Integrated surface and groundwater modeling to enhance water resource sustainability in agricultural watersheds.

Management of water resources is essential to maintain sustainable agricultural productivity and preserve groundwater and surface ecosystems. The long-term sustainability of these systems depends on the understanding of complex surface-groundwater flow interactions at different temporal and spatial scales, and the impacts of agricultural practices on water use. To support these efforts, an integrated AnnAGNPS-MODFLOW modeling technology is proposed and evaluated. It combines the capability of the AnnAGNPS model to detailed characterization of farming practices with groundwater flow estimation tools of the MODFLOW model. The AnnAGNPS-MODFLOW model was evaluated in Upper Sunflower River watershed at the Lower Mississippi River Alluvial Plain. The integrated modeling technology in conjunction with observed values of streamflow at the outlet and well water levels were used to estimate irrigation strategies with application rates varying in time and space at field scale. Utilization of improved irrigation characterization have provided evidence of the sensitivity of streamflow and groundwater levels to irrigation strategies. Simulation results indicate that a reduction of irrigation application rates by 20–40% can impact aquifer long-term water levels. This finding supports the need to investigate more efficient irrigation strategies to promote the aquifer sustainable use. The proposed technology provides a management tool critical to understanding and evaluating the impact of agricultural practices, irrigation, and aquifer recharge strategies that are important to sustaining water resources in irrigated agricultural watersheds. • Integrated AnnAGNPS-MODFLOW modeling technology for assessing the impact of farming practices on groundwater resources. • Estimation of irrigation rates varying in time and space at field scale using iterative optimization procedure. • Quantification of relationships between surface streaflow loads, irrigation adoption, and aquifer levels. [ABSTRACT FROM AUTHOR]