Impacts of Climate and Land Use Changes on Water Resource in the Big Sunflower River Watershed

The Big Sunflower River Watershed (BSRW) in Mississippi, USA is well known for irrigated agriculture and the groundwater level has declined > 6.5 m since 1970 due to the agricultural pumpage. The cultivation area of high water-consuming crops (corn and soybean) is increasing rapidly, while the cultivation area of low water-consuming crop (cotton) is decreasing. Due to the uneven seasonal distribution of precipitation and abnormal climate, flood and drought often occur in the BSRW. Climate and land use changes are projected to have significant impacts on agricultural production. This study applies a coupled surface-groundwater model, SWAT-MODFLOW, to investigate the impacts of climate and land use changes on water resource in the BSRW. The model was calibrated and validated using monthly river flow and hydraulic head data 1996 to 2006. Future climatic conditions in the area are developed by downscaling the data of General Circulation Models (GCMs). Two representative concentration pathways (RCPs) scenarios (i.e., RCP4.5 and RCP8.5) were selected for projecting future conditions of water resources. The SWAT-MODFLOW model simulated surface-groundwater flows interactively and computed spatial and temporal distributions of hydrological processes, including surface runoff, ET, percolation, lateral flow, and groundwater return flows. These results may help decision-makers for devising sustainable groundwater management strategies in the BSRW.