Groundwater recharge simulation using a coupled saturated-unsaturated flow model

Abstract The coupled MODFLOW-HYDRUS software package was used to produce a saturated-unsaturated flow model for a Flood Spreading System (FSS) and its associated aquifer. The study aim to improve simulations of near-surface hydrological processes, including temporal and spatial variation in groundwater recharge rates. The coupled model was built with average RMSE=1.1 and 1.3 for calibration and validation periods, respectively. One of the features of the coupled model is separate recharge estimation from each unsaturated profile. Considering the FSS as a profile, annual recharge caused by the FSS on average is 3.5 MCM of which 0.5 MCM is natural recharge and the rest of it is net artificial recharge. Also, effects of sedimentation on recharge reduction was considered. Results shown that due to small sedimentation area relative to total study area, less than 10 percent of recharge caused by FSS was reduced as a result of sedimentation. Finally, considering aquifer area and specific yield, recharge caused by FSS makes ground water level rise by 30 cm annually.