Modelling the interaction of surface and subsurface water flow by linking TOPMODEL and MODFLOW

Abstract

A coupled ground water–surface water model was used to quantify the hydrological processes in a lowland watershed. The model was constructed by coupling TOPMODEL and MODFLOW without writing new code for the integrated model. Meteorological, land use and soil type data for the Tenmile watershed, USA, were used to run TOPMODEL, which partitions precipitation into evapotranspiration, runoff and recharge. The ground water model, MODFLOW, is driven by recharge derived from TOPMODEL and provides water table elevation and baseflow. The coupled model was calibrated and validated with stream discharge and ground water head data for the period 1968 to 1972. Nash-Sutcliffe model efficiency (E) and correlation coefficient (r) were used to evaluate model behaviour. The model demonstrated good performance, with average E and r values greater than 0.7 for stream flow and ground water head during calibration and validation. Despite obvious challenges in harmonising the different spatial and temporal discretisation in surface water and ground water models, the results from this study demonstrate that the coupled model is capable of simulating hydrological processes in the study area and that with further improvements, it can be a useful tool for integrated management of surface water and ground water resources.