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Modernization of irrigation system operational management by way of canal automation in India

Anil B. Mandavia

Chief Engineer, Management Information Systems
Sardar Saroar Narmada Nigam Limited, Gandhinagar, Gujarat, India


A scientific management culture should enter the field of our irrigation system operational management: only then the irrigation systems set up with enormous investments through the various five-year plans can be sustained to ensure reasonable returns. In India, the introduction of systems based on information technology for monitoring and controlling canal operations is necessary to improve water management not only at the operational level but also at the farm level. As the farmers are the end-users, when new technology is applied, they have to be informed during implementation of the improvements planned and of the anticipated benefits which they may gain. Upgrading existing canal system operations needs to be done in stages as a rehabilitation programme. It can be done in small areas which are easily and economically assessable for improvement. If information technology is brought to an existing water resource project, restoration of the existing control structures, canal sizing, canal lining and other related command area development activities must be completed before taking up the automation project. The cost of canal automation on an existing irrigation project and that on a new project cannot be compared, as the built-in constraints in the existing project not only limit the degree of automation but also increase the cost by way of remodelling the existing canal systems. In Indian conditions the cost of automation on the main canals can vary from Rs1 500 to Rs2 000 per hectare and that on the secondary canals from Rs3 000 to Rs4 000 per hectare. New techniques such as on-farm irrigation scheduling are available to predict the time and volume of water needed for the most effective irrigation. Specific amounts of water required for crop irrigation at particular times can be derived using the soil-water plant relationship. Soil characteristics such as infiltration rate and water-holding capacity are used in the calculation. By using soil characteristics, moisture content and estimated evapotranspiration, the timing and quantity of water needed to replenish the depleted soil moisture available to plants can be calculated and used to forecast the next irrigation. These schedules are then provided to the computer centre controlling the canal conveyance and delivery system to update the weekly and daily schedules of irrigation, which are set at the start of the season based on the available data. Thus the requirement of the release of water into a main canal can be predicted on a scientific basis and this will allow for a more flexible operation of the canal system. The linkage of real-time data collection and monitoring of climate crop-soil relation parameters with the canal automation of the conveyance and distribution system is the ultimate goal, and the use of information technology below outlet level must be given an equal priority. The socio-economic conditions of the farmers and the scientific use of water to satisfy crop requirements will determine the degree of success of the complete approach of implementing automation from headwork to farm level.


As we approach a new millennium, there are growing concerns and periodic warnings that we are moving into an era of water scarcity. With increasing demand for food and competing use within the water sector, the pressure is on irrigation professionals to manage water efficiently. The rallying cry is "more crop per drop". In response to this, strategic decisions and interventions need to be made on a continuous basis. These decisions should cover the full spectrum of the irrigation water supply system, from diversion and distribution to on-farm application down to the crop root zone.

Agriculture is the mainstay of the Indian economy; almost three quarters of the country's working population are engaged in agriculture and about half of the gross national product is generated by agricultural production. Agricultural growth largely depends on water, which is the prime input. Rainfall is not quite dependable or helpful to agricultural development in India. The Indian monsoon is known for its vagaries. Almost 85 percent of the rainfall is provided by the Southwest monsoon (June to September) and some parts of Southern India receive rain from the Northeast monsoon (November to December) as well. Rainfall distribution is uneven with respect to time as well as space, and frequently erratic. The mismatching of rainfall and crop-water requirements is quite common. A large part of the country is arid and semiarid as rainfall is not sufficient to ensure even a single crop. Furthermore, the low-rainfall areas of the country have a fairly high coefficient of variation. Droughts are experienced quite often in one part of the country or another. Irrigation is, therefore, an inseparable part of the welfare of Indian agriculture.

The country's population, which is now about 950 million, is expected to reach the billion mark by the turn of the century. The production of food grains, which was around 50 million tons in the pre-plan period, has reached about 195 million tons now and will have to be raised to 220 million tons by the year 2000. Boosting irrigated agriculture is the only way to achieve this target.

The management of irrigation in India differs conceptually from that practised in those developed countries where limited water is not a constraint. Good management, efficient operation and well-executed maintenance of irrigation systems are essential to the success and sustainability of irrigated agriculture. They result in better performance, better crop yields and sustained production. One of the key objectives in the management of an irrigation system is to provide levels of service as agreed with the relevant government authorities and the consumers at the minimum achievable cost.

In many parts of the world, irrigation systems are performing well below their potential. The problem of poor irrigation performance has stimulated the interest of a whole range of development professionals. There is unanimous agreement among them for the need to improve the operation of irrigation systems in order to increase productivity. In most countries great importance is now placed on programmes for rehabilitation, operation and maintenance of existing projects. However, works included in these programmes are often limited to canal lining, land levelling, construction of additional control structures, rehabilitation of existing control structures, improvement of access roads and to non-physical components such as staff training, improvement of cost recovery systems and so on. Too often, not enough attention is paid to alternative approaches to irrigation management, system operation and design.

History of irrigation in India

The history of irrigation in India can be traced back to prehistoric times, when agriculture was first practised by mankind. The Vedas and other ancient Indian texts make frequent references to wells, tanks, canals and dams and to the responsibility of the community for their efficient operation and maintenance. The entire landscape in southern and central India is studded with tanks and wells, some of which were built many centuries before the beginning of the Christian era. In North India there are equally old small canals in the upper valleys of rivers. The character of these works was largely conditioned by the natural features of the area. In the arid and semiarid plains of the perennial rivers of the north like the Ganges and the Indus, flood flows were diverted through inundation canals for irrigation, while in the rain-challenged south, water had to be stored in large tanks for domestic and agricultural use. Since the majority of the rural population subsisted on agriculture, irrigation had to be developed for growing crops in view of the vagaries of rainfall. While the use of groundwater from shallow wells was largely the result of individual private efforts, the surface water development for irrigation has traditionally been the result of community or state efforts.

Irrigation development in India gained momentum after Independence. The net irrigated area in 1950-51 was 20.85 million ha, with 1.71 million ha irrigated during more than one crop season. The gross irrigated area was 22.6 million ha. The planners assigned a very high priority to irrigation in the five-year plans. As a result, giant multipurpose and irrigation projects such as the Bhakra Nangal in Punjab, Damodar Valley in Bihar and Hirakund in Orissa were taken up.

By the end of the seventh five-year plan, the country had an irrigation potential of 29.9 million ha under large and medium-sized irrigation projects and 46.6 million hectares under smaller projects. By 1993-94, the irrigation potential created under the bigger irrigation projects was 31.2 million ha, 27.1 million ha of which were in use. In the case of the smaller irrigation projects, the potential created was 51.7 million ha, with 47.7 million ha used.

The target now is to achieve by the year 2010 the ultimate irrigation potential of 113.5 million ha from all sources of water - 58.5 million under large and medium-sized projects and 55 million under smaller projects. This means adding some 1.7 million ha a year to the larger irrigation projects.

