Abstract
Many of existing hydrologic models computing flow dynamics at mountainous slope grid cells assume impermeable bedrock. However recent field studies have reported the importance of mountainous groundwater in bedrock to control the dynamics of subsurface flow in soil layer. The objective of this study is to develop a simple groundwater model for mountainous bedrock aquifer incorporated to a distributed hydrologic model, in particular a Rainfall-Runoff-Inundation (RRI) model. The model assumes the exponential decline of hydraulic conductivity, so that it can avoid defining the unknown bottom boundary of the aquifer. The model was applied to two Japanese catchments and its performance was tested in terms of recession and dynamic storage characteristics. At Rokko catchment with steep slopes underlain by weathered granite, involving the groundwater component showed the significant improvement for representing the observed hydrograph characteristics.
