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J.A. Morabito, L. Fornero, L. Emili, Andean Regional Center, INCYTH, and R. Thomé, General Department of Irrigation, Mendoza, Argentina |
SUMMARY
Mendoza is located in the arid zone of mid-west Argentina. It has 293 557 ha under irrigation (Gobierno de Mendoza, 1993). The main crops are grapes, fruit trees, vegetables and fodder. Since 1884 water administration in Mendoza province has been decentralized and democratic. Due to the fluctuating demands for water and the diversification of uses, such as irrigation, urban, industrial and recreation, efficient water use and the monitoring of water quality are very important in Mendoza. In the irrigated area, ownership, served area, crop pattern and water availability change yearly. The improvement in water use can be accelerated with computational models that use precise data, organize the information collected, plan the actions and quantify the technical, economic and administrative performance of the organization.
The purpose of this paper is to show the results of applying the SIMIS model (van den Bulcke et al., 1994) to a pilot area irrigated by the Matriz Gil secondary canal (3303 ha) from the Mendoza River and to analyse the advantages of this use. It was necessary to survey: the irrigation network, the plots, the main crops, the landowners, and the distribution efficiency. Water delivered to the Matriz Gil secondary canal was measured. Incomes and expenditures in operation and maintenance (O&M) and yield obtained were collected from the water users associations. The SIMIS program was used to process and store this information. In order to evaluate the performance of the administration and improve operations, performance indicators are analysed (technical, economic and administrative).
Results obtained for the 1994 season show a value of 71% for the sustainability of the irrigated area and 34% for adequacy of irrigation water. Regarding economic-administrative performance indicators, it was possible to calculate O&M expenditures of $US 12.11/ha, the relative cost of water fees is 2.4 % of estimated production cost, 1.9% of total incomes of the project and 8.7% of the profit of the project.
In 1993 the overall budget of the water associations included a small investment (0.6%), and high expenditure: inspection (30%), administration (5.9%) and bank charges (4.7%).
Mendoza province is an arid zone located in mid-west Argentina. It has 350,000 hectares with water rights (Dpto. Gral. de Irrigación, 1994) and 293 557 hectares are effectively irrigated (Censo Nacional Agropecuario de 1988, Gobierno de Mendoza, 1993).
The main crops are (Censo Nacional Agropecuario de 1988, Gobierno de Mendoza, 1993): grapes (53.6%), fruit trees (16.7%), vegetables (11.8%), fodder and cereals (8.9%) and others (9.0%).
Since 1884 water administration in Mendoza province has been decentralized and democratic. The General Department of Irrigation (DGI) is responsible for the provincial water administration; it is an autonomous and autarchic governmental agency. Since water administration is decentralized, water distribution from secondary canal to farm inlet is the task of water users associations (Inspección de Cauce).
The irrigated area is divided in five rivers, one of the most important is the Mendoza River. It has 92 920 ha with water rights and 82 042 ha receiving water for irrigation. As water is scarce and in increasing demand in Mendoza, considering its multiple users (irrigation, urban, industrial and recreational), it is necessary to ensure its quality and improve the water use. The actual availability is 3 500 m3 per person/year and in the future this value will decline (Chambouleyron, 1994). The project efficiency (ep) in the Mendoza irrigated area is 30% (Chambouleyron, et al., 1982).
The irrigated areas are dynamic, with every year modifications occurring in water rights, in cropped area, in crop pattern and water requirements that affect the time schedule and flow to be distributed. On the other hand, water availability changes every year according to weather and hydrological conditions. The influence is great because there is no storage dam.
In the last ten years computational models have been developed. With these models it is possible to systematize precise and updated information from a project, helping water users associations to improve water management. It is necessary to evaluate these models to verify their effectiveness and adaptability to regional conditions and to analyse the advantages of a general use.
The objective of this paper is to show the results of applying the SIMIS model (van den Bulcke et al., 1994) to the Mendoza Irrigation Area and to analyse the possible advantage of its use.
MATERIAL AND METHODS
The SIMIS program has been developed by FAO with the aim of facilitating the operational activities in irrigation networks and improving integral administration of water. It is a user-friendly program written in dBASE IV. The main menu shows four options: Projects, Project Support, Project Management and Configuration. The Project Support module includes: climate, crops, soils, physical infrastructure, land tenure, machinery and implements, and staff. The management tools of the projects are: agricultural activities, crop water requirement, seasonal irrigation planning, irrigation scheduling, water consumption, accounting, operation and maintenance activities and costs, and water fees.