With the rapid expansion of the irrigation programme since the beginning of the planned economy in the early 1950s, there was significant growth in irrigation potential. It was soon realized that the potential created was not being fully used as farmers failed to distribute the water equitably and efficiently and to synchronize field activities with the creation of irrigation potential at the outlet. Thus a gap developed between potential and use, as can be seen from the table below.


Cumulative potential
(million ha)

Cumulative use
(million ha)

Gap in use of potential (million ha )





















Efforts to minimize the gap were initiated early in the Fifth Plan, i.e. in 1974-75, by initiating a command area development programme, with the following features:

Canal system operation in India

The canal system transfers water from its source(s) to one or more points of diversion downstream. Operation deals with the movement and behaviour of water in a canal system, and relies on the principle of open channel hydraulics. The primary function of operation is to manage the changes in flow and depth throughout the canal system. The term `operation' refers to the hydraulic reaction in the canal pools which results from control actions. Several methods are available which can be used to convey water downstream through a series of canal pools. The method of operation determines how the water level varies in canal pools to satisfy the operational concept. A canal's recovery characteristics - the speed and manner in which the canal recovers to a steady state flow after a flow change - depend on the method of pool operation.

Conventional operation

The majority of canal systems in India are operated in a manner which is referred to as conventional operation. A conventional operation consists of a scheduled delivery, an upstream operational concept and a constant downstream depth operational method.

Conventional operation evolved as a practical method of satisfying irrigation needs within traditional canal system limitations. By using delivery schedules, it essentially combines demand-based needs with supply-based operation. The purpose of conventionally operated canals is demand-oriented, since the primary goal is to satisfy the needs of the water users. The downstream demand for water is assessed in advance so as to schedule the supply of water entering the canal through the headwork. Although the headwork flow is based on this schedule of anticipated demand, the actual operation of the canal is based on the supply. Check structures are operated to respond to upstream conditions, and the outflow from a pool reacts to the inflow.

One weakness of conventional operation is the inevitable discrepancy between forecast and actual delivery flows. In addition, there will be always inaccuracies in checking the flow and the amount of water stored in the canal pools. Since the canal system is not operated to react to actual demand, any such errors are transferred downstream. The sum of all operational errors will accumulate at the far end of the canal. Tail-end water users will often suffer from too much or too little water. To prevent shortages of water at the downstream end, excess water must be supplied at the headwork. Most of the time, this excess ends up being wasted near the downstream end of the system. The typical wastage in a conventionally operated canal system is about 5 to 10 percent of the total flow.

Conventional operation involves the following basic procedure :

  1. orders are submitted by the water users;
  2. a water schedule is formulated;
  3. flow changes are made at the head of the canal to meet the water schedule; and
  4. the canal is operated manually to transfer these changes downstream, making adjustments at the canal-side turnouts and canal check structures en route.

Water delivery practices in India

Depending on the type of schemes the water distribution system for irrigation can be different for surface irrigation and groundwater projects. The important models of distribution of water below outlets in surface irrigation commands developed over time in India on the basis of requirements and experience are:

  1. the warabandi or osrabandi system of Punjab, Haryana, Rajasthan and Uttar Pradesh;
  2. the shejpali and block systems of Maharashtra and Gujarat and satta system of Bihar; and
  3. the localised system for paddy areas in the southern states of Andhra Pradesh, Karnataka, Tamil Nadu, etc.

Warabandi or osrabandi

The word warabandi originated from two vernacular words, wara and bandi, meaning `turn' and `fixation' respectively. As such, warabandi literally means `fixation of turn' for supply of water to the farmers. Osrabandi is a synonym of warabandi. Under this system of management, the available water, whatever its volume, is equitably allocated to all farmers in the command irrespective of location of their holdings. The share of water is proportional to the holding area in the outlet command and allocated in terms of time interval as a fraction of the total hours of the week. Whereas the term warabandi is commonly used in Haryana, Punjab and Rajasthan, this system of water distribution is usually referred to as osrabandi in Uttar Pradesh.

Shejpali, block and satta systems

The main feature of these systems is that the government enters into some sort of agreement with the farmers for supplying water to them. The farmers file applications and the government issues permits for the supply of water and the two together constitute the agreement. The shejpali and the block systems are practised in Maharashtra, Gujarat and parts of Karnataka, whereas the satta system was evolved and is still in use in the Sone command area in Bihar, which is one of the oldest irrigation systems of the country. The word satta means agreement. The satta system includes the features of both the shejpali and the block systems.

Under the shejpali system the water is distributed according to a predetermined date in each rotation. A preliminary programme is drawn up every year depending on the availability of water. Farmers submit applications for supply of water indicating the crops they wish to grow and the areas under them. Water is then apportioned on the basis of the crops and the overall demand. Proportionate reductions in the irrigated area proposed by the farmers are made if the demand is found to be higher than the water available. A schedule, known as shejpali, fixing the turns to different farmers for the sanctioned crop area is prepared for each rotation. The farmers at the tail-end of the command are served first, those at the head of the watercourse are served last. The irrigation interval depends on the rate of water consumption by the crops, i.e. high water consuming crops may be supplied water in each rotation, whereas the lighter crops on the same outlet may get irrigation on alternate rotations. The schedule so made is notified in advance and every farmer of the command has prior information about his turn of supply. The system is called `rigid shejpali' if the duration of supplying water to the various fields along with the date is also recorded on the permits issued to the farmers for sanctioned areas. This checks the tendency of the farmers to overdraw water.

Under the block system, a long-term arrangement for supply of water is done particularly on perennial crops, but irrigation from season to season proceeds through shejpali. One third of each block is to have sugarcane and the remaining two thirds is to be used for seasonal crops. The blocks are sanctioned for six to twelve years. There is assured supply of water for a long period under this system and farmers therefore can go for land development and plan their cultivation well.

The localised system for paddy areas

In most of the irrigation projects of southern and north-eastern states as well as in the states of West Bengal, Orissa, Bihar and Jammu & Kashmir, where paddy is the main crop, the irrigation below the outlets proceeds from one field to the other through surface flooding. The individual holdings are thus irrigated one after the other or even more than one field is irrigated at a time. Such a method of water distribution is prevalent in many of the outlet commands (where warabandi has not been introduced) in the Chambel Irrigation Project of Rajasthan. However, in Tamil Nadu and some other states, the farmers have a rotational system of water distribution in the outlet commands of some irrigation projects on one and a half days to four days basis for paddy crop and a longer interval for other crops. In this case, the water allocation is for a specified crop in a season and penalty is levied for deviation.

The modernization needs of irrigation system operational management in India

Although in India the major consumer of water is irrigated agriculture, the demands for various other competing and conflicting purposes are ever increasing. Ensuring water supplies in sufficient quantity and desired quality, properly distributed in time and space, has become a complex task. Water resource planning and management has become multidisciplinary in nature, requiring co-ordination among various government and non-government agencies. Making optimum use of water resources has long engaged human effort but it is only in recent times that it has taken the form of integrated water resources development and management. Pressure on the available water resources for conflicting uses has become so great that individual water resources projects, whether single purpose or multipurpose, cannot be undertaken or managed with optimum benefit unless there is a broad plan for the entire drainage area. Integrated development and management thus involves a co-ordinated and harmonious development of the various works (existing and new) in relation to all reasonable possibilities. This may include irrigation and drainage, generation of electrical energy, navigation, flood control, watershed management, industrial and domestic use of water, recreation and conservation of wildlife.

