Introduction to Modernization of Irrigation Schemes - Saiichi Oi
Need, Scope and Potential for Modernization of Irrigation Systems in Asia - V.V.N. Murty
Investments and Opportunities for Modernization Projects in Asia: Past and Future Needs - Herve Plusquellec
Institutional Change in Support of Modernization and Management Transfer - David J. Molden and Ian W. Makin
Concepts of Modernization - Hans W. Wolter and Charles M. Burt
Modern Water Control and Management Practices in Irrigation: Methodology and Criteria for Evaluating the Impact on Performance - Charles M. Burt
Modernization of Rice Irrigation Systems: Implications for Diversified Cropping - Sadiqul I. Bhuiyan
Change from Fixed Rotation to Continuous Flow - Dia El Din El Quosy
Technical Features and Implications of Modernization: The NEWMASIP Experience - A. Brolsma
Automatic Control and Measurement of Water Distribution - A. Yoshida
Saiichi Oi
Regional Water Development and Management Officer,
Regional Office for Asia and the Pacific, FAO,
Bangkok
INTRODUCTION
The population of Asia has almost doubled between 1960 and 1990 to over 2.9 thousand million people. This consists of nearly 55 percent of the world total. According to UN forecasts cited in several publications, the population of Asia will increase to 4.2 thousand million people by the year 2025. The International Food Policy Research Institute estimates that due to the increase in population and changing food demands the world food production has to be doubled by the year 2020.
Against this setting, the current trends in food production are of considerable concern. Cereals are the main staple food in Asia and food security depends largely on its production levels. In the decade of the 1980s average agricultural production of Asian countries increased by 50%. During the same period the population increased by 20% so the agriculture sector contributed in a substantial way to the welfare development in the region (Figures 1 and 2). Since 1990, cereal production growth rates have been declining. At present the annual growth rate of total cereal production is only 0.9% (FAO, 1995a).
Increased food production is possible by intensified use of inputs like improved seeds, fertilizers and control of insects and pests. The impact of all these inputs however depends heavily on how the basic resources, land and water, are used for agriculture. In Asia, very little land capable of sustainable agricultural production is still left unused. Furthermore, productive land is continuously being buried under the sprawl of urban and industrial development. About 43% of land in Asia is affected by some degree of degradation.
Scarcity of water will be another serious issue in future, particularly of clean water. The per caput availability of renewable freshwater (PCA) will decline by 50% in the next 25 years (Shahrizaila bin Abdullah, 1994). About nine Asian countries will have a low PCA. China and India are among the countries with the lowest PCA.
This implies that there is limited scope for water resources development. What is worse, investments in irrigation have decreased significantly in the 1990s from the level of the previous decade. Financial assistance of international donors tends to shift from irrigation development to other areas.
From these points of view, more attention has to be paid to existing land and water resources. The challenge is to use them in the best possible manner. To achieve this, irrigation will play the major role in increasing food production, but has to be improved to achieve this goal. In this paper possible improvements in irrigated agriculture through modernization of irrigation schemes are briefly outlined.
FIGURE 1. Agricultural production is outpacing population growth in several countries
FIGURE 2. Trend of cereal crop production in developing countries of Asia and the Pacific
IRRIGATION SYSTEMS IN ASIA
The role of irrigation in increasing agricultural production is well recognized. About 240 million hectares or 17% of the world's croplands are irrigated. This land produces one third of the world's food. At present, almost three-quarters of the world's irrigated area is in developing countries. Increased irrigated area and the technological innovations brought along with the Green Revolution enabled Asia to achieve food self-sufficiency.
Since the 1950s, the total irrigated area in the world expanded rapidly. Between 1961 and 1990, the area under irrigation increased by almost 100 million hectares. The annual growth rate of irrigated area exceeded 2% during the 1960s and 1970s. Today, the growth rate worldwide has slowed down to a moderate 0.8%. Between 1961 and 1990, the irrigated area in Asia expanded by 70 million hectares (FAO, 1992) (Figure 3).
All the countries of the region have irrigation systems varying in type and extent. The categorization of the irrigation projects varies from country to country. The projects are categorized as large, medium, or small scale depending upon the command area, the project costs, the storage capacity of reservoirs developed, or sometimes the irrigation water sources. While projects relating to surface water development are classified as large or medium, in general projects relating to groundwater or pumped irrigation tend to be classified as small-scale projects.
The performance of irrigation systems, however, has become subject of considerable criticism. The relatively larger systems have been subjected to more criticism, while the smaller ones appear to have performed better. Adverse performance parameters in the large irrigation systems include economic factors like inadequate returns from investments, low water-use efficiencies, social factors like failing to achieve equitable water distribution, and environmental factors like soil salinization, contamination of groundwater resources, and adverse public health effects.
LIMITS IN NEW IRRIGATION DEVELOPMENT
The rapid rate of expansion of new irrigated areas, which reached a peak in the 1970s, is steadily declining and is presently at 1.4% per year in Asia. Slowing down of the expansion is due to lack of new suitable land and water resources for irrigation development and due to increased costs for their development. Costs have increased substantially in recent years, mainly because more difficult areas have been developed, and full-scale irrigation development requires an integrated investment not only in irrigation infrastructures but in a range of related inputs. In addition to these difficulties, financial inputs by donors to irrigation development is shrinking for the reasons as mentioned above. Taking this into account, a study predicts that growth rate of irrigation will drop further to 1% in 2010 as the number of large-scale irrigation projects financed from public funds is decreasing.
CONSTRAINTS IN IRRIGATION
Many irrigated areas have a lower productivity than originally planned due to low cropping intensities and due to inefficient water use which reduces the originally designed command area. Furthermore part of the irrigated area goes out of production due to lack of maintenance or problems of waterlogging and salinity. It is estimated that at present 10 to 15% of the irrigated area, mainly in arid regions, is to some extent degraded due to waterlogging or salinization. The shortcoming in many irrigation systems requires additional investment in forms of costly rehabilitation and drainage projects, necessary to sustain productivity under irrigation.
The introduction of irrigation in particular to new areas may have other negative effects notably on the environment. These are often overlooked in the planning stage and include: large scale clearing of natural lands, pollution from high fertilizer and pesticide use, introduction and spread of water-borne diseases and environmental degradation of surrounding land due to increased population in the irrigated areas (fuel wood, overgrazing).
As the productivity of many irrigation schemes is disappointing, the financial viability of the irrigation infrastructure is threatening the sustainability of many schemes. Public schemes often rely on limited government funds for operation and maintenance, while revenues from taxing farmers for irrigation water prove very difficult to impose and to collect.
These problems and high costs in new irrigation development have led to a growing concern both from governments and financial institutes, and as a consequence there is a tendency to overscrutinize new investments in irrigation.
IRRIGATION PERFORMANCE OF EXISTING SYSTEMS
When the irrigation systems were planned and constructed, the main goal was to deliver water at the farm level. Many of the problems that later arose were not fully visualized nor appreciated. The main causes for the disappointing performance of the irrigation systems in the Asian region could be listed as follows:
In some large irrigation systems, the available irrigation potential is not being used for reasons like farmers attitudes, lack of on-farm development etc. Most of the irrigation systems were constructed by agencies which also continued to manage the systems. The engineers who were responsible for construction did not have the aptitude or in some cases the technical knowledge required for the management of the system. The irrigation system management in some cases could not come close to the farmers and be responsive to their needs. Required drainage facilities could not be established and also adequate budgetary provisions were not available for the maintenance of the system.
Irrigation systems operated under these constraints, developed, over time, several adverse conditions effecting the whole system operation. Some of these can be listed as follows:
In addition to these structural factors, inequitable and untimely water deliveries affected the overall productivity of the systems.
If problems with irrigation systems only remained within degradation, it would be sufficient to rehabilitate them for restoration to their original design. However, these rehabilitation could not be enough, if we want;
Unfortunately, most of the schemes designed and implemented in the past are unsuitable to meet these requirements without being modernized.
An important factor to make an irrigation system more effective is to reduce water losses. This, however, is often difficult to achieve as most irrigation schemes have open canal systems for conveyance of water.
While open canal systems have a good conveyance capacity in relation to the construction cost, compared with pipe line systems, they have little flexibility to change its flow. If discharge to a branch is changed, either increased or decreased, all the gates relating to the watercourse have to be adjusted to the changed discharge. The gates to be adjusted include gates of the turnouts and others located both downstream and upstream as well as at the main intake. To give an example, if outlets to secondary canals are either opened or closed downstream, the gate at the main intake has to be regulated to balance discharges between inlet and outlet. If it is not regulated properly, too much of water results in losses and too small quantity in shortage.
The characteristic of open canal flow is essentially opposite to that of pipe line systems, where total discharge flowing out from all the taps of the system logically equals to the inflow at the top of the same system with no delivery losses except for leaks. On the contrary, to minimize losses, an open canal system needs to adjust discharges to what is actually required. Adjustment is needed not only for withdrawal at the intake but also everywhere in the system. This physical feature of an open canal system makes water losses inevitable. To reduce water losses, a more intensive control of water flow will be imperative.
REASONS FOR MODERNIZATION OF IRRIGATION SCHEMES
The traditional agricultural systems based on the cultivation of rice, mainly for home consumption, have to be transformed into a more diversified system with higher agricultural inputs and to be market oriented. To feed growing population and support farmers' welfare and rural development, these objectives should be more encouraged and supported.
Considering the constraints regarding availability of cultivable lands, there is no other way than to make water use more efficient in already irrigated areas, shifting its pattern from seasonal to year-round supply.
It is not only irrigation that needs more water. Due to the rapid urbanization and industrialization, competition of water use between irrigation and other water users will become a focal point because they have to share limited water resources.
One major task of the irrigation sector will therefore be to reduce water losses and to achieve equitable water delivery. Modernization of irrigation schemes will therefore be an essential part of the solution. Modernization aims at improving a system, so that farmers are able to control water at minimized losses. However, modernization is not only a physical improvement of the system but also includes institutional reforms to sustain their performance.
It has meanwhile been recognized that human capacity building is a key prerequisite for better operation and maintenance. As far as controlling water in open canal systems is concerned, this is not always the case. When water scarcity occurs, intensive management takes place. Good operation usually requires a lot of labour. The poorer the irrigation system is functioning, the more labour will be required. However, when enough water is available, farmers don't care much of controlling water and withdraw their labour input from operation. That is because they have no direct benefit from saving water. In other words, the farmer who can take enough water has no real incentive to save it. Therefore, physical improvement of the system through modernization has to go along with transferring management responsibilities to the farmers in order to may change this attitude.
Nevertheless, many countries, except Japan and Korea, are still reluctant to modernize old systems saying that it is very costly and that expansion of irrigation is more important than modernization. However, water availability is getting tighter in many basins. Competition with water users is mounting, which might threaten water use for irrigation. Therefore, effective water use achieved by modernization has the same effect as the development of new water resources. If comparing the costs for new water resources development such as the construction of dams and reservoirs, modernization will often be more favourable.
As already mentioned before, modernization has to go along with institutional reforms. For raising funds, integrated development with municipal water suppliers is recommendable. Water Users Associations should be strengthened so that they will be accountable for management of the irrigation system. Modernization will make it possible to introduce adequate water fees for not only O&M but also for some parts of capital cost recovery because modernization of irrigation systems results in remarkable returns to farmers including equitable and rational water delivery, water security and labour saving for operation.
IMPLEMENTATION OF MODERNIZATION
In some irrigation systems, projects have been initiated for rehabilitation and improvement. The efforts in these projects are directed towards correcting errors in the original planning process and responding to new requirements. Most projects have experienced the problems encountered in new irrigation projects and have also posed new constraints and challenges to the project designers and implementors.
Based on the lessons learnt from past experiences, the following guidelines and recommendations regarding modernization are proposed:
1. In view of the dynamic nature of the irrigation system and its environment, the systems generally should not be restored to its original design specifications.SELECTION OF SYSTEMS FOR MODERNIZATION2. The current construction orientation of most agencies should be replaced by an approach that improves management as well as infrastructure.
3. The projects should be flexible, allowing adjustments during project implementation to correct errors in planning and to respond to new information.
4. Greater emphasis should be placed on project design. Planning for design should involve consultation with relevant national and local officials, with operation and maintenance personnel and in particular with farmers.
5. Diagnostic analysis of the irrigation system should be conducted to provide input into the planning process.
6. Roles, responsibilities, sharing of funds, and training opportunities should be clearly defined for all participating agencies before a project begins. The role that each agency plays should be complemented by specific incentives.
7. New policies should be formulated and communicated to water users and others involved in the process prior to project implementation and not during or after.
8. The monitoring and evaluation unit should be linked with the project management office to effectively make revisions during project implementation.
9. A coordinating and feedback mechanism should be developed among the various parties involved for continuous learning from the rehabilitation and betterment effort.
All the countries in the Asia-Pacific region have a large number of irrigation systems in operation. A careful review of the irrigation systems needs to be taken up before selecting a system for modernization. The procedures discussed for performance evaluation in earlier FAO consultations will provide some feedback for the selection of the systems. Only systems which will respond to modernization should be selected.
In a given irrigation system considered for modernization, a combination of the activities listed earlier need to be selected. The activities to be selected will depend on factors like possible system response, acceptability by the beneficiaries and technical competence available. The activities selected will no doubt be location specific.
BIBLIOGRAPHY
Shahrizaila bin Abdullah. 1994. Water for the Future. Paper presented on FAO Symposium for World Food Day. Bangkok, October 1994.
FAO. 1992. Production Yearbook 1992. Rome, Italy.
FAO. 1994. Irrigation Challenges in Asia.
FAO. 1995a. Report on Seventh Session of the FAO Regional Commission on Food Security for Asia and the Pacific. Bangkok, Thailand, 4-5 July 1995.
FAO. 1995b. Towards a Policy for Water Resources Development and Management in the Asia Pacific Region, Issues and Opportunities: Asian Development Bank.
FAO. 1995c. Irrigation management transfer in Asia: RAP Publication 31. FAO, Bangkok.
World Bank. 1993. Water Resources Management in Asia. Volume I: Main Report. World Bank, Washington D.C.
V.V.N. Murty
Professor, School of Civil Engineering, Asian Institute of
Technology, Bangkok
INTRODUCTION
It is generally known that a major part of the irrigated areas of the world are at present located in the Asian Region. In the last two to three decades, the irrigation systems in this Region have contributed significantly to increased food production making several countries self-sufficient in food grains and also in some cases resulting in exports. Irrigation systems also helped in the expansion of certain agro-based industries like sugar and starch by bringing more areas under supporting crops and also the production of some commercial crops.
At present there is not much scope to increase the irrigated areas due to limitations on land, water and capital resources. In addition at some locations there are demands on irrigation water for urban and industrial purposes. It is therefore important that the present irrigation systems are modernized and managed in the best possible manner.
In respect of the irrigation systems in the Asian region, it is recognized that improvements are needed in the operation and management of these systems to achieve higher benefits. Even though there are no specific evaluation reports of all the systems in the Region, studies by organizations like the International Irrigation Management Institute (IIMI, 1993) indicate the need for improving the performance of many of the irrigation systems. Efforts are, however, being made by all countries in the Region to improve the performance of the irrigation systems.
The concepts of modernization aims at carrying out improvements in the system to achieve enhanced objectives like increased crop productivity, reduction in labour required for operation, improved water use efficiency, environmental conservation, etc. The measures which could help modernization may consist of several items involving operational and constructional aspects and could vary from system to system.
The FAO Regional Office for Asia and the Pacific has for a long time been making efforts towards improving irrigation systems management in the Region. A regional workshop on improved irrigation system performance for sustainable agriculture was conducted in 1990. An expert consultation on irrigation/water management for sustainable agricultural development was conducted in 1992. In 1994, another expert consultation on irrigation performance and evaluation for sustainable agricultural development was conducted.
In this paper several steps which contribute to modernization of irrigation systems are outlined. Some available examples, wherein these steps are being implemented are also given. In the Asia Pacific region, irrigation systems are broadly classified as small, medium or large depending on the source of water, investments made and the area irrigated. The measures outlined are applicable to all the systems.
USE OF MODELS FOR ESTIMATING CROP WATER REQUIREMENTS
One of the important aspects in irrigation systems management is the estimation of the water requirements of the different crops grown in the system and adjusting the water deliveries to meet the crop water requirements. It is now recognized that crop water requirements can be reasonably be estimated using climatological approaches. Smith (FAO, 1992) prepared detailed software for estimating crop water requirements under different conditions. As lysimeters cannot be established at all locations, the use of this software is suggested for understanding the crop water requirements in irrigation systems.
Simultaneous with the use of software for estimating crop water requirements, the agro-meteorological observatories need to be improved. Equipment installed should be functional and regular observations need to be recorded. At present integrated units for agrometeorological observations equipped with microprocessors for data recording and also with radio transmission are available. Data recorded could be used for real time operation of irrigation systems.
In a given irrigation system, knowing the crop water requirements, rainfall and all losses a water balance equation can be developed as follows
IR + RF = Etc + DR + DP + CLwhere IR is the irrigation supplies, RF is rainfall, Etc is crop evapotranspiration, DR is surface drainage, DP is deep percolation and CL is conveyance losses. This equation could be used for each season and also for a given area. This analysis provides a broad understanding of the system and a basis for performance evaluation and improvements.
MANAGING WATER DELIVERY SYSTEMS
In a large irrigation system, water is released from a reservoir and diverted through a diversion structure into the canal system. The canal system consists of main and secondary canals or distributaries and finally water is delivered to the tertiary units. The irrigation system management usually has responsibility up to the tertiary units beyond which the farmers manage the water.
Depending on the topographical situation and the extent of the command area, the canal system has several structures in it. These structures consists of both for conveyance as well as water control structures. The water control in irrigation canals is broadly classified as (i) upstream control, (ii) downstream control and (iii) mixed control. In almost all the irrigation systems in Asia, the upstream control is adopted in the irrigation canals. From the canal system, water is delivered to the tertiary units and the delivery patterns are defined by the frequency, rate and duration. These could be in any one of the forms as shown in Fig. 1. Timeliness is another factor that needs to be taken into consideration. Ankum (1991) outlined the flow control procedures and structures in canal irrigation systems.
FIGURE 1. Possible water delivery patterns to the tertiary unit
Plusquellec et al. (1994) critically examined the problems involved with water delivery systems in canal irrigation. Main points mentioned are:
In a study conducted in Pakistan on two canal systems which have been in operation for fairly long time, Kuper and Kijne (1993) concluded poor performance of the systems as indicated in Table 1.
In another study Bashir Ahmad et al. (1993) found that along a distributory there is considerable variation in the discharge of outlets as shown in Table 2.
TABLE 1
Performance indicators for Fordwah and Gugera canal systems
during kharif
|
Indicators |
Fordwah Branch |
Rating |
Gugera Branch |
Rating |
|
Adequacy (Pa) |
0.67 |
Poor |
0.81 |
Fair |
|
Delivery Performance Ratio (P’a) |
0.76 |
Poor |
|
|
|
Dependability (Pd) |
0.47 |
Poor |
|
|
|
Temporal CV (P’d) |
0.41 |
Poor |
0.24 |
Poor |
|
Equity (Pe) |
0.63 |
Poor |
|
|
|
Spatial CV (P’e) |
0.56 |
Poor |
0.38 |
Poor |
|
Position
|
Type
|
Number
|
Average Discharge |
Performance |
|
|
Design |
Measured |
Coefficient |
|||
|
Head
|
|
|
|
|
|
|
APM |
20 |
0.9 |
1.08 |
121 |
|
|
OCAPM |
3 |
1.65 |
1.66 |
101 |
|
|
Open Flume |
5 |
0.87 |
1.04 |
119 |
|
|
OFRB |
3 |
2.12 |
2.18 |
103 |
|
|
Pipe |
7 |
0.94 |
1.22 |
130 |
|
|
Middle
|
|
|
|
|
|
|
APM |
12 |
0.91 |
1.01 |
111 |
|
|
OAPM |
4 |
1.83 |
1.74 |
95 |
|
|
Open Flume |
13 |
1.14 |
1.13 |
99 |
|
|
Pipe |
4 |
1.43 |
1.17 |
82 |
|
|
Tail
|
|
|
|
|
|
|
APM |
3 |
0.93 |
0.78 |
83 |
|
|
Open Flume |
23 |
1.31 |
1 |
76 |
|
|
Pipe |
4 |
0.9 |
0.64 |
72 |
|
|
Overall
|
|
|
|
|
|
|
APM |
35 |
0.9 |
1.03 |
114 |
|
|
OCAPM |
7 |
1.75 |
1.71 |
98 |
|
|
Open Flume |
41 |
1.21 |
1.04 |
87 |
|
|
OFRB |
3 |
2.12 |
2.18 |
103 |
|
|
Pipe |
15 |
1.06 |
1.06 |
100 |
|
In a study in the Sungai Muda Irrigation Scheme in Malaysia, Lankford and Gowing (1996) observed that most of the gates provided in the system were either oversized or undersized. The tendency is to open the gates fully during their operation. Gates which were oversized delivered more water than required resulting in wastage of water. Gates which were undersized could not deliver the water as per crop water requirements.
In a study conducted on a tertiary unit in the Meklong irrigation system (Thailand), Kemachandra and Murty (1992), observed that the tertiary canal capacities are not sufficient to deliver the water to the fields as per peak crop water requirements.
In respect of water delivery systems, the following points need to be attended to in any irrigation system.
1. The hydraulics of the canal system need to be analysed. This should include the hydraulics of all the structures along the canal including discharge characteristics, travel times etc.
2. Maintenance of the canal linings and silt removal will help in improving the conveyance efficiency and also equitable distribution of water to the secondary and tertiary canals.
USE OF WATER ALLOCATION MODELS
At present, several computer based water allocation models which are useful in irrigation system management are available. These models are developed for main system level operation including canal network and reservoirs, estimating water demand at tertiary unit level and as management information systems.
Main system level models are useful in day-to-day operation of the irrigation network including scheduling of irrigation deliveries, management of reservoir operation, setting of hydraulic structures and providing feedback information. Tertiary level models estimate the water demand of the tertiary system based on water balance calculations and these estimates are used by the main system level models to route channel flows. Management information systems can provide information to support other project activities such as the control of operation and maintenance activities, expenditures, water fees, crop production etc.
In Thailand, application of computer models for irrigation systems management is in the initial stages. All the large irrigation systems in Thailand are upstream controlled wherein decisions relating to water deliveries are made from a location near the headworks. In the Mae-Klong irrigation project in Thailand, a computer-based water allocation model WASAM (Water Allocation Scheduling and Monitoring) is in use. This model essentially considers the depth of water in lowland paddy fields as the criterion for allocating the water to different tertiary units. Expected rainfall is estimated using the Weibull plotting position (Ilaco/Empire M&T, 1988).
In addition to WASAM, in Thailand a software developed by HR Wallingford (UK) entitled INCA (Irrigation Network Control and Analysis) is in use in Kraseio Irrigation Project (Chaiyong, 1996).
In India, in the Bhadra reservoir project efforts are being made to implement a water delivery model (Mehta, 1994). In the Republic of Korea significant advances have been made in the use of computers in irrigation systems management (Chung and Lee, 1992).
The use of computer models for water allocation is in the preliminary stages. Most of the time, these models are used as ‘black box’ with the result that full use of the models are not made. More trained personnel is needed in this direction.
Recently, the use of geographical information systems (GIS) in irrigation systems management is being advocated (Iyangararasan and Murty, 1993). GIS can serve as a good management information system and can be useful in day to day management as well as providing feedback through performance evaluation.
IMPROVEMENTS IN IRRIGATION STRUCTURES
Structures in the irrigation system consists of: (i) structures in the main and secondary canals (ii) outlets at the tertiary units, and (iii) farm irrigation structures in the tertiary units. Structures in the main canals help in controlling water flows and structures at the tertiary outlet and at the farm level help in proper distribution of water.
In general, the structures in the main canals are well maintained, while structures at the tertiary unit level need improvements. In the Indus Irrigation systems in India and Pakistan, several types of outlets are used at the tertiary unit levels. In Thailand, the Constant Head Orifice (CHO) outlet has been installed in some irrigation systems (Krasieo, Petchburi and Meklong). The CHO outlet even though based on sound hydraulic principles has not been very successful because of its somewhat complicated operational procedure. The simple gate outlet has been found to be operating satisfactorily.
In terms of farm irrigation structures, there is no uniformity in the structures adopted. A wide variety of designs could be found in the irrigation systems. The prefabricated structures used in Pakistan have been found to be fairly successful. In the case of farm irrigation structures, it is desirable to develop prefabricated structures as these will be easy to manufacture and install at the field level.
IMPROVEMENTS IN FARM IRRIGATION SYSTEMS AND FIELD LAYOUTS
The fields receiving irrigation need to be properly levelled and the stream size should match the crop, soil and length of run. There has been no systematic attempt to improve the farm irrigation systems. However, India, Pakistan have embarked on large scale land levelling operations. In the case of paddy field layouts, Thailand has carried out significant improvements to paddy field layouts. Paddy fields were developed in three categories depending on the possibilities in a given situation. These were termed as ditch and dike system, extensive development and intensive development. In the ditch and dike system improvements in irrigation and drainage channels were carried out with the existing field layout. In the extensive layout, in addition to these improvements, minor improvements like straightening field embankments, roads etc. are included. In the intensive layout, all these improvements are done in addition to land consolidation.
Japan and the Republic of Korea have developed the paddy fields in an ideal manner. In many of the countries in the Asia-Pacific Region, due to land fragmentation, development of an ideal layout is difficult. But within the existing situation, land improvements in the irrigation systems need to be carried out.
Sprinkler and drip irrigation systems are getting popular in the Region as their costs of installation are coming within affordable ranges. Drip systems are becoming popular for horticultural crops. In India, sprinkler systems are being used on a limited scale in the canal irrigated areas for irrigating highly sandy areas and areas which cannot be reached by surface flows. The possibilities of integrating these two methods in a large surface irrigation system need to be examined in all large irrigation systems.
CROP DIVERSIFICATION
Crop diversification is being advocated in the large irrigation systems, especially with the rice-based cropping systems (Miranda and Maglinao, 1993). The purpose is to make better utilization of the available water supplies and at the same time improve the farmers income. In an extensive study in Bangladesh, Biswas and Mandal (1993) concluded that “Crop diversification does not appear to be strongly associated with social variables such as family size, level of education, farm size and population density, but it seems to have a strong relationship with access to credit, inputs and support services”. Infrastructural and institutional development in terms of communications and marketing are also required. The technology for utilizing rice fields for other cropping systems appear to be equally important. It is seen that crop diversification is possible and accelerated when the farmers are able to get some economic benefits. For example in the Meklong and Kraseio irrigation systems (in Thailand) which were originally designed for rice, with the establishment of sugar mills in the area, sugar cane became an important crop. Crop diversification is possible if an agro-industrial base could be established for the crops grown in the area. Large irrigation systems need to examine such possibilities.
CONJUNCTIVE USE OF SURFACE WATER AND GROUNDWATER
In surface irrigation systems over a period of time the water tables are likely to rise, even up to the ground level creating waterlogging conditions. In large surface irrigation systems, it is desirable to use the groundwater along with the surface water. For the farmers groundwater is relatively expensive compared to surface water. However, some mechanism should be developed so that the available groundwater resources are used along with the surface water.
Conjunctive use of surface water and groundwater has been successful in Bhakra irrigation system (part of the Indus basin) in India. Here the surface irrigation system did not cover the full water requirements and farmers installed a large number of shallow tubewells for groundwater extraction. In the Phitsonulok irrigation system in Thailand, farmers are using shallow tubewells to supplement the available irrigation supplies. The impact of these shallow wells in the overall groundwater resources has not yet been assessed.
DIVERSIFIED USE OF IRRIGATION SYSTEMS
Irrigation systems sometime form part of multipurpose projects involving hydroelectric power generation, flood control and navigation. Even though the irrigation systems are designed for the purpose of delivering water for crop production, recently other uses of irrigation systems are being adopted.
One such use is the provision of drinking water in the rural areas. Such cases are reported from India and Thailand. As the irrigation systems traverse large areas and as the conveyance system is already in place, the irrigation system could be used for providing water for municipal needs. The main concern will be the water quality drawn from the irrigation system which will need further treatment so that the water becomes suitable for municipal use. Drawing water from an existing irrigation system could to some extent affect the irrigation supplies. Improvements in the operation of the irrigation system becomes necessary.
DRAINAGE
The need for drainage in large irrigation systems is now generally accepted and provision for drainage is being made. The drainage measures consists of open drains to drain the surface flows during the monsoon period. In some of the irrigation systems (the Indus system in Pakistan and India), the rising water tables and salt problems indicate the need for subsurface drainage. Efforts are now being made in Pakistan and India for installation of subsurface drains. In Japan, subsurface drainage systems have been used in paddy fields. In the countries in the Asia Pacific Region, subsurface drainage systems have not so far been adopted on a large scale.
The maintenance of open drains continues to be a problem in irrigation systems. Innovative approaches for using the water in the drains are needed.
ENVIRONMENTAL HAZARDS
Irrigation systems convey large amounts of water to areas which might have been under rainfed agriculture. As a result of irrigation, the soil moisture levels remain high and as a consequence new vegetation in the area gets established. Even though irrigation systems in general are beneficial, they are also responsible for certain environmental hazards. These could be broadly listed as follows:
1. waterlogging, formation of stagnant water pools and vector breeding places resulting in health hazards;Two groups of water-related diseases, the water-based and water-related vector-borne diseases, are most likely to be found in areas where irrigation has introduced large new water surfaces, like lowland paddy. The diseases include malaria, schistosomiasis, lymphatic filariasis, onchocerciasis (river blindness), Japanese encephalitis, and some other viral diseases transmitted by insects. The settlements of new residents may bring in people without immunity, or they may bring new sources of infection or in more dense settlements disease transmission may be facilitated. Oomen et al. (1990) examined the irrigation-health problems and offered detailed suggestions.2. soil degradation, development of salinity and alkalinity resulting in reduction in crop production, uptake of undesirable elements by plants causing long-term health problems;
3. irrigation return flows causing surface water and groundwater contamination and also resulting problems for aquatic habitat;
4. drainage channels with aquatic weeds and stagnant water pools;
5. spread of water-borne diseases.
The irrigation system management should be aware of these and any other possible hazards in the system. In the monitoring programme of the system, the likely hazards should be included. In order to mitigate several of the hazards listed, cooperation and assistance from other agencies might be required. The irrigation system management may not be able to implement the preventive measures but should act as a catalyst in getting them carried out.
COMMUNICATION FACILITIES
Irrigation systems should be provided with satisfactory communication facilities. A network of roads help the farmers to move the agricultural produce to marketing or storage facilities. If the central office responsible for water deliveries is situated far away from the delivery points, suitable communication facilities are needed for the field staff to keep in contact with the central office.
OTHER ISSUES
In addition to the items discussed earlier, improvements in irrigation systems management are possible by organizing water users associations, providing extension services, organizing short courses for the farmers and also the personnel involved in the project administration.
