Change of groundwater environment and problems in large urban areas in Japan

Urbanization affects quantitatively and qualitatively groundwater environment in urban area. Especially, groundwater environment in large urban area has been changed more than several decades. However, there are few studies about evaluation of secular change of groundwater environment with developing of urban area. In this study, long term change of groundwater environment in the Kanto plain and the Nobi plain which had the very large urban areas were summarized from the view point of regional groundwater flow.Present groundwater flows in these plains were significantly different from the groundwater flows in the periods when the effects of urbanization were small, even though more than 30 years have passed since groundwater extraction had been regulated. Also, three dimensional distributions of chemical properties of groundwater quality and environmental isotopes have changed. These results show that the effects of human activities were still strongly remained. On the other hand, demands for groundwater for public use and private use have become increasing in recent years because of recovery of hydraulic potentials of confined aquifers that had depleted from the 1950s to 1970s by huge amount of groundwater abstraction. Therefore, it is important to keep monitoring and evaluating the groundwater environment in these urban areas for sustainable management of groundwater resources.