Water resources development planning has traditionally been attempted at state level, as in the case of other sectors, although it is well known that water does not obey political or administrative boundaries. Yet a river basin or a sub-basin should be the basic hydrological unit for water resource planning. In the early stages of water resource development, projects were formulated to serve mainly irrigation requirements or irrigation combined with hydropower generation and some other incidental purposes. As projects were relatively few, inter-project considerations were more or less absent and each project was considered and planned as an independent entity.

In spite of substantial growth in irrigated agriculture and consequent agricultural productivity over the years, irrigation systems in India are still facing many problems. The root cause of the poor performance of our irrigation systems may be the lack of scientific approach to their management. On most command areas served by a canal, water is poorly distributed over area and time. A common shortcoming is that tail-end users are not getting water or are getting insufficient and unreliable water. Conversely, head-end users often get too much water, either because they have no choice or deliberately, taking water when they can and often more than needed. Low irrigation efficiency is also attributed to changes in cropping patterns. In many cases, the cropping pattern actually adopted by the farmers is very different from the designed cropping pattern because it is mostly influenced by market forces, farmers' preferences, reliability of water supply and other factors. The on-farm irrigation practice prevailing in the country also results in wastage leading to low irrigation efficiency. Most farmers still irrigate the way their forefathers did thousands of years ago by flooding or channelling water through parallel furrows. This gravity system, typically least expensive to install, fails to distribute water evenly. Farmers are forced to apply an excessive amount of water to ensure that enough reaches the plants situated on higher ground or on the far side of a field. The adoption of field-to-field irrigation adds to the problem, as does poorly conceived irrigation scheduling.

Modernization of irrigation system operational management by way of canal automation

The overall water use efficiency of a manually operated system, exclusive of the use of any return flow, seldom exceeds 40 percent. It is reasonable to expect an increase of the overall efficiency of about 10 percent or more for a system with some automation. The advantages of automation are not limited to savings in operation cost and in water. It also alleviates the risk of waterlogging and salinization. A further advantage is that it increases the reliability and accuracy of water distribution. This contributes to the establishment of a climate of confidence between the operating authority and the farmers, which in turn contributes to the effective organization of water user groups and their participation in operation and maintenance activities. With automation, it may also be possible to accurately know the volume of water delivered to individuals or groups of farmers. This makes possible the introduction of volumetric water charges, combined or not with a system of annual volumetric allocation. This approach is a useful tool for encouraging farmers to optimize the use of limited water allocations and to increase productivity.

Improvements in automatic control equipment have greatly expanded the field of canal operation and control. Automation has become a common term when discussing modern canal systems. `Automation' is defined as A procedure or control method used to operate a water system by mechanical or electronic equipment that takes the place of human observation, effort and decision; the condition of being automatically controlled or operated.

Automating a canal system is therefore implementing a control system that includes automatic monitoring or the control equipment that upgrades the conventional method of canal system operation. Automation is used to simplify and reduce or replace the decision-making process of the operators and to implement a decision. It is increasingly used to improve the effectiveness and to reduce the cost of water supply system operations.

Automation of distribution canals becomes essential for optimum conditions. The process must not be dismissed out of hand as too expensive. Its economics must be studied, keeping in mind that reduced on-farm costs and water requirements, and increased yields and management capabilities, provide savings that usually will more than make up for increased project costs. Reduction of project operation costs and water loss is also a benefit of automation and is usually the only one considered.

Automation of a canal system should not be thought of as an end in itself, but rather as a means to better operate that system. The true goal should be to achieve the most efficient and beneficial operation possible. Expanding control system capabilities is one way of economically reaching this goal.

Automation can be obtained in many ways, some extremely simple, others very complex. A long crested weir (also called duckbill or folded weir) by its very existence maintains a nearly constant water level in a canal under variable flows. A closed pipe line system connected to a variable source such as a canal carrying excess water to local needs, will automatically convey the exact amount of water that is withdrawn at the turnout valves.

Float-actuated mechanical devices such as the Neyrtec constant level and the improved controlled leak canal gates are self-contained but can obtain a constant canal water level. These systems easily adjust to variable flow rates. If they are desired to control down to the no-flow regime rather than just regulate the flow, they need to be installed in top-level canals. They are sluggish in reaction as they receive input in sequence from each adjacent reach to transmit a change over the whole canal length.

The objective of building and operating a canal system is to serve the farmlands, supply municipal and industrial needs, carry storm runoff to natural drainage channels, collect water from several independent sources into a single supply, convey water used for the generation of electrical power and supply water to fish and wildlife and for recreation. In order to serve the above purposes as efficiently and economically as practicable, canal operations should be tailored to meet the specific requirements of the systems.

The flexible, high-quality operation of a canal system will yield many benefits, some of which are:

Most of these benefits result in obvious economic savings and some of them represent intangible benefits to which it is difficult to assign a monetary value. Regardless, they all result in a better and more cost-effective water resource project.

Present status of canal automation in India

To improve irrigation efficiency in general and to assure a reliable supply of water to users in particular, many water resource projects in India, whether existing or new, have taken up the challenge to improve water management by way of remote monitoring and controlling of various physical structures and parameters. In most of the projects, it has been planned to select a segment of the existing canal system for a pilot project which will study and analyse the benefits of improved water management systems and which can cover a larger area later on.

To describe the present status of canal automation in India, we will discuss the case studies of canal automation on the following water resources projects:

  1. the Chambal project in Madhya Pradesh,
  2. the Khadakwasla project in Maharashtra,
  3. the Majalgaon project in Maharashtra,
  4. the RAJAD project in Rajasthan,
  5. the Sardar Sarovar project in Gujarat and
  6. the Tungabhadra project in Karnataka.

The Chambal project in Madhya Pradesh

The Chambal project is a multipurpose project, a joint venture of the states of Madhya Pradesh and Rajasthan. It is comprised of a cascade of reservoirs, i.e. the Gandhisagar reservoir in Madhya Pradesh, the Ranapratapsagar reservoir in Rajasthan and the Jawaharsagar reservoir in Rajasthan, (with a powerhouse at the foot of each of the reservoirs), and of a terminal barrage at Kota in Rajasthan, which has two main canals for irrigation purpose. Total installed capacity of hydropower generation at the three dams is 386 MW. The state of Madhya Pradesh is served by the Right Main Canal (RMC), which cuts across Rajasthan for about 130 km, then crosses over the Parvati river and enters Madhya Pradesh with a design discharge of 110.4 cubic meters per second (cumecs) at the Parvati aqueduct. The entire Chambal command area has been divided into seven administrative divisions, namely Sheopur, Sabalgarh, Joura, Morena, Ambah, Gohad and Bhind.

