Performance Appraisal of Irrigation Water Distribution within the Abshar Irrigation Districts’ Main and Lateral Canals in Normal and Water Shortages Operational Scenarios

By developing a hydraulic simulator model of flow in irrigation canals, this study proceeded to spatially evaluate the adequacy of irrigation water distribution in the main and secondary canals of the waterfall irrigation network located in Isfahan province. For this purpose, a water distribution simulation between main and secondary canal catchments was performed during an irrigation season, based on spatial analysis of the water distribution performance adequacy index. According to what is done, daily distribution and delivery planning based on the information of water supply, water sales, and specified share for each second and third-degree intake valve, and with a simplified integral-delay mathematical model in MATLAB environment was linked. Five exploitation scenarios, representing normal conditions, waterlogging, and water scarcity, were considered following the prevailing patterns of surface water allocation - based on information collected in the last ten years from the irrigation network operation office. The simulation results in the main and secondary canals indicate a frequently decreasing trend of water delivery adequacy from upstream to downstream catchments, so that the adequacy index under water deficit scenarios of five, 15 and 30 percent in the range of 41-69 percent, respectively, 95-29 percent and 65-19 percent. The required water has reservoirs located downstream of the main canals. In addition to the nature of upstream control of the operation, the justification for this phenomenon is the inefficiency of the traditional manual operation method and the insufficient flexibility of water level adjustment structures and reservoirs in the reliable distribution of irrigation water under water scarcity scenarios. With the decrease in inlet flow due to water shortage, the vulnerability of the water distribution process in the downstream catchments has increased, and the favorable water delivery conditions can be seen only in a limited number of catchments located at the beginning of the main and secondary canals.