Study on groundwater salinization accompanied by the groundwater level recovery at coastal area

－Case study in Arao City, Kumamoto－

Abstract

To reveal a process of groundwater salinization in Arao City, the groundwater level, water quality and groundwater age tracers are used. Groundwater salinization has occurred by the pumping up groundwater in the coal mine below Ariake Sea, and the recovery of groundwater level after closing down the mine. Salinized groundwater consists of two components. One is fresh groundwater which has recharged during 1930 to 1940. The other is saline water, which is originated from a diluvial formation below Ariake Sea and has recharged during 1972 to 1999.