In many of the irrigation systems, the construction engineers later became the persons responsible for managing the systems. Professional career paths were not as attractive in management as in the construction sector. To some extent these aspects did not contribute to develop persons who have an aptitude for managing large irrigation systems. A management focus is required for modernization of irrigation systems.
CONCLUSIONS
1. A clear understanding of the crop water requirements in the irrigation systems is necessary. Available climatological methods for estimating crop water requirements may be used along with upgrading of the agro-meteorological observatories. A water balance of the entire system based on seasons and subareas needs to be developed.
2. Operation of the water delivery systems consisting of main and secondary canals along with the structures is a crucial factor in irrigation systems management. The hydraulics of the system need to be fully understood and suitable operational policies are to be evolved. Maintenance of the system by structural maintenance and desilting are also important.
3. Computer based water allocation models could be useful in irrigation systems management. However, an understanding and adoption of these models to a particular system are required.
4. Improvements in the farm irrigation structures will enhance conveyance and application efficiencies at the tertiary unit level. Prefabricated structures can conveniently be used for this purpose, as they provide easy installation and maintenance.
5. Improvements in farm irrigation systems consists of land levelling, improvements in field layout and adoption of sprinkler and drip systems. These need to be implemented at possible locations.
6. In rice based irrigation systems crop diversification could be encouraged. Crop diversification is accelerated when farmers have economic benefit, possible through agro-industrial support.
7. In irrigation systems, conjunctive use of surface and groundwater should be attempted. Such a practice to some extent control the rise of water tables and also meet the crop water requirements.
8. Diversified use of irrigation systems need to be considered. Water supplies to municipal and industrial purposes can be accepted as they will be financially beneficial. However originally targeted irrigated areas should not suffer as a result of the diversified uses.
9. Drainage continues to be an important requirement in all irrigation systems. High water table and salt problems can effectively be handled using subsurface drainage methods. Provision of drainage and maintenance of the drainage channels need to be attended to in all irrigation systems.
10. Environmental hazards in irrigation systems consist of soil degradation, water quality and health issues. The environmental hazards in an irrigation system need to be identified for initiating remedial measures.
11. Irrigation systems should develop infrastructural facilities like communications, roads, market facilities for agricultural produce etc.
12. Development of human resources for irrigation systems management need to be continued. This should include establishment of career paths and interdisciplinary approaches.
REFERENCES
Ankum, P. 1991. Flow Control in Irrigation Systems. International Institute for Hydraulic and Environmental Engineering, Delft, The Netherlands.
Bashir Ahmad, Ch., Ali, M.A. and Khan, A.R.A. 1993. Pattern of Flow Variations in Distributories and Reachwise Supply to Outlets. Proceedings, Irrigation Systems Management Symposium, Lahore, Pakistan.
Biswas, M.R. and Mandal M.A.S. (eds.). 1993. Irrigation Management for Crop Diversification in Bangladesh. University Press, Dhaka.
Chaiyong, P. 1996. Case Study of Planning/Monitoring of Irrigation Water Management for Krasieo Irrigation Project. M. Engg. Thesis, Asian Institute of Technology, Bangkok.
Chung, H.W. and Lee, N.H.1992. Computerized water management systems for paddy fields. In: Soil and Water Engineering for Paddy Field Management. Asian Institute of Technology, Bangkok.
FAO. 1992. CROPWAT: a computer program for irrigation planning and management. M. Smith. Irrigation and Drainage Paper 46. FAO, Rome.
Ilaco/Empire M&T. 1988. Mae Klong Irrigation Project, Stage II Right Bank. Royal Irrigation Department, Thailand.
International Irrigation Management Institute (IIMI). 1993. Advancements in IIMI’S Research, 1992. Colombo, Sri Lanka.
Iyngararasan, M. and Murty, V.V.N. 1993. Assessing Environmental Impacts in Large Irrigation Systems using GIS. Proceedings, International Conference on Environmentally Sound Water Resources Utilization, Asian Institute of Technology, Bangkok.
Kemachandra, R.A.D. and Murty, V.V.N. 1992. Modeling irrigation deliveries for tertiary units in large irrigation systems. Agricultural Water Management 21: 197-214.
Kuper, M. And Kijne, J.W. 1993. Irrigation management in the Fordwah Branch Command Area, Southeast Punjab, Pakistan. In: Advancements in IIMI’S Research, 1992. International Irrigation Management Institute, Colombo, Sri Lanka.
Lankford, B. and Gowing, J. 1996. The impact of design approximations on the operational performance of an irrigation scheme: a case study in Malaysia. Irrigation and Drainage Systems 10(3): 193-205.
Mehta, N.K. 1994. Irrigation water management for Bhadra Reservoir Project, Karnataka, India. In: Irrigation Water Delivery Models. Water Report 2. FAO, Rome. Pp. 33-48.
Miranda, S.M. and Maglinao, R. (eds.). 1993. Irrigation Management for Rice-Based Farming systems in Bangladesh, Indonesia and the Philippines. International Irrigation Management Institute. Colombo, Sri Lanka.
Oomen, J.M.V., de Wolf, J. and Jobin, W.R. 1990. Health and Irrigation. Vols. 1 and 2. International Institute for Land Reclamation and Improvement, Wageningen, The Netherlands.
Plusquellec, H., Burt, C. and Wolter, H.W. 1994. Modern Water Control in Irrigation, Concepts, Issues and Applications. The World Bank, Washington, D.C.
Herve Plusquellec
Senior Advisor, Water Policy Division, Agriculture Dept.,
World Bank, Washington D.C., USA
INTRODUCTION
FAO called a regional expert consultation to explore the need and opportunities for introducing modernization in a sustainable way in Asia’s irrigated agriculture. The objectives of this consultation are:
This paper will deal mainly with the second objective of this consultation by providing an overview of the techniques and impact achieved by modernization projects in the Asia region and discussing the opportunities for modernization of irrigated agriculture in Asia.
The information note for the consultation provides the framework for the justification of irrigation modernization:
Increasing competition with the urban and industrial sectors limits the quantities of water available for further irrigation expansion. Furthermore, the availability of land and water resources which could be developed economically is limited worldwide and even more in the Asian context.To meet the challenges of the future, the main remaining option is to increase the amount of food that can be produced per unit of water. Many changes in the physical system and the management system have to be made to meet that challenge:
This paper will first suggest a broad typology of gravity irrigation schemes in the Asia region based on management and associated technologies and examine the reasons for the slow adoption of modern irrigation in most parts of the world. The paper will then present some past and recent modernization experiences in Asian countries, including Western Asia (Middle East). Finally, the paper will examine the constraints to modernization of existing schemes.
TYPOLOGY OF IRRIGATION SCHEMES IN ASIA
First, it is important to note a major difference in irrigation water distribution between most, if not all, countries from the region and other parts of the world. In most irrigation projects from Latin America and North Africa, water is generally distributed on a pre-arranged demand. Individual or group of farmers place their water demand a few days in advance. The rate, frequency and duration are arranged between the user and the irrigation agency or the user organization. By contrast, most irrigation systems in the Asia region are operated under centralized scheduling. The idea is to determine irrigation water delivery for the farmers on a project wide basis. Rigid rotational schedulings are applied in some countries, such as in the four provinces of Pakistan and in the Western States of India. Some flexibility to attempt to match supply and crop requirements was introduced in the delivery schedulings of irrigation schemes in East Asia countries: Thailand, Philippines, Indonesia, Burma and in the Southern states of India. To achieve flexibility in water distribution, these schemes were equipped with fully gated structures at each bifurcation point.
The so-called “melon-on-the-vine” design concept of irrigation projects in South China is a special case. To provide flexibility in water use, the main reservoirs are connected to a number of medium-size reservoirs themselves connected to thousand of farm ponds. The same concept was also used in Sri Lanka and Tamil Nadu State, India (it is also used in Coachella project, California to make pressurized irrigation applications possible at farm level, in a system designed for gravity irrigation).
REASONS FOR SLOW ADOPTION OF MODERNIZATION
Worldwide
Despite the poor performance of irrigated agriculture in many countries the fact is that the adaptation and transfer process of modern technology in irrigation has been slow. Not long ago, it was mistakenly thought that “Modernization is not for developing countries”. This statement, heard even during international events in the past, reflect a profound misunderstanding of modernization and of the deficiencies of existing systems. Another frequently argument is that modern technologies and design concepts are too costly. Adverse administrative and behavioural reasons for slow adoption of modernization include:
The fundamental cause for the slow rate of technology transfer, however, has been a lack of knowledge of available technologies and a misunderstanding of the nature of irrigation in particular:
Asia Region
Adoption of modernization techniques has been particularly slow in the Asia region. In addition to the worldwide reasons discussed above, there was a perception that water resources were abundant in most countries from the region. As a result, little attention was paid on conserving water. As an example, rice was produced in the Chao Phraya delta in Thailand only during the wet season until early 1960s. The second rice crop peaked up during the late 1970s to a maximum of 400,000 hectares which contributed to the severe competition between water uses for irrigation, salinity and pollution control in the Lower delta and municipal and industrial supply of the Greater Bangkok Metropolitan area. Modern management techniques of the entire Chao Phraya basin were progressively introduced.
Although the argument of abundant water resources was not valid for a large part of South Asian countries, the concepts of modern irrigation were introduced in that region much later than in other parts of the world. Some of the arguments heard from the opponents of modernization are discussed in detail.
Some experts believe that there is no need for flexible water delivery. They argue that farmers can easily adjust their cropping pattern and farming practices to predetermined irrigation schedules as long as they are reliable. In their views, the additional benefits are not sufficient to balance operational complications and higher investment costs. The argument is valid for flat areas with homogeneous soils and uniform cropping pattern. The explosion of groundwater use in Pakistan and Northern India during the last three decades show how much farmers are willing to obtain not only additional water but also flexibility in water application. The design logic of extensive irrigation, water spreading and central administration, developed by the local powers in India and Pakistan, has served the countries well as long as rules were enforced and overall demand for food was smaller. It has now been well documented that in some regions water supplies are inequitable, the rules are no longer enforced and crop yields are still stagnating at low levels.
Other experts advocate that lack of management skills is the most constraining factor to modernization of irrigation schemes in developing countries. They argue that performance is very poor in most projects designed for flexible scheduling to match water delivery to farmers’ needs. The author agrees with this diagnosis and the suggestion that the technology must be simplified. However, the solution to simplify operational procedures is not limited to eliminating flexibility in water distribution through fixed flow-sharing structures (or the so-called structured design in which systems are managed to a certain level, below which the canals run in an on-off mode and water is distributed through fixed outlets and proportional dividers). If assisted by suitable technology, operators are able to manage gated irrigation systems. With good design, operation can become easier and more reliable.
As discussed by other participants, the case for modernization is now compelling. Low project efficiencies, dismal performance, negative environmental consequences, and inequitable and unreliable water deliveries are now well documented. New designs concepts, design tools, equipment and communication systems exist. Progress requires that designers and planners become familiar with such tools and concepts and apply them.
Modern design of an irrigation system must not be confused with new physical components. The design process should start with the definition of performance objectives and the definition of an operational plan. Unfortunately, a frequent error in the past was to prepare an operational manual as an afterthought, once construction was completed. This reverse process in the design of irrigation schemes has been one of the major causes of the poor performance of irrigated agriculture.
PAST EXPERIENCE WITH MODERNIZATION IN THE ASIA REGION: AN OVERVIEW
If modern design is defined as the result of a thought process that selects the configuration and the physical components in light of a well-defined and realistic operational plan based on the service concept, several systems in the region meet that definition. In that case, the traditional irrigation systems designed and built by farmers (Nepal, Bali) and based on the flow sharing concept through the use of simple flow divisors are the first modern systems in Asia. Even the rigid scheduling, ungated system of Pakistan and Northwest India were modern when introduced by the colonial power. The objective of equity of distribution to serve the maximum area possible was matched by an infrastructure requiring minimum human interference in operation.
Serious operational problems arose when it was attempted to make irrigation schemes more responsive to farmers’ needs through the design of fully gated systems. Two of the most common design errors during the expansion period of irrigation in the region after the mid-1940s have been the poor understanding of unsteady flows and the use of manually operated gates which require frequent adjustments.
A first step in the professional evolution of irrigation engineers is to increase their understanding of the interactions between hydraulic structures and of the dynamics of unsteady flows. They should also have better understanding of the reality of the field, including the working conditions of the operating staff and of the limitations of transportation and communications facilities.
To resolve the difficulties of operating large irrigation schemes, technologies and control equipment used for quite sometimes in more advanced countries were introduced in the region since the late 1960s. However, these innovations were used on a pilot basis and so far none of the countries in the region has approved new national design standards reflecting modern concepts of design and operation of canal system. It is also important to note that most of these innovative designs were used for new projects. Existing projects have benefited from modern management tools and less from modernization of the physical infrastructure.
APPLICATION OF MODERN DESIGN TO NEW DEVELOPMENT PROJECTS
Examples of new schemes where modern design concepts are found in Malaysia, Indonesia and India, as well as in Western Asia countries: Iraq, Syria and Iran. Two projects in Malaysia, Muda on the west coast and Kemubu on the east coast have been under operation for about 25 years. The Sidorejo project in Indonesia, a sub-project of the Kedung-Ombo scheme, was completed three years ago and the Majalgaon project in India has just been inaugurated in October 1996. Experience from these modern projects in the region is, therefore, rather limited. Projects in Western Asia have been under operation for quite some time. However there is no information available on their performance with the exception of the Guilan project on the Caspian sea in Iran. Construction of a new modern project, the High Level Pehur Canal diverting water directly from Tarbela reservoir in the Northwest province of Pakistan is going to start early 1997. Detailed descriptions of these schemes are provided in Appendix 1.
The common objective of the above schemes is to provide a better matching of water supply and demand, to simplify the operation of the canal systems through the use of less sensitive structures or combination of, and the use of automatic water control. The main canals of the two projects in Malaysia, the projects in Syria and Iran are operating under the concept of upstream control. The water demands of the individual secondary canals, determined by the irrigation agency (or by groups of farmers) are aggregated up to the headworks, taking into consideration transmission time and conveyance losses. Although this process is still cumbersome operation is greatly simplified through the use of computers. Various devices have been introduced in the region under these projects:
The operational concept of the main canals of Sidorejo, and HLPC projects is automatic downstream control, meaning that any variations of demand from downstream is automatically transmitted upstream up to the headworks through a number of gates reacting to the variations of downstream levels. Downstream control requires main canals to be level-topped. The Majalgaon main canal was already partly built with some sloping berms when the decision to modernize the system was made. Therefore, the main canal will be operated under the constant volume concept which does not require top level canals over the total reach between the control structures. The cross regulators will operate under the instructions received from a central control centre. A frequent misunderstanding of downstream control is that the users would have the possibility to withdraw as much water as they want. This would be the case if downstream control was applied down to the farmer outlets and water was not priced on volumetric basis. In the cases of Sidorejo and Majalgaon, the delivery of water to the secondary canals remain under the control of the irrigation agency. Secondary canals are or will be operated under the concept of upstream control. In Sidorejo, these canals were equipped of automatic float-operated gates and in Majalgaon of long crest weirs. In the case of HLPC, the secondary branches will consist in semi-closed pipes, maintaining the continuity of downstream control down to the tertiary outlets (mogha).
The only pilot operation where water was distributed on demand at the farm level was of very modest scale (150 hectares) at the end of a distributary of the Mahaweli project in Sri Lanka. The objective of that operation was to compare the demand schedule to a conventional agency controlled rotation schedule. The project operated successfully for six seasons and then was reverted to rotational supply like the rest of the Mahaweli scheme. The likely cause of failure of that research operation is the lack of financial incentives for the farmers to save water and the lack of agronomic reasons for rice cultivation to limit application of water.
Construction of the Kirkuk project, in Northern Iraq, covering an area of 230 000 ha, proceeded rapidly until the mid 1980s. Design of this project is making use of all the possible modern techniques of water control: remote central control, float-operated constant downstream level gates, low-pressure pipes and radio-communications.
Flow at offtakes of canals under upstream control in the above projects is controlled by constant flow regulators also called modules. Modules is a term used to designate a passive flow regulator which remains functional over a wide range of upstream level by successive changes in the flow regime. These devices have been used for about 50 years in the Mediterranean basin countries and elsewhere. They are extremely easy to use since they do not need any measurements or reference to charts or tables. Another major advantage over other flow regulators is that they do not need any resetttings of the gates between changes in flow targets, assuming that the water level in the parent canal remains within certain limits.
MODERNIZATION OF EXISTING SCHEMES
It is now common place to state that reduced O&M allocations and inadequate maintenance have contributed to system deterioration and disappointing system performance. Unfortunately, past rehabilitation programmes have often failed to improve or even sustain performance. The question is what kind of rehabilitation is needed. Rehabilitation should not be simply re-establishment of original designs but should consider modifications to reflect operational past experience. The World Bank has frequently advocated a more systematic diagnosis of scheme-level problems to ensure that physical improvements contribute directly to a workable irrigation service plan. A more realistic approach to water control is needed. A frequent argument is that designs should be simplified. This paper argues that the operational procedures should be simplified, not the design. Indeed, modernization of an existing project is a very complex task. The designer has to face a number of constraints imposed by the layout and other characteristics of the existing infrastructure (slope and profile of canals) limiting considerably the possible options. Furthermore, his options are also limited by the need to maintain the continuity of irrigation during construction works and to make maximum use of the existing facilities.
Modern hardware and software techniques now exist to improve performance of existing schemes given the above constraints. Reliable instrumentation has now been developed to perform the following functions in the harsh environmental conditions of irrigation projects:
Hydraulically automated gates are no longer the only option for the automation of control structures. Automatic controllers have been developed to equip conventional gates which were manually operated. These gates could be actuated by local controllers or by a remote signal. The development of these new instrumentation, communications and automation technologies now provide a large variety of tools to improve the water distribution function of existing systems. Modernization can be introduced in progressive steps:
The application of these technologies is highly dependent on the reliability of power supply, the quality of service for maintenance of the electronic and electro-mechanical equipment and the availability of spare parts and also to the sensitivity of electric and electronic equipment to factors such as climatic conditions.
One of the first examples of remote monitoring in the region is the Muda project in Malaysia, which has been recently upgraded after 20 years of service. Very large project are now under development in India and China. Remote monitoring and decision support system of the Hetao project serving 730 000 hectares in Inner Mongolia in China, built in the 1960s, is now under study. The Narmada project which will serve about 1.9 million hectares in the state of Gujarat is still under construction. The 438 kilometre-long main canal with a head capacity of 1130 cubic meters/sec will be operated under dynamic control.
Software tools were also developed to simulate the operation of canal systems through mathematical modeling. A large number of models are now available such as the SIC model developed by CEMAGREF for an application in Sri Lanka on the Gal Oya canal. The CARIMA model was developed by a consulting firm for numerous applications, CANALCAD is used by the Iowa Institute of Hydraulic Research and many others. These simulation models have been frequently used by research organizations to determine optimal operation of existing canal systems without any modifications to the existing infrastructure. For example, IIMI has carried out a detailed study of the Chasma Right Bank Main Canal in Pakistan in 1994.
This canal was designed for crop-based operation with a design duty about three times the values of other projects in the Indus Basin. The present operation of the first two stages of this project is very inefficient because no provision were made in the original design to operate the main canal at less than full supply. It would be highly desirable that the design of the last 150 kilometres of the main CRBC canal be reviewed before construction starts in order to examine the possibility of modifying the control structures to simplify operation or improve safety of operation. A possible alternative solution would be to replace the proposed gated cross regulators by composite regulators, meaning a combination of gates and long crest weirs. In the case of power outages, safety and automation of canal operation would be maintained for a certain period. This design was adopted for the main canal of the Haouz scheme serving the Marrakech oasis in Morocco. This canal is operated under the concept of dynamic control, which is the most advanced stage of remote automated control.
There are very few examples of modernization of the physical infrastructure of existing systems in the Asia region and elsewhere. One not well-known example is the Office du Niger in Mali. Operation of the feeder canal was considerably improved through the use of simulation modelling; the main canals were remodelled using the concept of downstream control and modular distributors. Various alternative solutions for modernization of the irrigation infrastructure in the northeast of Thailand have been tested during the last years. Thailand has now an on-going programme of modernization, called NEWMASIP which has opted for water-level control in main and lateral canals through the use of composite regulators (gated duckbill weirs). The project engineers recognize the simplicity of operation of the modular distributors. However, because of the high costs of imported equipment, the consultants recommended to continue to use calibrated single gates. Local fabrication distributors or use of fibreglass instead of steel, as it is now done in Mexico, may change that recommendation.
ECONOMICS OF MODERN IRRIGATION TECHNOLOGY
A common argument against modernization is the perception that modern design is far more expensive that conventional design. There are very few cost comparison studies to refute that argument because of the limited cases where both conventional and modern design have been considered and studied in detail. The results of detailed cost comparison studies for three projects in Indonesia, Pakistan and Mexico (Sidorejo, HLPC, Cupatizio) led to the conclusion that modern systems do not substantially increase investment costs. If only the direct costs of conventional and modern design equipment are compared, modern designs would not be selected because of higher initial costs. The advantages of modern design concepts become evident if the increased benefits in terms of higher efficiency, higher agricultural production, reduced farm labour and other benefits are taken into consideration. The HLPC project in Pakistan is a case in point: the cost of the automatic control structures, including civil works and mechanical equipment is about twice the cost of manual gates. However, the net cost of automating the LHPC alone is about 8 percent of the total cost of the canal and 2.5 percent of the total cost of the project, including cost of secondary canals and watercourses. The consultants estimate that automation can be economically justified by an increase in agricultural production of only 0.5 percent or a saving in Tarbela power foregone by only 2 percent, either of which should be easily attainable. The results of the cost comparison for the Sidorejo project in Indonesia compare well with the results of the HLPC project: the incremental cost for automation was only 3 percent of the total cost of the project.
CONCLUSION
The case for modernization of irrigation schemes in the Asia region is compelling. Low performance of existing schemes has been well documented. Increased world population and competition with other uses of water require that irrigation projects be better managed and more productive. Design engineers must be aware of the limitations and of the implications of their design for maintenance, operation and flexibility of water use. Designers must understand that the farmers can increase production only with reliable and convenient water supply.
Modernization programmes should be associated with programmes for increasing the participation of farmers in irrigation management. It may be unreasonable to expect that farmers could better operate irrigation schemes which are not realistically manageable by an irrigation agency. Modernization and farmer participation are two programmes which are self-supporting. The recent experience of Mexico which combined these two programmes demonstrates that user associations are very active players in the modernization of the schemes for which they have taken full responsibility of management. It is generally known that a major part of the irrigated areas of the world are at present located in the Asian Region.
REFERENCES
Merriam, J. 1985. Demand Irrigation Schedule, Concrete Pipeline Pilot Project, Mahaweli Development Board, Area H, Block 404, D-1. Maheweli Development Board, Sri Lanka.
Merriam, J. 1990. Galdigaltar Tank Irrigation Pilot Project. Irrigation Department, Khargone, Madhya Pradesh, India.
Merriam 1991. Flexible Irrigation Supply Pilot Projects. Part II: Sri Lanka, Pakistan, India, Egypt. ASCE I&DD Conference, Hawaii.
Merriam, J., DeSilva, N.G.R. and Bandaragoda, D.J. 1987. Six Seasons of Demand Schedule Irrigation for Improved Water Management in Sri Lanka. International Commission on Irrigation and Drainage, Thirteenth Congress, Rabat, Morocco.
Appendix 1. Case studies
INDIA
Substantial differences in agroclimatic and socio-economic conditions and historical development of irrigation between regions of India have resulted in a wide variety of irrigation infrastructure and management concepts. A broad distinction can be made between systems that distribute water according to pre-established rules (water duties) and systems that attempt to meet crop water needs. These two broad categories are often referred to as supply-based and demand-based. However, in both cases, the irrigation scheduling is decided by the irrigation agency.
This appendix describes two pilot projects with different concepts. Majalgaon is part of a large-scale project in the state of Maharashtra and Gadigaltar is a small tank project in Madhya Pradesh, where the farmers would have more responsibility in water allocation and distribution.
The Majalgaon Irrigation Project, located in the valley of the Godaveri River and serving 58 000 ha, is an expansion of the large Jayakwadi project with a total irrigable area of 350 000 ha. The expansion became possible after the Majalgaon storage dam, with a capacity of 450 million m3, had been constructed to regulate the water of the Sandphana River. This water source is complemented through releases from Paithan dam into a link canal.
The Majalgaon main canal and parts of the distribution system had been partly built when the Irrigation Department of Maharashtra decided to use the project to test alternative delivery method to the shejpali system, commonly used in the state of Maharashtra. Under the shejpali system, individual farmers receive individual water allocations for sanctioned crops. However, the shejpali system requires a precision and flexibility of water control that is increasingly difficult to achieve with the existing control structures and the present fragmentation of land. The proportional delivery system, used in North India, is inflexible and not well suited to the conditions in Maharashtra, such as variable soil conditions, diversity of crops, and rolling topography. Under the new concept water will be sold in bulk to water user associations, each serving about 300 to 400 ha. The WUAs will get annual quotas and are responsible for the distribution of water and the maintenance of the water courses and field channels. They order the volume of water required for each irrigation turn. The internal water distribution will be essentially on rotation and proportional to the size of the holding, but other arrangements such as buying and selling of water are possible.
Several alternative water control methods were studied in 1990 to provide the required operational flexibility. However, since most of the system is already completed or under construction, the structural modifications had to be limited. The proposed solution makes use of the storage capacity of the main canal, which was originally sized to serve an area of 100 000 ha. The main canal will be operated under the constant volume concept. The cross regulators will be manually operated on the instruction of a central control centre. The turnouts of branch and minor canals will be equipped with downstream control gates and modular distributors. Long-crested weirs and modular distributors will be installed in minor canals when the accuracy of existing structures is insufficient.
A preliminary estimate indicates that the cost increase caused by the addition and modification of control structures is in the order of 5 percent. Construction or modifications of these control structures is scheduled to start in 1993.
The Gadigaltar tank project in Madhya Pradesh has recently been constructed. The guiding criteria of this project is to provide farmers with control at his farm turnout on the frequency, rate, and duration of flow with some restrictions from the project organization in case of drought. Using the limited rate, arranged schedule, the small irrigation groups will be responsible for arranging with the farmers the irrigation schedule. It is anticipated that delivery will be made within one day of the water request. It is expected that the increased efficiencies through improved control and use of pipes will provide appreciably more water.
The project covers about 1,150 ha with more than 500 farms. The main infrastructure includes:
About 500 ha are served from the sloping canal through five pipe laterals and the remaining 660 ha from the level-top canal through five conveyance pipelines and one direct outlet. Float valves and an overflow stand are used to limit the static pressure in the pipes to about 5 m.
There are 67 groups of farmers, each with a group irrigator who arranges water deliveries with the central water coordinator's office. Most of the groups consist of 5 to 10 farmers with a total area of about 10 to 25 ha. Each group has its own water meter and a connecting gate to the supply system. The water will be supplied with a limited rate, arranged schedule with the ensured minimum flow rate of 30 litres per second.
Interestingly, construction of the primary tank and of the first 5 km of the main canal was nearly completed when the modernization of the design was decided. This constraint was solved through the construction of the overnight storage reservoir. For a detailed description see Merriam (1990).
INDONESIA
Small run-of-the-river systems and small and fragmented land holdings are characteristic of Indonesian irrigation. Water is generally distributed under central control. Water demand for each tertiary block in an irrigation system is assessed by the administration every 10 to 15 days. This requires knowledge of actual irrigated areas, the type and area of each crop in every block, and precise estimates of conveyance losses. In practice, there is considerable reliance on estimated rather than precise information.
The physical infrastructure that has evolved in association with this management system requires a high degree of control. However, valid design standards recommend undershot gates at cross-regulators and adjustable Romijn weirs at canal intakes. This is the worst combination of control structures with regard to hydraulic stability, as explained in this paper. Recent studies by IIMI have shown that even if the operating procedures are truly followed, planned and actual discharges often differ considerably in practice.
Sidorejo Irrigation Project. In the mid 1980s, the Indonesia Directorate General of Water Resources Development selected the Sidorejo Irrigation Project, a subsystem of the proposed Kedung Ombo multipurpose dam and irrigated scheme to test modern canal control and to determine its replicability to other irrigation systems. The recently completed project is located in central Java about 70 km east of Semarang and serves an area of 5 200 ha. This project is of particular interest since it is the first large-scale experience in south and east Asia under predominant rice crop that has adopted an advanced control concept for an entire system.
Water is supplied to the Sidorejo pilot system through a diversion weir, approximately 9 km downstream of the storage dam. The main canal has a total length of 13 km and a maximum design capacity of 9 m3/s. The main canal is operated under downstream control; the secondary and tertiary canals taking off from the main canal are operated under upstream control. The main canal is equipped with automatic float-operated gates maintaining a constant downstream level. The water level in the secondary canals is upstream controlled through automatic hydraulic gates. Discharges are controlled by modular distributors.
The control concept adopted for the Sidorejo pilot project is quite similar to the one used in Mediterranean countries. However, it differs in the control structures for the distribution system by not making use of static structures such as diagonal or duck-bill weirs. This deviation was justified at design stage by the risk of siltation but could create a maintenance problem in the future.
Hydraulic tests of the Sidorejo project have recently been completed. The main canal is operating satisfactorily, but several corrections were required in the installations of mechanical equipment in the smaller canals. The intent was to monitor the performance of the new design to determine the advantages and disadvantages over conventional design systems in Indonesia. The new design would allow change in the present water allocation procedure, which is based on historical rainfall records, to a real time operation based on actual rainfall measurements.
A detailed comparison of construction costs has been carried out by consultants. This study shows that the costs of the Sidorejo project with automatic control is similar to the cost of the project if it had been built using conventional Indonesia design standards. The hydromechanical equipment is more expensive, but these extra costs are compensated by substantial savings in civil works. In general, earthworks and lining are more expensive for canals under downstream control because of the need for horizontal banks. In Indonesia, however, a wide shallow section is adopted for traditional upstream-control canals to minimize variations of flow levels despite substantial variations in discharges. According to Indonesia design standards the ratio of bed width to water depth at maximum discharge should be 5 to 5.5. In the new design the ratio is only 1 resulting in a 16 percent cost saving. Using 1986 unit costs, the results of the costs comparison are presented in Table 1.
