Performance assessment of heterogeneous irrigation schemes in India
2015-09-02T11:59:45Z (GMT) by
Most irrigation schemes in India are performing poorly as seen from the average irrigation efficiency in the range of 30-40% for these projects. Hence it is necessary to study the performance assessment of these schemes to investigate the reasons and improve the performance subsequently. There are different kinds of performance measures that may vary spatially over the irrigation scheme. Hence it is necessary to use a framework for finding out the final performance index (FPI) that combines important performance measures. Hence this study was undertaken. Mula Irrigation Scheme in Ahmednagar District of Maharashtra State, India was identified after verifying that most of the needed data was available. The six performance indicators viz. Productivity, Equity, Adequacy Reliability, Flexibility and Sustainability were identified as the important one for obtaining the information on the relative preference from the farmers and first three were considered for obtaining the allocation plans. The performance of different irrigation schemes is assessed with the help of Area and Water Allocation Model (AWAM). The performance measures viz. productivity, equity, adequacy and excess were obtained by formulating the irrigation strategies based on 1. Irrigation amount: Full depth irrigation (FDI), Fixed depth irrigation (FxDI) and Variable depth irrigation (VDI), 2. Irrigation frequency (14 days, 21 days, 28 days and 35 days), 3. Water distribution: Free water distribution (FWD), Equitable distribution of seasonal water (EDSW) and Equitable distribution of intra-seasonal water (EDIW) and 4. Cropping distribution (Free cropping distribution and Fixed cropping distribution). The yield response of crops to different criteria such as soil, irrigation interval, irrigation strategy and irrigation depth, were analysed. It is found for wheat grown on all considered soils, the variable irrigation depth strategy provided better performance of irrigation scheme in terms of productivity and results in higher irrigation water use efficiency. It is concluded though that the application of water according to the variable irrigation depth strategy is operationally and from a management point of view not convenient and in current situation may not be adoptable. Though the fixed depth irrigation strategy is found to be less productive based on this research for Mula irrigation scheme, it is more convenient for operation compared to other strategies as it does not involve adoption of separate schedules for different crops. In general the area and net benefit productivity values are higher in fixed depth irrigation followed by variable depth and then full depth. The productivity values are higher in case of free cropping distribution compared to fixed cropping distribution. The equitable water distribution resulted in lower productivity compared to free water distribution. No specific trend of equity with the irrigation interval was found. Equity values are higher in case of fixed depth of irrigation compared to full depth. The equity values are higher in case of fixed cropping distribution compared to free cropping. The equity values are as expected higher or unity for equitable water distribution compared to free water distribution. The adequacy values are higher in full depth of irrigation followed by variable depth irrigation and fixed depth irrigation. It is observed that the productivity and equity are almost inversely proportional to each other. Hence the hypothesis that productivity and equity conflicts with each other holds true. Further, Analytic Hierarchy Process (AHP) was used to assign weights of different performance measures by determining the farmers relative preference of different performance measures. The average weights of different performance measures (monetary productivity, equity in water distribution and adequacy) were obtained for farmers from different reaches from the weights obtained from AHP analysis, and considerable differences were found between the weights for the head, middle and tail reaches. The values of the performance indicators were obtained from the simulation-optimization modeling (AWAM model). The different indicators were combined into a final overall performance indicator (FPI) of irrigation management in an irrigation scheme from the farmers perspective. The FPI was computed for head, middle and tail reach farmers using the weights obtained from AHP by compromise programming. It is interesting to note that the strategies that best met the farmers preferences (highest FPI), were same for middle reach and tail reach farmers however it is different for head reach. It is also interesting to note that the preferences of the head, middle and tail reach farmers, irrespective of their relative location in irrigation scheme, were best met by strategies which include the equitable distribution of water. For middle and tail reach farmers, full depth irrigation would give the highest FPI, while for head reach farmers optimised fixed depth would be best. It is also seen that for head and middle reach farmers a strategy with fixed cropping distribution and free water distribution would be worst for meeting the preferences of head and middle reach farmers while for tail reach farmers a strategy with free water and free cropping distribution would be worst. The mean values of the weights for head, middle and tail reach farmers were Productivity = 0.33, Equity = 0.31 and Adequacy = 0.36. With these weights, the highest FPI (0.85) was obtained with an irrigation strategy of Full depth irrigation with free cropping and annual equity at irrigation interval of 35 days in winter and 28 days in summer . Considering the different depth of irrigations (FxDI, VDI and FDI) the VDI and FDI are practically difficult to execute due to the data required for calculations and operational requirements of the irrigation canals. Using FxDI, a strategy with high FPI (0.83) was identified as the best feasible irrigation strategy to implement for the entire irrigation scheme: Fixed depth irrigation with free cropping and annual equity at irrigation interval of 35 days in winter and 28 days in summer . It was found that this best feasible irrigation strategy for the entire scheme was not sensitive to the weights assigned to the performance measures.