Recent Low-Flow and Groundwater Storage Changes in Upland Watersheds of the Kanto Region, Japan

Abstract

Annual trends in baseflow and groundwater storage over the past 40years are deduced from stream flow observations in four upland catchments in the northern parts of the Kanto region. The analysis is based on the assumption that baseflow is an exponential decay function of time, which yields a linear relationship between storage and baseflow. These catchments are part of the water supply system for the Greater Tokyo metropolitan area, and groundwater constitutes an integral component of their storage capacity. Although the data exhibit great variability from year to year, no evidence was found that any persistent or systematic changes in low streamflow regime and in groundwater storage have taken place in this region over the period of record.