TABLE 1
Cost comparison
|
|
Traditional System (Rps million) |
Automatic System (Rps million) |
Difference (percent) |
|||
|
Main canal |
|
|
|
|
||
|
Earthwork and lining |
2,380 |
2,047 |
|
-16% |
||
|
Flow control structures |
|
|
|
|
||
|
|
-civil works |
165 |
133 |
|
-24% |
|
|
-equipment |
236 |
474 |
|
49% |
||
|
Other structures (roads, bridges, culverts) |
2,347 |
2,231 |
|
-5% |
||
|
|
|
Total |
5,128 |
4,885 |
|
-5% |
|
Secondary canal |
|
|
|
|
||
|
Earthwork and lining |
134.5 |
|
134.5 |
0% |
||
|
Flow control structures |
|
|
|
|||
|
|
-civil works |
11.1 |
|
11.1 |
0% |
|
|
-equipment |
15.6 |
|
22.9 |
31% |
||
|
Other structures (roads, bridges culverts) |
118.4 |
|
118.4 |
0% |
||
|
|
|
Total |
279.6 |
|
286.9 |
3% |
MIDDLE EAST
There is virtually no information available in the irrigation literature on the performance of large-scale modern irrigation schemes built in the Middle East in the 1960s and 1970s. This section discusses some aspects of two large schemes featuring modern design concepts. The first scheme, near Kirkuk in the north of Iraq, covers 230 000 ha and is still under construction, the other scheme is located in the Guilan plain in northern Iran near the Caspian Sea, it covers 270 000 ha and was completed in the late 1960s. An in-depth performance study of the Guilan project which has now been in operation for more than 20 years, would certainly provide very useful lessons on the modernization of irrigation schemes.
Kirkuk Project, Iraq. Construction of the Kirkuk project about 300 km north of Baghdad proceeded rapidly until the mid 1980s when it stopped because of political and military events. The project is supposed to divert water from a tributary of the Tigris River, regulated by the Dokan dam with a storage capacity of 5 thousand million m3. The climate of the region is continental, and the annual average rainfall is about 350 mm. The soils of fine texture are moderately saline, but contain a high proportion of gypsum, which pose serious problems for canal lining.
The project comprises essentially of:
To ensure minimum response time and high flexibility in water distribution, the feeder canal is regulated by the associated levels remote control method, maintaining constant head loss between two successive regulators. Each regulator is automatically controlled and monitored by a central computer, communication is provided through radio links. Stability of the regulators was checked on a mathematical model. The gates of the main canal are also automatically controlled, using P.I.D. controllers.
The flows in the secondary canals are controlled by hydraulic downstream control gates and modular distributors. Slide gates control the pipe offtakes on the canals. The hydrant discharges at the farm turnouts, fixed at 70 l/s, are controlled by flow limiters.
Guilan Project, Iran. The Guilan project located on the southeast coast of the Caspian Sea benefits from a particular climate unique in western Asia. The region is open to maritime influences and isolated from the Iranian plateau by the Elbrouz Mountains, which rise to elevations ranging between 2 500 and 3 000 m. Temperatures are similar to the Mediterranean climate, but average annual rainfall exceeds 1 000 mm. The project is supplied by Sefi Roud River water regulated through a large storage dam with an active capacity of 800 million m3. There are considerable variations in the annual flow of Sefi Roud, with a median flow of 3.6 billion m3. Rice is the main irrigated crop; average rainfall during the growing season between April and September is about 250 mm. The area is densely populated (more than 330 habitants per km2), and the average farm size is 0.8 ha.
The project implemented between 1962 and 1969 comprises two irrigation areas, each supplied from a diversion dam: (1) the upper zone covering 70 000 ha with a 17 km long tunnel and the 52 km long Foumen canal, with a capacity of 35 m3/s, and (2) the lower zone covering 81 000 ha on the right bank and 115 000 ha on the left bank served by two main canals of 67 and 114 m3/s respectively.
The two main systems are operated under upstream control through use of long-crested weirs and hydraulic gates. The offtakes are equipped with modular distributors. About two-thirds of the irrigated area (243 000 ha net) are still served by traditional unlined canals. The rest of the area is served through lined branch canals and equipped with long-crested weirs and modular distributors and raised prefabricated canals (canalettis). The civil works are still in excellent condition, and the hydromechanical equipment is progressively replaced after 25 years of service.
Water releases are decided by the Guilan Water Authority, and water users are informed through their water masters, who operate the secondary systems and report on the system status back to the Water Authority. On average, 1.7 thousand million m3 are diverted annually to irrigate about 142 000 ha of paddy fields. It seems that the project performance in terms of efficiency is reasonably good and close to the expectations at the planning stage. Operation of the project is simplified through the use of hydraulic regulating structures and appears to be quite appropriate for the prevailing rice irrigation with moderate rainfall during the growing season.
MALAYSIA
The initial stage of irrigation development in Malaysia was intended to provide controlled drainage to existing rice lands. With the advent of double cropping after independence in 1957, the main objective was the development of reliable water supply for the second crop, which involved the construction of storage and diversion dams and the upgrading of existing irrigation systems. This section describes two large irrigation schemes with aspects of modern water control.
Muda scheme. The scheme of 98 000 ha is located in the northwest of peninsular Malaysia. This scheme accounts for 40 percent of the national rice production and is critical to the rice policy. The project is not only a case of successful upstream control, but it is also one of the best documented projects. The infrastructure comprises of two storage reservoirs connected by a tunnel, a diversion dam 35 km downstream, and two main canals, north and south, running along the perimeter of the command. Cross-regulators on these canals are equipped with over-shot motorized gates. Offtakes serve the lateral canals that run westward to the sea and the sublaterals, typically at 2 km intervals. Cross regulators on lateral and sublaterals as well as offtakes, are simple, hand-operated, undershot structures. A remote monitoring system in project headquarters was built to provide engineers with real time information on reservoirs and canal water levels and on rainfall in the catchment areas between the storage and diversion dams to predict the unregulated flow.
The combination of remote monitoring system and overshot gates on the main canals has contributed to the efficient operation of the main system. The adoption of conventional water control for the distribution system, however, resulted in fluctuating water levels and unreliable water deliveries to rice growers.
The mechanization of rice farming, particularly the conversion from transplanting to direct seeding, had marked effects on demand for irrigation water. It is now much more important for farmers to control the amount and timing of water deliveries. In practice, it also meant that planning and harvesting dates are less uniform than they used to be. To achieve the control over amounts and timing of water delivery, farmers in Muda have installed their own low-lift pumps to lift water from public canals and drains. Although the costs are higher than for public irrigation water, pumping is preferable to insufficient and untimely water supply and subsequently reduced yield.
Kemubu-Kemasin. Improving the operation of the distribution system through easily operated structures is the approach adopted for the Kemasin extension of the Kemubu project.
The Kemubu project is located opposite the Muda project on the northeast of peninsular Malaysia near the Thai border. The 17 000 ha project was originally supplied by pumping Kelantan River water by means of five diesel-driven pumps with a total design capacity of 30 m3/s. The south main canal is operated under downstream control. A few of the lateral canal offtakes are equipped with modular distributors and the remaining by adjustable Romijn type weirs. The farm intakes are equipped with adjustable undershot gates combined with a flow-measuring device. After completion in mid-1975, some difficulties occurred when it was found that the effective capacity of the pumping station was 30 percent less than expected and that the proportion of the light soils was higher. This problem has been solved with the completion in 1989 of a new pumping station of 6 electrically driven pumps with a total capacity of 42 m3/s.
Another problem in Kemabu was to control the flow in the minor distribution system through manually operated gates and the increasing importance of diversified cropping, that required fine tuning of water supply. These difficulties may have been the reason for selecting different control structures for the Kemasin extension area. The distribution system for that extension is equipped with gated flow-dividing structures making it possible to divide the incoming flow either proportionally to areas served (when all gates are open) or according to farmer's requests (flexible structured design).
SRI LANKA
Modernization of two distributary canals was carried out in Sri Lanka under the Major Irrigation Rehabilitation project financed by the World Bank. Although of modest scale (150 ha each), monitoring these two canals provides some interesting information.
The structural modification in the design of these two distributaries, compared with a conventional gated system, included:
Monitoring of these distributaries and of the areas served did not show significant differences in water use and crop yields compared with their respective control areas, but some doubts exist regarding the reliability of these data. It was found, however, that the operational costs of the new design were about 40 percent lower then the operational cost of the conventional design. The general feeling in the Sri Lanka Irrigation Department is that the modifications provide a superior operation facility. The farmers also express their appreciation for these controls as they can easily check the quantity of water delivered to their field.
Merriam reports in various publications (1985, 1987, 1991) on a pilot project in Area H of the Mahaweli Scheme. The pilot project covers about 150 ha on the lower end of a unit served by one distributary. The farmers are provided water on demand, flow is limited to 20 l/s. The automated supply system consists of a reservoir, a downstream level control gate, top level canals, and low pressure concrete pipes supplying individual turnout valves. The objective of the project was to compare the demand schedule to a conventional agency controlled rotation schedule. The principal points of comparison were: costs, crop production, water use, and social effects. The project operated successfully for six seasons (three years) and interesting results were achieved. Unfortunately, after the end of that period the project reverted to rotational supply schedule like the rest of the area. No water user association had been developed to prevent this, though the farmer results had been very satisfactory and further experimentation would have been valuable.
Table 2
Methods of operation and structures for main and secondary
irrigation distribution systems
|
Operational concept |
Main canal structure |
Function of structure |
Advantages |
Disadvantages |
Applications or design notes |
Practice to improve operation |
Project and country |
|
1. FIRM UPSTREAM CONTROL |
Proportional dividers |
Divide incoming flow into predetermined (and generally fixed) proportions
at each bifurcation point |
No gate movements needed. |
Theoretical equity is not actually achieved because it is virtually impossible
to design and install outlets so that they function as predicted over
a range of flows. |
In Warabandi of NW India and Pakistan, lower branches may be ungated
and use a rigid rotation. |
If proportional control is needed for rotation further down the system,
main and secondary canals should still be operated with improved control
methods to avoid disadvantages listed. |
Numerous, NW India and Pakistan |
|
2. GATE UPSTREAM CONTROL |
- Typically sluice or radial gates. |
Structure should maintain a constant upstream water level. Instead, operators
are instructed to use structures as flow-control devices. |
None |
This is a very common misapplication of upstream control. Operators are
asked to do the impossible: with upstream control a constant flow rate
cannot be obtained both through the turnout and the check structure. |
|
|
|
|
‘with water-level control’ |
|
First gate, at inlet to canal (and generally an undershot or orifice-type
gate) controls flow into canal. |
Low initial cost relative to more modern control techniques. |
Flows must be known in advance and be well controlled at inlet and all
outlets to minimize tailender problems. |
Suitable for arranged deliveries, rotations or proportional control from
tertiary canals. |
Install buffer (balancing) reservoirs throughout system. |
|
|
‘with structures for manual operation’
|
Sluice gates (underflow). |
|
|
Large forces required to move the gates. |
|
Use side weirs with constant spill (back into the canal) to reduce number
of gate movements. |
|
|
Radial gates (underflow). Motorized manual movements |
|
Small forces required to move them if counter-balanced; they do not stick
easily. |
Hourly adjustments needed. |
|
Use several smaller parallel gates rather than a few large gates. |
Rio Sinaloa and Yaqui, Mexico |
|
|
Stoplogs |
|
Only a few minor changes needed per day. |
Stoplogs may be stolen for firewood. |
|
Use stoplogs with maximum dimensions of 2 m x 5 cm x 10 cm to facilitate
handling. |
Madera ID, California and many western districts, USA |
|
|
Long-crested weirs |
|
Upstream head variations during a day may be almost negligible. |
Do not allow for different controlled water levels during different flow
regimes; will silt up unless underflow gates are provided at downstream
ends. |
Maximum effective design length is about 8-10 times the channel width. |
Install underflow gates at downstream points in each structure to flush
silt through the structure. |
Mocambinho, Brazil Mae Tang, Thailand Kemubu, Malaysia Coello, Colombia |
|
|
‘with structures for automatic operation’
|
Automatic electrical controls, undershot or overshot gates |
|
Able to maintain very precise upstream water levels automatically. |
Power cuts or poorly trained or supplied maintenance personnel will result
in failure. |
Can be monitored and controlled remotely in case target depth is changed,
or in an emergency. |
Use industrial-grade controllers and water-level sensors. |
Munda, Malaysia Friant-Kern Canal, California, USA Imperial ID, California,
USA |
|
Hydraulic constant upstream level gates. |
|
Very simple. |
May be greater initial cost than electrically controlled automatic gates.
|
Decrement can be reduced if small gates are used in parallel rather than
one large gate. |
To reduce price, install one automatic gate in parallel with some manual
gates. |
Sorraia, Portugal Benil Amir, Morocco Dudly Ridge WD, California, USA |
|
|
3. DOWN-STRAM CONTROL WITH TOP LEVEL CANALS
|
Gates are always automatic |
Maintains a constant water level immediately downstream of gates there
by supplying flow into downstream pool as needed. |
Offtakes can be shut off or flows reduced at any time without advance
notice. |
Longitudinal slope should generally be less than 0.0003. |
Demand operation of main and secondary canals is not to be confused with
on demand deliveries to individual farmers, chaks, or watercourses. |
Turnouts should be located at headends of each pool rather than at tailend
of pools. |
|
|
Automatic electrical controls with undershot or overshot gate. |
|
Same as upstream electrical. |
Same as upstream electrical. |
|
|
|
|
|
Hydraulic constant downstream level gates. |
|
Same as upstream hydraulic gates. |
Same as upstream hydraulic gates. |
|
|
Sidorejo, Indonesia Massa, Morocco Retail Office du Niger, Mali Tranquility
ID, California, USA Victoria, Australia Bas Rhone-Languedo, France |
|
|
4. UP-STREAM & DOWN-STREAM COMBINED CONTROL |
Automatic upstream and down-stream control hardware. |
First gate, at inlet to upper main canal, is used for flow rate control
into system. |
Less expensive than a complete downstream- control system, yet with about
same simplicity and advantages. |
System must be operated on an arranged basis (more restrictive schedules
are also possible) because flow into the top of canal is based upon approximate
anticipated demands. |
Ideal for a canal with an initial steep slope that ends on flatter topography.
|
Use modeling to predict wave travel time from inlet to buffer reservoir. |
Friant-Kem, California, USA Doukkala Sidi-Bennour, Morocco |
|
5. CENTRALIZED CONTROL |
Often manually upstream controlled gates. |
Operators are told by central control how to operate gates for each day’s
needs, which are general predicted by some model in central office. |
Central office does not need to listen to field. |
Rarely if ever works as intended, because the control is “open-looped”
without any feedback; design and operation assumptions are usually incorrect.
In order to even partially work, extensive field calibration of hydraulic
parameters must be done. |
This is not really a control technology but rather a method of management.
It is frequently proposed, however, in recent literature as a means of
control. |
|
NE Irrigation, Thailand Upper Pampanga, Aurora-Penaranda, Philippines |
|
‘with arranged delivery’ |
Electrically controlled, automated gates; micro-processors at each gate.
All gates are electrically moved from a remote centralized control centre.
Turnouts are generally not automated, nor are they remotely controlled. |
All gates respond to commands from a centralized control center. |
Allows fast response throughout system in case of an emergency; all gates
can be shut down quickly. |
These methods generally require 1-2 days’ advance notice of any
turnout flow-rate change responsive. |
Suitable for very large canals and primarily for conveyance. |
Use same hardware and communications system, but modify the control logic
to utilize dynamic regulation (explained below). |
California Aqueduct, USA Central Arizona Project, USA |
|
6. RESPONSIVE SYSTEMS FOR SLOPING CANALS |
Electrically controlled, automated gates. |
Responds to computer instructions. Some maintain water levels; others
maintain pool volumes. |
Similar in function to downstream control on level tops. |
High risk if personnel, maintenance, initial equipment quality, power
backup, communications are not superb. Require a high degree of initial
planning and modeling work and sophisticated maintenance and operation
personnel. |
Centralized dynamic regulation methods may be compatible with inline
hydroelectric installation operations; no independent control methods. |
Large canal cross sections and buffer reservoirs always make control
easier even with sophisticated modeling and control. |
|
|
‘with local independent controllers’ |
Radial gates are generally used. |
Controls flow rate into a pool in order to maintain a specified water
level at some point in that downstream pool (i.e., they operate on demand). |
Small, relatively inexpensive controllers. |
These control methods have not had wide application. Knowledge is still
being gained regarding design rules and requirements for simplicity and
techniques for determining proper control algorithm constants. |
Methods do not appear to work well on steep slopes. Since they are still
in development, a full history of past research and applications is advised
before use. |
|
Tehema-Colusa, California, USA Canal du Sahel, Niger |
|
‘with dynamic regulation’ |
Centralized, computerized control center. |
Controls flow into pool in order to maintain desired water level or pool
volume. |
Very fast, responsive operation. |
Highly sophisticated equipment. |
Several successful systems are in place. Proven technology |
|
Canal de Provence, France Canal de Haouz, Morocco |
|
7. PRESSURIZED SYSTEM |
Closed pipe system |
For main and secondary distribution, pipelines are generally high-pressure
pipe. |
Highest conveyance efficiency. |
May require expensive pumping. Initial investment generally higher than
canals. |
Automatic screening needed at entrance to prevent inlet blockage and
subsequent pipe damage during refilling. Adequate pressure relief and
air venting designs needed. |
Common problem is to undersize the pipes; systems can be very flexible
if pipes are large enough. Ideally suited for volumetric deliveries. |
Westlands WD, Belridge WD, Wheeler Ridge WD in California, USA Nehbana,
Tunisia |
David J. Molden and Ian W. Makin
Senior Irrigation Engineers, International Irrigation
Management Institute (IIMI),
Colombo, Sri Lanka
INTRODUCTION
Irrigation management transfer is defined as the transfer of management responsibility and authority for irrigation systems from government agencies to farmer or other non-governmental organizations (Vermillion, 1996). Typically, countries adopt management transfer policies in order to reduce the cost of irrigation to government. In recent years, management transfer has become an increasingly common policy trend worldwide.
In many cases, rehabilitation or modernization efforts are carried out simultaneously with management transfer. A common reason for rehabilitation at the time of management transfer is to repair deteriorated infrastructure to bring it up to a level that local organizations can manage. Modernization provides improvements to an existing system to permit the achievement of enhanced objectives. Management transfer can be considered a type of modernization which involves modernizing institutions and their management functions and possibly modernizing infrastructure to help institutions meet expanded management objectives.
Modernization together with management transfer does present significant opportunities for improvement of irrigation performance. Likewise, ill-planned or poorly executed modernization programmes can lead to a costly failure of the management transfer process. This paper outlines institutional and infrastructure design considerations for modernization during a management transfer process.
MANAGEMENT TRANSFER AND INSTITUTIONAL CHANGE
Three types of institutional adjustments are required for successful management transfer of irrigation operation and maintenance responsibilities to non-governmental organizations. First, suitable local organizations able to take up the responsibilities must exist. (Here, local organizations is used as a general term to refer to a number of possible non-government or semi-government possibilities including water users associations, public utilities, irrigation districts, mutual companies, or contractors (see Vermillion, 1996, for descriptions).) Second, the existing agency must adapt to its new role. Finally, appropriate policies and regulations are required to provide a supportive environment for local organizations to undertake their necessary functions.
Recognizing that there are many existing management arrangements between governments and farmers in irrigated agricultural systems, the process of management transfer can be simply represented as in Figure 1. On the left of the diagram are those irrigation systems where the irrigation agency takes the major responsibility for operation, maintenance, and management of the irrigation system. Here funding for the system comes from the government with varying degrees of cost recovery from farmers. At the other end of the spectrum are purely farmer managed irrigation systems, built and operated by farmers with funding for O&M and other management functions borne by farmers. Management transfer is the process of shifting from agency managed toward locally managed irrigation systems.
FIGURE 1. Management transfer as a shift from agency to local management
Some arrangements of management transfer envisage a complete turnover of O&M responsibilities to a local organization, while other arrangements consider joint government and local organization arrangements. Joint arrangements could follow several forms, but a typical pattern is for the irrigation agency to operate and maintain infrastructure for water distribution to a specified point in the system, after which a local organization takes over responsibility for delivering water. Other arrangements call for shared responsibility between the government agency and the local organization at some or all levels of the system. Management transfer demands a clearly defined interface between the areas of responsibility of the agency and local organization. It may also imply a shift in the location of the interface.
Local organizations need to adapt to their expanded role in management of operation and maintenance. In most cases, roles of existing local organizations are enhanced, while the agency’s role decreases. Establishment of new local organizations is required when they are non-existent or non-functioning before transfer. New policies, rules, and practices need to be adapted by local organizations to match increasing responsibility.
Similarly, irrigation agencies must also respond to change. In general, irrigation agencies must focus on a smaller set of management issues such as reliably delivering the allocated amount of water to local organizations, providing technical assistance, or assisting to adjudicate water rights. At the extreme case, the agency totally loses its role as water delivery service provider, and its very existence may be in question.
A third type of institutional adjustment, beyond the agency’s direct control, is necessitated when policies and regulations must change to provide a supportive environment for management by local organizations. Rights of local organizations including their water rights, rights to collect fees, and rights to levy penalties must be delineated and recognized. Other governmental institutions may have to be strengthened, for example institutions with the responsibilities for adjudicating water rights.
THE INTERFACE BETWEEN LOCAL ORGANIZATION AND GOVERNMENT AGENCIES
The point at which water is turned over by an irrigation agency to a local organization represents an important interface between local organization and governing agencies. Downstream of this point, local organizations manage water delivery service. Upstream, government agencies are involved. The most important job of the irrigation agency providing water delivery service is to ensure that the entitled amount of water is reliably delivered at the interface.
A key decision in a management transfer process is the location of this interface. The interface could be a diversion point from a river. Within the river, the agency would have responsibility of administering rights between irrigation systems, while a local organization would have responsibility for delivering water downstream of this point. The interface could lie within an irrigation system. For example in a structured system, the location of the interface may be at a tertiary head. In tank systems where management transfer has occurred in Tamil Nadu in India, the interface is at the reservoir outlet, with the government agency releasing water from the reservoir (Ramnarayan, 1996).
Allocation and other organizational rules are built around the right to water of the organization. If the supply is not reliably delivered according to the water right, it becomes very difficult for the local managing organization to deliver water according to its allocation principles. Newly formed organizations can easily fail when they cannot provide water delivery service because an irrigation agency did not provide their water delivery service. On the other hand a supply of water reliably delivered according to allocation principles puts the burden of water delivery service on the local organization.
Infrastructure must match the given or intended system of water rights and allocation and the standard of delivery service expected by the users. Likewise managing institutions, including local organizations and government agencies may be compelled to make adjustments in terms of their governance arrangements and rules and procedures for managing the irrigation system. The actual level of water delivery service is a function of how well infrastructure is managed and will ultimately influence system performance in terms of productivity and economic benefits (Figure 2). The three components of the design domain are examined in the following sections.
Water rights
Water rights specify the amount of water that users, either individually or collectively, are entitled to receive. Water rights between irrigation systems, or between local management entities are in many cases legal entitlements adjudicated by the government. Within an irrigation system, entitlements to water, often referred to as water allocation, are generally fixed and administered by the managing institution. A firm collective water right is the building block upon which local allocation procedures are based by the managing institution.
Allocation of water within an irrigation system describes the share of water users are to receive. Frequently, water shares are tied to land, and in many cases are in proportion to land area cultivated such as found in Warabundi systems (Malhotra, 1982). Alternatively, shares may be based on original investment, on time of settlement, order of appropriation of water, location within irrigation system, or ownership of shares. Allocation principles may also be crop based such as the Shejpali system where the water right is seasonal, and allows users to grow a sanctioned crop to maturity. Several case studies demonstrate the diversity of locally developed water allocation principles (see for example Maas and Andersen, 1978; Yoder, 1994).
FIGURE 2. Relationship of fundamental elements water rights, infrastructure, and institutions to water delivery service
Management and institutions
Irrigation management institutions’ central task is providing water delivery services to users. Distribution procedures, including rules for water allocation and operational procedures, relate to the quality of services provided. Effective procedures must be based on characteristics of water supply, the amount of storage available, type of existing or proposed structures, and the management intensity required to enforce water allocation rules.
Water distribution procedures can be described in terms of flow rate, frequency, and duration (Replogle et al., 1983). In supply based distribution procedures, management specifies these basic variables, such as a rotational water supply system, or a continuous flow system. A demand-based system allows flow rate, frequency and duration to be specified by the user, or to be arranged between the management and the user. Demand-based procedures allow for greater opportunity to meet changing user demands through a season. However, the tradeoff is between more expensive infrastructure, and more intensive management.
Organizational design principles have been suggested by several researchers (for example Ostrom 1992, Freeman 1989) and include a supportive policy and regulatory environment, proportionality between benefits and costs, and local organizational control of water. To provide the expected water delivery service, several auxiliary tasks must be performed by the managing organizations such as policy setting, maintenance, drainage, conflict resolution, and resource generation. These important organizational design considerations are also in large part influenced by infrastructure. The benefits in terms of increased productivity may be offset by the costs of maintaining and managing the irrigation system. Designs for modernization must provide for adequate management capacity to take advantage of the degree of flexibility provided by the infrastructure, no matter how rigid or how flexible.
Irrigation infrastructure
Irrigation infrastructure consists of irrigation and drainage facilities required to deliver allocated water to, and remove excess water from, land to provide a suitable environment for agriculture. Irrigation employs a wide variety of infrastructure. However, two descriptive variables are considered here: ease of operation and maintenance and capacity to deliver water entitlements.
In the design of irrigation infrastructure decisions are taken on the intended methods of operation that will be instituted once construction is completed. Assumptions are also made on the standards of maintenance that will be applied during the life of the infrastructure. An essential component in the design of modernization, which includes transfer of operational responsibility, is a review of whether the original design assumptions will remain valid.
Regulating structures such as canal offtakes can be described in terms of their capacity for flexibility (Figure 3). Rigid or fixed structures are those which cannot be regulated such as fixed proportioning weirs. Structures that can only be opened or closed offer slightly more flexibility. Flexible structures are those where discharge can be gradually varied, such as gated orifices, variably proportioning weirs, or automated sluice gates.
The advantage of more flexible structures is their capacity to control the timing and discharge of water such that the required volume of water can be accurately delivered. This flexibility is provided with an increase in costs associated with capital investments, management intensity, and possibly maintenance.
FIGURE 3. Relationships of key features for various regulating structure types
Fixed structures offer advantages such as low management intensity and a high level of transparency. Local organizations may place a premium on transparent systems of control and thus may demand less flexibility. Such organization often prefer controls which are ‘open or closed’, which enable members to confirm operational actions more easily than is the case with more flexible regulating structures.
On-demand supplies to individual farm holdings is the most desirable design and operations package from the water users’ point of view (Merriam, 1992). This type of service requires flexible infrastructure. Similarly, highly automated control systems offer advantages in terms of water delivery performance (Plusquellec et al., 1994). In both cases capital and maintenance costs are high, so that the benefits received must outweigh costs. Also, experience in some cases has shown that automated structures are susceptible to unauthorized manipulation, with negative impacts on delivery performance.
Manual regulation of canals offers savings in capital expenditure however additional operational and maintenance expenditures will be required and experience has shown that providing reliable water delivery services has proved difficult to sustain. Passively managed systems based on hydraulic proportioning of flows, while less flexible, offer considerable advantages in terms of operational simplicity (Shannon, 1992).
Evidently there is a trade-off between service and cost. There is growing evidence that past designs have attempted to provide too sophisticated levels of service which cannot be sustained by the agencies or users (Albinson 1996, pers. comm.). Where adjustable controls (movable weirs, adjustable sluice gates) have been turned-over to water user control the, demand for transparent operations frequently results in the structures being ‘fixed’ so as to give approximate proportional distribution. When variations in supply are required, users generally find managing time allocations simpler and more transparent than adjustments of flow rates by changing structure settings.
Within the constraints imposed by water rights, the system infrastructure and management must be well matched to achieve the desired water allocation and delivery service. Flexible systems are appropriate only where there is adequate management capacity with sufficient resources. Bearing in mind the management capacity in many systems, it may be more beneficial to adopt less flexible, but less complex infrastructure.
Water delivery service
The quality of water delivery service is determined by the characteristics of infrastructure and management intensity. Levels of service can be described in terms of reliability and adequacy of water supply. For productive agriculture, water supply to crops must be timely, reliable and adequate. Given the varying profile of crop demands and frequent mismatches between the timing of water availability and crop demands, meeting irrigation requirements in such a way to allow maximum production is a challenging task. Well crafted institutional rules can often enhance the level of service afforded by infrastructure design. For example, even with a supply-based system that uses rigid infrastructure, users may adjust time of delivery, or may trade turns to provide for more flexibility. The ultimate flexibility of water service is not a function of infrastructure alone, rather the interaction between infrastructure and management.
A purely demand based system where users could turn on and off water as per their demand would represent a high level of service. In contrast, the protective irrigation systems of N. India and Pakistan make no attempt to match water supplies to full crop water demands. Rather the objective is to provide an equitable distribution of available water to secure a stable base for agriculture (Jurriens et al., 1996). In certain settings, these systems have largely proven to be sustainable and productive, although in recent years increasing exploitation of groundwater resources through farmer-owned and operated pump-sets has introduced a large degree of flexibility in water supplies not present in the management and infrastructure design. This evolution may be seen as a modernization of the systems brought about in part by the adoption of modern varieties of crops which are less tolerant to below optimum water supplies.
Performance
Performance related to outputs such as productivity and economic returns are a function of the quality of water delivery service. If the designed level of water delivery service is not met, this may be due to a mismatch between management capacity, infrastructure, and water rights. If the level of water delivery service is restricting output performance, modernization could be called for to upgrade water delivery service. If the designed level of service is being met, and outputs are not up to a desired level, there may be reasons external to managing irrigation water leading to poor performance such as below optimum use of inputs or lack of proper price incentives.
DESIGNING MODERNIZATION WITH INSTITUTIONAL CHANGE
Ideally, a modernization programme combined with management transfer would be initiated by the water users of an irrigation system. Users would feel that taking over more of the system would be beneficial in terms of the amount of additional control of water resources derived as a result of transfer. Ideally, users would be willing to finance all or part of the cost of modernization to meet enhanced objectives of their communities. This type of management transfer has occurred in Colombia (Vermillion and Garces-Restrepo, 1996) and Washington State (Svendsen and Vermillion, 1996), although infrastructure modernization was not part of the transfer process.
In fact, management transfer is most often not user demand driven, rather it is driven by the needs of government to reduce expenditures on operation and maintenance, or by the assumption that local management will lead to improved irrigation performance. For example, turnover in Mexico followed this approach (Palacio-Velez, 1995). To entice and assist users to take more responsibility, rehabilitation and possibly infrastructure modernization are added to management transfer programmes. In either case, whether driven by demand, or driven by other reasons, a logical sequence of activities can be identified to integrate considerations of water rights, management and institutions, and infrastructure. These considerations are taken from the perspective of one providing technical assistance to the local users.
Understanding the basic features of the system
Before being able to provide assistance in a modernization process, it is essential to understand the basic features of the system, the actual objectives of the water users, present utilization of water, and the water rights of the system. “De-jure” operational rules for many systems no longer apply and an acceptance that designs for modernization will have to address “de facto” procedures which have evolved in response to local situation.
Consultation with user representatives
Management transfer implies more responsibilities for users. It is has often been observed that users are not involved in design of irrigation systems, thus leading to ultimate failure of projects. In cases where local organizations are present, they must be consulted. If users are not represented, a first step is to identify or work with users to create a representative group of farmers that can initially be consulted on design issues.
