Abstract
In this study, we investigated the change in the salt concentration in a lake, and the motion of interfaces between seawater and fresh water in the ground occurred by the differences in the tidal and fresh water level, using laboratory water tank experiments. Our results showed that the interface was formed under the lake or marsh, and that the configuration of the interface was flat when the fresh water level exceeded the seawater level, while the area of freshwater became smaller than the initial area when the fresh water became lower than the tidal level. In the latter situation, the fresh water flowed into a storage pond located between the land and an embankment. The storage pond water then flowed out into the ground. This work clarified that the variations in the salt concentration in the storage pond, which reproduced the lakes and marshes, must be estimated using the entire system including the water of the lakes and marshes, seawater and the subsurface fresh water.
