Alternative Rotational Delivery Scheduling for Better Water Regime in Canal Command

A model for modifying the canal delivery schedule during the dry season has been formulated to overcome the problem of low irrigation efficiency in a major irrigation project in India. Phulnakhara Distributary of the Puri main canal system (a run-of-the-river scheme) in the state of Orissa was chosen for this study. The model adopts a procedure of daily water balance simulation in paddy field and daily moisture balance simulation in nonpaddy crops field in the crop root zone. The historical canal flow data show that the prevailing delivery schedule is continuous. In addition to prevailing a continuous delivery schedule, five alternative rotational (variable discharge, constant duration, and constant frequency) schedules were considered. The alternatives considered are: 7 days canal operation followed by 7 days canal closure (7_7); 10 days canal operation followed by 10 days canal closure (10_10); 15 days canal operation followed by 15 days canal closure (15_15); 10 days canal operation followed by 7 days canal closure (10_7); and 15 days canal operation followed by 7 days canal closure (15_7). Considering both paddy and nonpaddy crops to be grown in the command during the dry season, 7 days canal operation followed by 7 days canal closure rotational schedule were found to be the best alternative. The alternative schedule 7_7 has registered weighted average seasonal evapotranspiraton (ET) of 354 mm in comparison to 347, 342, and 352 mm in 10_10, 15_15, and 10_7 schedules, respectively. In the paddy field, schedule 7_7 registered maximum of 4 days of disappearance of water as compared to 5 days and 6 days for 15_7 and 10_7 schedule, respectively. Besides creating a favorable water regime and better crop ET, this schedule saves about 10.31% of water over prevailing (actual) water supplies.