Initial organizational design
Where farmers are not initially organized, a task is to create a sustainable organization for managing water resources. Implementing large scale rehabilitation or infrastructure modernization in conjunction with a newly-formed organization can be a delicate process. A main purpose of a local organization for irrigation is to provide water delivery service. Attention from this can easily be diverted to construction and contracting activities. When dealing with newly formed organizations, it is generally best to proceed slowly, and let the organization learn how to manage water delivery service first. After this is accomplished, a more stable organization may be in place better able to identify their needs. This philosophy is often at odds with time-bound modernization projects (Brewer et al., 1992).
Consideration of expected individual water rights and level of service
Once the organization has been established, and preferably have had experience operating the system then this is the appropriate time to determine the level of service desired. Management and infrastructure tradeoffs must be considered given the objectives of the users, and the costs of alternative arrangements.
Design of infrastructure
Initial considerations are the level of water delivery service that structures can provide, management, and cost considerations. Users’ may not be willing to pay for the infrastructure required to meet their initial service demands. Later considerations are the layout, specific types of structures and their locations. The design process requires an iterative approach due to the interrelationship between elements.
Adaptation to new system
Time is required for concerned managing institutions, including both the local organization and the irrigation agency to adapt to a modernized system. After infrastructure is in place, institutions must adapt their rules and procedures for operating and maintaining them to yield better performance. A successful adaptation would be characterized by adoption and enforcement of rules that allow for better performance. A non-successful adaptation is characterized by a breakdown in organizational rules accompanied by a breakdown in infrastructure.
MANAGEMENT TRANSFER AT KHAGERI IRRIGATION SYSTEM, NEPAL
To illustrate the points discussed above, a case study of the Khageri Irrigation System located in Nepal is presented. Management transfer in Nepal takes two forms: joint management and turnover. Joint management is where the irrigation agency is in charge of O&M up to a certain point in the irrigation system after which it turns over water and responsibility for managing water to local organizations. Turnover occurs when a local organization takes charge of O&M of the entire irrigation system. The irrigation policy calls (HMG/Nepal, 1992) for turnover of agency managed irrigation systems of less than 500 ha in the hills and 2 000 ha in the terai (plains) to local user organizations. Joint management, or if possible, turnover arrangements are to be made for systems larger than these sizes. Khageri Irrigation System, serving 4 000 ha in the terai was one of the first systems brought under this management transfer programme
Construction of the Khageri Irrigation System, funded through the government, was completed in 1965. The system has one main canal of 22.5 km in length serving 9 branch canals and 4 minor canals. The main source of water is the Khageri river where a permanent barrage structure diverts up to the design discharge of 8 m3/s. The main canal passes through 9 km of forest land before entering the command area. River flow varies considerably throughout a year and no major storage is available. The system provides supplemental water for rice during the monsoon season as well as water for winter wheat and a limited area under early paddy.
FIGURE 4. Layout of the Khageri Irrigation System
Until the start of the management transfer programme, responsibility for operation and maintenance of the system fell with HMG/Nepal government. The joint management programme was initiated in 1992. At that time, there was no representative body of users and no local organization for operation and maintenance of the irrigation system. A single water user association (WUA) was initiated for the system consisting of a representative general assembly to approve key policy decisions, an executive committee involved in day to day decision making, and branch committees for each of the branch and minor canals. In January 1993, the constitution of the WUA was ratified by the General Assembly and the organization was formally registered.
A first task of the WUA was to develop its rules for water allocation, operation, fee collection, labour mobilization, and maintenance (Research and Training Branch, 1993). The WUA adopted the concept of a share (Wilkins-Wells et al., 1995) which links the allocation of water to payment in cash, kind, or labour for services. Shares were allocated in proportion to land holding. Annual irrigation service payments are levied at a fixed rate per share. Water allocations are also proportional to share holding.
The WUA devised an allocation procedure where 120 000 shares were made available, one share corresponding to one khatta, the local land area measurement (1 khatta = 1/30 ha). One share entitles a user to 1/120 000 of the usable supply entering into the system. At full supply, 7 m3/s enters the command area of which 6 m3/s is estimated as usable after subtracting seepage losses (Kalu et al., 1993). Water allocations per share is reduced in proportion to the reduction in inflow into the system.
A table devised by the newly formed WUA, translated from Nepali, is shown in Table 1. The table has a statement about the allocation principle and the delivery service required. At full flow, two rotational groups are specified with deliveries to branches based on the number of shares on the branch. Branch committees then decide how to distribute shares of water to farmers. If the water is less than full supply, then the allocated amount reduces in proportion to the reduction in discharge. If the total discharge at the head of the main canal falls below 5 000 litres per second (lps), then a further rotation within each section will be called.
TABLE 1. Water allocation rules and distribution procedure developed by the Khageri WUA
Khageri Irrigation System; WUA, Shivanagar, Chitwan
Water Delivery Schedule
|
Pro Rated Flow: 6000 l/s |
Total Land Irrigated: 6000 Bigha |
|
|
|
Total Shares to be Distributed: 120,000 |
(1 Katha = 1 Share) |
|
Sr. No. |
Section Rotation I |
Section Rotation II |
||||||
|
Sr. No. |
Branch/ Minors getting turn for water |
Pro Rated 100% Share Value Quantity/Share lps |
Total Number of Shares |
Pro Rated 100% Section Discharge lps |
Branch/Minors getting turn for water |
Pro Rate 100% Share Value Quantity/Share |
Total Number of Shares |
Pro Rated 100% Section Discharge lps |
|
1 |
Branch No.1 |
0.1 |
7,140 |
714 |
Branch No.0 |
0.1 |
870 |
87 |
|
2 |
Branch No.3 |
0.1 |
17,790 |
1,779 |
Branch No.2 |
0.1 |
15,180 |
1,518 |
|
3 |
Branch No.4 |
0.1 |
6,840 |
684 |
Branch No.6 |
0.1 |
15,900 |
1,590 |
|
4 |
Branch No.5 |
0.1 |
8,850 |
885 |
Branch No.8 |
0.1 |
8,640 |
864 |
|
5
|
Branch No.6 |
0.1 |
13,260 |
1,326 |
Minor No.1 |
0.1 |
6,540 |
654 |
|
West |
|
|
|
Minor No.1 |
0.1 |
7,710 |
771 |
|
|
6
|
Branch No.7 |
0.1 |
6,450 |
645 |
Minor No.3 |
0.1 |
3,000 |
300 |
|
|
|
|
|
Minor No.4 |
0.1 |
1,830 |
183 |
|
|
|
Total |
60,330 |
6,033 |
|
Total |
59,670 |
5,967 |
|
1. Before each section rotation, water measurement shall be carried out in the head reach of the system. The quantity of water for each share shall comply with the variations in pro-rated value of flow in the source.
2. If the discharge in the source becomes less than 5000 litres per second then section rotation shall be imposed and every branch shall receive water according to the shares allocated to its branch.
The existing structures in the system consist of gated overflow weirs delivering water from the main to the branch canals. The width of the weirs is in proportion to the original, designed command area of each branch. In 1993, the actual flow delivered was found not to be in proportion to the existing command area due to varying hydraulic conditions at the offtake structure, alterations of the structure such as lowering the weir sill, and a change in actual command area from the original design command area (Kalu et al., 1993). The outlet structures were calibrated such that flow could be regulated to deliver water in proportion to the land area below the outlet.
Within branch canals turnouts to tertiaries or farms were designed as gated pipe outlets. Many of the gates were removed over time leading a condition of over-supply to head-enders and less supply to tail-enders. The new organizations at the branch level made rules to enforce rotational flow of water, by regulation of pipes.
The Department of Irrigation (DOI) has been supportive of the process and took the lead role in implementing management transfer process. A major function of the DOI has been the construction and rehabilitation of irrigation systems. The DOI has recognized the need to be a more service based organization and has made progress through the establishment of their Irrigation Management Division which supplies training, applied research, monitoring, and advise on system management. Policies and regulations have been evolving which support local organizations and their right to water.
At the time of writing, management of branch canals is done by branch committees, and management of main canals jointly by the WUA and the DOI. This institutional change of management transfer and development and enforcement of rules represents modernization of the system. During the period 1992 to 1994, the average net benefit to farmers increased from $190 to $260 per ha (Pradhan et al., 1995) due to better water delivery service. There were increases in area under rice and wheat, greater productivity from wheat, and more production of oilseeds and pulses.
The WUA has had nearly four years of managing the system jointly with the Department of Irrigation. Through a joint HMG/Nepal, Asian Development Bank, USAID Irrigation Management Transfer Project, funds for infrastructure improvement are being provided under cost sharing arrangements.
Given this set of conditions, what kind of infrastructure modernization is required? There are some key infrastructure, management, and cost tradeoffs that must be carefully considered by the WUA. Performing minor repairs to the existing outlet structures would be cheapest, but gates must be carefully adjusted to deliver the amount of water called for by the allocation rules. Alternatively, the outlet structures could be remodelled to allow for proportional distribution of the water supply throughout the main system with provision for opening and closing branch outlets. In this case the management intensity required for operation would be less, but the initial costs would be higher.
Provision of more regulating and control structures may give the opportunity to produce more grain crops and for shifting to other higher valued crops. The initial plus the annual costs of maintaining and operating these structures would not have been warranted given that it is uncertain that new crops would be adopted. Additionally, users are grappling with already difficult problems of fee collection and determining who and how gates should be operated.
Ultimately the choice was to make minor repairs to the outlet structures, and focus on lining of portions of the canal system with heavy seepage losses. Farmers felt that supply for water was the most limiting factor. Organizational rules allowed for additional flexibility within the system. For example, shares within branches could be traded. Frequent discussions were held within the executive management committee of the WUA to adapt operational procedures to better match user demands and retain as much equity as possible. Also, in many places throughout the command area there is potential to pump from shallow groundwater or surface drainage water. Pumping allows much more flexibility in terms of duration, frequency, and volume of water delivered and allows for higher valued crops and higher yields on grain crops.
CONCLUSIONS
The process of management transfer requires institutional changes in that local organizations take more responsibility for irrigation management, and irrigation agencies concentrate their effort on a smaller set of O&M activities and may change to a role of support-provider. Management transfer in itself can be considered a form of modernization in that it is a means of attaining enhanced system objectives.
Management transfer is often accompanied with infrastructure modernization. In this case, both infrastructure and institutional changes are required. Three basic elements: water rights, infrastructure, and management institutions must be integrated and balanced in the design of both infrastructure and institutions. The combination of management and infrastructure must match with the desired level of water delivery service. Adequate institutional capacity of both the irrigation agency and the local organization must be in place to manage the designed infrastructure. The arguments presented here together with the case study supports the need to promote institutional development before infrastructural modernization efforts. A local organization, experienced with operation and maintenance, will be better able to identify and implement infrastructure modernization.
ACKNOWLEDGEMENTS
The information about Khageri is based on experience gained through the joint HMG/Nepal Department of Irrigation and the USAID/Nepal Irrigation Management Project and their support is acknowledged and appreciated.
REFERENCES
Brewer, J.D., Sakthivadivel, R.and Wijayaratna, C.M. 1992. Achieving cost-effective rehabilitation and modernization of irrigation systems: Research results from Sri Lanka. In: Advancements in IIMI’s Research 1992. A selection of papers presented at the Internal Program Review, Colombo, IIMI.
Freeman, D. 1989. Local Organizations for Social Development: Concepts and Cases of Irrigation Organization. Boulder, CO: Westview Press.
HMG/Nepal, Ministry of Water Resources, 1992. Irrigation Policy 1992.
Jurriens, M., Mollinga, P.P. and Wester,P. 1996. Scarcity by Design. Protective Irrigation in India and Pakistan. Liquid Gold Paper 1. International Institute for Land Reclamation and Improvement (ILRI), Wageningen, The Netherlands.
Kalu, I.L., Manandhar, P. Regmi, S. and Molden, D.J. 1993. Khageri Irrigation System Hydraulic Operation Report. Research and Training Branch and System Management Branch, HMG/Nepal Department of Irrigation, Kathmandu, Nepal.
Maas, A. and Anderson, R.L. 1978...and the Desert Shall Rejoice: Conflict, Growth and Justice in Arid Environments. Malabar, FL: Robert E Krieger Publishing, 1986 edition.
Malhotra, S.P. 1982. The Warabandi and Its Infrastructure. Central Board of Irrigation and Power, Publication 157, New Delhi.
Merriam, J.L. 1992. Flexible water supply systems facilitated by low pressure semi-closed and closed pipeline systems. In: Advances in Planning, Design and Management of Irrigation Systems as Related to Sustainable Land Use. J. Feyen, E. Mwendera, and M. Badji (eds.). Proceedings of an International Conference organized by the Center for Irrigation Engineering of the Katholieke University Leuven in cooperation with the European Committee for Water Resources Management, Leuven, Belgium, 14-17 September, 1992.
Ostrom, E. 1992. Crafting Institutions for Self-Governing Irrigation Systems. San Francisco, CA: Institute for Contemporary Studies Press.
Palacio-Velez, E. 1995. Performance of water users’ associations in the operation and maintenance of irrigation districts in Mexico. In: Irrigation Management Transfer: S.H. Johnson, D.L. Vermillion and J.A. Sagardoy (eds.). Selected papers from the International Conference on Irrigation Management Transfer, Wuhan, China, 20-24 September, 1994. Water Report 5. Rome: IIMI and FAO.
Perry, C.J. 1995. Determinants of function and dysfunction in irrigation performance and applications for performance improvement. Water Resources Development 11(11):11-24 (Special Issue: Irrigation Management: Definition, Analysis and Impact).
Plusquellec, H., Burt, C. and Wolter, H.W. 1994. Modern water control in irrigation: concepts, issues and applications. Technical Paper 246. World Bank, Washington, D.C.
Pradhan, N.C., Sharma, V., Upadhyaya, S. and Joshi, S. 1995. Benefit Monitoring and Impact Evaluation of West Gandak and Khageri Irrigation Systems under the Joint Management Program. Research and Technology Development Branch, HMG/Nepal Department of Irrigation.
Ramnarayan S. 1996. Summaries of Field Sites Studied under IIMI/IIMA study on irrigation management transfer in India (Manuscript).
Replogle, J.A., Merriam, J.L., Swarner, L.R. and Phelan, J.T. 1983. Farm water delivery systems. In: Design and Operation of Farm Irrigation Systems. M.E. Jensen (ed.). ASAE Monograph Series No. 3. St. Joseph, Michigan, USA: American Society of Agricultural Engineers.
Research and Training Branch, 1993. Training Report: Operation and Maintenance and Share System Development in Khageri Irrigation System. HMG/Nepal, Department of Irrigation, Irrigation Management Division.
Shannon, L. 1992. Planning and management of irrigation systems in developing countries. Agricultural Water Management 22(1 and 2).
Svendsen, M. and Vermillion, D.L. 1996. Results of irrigation management transfer in the Columbia Basin Project, USA. In: The Privatization and Self-management of Irrigation. Final Report. D. Vermillion (ed.). International Irrigation Management Institute, Colombo, Sri Lanka.
Vermillion, D. (ed.). 1996. The Privatization and Self-management of Irrigation. Final Report. International Irrigation Management Institute, Colombo, Sri Lanka.
Vermillion, D.L. and Garces-Restrepo, C. 1996. Results of management turnover in two irrigation districts of Colombia. In: The Privatization and Self-management of Irrigation. Final Report. D. Vermillion (ed.). International Irrigation Management Institute, Colombo, Sri Lanka.
Wilkins-Wells, J., Molden, D.J., Pradhan, P. and Rajbhandari, S.P. 1995. Developing share systems for sustainable water users’ associations in Nepal. In: Irrigation Management Transfer. S.H. Johnson, D.L. Vermillion and J.A. Sagardoy (eds.). Selected papers from the International Conference on Irrigation Management Transfer, Wuhan, China, 20-24 September, 1994. Water Report 5. Rome: IIMI and FAO.
Yoder, R. 1994. Locally managed irrigation systems: essential tasks and implications for assistance, management transfer, and turnover programs. IIMI Monograph No. 3. Colombo: IIMI.
Hans W. Wolter
Chief, Water Resources, Development and Management Service,
Food and Agricultural Organization of the United Nations
(FAO), Rome,
Charles M. Burt
Director, Irrigation Training and Research Center,
California Polytechnic State University,
San Luis Obispo, California, USA
INTRODUCTION
This paper discusses concepts of modernization of irrigation systems. Modernization is understood as a process of change from supply oriented to service oriented irrigation. The process involves institutional, organizational and technological changes. Modernization in that sense is a response to current trends from protective to productive irrigation. The paper discusses strategic choices with emphasis on technological options and presents an outline for a plan of action on modernization. Two appendixes, one on technological options and another on the assessment of modernization needs are attached. In preparing this paper the authors drew heavily on experience gained during their work in Mexico. It is hoped that the lessons learned will also be applicable in the Asian context.
FROM PROTECTIVE TO PRODUCTIVE IRRIGATION
Irrigation schemes in large parts of India and Pakistan have been built on the design logic of “protective irrigation”. The idea is to reach as many farmers as possible to protect them against crop failure and famine which would occur without irrigation in regions with erratic monsoon rainfall. Water available in rivers or reservoirs is spread thinly over a large area. The amount of water a farmer is entitled to receive is insufficient to cover the full water requirements on all his land for an average rainfall year. Protective irrigation systems are based on scarcity by design. While there are different management principles in India (Warabandi, Shejpali, crop sanctioning) they all involve the problem of rationing scarce water in a supply based system where the objectives of individual farmers differ from those of the scheme management. Typical irrigation systems have very few control structures. Canals are run at full supply level or have to be closed, in order to achieve equal distribution of water to ungated chak outlets and to avoid deposition of silt. (The term Chak is used in Northern India to describe the smallest hydraulic unit above field level. A chak supplies water to about 30 to 50 farm outlets.) Construction costs per unit area of these rather unsophisticated irrigation systems are low but maintenance costs are high in comparison to the low level of irrigation service.
Protective irrigation systems have worked well through most of the past 100 years. They have been able to mitigate the effects of severe droughts and are still the backbone of the agricultural economies in Pakistan and India. 90% of the agricultural production in Pakistan comes from irrigated land, the respective figure for India is 65 %.
However, it is now becoming apparent that the design logic of these systems may no longer be adequate for modern productive irrigated agriculture in an increasingly global economy which is driven by market forces. The most pressing problems include: low efficiency in water distribution and use, unreliable water delivery, widespread vandalism of structures, poor maintenance, waterlogging and salinity, in-sufficient cost recovery. Farmers could cope with these ineffi-ciencies and make full use of advances of the green revolution in cases were they had access to fresh groundwater. The phenomenal spread of private wells in canal irrigated areas is a clear sign of the inadequacy of canal irrigation. However in areas which are less fortunate, because of saline or insufficient groundwater, yields are stagnating or declining. Successful irrigation systems feature high yields, service oriented irrigation management and financial autonomy. They may be described as productive irrigation. The main differences between protective and productive irrigation are given in Table 1.
TABLE 1
Differences between productive and protective irrigation
|
|
PROTECTIVE |
PRODUCTIVE |
|
HYDRAULIC |
||
|
Water duty |
Low |
High |
|
Canal supplies |
Constant flow |
Varying flow |
|
Control |
Supply oriented |
Demand oriented |
|
AGRICULTURE |
||
|
Intensity |
Low |
High |
|
Seasons |
One to two |
Two to three |
|
Crops |
Low water demanding |
High water demand |
|
MANAGEMENT |
||
|
Water |
Planned scarcity |
Planned sufficiency |
|
Cropping pattern |
Prescribed/controlled |
Free |
|
SOCIO-ECONOMIC |
||
|
Objectives |
Poverty alleviation |
Agric. growth |
|
Benefits |
Spread |
Concentrated |
|
Optimization of |
Unit of water |
Unit of land |
|
Labour |
Family labour |
Hired labour |
|
Orientation |
Subsistence |
Market |
The time has come to reconsider the strategic choice for irrigation development in Asia in the context of recent economic trends. Perhaps it is necessary to make a deliberate shift from protective to productive irrigation. However, there should be no illusion that such a shift would involve difficult decision. What are the options?
1. Business as usual. This, probably, is the least preferred option, although it may be politically the easiest option. The risk is that the problems mentioned above will continue to increase, in particular, head-end/tail-end conflicts, system deterioration, low cost recovery and low productivity.When considering the options it must be realized that in reality irrigation schemes are already shrinking in an unplanned manner. Head-enders usually take more water than their share and tail-enders receive little if anything. Further, it is debatable whether state interventions can successfully stem strong economic and social trends. This paper argues that a strategy of modernization, building on current economic trends, is the adequate response to the present economic and social environment.2. Enforcement of the protective irrigation concept. The option implies: strict control of water allocations, maintaining full supply flow in main canals, and installing fixed proportional dividers. The concept requires strong irrigation authorities who will remain dependent on state subsidies. Levels of irrigation service and agricultural productivity will remain low except where canal water is supplemented by private wells.
3. Modernization, through a combined strategy of institutional, managerial and technological change with the objective to change from a supply to service oriented mode of operation.
VISION OF MODERN IRRIGATION
Appropriate modernization is a process which incorporates new design procedures and new equipment with a vision of future operations. Modern design is the result of a thought process. Configuration and the physical components are selected in the light of a well defined and appropriate operational plan. Advanced concepts of hydraulic engineering, irrigation engineering, agronomy and social science should be used to arrive at the most simple and workable solution. A modern irrigation design is not primarily defined by specific hardware components and physical configurations, but will have all or some of the following characteristics:
There are two major hurdles for the implementation of proper modernization processes. First, a full understanding of the above principles is needed by all participants in the modernization process. Second, some additional funding for design, construction, and maintenance of the new hardware and introduction of new operation procedures is required. As explained in the paper by Plusquellec, these funds amount to about 5 percent of the construction costs.
Operational level
In large irrigation schemes there are typically four or five levels of irrigation operation to consider:
The purpose of each of the operational service levels (dam, major, minor, chak) in the water delivery system must be to provide the appropriate degree of service to the next lower level. In turn, each lower receiving level (farm, WUA, ID, dam) will compensate the next upper level for the services received, thus creating an autonomous system. This concept of service may be the most difficult hurdle to cross in many modernization programmes. However, the service concept, or “client-centred” approach, must be clearly understood and accepted by personnel at all levels in an irrigation scheme in order for an irrigation project to achieve its maximum potential.
Objectives of irrigation scheme operation
The operational objectives may differ from one level to another. There should be a consensus that the primary objective of scheme operation is to enable farmers to improve the quality and quantity of crop yields, while ensuring or improving economical and environmental sustainability. Consensus is also required on the following:
1. The service concept should be adopted throughout the system. This will require improved flow measurement, water level control, communications, etc. throughout all levels of the water delivery network down to the individual turnout.Present vs. future operations2. A general consensus should be reached that a major cause of the low performance of irrigation projects is low level of irrigation service received by the farmers and the resulting low application efficiencies on individual fields. Therefore, the benefits of a modernization programme will only be realized if there is an improvement at farm level in reliability, equity, and flexibility of water delivery. The question is not whether improved reliability, equity, and flexibility is desirable - the question is how exactly can it be obtained.
3. The question of how much flexibility should be provided to individual farms, should be decided by the members of water user associations themselves. In essence, the water user associations must decide what level of service should be extended down to the individual field level in their particular cases. However, they must also face the financial consequences of their decision.
Modernization implies change from some present status to an improved status in the future. A vision of the future must be derived from the present situation. Because the purpose of an irrigation project is to enhance on-farm production and profitability, any analysis of the operation of an irrigation project must begin with the farm level. Table 2 presents a comparison of present and future on-farm irrigation.
Table 3 describes operations which are under the control of the water user associations. It addresses the chak and the minor level, although from the standpoint of engineering and control concepts the two levels are distinct. The importance of modernization at chak or watercourse level is great. Therefore, Table 3 serves as a reminder that funds must be allocated for those needs, and the concept of service in the larger canals must include the vision of the eventual, future use of water on the individual farms.
Tables 3 and 4 indicate that future agricultural development and on-farm irrigation technology will require profound changes in the present operation of all service levels. In some cases, the future needs are completely incompatible with present designs. This is frequently the case with the final distribution system consisting of small, poorly maintained ditches between the chak outlet and the individual farms. Low pressure pipelines, as discussed later, present a good engineering solution at that level.
Suggestions about providing more flexibility in deliveries from the secondary and main canals are usually greeted by initial scepticism by the present operators. This is because they are not aware of engineering water control options whereas they are keenly aware of the tremendous difficulties of just maintaining present operation with an inflexible schedule. Because the wholehearted support of the present operators is so important for the success of any modernization programme, the list of proposed actions in the next section includes a significant component for consensus building and training.
TABLE 2
Present vs. Future Operations: On-Farm Level
|
Present Operation |
Future Operation |
Necessary Changes |
|
Poorly designed and main-tained traditional surface irrigation
systems (basin) in many areas, lack of proper land grading. |
Well designed and maintained on-farm irrigation systems. Mix
of modern level basin, furrow, sprinkler, and drip. The irrigation system
designs are tailored to meet individual field crop, soil, topography, economic,
and labour requirements. |
· Capability to supply each farm
below a chak outlet at request with a constant flow rate. |
|
Irrigation frequency and rate are scheduled by tradition or on
instruction from ID (warabandi, shejpali) |
Irrigation frequency, rate and duration customized to match
more closely irrigation technology, soil, weather, crop, and labour schedules.
|
· More flexible and reliable
water deliveries. On-farm storage for drip and sprinkler systems. |
|
Insufficient awareness of correct agronomic practices and
irrigation inputs. |
Improved awareness of necessary inputs and agricultural
practices. |
· Education about on-farm
irrigation, agronomic inputs, soil/water/plant relationships. |
|
Annual water consumption per plot is unknown to farmer, or not
understood in terms of volume. |
Water allocations will be done on a volumetric basis, with
annual or seasonal limitations. |
· Ability to measure flow rate
and volumes delivered to individual plots. |
|
Water losses are only understood in terms of surface runoff.
The magnitude of deep percolation losses is not understood. |
Water losses will be understood to include both surface and
deep percolation losses. |
· Improved rules for water
distribution. |
As an example an outline of a plan of action is provided in the text box. Action items within each of the categories are listed in chronological order of implementation, although actions in each category can begin simultaneously. These and additional items are discussed in more detail in this chapter.
Policy actions
Coordinator. It is recommended that the ID should nominate a special full-time coordinator who has the staff, knowledge, and budget to facilitate modernization efforts. This office will serve as the “wheel hub” for the many efforts related to training, development of new design guides, diagnostic research which will span the engineering, construction, and planning divisions of the ID. The coordinator will also be able to enhance the effectiveness of outside agencies such as research institutions, the universities, and consultants.
TABLE 3
Present vs. future operations: service level between the farm and chak outlet or minor canal
|
Present Operation |
Future Operation |
Action Needed |
|
Rotation schedule |
Arranged schedule |
· Improved
communications |
|
Inequitable water delivery to farm-turnouts. Tail-ender do not
get equitable supplies |
Equitable water delivery |
· Improved final distribution
system |
|
Water distribution system (open ditches) is difficult to
access and maintain. Large seepage losses. |
Simplified maintenance and operation. Reduced seepage losses.
|
· Lining of canals or
installation of pipelines. |
|
Water delivery only possible to one farm at a time. |
Water deliveries to more than one farm at a time or at least
with more flexibility. |
· New design criteria for
flexible service. |
|
Insufficient capacity for flexible deliveries. |
Larger capacities, so that multiple farms can be serviced
simultaneously. |
· Different types of water
delivery control and conveyance between the canal turnout and the farm. If
possible interim storage reservoirs. |
|
Lag time between water delivered at the canal turnout and the
water reaching the field. |
Reduced lag time. |
· Piped distribution, or
|
|
Flow rates are only measured at the canal turnout. |
Multiple deliveries downstream of the turnout. Flow is
controlled and measured at each farm during simultaneous deliveries. |
· New delivery control and
conveyance systems. Development of portable, totalizing flow measurement devices
for canals and pipelines. |
|
Frequent spills. If a farmer shuts off the water to his plot,
the water must be switched to another farmer. |
Farmers may be able irrigate independently. |
· Remote monitoring, automation,
piped distribution. Options depend upon location and economics. |
Present vs. future operations: service level between the minor and primary canals
|
Present Operations |
Future Operations |
Action Needed |
|
Minor canals: Typically only one change of flow- rate at the
head of the canal every 1-7 days. |
Multiple changes of flow-rate per day at the head of each
secondary canal. |
This means that simple rehabilitation such as replacement of
broken gates is insufficient; the future operation will be completely different
from the present. It will require a better understanding of the operational
relationship of structures in primary and secondary canals. |
|
Primary canals: Typically only one change of flow rate at the
head of the canal every 3-7 days. |
Multiple changes of flow rate per day. |
|
|
Silt and aquatic weed growth reduces flow capacity. |
Reduced blockage of flow. |
· Basic maintenance and
rehabilitation, with improved equipment and access to canals. |
|
Proposed Action Plan 1. Policy Actions a. Appoint a national coordinator of modernization activities.2. Training a. Provide refreshing training for key ID staff.3. Planning and Implementation a. Develop/publish new official design procedures for field engineers. |
Consensus building. It was noted earlier that effective modernization requires a consensus by decision-makers at all levels regarding the vision for the future, the objectives, the most suitable technical solutions, and the proper plan of action. The major points that require a broad consensus are “Recommended Strategic Choices” and the “Proposed Action Plan”.
Information Transfer. Once an initial consensus has been reached at the national or state level, regional meetings must be held to explain the intent, reasons for the decisions, and implications on present maintenance and rehabilitation work. Participants in each regional meeting including water user associations and local ID personnel, should then discuss the guidelines and arrive at a consensus on a local variation of the guidelines.
Review Panels. Modernization will involve many unique situations and requirements, yet it is important to be able to provide some form of centralized and effective technical input to the proposed changes. A national panel of experts should be formed to provide review and insight to the modernization plans for individual projects. The panel should not be used to provide detailed engineering or economic review of each project. Rather, this panel should be used to suggest improvements and new options for projects. The panel's expertise should ideally be used in the early stages of project modernization, after a diagnosis has been made of project conditions and needs. In order for this review panel to be effective, it must provide a timely response (less than 1 month) to requests from the individual projects. Representatives from the panel should attempt to physically visit the projects to evaluate the action plans and provide technical advice and insight.
Training
Training is a key element to wise investment. In some cases, the training is necessary to understand the intricate details of how a particular device must be designed. More importantly, however, the training can be used to present a balanced view of the general options which are available to solve a particular problem. All training should be conducted in the context of the broader purpose of modernization - to improve on-farm production and profitability, and to protect or enhance the environment.
Training of key personnel
The changing functions of ID personnel require a larger knowledge basis. A top priority is that the key personnel be familiar with the recent advances in on-farm irrigation. That familiarity will improve their vision of future demands on the water delivery system. Secondly, they should increase their awareness of existing water distribution control possibilities. Undoubtedly, there is already considerable expertise within ID for each of the technologies listed below. However, proposed training will ensure that a core group is aware of the latest technological developments in the country and elsewhere.
