An Alternative Rotational Delivery Schedule for Improved Performance of Reservoir-based Canal Irrigation System

Alternative delivery scheduling approaches were tried to overcome the problem of low efficiency in eastern Indian irrigation projects. The features of the existing delivery schedules in the Left Bank Feeder Canal (LBFC) system of Kangsabati irrigation project, located in the state of West Bengal, India, have been studied. Four simulation scenarios were considered in the study. These are (1) actual canal scheduling with original transplanting date (S1), (2) Integrated Reservoir-based Canal Irrigation Model (IRCIM) scheduling for usual transplanting date (S2), (3) IRCIM scheduling for 5 days advanced transplanting date (S3), and (4) IRCIM scheduling for 5 days lagged transplanting date (S4). An attempt was made to develop a year-independent alternative delivery schedule based on the analysis of 11 years simulation results with all the above scenarios. For maximum number of simulation years, model performance was better for paddy transplanted on July 24, three irrigations from the reservoir between transplanting and harvesting, and restricting the release to minimum rule curve (MRC), i.e., maintaining the stage on any day above the minimum stage actually found in 16 years period. Hence, it was proposed as the year-independent alternative delivery schedule. This alternative delivery schedule saved 18.36% irrigation water over actual schedules, but increased the crop evapotranspiration by 0.61%. The proposed alternative delivery schedule also considered both the expected dry spells as well as critical growth periods of the crop during the simulation period. Thus, it was recommended to adopt the alternative delivery schedule instead of existing delivery schedule in the future years for the LBFC system of Kangsabati irrigation project.