Enhancement of physical representation in a basin-scale hydrologic model, SWAT

Abstract

In the development of hydrologic models, numerous concepts and empirical equations related to hydrologic processes have been included into hydrologic numerical models. With calibration, these models generally give reasonable simulation results and can meet the practical requirement. However, those empirical equations in the models usually constrain the expansion of their application mainly due to the lack of representing related physical processes. This paper presents an improvement of updating hydrologic representation of a basin-scale hydrologic model, soil and water assessment tool (SWAT) (Neitsch et al., 2005; Arnold et al., Journal of the American Water Resources Association 34(1) (1998) 73–89), by using physically-based processes. In SWAT, the steady-state response of groundwater to recharge is used to compute the baseflow, and the process of re-evaporation is used to simulate the water movement from the shallow aquifer into the overlying unsaturated zone (Neitsch et al., 2005). However, these two processes cannot reflect properly the influences of basin topography and dynamic water table depth. This study is to present a more physically-based method to simulate re-evaporation and baseflow by incorporating the features of a topographic-based hydrologic model, TOPMODEL (Beven and Kirkby, Science Bulletin 24 (1979) 43–69). The new model, so-called SWAT-TOPMODEL, is applied to the East River basin in South China, and the study results show that the new model can provide more reasonable simulation of these two processes than SWAT.