It is recommended that a core group of professional (up to 30 persons) receive a common base of training and awareness. Ideally this training will occur with all participants in a single group. This will ensure that all of the trainers, regardless of their speciality, share a common vision of the purpose and direction of the modernization efforts. Although it is expensive and difficult to bring such a large group together for the approximately 3 weeks which are needed, the long-term benefits will justify this initial investment. Fast and cohesive advances in modernization will only occur if individuals at all levels share the same vision and basic knowledge of options. In addition, if a single group studies together, it will be easier and less expensive to organize the special training needed than if several groups are formed.
The following topics are considered to be the most urgently needed for the core group at the initial stages:
1. Water delivery modernization options - general. This will include general concepts of canal and pipeline control and the implications of adopting various hardware and management strategies in terms of economics, reliability, risk, and flexibility.After the group training, individual professionals receive additional training on the specific topics of their responsibility. The recommended speciality topics for this first stage are:2. Improved on-farm irrigation methods - general. This session will ensure that participants are aware of practical options for future improvement of on-farm irrigation methods. It will cover on-farm pipeline distribution systems, irrigation scheduling, and modern irrigation methods such as sprinkler, drip, and improved furrow and border strip.
1. Water Delivery ModernizationWith most of the topics noted above there should be an identification of brand names, existing users, costs, suppliers, and reputable consultants/engineers. The ultimate users of the information (the water user organizations and ID field engineers) need to know how to access the equipment and technologies.a. Canal capacity, freeboard, and head requirements for flexible deliveries.2. Canal maintenance, to include topics such as:b. Buffer reservoir design and location strategies for main canals.
c. Communication equipment.
d. Remote monitoring and control software and equipment.
e. Options for automatic flow control at the head of canals, including both the design of the flow measurement structure (e.g., Replogle Flume or distributor modules) and control software.
f. Low pressure pipeline distribution systems, to include
- Air vent and pressure relief considerationsg. Design specifications for the following types of gates:
- Pipeline materials
- Construction techniques.
- Turnout designs- Electrically automated radial gates.h. Revised designs for the chak turnout, to include detailed construction specifications of options for the system which includes the canal cross regulator, the flow control, and flow measurement.
- Electrically automated overshot gates
- AMIL, AVIS, and AVIO gates
- Long crested weirs
- Combination gates.a. Sterile grass carps for elimination of aquatic growth in perennial waterways.b. Chaining for the removal of weeds
c. Herbicide usage, with special consideration to toxic effects on humans and animals who come in contact with the water.
d. Specialized equipment for annual shaping of ditch banks and removal of silt and weeds from the bottom of ditches.
e. De-silting basins.
Long-term training needs
Long term training must be organized to distribute the knowledge gained by the core group in the immediate training sessions. The exact details and topics of such training will be developed with time, but such training will be aimed at these principal groups:
1. The engineers, designers, and technicians within ID and the water user associations.The training must be practical, and always include a view of the overall vision of modernization, plus provide insights to the economic, management, sustainability, and environmental aspects of the factors being discussed. Training should be conducted by persons who have both academic and field experience in the subject matter. Training topics, session durations, and material depth must be customized to match regional and individual participant needs. Care must be taken to avoid obvious errors such as discussing computer based irrigation scheduling with farmers who do not have good flexibility or reliability in water delivery to individual fields.
2. Managers within ID and the water user associations.
3. Consultants who will provide design assistance.
4. Persons from the banking and financial industries.
5. University and extension personnel.
6. Farmers
Training for managers and technical staff of water user associations
Specialized training materials and sessions should be available for staff of the water user associations. Since these people hold the purse strings to future investments, and since their decisions have such a tremendous impact on the final outcome of policy decisions, it is important that they have an understanding of some basic principles of hydraulics and water control, as well as knowledge of some maintenance options. Specific topics of interest for this audience include:
1. Basic maintenanceIt is important to note that the audience will be largely composed of persons with limited formal education. More extensive training, as described in the previous section, could be made available to the technical staff of the water user associations.
2. Basic principles of upstream control (manual and automatic)
3. Basic hydraulicsa. Effects of different roughness factors (and the actual importance of various levels of canal cleaning)b. Causes of deep percolation as influenced by on-farm irrigation.
c. Overshot vs. flow gate hydraulics
d. The nature of unsteady flow.
e. Flow rate and volumetric measurement and control.
Planning
New design manuals
Many field engineers in Asian countries are using design manuals which are based on outdated design concepts which treat irrigation water control as a steady flow problem. The real need in modernization is something different - it is to solve the problems of unsteady flow conditions in canals and pipelines. The field engineers need new design guidelines because they may not have the background, confidence, or authority to deviate from existing official practices.
Assessment of current status
Time is of essence under the modernization programme. A rapid assessment must be made of the technology needs and present level of performance of each individual project prior to allocation of funds for specific actions. An initial assessment of current conditions is helpful for three reasons:
1. It documents the current conditions, which will be helpful in future monitoring programmes. This assessment will provide some performance criteria against which improvements can be measured.There are two general types of assessment, both of which can be used to provide an accurate view of the situation. These are:2. It documents the need for improvement and generates support. This is particularly important because a modernization programme moves faster and smoother if everyone is aware of the need for change.
3. It helps define specific actions for future improvement.
1. Focus on Symptoms: Traditionally performance assessment focus on water use and distribution efficiency and conditions such as high water tables, high salinity, and crop yields. This assessments, combined with maps of water distribution and drainage networks, may be integrated into a geographical information systems (GIS).A group of experts should be convened to develop the final assessment procedure which should include a very well defined technique of data processing and analysis. Because of the large amount of data which could be collected and the amount of time which could be potentially wasted on data entry and analysis, the initial work by these experts to streamline the effort is especially important.2. Focus on the level of service: A possible list of questions for a rapid assessment related to current level of service is provided in the attachment. This type of appraisal of how well the operations provide service is relatively new.
Assessment of the needs for physical improvements
Larger schemes should be broken down into sub-units (main canals, secondary and tertiary canals) for the assessment of the needs for physical improvements. The responsibility for such an assessment should rest with the authority in charge for the particular works. The canals under control of a water user association should be assessed by members of that association, with technical assistance from the ID.
An outline of major points to consider is provided below. Relevant technological options are discussed in the next chapter.
1. All-weather access to critical sites
a. All-weather access can be obtained either by improving the roadways or by purchasing special trucks. In some cases, it may be more economical to purchase 4-wheel drive vehicles than to invest in better road bases.2. Maintenance equipmentb. Critical sites are those with cross regulators that are crucial to the safety and flexible operation of the canal system. As sites are automated in the future, all-weather access may be provided during site construction.
c. It may be determined that there is restricted site access only during the time of year that there are very low flow rates. In that case, it may be sufficient to have access with an all-terrain vehicle during the rainy season.
a. In regions of heavy aquatic weed growth the maintenance equipment should be capable of covering the total length of canals for a certain number of times per year. In some areas, the coverage may be necessary in a 2 month period for bank shaping. In other projects, it may be necessary to remove weeds through chaining every 2 weeks. Access roads on both sides of the canal greatly facilitate these operations.3. Communications networkb. Maintenance equipment should only be funded if it is necessary for enhancing the operation of the water delivery system. This includes only the most basic maintenance of roads (except to critical sites), and does not include maintenance for cosmetic purposes.
a. It may be least expensive to have a single communications network, with expenses shared by all associations in the project.4. Improved control on the main canalsb. Equipment should be standardized within a project, even if it is not shared.
c. If associations and ID already have adequate, but non-standardized communications networks in the project, it is best to delay further investment on communications.
a. The main canals should be capable of providing 2-10 flow changes per main canal turnout per day, with less than 3% tail end spill.5. Automated secondary canal headingsb. Water levels at turnouts should be controllable within plus or minus 0.1 foot at all canal flow rates experienced during a week unless the turnouts have automatic flow rate control.
c. If main canal cross regulators are already automated with upstream control, concentration should be placed on monitoring of tail end spill and the construction of regulating reservoirs.
d. In some areas, downstream control will be the best option.
e. In other areas, a combination of improved communication, remote monitoring, and the use of buffer reservoirs may provide reasonable control for flexible deliveries.
a. If the main canal has good (plus or minus 0.1 foot) water level control at these points, the secondary canal headings do not need to be automated at this stage. However, the ability to remotely change the flow rate provides tremendous flexibility to system operators.6. New turnout designs and long crested weirsb. If operators can physically reach the canal heads within 30 minutes of the need to make a flow rate change, the headings may not need remote control.
c. Good flow measurement, in the form of broad-crested weirs, will almost always be required.
a. The designs of the turnout, the turnout flow measurement device, and the cross regulator must be considered together. In general it is desirable to have an accuracy of within plus or minus 5% flow rate control, regardless of the hourly changes in flow rate through the cross regulator.Planning procedure
Planning groups should be created at each level. Their first action would be to participate in the local assessments and review the results of the rapid assessment of the current operations and symptoms. They would then try to achieve consensus on the vision for the future operations. Special training in important technical aspects of modernization would be useful. After these first steps, local planning groups should:
1. Develop technical and management options for modernization. These should include time and cost estimates.RESULTS OF THE FIRST STAGE OF MODERNIZATION2. Request input from the review panel regarding additional options or modifications to the original ideas.
3. Present a list of technical recommendations, justifications, costs, and implications to the water user associations.
4. Modify the recommendations based upon the desires of the water user associations, and present these new recommendations to the water user associations as many times as required.
5. Request input from the regional or national review panel.
6. Receive new approval from water user associations.
7. Conduct a complete economic feasibility study.
8. Receive final approval from water user associations.
9. Implement the programme.
The modernization programme to this stage has resulted in the installation of a limited number of better gate types at critical locations (with sufficient capacity to accommodate future requirements), accounting for flows and volumes with proper measurement and control structures, improved communication, and an increased number of canal turnouts. Formation of effective water user organizations and definition of water rights were pre-requisites for these physical improvements.
Assuming that maintenance is reasonably good, the operation at this stage should now be characterized as follows:
1. Equitable deliveries to the chaks, except in some areas with insufficient canal capacities which is a problem of the original design.The water delivery infrastructure is not perfect but is quite reliable and equitable and reasonably flexible. Once these steps have been taken, noticeable improvements in project water management will be observed. Additional benefit will occur when improvements are made downstream of the chak outlet. These improvements can be sustained because the water delivery infrastructure is robust and very functional.2. Good control of flow rates at farm turnouts.
3. Reasonably flexible deliveries, with the capability to provide deliveries to individual farms with 2-3 days advance notice.
4. Some tail-ender problems in the form of spill at the ends of all secondary and tertiary canals. This spill might represent 5-10% of all delivered water, but it has not been contaminated and therefore does not damage the downstream environment.
Once the basic water delivery infrastructure has been improved, the objectives of improving agricultural production and profitability will probably have the following remaining problems (listed in order of importance for the majority of areas):
1. Poor on-farm irrigation technologies and management. The on-farm irrigation efficiencies may be in the range of only 50%. However, on-farm irrigation efficiency can only be improved when the infrastructure is in place to enable farmers to adopt more efficient technologies and management. Prior to this stage of modernization, unreliable or inflexible water deliveries would have discouraged farmers from investing in better on-farm irrigation systems.Diagnostic research tools are important in helping to decide how to best invest future funds. Funds should be spent to strengthen the weakest link in meeting the primary objective, and it may not be obvious what that weakest link is.2. Inadequate technological agronomic inputs (fertilizer, seed varieties, appropriate pesticide applications).
3. Physical bottlenecks in the water delivery system which prevent adequate water deliveries in some areas.
4. Inflexibility in deliveries and lack of control at individual farm turnouts.
5. On-farm and project drainage problems.
6. Some inflexibility in water deliveries to the chaks and some tail-ender spills.
1 There are two principal yardsticks to measure the efficiency of water use with small but significant differences:Appendix 1
Water use efficiency reflects a combination of factors, including on-farm irrigation efficiency and the whole agronomic basket of managerial and economic inputs.
Technological options of modernization
Each project is different and actual modernization requires an assessment of the technological needs of any individual project. There is, however, a certain sequence of stages in modernization which has been followed in Mexico but which was found useful in other countries as well. Care must be taken not to over-invest at any single level in the distribution system. Some major improvements in performance can be achieved with relatively simple modifications if dedicated staff are available.
1 Provide all-weather access to critical sites
Critical sites are those with cross regulators that are crucial to the safety and flexible operation of the canal system. The importance of having good access for adjustments, maintenance and repairs can not be overstated. Manual operation requires that the operator can easily reach the site. Sites with remote control and monitoring equipment also require good access because it needs adjustment and maintenance.
2 Procure more efficient maintenance equipment and optimize maintenance procedures.
Maintenance equipment should be capable of covering the total length of canals a certain number of times per year. The equipment should only be procured if it is necessary for enhancing the operations of the water delivery system. Critical equipment includes road and bank graders; vegetation movers; de-silting equipment; spare parts, repair facilities, electrical and mechanical diagnosis tools.
3 Communication network
The operation of modern irrigation systems stresses reliable and flexible water deliveries. Such deliveries can only occur if frequent flow rate changes are made throughout the system. These changes need to be ordered, executed and confirmed. A communication network which is capable of transmitting, storing and displaying a wide variety of human and equipment signals is essential. Quantity and specific nature of communication will vary with each project, however the basic communication needs include the following:
4 Improved control of the main canals
There are many ways to improve control of main canals. Improved communication and remote monitoring will be a great improvement. Providing physical storage in the form of buffer reservoirs which are strategically located along the canal can substitute for precise control and water demand predictions. Replacement of old check structures with overflow gates or composite gates with overflow characteristic provides good water level control. Eventually, all main canals will be automated to provide high quality irrigation service. In most cases the main canals have already been designed and built and the designs were based upon manual upstream control. Therefore, there is frequently insufficient pool capacity to convert to downstream control with top level canals. Local downstream control for sloping canals are still in the development stage. Gate-stroking methods have generally proven to be unfeasible. Therefore, the immediate modernization options for automation of the main canals include:
1. Upstream control using local independent controllers.The most reliable and easiest option for the main canal automation is probably option (2). Furthermore, the implementation of automated upstream control is a pre-requisite for more advanced control logic at a future date.2. As above, but with the addition of remote sensing and the ability to change the pool water level targets from a remote location.
3. Dynamic regulation, such as at the Canal de Provence in France.
4. Some form of advanced prediction programming and controlled volume, such as is used in the California Aqueduct or the Central Arizona Project.
5 Automatic flow measurement and control at secondary canal headworks.
The headworks of secondary and tertiary canals are at the interfaces of two levels of the organizational and hydraulic structure. It is therefore important that the flows from the main canals to the secondaries are stable and known fairly accurately.
In most cases the secondary and tertiary canals will be operated under upstream control. The nature of upstream control is to deliver a known flow rate into the head of a canal in order to provide exactly the flow needed at the downstream turnouts, plus allowance for seepage and some spill. That flow rate should remain constant until the operators want to change it. It is for this reason that this step in modernization includes the word control as well as measurement. Automatic control implies that the flow rate into a secondary canal remains constant, regardless of the changes in water level or flow in the supply canal. It is recommended that automatic electric gates be used to maintain a constant head on a flume because this step also includes remote monitoring and the ability to remotely (but manually) change flow rates into the headworks. Electricity will be needed for these activities.
6 Modernization of secondary and tertiary canals
Constant flow rates at the turnout to field canals are obtained by keeping the water level in the supply canal constant. Water level control is obtained with some form of automated canal check structure (cross regulator) providing upstream control. The designs in secondary and tertiary canals may not use electricity because it may not be economical to supply electricity to each cross regulator and it is generally unnecessary to have monitoring capabilities at the small cross regulators.
The three most common types of cross regulators which provide “automatic” upstream water level control are:
1. Long crested weirs. Although these are not truly automatic devices, the water level control is excellent. They generally incorporate a gate at the downstream end for flushing of silt and for making fine adjustments in water level.7 Modernization of turnouts and final distribution2. Hydraulic gates. These include the well proven Neyrtec design (AMIL gate) on flat ground, and some simple vertical tilting, hinged gates which are suitable where there are drops in the canal floor downstream of the cross regulators.
3. Electric gates controlled by microprocessor. These overshot gates are self-contained, both, the gate and computer receive power from a solar cell. Their main advantage is that the set-points of water level control can be changed.
Turnouts on tertiary canals may supply many small fields. In many cases there is no control or flexibility of water delivery beyond the turnout, because of the lack of control and measurement structures. Furthermore, the turnouts themselves often lack control and measurement capabilities.
It is apparent that modern on-farm irrigation management will require a better final distribution method than the small field ditches. In modern schemes this final distribution has been handled very successfully with the use of low pressure pipelines. Pipelines have the following advantages:
For these reasons, it is assumed that pipelines will replace field distribution ditches in later stages of modernization. New turnout structures and flow measurement devices should be designed to accommodate pipelines in the future. In conditions with very flat ground and little head from the supply canal and large flow rates canals may be needed rather than pipelines at the distributary level. Hydraulic modules will then be used to provide a constant flow rate. Only once these improvements are in place and operating, will the farmer have the incentive to invest in more efficient on-farm irrigation technology.
Appendix 2
Questions for the assessment of current operation
A. Personnel and Training needs.
These questions will differ depending upon the service level at which the questions are asked. Only the general nature of these questions is given here.
1. Awareness of various automation, hydraulics, control, and maintenance options.B. Water Records and Rates.
2. Availability of technical manuals on various topics.
3. Familiarity with computers.
4. Ability to maintain and repair a variety of technologies.
5. Perceptions of priorities and goals of modernization.
1. Base rate for access to water (none, or $/ha)Interpretation: The goal is to deliver and sell water on a volumetric basis to individual farms, with some upper volumetric limit. Farmers would know the volume they received within a few days after an irrigation.
2. Rate for actual water delivered - $ per cubic metre, hectare, or field
3. Method of accounting (hand, computerized)
4. Frequency with which individual farmers are given a record of the volumes used (never because volumetric use is not monitored; never, ____months, _____weeks, immediately after an irrigation)
5. Is there a maximum limit to the volume of water which can be used by a farmer? (yes, or no)
C. Adequacy of water supplies - rough estimate
1. Approximate area of various crops, by month (tabular
form)
2. ET requirement of various crops, by month (tabular
form)
3. Total ET water requirements, by month (tabular
form)
4. Effective rainfall, by month (tabular form)
5. Using an estimated 75% irrigation efficiency to include
both on-farm and conveyance, calculate by month:
Interpretation: If the actual deliveries exceed the gross irrigation requirement, there is no need to look for additional supplies. The challenge will be one of flexibility, reliability, and equity in water delivery, plus improved on-farm irrigation efficiency. If actual deliveries are less than the gross irrigation requirement, the eventual choices will be:
D. Present Level of Service
These questions will be answered individually for the (i) main canal system, and (ii) the canals in the distribution level. The “user” for the main canal system is the operator of canals in the distribution level.
1. Ability to maintain a constant flow at the turnout.
2. Flow measurement accuracy at turnouts
3. Equity of water deliveries along the canal.
4. Frequency and duration of deliveries.
- Are the turnout flow rates fixed or variable?5. Lateral spills. Characterize canal spills along the length of the canal as follows:
- Are the turnout flow durations fixed or variable?
- Is the turnout flow rate determined by the canal operator or by the user?
- Is the turnout flow duration determined by the canal operator or by the user?
- Are deliveries made on an arranged basis or on a rotation basis or on an arranged-rotation basis?
6. Tail-end spills. Characterize canal spills at the tail end of the canal as follows:
Interpretation: The goal after initial modernization is to have arranged schedules of a single day advance notice but with the ability to make hourly adjustments, with no spills along the canal, and less than 5% spill from the tail ends. Tail enders and head enders will receive the same quality of service.
E. Water delivery service below the turnout (chak).
1. Are deliveries to individual farms made on a rotation, arranged, or arranged-rotation basis?
2. The flow rate to individual farms is determined by: (farmer, ID, Water User Association canal operator, or Water User Association policy).
3. The frequency of irrigations to individual fields is determined by: (farmer, ID, Water User Association canal operator, or Water User Association policy).
4. The duration of irrigations to individual fields is determined by: (farmer, ID, Water User Association canal operator, or Water User Association policy).
5. How much advance notice must the farmer give before
receiving water?
Answer = __________days.
6. Can the farmer shut off his/her water unannounced?
7. What percentage of the water is lost to seepage in the distribution ditches?
8. Can more than one farmer at once receive water downstream of a single chak turnout?
9. Describe the number of farms served by one chak turnout.
- Minimum = _________10. What percentage of the farmers use:
- Maximum = _________
- Average = _________
- FurrowsInterpretation: The goal is to have improved flexibility of deliveries to individual farms. Deliveries should be available on an arranged basis, with flexibility of frequency, rate, and duration. Advance notice of one day will probably be required.
- Border strips
- Basins
- Drip
- Sprinklers
F. Present labour requirements
To be answered for all three levels: Main canal, distribution canals, and chak level.
1. Must an employee personally make the changes at
- Turnouts (yes or no)2. Number of turnouts (open and closed) served by one operator = ______
- Canal headings (yes or no)
3. Frequency of an operator passing by a typical turnout = _______hours
4. Number of turnouts served by one operator which are open at once
- Minimum occurrence = _______5. Number of flow rate changes which are made on the average turnout per week (not including adjustments to get the correct flow rate) = ______
- Average occurrence = ________
- Maximum occurrence = _______
6. Time between a flow rate change at the head of the canal and a response at the tail end of the canal under
- Low flow conditions = _______hours7. Time necessary for the employee to travel to inspect all the open turnouts in a typical day = _________hours.
- High flow conditions = _______hours
Interpretation: Present operations are probably hindered by the lack of remote monitoring and poor access to control sites. Furthermore, operators are compelled to have rigid deliveries because the control system is inflexible and requires considerable time to stabilize. Future operations should make extensive use of remote monitoring, have improved site access, and require only one adjustment at the turnout.
G. Present monitoring along the canal (for the main, secondary, and tertiary canals).
1. Collect the following information:
- Location2. The time required to stabilize flows in that service area after a change in total deliveries is characterized as:
- Frequency
- Visual (Y/N)
- Remote (Y/N)
- Accuracy if measured, +/-%
- Tail end water level
- Tail end spill
- Turnout flow rates
- Water levels at turnouts
- Headworks flow rate
|
Flow rate change |
Time to stabilize |
|
.... % |
5 hours |
|
.... % |
10 hours |
Total time period over which those adjustments are made = _______
4. What time is necessary between
a. When an emergency occurs and employees know about it = ______hoursInterpretation: See previous section.
b. When they know about it and can correct the flow rate at the head of the canal =
_________hours.
H. Seepage losses
1. Km of canal = ___________
2. Characteristics during peak flow period
Peak flow rate = ___________3. Characteristics during average flow period
Flow rate lost to seepage = ___________
Average flow rate = ___________Interpretation: Extremely high seepage losses hinder operations and prevent equitable deliveries in some systems. The early modernization steps will not address seepage losses, but they should be estimated so that their importance can be evaluated. In general, funds spent on seepage reduction can absorb a huge percentage of a project budget and may not result in improved delivery performance.
Flow rate lost to seepage = ___________
I. Condition of control equipment.
Use the table to classify the state of repair of various control devices.
Percentage of the devices which are:Excellent, Good, Fair, Poor, Non-functional
Device type:
Cross-regulatorInterpretation: Much of the disrepair may be due to deferred maintenance. These answers will provide a glimpse into the challenges faced with modernization. Excellent structures may need minimal investment for a conversion to automation, whereas nonfunctional structures may be more expensive. On the other, complete replacement of structures often allows for improved designs and larger capacities.
Flow measurement at canal head
Turnout regulation mechanism
Turnout flow measurement device
Charles M. Burt
Director, Irrigation Training and Research Center
(ITRC)
California Polytechnic State University, San Luis Obispo,
California, USA
OVERVIEW
Modernization of irrigation projects results in an improved level of service to the ultimate users, the farmers. All modernization programmes should contain these steps:
MOTIVATION AND CONTEXT
The challenge
The need for proper modernization of irrigation project deliveries is set against the following background:
1. Worldwide, there are few remaining untapped irrigation water sources, and donor and country funding for the construction of new dams is declining rapidly.Possible options for increased agricultural water supplies2. Many countries have overdrafted their water supply (surface and groundwater); irrigation has been a primary consumer of that water supply.
3. Population gains will accelerate the need for increased grain yields.
4. The least expensive and most simple options for increasing crop yields through irrigation (expanding irrigated acreage) have already been exercised; attaining incremental improvements in yield will be increasingly difficult and expensive.
5. Historically, modifications to irrigation projects did not give thorough consideration to environmental consequences. Scarce water and concern for environmental impacts increase the need for improved on-farm irrigation management.
Low irrigation efficiencies have been documented in various projects, and improved irrigation efficiencies are often listed as a major source of “new” water. However, it is now evident that return flows from an “inefficient” project are often the supply for downstream projects, in the form of surface flows or groundwater recharge. Therefore, typical project irrigation efficiencies in the 20-30% range by themselves give no indication of the amount of conservable water within a hydrological basin unless that project is at the tail end of the basin (Clemmens et al., 1995). Conservation (i.e., less spill, deep percolation, and seepage) within one project may deprive a downstream project of part of its accustomed water supply. Effective modernization programmes will have to adopt a more sophisticated approach to examining water consumption and conservation.
Most “new” water for existing basins and projects will only appear if there is improved irrigation water manageability by farmers. The potential sophistication of on-farm water management1 is highly dependent upon the level of water delivery service2 provided to individual fields, which in turn depends upon the conveyance manageability3 within the complete water distribution system (Plusquellec, 1988). For example, it is impossible to implement drip irrigation throughout an irrigation project which only delivers water to fields once every two weeks (a typical delivery schedule in most non-rice irrigation projects). Drip irrigation requires daily irrigations with dependable small flow rates.
The methods that yield “new” water will include:
1. Improved Water Use Efficiency (WUE), where WUE is defined as:Competition for agricultural water supplies
where consumption is evaporation plus transpiration
Improved WUE can come from:
- Improved use of rainfall,Although improved WUE does not generate new water, it does generate more harvested crop for the amount of irrigation water consumed. This is analogous to increasing water supply. WUE increases of 25% - 100% are possible on various grain crops if on-farm water management and associated agronomic practices are improved (Hanks, 1983; Howell et al., 1990; FAO, 1979). Water management at the field level is generally a primary constraint on improvement in other agronomic practices.
- Improved timing of irrigations to match critical stages of crop growth,
- Improved investment in fertilizers, pesticides, and cultural practices,
- Reduced waterlogging.2. Improvements in the quality of surface return flows. Water which runs off the surface of agricultural fields contains pesticides and some fertilizers, thereby decreasing its value to downstream users. Downstream users must dilute this water in order to achieve the yields obtainable with uncontaminated water. Reducing surface return flows is therefore equivalent to a small savings in water consumption.
3. Reduction of deep percolation from farmer fields, and the associated reduction of nitrate leaching. Deep percolation is expensive to the farmer and damages water quality in the aquifers. In the United States, high levels of nitrates in aquifers under agricultural lands have led to potential human health problems and crop quantity and quality reductions. Such problems can be expected in other countries as the extensive use of fertilizers expands.
4. Reduction of on-field deep percolation destined for a salt sink. This typically occurs in one of two ways. Either deep percolation passes through subsurface shale (or similar marine layer) and picks up a high load of salts, or deep percolation ends up in a salt sink, such as the ocean. This deep percolation is then unfit for future agricultural use.
Of course, agriculture is not the only user of water supplies. Urban, industrial, and environmental concerns must be considered and in the future will drive many agricultural irrigation modernization decisions.
Environmental concerns
We are beginning to understand the critical importance of maintaining minimum flow rates and water qualities in natural drains and rivers. In the United States, for example, many of the recent irrigation system modernization efforts have stemmed from the need to reduce in-stream damage to endangered species of fish. The quantities and timing of river diversions, and qualities and quantities of irrigation return flows, have a tremendous impact on the environment.
As an example, for rice production in California, new legislation requires that farmers hold water inside rice paddies (called “lockup”) for a minimum of 28 days after herbicides are applied. That is, surface drainage is not allowed during this period. This has put new pressures on the irrigation projects to provide only the amount of water which is needed, even though the weather can change rapidly.
Other farmer needs
Rice farmers may not remain rice farmers in future years, or they may grow upland crops after the rice is harvested in a single year. The demands for farm irrigation water from the project are completely different for rice, as compared to upland crops. The upland crops need a high flow rate for a short duration. Also, flow-through distribution systems (in which water flows through several fields of rice before reaching downstream fields) is unacceptable for upland crops.
With rice, it is obvious that the irrigation delivery systems must be flexible in order to respond to fluctuations in weather conditions (varying evapotranspiration rates and rainfall). There is also a need to do a better job of providing large flow rates rapidly during the initial flood irrigations.
DEFINING MODERNIZATION
Improvement
Modernization implies change for the sake of improvement, not just change for the sake of change. Therefore, the very first aspect of a modernization programme is that the present status of a project must be assessed. After an initial status and needs survey of a project, modernization can proceed in a deliberate, focused manner to address key deficiencies.
Essential Elements of Modernization
Modernization of irrigation projects virtually always involves modification of three things:
1. Everyone in the project, from the lowest operator to the highest administrator, must adopt the concept of providing good service. This requires that they understand the service concept, and truly have a desire to provide as high a level of service to their customers as is possible.There have been many studies which address the need for water rights legislation, improved hiring/firing procedures, and other social aspects of irrigation projects. While those are critical points, the three items mentioned above, especially as related to improved service, have often been overlooked and are considered by the author to be indispensable elements of any modernization programme.2. Hardware must be modified in order to provide better service. The hardware changes are the result of a deliberate analysis of service requirements. Hardware modifications may be as simple as replacing undershot gates (orifices) with manual long crested overshot gates (weirs) for water level control, or the proper installation of flow control points. In some cases, it may require more advanced supervisory control and data acquisition (SCADA) systems and automation. The desired level of water delivery service and existing budget and other constraints will define the required hardware, and not vice versa.
3. Operation rules must be changed. The way that water is ordered and delivered, the form and frequency of communications (between operators and their bosses, and between farmers and project personnel), and the way various control structures are manipulated on an hourly or daily basis must be changed to match the defined service objectives.
The concept of service
Chris Perry of IIMI has noted that irrigation is an input into agriculture, just as electrical power is an input into industrial manufacturing. Providing power without a clear definition of the service in terms of voltage, frequency, and a number of other characteristics, would greatly reduce the value of the input, because users would be unable to plan their activities or select appropriate equipment to use the resource. These considerations apply to other service or utility sectors - for example, a transportation service is defined by schedule, pick-up points, fare structure, and nature of the goods which can be carried. Distinctions among these factors are apparent for bus, taxi, train services, or a road haulage agency, and the differences allow users to compare and select the most appropriate service.
