A DISTRIBUTED PHYSICAL APPROACH FOR SURFACE-SUBSURFACE WATER TRANSPORT MODELING IN AGRICULTURAL WATERSHEDS

Surface cover and soil type have a major influence upon groundwater re charge and groundwater quality in agricultural watersheds. However, se veral hydrological models focus on simulating groundwater recharge wit hout including the influence of agricultural practices and soil charac teristics. In this study, ANSWERS, a distributed parameters surface no npoint source model has been modified to include the simulation of wat er transport in the vadose and saturated zones. This model takes into account the spatial and temporal variability of crop cover and managem ent practices, and the spatial variability of soil type and rainfall d istribution. It is physically based and uses parameters that can be ea sily determined from readily available soil and plant information. It has been validated at multiple scales: local scale, field scale and wa tershed scale. At the local and field scale, it predicts accurately dr ainage below the root zone and evapotranspiration on different type of soil cover. At the watershed scale, it reproduces well the piezometri c levels and trends of variation. (C) 1997 Elsevier Science B.V.