Study on the Groundwater Flow along the Seawater / Freshwater Interface

The shape of Seawater / Freshwater Interface is effected by the groundwater flow at the coastal area, and decide the position of submarine groundwater discharge that should be existed everywhere in the world. The hydraulic gradient is too small to estimate the groundwater flow in the area, usually. On the other hand, the groundwater that discharges to the marine have to runs along this interface. And the water discharged to the marine is from the deep zone. That_fs why the water discharges to the marine (runs on the interface) might have many information of the deep zone of groundwater. The Hasunuma Beach Park located on the Kujyukuri Long Beach close to the New Tokyo Int_fl Airport is selected of the study for the groundwater flow along the Seawater / Freshwater Interface. The layered aquifer in the deposited rocks lies in the area, until over than 1000 m depth. The shape of the interface was observed by some kinds of physical sounding from the surface (e.g. specific electricity, AMT method), the logging data in the observation well (EC, T, Flow meter logging, Electric logging etc.) and water quality analysis (incl. Isotopes). And the Flow Meter measurement in the well was done, so that the actual groundwater flow was measured in the aquifer (in the crack of the aquifer, exactly). The observed groundwater flow is thought on the interface and the important element of the shape (angle and depth) of the interface, simultaneously. Two interfaces are found at the well point (200 m onshore). The shape of the interface was also confirmed from a diving work that found the submarine discharge of fresh groundwater at 320 m offshore. The distribution of pressure (hydraulic gradient) in the aquifer and the shape of the interface are made cleared by these tests. The progress expression of the Glover_fs solution was suggested by the study.