In most cases, the service definition implies responsibilities for both the provider and the user of the service; the power company is responsible for delivering 110 volts, 60 Hz. electricity to the buyer. If the user wishes to run a 12 volt DC radio, then the user must insure that the required transformer is provided. Similarly, a bus company indicates time and place of pickup and a traveler must arrive at the appropriate place, on or before the scheduled time.
Applied to irrigation, these considerations suggest a number of aspects to the definition of irrigation service.
Definition of service
The definition of water delivery service at any layer4 in the distribution system includes:
1. specification of the water right of the beneficiary (for example, cubic metres per hectare per season for volumetric deliveries, or proportional allocation of available supplies in the case of uncertain supplies);2. specification of the point of delivery (farm level; user association; 'chak' outlet);
3. flexibility in rate of delivery (fixed; variable; variable between limits);
4. flexibility in duration (fixed; variable but predetermined; variable by agreement); and
5. flexibility in frequency (every day; once per week, undefined).
The service definition will also specify the responsibilities of all parties (farmers, water user associations (WUAs), operators of the tertiary canal, operators of the secondary canals, operators of the main canals, and project authorities) in operating and maintaining all elements of the system. A main canal provides water, with a certain level of service, to secondary canals. Each upstream layer in a hydraulic distribution system provides service to the layer immediately downstream of it. The actual levels of service at each layer must be examined to understand the constraints behind the level of service which is provided to the field.
Point of differentiation
The point of differentiation within an irrigation system is the location for which upstream water deliveries can be deliberately and effectively manipulated separately with time. Downstream of the point of differentiation, all turnouts are treated identically, without the ability to provide special treatment to any of them. The point of differentiation is not the point of ownership transfer. A water user organization may become responsible for the distribution system above, below, or at the point of differentiation.
For all systems in which there is a concept of water management by the individual farmer, the point of differentiation must be at the individual field scale.
Different levels of service
It is clear from consideration of the service definition that there is a wide range of levels of irrigation service, and that the nature of the service may vary significantly from a highly flexible service differentiated at the farm level (analogous to a taxi service) to an inflexible service provided on an undifferentiated basis to a large number of farmers (analogous to a train service). For many irrigation projects, levels of service at various points through an irrigation distribution network are not clearly defined in the proposal or design stages.
EVALUATING EXISTING PERFORMANCE
History
Although the primary function of irrigation dams, canals, and pipelines is to provide water delivery service for agricultural use, there have been few significant efforts made to measure the characteristics and success of this function.
World Bank Staff Appraisal Reports (SAR) and Impact Evaluations do not yet touch upon quality of water delivery service or conveyance manageability. Rather, appraisals concentrate on large-scale inputs (gross water supply, total acreage, etc.) and gross output indicators of success or failure (IRR, cropping intensity, etc.). The internal indicators which measure and evaluate the processes between initial input and final output are not audited, analysed, or discussed in appraisal reports.
The concept of providing service in irrigation projects is relatively new, although it has been promoted before. Merriam (1973) was instrumental in providing early definitions of service in terms of frequency, rate, and duration. The idea of assessing performance, including some measures of service, is even more recent.
The realization that institutional constraints can be as important as hardware constraints in the success of irrigation projects became clear in the early 1980s. Various international organizations put considerable effort into promoting water user organizations. For almost a decade, discussions on irrigation project improvements emphasized management improvements almost entirely over better hardware selection and design. Meanwhile, H. Frederiksen and others in the Bank began to promote the concept that irrigation projects must provide service to customers. In the early 1990s, IIMI began to develop “Performance Indices” for international projects.
Murray-Rust and Snellen (1993) examined 15 projects and documented significant differences between promised versus delivered flow rates at various offtakes. They also provided a narrative discussion of factors which they felt influenced the level of service. Their recommendations emphasized management improvements over hardware improvements. Plusquellec et al. (1994) re-emphasized the importance of proper hardware selection and articulated the need for a approach to modernization based on the service concept. They pointed out that many management goals are impossible to achieve without the proper hardware in place.
IIMI has defined an action research programme for the years 1994-1998 (IIMI, 1994; ILRI, 1995) which includes some types of performance assessment. ICID has a Working Group on irrigation and drainage performance which coordinates with IIMI. The ICID Working Group (ICID, 1995) recently published a list and description of currently used performance indicators. The performance indicators emphasize ratios of volumes of water delivered, lost, and consumed at various times and locations. In addition, some indices have been developed for concepts such as dependability of supply and regularity of water deliveries.
A task committee of the Water Resources Division of the American Society of Civil Engineers has recently completed a significant, multi-year effort to provide a definitive document regarding Irrigation Efficiency (Burt et al., 1996a). A proper understanding of project and basin efficiency is an important prerequisite to making modifications in an irrigation project; there have been numerous examples of modernization efforts in the United States which have over-estimated potential water savings because the planners did not understand irrigation efficiency concepts.
Where to start
It is apparent that even though work on performance indices is relatively new, there are already several different ways to define and quantify performance. However, not all aspects of performance must be defined in order to determine how best to modernize an irrigation project.
As noted at the beginning of the paper, high efficiencies are the result of having a manageable irrigation project which provides the required degree of service. Therefore, most modernization programmes should concentrate upon improving service at all layers within the project delivery system.
Precedents
Some examples can be given of what has been successfully done to assist with modernization of irrigation projects.
Two large-scale surveys of service levels within irrigation districts have been conducted in the United States, both in California (Burt et al., 1981; Burt et al., 1996b). Key needs were identified in both surveys that allowed funding organizations to develop meaningful technical assistance and education programmes to rapidly enhance modernization efforts.
Working for IPTRID (International Program for Technology Research in Irrigation and Drainage), Burt and Wolter (1992) developed Guidelines for Irrigation System Modernization in Mexico. These guidelines were based upon a rapid assessment of irrigation projects in Mexico. Most of the recommendations have been implemented. Mexico has had a remarkably successful and rapid privatization programme of irrigation projects.
Burton et al. (1996) have recently recommended an “asset management” approach to planning long term investment in infrastructure. They conducted studies on this approach in Indonesia and found similarities between modernization in the UK water industry and irrigation projects in Indonesia. They list six stages of an asset management plan (AMP):
1. Devise procedures for preparing the AMP and keeping it up to date. These must be traceable and repeatable.Burton et al. (1996) note that “stage 2 is particularly important because it introduces the notion of service provision to customers as a key driving force in determining investment needs. This was a major step forward in terms of changing the ethos of the water utility from the provider of services as determined by the priorities of management and government to the provider of service to the customer.”2. Prepare a statement of the project's relevant standards and policies.
3. Identify various functions of the project and prepare a list of systems under each heading. Each system will comprise of a number of assets.
4. Collect information on performance and condition of the principal components of each system. This may be done by sampling. (Note that performance information relates to a system, whereas condition information relates to individual assets).
5. Estimate long term investment (20 years).
6. Prepare short term programme of expenditure for 5 years.
In short, they have also endorsed the absolutely necessity of adopting a service ethic and philosophy if there is a desire for modernization.
COMPONENTS OF A STATUS SURVEY
General
A survey of an irrigation project status does not necessarily require many years of study. In general, the water delivery and service aspects of a project can be evaluated in a few weeks or less by experienced personnel.
Defining the levels of service in a project
The first thing to identify in any pre-modernization study is the existing level of service. It is important to re-emphasize that an irrigation project is a network which consists of many hydraulic delivery layers, and each layer provides service to the next lower layer, finally ending at a “point of differentiation”. The levels of service may be different at each layer.
A study should not only identify what the existing level of service is, but what the expectations are at each layer of operation. Factors to define in a study include:
1. The flexibility of water delivery. The three aspects of flexibility, at any layer in the system, are:Controllability of watera. Frequency. How often can water be delivered, or can a flow be changed when desired?2. The equity of water delivery to all levels in the system.b. Flow rate. What flow rate can be delivered at a point? How often can the flow rate be changed, and how much advance notice must be given? Is the flow rate controllable? Is the flow rate even known?
c. Duration. Can the duration of an irrigation or water delivery be adjusted?
3. The reliability of water deliveries. If something is promised, is the promise fulfilled?
4. The timeliness of water deliveries. If a flow rate change or delivery is scheduled for 09.00 hours, can it actually occur at that time?
What really sets modernization apart from rehabilitation is the improvement of the controllability of water for the purposes of providing better service. The controllability of water in a project depends upon many things, most of which should be evaluated in a status study. These include:
1. Ease of access to key structures and delivery points.General project conditions
2. The communication system. Aspects to consider are:
- What information is communicated?
- How often is the information communicated?
- Who communicates to whom?
- Is the communication system reliable?
- How is information archived and accessed?
3. Operation instructions. Often, the instructions given to operators are impossible to follow and the operators may actually move or manipulate the structures in an entirely different manner than what is perceived in the office.
4. The types and locations of water level control structures. For example, manually operated underflow gates are extremely difficult to operate correctly if the flows change frequently.
5. The types and locations of flow control and flow measurement structures. These are often two different types of structures.
6. The number of parcels receiving water downstream of the most downstream flow control point.
7. Lag time (wave travel time) throughout the system.
8. The existence of buffer storage and freeboard.
9. The relative elevation of canal water surfaces above the turnouts.
10. Robustness of structures, and the general condition of them.
The specific solutions, and the economic viability of them, will also be affected by other conditions which should be examined in a status study. These include:
1. The relative magnitude of seepage losses.In order to establish modernization programme priorities, the values of these factors do not need to be known precisely; rather, an approximate estimate of their magnitudes is sufficient. For example, a detailed study of seepage losses would take a long time and be very expensive, and the detailed knowledge gained from such a study would not change the decisions made regarding the first appropriate modernization steps.2. The existence of conjunctive use.
3. Whether the water supply is from a controlled supply (i.e., a dam) or from a rapidly fluctuating river.
4. Typical crop yields and intensity of farming.
5. Rainfall patterns.
6. The existence and enforcement of water rights and laws.
7. The quality of the maintenance.
Social issues
Certain social issues have been observed to be important for the viability of water projects. These include:
1. The existence of a reasonable method for assessing costs for water and the ability to collect those water charges and to withhold water from those not paying.Assessments should briefly examine these factors, to help determine if new policies and enforcement capabilities will be needed in the future.2. The characteristics of project employee/employer relationships. Some aspects to consider include:
- The existence of incentive programmes for employees.
- The existence of meaningful training programmes.
- Salaries of employees.
- The ability to assess performance of employees, and the ability for managers to separate those with documented poor performance.
- The tenure of employees (how long they have worked on the project).
DEFINING THE NEEDS
Sharing a common vision
Once the status of a project has been documented, the real challenge remains - defining what should be done in the modernization programme.
The decision of what should be done is generally arrived at with the consensus of many parties. It is therefore important that all parties share a common vision of the points which were detailed at the beginning of this paper. These include:
What we have learned at the California Polytechnic State University is that when we work with irrigation projects in the United States, we need to start by bringing all the key players together for a short (few days) training programme. Such an orientation programme emphasizes the service concept, and various water control strategies which are available to help provide good service. We try to bring together policy makers and engineers in the same room, so that they share the new vocabulary and the same point of reference for future discussions of modernization options.
In short, a first step for meaningful modernization is an education/awareness component on the general concepts of modernization.
Engineering education
A second step is to make sure that the engineers and technicians who will be involved in the project have the proper tools with which to recommend improvements. One only needs to look at the poor levels of performance of existing projects to conclude that we have some serious problems in this regard. In general, water control concepts are not taught to engineers in college. Unfortunately, many universities believe that they are being taught. The biggest question is: where can people get the proper education?
This is a sensitive subject. There is almost a natural inclination for engineers to have a defensive attitude about their present designs, because they have worked very hard on various projects, and discussions of change may imply that in the past they did not do a good job. What needs to be conveyed, however, is that there are new techniques available to help us work smarter. The changes need to be presented as opportunities rather than as criticisms - a difficult task. We have found that if we can get past defensive attitudes about the existing projects, engineers can quickly grasp the concepts of design for modernization. Resources are available, such as the slide series on modernization by the World Bank (Plusquellec, 1988) and training programmes by a few organizations such as the California Polytechnic State University Irrigation Training and Research Center (ITRC).
The concepts of service absolutely must filter past the upper levels of management. The design engineers who actually do the structure drawings (individuals who are not paid to risk anything) must also be provided with specific design tools. For example, if there is a standard design handbook, it will almost certainly need to be upgraded so that the lower-level engineers will actually design the correct structures.
Typical design changes
The points covered earlier in this paper regarding questions for a status survey will give good guidance for modernization. A typical sequence for modernization, after initial education efforts, will be something as follows:
1. Demonstrate the effectiveness of modernization on a small but significant part of the project. Actions often include:Cost effectivenessa. Improvement of access to key control sites.The participation of farmers and water user organizations is generally not useful when changes are made to the main canal system. However, their participation is extremely valuable and necessary when changes are made to the system at the distributary or small lateral level.b. Improvement of communications (people-to-people) through the use of radios.
c. Implementation of flow control and flow measurement at the headings of key laterals.
d. Installation of a few remote monitoring sites.
e. Improvement of water level control structures, such as with automatic hydraulic gates or simple long crested weirs.
f. Improvement of turnout structures and locations.
g. Formation of effective water user organizations, often which operate like a business, at the lower ends of a system.
h. Improvement of maintenance programmes.
The author is a bit hesitant about the wording of this recommendation, because it may appear to be nothing more than a typical “pilot project” recommendation. A difference here is that selective improvements can be made simultaneously throughout the system, rather just having them concentrated in one area. These improvements would not be considered demonstrations as much as initial shake-down trials.
2. Make certain that the initial efforts work and work well. Frequently consult with the people who are affected by those improvements, whether they be canal operators, engineers, or end users (farmers). Be certain that those individuals are happy with the improvements, solicit their suggestions, and incorporate necessary changes.
3. Bring in people from other areas of the project and let them talk with the people involved in step (2). These people from other areas will develop a desire for changes in their own regions if the local people are enthusiastic. If the beneficiaries mentioned in step (2) are not convinced and enthusiastic, the project modernization efforts are probably inappropriate.
4. Develop a master plan for the complete project modernization, using lessons learned in steps (1) and (2), and relying on input from operators and users throughout the project.
5. Begin to implement the larger plan for modernization.
One of the biggest hurdles facing modernization efforts is the desire to compute the cost effectiveness of all proposed improvements. Although the author understands the absolute necessity of economic viability, the author has also learned that traditional engineering economics are insufficient for modernization programmes. For example, a large diameter pipeline (which can provide much more flexibility than a small pipeline) will always cost more per meter than a small diameter pipeline. The true economics must consider whether or not yields will increase (a difficult thing to estimate and guarantee), and how improved service will affect recovery of water charges and maintenance. These factors will not necessarily show improvement in the first or second year.
SUMMARY
What is presented here is a conceptual framework for the process of modernization. What is important for irrigation projects is not the number of hectares served, or the kilometres of canal, or the number of structures. Rather, the key factor is how well all those kilometres of canal and hundreds of structures function to provide the defined and required level of service to the ultimate users. To provide good service to the farmers, a project must be considered as a network of layers, each of which provides service to the next lower layer.
A status and needs survey should be conducted in any project prior to modernization. The survey can be rather brief, only needing a few weeks or months. However, it must be targeted to identify the levels of service provided (i.e., performance) and the factors which affect that performance.
In most of the many projects that the author has visited worldwide, there are serious deficiencies in the hardware designs and physical water control. Often, very simple and robust solutions are available to solve these problems. A first step to solving them, however, requires a common understanding of control principles.
The question of cost will always arise in modernization programmes. The author has observed that many, if not most, modernization programmes are underfunded. There is no shortcut to some things - it simply takes money and time to make certain changes. Of course, there are always some effective changes which can be made at a small cost.
When considering costs of modernization, one might remember a popular slogan: “If you think education is too expensive, just see how much it costs without it”. Similarly, with irrigation projects we know that the performance must improve. The competition for water is growing, and the need for food is also increasing. Can we afford to not modernize? The author believes we cannot.
Successful modernization programmes will require strong individual leaders who have vision, and who are willing to gamble for the future. These leaders must be nurtured at all levels of projects, from the project managers to university professors to canal operators to farmers. Only then will we meet the challenges which face us.
ACKNOWLEDGEMENTS
The author would like to thank Messrs. Herve Plusquellec, Randall Purcell, and Chris Perry for valuable input to many of the ideas presented in this discussion.
REFERENCES
Burt, C. M., Clemmens, A.J. Strelkoff, T.S. Solomon, K.H. Bliesner, R.D. Hardy, L.A. Howell, T.A. and Eisenhauer, D.E. 1996a. Irrigation Performance Measures - Efficiency and Uniformity. Task Committee on Efficiency and Uniformity. Water Resources Division of the American Society of Civil Engineers. submitted to Journal of Irrigation and Drainage, ASCE.
Burt, C., O'Connor, K., Styles, S., Lehmkuhl, M., Tienken, C. and Walker, R. 1996. Status and Needs Assessment: Survey of Irrigation Districts, USBR Mid-Pacific Region. Irrigation Training and Research Center. California Polytechnic State University. San Luis Obispo, CA 93407. 39 p.
Burt, C., Gartung, J., Lord, J., Parrish, J. and Bryner, J. 1981. Distribution System Improvement to Facilitate Water Delivery. A report by JM Lord, Inc. to the Agric. Division, Office of Water Conservation, Calif. Dept. of Water Resources.
Burt, C. and Wolter, H.W. 1992. Guidelines for Irrigation System Modernization in Mexico. A Report to IPTRID. Prepared for the Comision Nacional del Agua, Mexico.
Burton, M.A., Kingdom, W.D. and Welch, J.W. 1996. Strategic investment planning for irrigation. Irrigation and Drainage Systems 10:207-226. Kluwer Academic Publishers. The Netherlands.
Clemmens, A.J., Strelkoff, T.S. and Burt, C.M. 1995. Defining Efficiency and Uniformity: Problems and Perspectives. Proceedings of the ASCE Water Conference in San Antonio, Texas (Water Resources Engineering). American Society of Civil Engineers, N.Y., N.Y. pg. 1521-1525.
FAO. 1979. Yield response to Water. Doorenbos, J. and A.H. Kassam. FAO Irrigation and Drainage Paper 33. FAO, Rome.
Hanks, R.J. 1983. Yield and water-use relationships: an overview. In: Limitations to Efficient Water Use in Crop Production. Chapter 9A. Amer. Soc. of Agronomy. Madison, WI.
Howell, T.A., Cuenca, R.H. and Solomon, K.H. 1990. Crop yield response. In: Management of Farm Irrigation Systems. Chapter 5. ASAE Monograph 9. Amer. Soc. of Agric. Engr. St. Joseph, MI.
ICID. 1995. Currently Used Performance Indicators. Research Program on Irrigation Performance. Contact: M.G. Bos, Wageningen, The Netherlands.
IIMI. 1994. Assessing and Improving the Performance of Irrigated Agriculture: Indicators of Productivity, Economic Profitability and Environmental Sustainability. An Action Research Program: 1994-1998.
ILRI. 1995. Research Programme on Irrigation Performance, RPIP. Annual Progress Report no. 2. A report by the Intern. Inst. for Infrastructural Hydraulic and Environ. Engr. (Delft, the Netherlands), IIMI, and ORMVAM (Berkane, Morocco)
Merriam, J.L. 1973. Float Valve Provides Variable Flow Rates at Low Pressures. Agricultural and Urban Considerations in Irrigation. ASCE Specialty Conference. Ft. Collins, Colorado. April 22-24. pp. 385-402.
Murray-Rust, D.H., and W. B. Snellen. 1993. Irrigation Performance Assessment and Diagnosis. Colombo, Sri Lanka. International Irrigation Management Institute. 148 pp.
Perry, C. 1995. Determinants of function and dysfunction in irrigation performance, and implications for performance improvement. Water Resources Development 11(1): 25-38.
Plusquellec, H. 1988. Improving the Operation of Canal Irrigation Systems. A seven-part slide series. Washington, D.C. The Economic Development Institute of the World Bank.
Plusquellec, H., Burt, C. and Wolter, H.W. Modern Water Control in Irrigation - Concepts, Issues, and Applications. 1994. World Bank Technical Paper No. 246. Washington D.C.
Sadiqul I. Bhuiyan
Water Resource Specialist, Soil and Water Sciences
Division,
International Rice Research Institute, Los Baños,
Philippines
INTRODUCTION
Modernization of an irrigation system could be defined as the act of upgrading or improving the system capacity to enable it to respond appropriately to the water service demands of the current times, keeping in perspective future needs. Since irrigation water is a limited and progressively scarcer resource, maximizing the productivity of water and the benefits from water use must be considered a primary objective of irrigation modernization. Modernization may or may not have any physical or structural improvement component - e.g., in certain situations, improvement in the operational procedures of the irrigation system or enhancement of the system’s personnel capacity for improved operations may constitute the only activity of the modernization process. On the other hand, another set of conditions may require significant structural changes in the water control, conveyance, or distribution system as a major component of the modernization process.
In rice-growing Asia, about 80-90 percent of all freshwater resources used are for agricultural purposes and more than 80% of this water is used for irrigating rice. It is evident that agriculture’s share of water will be decreasing constantly through the coming years as investments for new water resources development have declined in recent years to relatively insignificant rates and competition for the available water from industry and urban sectors continues to grow at high rates. In some Asian countries, the anticipated decline in per capita water availability in the next 20-30 years is very high (Figure 1).
Currently, much water is used in rice production. About 5 000 litres of water are needed to be diverted at the irrigation system source for each kilogram of rough rice produced in the field (IRRI 1995). Clearly, means of producing rice with less water in irrigation systems must be used in future in order to prevent serious rice supply crisis due to water shortage. In other words, the efficiency of water use in irrigated rice production systems must be significantly increased. The existing strong interdependence between water use in the crop production subsystem and the operation of the irrigation facilities for water service elicits the need for pursuing a comprehensive agenda for improving the performance of rice irrigation systems. The need for modernizing irrigation schemes must be conceived with full understanding of this interdependence.
In this paper, irrigation systems that are specifically developed for supporting rice production, mainly in the humid tropics, are in focus. Therefore, irrigation systems in semi-arid areas, where certain unique water allocation systems such as the “warabandi” system(northwestern India, Pakistan) or the “localization” concept (south India) are used to maintain a balance between rice and non-rice crop culture (Pike 1995), are not considered. The paper aims to establish the unique features of rice irrigation systems and present a rational approach to modernizing such systems, with special reference to facilitating diversified cropping.
FIGURE 1. Projected change in per caput water resources, selected Asian countries (Source: Gleick, 1993)
WILL IRRIGATION MODERNIZATION LEAD TO RICE SHORTAGE?
Will rice production be reduced as a result of modernization of rice irrigation systems? This would be a valid concern if the modernization process is carried out with the main aim of converting large areas from rice culture to non-rice cropping. It must be recognized that the demand for rice is still growing in almost all developing countries of Asia. By the year 2025, rice production in Asia must increase by 67% from the 1995 production level in order to meet the increased demand for this cereal which is the staple food for more than one-half of the world’s population (Hossain, 1995). Since no major net addition to currently irrigated rice areas is expected in the coming decades and major breakthroughs in raising yields of rainfed rice systems are unlikely to be available during this period, most of this additional rice will have to be produced in irrigated areas. Therefore, major investments to enable rice irrigation systems to reduce the rice area can hardly be justified.
However, it should be kept in mind that, when flexibility of crop choice is considered, rice must also be included among the possible crops. Presently, it is generally true that rice is the chosen crop to be grown in the dry season by most farmers if enough water is assured. Apart from the domestic need for the staple and familiarity with rice culture, farmers preference for rice is due to its comparative advantage over most other crops, e.g., higher yield potential in the dry season, assured marketing of surplus at predictable prices (price fluctuation is much less for rice than for most other crops), availability of good storage technology (farmers may, with relative ease, store rice at home and are not compelled to sell at the low price prevailing at peak of harvest season), lower production risk (rice production technology is fairly robust), and lower cost of production. Returns from rice cropping are significantly higher in the dry season compared to the wet season. One can therefore expect that rice’s advantage over many non-rice crops, as discussed above, will probably hold for most of the irrigated areas.
WHY DIVERSIFY CROPPING?
In rice irrigation systems, rice monoculture is overwhelmingly the dominant practice. Diversification of the crop production system in these areas is desirable for several reasons. First, diversification will open opportunities for increasing farmers’ income from their limited land resources. This is particularly important at the present time when profits from rice culture are very low and declining. Second, it is increasingly evident that, as productivity of the land under rice monoculture under wetland conditions is declining over time (Cassman and Pingali, 1995), a diversified agriculture will be more sustainable in the long-run. Third, with increasing scarcity of water, irrigated agriculture will have to aim at maximizing return to water rather than return to land. Present rice culture system requires more water than most other food crops, both in terms of quantity of food and calorie produced (Bhuiyan, 1992). Therefore, a major scope exists for increasing returns from water by growing diversified crops, especially in areas of water shortage.
UNIQUENESS OF RICE IRRIGATION SYSTEMS
To enable farmers to diversify their cropping pattern, they must be provided with facilities to exercise crop choice options, which is presently lacking in most rice irrigation systems. Attempts to rectify this situation through modernization would be better directed by clearer understanding of the reasons for the lack of flexibility of crop choice in rice irrigation systems. Most of these reasons are ingrained in the way the systems are conceived, designed and developed.
The physical and climatological characteristics of rice irrigation systems in Asia, where about 90% of world’s rice is grown and consumed (IRRI, 1989), are that they are developed to provide irrigation water for single or double cropping of rice in areas where:
Each of the above characteristics can contribute to creating an excess water condition in the field in the wet season, which rice can tolerate (but does not like or need it for good yields) much longer than most other crops without major penalty. At the same time, in the dry season, when total water availability at the source is generally limited, access to water in farms located farther from the water source is non-existent or highly inadequate (rice adjusts much more poorly to water shortage than diversified crops). The issue of providing flexibility for crop choice must be viewed in the context of these facts.
PERMANENT VS. SEASONAL FLEXIBILITY OF CROP CHOICE
Permanent conversion of irrigated ricelands for diversified cropping will be far-fetched and unsustainable. The cost of land shaping, drainage provision, etc., that would be needed for permanent conversion will be very high. In recent years permanent conversion has occurred, as an exceptional case, in Thailand, in some irrigated rice areas close to Bangkok city at a high cost of about $5 000/ha (Barghouti et al., 1990). This is in response to the heavy demands for vegetables and horticultural products from the metropolis. The high degree of suitability of the soils of those areas for fruits and vegetables was a contributory factor to this conversion.
From the above discussions, it seems clear that the objective of giving a choice of crops is technically and financially justifiable for the dry season only. Exception to this may be feasible only on very light-textured soils with relatively deep water tables, and moderately light soils in high-ground areas.
THE WET SEASON - DRY SEASON DUALISM
The changing characteristics of the rice irrigation system between the wet and dry season have a strong influence on both the management of water at the system level and use of water by farmers. This is a significant contributory factor to the problem of low water use efficiency in rice irrigation systems. The supplemental nature of irrigation for rice in the wet season makes it difficult for water users to perceive the need to comply with the system’s rules and regulations on construction, maintenance and use of on-farm irrigation and drainage facilities such as main farm ditches, division boxes, and internal farm ditches. A special requirement for adhering to the rules and regulations is that all farmers using water from a single turnout (in the Philippines, a turnout usually serves 30-60 ha, hence a large number of farmers are involved) have to work cooperatively, which is considered a burden by many (increasingly, farmers want to spend less time on field works). In the dry season, when rainfall is small and water stored in the reservoir is also limited, these structures are more clearly needed for good water management, but it becomes difficult for farmers to accept the cost of maintaining them for one season only. In the lower (far-from-source) areas of major canals, the uncertainty and inadequacy of irrigation water delivery in the dry season also acts as a deterrent to farmers’ being fully motivated to take care of on-farm irrigation and drainage facilities. On the other hand, farmers with lands in the upper ends of the system usually have access to unlimited quantity of water because of their advantageous locations, and are generally not motivated to comply with the water-efficient irrigation regulations.
This complex relationship between water availability/non-availability and farmer motivation has been demonstrated in a study of the Upper Talavera River Irrigation System (UTRIS) in Central Luzon, Philippines. There, farmers in the upper section of Lateral B (second lateral), where limited amounts of irrigation supply has been historically available in the dry season, successfully grow non-rice crops, with elaborate water control facilities established seasonally (Bhuiyan, 1989). But in Lateral A (first lateral), in which the dry season supply has historically been adequate, farmers have used least on-farm water control structures and have always grown rice in the dry season. The soils in lateral A area are also heavier than those in lateral B area which is better suited for diversified crops.
NEED FOR INFRASTRUCTURAL ADJUSTMENT: PERMANENT OR SEASONAL?
The task of upgrading or modernizing an irrigation system for rice cropping in the wet season and for diversified cropping in the dry season is complex. It requires that any permanent structural or physical upgrading to be done for rice must also conform to the requirements of the diversified crops to be grown in the dry season. It is therefore logical to assume that the upgrading of common denominator factors, i.e. factors that are relevant for both seasons, could be upgraded permanently and these should be handled by the main irrigation system. Examples of these would include upgrading of water control, drainage, reliable schedule of water delivery, etc. at the main system. The on-farm, crop-specific factors should be handled seasonally by the farmers themselves as individuals or as groups. Examples of this type of upgrade would include the same items, as above, but at the farm level. Delineating responsibility of modernizing a rice irrigation system, using the above principle, seems equitable, practical and cost-effective.
Some of the on-farm structural upgrading may need construction of temporary (seasonal) water control facilities that would occupy some land area when diversified crops are grown. These may be erased out while preparing the land for wet season rice cropping. Such a process of seasonal adjustment by farmers for successful diversified cropping has been found in the Philippines. The functions of these water control facilities have been analysed and found highly effective (Bhuiyan, 1989; Tabbal et al., 1990). Effective functioning of similar, seasonal on-farm facilities for diversified cropping has been reported for Bangladesh by Mondal et al. (1993).
IS THE IRRIGATED DIVERSIFIED CROPPED AREA INCREASING?
Reliable data on areas grown to diversified crops within rice irrigation systems are scanty. While one would expect an increasing trend in the use of irrigated lands for diversified cropping, there is doubt that it has really been happening in recent years. An analysis of Bangladesh government’s published statistics (BBS 1995) indicates that there has been very little growth of irrigated non-rice crop areas between 1982-83 and 1992-93 (Figure 2). Mondal et al. (1993) indicated that in the water-starved tailend areas of the large G-K irrigation project, farmer adoption of non-rice crops using residual soil-water after the harvest of the main rice crop has significantly increased. The impact of a recent move to promote use of shallow groundwater in those areas (there was a legal ban on use of groundwater in the service area of the canal-based irrigation system, which was lifted recently) should be assessed in-depth. In Thailand, the proportion of the total irrigated area grown to diversified crops increased from 9.2% in 1985 to 12.4% in 1986, but remained more or less stagnant during the subsequent three years (Ouraikul et al., 1993).
