Shallow Groundwater in the Inland Kanto Plain after Groundwater Level Recovery – Temporary Changes in Hydraulic Head and Groundwater Flow

Abstract

　In inland areas of the Kanto Plain, where the groundwater level has recovered from its lowest depths because of pumping restrictions, the distribution of hydraulic heads was examined during the temporary low level of the annual cyclic change. Long-term groundwater level data from observation wells in Saitama prefecture accumulated during 25 years since 1992 were used to confirm changes to hydraulic heads of two types, with long-term and annual cyclic patterns. Before confirming the hydraulic head of shallow groundwater, we selected a representative observation well to assess the hydraulic head of shallow groundwater using classification with similar groundwater level change patterns, seasonality of precipitation, and the relation between hydraulic head and elevation. Results shown on a contour map from the hydraulic head distribution in the observation wells indicate a marked temporary change in June in the central part of the plain between the Tone River and the Arakawa River. The findings suggest the influence of decreased groundwater inflow from the periphery of the plain attributable to the pumping rate distribution.