Analysis of the effects of the groundwater scheme introduced into the land surface model on estimation of river discharge

Abstract

A hydrologic model is required to estimate both floods and droughts accurately for integrated water resources management. In the past study, the authors introduced a groundwater scheme into a land surface model, SiBUC, which is coupled with a flow routing model 1K-FRM, to reduce the underestimation of low streamflow. In the groundwater scheme, all subsurface runoff is assumed to recharge the groundwater. That model could improve low streamflow in most of the Kyushu river basins, but, resulted in overestimation in some basins. In this paper, we attempted to derive the better estimation by changing the parameters of recharge rate and intensity of groundwater runoff. As a result, overestimation of low streamflow can be reduced by the smaller recharge rate set at Hitoyoshi station in Kuma River. However, it was found that the most suitable parameter setting was dependent on the year. It suggested further improvement of the groundwater scheme.