The Chambal project was commissioned in 1961-62 with a projected irrigated area of 283 500 ha annually (85 050 ha for kharif and 198 450 ha for rabi crops). The maximum irrigation achieved so far was 188 307 hectares in 1977-78, and the minimum 124 016 ha in 1982-83. The average area under irrigation over the last fifteen years is of 148 000 ha. Large areas at the tail-ends of the Ambah Branch, Morena Branch, Bhind Main canal and Mau Branch canal have not received the benefit of canal irrigation since the commissioning of the project.

In the present system of operation of the Chambal canal network, the availability of water at the beginning of the rabi season, i.e. on 15 September, is assessed. In the Chambal command area, water is allocated from crop season to crop season, through an announcement called `Sinchai Ghosna', which is issued before or on the eve of the crop season and contains figures of areas to be provided with water at the subdivision, block, tehsil, assembly and branch-distributary levels. The names of the villages to be irrigated, and in each village of the channel and the reduced distance from the heads up to which water will be provided, are also indicated. During the first fortnight, the Right Main canal with all distributaries under its direct command, the Lower Main canal, the Morena Branch, the Bhind Main and the Mau Branch canals are supplied with water. During the second fortnight, while they continue to get water, the Ambah Branch canal in turn is supplied but all the direct command distributaries on the Right Main canal are closed. During the third fortnight, the Right Main and Ambah Branch canals with all their direct distributaries are supplied with water. The minors, sub-minors and fields get their water by adjustments. Although the announcement is made at the start of the rabi season, it has not been possible, so far, to really supply the allocated water and the tail-end users have always suffered. An analysis of pattern of deliveries at the Parvati aqueduct indicates that the supplies have wide fluctuations daily, monthly and yearly, and also vary according to the crops. Due to the unreliability of flows, many farmers are left guessing as to the quantity and timing of the supplies they will receive.

A part of the Chambal canal system in Madhya Pradesh has been selected for a UNDP-funded pilot project, in the Sabalgarh administrative division, and in association with the local Central Water & Power Research Station.

The Khadakwasla project in Maharashtra

The Khadakwasla irrigation project consists of three dams, viz. the Tanaji Sagar dam (Panshet dam) on the Ambi river, the Veer Pasalkar (Warasgaon) dam on the Mose river and the Khadakwasla dam on the Mutha river. The Khadakwasla dam is located downstream of the confluence of the Ambi and Mutha rivers, some 17 km west of Pune city, near the village of Khadakwasla. The New Mutha Right Bank canal is a contour canal, with a design discharge capacity of 58 cumecs. It is planned to irrigate 97 100 ha of gross command area, with 62 146 ha of irrigated area over the district of Pune. The command is covered by 60 distributaries off-taking either directly from the canal or from the Bhigvan branch (located about midway along the canal) and the Indapur branch in which the New Mutha Right Bank canal tails.

The New Murtha Right Bank is a long canal, and the effect of a change made in the release of water at its head will take time to be felt at the distributary heads downstream. A rough estimate is that it will take about 24 hours for a change made at the head to get transmitted down to the tail. When a canal has to be run with requirements down the line changing from day to day, operation becomes complicated for the following reasons:

  1. Changes have to be made in the releases at the head of the canal in anticipation of the change of demand (closing of running distributaries and opening of new ones) and associated travel time to the various distributary off-takes.
  2. When level changes occur down the main canal as a consequence of a change in release at its head, the discharge into the distributaries will change. Therefore, unless close watch is kept on distributary off-takes and gate settings are adjusted, deliveries into distributaries will not match what is planned. The operating staff will tend to play safe and ensure that their distributaries are drawing more than what is strictly required.
  3. Gate settings at cross regulators will need to be adjusted to reduce fluctuation in water levels in the different sections of the canal. The frequency of adjustment will depend on how releases into the canal change to satisfy the changed demands at distributary off-takes.

The decision on the release of water into the New Mutha Right Bank canal from the reservoir is taken at the main administrative headquarters, i.e. in Pune, which must decide whether it is appropriate to release the entire amount of water determined based on the requirements arrived at from the operational schedule received from the field, or to cut down on the requirements. The decision will be made in the light of the current storage available in the reservoir and of an assessment of the likely demand and inflows in the reservoir for the rest of the season, and of the storage that is desirable at the beginning of the next season.

The water delivery system as practised in the state of Maharashtra is known as the shejpali system. In this system, at the beginning of the season the farmers make applications in prescribed forms for the irrigation of specific areas. The Department of Irrigation accedes to the requests depending on the availability of water and other relevant factors. In the shejpali irrigation delivery system, the distributary is considered as a unit, i.e. with all minors and sub-minors if any is running for the same number of days as the distributary. The irrigation schedules are prepared taking into account more or less uniform characteristics of the command, as it is very difficult in practice to calculate the demand based on the condition of the various fields in the command. In the shejpali system, the Department of Irrigation commits itself to providing adequate water at the outlet to meet the irrigation requirement of a crop till maturity. What is adequate for the standing crop in the field is decided by the farmer and the effectiveness of irrigation is judged by the degree to which the irrigation department is able to fulfil its commitment to the farmer. For the success of this system, it is necessary to have reliable irrigation supplies at least at the head of the distributaries.

The pilot project is conceived as one unit, integrating telemetry, communication, computers and decision support software to improve system operations. It covers the operation of the New Mutha Right Bank canal and its distributaries. Three agencies, i.e. the Department of Electronics of the central government, the Department of Irrigation of the government of Maharashtra and CMC Ltd. are associated in the project.

The Majalgaon project in Maharashtra

The Majalgaon irrigation project is located in the Marathawada region of Maharashtra, south-east of Aurangabad, in the valley of the Godavari river. It constitutes the downstream part of the Jayakwadi project, which is planned to irrigate about 350 000 ha of cultivable command area. In this region, the Paithan dam on the Godavari has a gross storage capacity of 2 950 Mcm, supplying water to the Paithan left bank and right bank canals, and the Majalgaon dam on the Sindhphana river, with a gross storage capacity of 450 Mcm, is supplying water to the Majalgaon right bank canal. The runoff of the Sindhphana basin is insufficient to meet the water requirements of the Majalgaon project, and shortages are to be supplemented by additional releases from the Paithan dam.

Compared to other Indian states, Maharashtra is poorly endowed in water resources. Even with full exploitation of the available water resources, the total area that could be brought under irrigation, including well irrigation, would be about 34 percent of the total cultivable area. The water delivery schedule popularly known as the shejpali system has been in practice in the state for over fifty years. In its present form, any change made at the head of a canal to suit the changing demands down below takes a long time to be felt at the distributary. If there are frequent changes in the demands on the distributary, the releases at the head reach must be changed accordingly, and unless a very close watch is kept on the distributary off-takes and there are frequent gate settings adjustments, the deliveries in the distributaries will not match what is anticipated.