The user can easily handle the program completing and continually updating the data. SIMIS is an information system that enables users to analyse each plot of the project and its aggregations at higher levels (global vision) of the project.
The Matriz Gil secondary canal (Rama Gil) from the Mendoza River was selected as a pilot area. It receives water from the Cacique Guaymallén primary canal and delivers water to 3 303 hectares according to water rights on the left bank of the Mendoza River. The command area of Rama Gil is an important agricultural zone, with serious problems of land subdivision caused by urban expansion.
Rama Gil delivers water to 4 farm intakes and 6 tertiary canals (hijuelas) that run parallel until the Pescara drainage canal (Figure 1). Most of the area is irrigated by superficial methods (graded furrows and graded border) with low application efficiency (39%). Some farmers have performed a better land systematization that has resulted in higher application efficiencies (70%). The canal is administered by a 'Inspección de Cauce'.
To implement the application it was necessary to survey the irrigated network and hydraulics structures: flume, gate intake, hydraulic diversion structures to tertiary canals, gates of the 191 farms and drainage structures at the end of tertiary canals to the Pescara drainage canal. Figure 1 shows soil individualization of each farm. The soils are medium (Class 2) to fine (Class 1) texture, fertile, superficial, with gravel and good drainage.
FIGURE 1 - Area irrigated by Rama Matriz Gil: irrigation network, plots and soils
Input data were completed according to the network system module. Each canal and hydraulic structure was identified, following the water way, from the upper part to the plots. General information about each canal and its structures is in the databases.
A detailed analysis of the water registration rights (according to the DGI, 1994) of that canal was made. Each plot was located in its correct gate with the help of gatemen from the Gil area. For each intake it was possible to identify: name of owner, surface with water right, existing crops and number of water right according to DGI.
RESULTS
The crop pattern of Rama Gil was obtained using the agricultural activities module: grape (746 ha), olives (603 ha), fruit trees (355 ha), vegetables (236 ha), forest (298 ha), fodder (93 ha) and uncultivated (906 ha). Twenty-eight percent of the area is uncultivated.
The Penman-Monteith Reference Evapotranspiration (ETo) was obtained with climatic data from the Chacras de Coria weather station (FCA-UNCuyo, 1995), located in the pilot area. Annual ETo was 1 194 mm and effective precipitation 103 mm. Water shortage for this year was 1 091 mm.
The maximum evapotranspiration was obtained for each crop for 1994. These, expressed in mm/year were: grape (745), olives (823), fruit trees (888), forest (950), tomatoes (536), garlic (563) and fodder (1 234).
Water distribution in the Mendoza River and Rama Gil
Depending on actual flow, the irrigated area of the Mendoza River is divided into two or three sectors. Table 1 shows the criterion for water distribution. For example, when the river flow is less than 30 m3/s, all the water is delivered to one sector at a time with an interval of eight days. Sector 1 receives water for a period of 66h 33min; sector 2: 67h 24min and sector 3: 58h 03min.
TABLE 1 - Irrigation sectors of the Mendoza River
|
River flow (m3/s) |
Sectors |
Time (hh min) |
Interval (days) |
|
Q < 30 |
1 Upper Guaymallén and Lower San Martín |
66 33 |
8 |
|
|
2 Lower Guaymallén and Upper San Martín |
67 24 |
|
|
|
3 Lower Reach |
58 03 |
|
|
30 < Q < 40 |
1 Guaymallén |
96 27 |
8 |
|
|
2 San Martín and Lower Reach |
95 33 |
|
|
Q > 40 |
1 Guaymallén and San Martín |
120 00 |
7 |
|
|
2 Lower Reach |
48 00 |
|
Rama Gil is located in the upper part of the Guaymallén canal and water distribution is by intervals (turnout). A Vieytes street divides each tertiary canal into two sections. All intakes of a section receive water at the same time. Flow is divided by each fixed hydraulic structure and gates, considering surface water right. The gatemen aim to deliver the same volume of water to each hectare with water right. The flow is proportional to the size of the plot. When farmers do not pay, they do not receive any water.
If delivery time to Rama Gil is 66h 33min, section 1 receives water for 36h and section 2 for 30h 33min. If there are two sectors of irrigation with an interval of 8 days, water is delivered for 53h at section 1 and 43h 27min for section 2. Every eight days delivery changes from 1 to 2 and vice versa.
If there are two sectors of irrigation every seven days, water is delivered for 120h to all intakes. The Palma tertiary canal always delivers water to all intakes.
It is important to note that water distribution has many problems: little scheduling (water flows away without being delivered), poor control of water (much routine), and small flows when farms are small.
