Spatial discretization of distributed hydrological response units for SWAT

The Soil and Water Assessment Tool (SWAT) is a well established eco-hydrologic model. For the semi-distributed hydrological model, Hydrological Response Units (HRUs) are the basic modeling units, which are defined by land use, soil and slope. Land surface patches within one Hydrological Response Units (HRUs) should bear identical hydrological properties (including land use, soil, slope and management) and thus have similar hydrological responses. However, it is difficult to determinate the spatial locations and to describe the interactions between different HRUs. This study proposed one schema to discretize HRUs for SWAT on the basis of generalized data input. Within a small watershed of Taihu Basin, the data of land use and soil were generalized for discretizing SWAT HRUs. The SWAT model was modified with the discretized HRUs. The resulted showed that the SWAT improved by discretization schema could be more sensitive the runoff lag process and thus achieved better simulation accuracy.