To overcome the problem, the government of Maharashtra has implemented a system of volumetric water distribution to the farmers' association on the Majalgaon project. This requires that the volumes, flows and levels in the main and branch canals be controlled to suit the operational philosophy. Improved water control with the help of constant water level gates, baffle distributors and remote monitoring and real-time computer-assisted management control has been executed on the Majalgaon project.

The government of Maharashtra has introduced a pilot project to improve water control management on the Majalgaon Right Bank canal from Km0 to Km165 in two successive phases. The first phase has covered the entire 100km length of the canal and the entire length of its Ganga Masla branch. Technically it consists of a combination of control and regulation techniques associated with remotely monitored computer-assisted control on the main canal and local control using float gates, long crested weirs, baffle distributors and self-regulated outlets on GMBC distributaries and minors.

The Majalgaon Right Bank canal has a design discharge capacity of 83 cumecs at its main head regulator. Ten cross regulators are planned over its 100 km. The Ganga Mala branches off at about 8 km on the Majalgaon Right Bank canal and has a designed discharge capacity of 9 cumecs. Upstream control with avio gates and baffle distributors at the head gate of the Ganga Mala branch, along which nine duckbill weirs have been installed over a 13km stretch for improved water control. The length of weir is about 50 m for a discharge of 9 cumecs.

The constant volume concept of operation will be used on the Majalgaon Right Bank canal. When it will be extended beyond Km100 and the demand of irrigation water at main-head regulators will increase beyond 60 cumecs (as against a designed discharge of 83 cumecs), the canal will be operated on the concept of controlled volume.

At each remote location, remote terminal units will be installed. Sensors will measure water level upstream and downstream of the gate and at the centre of the pool. The gate position sensor will sense the position of each gate in the control structure. Data will be transmitted by radio. The main control centre will be located at the Majalgaon dam site and will have the usual hardware and software necessary for remote monitoring and control functions.

Water will be supplied by volumetric allocation with a rotational water delivery system. User associations, covering an area of about 200-300 ha, will receive water from the canal system and will distribute it to their members on a rotation basis.

The second phase will be implemented on the remaining part of the Majalgaon Right Bank canal and its distribution system, based on experience gained in the first phase. The pilot project is carried out under an Indo-French co-operation programme in water resource management. The government of Maharashtra, in consultation with the French consulting firm Gersar, has implemented the first phase of the project at a cost of Rs136.7 million.

The Rajasthan agricultural drainage (Rajad) project

The Chambal command area, in the south-eastern part of Rajasthan, serves an irrigated area of 229 000 ha from storage facilities on the Chambal river and a diversion dam at Kota. The Left Main canal serves about 102 000 ha of irrigated land and the Right Main canal 127 000 ha of irrigated land. In addition, the Right Main canal carries water to irrigate an area in the adjacent state of Madhya Pradesh. The latter, which thus shares the water of the Chambal river with Rajasthan, has installed a wireless radio network along the Right Main canal to monitor its share of the water. This has proven to be a valuable tool in tracking flows along the initial 130 km of the Right Main canal, which are in Rajasthan.

The Command Area Development (CAD) authorities of the Chambal and Indira Gandhi Naher projects aim to have an improved sub-surface drainage and water management in the command area. An important part of water management is the automation and remote monitoring system on the canal. The Chambal CAD authorities recognize the value of canal automation and have initiated steps to install a voice communication radio network that would put all parts of the command area within 20 km of a base station. The voice communication network will consist of ten field base stations located at CAD offices throughout the command area. In addition there will be 11 mobile units for senior staff to allow them to keep in contact with all stations when they are away from their offices. A data communication network is also planned on the canal system to collect data related to water levels and flow rates.

In a pilot project, four remote monitoring sites have been selected. From these, data will be transmitted to the CAD office for monitoring and control. A head regulator gate on one of the distributaries which was of the slide type and manually operated has been replaced by an automatic gate. To maintain constant water level in the distributaries, duckbill weirs are planned to be installed at the location of an existing fall-cum-village road bridge structure. The pilot project comes under an Indo-Canadian co-operative aid project and is being implemented by the CAD authorities of the Chambal and Indira Gandhi Naher projects in consultation with Canadian experts.

The Sardar Sarovar project in Gujarat

The Sardar Sarovar (Narmada) project, currently under construction, is one of the largest multipurpose water resource development projects in India. It will consist of a large concrete gravity dam on the Narmada river in the state of Gujarat, a riverbed powerhouse (underground, with an installed capacity of 1200 MW), a canal-head powerhouse (surface, with an installed capacity of 250 MW) and a widespread network of canals and drainage channels as required to irrigate about 1.792 million ha of land out of the 3.428 million ha of the gross command area. The command area of the project spreads over 12 districts and 62 tehsils (partially or fully) of the Gujarat state. The canal water released from the Sardar Sarovar reservoir will pass through the 250MW canal-head powerhouse located below the Vadgam saddle dam on the right rim of the reservoir near the Sardar Sarovar dam. The water will then flow through four secondary ponds created by a series of rock-filled dams, which are interconnected by open channels. These ponds provide diurnal balancing storage of the flows released through the canal-head powerhouse to provide hydroelectric peak capacity. The 458km-long concrete-lined Narmada Main canal will be one of the world's largest multipurpose water supply canals. It extends on the northern side from the dam site up to the Gujarat-Rajasthan state border. The Narmada Main canal will have a design discharge capacity of 1 134 cumecs at its head and it will taper down to 71 cumecs at the border. The canal is extended further to irrigate parts of the Barmer and Jhalore districts of Rajasthan and also to provide domestic, municipal and irrigation water supply. Its head regulator will control water deliveries through five 12.2 x 13.5 m radial gates. The cross section of NMC at its head has a 73.1 m bottom width and a water depth of 7.6 m with a 2:1 inner slope on either side. The flow velocity at the head of the canal with a designed discharge of 1 134 cumecs will be 1.69 metres per second.

The Narmada Main canal will supply water to a vast conveyance and delivery network comprised of branch canals, distributaries, minors and sub-minors of a total length of more than 47 000 km. The canal system has been designed to operate on the `controlled volume' concept for timely deliveries. A real-time computer-based monitoring system and a state-of-the-art communication network will allow remote control operation of the canal conveyance system to provide reliable and equitable distribution of water. In a 75-percent dependable year, under full development, there will be approximately 9 million acre feet (Maf) of water delivered through this system in Gujarat from the reservoir formed by the Sardar Sarovar dam.

From the Narmada Main, two major branch canals branch off, at Km264 and Km386, to convey water for irrigation, domestic and municipal needs and for industrial uses. The Saurashtra Branch, which branches off at Km264, is 104km-long and has a difference of 40 m over that length. This means that water needs to be lifted by about 70 m to cover the command area and the entire Saurashtra region for the supply of drinking water. At three fall sites, hydropower will be generated and used to lift water at five pumping sites. Similarly, on the Kutchchh Branch canal, which branches off at Km386, there will be a series of falls and pumping plants to serve the command area in Kutchchh and to cover the entire Kutchchh region for the supply of drinking water.