During 1985-89 the annual rate of growth in the total area within “wet lands” (which is taken here as irrigated ricelands) that was used for producing five major non-rice crops (maize, cassava, potato, peanut and soybean) declined slightly - by -0.4% in Java, Indonesia (Pasandaran et al., 1993). For Indonesia as a whole, a modest 1.0% growth rate was estimated for the period by the authors. They explained the negative growth in Java as being caused by substantial decrease (-3.5% annually during 1985-89) in maize area. Since Java has nearly 80% of the total non-rice crop area within irrigation systems in the country, the above figures imply that, during the period, most areas that went out of maize either remained fallow or did not grow any of the above-mentioned five major crops.
In the Philippines, about 207 000 ha or 35% of the total irrigated area under the national irrigation systems (NIS) have been considered suitable for diversified cropping. In 1989-90 dry season, about 6,870 ha or 1.1% of the NIS service area were planted to irrigated diversified crops and about 5,900 ha to unirrigated diversified crops. In the following dry season, the diversified crop areas were reduced to 4,940 ha irrigated and 4,280 ha unirrigated, representing a decline of 28 and 27% respectively (Maglinao et al., 1993).
The proportion of the total irrigated area that is potentially suitable for diversified cropping in Sri Lanka is 31% in the Maha and 55% in the Yala season. During 1990-91, about 22% of the Maha’s and 17% of the Yala’s Potential areas were actually utilized for diversified cropping (Jayewardene et al., 1993).
We must understand better why most Asian farmers prefer to continue growing rice in the dry season, even in areas where soils are highly suitable for diversified cropping. We must also understand better why and how some farmers are successful in growing non-rice crops.
FACILITATING THE CROP DIVERSIFICATION PROCESS
In the past decade or so, numerous deliberations have taken place focusing on the issues of how irrigated crop production systems can be made more diversified. A number of special projects to promote diversified cropping within rice irrigation systems were undertaken in several countries. Evaluations of these actions can enhance our understanding of sustainable diversification processes and their practical implications.
The process of crop diversification for an irrigated area must be viewed in the context of the greater socio-economic environment. Clarity of purpose is a basic need for this process to succeed and sustain. The goal behind promotion of diversified cropping should be raising and stabilizing rural incomes, not increasing crop production per se. The diversification process must be demand-driven (Timmer, 1992). Removing technical constraints to diversified cropping, including water related constraints, may be a critically important objective to pursue in many situations, but they are a means rather than the end itself. For example, the need to provide capacity for quickly removing excess water from the field is a universal requirement for sustainable non-rice cropping enterprise. But, in practice, they will be needed only if there is a sustained demand for the products and there is economic incentive to grow these crops. Institutional constraints (e.g. lack of marketing mechanism or availability of good seeds) alone may limit farmers’ non-rice crop culture, even when all else seem right. Fluctuating price of products and lack of storage facilities can discourage farmers to grow non-rice crops. In final analysis, it is the logical, risk-aversive nature of farmers’ decision-making process that will ultimately determine their crop production pursuits. Is it then so surprising that most small-holder farmers still prefer to grow rice in the dry season if they have access to adequate water?
What are some of the basic improvement factors in rice irrigation systems that will promote and facilitate diversified cropping? Local conditions will invariably influence this choice, but attention to the following items is central to answering this question for most situations.
Understanding of the demand for diversified crops
The structure of demands for potentially attractive non-rice crops from the local community and the regional market should be well understood. This should form the basis for conceiving any institutional support program, including support for irrigation system modernization, that is considered needed.
Emphasis on areas with light-textured soils
The areas with light-textured soils that are inherently more suitable for producing non-rice crops should be delineated and their water management improvement needs assessed. These, or part of these, should constitute the core areas for diversification programme thrusts.
Improvement of drainage capacity
For high yields, all non-rice crops will require good drainage capacity of the land. As discussed earlier, most rice irrigation systems have poor drainage capacity. In the dry season, canal operation for dual purpose functions (both irrigation supply and drainage) should be considered if surface drainage improvement is difficult due to flat topography.
Augmentation of water supply
Reliable water supply is critically important for diversified cropping as farmers have to invest much more for these crops compared to rice. Areas that are far from the irrigation source generally suffer more water shortage in the dry season compared to near-by areas. Means of augmenting water supply in these areas, if they are suitable for diversified cropping, have to be found. Shallow groundwater development through the private sector is often the most reliable and affordable water source for this purpose. Groundwater has the advantage of being available on demand at the farm and able to avoid major water distribution problems.
The above can be considered as the necessary, but not sufficient, generic factors that support crop diversification in rice irrigation systems. Institutional issues such as credit and marketing facilities are usually site-specific, which may require appropriate interventions that would lead to sustainable development of the institutions. As discussed earlier, the site- and crop-specific production related issues can be more appropriately handled and resolved by farmers individually or as groups, with some institutional support, as needed. These may include such issues as suitable methods of water application to the crop (e.g., basin, furrow or basin-cum-furrow), methods of controlling seepage from canals or neighbouring rice areas (e.g., dikes, interceptor channel, dike-cum-interceptor channel), or means of drainage enhancement (e.g., collector gravity drain, pumping, collector-cum-pumping). Similarly, technical problems of farmers’ access to quality seeds, agronomic management of the crop for optimal yields, etc. may be addressed with some institutional support. In all the above, efforts should be made to allow the private sector entrepreneurship to grow and function properly.
CONCLUDING REMARKS
Modernization of rice irrigation systems must not be viewed as an attempt to convert the so-called low-efficiency gravity, canal-based irrigation to pressurized, high-efficiency irrigation techniques such as sprinklers and drips. There is no doubt that pressurized systems are not technically suitable or economically feasible for irrigated rice production systems in Asia.
Properly done, modernization of rice irrigation systems can be highly beneficial to both the water users and the society at large. Diversified cropping requirements must be thoroughly considered in pursuing the modernization process, with the objective of raising farmers’ incomes through provision of flexibility and option to choose crops in the dry season. The apparent antagonism between the water-abundant environment required for rice culture and the precisely controlled water management demanded for successful non-rice crop culture is often an overblown concern. Examples abound in which farmers within ordinary rice irrigation systems have found effective solutions to this problem in areas where there is enough incentive to grow non-rice crops.
In the modernization process, an important decision to make concerns the type of upgrade that should be done and managed at the main irrigation system level and those that farmers themselves should handle. The roles that farmer entrepreneurship can play in the provision of these upgrades, especially the seasonal upgrades, must be better understood and promoted in order to make the crop diversification process sustainable in the long-run. In this endeavour, we must keep our faith in the ingenuity of farmers in solving their on-the-ground problems.
ACKNOWLEDGEMENTS
The author is grateful to his colleague Dr. T.P. Tuong, Water Management Scientist, Soil and Water Sciences Division, IRRI, for his useful comments on an earlier version of this paper.
REFERENCES
Barghouti, S., Timmer, C. and Siegel, P. 1990. Rural diversification: lessons from East Asia. World Bank Tech. Paper No. 117 (111 pp.). World Bank. Washington, D.C
BBS (Bangladesh Bureau of Statistics). 1995. 1994 Statistical Yearbook. Govt. of Bangladesh. Dhaka, Bangladesh.
Bhuiyan, S.I. 1989. Irrigation and Water Management for Diversified Cropping in Rice Irrigation Systems: Major Issues and Concerns. Overseas Development Institute (ODI), London. ODI/IIMI Irrigation Management Network Paper 89/1e.
Bhuiyan, S.I. 1992. Water management in relation to crop production: Case study on rice. Outlook on Agriculture 21(4): 293-299.
Cassman, K.G. and Pingali, P.L. 1995. Extrapolating trends from long-term experiments to farmers’ fields: The case of irrigated rice systems in Asia. In: Agricultural Sustainability: Economic, Environmental and Statistical Considerations. V. Barnett, R. Payne and R. Steiner (eds.). John Wiley, England. Pp. 64-68.
Gleick, P.J. (ed.) 1993. Water in Crisis: A Guide to the World’s Fresh Water Resources. Oxford University Press, New York.
Hossain, M. 1995. Sustaining food security for fragile environments in Asia: Achievements, challenges, and implications for rice research. In: Fragile Lives in Fragile Ecosystems. IRRI, Los Baños. pp. 3-23.
IRRI (International Rice Research Institute). 1989. IRRI Toward 2000 and Beyond. IRRI, Los Baños.
IRRI (International Rice Research Institute). 1995. Water: A Looming Crisis. IRRI. Los Baños.
Jayawardene, J., Jayasinghe, A., and Dayaratne, P.W.C. 1993. Promoting implementation of crop diversification in rice-based irrigation systems in Sri Lanka. In: Promoting Crop Diversification in Rice-based Irrigation Systems. S.M. Miranda and A.R. Maglinao (eds). International Irrigation Management Institute, Colombo. pp. 93-103.
Maglinao, A.R., Lantin, M.M. and Galvez, J.A. 1993. Promoting implementation of crop diversification in rice-based irrigation systems in the Philippines. In: Promoting Crop Diversification in Rice-Based Irrigation Systems. S.M. Miranda and A.R. Maglinao (eds.). International Irrigation Management Institute, Colombo. Pp. 77-92.
Mondal, M.K., Islam, M.N., Mowla, G., Islam, M.T. and Ghani, M.A. 1993. Impact of on-farm water management research on the performance of a gravity irrigation system in Bangladesh. Agricultural Water Management 23(1): 11-22. Elsevier Publishers, Amsterdam.
Ouraikul, A., Rewtarkulpaiboon, L. and Somwatanasak, S. 1993. Promoting implementation of crop diversification in rice-based irrigation systems in Thailand. In: Promoting Crop Diversification in Rice-Based Irrigation Systems, S.M. Miranda and A.R. Maglinao (eds.). International Irrigation Management Institute, Colombo. pp. 105-118.
Pasandaran, E., Soenarno and Pusposutadjo, S. 1993. Irrigation development and management strategies to support rice-based crop diversification in Indonesia. In: Promoting Crop Diversification in Rice-Based Irrigation Systems. S.M. Miranda and A.R. Maglinao (eds.). International Irrigation Management Institute, Colombo.pp. 35-50.
Pike, J.G. 1995. Some aspects of irrigation system management in India. Agricultural Water Management 27(2): 95-104. Elsevier Publishers, Amsterdam.
Tabbal, D.F., Bhuiyan, S.I. and Lampayan, R.M. 1990. Water control requirements and complementarities for rice and nonrice crops. In: Irrigation Management for Rice-Based Farming Systems in the Philippines. A.R. Maglinao (ed.). Philippine Council for Agriculture, Forestry and Natural Resources Research and Development, International Irrigation Management, and IRRI. Los Baños. pp. 14-37.
Timmer, C.P. 1992. Agricultural diversification in Asia: Lessons from the 1980s and issues for the 1990s. In: Trends in Agricultural Diversification. S. Barghouti, L. Garbus, and D. Umali (eds), World Bank, Washington, D.C. pp. 27-38.
Dia El Din El Quosy
Director, Water Management Research Institute,
National Water Research Centre, Cairo, Egypt
INTRODUCTION
Many irrigation schemes in the world are as old as the countries they serve. These old schemes were established over long periods of time. Some of them are showing severe symptoms of ageing which makes their renewal, modernization and rehabilitation essential.
Ageing is not the only problem which faces managers of old irrigation schemes. Fast-growing populations, especially in developing countries, necessitate the improvement of the systems in order to raise efficiency and reduce water losses to a minimum. Conservation of water saves the quantities required to implement horizontal expansion through the reclamation of new lands.
Egypt has one of the oldest irrigation systems in the world. However, in view of the historical importance of the major source of water in the country, the River Nile, the irrigation scheme is still functioning with remarkable levels of efficiency.
The pressure of growing population and the need to raise food and fibre production, plus the fear of continuous ageing of the conveyance network and control structures, require utmost care towards regular maintenance and modernization of the system.
Regular maintenance of the irrigation system in Egypt is carried out during the winter closure when almost all the conveyance and distribution network is closed for a period of two to three weeks. The winter season is chosen because of suitable weather conditions and the possibility of having rainfall which compensates for irrigation water.
Modernization of the irrigation system has been continuously taking place by replacing some of the elements of the scheme and by adding new elements according to the actual requirements.
The Egypt Water Use and Management Project (EWUP) started in 1978. The aim of the project was to investigate the possibilities of modernizing the irrigation system both at the delivery and farm levels through the implementation of a research programme on an experimental scale.
FIGURE 1. High-level concrete-lined mesqa
FIGURE 2. High-level low-pressure pipe line mesqa
This programme lasted for more than five years. The results of EWUP were applied to a number of pilot-scale irrigation improvement projects (IIP). The experience gained from IIP was further extended to a larger area of about 400 thousand feddans (1 feddan = 0.42 hectares) which is now under improvement.
Following this stage, the country will be prepared to go ahead with the improvement of the irrigation system in the whole area of the old lands, which is about six million feddans.
The purpose of this paper is to touch upon the objectives of irrigation improvement in Egypt. The main components of improvement are brieflyexplained. The change from the rotation system to the on-demand system is discussed in detail showing the merits and limitations of each.
THE IRRIGATION IMPROVEMENT PROJECT
The Egyptian experience
As mentioned earlier irrigation improvement in Egypt came as a result of intensive research on the experimental field scale and also on the actual implementation of improvement projects on the pilot scale.
The main concepts of irrigation improvement as carried out on the above two scales were as follows:
Substitution of earth mesqas by lined mesqas or low pressure pipelines
The continuous cleaning of field channels called mesqas from aquatic weeds and sediments causes the geometry of the cross section to change and the canal to be wider and deeper which affects its hydraulics and water regime.
In order to bring such mesqas back to the design characteristics, the cross-section is first backfilled, straightened, excavated to the required cross-section and a concrete lined mesqa is constructed.
The advantage of lining is three-fold: (i) to reduce evaporation from the smaller free water surface; (ii) to reduce seepage losses to a minimum; and (iii) to add a new area of land either for cultivation or for the formation of farm roads.
In some locations low pressure pipelines were installed in order to completely eliminate losses through evaporation from the free water surface, and seepage.
Figures 1 and 2 show details of a lined mesqa and a low pressure pipeline respectively.
Replacement of multi-point lift by one point lift
The philosophy of irrigation improvement was different. The new idea was to substitute the multi-point lifts along the mesqa by one point lift at its offtake. Because water is elevated at the beginning, abstraction along the mesqa can be carried out by farmers under the effect of gravity.
The advantage of the one point lift is two-fold: (i) it improves the hydraulics of the flow and therefore minimizes its sedimentation/scour characteristics; and (ii) it saves energy due to the reduction in fuel consumption from the large number of pumps along the canal to one single pump at the offtake.
Formation of water users’ associations
Since the raised mesqa is operated through a single point lift, the number of farmers whose lands are served by the mesqa have to share the management of its water.
The farmers are required to: (i) purchase the pump; (ii) hire a pump operator and pay his wages; (iii) pay for the cost of fuel and maintenance; and (iv) charge every farmer according to his/her share of land served by the pump.
FIGURE 3. Water surface profiles for downstream control with level top canals
The formation of water users’ associations is also important with respect to the maintenance of mesqas (repairs of concrete, cleaning of sediments and aquatic weeds, levelling of embankments, etc.) and with respect to the fair distribution of water to the farmers along both sides.
Substitution of upstream control by downstream control
Upstream control was and still is practised on a large scale in almost all irrigation systems. The clear advantage of upstream control is its simplicity of manual operation which mainly depends on human supervision.
Limitations of upstream control include the difficulty of matching between supply and demand and therefore, the possibility of having water shortages and water surpluses. The second limitation is the difficulty of determining the lag time during which water is conveyed from the source to the field gate taking into consideration the abstraction of water by individual farmers. Third, upstream control gives the upstream branch canals and upstream farmers priority over the tail end part of the system.
This means that the tail end canals and farmers will not be allowed to irrigate unless the upstream part has fully obtained its requirement.
Downstream control enables to overcome such a limitation if: (i) farmers follow the appropriate rules; and (ii) the system is equipped with proper control structures and gates.
Furthermore, downstream control can be used to improve the storage characteristics of irrigation canals as shown in Figures 3 and 4.
Irrigation Advisory Service
Farmers in old irrigation schemes inherit their practices from one generation to the other. The change of these practices cannot take place unless there is a professional contribution of technology transfer, which shows the advantages of changing from the old system to the new ideas.
FIGURE 4. Automatic self-operating gate
One of the achievements of IIP is the formation of the Irrigation Advisory Service which is simply an extension service in the field of water use.
The use of improved elements of the system is explained to the users and the importance of rational use of water is always emphasized.
CHANGE FROM FIXED ROTATION TO CONTINUOUS FLOW (On-demand System)
Irrigation rotation
Irrigation rotation is defined as the provision of water to the lowest level of the canal system (distributary canals) from which farmers directly abstract water to irrigate their fields, during a certain period of time called the “on” period and the closure of water from the same during a similar period called the “off” period as shown in Figure 5.
In order to achieve the above requirements the area served by the feeding canal is divided either into two portions of almost equal area served or to three equal parts. The first is called the dual (two turn) rotation and the second is called the three turn rotation.
Irrigation rotation has the advantage of reducing evaporation and seepage due to the availability of water only during half or one third of the total time. This also relieves the drainage system and minimizes the effect of sedimentation and scour. The “off” period enables the operators of the system and the farmers to carry out other activities.
However, irrigation rotation has the limitation of being a fixed schedule that cannot be changed with the change of climatic conditions, crops and/or soil types. This means that the important part of irrigation, that is, when to irrigate, has only one answer: during the “on” period; regardless of the actual needs and requirements of the crops.
Continuous (on-demand) flow
FIGURE 5. Rotation system
The main objective of continuous flow is to provide water in the distributary canal continuously in order to meet the requirements of each farm at the appropriate time according to the actual needs.
The prevailing idea of water management engineers is that farmers usually over-use water for irrigation especially when they do not pay the cost of this water. However, the experience shows that this is only true for a short period of time at the beginning of the application. Farmers usually realize that over-irrigation causes more harm than good if it is continued for a prolonged period of time.
When the cropping pattern is diversified, some crops might need to be irrigated once every rotation, others might need to be irrigated every second rotation and others might need to be irrigated once every three rotation periods. However, farmers raising three crops might irrigate every rotation because they suspect they will not get the water in due time and when the plants actually need it.
Continuous flow also has the disadvantage of increasing evaporation and seepage and the consequent problems of drainage plus the fact that canal cross-sections are increased due to the conveyance of more water than in the case of rotational flow.
Field observations
Following are the results and evaluation of a study conducted by EWUP in El-Mansuriya, Giza Governorate on the comparison between irrigation rotation and continuous flow.
The two systems were compared with respect to nine aspects, these are:
Water savings
Figure 6 shows a comparison between the measured flows of an improved (lined) canal, an earth canal and the crop water requirements as computed by the well known equation of Blaney and Criddle all expressed in mm/day and in m3/feddan/day.
FIGURE 6. Discharge in improved and non-improved canals compared with consumptive use
It is clear that the earth mesqa follows the same trend of crop water requirements with the efficiency in summer being close to 75-80% and falling in winter to less than 25%.
The lined canal shows fairly high efficiency in winter (October, November and December) while a clear deficit is observed during the summer months (July through to September). The reason could be the fact that conjunctive use of groundwater is practised on large scale due to the raising of sensitive crops such as vegetables.
However, the figure shows that lining of irrigation canals strongly reduces losses and increases water savings.
Acceptability to farmers
The results of a survey carried out in irrigation improvement regions showed that 55% of the farmers preferred the continuous flow system in comparison with 45% who preferred the rotational system. Most of the farmers who preferred the rotational system did so becasue water levels in the canals during the “on” period are higher, which would allow farmers with low-lying lands to irrigate their fields by gravity. It would also mean more water available for farmers at the tail end of the canal and an excessive amount of water for those at the top reach.
Equity of distribution
Figure 7 shows a comparison between an improved distributary canal and its branches and an unimproved system and its branches. The figure shows that, in addition to the equitable distribution between the branches of the improved canal; the cumulative discharges are larger which means that losses in this case are smaller than those of the unimproved branch.
From the above results it appears that continuous flow irrigation can alleviate the problem of unequal water distribution if it is accompanied with an organized programme for cleaning and maintenance in order to make it fully effective.
FIGURE 7. Equity of distribution between improved and non-improved canals
Irrigation interval
In a continuous flow system farmers may irrigate whenever they feel their crops need water subject to coordination with their neighbours.
Table 1 shows a comparison between the length of irrigation intervals. The irrigation rotation is four days “on” and eight days “off”.
The table reveals that for 25% of the time farmers on the rotation system irrigate twice during the “on” period (irrigation interval less than four days), this did not take place under continuous flow.
For irrigation intervals between (5-8) days and (9-12) days the percentage in continuous flow is 21% and 32%, while the percentage in rotational flow is 14% and 33% respectively.
For intervals between (13-16) days and (17-20) days the percentage in continuous flow is 20% and 20% compared with 16% and 2% in the rotational flow respectively.
TABLE 1
Intervals between irrigation
|
Length of Interval in Days
|
Continuous Flow System Canal |
Rotational Flow System Canal |
||
|
No. of Irrigations |
% of Total Irrigations |
No. of Irrigations |
% of Total Irrigations |
|
|
4-Jan |
- |
- |
31 |
25 |
|
8-May |
25 |
21 |
17 |
14 |
|
12-Sep |
37 |
32 |
41 |
33 |
|
13-16 |
23 |
20 |
19 |
16 |
|
17-20 |
24 |
20 |
3 |
2 |
|
21-24 |
7 |
5 |
8 |
7 |
|
25-28 |
1 |
1 |
- |
- |
|
29-32 |
1 |
1 |
- |
- |
|
33-36 |
- |
- |
1 |
1 |
|
37-40 |
- |
- |
- |
- |
|
40 |
|
- |
3 |
2 |
|
Total |
117 |
100 |
123 |
100 |
This picture shows that with continuous flow farmers tend to increase the time span of the irrigation interval which means less number of irrigation gifts for the same crops and consequently less cost of irrigation. It can also be noticed that since 57% of the irrigation in the rotational canal has occurred at intervals which are not multiple of 12 (length of “on” and “off” periods), water must have been taken unofficially from canal storage, gate leaks, drains, or groundwater reserves.
Land savings
With the application of continuous flow, it was possible to reduce the cross section of the canal by two thirds, thereby saving a considerable amount of valuable land for cultivation or for the formation of roads and embankments.
Effect on water table
Figure 8 shows the average water table in three successive years following the change from rotational flow to continuous flow. The figure shows that the groundwater table has dropped 30 cm between year 1 and year 3 at an average of 10 cm/year.
Effect of seepage from canals
In addition to the fact that seepage from lined canals is less than that from earth canals, the lowering of water level due to the application of continuous flow reduces the possibility of seepage further. The advantage of requiring smaller cross section of both distributary canals and mesqas decreases water loss from seepage as well.
Growth of aquatic weeds
Continuous flow which has no drying period may encourage weed growth in the canals. However, the lining of canals appreciably reduces the possibility of weed growth. In the mean- time the leakage from the gates of the unimproved canals makes the dry period not sufficient to have any noticeable affect on weed growth. It can also be added that the reduction of the cross section and the lining effect which reduces friction losses increases the velocity which inhibits the growth of weeds.
Crop yields
One of the major achievements of improvement projects is the lowering of the groundwater table and more important the avoidance of large fluctuations.
The supply of irrigation water according to the actual requirements of the crops and when needed by these crops improves the water use efficiency and consequently increases crop yields.
BIBLIOGRAPHY
El Kady M. et al. 1982. The rotation water distribution system versus the continual flow water distribution system. EWUP Technical Report No. 20, April 1982.
El Quosy D.A. 1995. Control System Through Water Level. Proceedings of Tokyo Symposium of Sustainable Agriculture and Rural Development Tokyo, Japan 27-29 November, 1995. pp. 313-327.
El Quosy D.A. et al. 1996. Water Users Association: Role and Rate of Adoption. Proceedings of the 16th International Congress on Irrigation and Drainage Cairo, Egypt, 15-22 September 1996.
El Quosy D.A. et al. 1996. Farmers Participation and Free Cropping Pattern. Proceedings of the 16th International Congress on Irrigation and Drainage Cairo, Egypt, 15-22 September 1996.
El Quosy D.A. et al. 1996. The Irrigation Advisory Service: A Proper Extension Tool. Proceedings of the 16th International Congress on Irrigation and Drainage Cairo, Egypt, 15-22 September 1996.
FAO. 1993. Structures for Water Control and Distribution. FAO, Rome.
Goussard, J. 1993. Automation of Canal Irrigation System. Working Group on Construction, Rehabilitation and Modernization of Irrigation Systems, ICID.
Nour El-Din, M.M. 1995. Design Guidelines for Automatic Irrigation Delivery Systems. Irrigation Improvement Project, Ministry of Public Works and Water Resources, Egypt.
Rogers, D.C. 1988. Operation of Canal Systems. US Bureau of Land Reclamation.
World Bank, 1994. Modern Water Control in Irrigation: Concepts, Issues and Applications. Washington D.C.
A. Brolsma
NEWMASIP Manager, EUROCONSULT, Khon Kaen,
Thailand
NEWMASIP APPROACH
Project background
The North-East Water Management and System Improvement Project (NEWMASIP) is one of six projects funded by the European Commission and the Royal Thai Government (RTG) which aim to develop (dry season) cash cropping alternatives for farmers in North-East Thailand. NEWMASIP’s project objective is to increase farmers’ net incomes on a sustainable basis in ten existing irrigation schemes (Figure 1). The main constraints affecting agricultural productivity and farmers’ incomes on the NEWMASIP irrigation schemes are inappropriate and generally infertile soils; deteriorated and incomplete irrigation infrastructure, particularly at tertiary level; lack of experience, unfamiliarity with options for diversification and marketing; uncertain dry season water supplies; poor development of farmers’ organizations and inadequate extension services.
NEWMASIP is a multi-disciplinary project; its activities include: erection of buildings (e.g. training centres); purchase of equipment (e.g. for operation and maintenance of irrigation systems); rehabilitation, completion, and modernization of irrigation infrastructure; optimizing water management and improving maintenance; developing agricultural potential, including marketing, developing farmers’ institutions (e.g. Water User Groups); and training. The project budget is Baht 1 500 million (ECU 48 million, equivalent US $ 60 million). The project is implemented in seven years (1991 to 1998). The responsible agency in RTG is the Royal Irrigation Department (RID).
Approach to achieve the project objective
NEWMASIP’s approach to the attainment of the project objective of sustainable and increased farmer incomes is schematized in Figure 2.
A study commissioned by the Project on farmer group formation and strength concludes that strong groups are those where water security has been achieved and good group management is in place. Experience shows that when strong groups are challenged by (crop) production opportunities and alternatives in their schemes, optimal (dry season) cropping will result because of the business acumen of the farmers: increased farmer incomes will be the result.
FIGURE 1. Location of the NEWMASIP irrigation schemes
FIGURE 2. NEWMASIP approach to achieve project objectives
Sustainability at scheme activities level will lead to sustainability at results level; sustainability at results level creates the conditions for sustainability at (scheme) activities level. To get this cross-fertilization process moving, NEWMASIP concentrates its project resources on the activities level through investments in irrigation infrastructure and (temporary) inputs in staffing and know how in the fields of water management, operation & maintenance and agricultural, marketing and institutional development.
Farmer participation is being encouraged as a theme throughout NEWMASIP activities. For instance, farmers are being brought into the scheme management structure through participation of farmer leaders in Scheme Working Groups, where they will work with RTG officials on planning and implementing the operation and maintenance of the irrigation system, and agricultural production and marketing.
Water security
Irrigation infrastructure is being rehabilitated, improved, and extended.
Water management is being rationalized through training and improved or new software, leading to equity in distribution.
Scheme operation training aims at sharing responsibility between beneficiary farmers (groups) and RID scheme staff, leading to cooperation and trust.
Maintenance of scheme infrastructure, of prime importance for sustainability, is being shared between farmers (group) and RID, with resources coming from both farmers and Government.
Developing and strengthening groups
Leadership is being developed through training in meeting techniques, planning, cooperation and accounting aiming at fair and democratic leadership.
Rules, regulations & sanctions are addressed in group meetings and training aiming to achieve a simple and clear institutional structure which is open and creates cooperation and trust in the management amongst the participants.
Agricultural alternatives/cropping opportunities
When pursuing the aim of agricultural intensification and increased farm incomes, the Project and the cooperating RTG agencies can only suggest alternatives and facilitate implementation. The farmers decide what they will grow.
Agriculture and marketing assistance is given to identify, together with the groups, marketing and production opportunities and to organize specific packages of assistance which optimize the chances of success.
Though NEWMASIP has taken the lead at scheme activities level with its financial and human resources, the remaining project years are used to strengthen the scheme training teams (RTG field staff) and to gradually fade out from active implementation to facilitation and monitoring roles, such that no break will occur at the end of the Project.
The sustainability cycle, thus having been started with project resources, would maintain its momentum as a result of the (initial) success in production.
Inputs to achieve the objective are:
Investments in ‘hardware’: 90% of project funds are used to improve water delivery to the field:
- investments in Main System rehabilitation/improvement‘Software’: 10% of project funds are used for formal-and field training of office-and field staff of RTG-agencies and farmers in order to achieve sustainable:
- investments in On-Farm Development
- investments in (training) buildings and equipment
- improved water management and operation and maintenanceIrrigation system rehabilitation and modernization
- agricultural development and marketing
- institutional development at scheme level
Within the limits dictated by the existing irrigation infrastructure, its condition and its adequacy, the design criteria for modernization/improvement are governed by the operation and maintenance (O&M) model selected for the future. In NEWMASIP, a high degree of farmer participation in O&M is foreseen and the designs aim at “user friendliness” (simple to read and adjust), and ease of maintenance; only existing, simple and proven technology is used.
NEWMASIP has opted in all its schemes for upstream water-level control with:
This not very revolutionary but modest approach to modernization has been selected for the following reasons:
System modernization in terms of more sophisticated water level and flow control structures runs contrary to NEWMASIP’s aim of increased farmer participation in operation and maintenance.
Based on above (re) design criteria rehabilitation, improvement and extension of irrigation infrastructure took place on all seven Medium Scale Irrigation Schemes for 100% of the area, and on pilot areas of approximately 20% of the Large Scale Irrigation Schemes totaling 170 000 rai (27 000 ha).
Farmer participation
Farmer participation is considered the key to the sustainability of the project results. Thus, the Project has promoted farmer involvement in:
Key players in bringing about this involvement are the Irrigation Community Organizers and the Agricultural Technicians, project staff stationed at the schemes for most of the duration of the Project. They are the day-to-day link between the Project Management Unit (PMU) at head quarters in Khon Kaen and between RTG field staff and farmers. Participation in design means that water users participated in walk-through surveys of the schemes to inventory and assess the repair and improvement needs of existing infrastructure and record remarks on preferred tertiary layouts and on drainage problems. Where complete redesign was needed, the designs were explained to the farmers and based on their comments (and if feasible), changes were made to alignments, design levels and location of offtakes. During construction, either by Force Account or by contractors, local farmers were the preferred labourers allowing them to get familiar with construction practices and to act as ‘quality supervisors’. In some cases farmers organized their own supervisory groups, checking even at night, to be able to report on suspected low quality work by contractors.
