Modeling approach for the assessment of recharge contribution to groundwater from surface irrigation conveyance system

Rice–Wheat rotation system utilizes surface, ground and rain water resources conjunctively. Recent studies have shown increasing contribution of groundwater for crop irrigation. As the system utilizes water pumped from the underlying aquifer and partly seeps back, a cycle of recharge and discharge continues. Sustainability of groundwater system for the on-going drought in the country depends mainly on the recharge of the aquifer. The reported study was, therefore, carried out to measure and assess the recharge contribution of a distributary of canal in Punjab, Pakistan. Assessment of recharge through distributary was carried out using a groundwater flow “MODFLOW” model, which utilized the observed watertable, climatic, crop and soil for a period of about 1 year in addition to hydraulic conductivity, evapotranspiration and aquifer characteristics data. The requisite primary data for “MODFLOW” were collected from field and secondary data from public sector organizations dealing with water. Model calibration involved changing input parameters within reasonable limits until acceptable matches were obtained between the observed and simulated water levels for all observed hydrographs. The external inputs such as, recharge through irrigation, precipitation, stresses due to evaporation, lateral flow and stream were simulated to calculate the monthly water budget of aquifer. As concluded, recharge contribution was 16.5% of the inflow rate of the distributary. Using predicted results of the model a relationship between recharge (R) and discharge (Q) was also developed. Although, the presented results of recharge contribution were limited to one distributary of canal irrigation system, yet the developed methodology can be extended to the other canal systems of the Indus Basin.