Effects of the lateral and vertical expansion of the water flowpath in bedrock on temporal changes in hillslope discharge

Abstract

Many researchers have emphasized that water flow through fractured bedrock is a dominant contributor to water runoff from hillslopes during baseflow. However, the first-order (main or dominant) controls on water flow through fractured bedrock are not fully understood. We measured the water flow rate from 12 bedrock fractures in a first-order catchment in Ibi, central Japan. Here we showed that the depth of the hydrologically active bedrock controlled temporal changes in water flow rate from bedrock fractures, whereas the contributing area of flow in the hydrologically active bedrock had only a small impact on temporal changes in water flow rate from bedrock fractures. This indicated that although previous studies have mainly examined the influence of lateral expansion of flowpaths on the hillslope discharge, the role of vertical expansion of flowpaths on the hillslope discharge can be important. Copyright 2008 by the American Geophysical Union.