Where is the direction of future hydrologic modeling?

Abstract

Along the development of hydrologic models, a numerous concepts and empirical equations related to hydrologic processes have been included into different hydrologic numerical models. With calibration, these models generally give reasonable simulation results and can meet certain practical requirements. However, those empirical equations in different models usually constrain the expansion of their application mainly due to the lack of representing related physical processes. To understand the direction of future hydrologic modeling, in this presentation, an improvement of updating hydrologic representation by using physically-based processes in a basin-scale hydrologic model, Soil and Water Assessment Tool (SWAT), is presented. 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. However, the simulation of these two processes does not consider the influence of topography and dynamic water table depth. Therefore, it is a question whether we should update the physical representation in SWAT. To explore the question, this study is to present a more physically-based method to simulate groundwater discharge (i.e. re-evaporation and baseflow) by incorporating the features of a topographic-based hydrologic model, TOPMODEL. The updated SWAT with TOPMODEL features is applied over the East River basin in South China, and the study results show that the integrated SWAT-TOPMODEL can provide more reasonable simulation. The results of the study reveal, to some extent, the direction of future hydrologic modeling would be to improve the physical representation of terrestrial hydrologic processes by improving our understanding.