NEWMASIP sets up or transforms existing water user organizations, from the tertiary or ditch level up to the lateral and scheme levels: Water User Group, Lateral Group and Scheme Working Group. Three functions are catered for by the Groups: water management, production coordination and marketing coordination. In full development, the group strengthening process should culminate in legalization of the status of the water user organization i.e. to become a Water User Association or Water User Cooperative, with a complete set of rules and regulations as developed and agreed upon by the members. Four out of the ten project schemes now have Cooperatives and Associations.
To increase the farmers’ sense of ownership of the tertiaries, and to motivate them to take proper care of the tertiaries, NEWMASIP organizes handing-over ceremonies both of newly constructed tertiaries and of existing tertiaries after rehabilitation. Special certificates are printed for the occasion, together with a map of each tertiary, list of the water users and the Water User Group leaders, and documents relating to the operation and maintenance of the tertiaries. A party is organized with food and drinks to celebrate the occasion.
Farmer cooperation in groups strengthens their bargaining power with agricultural contractors and middlemen as well as with RTG department staff assigned to assist them. It also fosters a sense of belonging and ownership, crucial for their willingness to participate in operation and maintenance of the infrastructure.
NEWMASIP EXPERIENCES
In this section, experience with farmer participation and group formation will be presented and then a first evaluation of design criteria and the approach in the light of the initial success with farmer participation will be attempted.
Experience with farmer participation
Scheme infrastructure rehabilitation and improvement started to be completed from the third project year onward and is continuing to this day. Experience with farmer participation and group strengthening is therefore limited to two years only and not for all ten schemes.
Overall, farmer participation has been high and many farmers are dedicated to the groups and the new functions of the groups. The scheme training teams (RTG field staff) were trained by the PMU, one training team for scheme O&M, one team for production and marketing. They then trained and assisted in the formation and functioning of the different groups. The production and marketing functions were strengthened through farmer exchange visits and skill training workshops with the participation of agricultural contractors. This did result in a substantial growth of production contracts with the private sector. As a result, the groups became more attentive to water use planning and cooperation within-and with other groups. This also led to an increased willingness to participate in scheme operation. With the schemes being recently rehabilitated, little experience with maintenance participation does as yet exist.
One conclusion seems to stand out already: water user organizations must be multi-purpose (not only an O&M function). The farmers will not take up O&M activities if they are not involved in income generation activities as well. Once they are, the group management has shown keen interest in costing O&M activities and in negotiating with the group members for contributions (fee collection).
On the downside of above rather rosy picture, much of the initial training in water management and the O&M function had to be based on theoretical figures and it has become obvious that (much) more practical, on-the-job training will be needed. The willingness of RTG field staff to relinquish (part of) their involvement in water management and scheme operation to the farmer (group) cannot be taken for granted and largely depends on a proven track record in farmer-official cooperation and trust in quality. To achieve this, more time is needed.
Experience with system rehabilitation and modernization
The experience with system rehabilitation and modernization so far is a rather mixed bag. Though designs, rotation schedules and operation procedures were addressed in many training sessions and meetings, not all farmers readily understood the technical explanations and pictures. Dissatisfaction of certain farmers cannot be avoided in this way and modification and interference of structures by some farmers is still a regular occurrence. Physical models of structures will be built for demonstration of operation.
Construction quality and adherence to designs was a problem on a number of schemes as the ability of RTG field staff and farmer representatives to correct below standard performance by contractors is limited. Preparation of as-built drawings is therefore a must on which to base the water management and operation manuals for the schemes.
Movable checks have been provided for use by every farmer of the ditch. As no farmer in particular is responsible for the check, they sometimes disappear.
Many more years of practical on-the-job experience and continued monitoring and refresher courses will be needed before a final evaluation of the adequacy of the design criteria of ‘user friendliness’ can properly be made.
Experience with the approach
For those farmers who are interested in dry season cropping, the (initial) enthusiasm to join in water user organizations and its activities has been promising (see Experiences with farmer participation above). Fewer than 10% of those farmers report water security as a main constraint to agricultural production.
Dry season contract farming by groups (tomato, baby corn, lemon grass) did start on four of the schemes and vegetable production for the free market on three schemes. As a result, water user groups in these schemes have grown in confidence, raising the hope for future sustainability.
More time for learning and gaining of experience will be needed with continuing monitoring and support before the groups and their ability to make money in the dry season can be considered to be sustainable. The final evaluation of the adequacy of the project approach therefore cannot as yet be made: the verdict is still out.
SOCIO-ECONOMIC CHANGE
The context: Socio-economic change in Thailand
Socio-economic change in NE Thailand should be viewed in the context of economic change in the whole Kingdom. In 1985-1995 Thailand was the fastest growing economy in the world, with an average annual growth rate of over 8%. Per capita incomes are doubling every 12 years. However, growth rates vary widely between regions within Thailand.
Thailand is classified by the World Bank as a ‘newly-industrializing economy’ (NIE), and as one of eight ‘high-performing Asian economies’. The Thai economy is characterized by macro-economic stability, a high share of GDP in international trade, strong competition among firms, high investment and savings rates, and modest inflation rates. Thailand is also be classified as a ‘newly agro-industrialized country’, in the pattern of food exporting industrial countries such as France and The Netherlands, and is already the world’s ninth largest net food exporter (one of only two in Asia, the other being Vietnam).
The proportion of people living in urban areas has risen to more than 20% in the 1990s, and the rate of urbanization will continue increasing as the manufacturing sector grows faster than agriculture. As recently as 1960, the agricultural sector was the most important in the economy, accounting for 40% of GDP, but this share has fallen to less than 10% in 1996. The decline has not been absolute, but relative, due mainly to the phenomenal growth of the industrial and services sectors.
Exports were once dominated by agricultural produce, but the sector now contributes only about 20%, whereas 70% comes from manufacturing. Rice used to be the largest export item, but was only 8th in 1994 after garments, computers and parts, frozen prawns, integrated circuits, gems and jewelry, rubber, and footwear.
Thailand faces strong competition in the long term from other NIEs such as Malaysia and Indonesia, as well as from emerging NIEs like Viet Nam. However the greatest competition is likely to come from India and China, the world’s two most populous countries. China is already the world’s third largest economy, and has labour costs that are much lower than Thailand’s. NIEs such as Thailand are at an intermediate stage of development and therefore find it difficult to compete with the industrialized countries, which have higher technology and better educated work forces; and also with the emerging economics which have much lower labour costs.
Under-investment in human capital might become a serious constraint to future growth prospects. About 80% of the work force has only primary education. As recently as 1960 it was estimated that 82% of employment was in agriculture, but by 1994 this had fallen to 58%. However, productivity in agriculture, as measured by GDP per employee, has been about 10% of that in manufacturing during the period 1970-1994.
Socio-economic change in NE Thailand
NE Thailand (Isan) has long been regarded as the poorest and most neglected part of Thailand. Poor soil and erratic rainfall have left it sparsely populated. With poor natural resources and minerals, the region has been relatively unsuccessful in attracting investment. In the early 1990s 35% of Thailand’s population was in the NE region, which produced only 13% of the country’s GDP. In contrast, Bangkok had 16% of the population and produced 48% of GDP. This great difference resulted from slower economic growth in the NE, because the region has a small proportion of the country’s industry.
Regional per caput income for NE Thailand has increased, but at a slower rate than in other regions of the country, so Isan has become relatively poorer. However, in absolute terms the incidence of poverty has decreased.
Migration
Migration has long been a feature of rural life in Isan, originally to seek new and better land to farm and more recently in the form of seasonal movement to seek work in the dry season. Since the 1960s migration has tended to become more permanent as rural people seek stable wage-earning opportunities in factories, construction, and other urban occupations.
Typical migrants are young and unmarried, either male or female. Longer term migration is characteristically by the younger and better educated people.
Causes of migration include both ‘push’ factors which are related to the relatively poor living conditions and opportunities in rural areas; and ‘pull’ factors related to the economic and social attractiveness of urban life.
Farming systems
In general profitability is being severely ‘squeezed’ by rising input costs and static output prices for farm products, which have little prospect of increasing.
Rainfed farming systems are still dominated by (a) subsistence paddy production, which is economically attractive in view of the big difference between the farmgate and retail prices;(b) cassava, for which prices are currently higher than in previous years and (c) sugarcane, for which the planted area is expanding, often causing serious soil erosion.
Irrigated farming systems are still dominated by rice in the wet season, while in the dry season cropping intensities are generally low. The best prospects are for seed crops, vegetables, fish and shrimp ponds.
Farm income
Statistics since the mid-1980s have shown that farm households typically derive only one third or less of their incomes from their farms. Remittances from wage-earning family members make up the most important component of off-farm and non-farm income, and are growing in importance.
There is anecdotal evidence (although as yet little statistical evidence) suggesting the farm holdings are becoming fragmented in terms of ownership. Land speculation is rife around cities and towns. The number of former farmers who have no land will probably increase.
Farm labour
The amount of labour available for farm work is being reduced by seasonal and permanent migration, and by children increasingly (and compulsorily) attending school. Children used to contribute 10-20% of the labour required for farm work. Because migration mainly involves ‘newly economically active’ younger people, the rural labour force is becoming older. This might mean that labour intensive farming will become less attractive.
Hired labour resources and wages
It was estimated in 1960s that even in the busy wet season months 20-25% of the agricultural labour force was under-employed. The World Bank (1990) commented on ‘quite impressive’ employment growth in the NE, and that ‘job opportunities in agriculture and commerce grew more quickly in the Northeast than in the rest of Thailand’.
The pool of under-employed labour seems to have disappeared in the late 1980s, resulting in a sudden increase in wages of hired labour from B30/day in 1988/89 to over B100/day in 1995/96, an annual increase of about 25%. Labour is often difficult to find, and has to be offered non-wage inducements such as food, whisky and cigarettes.
Rural living conditions
The rural population is becoming unstable due to permanent and temporary migration. Villages are becoming de-populated, and may increasingly be seen as unattractive places to live. Young people who have experienced urban life may be reluctant to stand in paddy fields transplanting rice on the family farm. It has been argued that the strong cultural links with the rice producing ‘home farm’ will weaken and disappear within another generation.
Summary of rural changes
The ability of the agricultural sector to compete for resources is weakening. Both labour and capital resources increasingly find more productive and more rewarding opportunities in the non-farm sectors. Moreover structural problems such as inadequate land documentation, incipient fragmentation of land holdings and input prices which are relatively high compared to output prices for farm products create a difficult environment for rural development.
Impact and response to labour scarcity and rising labour costs
Most of the farming activities being promoted by the Project require relatively high levels of labour input, and they require attention over a larger proportion of the year than is normal for most Thai farmers. One of the attractions of planting cassava in particular is that it needs little care between the peak labour inputs for planting and harvesting and meanwhile the farmers can work or amuse themselves as they please. In contrast integrated agriculture on irrigation schemes and high-quality fruit and vegetable crops require the farmer to be on the farm for most of the year, with relatively large inputs in terms of the numbers of mandays per rai. Moreover increasing production and, especially, improving the quality of farm produce traditionally means increasing labour inputs, which is problematic at a time of increasing labour shortages and rising labour costs.
As shown in para Socio-economic change in Thailand above, labour costs are rising rapidly and will quickly erode the profitability of even the most attractive farming enterprises.
From the monitoring information available for the various NEWMASIP schemes, it is already known that dry season cropping intensities are low and that little improvement has been recorded since the rehabilitation of these schemes was completed. Moreover, when such improvements have been recorded, these have been considerably less than expected.
Dry season cropping intensity of high value crops is the single most important planned project result, the outcome of which makes or breaks the return on the investments in irrigation system rehabilitation/improvement. Wishing to get an insight into farmers dry season cropping interest, the Project conducted a special survey on two schemes where rehabilitation, improved water management, and agricultural, marketing and institutional development activities had been conducted in previous projects and the dry season cropping opportunities had been optimal for over many years.
In the Lam Nam Oen irrigation scheme, the average 1996 dry season cropping intensity in our sample was 16%. For the whole project and in previous years, dry season cropping intensities of between 0-15% have been recorded including rice. Rice is now not grown as it is discouraged by RID and the 15% intensify of non-rice crops is the highest level achieved so far.
In a part of the Lam Pao irrigation scheme which had previously been rehabilitated, the average 1996 dry season cropping intensity in our sample was 35%, 19% for rice and 16% for high value crops.
In the samples of both schemes, around 35% of the farmers did not grow any dry season crops at all, around 13% grew crops on all their land and 52% of the farmers only on part of their land.
When asked about the reasons for not growing crops at all or on more of their land, a hefty 50-70% of the farmers identified (family) labour availability as the main constraint. Irrigation constraints were considered problems by 10-20% of farmers and problems regarding unsuitable soils, pests, diseases and insect infestation were mentioned prominently as well. Dry season cash crops other than rice are generally considered relatively risky crops as farmers are never confident that the demand and the price will be sufficient to guarantee a sufficiently high net income to compete with other types of less risky off-farm income generating activities. Some high value cropping alternatives (e.g. tomatoes) can suddenly disappear if the market goes sour, or the processing company goes bankrupt, further depressing the dry season cropping intensity and farmer confidence in the market.
Labour scarcity and rising labour costs have led to progressive mechanization; already 90% of the farmers use 2- and 4- wheel tractors for land preparation, and combine harvesters and threshers are making inroads. Mechanization means capital investments, however, and crop revenues hardly justify such investments at the current commodity prices.
In summary, the changing socio-economic environment of NE-Thailand and the resulting low interest in dry season cropping destroys the economic justification of investment in irrigation system rehabilitation and improvement in the North-East. When 65% to 90 +% of the land where dry season cropping is technically feasible is left fallow, no economic justification for 100% rehabilitation is possible.
It may be that the Government is prepared to consider investment in irrigation system (rehabilitation) as a subsidy to those farmers who (continue to) try to make a living from the land. If they don’t, other ways for irrigation development need to be found, for instance partial rehabilitation on part of the area only, and only if high value dry season cropping interest has been established.
FUTURE OPTIONS
Over 60% of the farmers with irrigated land where dry season cropping is technically feasible (enough water) engage in dry season cropping, though most use only part of their land (see preceding chapter). Especially for high value crops, they must consider the returns to labour to be acceptable and combined with other reasons for wishing to stay on the land, good enough not to join in the outward migration (as yet).
For the Government and donors who join in irrigation system development in the NE, however, it must be disheartening to see most of the irrigation areas left fallow in the dry season. And where no money is made farmer interest in system maintenance is bound to be low, continuing the cycle of rehabilitation and decay.
With current and projected rice prices, the economics of rice cultivation are bad. Most farmers in the NE grow (rainy season) rice for subsistence reasons only, and on irrigated land in the dry season if the preceding harvest fell short of expectations. Also, the yield differences between rainfed rice and rice with supplementary irrigation are in average too small to justify investments in irrigation. Economic justification for irrigation development can only come from high value dry season cropping on most of the land where this is technically feasible (enough water), and even then the returns do not justify large amounts of capital investments.
Irrigation system development, rehabilitation and improvement (modernization) is not a goal in itself; it is a means to achieve higher agricultural production, productivity, and increased farm incomes. If the latter can hardly be achieved, the rationale for irrigation development disappears.How then does the future look for agriculture in general and irrigated agriculture in particular in the NE? In Europe with artificially high commodity prices and protected from international competition; with mechanization and industrialization of agriculture, dramatic increase of farm sizes, high levels of education and professional support services, agriculture employs 5-10% of the total work force at acceptable levels of income.
Thailand is not likely to follow the European example of a closed agricultural economy. Thai farmers can expect to continue to face world market commodity prices and cannot expect to look the same in one-or two generations from now. Extensive farming may be one option, together with mechanization and land consolidation. As in Europe, large tracts of land may revert to different uses: recreation and forestry for example. Only the future can tell.
Future options for irrigation rehabilitation and development
In NEWMASIP rehabilitation and improvement of irrigation infrastructure took place on 100% of the irrigation area, even if the reservoir capacity allowed dry season cropping only on 10% or 20% of the land in four out of five years. The supplementary irrigation option during dry spells in the rainy season was the only justification for 100% area rehabilitation.
As expanded above, dry season high value crops are the only means of giving the farmers an acceptable return to labour. A shift toward integrated, diversified, value intensive farm enterprises should therefore be encouraged and for this time, training and commitment is needed. Government (and donor) support in ‘software’ activities should therefore take precedence over continued investments in irrigation infrastructure. Investments in agricultural and marketing development and in institutional development and training are likely to show much higher returns than investments in ‘hardware’ which is only partially used: first valorize the infrastructure which is already there.
Before rehabilitation and modernization of irrigation infrastructure is considered, dry season water availability needs to be assessed. If water availability limits dry season cropping to for instance 20% of the area, consider to rehabilitate only the upstream areas of the schemes and only the better soils. Even if water availability would allow 100% rehabilitation, the partial rehabilitation option should be considered for the reasons expanded upon in the previous chapter. Those farmers who wish and are capable to grow high value dry season crops may well find ways of securing irrigated land in the rehabilitated areas.
In summary:
ACKNOWLEDGEMENTS
This paper is based on the reports produced by the NEWMASIP technical assistance team and by its volunteers and students.
A. Yoshida
KURIMOTO Ltd., Osaka, Japan
BASIC CONCEPTION OF CONTROL OF IRRIGATION WATER DISTRIBUTION
Fundamental rules on irrigation water management
It is fundamental in irrigation water management to ensure that there is the necessary quantity of water to be distributed impartially among the users. Importance is laid on ensuring water resources from which water can be taken in sufficient quantities for not only meeting the demand for irrigation but also making up conveyance and distribution losses even in water shortage periods.
Where water resources are plentiful
Where water resources are plentiful, water is taken up to the full capacity of facilities and distributed in geometric ratio in accordance with the ratio of the largest quantity necessary in each irrigated region. It is a general rule to “share water impartially” even if there are slight shortages of water.
More efficient use is possible by distributing water, based on information on changes of cultivation methods and staggering cropping.
Where water resources are scarce
As the pressure of water demands increases where water resources are scarce, intake and distribution of irrigation water need to be kept under proper management through appropriate seasonal and regional control of water intake/distribution facilities. Intake should be limited to the smallest quantity that meets the users' demands in the lower reaches of an irrigation system, and water must be distributed carefully in proportion to demand. Otherwise, it is impossible to satisfy the demand for irrigation water in the whole region. “Impartially”, as mentioned above, means not only “equally” but also “in necessary and sufficient quantities.” Each user is responsible for water management so that improved efficiency of water utilization will meet the demand for irrigation water in the whole region.
Improvement of facilities and introduction of new technologies
For a careful management of water distribution, it is necessary to regulate discharge quantities properly according to seasonal and regional demands. For the purpose of timely identifying changes in demand and understanding flow regimes of canals, information needs to be collected, and facilities for irrigation water need improvement.
The recent development in communications and computer technologies has promoted the development of new irrigation technologies, including computing technology, systems science, surveying technology and optimization technology, and has created a new age for management science. It is indispensable to introduce modern technologies and latest results of management methods, in the modernization of irrigation water distribution control for the most effective use of water. Those who are involved in irrigation water management are responsible for the efficient utilization of limited water resources and the establishment of a basis for social development.
DISTRIBUTION CONTROL BY OPEN CHANNEL SYSTEM AND ITS CHARACTERISTICS
Open channel system and intake/diversion
In a gravity-type, open-channel system, water taken from a river flows down a main canal, being diverged at turnouts, like the branching of a tree, and is conveyed to the target fields.
At intake facilities (head works), water is taken from the river, being dammed up at the diversion weir to the prescribed water level and guided steadily to the intake works. Intake is regulated by maintaining the intake level on the side of the river and adjusting openings of the regulating gate at the mouth of the headrace.
In water diversion, it is fundamental to diverge water further at each block of irrigated fields. It is important that a canal system has a structure which does not divide water in small quantities directly from a large-capacity canal. Small-quantity diversion is difficult to control, and often impedes impartial distribution of water.
Regulation of diversion
Turnouts shall have, in principle, a structure which does not need control to produce constant ratio diversion at any water level. Discharge ratios are changed, where necessary, through the control of regulation facilities such as regulating gates. The flow and the distribution of water are controlled successively from the upper course of the canal, for the purpose of maintaining constant flow in proportion to intake. Regulation is carried out from time to time, with a view to adjusting the flow to meet seasonal changes in demand. A change of flow in the upper course reaches the lower course gradually, and generally considerable time is required until the flow becomes constant again.
Rules on water abstraction
As water is supplied to each field constantly and continuously, freely increased abstraction in the upper course immediately reduces water supplies in the lower reaches. Abstraction therefore needs to be well under control, and rules on water abstraction need to be established for each section of the course, by mutual agreement among irrigation water users' organizations.
DIVERSION FACILITIES AND CONTROL SYSTEMS
Distribution works
Split diversion through guide walls is the simplest method of diverging water from a main canal. In diverging water in nearly equal quantities, a geometric ratio diversion by width is conducted, by dividing the canal with guide walls. For increased accuracy, diversion is sometimes carried out through facilities which make the flow of water supercritical near a turnout and divide the supercritical flow with sharp-edged walls. Diversion ratios are changed by regulating openings of the gate constructed in each diversion canal.
The use of cylindrical diversion works is another method of increasing the accuracy of diversion ratios. In this method, water is guided to a double-cylinder canal, where its circumference is divided for the purpose of fixing diversion ratios, and water is guided to each diversion canal in diversion ratios thus fixed. Although diversion ratios can be adjusted by changing divisions of the circumference, it is difficult to adjust ratios as necessary. These control systems are used in those schemes where the already agreed practice of constant ratio diversion is observed, without necessitating the adjustment of diversion ratios. as a general rule.
Turnout
Water is diverted in comparatively small quantities from a main canal to branch channels through control equipment installed in the link canal. The simplest control is a diversion gate constructed in a branch channel. The quantity of diversion water is adjusted by opening the gate. Valved diversion pipes are also used for this purpose. It is necessary that gauging equipment is installed, for the purpose of raising the accuracy of flow regulation. Methods often employed for obtaining stable accuracy in flow regulation include the method in which the level of water is maintained constant in the main canal and water is diverged through a overflow weir constructed at the side wall of the canal. The double-orifice method is another method in which a regulating tank is constructed in the diversion pipe to diverge water. Quantities of diversion water are controlled with the diversion gate or by the adjustment of openings of the valve, and ascertained with the gauging equipment in the branch channel.
MEASUREMENT OF DISCHARGE
Water level gauge
If steady flow is produced in open channel systems, the measurement of the water level can generally show the amount of discharge (velocity, flow area) at the position of measurement. The water level is measured by reading a staff gauge, a float-type water level gauge in an observation well, or an electrode-type water level gauge.
Water measurement facilities
Where high accuracy is needed, an ultrasonic discharge gauge is sometimes used.
Where flow regimes are unstable without producing steady flow, the amount of discharge is sometimes measured by installing a Parshall flume or an overflow weir. This method is, however, not advisable because head losses are large and the range of measurement is limited.
Opening gauge
For measuring openings of gates and valves, which regulate the amount of discharge, opening gauges fitted to respective purposes are used. The amount of discharge after regulation is measured with the above-mentioned method, and openings are adjusted by feeding back the measurement results.
QUANTITY OF DIVERSION WATER AND DIVERSION CONTROL
Constant ratio diversion
In irrigation systems for paddy fields, canals are constructed for constant ratio diversion in proportion to canal capacity ratios, based on the maximum demand ratios, without special control to cope with changed intakes.
In cases of designing diversion facilities in which a changed water level of the main canal greatly affects diversion ratios, diversion works are designed and controlled so that constant ratio diversion would be easily carried out by regulating facilities.
Control of rotational irrigation
In cases where a constant ratio diversion is able to convey only small quantities of water for canal capacity, such as in an exceptional shortage of water, hour-restricted water supply is conducted on a rotational basis. In these occasions, the gates of the diversion canals are opened one after another.
Increased necessity for adjustment
Cultivation methods and land utilization have changed, with changes of social conditions. With a seasonal change of the demand for irrigation water, as well as with regional changes, it becomes necessary to adjust the supply of water carefully. Moreover, as rural regions are increasingly affected by urbanization, a more economical use of irrigation water becomes imperative.
Measures for complicated control
In an open channel system, the manager of basic facilities conducts the distribution of irrigation water by controlling intake and diversion of water. It is important for the manager to control the facilities carefully, in order to distribute water in proportion to demands. It is necessary that the facilities be improved, such as by strengthening discharge observation equipment for understanding the flow regime every moment, installing information transmission equipment, and introducing equipment for analysing control effects.
Necessity for automatic control
As conditions become complicated, the necessity for automatic control increases in the greater part of the system of monitoring, observation, analysis, judgement, instructions and the execution of control, for proper judgement and control on irrigation water distribution.
DIVERSION FACILITIES AND AUTOMATIC CONTROL
Opening and closing
The opening and closing of the gate/valve of a turnout can be shifted from manual operation on the spot to electric control in the operating room. At first, on-off switching is conducted through the monitoring of openings. Then, openings of gates/valves are adjusted in accordance with prescriptions, and later, opening and closing are automatically controlled, by setting the quantity of water to be diverged and finding the required openings through calculation.
Check gate
A check gate is constructed for the purpose of keeping the level of water constant in the main canal for ensuring stable diversion in proportion to openings. Check gates are classified into those which keep the level of water constant by means of floats and those which keep the level of water constant by means of the linkage of water level measurement and the control of openings.
Opening setting
Methods of finding adequate openings from prescribed quantities of diversion water include the method in which openings are adjusted through measuring the water level of the main canal and calculating the necessary opening. Another method uses a feedback mechanism, in which the water level in the lower reaches is measured by calculating the quantity of diversion water, and the opening is readjusted, based on the difference from the prescribed quantity. Both methods are based on the assumption that the flow of water is steady at the time of water level measurement. If the flow is not steady, it is possible to adjust openings by unsteady flow analysis based on water levels and their changes in the upper and the lower courses. It is, however, difficult to carry out a stable control.
Feedback control
In cases of systems which include feedback control, problems may occur if a too sharp control is expected, because the step control of openings and the measurement of consequent water levels are repeated. Due consideration needs to be given in designing feedback control systems.
The elements of automatic control are minor loop control at each turnout, where feedback control is carried out through water level measurement and the control of discharge at the prescribed opening.
IRRIGATION WATER CONTROL FACILITIES
Telecommunication equipment
Irrigation water control facilities include telecommunication equipment for integrated water management through monitoring and controlling facilities such as gates for regulating quantities of intake and diversion. These facilities receive information on water levels, quantities of discharge, openings, etc., measured at intake/diversion points.
Telephones and telegraphs are the simplest facilities for transmitting data either through a wire system or a radio system.
Computerization
Computers are used for data analysis and storage as well as for simulation of different water control scenarios.
Automatic control system
An automatic irrigation water control system refers to an apparatus which automatically carries out measurement, calculation, control and regulation over the full range of the irrigation scheme from the water source to the fields, by utilizing technologies of telemetry, tele-control, data transmission and remote regulation of gates and other control facilities.
IRRIGATION WATER MANAGEMENT IN JAPAN
Number of projects equipped with irrigation water control facilities
In 1994, there were approximately 5 600 major irrigated schemes in Japan, among which 211 were equipped with irrigation water control facilities. Among these facilities, 105 were for the control of water sources (including dams, head works and pumping stations) only, while 106 were installed for the control of diversion facilities.
Construction cost of irrigation water control facilities
The cost of facilities which can control irrigation water in schemes exceeding 3 000 ha amounts to about 370 million yen on average, compared with about 210 million yen on average for schemes below 3 000 ha.
Annual expenses for the management and operation of these facilities are between 0.5% and 3%.
Effects of irrigation water control facilities
These control facilities are effective in the systematic utilization of irrigation water, and allow efficient operation of dams as sources of irrigation water. They can contribute to satisfy increased demands for irrigation water systems which are subject to water shortages.
Irrigation water control facilities furthermore allow the smooth distribution of water for various uses even in water shortage periods, and make it possible to reduce extraordinary expenses for water management and prevent problems in the adjustment of water distribution.
Measures for proper management of irrigation water control facilities
Irrigation water is managed by farmers’ organizations as part of their activities for land improvement, as a general rule. Regarding those facilities which are used for irrigation water regulation over very wide areas, either the range of official management of facilities (i.e., by the national government, prefectural governments, or municipalities) is expanded, or assisting measures are taken (e.g., grants/subsidies, training for operators, or dispatch of experts).
Problems awaiting solution
The service life of control apparatus is shorter than that of irrigation facilities. Moreover, the rapid development in communication and computer technologies in recent years make the existing apparatus old-fashioned quickly. It becomes necessary that computer software be updated to meet the changes in irrigation water management which goes along with rapid social and economic changes. It is also necessary that personnel be equipped with improved skills in the operation of advanced irrigation water control apparatus. Improved methods have to be adopted for collecting and analysing data on irrigation water management. It is important to examine the efficiency and characteristics of apparatus before deciding to procure it. It is also important to choose only that apparatus, which is suited for the purpose.
MODERNIZATION OF FACILITIES FOR HIGHER LEVEL CONTROL
Management of steady flow
Although open channel systems can guide large quantities of water economically, they are attended with the restriction of flow time, because management is aimed mainly at steady flow. It is therefore difficult to meet complicated changes of water demands. It is uneconomical to carry out highlevel, automatic control at all turnouts, and doing so could damage the stability of the system.
Construction of storage facilities
Supply-oriented water management is effective in the control of water resources, but cannot completely eliminate losses from demand-supply gaps. In modernizing canal systems, it is effective to construct temporary storage facilities such as a regulating reservoir, in addition to lining of canals for ensuring the flow capacity and reducing seepage losses, as well as to improve the diversion facilities.
Employment of pipeline system in lower reaches
It is recommended that a pipeline system is employed downstream for better utilization of irrigation water. Pipeline systems, conveying water in proportion to demands, can meet individual demands and prevent spills and tailwater losses. In using a pipeline system, facilities having a regulating capacity (e.g., regulating reservoir, regulating tank or storage facilities) need to be constructed at the point where the pipeline system is connected to the main canal.
Project for diverting irrigation water into city water
In agricultural areas near cities, projects have been implemented for reducing the expenses for irrigation water management and creating resources for city water. These projects had the objective to economize on irrigation water use while meeting the rapidly increasing demand for city water at the same time. In these projects, main canals are improved, automatic control is introduced in diversion management, central control equipment is installed, pipeline systems are employed in the lower reaches of the irrigated areas, and storage facilities are constructed at divergence sections of the main canals. As onerous transfer of water rights to other uses than irrigation is not permitted in Japan, these projects are implemented in the form of joint projects, mainly with city governments’ investment in urban water resources development, together with irrigation water users’ defrayal for the reduction of water management expenses and the modernization of the whole irrigation facilities.
