Abstract
An investigation of the phenomena of sea water intrusion into ground water in the basin of the River Kiki and Miyauchi, Ehime prefecture, arecarried out by examining the contents of chloride ion in ground water. The influence of sea water intrusion is observed remarkably in the region within about 700m from the seashore. The relation between the phenomena of sea water intrusion or drawdown of water level and the pumping amount of ground water is also discussed.