In a 75-percent dependable year and under full development, the Gujarat state will have approximately 9 Maf of water to use from the Sardar Sarovar reservoir. Priority is to be given to the supply of drinking water and of municipal water followed by industrial water and irrigation. Thus, about 1.06 Maf of water will be used for the drinking and municipal water supply and for industrial use; 8 215 villages and 135 urban centres will receive water for drinking purposes. About 7.94 Maf of water will be available for irrigation to cover a widespread command area. It is planned to irrigate about 1.79 million ha of land, which means that water availability per unit area, at the head of the main canal head regulator, will be about 55 m3.

The command area covered by the Kutchchh branch canal lies at a distance of about 800 km from the Sardar Sarovar reservoir. The effect of change made in the release of water at the head of the Narmada Main canal will take time to be felt downstream. A rough estimate is that it will take about 7 days for a change made at the head to get transmitted down to a tail located 800 km away. The operation of the canal system becomes complicated if operated in a conventional way, for the following reasons:

  1. The canal water released from the Sardar Sarovar reservoir will pass through the 250 MW canal-head powerhouse located below the Vadgam saddle dam on the right rim of the reservoir. As this powerhouse is provided for hydroelectric peak requirements, it will be operated for about 8 to 10 hours a day. To provide diurnal balancing storage of flows released through the powerhouse and water drawn into the canal system, a balancing reservoir is created upstream of the main canal head regulator. A diurnal variation of about 3 m will be there in this reservoir, thus to control the discharge into the main canal, the gates of the main canal head regulator will have to be operated more frequently to take care of changes in water levels in the balancing reservoir.
  2. Changes have to be made in the release not only at the head of the Narmada Main but also at the head of the other main canals branching off it, in anticipation of changes in demand. This requires a very close monitoring at all locations of the control structures.
  3. When level changes occur down the Narmada Main canal as a consequence of a change in release at its head, the discharge into the branch canals and hence the distribution system will change. Therefore, unless close watch is kept on branch canal off-takes and gate settings are adjusted, deliveries into the branch canals will not match what is planned.
  4. Settings at cross regulators will need to reduce fluctuation in water levels in sections of the Narmada Main and its branch canals. The frequency of adjustments will depend on how releases into the main canal satisfy the changed demand downstream.
  5. Pumping stations on the Saurashtra and Kutchchh branch canals can create emergency conditions when they fail to draw their designed discharge due to either power failure or some mechanical fault at the pumping plants. The design discharge of the Saurashtra Branch canal is 319 cumecs. When such a heavy discharge is rejected, the water already released from the reservoir must be handled so that it is not wasted and the main canal and respective branch canals are not overtopped. Simultaneous gate operations of various control structures become essential in such a situation.

To overcome the above problems, the conveyance and delivery system is planned to be operated with a design discharge capacity of up to and above 8.5 cumecs under the `controlled volume' concept. The operational plan is designed to provide efficient, reliable and equitable water supplies to the users. The primary objectives are to:

Canal operation in general centres on the pivot point of the canal pool's water surface. The pivot point is the location within a canal pool at which the depth remains constant while the water surface slope varies. The Narmada canal system is planned to be operated on a controlled-volume basis by managing the volume of water contained in each canal pool. There is no well-defined pivot point. The volume can be made to change to satisfy operational criteria, allowing the pivot point to move within the pool. The water surface may sometimes rise or fall without a pivot point, like a reservoir. Since the operation is based on volume, either flow or depth may be used as the measured quantity. The Narmada canal system is also planned to work on the upstream operational concept. The upstream operational concept is used when the upstream conditions or supply dictate how the system is to be operated. As the availability of water for irrigation is limited to the availability of water in the Sardar Sarovar reservoir, the upstream operational concept is used.

The operation of a canal system is accomplished primarily by controlling the flow through the check structure. Flow charges which are initiated by gate movements create the translatory wave phenomenon. The Narmada canal system is planned to be operated by the simultaneous control structure operating technique. Adjusting all the canal check structures simultaneously can establish the new steady state flow condition in the canal system in the shortest possible time.

The Narmada canal system is planned to be operated using the supervisory automatic control method. The supervisory control method involves monitoring and control of the control structures from a central location referred to as the main control centre. Monitoring is the collection of data from various sites on the canal system and the presentation of this information for use in determining control actions. Data such as water level, gate positions, flow and pump status are collected at each remote location, including check gate structures and pumping plants. The information collected at all remote locations is transmitted to the control centre, where it is analysed and presented in a suitable format. Control commands are then transmitted back to the remote sites, creating control actions such as gate movements. Supervisory control enables control decisions to be based on comprehensive information. A change in any portion of the system can be recognized promptly and the appropriate control action taken. This capability maximizes the operational flexibility of a canal system.

The system is also planned to be operated on the upstream control concept. The control concept in general is defined by the location of the information needed for control relative to the control structure. This information can include the flow, depth or volume at one or more points in the canal system. In the case of the upstream control concept, the control structure adjustments are based on information from upstream. The required information could be measured by a sensor located upstream or based upon the upstream water schedule established by the irrigation management authorities. Upstream control transfers the upstream water supply (or inflow) downstream to points of diversion or to the end of the canal and is compatible with the upstream operational concept.

The Narmada canal system is thus planned to be operated on the controlled volume method with an upstream operational concept. The control action is initiated with an upstream control concept and with the supervisory automatic control method. The simultaneous control structure operating technique will enhance the canal operation. Based on these, for the purpose of irrigation management it is proposed to divide the 3.428 million ha of gross command area into blocks of approximately 26 000 ha. The irrigation management data for each of the blocks will be collected by a data collection centre, using very high frequency radio. One hundred thirty-two such centres are planned. They will communicate data required for the regulation of branch canals to divisional operational centres, which will be in charge of branch canals. Taking into account the limitations imposed from a hydraulic and canal operation point of view, 15 divisional operational centres are planned. They, in turn, will report to the main control centre, which will be in charge of the overall operation of the Narmada canal and will be located near Gandhinagar.

The Narmada canal conveyance and delivery system of up to 8.5 cumecs designed discharge capacity has been planned and designed to be operated on the controlled volume operational method with remote monitoring and control system for its operation. The construction of the canal conveyance and delivery system in Phases I and II of the project area is in full swing. The work in Phase I is about to be completed. One divisional operational centre in Phase I of the command area will be selected to carry out the pilot project. It will cover about 100 km in length over the canal system with some 120 flow control gates and about 0.15 million ha of irrigated area. The Sardar Sarovar Narmada Nigam Co Ltd, in consultation with experienced consultants, will take up the task of implementing the pilot project in the near future.

The Tungabhadra project in Karnataka

The Tungabhadra project was conceived and executed to serve the chronically drought-prone districts of Raichur and Bellary of Karnataka, and the Anantpur and Kurnool districts of Andhra Pradesh. To manage this project the Tungabhadra Board was constituted by the Government of India in 1955. From the 2 300 Mm3 of water expected to be developed by the project on average over the long term, Karnataka receives 1 515 Mm3 and Andhra Pradesh 785 Mm3.

