The evaluation of irrigation network by using classic and new concepts of irrigation efficiency (Case study: Hamody irrigation system of khozestan)

This study was carried out to evaluate Hamody irrigation network (in an area of 3079 ha) using classic and new classic irrigation efficiency concepts. For this purpose, firstly the main district’s water inputs (irrigation, rainfall and canal releases) and outputs (actual crop evapotranspiration, drainage outflow and canal seepage) were measured or estimated during the hydrological years (2006-2009). Then, the application efficiency (classic concept) and the net and effective efficiencies (neoclassic concept) were estimated at the network level. Finally, different scenarios of water allocation were evaluated by considering new concepts of irrigation efficiency. The assessment scenarios include 65, 75 and 85% of water supply needs, 100% Crop Water Requirement (CWR) and a fraction of CWR without significant reduction in yield. The annual average outflows were 16% higher than the inflows, presumably due to canal seepage and lateral groundwater inflows from neighboring lands. Distribution, application and total efficiencies were estimated 68, 53 and 44%, respectively, indicating low irrigation performance in the irrigation network. Despite the high volume of applied irrigation water, the actual ET was 19% less than the potential ET, indicating water-stress and crop yield reduction. The assessment of surface irrigation systems using new classical approach showed that the net (0.77) and effective (0.65) efficiencies were more than the classical efficiency (0.53). The results of this study showed 19-47% water saving in allocation scenarios using the new concepts of efficiency.