Flow measured at Rama Gil
The flow rating curve of the flume at Rama Gil intake was measured. Every day when water was delivered into the secondary canal, the flow (through gauge reading) and time were recorded. Figure 2 shows the timetable of flows delivered during 1994. For each delivery, opportunity initial and ending time, and mean flow (l/s) are indicated.
Travel time from the Cipolletti diversion dam to Rama Gil is 1h 30min. Travel time in Rama Gil changes with actual flow. When the flow is low (2 000 l/s), it takes 1 hour 10 minutes and in summertime, when the flow is high (3 000 l/s), travel time is about 50 minutes, with a mean flow travel time of one hour. In the tertiary canals the travel time is two hours.
Proportion of division flow at tertiary canals
As the hydraulic structures are not in good condition, it was necessary to measure the actual flow into each tertiary canal.
Table 2 presents the percentage of total flow (% Q) allowed into each tertiary canal. The same table shows the theoretical flow in relation with the canal widths: tertiary canal width/secondary canal width (% of canal width).
Table 2 shows that major differences are registered in the Delgado and Terreros tertiary canals. For example if the flow in the Rama Gil secondary canal is 2 220 l/s at the hydraulic diversion structure of the Delgado tertiary canal, the theoretical delivered flow should be 2 220 * 0.1840 = 408 l/s, but the actual delivered flow was 2 220 * 0.2638 = 586 l/s, 43% more than the flow that the diversion structure was designed for.
TABLE 2 - Division of flow at Rama Gil
|
Tertiary canal |
% canal width |
% Q |
Difference % |
|
Gil |
18.49 |
19.34 |
+ 0.85 |
|
Bóvedas de Corvalán |
28.08 |
26.32 |
- 1.76 |
|
Delgado |
18.40 |
26.38 |
+ 7.98 |
|
Terreros |
31.71 |
25.93 |
-5.78 |
|
Palma |
59.40 |
57.98 |
- 1.42 |
|
Estrella |
40.59 |
41.83 |
+ 1.24 |
Irrigation efficiencies
Distribution efficiency (ed) is defined as (Bos and Nugteren, 1983) the relation of volume of water delivery to the plots plus other users in relation to the volume of water delivered to the distribution systems. For this study measured flow was done in Rama Gil and in two tertiary units (Gil and Palma) at different dates.
Rama Gil was divided in three parts. The first part of Rama Gil is from the beginning until the Bóvedas de Corvalán tertiary canal: ef = 99% in 710 m; the second part from Bóvedas de Corvalán until the Terreros tertiary canal: ef = 98.4% in 1 090 m; the last part from Terreros to the Palma canal, ef = 98.3% for a distance of 1 610 m. Total efficiency of Rama Gil was calculated as 95.7% for a length of 3 410 m. (The water losses ratio is 4.3%/3410 m = 0.126%/m).
The efficiency of tertiary unit Gil was obtained measuring the circulating flow between intake 13 and 17 for a distance of 2 160 m, the result was an efficiency of 94% (6% of losses/2 160 m = 0.27 %/m). The efficiency of tertiary unit Palma was measured in the same way, between intakes 9 and 17 (1 926m), the efficiency measured was 95.4% (5.5% of losses/1 926 m = 0.28 %/m).
The distribution efficiency (ed) was obtained considering the efficiency at the secondary and tertiary canal of the pilot area. The mean ed value for the irrigated area of Matriz Gil was estimated at 87%. This information will be used in the SIMIS Irrigation Scheduling module and will be presented in another paper.
Performance indicators
Figure 3 shows water irrigation requirement and water supply for 1994 at Rama Gil, as resulting from the model processing.
Figure 4 shows adequacy performance indicators for 1994, defined as the ratio of water requirement to water supply. High values mean that water supply is close to water requirements, sometimes not enough to compensate the losses of the systems (water shortage). Low values indicate waste water that affects the environment (elevation of phreatic level, soil salinization, fertilizer contamination, etc.).
This performance, indicator is close to the Project Efficiency (ep) defined as the ratio of measured crop evapotranspiration to project water supply. The mean annual value of adequacy for Rama Gil was 34%.
Another interesting indicator is the total annual volume of water per unit of surface (TAVWUS). At Rama Gil intake a mean volume was measured (44 808 498 m3/year; 1978/88). This volume divided by 3 303 ha with water rights means 13 566 m3/ha year, but considering the actual cultivated area (2 331 ha) that value changes to 19 223 m3/ha year.