The Tungabhadra project involves three main canal systems, viz. on the right side (both a low-level unlined and a high-level lined canal systems) and on left side (lined canal system), running for a total length of 750 km and covering an irrigated area of more than 0.5 million ha.

The present canal operational procedure is based on the following principles:

  1. Canal capacities are designed for average duties. If a canal serves areas of mixed crops, its capacity is sufficient to provide authorized discharge for the seasons with the maximum requirement. In other seasons it is operated at a reduced discharge.
  2. Continuous flow is provided to the outlets so that, in principle, canals run continuously to provide a specified discharge to the controlled outlets. If a full supply is not required, then its discharge can be reduced.
  3. Variable supply and flexibility are important operational objectives since variable discharge may be required at any level, either to serve different localised areas in different seasons or to meet different crop requirements within a season.

The flexibility provided in the present distribution system requires that gates at every control structure be adjusted to respond to variable flows in the parent canal. For the system to work, it is necessary that the gate operators perform their duties correctly and on time, and that there be no interference in the gate setting or in the flow regime of the parent canal.

The pilot project has been executed in the state of Karnataka on the right bank high-level canal up to the Karnataka-Andhra Pradesh state border. In this task, four agencies are associated. The Central Water Commission of the government of India, the Tungabhadra Board, and Bharat Electronics Co Ltd, in consultation with USAID experts, have executed the pilot project.

From the above case studies it can be noted that the Central Water Commission and the Department of Electronics of the central government, various state governments and public- and private-sector companies have entered programmes to improve water management on existing water resource projects by involving engineers and scientists from various disciplines, all of them with the goal to satisfy the desire of end-users for reliable and timely delivery of irrigation water. With the improvement in water management now being planned, it will be possible to improve the irrigation efficiency at farm level and operational ease and flexibility at project level.

Cost aspect of canal automation in India, based on case studies

The financial and economic analysis of plans to automate irrigation canal systems implies complex technical exercises that require the expertise of professional economists and financial analysts as well as engineers, agronomists, land classifiers, soil scientists and other irrigation specialists. The financing of such plans, in most cases, requires programmes and financial resources beyond the capability of water users. Financial and economic considerations are therefore the key to the successful implementation of plans to automate irrigation canal systems.

While financial and economic analyses are closely related, a distinction between the two is necessary. Economic analysis is used to estimate total return on investment to society as a whole, without regard to who contributes the resources and who obtain the benefits. The state government or the central government is interested in the economic analysis of a canal automation project to justify disbursements. Financial analysis, on the other hand, is used to determine the inflows and outflows of funds of project entities and of the farmers and other water users. While economic analysis and justification may or may not be needed for a given canal automation project, its financial feasibility is required for the successful implementation of the automation project.

Economic and financial analyses should not be limited to only the costs and benefits associated with operating the project facilities. Improved irrigation systems and better water management by way of automated irrigation canal systems provide each farmer with the ability to improve his on-farm management through flexible scheduling. Cost savings to the farmer and benefits from increased crop yields, better quality of products and ability to diversify crops must also be considered in the analysis.

The computation of the benefits of an automation project is quite complex. An automation project is undertaken to improve irrigation systems so that they can meet enhanced operating criteria. Usually this implies increased water volumes and improvements in conveyance, distribution and application efficiency. These, in turn, may require the re-dimensioning of some structures and, if enough water is expected to be saved and additional land is available nearby, may lead to an expansion of existing irrigation projects by increasing their command areas.

The decision to implement a control system should not be justified solely on tangible benefits. Intangible benefits are significant on most canal projects. Estimating tangible benefits and properly describing intangible benefits related to the need to upgrade a canal operation is essential when one examines the feasibility of a proposed automation system.

Implementing automation on new projects is a comparatively simpler task than on existing projects. Built-in constraints and limitations in existing projects must be identified, evaluated and answered on a project-by-project basis. As these constraints are different in each project, their economic evaluation will also differ. It is not possible to assess the cost of automation on existing projects by rule of thumb. In the case of a new project, one can estimate a two-to-three percent cost for automation. In reality, the cost of civil, mechanical and electrical engineering structures and components in water resources projects increases during the execution of the project, the cost of electronic components either remains at the same level or decreases; thus, cost figures may come down when the cost of the completed project is considered.

Improving the operation of the Mahi right bank canal

The feasibility study undertaken in March 1982 by the French consulting firm GERSAR on improving the operation of the Mahi right bank canal concluded that it would be possible to improve the efficiency of the system with automation. According to the study, the efficiency of the network at the time was 23 percent. The irrigation authority proposed to introduce warabandi in the command area without any improvement in regulation. This would increase efficiency to 28 percent. The study recommended to have "dynamic regulation" on the canal system implemented in two stages. At the end of the first stage the efficiency of the system would increase to 34 percent and to 44 percent by the end of the second stage. The pilot project was selected to cover 100 km of the main canal and 4 400 ha of the distribution network. The cost of automation was estimated at Rs500 per ha on the main canal and Rs1 700 per ha on the distribution network, as of 1982.

Canal automation on the Sardar Sarovar project

The feasibility study presented in April 1990 by the Gujarat Communications & Electronics Co Ltd on a control and communication network for the Narmada canal proposed a supervisory control system based on the controlled volume concept. The Narmada main canal has a designed discharge capacity of 1 134 cumecs at its head tapering down to 71 cumecs at the Gujarat-Rajasthan border and it would be operated on the automation concept. The main canal has 42 branch canals. Most of them would have a designed discharge capacity of more than 8.5 cumecs. Optical fibre would be the communication medium. A canal network with a designed discharge capacity of less than 8.5 cumecs would be operated by local manual control. Information on irrigation water demand would be sent to a data collection centre through very high frequency radio. The data collection centre would be the terminal point at which the design discharge capacity of the canal system would be of 8.5 cumecs. The cost of the control system, which includes the cost of the communication system up to the village service areas, was estimated at Rs1 970 million, for a total project cost of Rs64 800 million.

As the command area of the project covers 1.863 million ha, the cost per hectare works out at Rs1057. This figure can go up if the project authority decides to extend the canal automation to the grid with a discharging capacity below 8.5 cumecs. It is difficult to come out with a realistic figure of the cost of canal automation until automation has been implemented. Also, in the case of this project, the cost of civil, mechanical and electric works incurred for the control structures is not included in the cost of canal automation, as it is a component of the overall project cost.

The breakdown of the cost estimate of Rs1970 million is as follows:

Sr. No


Cost (Rs million)



Control system (computer system, remote terminal units sensors and controllers)


Up to 8.5 cumecs discharge capacity canal system


Fibre optic communication network


Up to 8.5 cumecs discharge capacity canal system


VHF Communication Network


Below 8.5 cumecs discharge capacity canal system


Time division multiplexing network


Up to 8.5 cumecs discharge capacity canal system



1 970.0


Dynamic regulation on the Majalgaon right bank canal

A pilot project of "dynamic regulation" has been selected for the Majalgaon right bank canal, covering 100 km in length for the main canal, 18 km for the Ganga Massla branch canal and its distribution systems.

