A distributed physical approach for surface-subsurface water transport modeling in agricultural watersheds

Surface cover and soil type have a major influence upon groundwater recharge and groundwater quality in agricultural watersheds. However, several hydrological models focus on simulating groundwater recharge without including the influence of agricultural practices and soil characteristics. In this study, ANSWERS, a distributed parameters surface nonpoint source model has been modified to include the simulation of water transport in the vadose and saturated zones. This model takes into account the spatial and temporal variability of crop cover and management practices, and the spatial variability of soil type and rainfall distribution. It is physically based and uses parameters that can be easily determined from readily available soil and plant information. It has been validated at multiple scales: local scale, field scale and watershed scale. At the local and field scale, it predicts accurately drainage below the root zone and evapotranspiration on different type of soil cover. At the watershed scale, it reproduces well the piezometric levels and trends of variation. (C) 1997 Elsevier Science B.V.