FIGURE 3 - Water irrigation requirement and water supply (1994)
The sustainability performance indicator defined as the ratio of actually irrigated area to planned irrigated area (here water right area) is 2 331/3 303 = 71%. Other performance indicators obtained are:
· Mean surface cropped area per intake: 2 331 ha/191 = 12.2 ha.
· Perennial crops area divided by total crop area: 2 002 ha/2 331 ha = 86%.
FIGURE 4 - Performance indicator of adequacy at Rama Gil (1994)
Economics and administrative indicators
It would be possible to improve the integral administration of the water and increment users participation if, every year, the 'Inspección de Cauce' made a revision of the expenditures and incomes and organized the distribution of the budget for the next year.
For that purpose SIMIS can help water user associations improve the management of irrigation water over time and inform the farmers about the budget, the state of the current account and the distribution of expenditures.
Analysing the budget and expenditures distribution of Rama Gil for the 1993 period it was possible to evaluate the economic and administrative management.
Total expenditures of Rama Gil were ($US 39 198) corresponding to 3 237 ha of water right, which results in a unit cost per hectare of operation and maintenance of $US 12.11 ha/year.
It was useful to illustrate the monthly balance of the 'Inspección de Cauce' during the year which seems to be an interesting indicator. The distribution of expenditures in items was calculated analysing 1993 management. The values obtained are in items: operation (44.3%), 'Inspección de Cauce' expenditures and per diem (30%), maintenance (10.6%), administrative services (5.9%), bank charges (4.7%), others (3.9%) and investments (0.6%).
It is interesting to see the very low expenditures on investment and the high values for 'Inspección de Cauce' expenditures and per diem. Others items such as administrative services and bank charges could be reduced.
The annual fee for irrigation water was in 1993 $US 34.37 ($US 16.28 corresponding to 'Inspección de Cauce' O&M, and $US 18.09 to governmental administration). Considering ed = 87% it was possible to estimate the cubic metre (m3) cost of water, the result is $US 34.37/(13 566 m3 *0.87) = $US 0.0029/m3, eight times lower than the unit volume of groundwater obtained for the same area, $US/0.024/m3 (Hiramatzu and Pissi, 1995).
The reports of agricultural production, productivities and incomes of the SIMIS program gave us the opportunity to obtain three indicators that enable the project's evolution to be analysed. These indicators obtained with a water fee of $US 39 (1994) are:
· relative water fee with respect to mean cost production of the projects: 39/1 606 = 2.4%.
· relative water fee with respect to mean total incomes of the projects: 39/2 056 = 1.9%.
· relative water fee with respect to the profit of the projects: 39/450 =8.7%
CONCLUSIONS
To improve water use, maximizing production and minimizing environmental degradation are urgent targets. Models can help, but it is necessary that these tools be accurate, simple (user-friendly) and with relatively easy availability of input data. SIMIS has shown itself helpful in the general systematization of data from an irrigation project and the activities needed to complete the missing information (irrigation network plane, state of operation and conservation of the hydraulic structures, command area of each gate, identification number for water right, crop pattern, etc). It is possible to store the information for each farmer and crop, and to calculate quickly the crop pattern and abandoned surface, in this case 28%. Data summarization at various levels and criteria are readily available.
It was possible to calculate the adequacy of irrigation performance indicator for 1994, the value obtained was 34%. It is possible to analyse other alternatives of water distribution and its impact on the overall project efficiency. This aspect is not discussed in this paper.
SIMIS shows its utility in obtaining precise information for the analysis of the economic and administrative performance of 'Inspección de Cauce' and for calculating the O&M water cost to include in water fees.
With respect to the distribution of expenditures it is possible to know that farmers do not invest in the irrigation network. Visiting the area, it becomes clear that in the last 20 years no investment has been made. In general, analysing the budget shows that farmers spend the budget without any long-term plan.
REFERENCES
Bos, M. and Nugteren, J. 1983. On irrigation efficiencies. ILRI no. 19. Wageningen, The Netherlands.
Chambouleyron J., Fornero, 1., Morabito, J., Menenti, M. and Stefanini, L. 1982. Evaluación y optimización del uso del agua en grandes redes de riego. INCYTH-IILA.
Hiramatzu, K. and Pissi, D. 1995. Calculo del costo del agua subterranea. Facultad de Ciencias Agrarias de la UNCuyo, Mendoza, Argentina.
Van den Bulcke, M., Sagardoy, J,, Hatcho, N. and Bellostas, J. 1994. Manual del Usuario del SIMIS (Sistema de información para el manejo de sistemas de riego). Versión 1.3. FAO, Rome.