The initial cost estimate of the pilot project, at the 1992-93 price level, was Rs30 million plus 7.3 million French Francs. At the conversion rate of FF1 = Rs7.5, the total estimated cost of the pilot project was Rs84.75 million.

The detail of expenditure incurred on the various components of the pilot project is as follows: Rs17.8 million for civil engineering works, Rs28.7 million for mechanical engineering works, Rs90.1 million for electrical and electronic components. This means a total expenditure of Rs136.6 million. The cost of dynamic regulation works out at Rs1 663 per ha on the Majalgaon canal, Rs2 961 per ha on the Ganga Massla branch canal and Rs3 755 per ha on the Minor branch canal.

The cost of canal automation on an existing irrigation project and on a new project cannot be compared, as the built-in constraints in an existing irrigation project will not only limit the degree of automation but also increase the cost by way of remodelling the existing canal systems. It can be concluded that the cost of automation on a main canal can vary from Rs1 500 to Rs2 000 per ha and that on a secondary canal from Rs3 000 to Rs4 000 per ha.

The cost of improved water control methods depends on the degree of automation desired. Even though supervisory control may amount to about one and a half percent of the project cost, it is not desirable to directly employ the said technique. When new technology is applied, one must keep in mind that high technology by itself has not been found to be very effective. It has to be matched by a proper environment and by proper user response. A farmer can receive the maximum possible benefits if there is flexibility in water distribution in terms of frequency, rate and duration. But this may not be practicable in our irrigation canal systems, as water has become a scarce commodity. If we are in a position to offer reliable water supplies to the farmers for irrigation, the goal to improve our water management plan can be considered as achieved. Water management is now viewed as a scientific art. If, by way of automation, the irrigation management authority is in a position to offer reliable water supplies and thereby boost the credibility of an organization, what monetary value can we assign to credibility?


The management of irrigation systems has gained importance over the last five decades due to a tremendous increase in irrigated area in India, primarily as a result of massive investments in new and existing surface irrigation projects. There has been a growing realization of possible improvement in water management for a more efficient use of available water resources. The potential of information technology applications for improved irrigation system management was realized long ago, but concerted efforts on this front have only been made in the last ten years. The use of computers, communication and information to control irrigation systems will yield many benefits, resulting in obvious economic savings and in intangible benefits whose value cannot be measured in monetary terms.

Rehabilitation and modernization of the existing water resource projects can be carried out under three main headings, engineering, agronomy and administration.

The engineering side includes modernization and rehabilitation of all headwork and their replacement where they have outlived their usefulness, and modernization of canals, canal structures, in particular the regulating devices, provision of additional cross regulators, permanent outlets and on-farm development works such as field channels, field drainage and land levelling.

The agronomic side includes the review of current cropping patterns, scientific assessment of crop water requirements to upgrade the system to meet the new demand, adoption of high-yielding varieties, propagation of proper cultural practices and so on.

The administrative side includes the consolidation of land, volumetric supply of irrigation water, changes in water rate policy and the like.

All of this can be achieved by improved water management at farm level, keeping in mind the existing constraints of the physical system and its operational constraints.

It is easier to plan and design a new project to be operated on the canal automation concept than to implement that concept in existing water resource projects. Physical and operational constraints must be evaluated and based on the impact of each constraint, the dynamic system design approach will have to be formulated to produce an economical technical solution.

With the exception of Sardar Sarovar, on all projects where canal automation is either planned or being implemented, it is done basically with a view to carry out the remote monitoring of the system through either manual control or local automatic control to achieve reliability in water flows. As the systems have their own constraints, the first step cannot be better than the one planned and it should not be treated as the final step, as we have to achieve an irrigation efficiency of about 60 percent in times to come.

Water is no longer defined as a natural resource but as a commodity, the value of which has been recognised both at administrative and farm levels. Unless reliability in irrigation is achieved, all other efforts to boost the irrigated agricultural sector will not reach the required goal. With limited water resources, it is now the responsibility of the engineers to create water which can be used on farm by reducing the operational and conveyance losses in the system.

Inadequate water in quantity, time and space is the primary constraint on agricultural production. However, when water reaches an outlet in an irrigation system, we cannot afford to remain despondent or indifferent to its proper distribution. Experience teaches us that inefficient water management below outlets not only results in lag of use, but also leads to serious legal complications due to inequity in water distribution. Normally, tail-end users are those who do not get their legitimate share of water. Furthermore, the farmers generally irrigate their farms with as much water as possible and as frequently as possible whenever water is available. This practice cannot be continued when water for irrigation is insufficient. Application of more water to crops does not necessarily mean better yields; on the contrary, it may lead to problems of waterlogging and thereby adversely affect crop yields.

There is considerable interest among farmers in technologically and economically advanced countries over the use of personal computers to implement their own irrigation scheduling programmes. Data collection equipment gathers necessary details about evapotranspiration, rainfall and irrigation. The irrigator selects the parameters of allowable soil water depletion and application depth. Irrigation scheduling forecasts the date and amount of the next irrigation, but does not check the ability of the distribution system to supply the required flow.

Though the below-par performance of an irrigation system is primarily attributed to inefficiency in water distribution below the outlet, it is not the only factor. Problems also lie in the main system operation, and reliable supply of water to the outlet is indeed a prior requirement for success of any management scheme below outlet. Water conveyance could be readily made automatic from the main canal headwork for the scheduling of irrigation at farm level. It requires linkage of the actual requirements of the irrigated crop or plant to the farm outlet as well as to the source of supply.

Recent advances in irrigation have related irrigation scheduling to the complex climate-crop-soil relationship. Increased knowledge of soil and plant characteristics combined with better methods of measuring soil moisture content and estimating soil moisture depletion are available to predict with greater accuracy the time and actual quantity of water needed for the next irrigation. The sensor element for measuring the prevailing soil moisture content could be a commercially available instrument or even a trained technician. The information could then be fed into an automatic data-processing digital computer which has available in its memory the information concerning the characteristics of the soil such as its moisture-holding capacity, the type of plant and its maturity, an estimate of evapotranspiration and many other parameters which may affect the quantity and timing of the next irrigation. A digital computer using many reference inputs determines the irrigation schedule, which is then provided to the computer centre controlling the canal conveyance and delivery system to update the weekly and daily schedule of irrigation as set up at the start of the season, based on the data available then. Thus the assessment of water needed to be released into the main canal can be forecast on a scientific basis, and this will allow a more flexible operation of the canal system. Linkage of real-time data collection and monitoring of the climate-, crop- and soil-related parameters with the canal automation of the conveyance and distribution system is the ultimate goal, and use of information technology below outlet level will be assigned equal priority. The socio-economic conditions of the farmers and the scientific use of water to satisfy crop water requirements will determine the success of the complete approach of implementing automation from headwork to farm level.

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