Watershed Configuration and Simulation of Landscape Processes with the SWAT Model

Recent and future river basin management requires a more spatially distributed description of basin hydrology and nutrient transport processes to enable land use management as a process controlling factor to realize sound river basin management. The spatial description of these processes in the Soil and Water Assessment Tool (SWAT) watershed model is presently realized by aggregating the flows from overlaid soil and land use patches in subbasins with averaged slope angles. Many concepts with different degrees of complexity have been developed in river basin modelling to aggregate units with similar hydrologic behavior (Hydrological Response Units). Watershed configuration for SWAT currently consists of: 1) subbasins defined by surface topography and 2) hydrologic response units in each subbasin to account for heterogeneity in soils and land use. The hydrologic response units do not account for landscape position within the subbasin. Until recently, many existing watershed models did not implicitly account for landscape processes within a subbasin. Other smaller scale models do account for hillslope transfer (e.g. WEPP, REMM, APEX, HYDRUS2D).