Field assessment of the water saving potential with furrow irrigation in Fergana, Aral Sea basin

The Aral Sea basin is a region that faces water scarcity due to aridity and man-made desertification. To reduce the disproportion between water demand and supply improved water management is required, particularly aimed at water saving and conservation in irrigated agriculture. One main issue is demand management by reducing the farm irrigation water demand by improved crop irrigation management since the modernization and rehabilitation of the conveyance and distribution systems are presently out of the scope in Uzbekistan. Under this perspective, the improvement of furrow irrigation systems, which are used on 98% of the irrigated lands, is a main issue. To assess the potential for improving the performance of furrow irrigation in the central part of the Fergana Valley, Uzbekistan, a set of evaluation experiments was carried out. Irrigation management alternatives included several furrow inflow rates (1.2-2.4 l/(s furrow)) and furrow lengths (130 and 400 m); comparing every-furrow irrigation with alternate-furrow irrigation. Results were evaluated through the application efficiency (Ea), the distribution uniformity (DU) and total applied irrigation depths. The best performances were obtained for alternate long furrows adopting the inflow rate of 1.8 l/(s furrow), which produced high Ea and DU, superior to 80 and 83%, respectively, and led to seasonal water savings from 200 to 300 mm when compared with actual water use in every-furrow irrigation. Large water saving also resulted from reducing the irrigation cut-off times in every-furrow irrigation, corresponding 150-200 mm through the irrigation season. Also, improving the multi-tier reuse method when adjusting the cut-off times in agreement with the inflow rates produced high irrigation performances and water savings larger than 300 mm for the season. The field research provided information for alternative approaches to be further considered, such as surge-flow irrigation aiming at reducing advance times and tail-end runoff.