In the Metropolitan area, it has been pointed out that the rise of the groundwater level after the pumping restraint measured against the land subsidence has an adverse affect on many subsurface infrastructures. In order to solve those problems, it is considered to be essential to clarify the groundwater recharge and/or discharge system in the Kanto Groundwater Basin. In this context, we evaluated budget of the hydrologic cycle in the Tama River Basin and it’s neighboring several small river basins locating at the Southwestern Kanto Plain. In the study, we utilized the spatial analysis capability of GIS to handle the large amount of the hydrological data. As a result, it was confirmed that considerable amount of groundwater is flowing out continuously from the Tama River Basin to the neighboring several small river basins and/or subsurface aquifers. In this paper, we will demonstrate that the water budget study is sufficiently effective to bring out the groundwater flow system over a large area such as the whole Kanto Plain.
