Study of the Conjunctive Water Use: A Case Study of Kankai Irrigation System, Jhapa, Nepal

More canal water is provided to farmers in the head end reaches of the canal. Consecutively, the farmers at the tail end have to pump more groundwater due to insufficient irrigation canal supply. As a result, it causes over exploitation of groundwater assets. If coordinated use of surface water and groundwater supplies is done in a planned way, then water demands for the crops can meet which ultimately increases water supply reliability. This research study focuses on enhancing irrigation water distribution by simultaneously using surface water and groundwater. Kankai Irrigation System having a command area of 7000 hectares (ha) of agricultural land in Jhapa district of Nepal is selected as the study area. Our main focus is on the tail end of the main canal at the command region of the secondary canals S19, S20 and S21 having a total area of 500 ha. The optimal plan for allotting canal water and groundwater was achieved using the LINDO 6.1 optimizing software. LINDO input model has been developed for allocation of water on existing and proposed cropping patterns. After extensive study on the different cases, the optimal plan giving maximum net benefits of NPR 9612 million, utilization of surface water and groundwater 266.15 ha-m and 152.67 ha-m respectively whereas the optimal of land use 95% monsoon rice for monsoon season, 40% wheat +20% green beans +20% pulses +15% tomatoes for winter season and 95% spring rice for spring season is suggested to be adopted and implemented for the study area.