Coupled Simulation of Xinanjiang Model with MODFLOW

Abstract

This paper investigates the probability of integrating the Xinanjiang model, the most widely used watershed hydrological model in China, with the fully distributed groundwater model MODFLOW for processing a coupled flow simulation. Based on the flow simulation of the Xinanjiang and the SWAT model in the case study area, the correlation between the groundwater recharge and the total flow runoff is analyzed, which is then applied to compute the groundwater recharge in subbasins in the Xinanjiang model. By applying a loosely coupled modeling approach, the spatially distributed groundwater recharge is introduced into MODFLOW with the RCH package via the interface of the subbasins in the Xinanjiang model and the cells in MODFLOW; thus the integration of the two models is successfully realized. The application of the integrated model simulation in Zhangji, a groundwater-dominated area in the Huai River basin, China, demonstrates that the coupled Xinanjiang-MODFLOW simulation produces reasonable groundwater levels comparing to the observations. However the study also shows the need for further research in regarding to the improvement on Xinanjiang model in order to enable its direct integration with MODFLOW. Furthermore, the approach presented in this paper is limited to a unidirectional coupling of Xinanjiang and MODFLOW, which only accounts for groundwater level simulations, while the possible feedbacks from the surface water is neglected. More efforts are required to further facilitate the applicability and capability of the models integration.