Analytic Element-Finite Volume Based Coupled Groundwater-Surface Water Interaction model for Canal Command Systems

Regional scale modeling of coupled groundwater-surface water interaction in canal command areas is difficult due to high computational requirements and data insufficiency. Groundwater plays an essential role in the interaction process to fulfil the irrigation requirement in tail reaches of canal command areas. A comprehensive coupled model is required to simulate the canal command systems by incorporating the processes: (a) saturated groundwater flow, (b) unsaturated flow and (c) overland flow. In the present work, a fully-coupled model is developed that simulates saturated groundwater flow using Analytic Element Method (AEM), unsaturated flow using analytical solution and overland flow using Finite Volume Method (FVM) based Zero-inertia model. The Capability of the developed coupled model is demonstrated for Damodar Left Bank Main Canal (LBMC) under two canal regulation scenarios for “Boro Rice” cultivation season (Jan-Apr). Major canal water shortage is observed in LBMC during this season. It can be observed from the results that hydraulic heads in the upper reach are quite high whereas it is significantly lowering down as we move away from the main canal or in the lower reach where the groundwater is the main source of Boro rice irrigation. The considerable decline in hydraulic head values can be observed in LBMC which can be justified with a decrease in water supply and an increase in the area under Boro rice cultivation.