Ground-water of the Naka upland, Prov. of Hitachi.

Owing to. the development of erosion of the upland lying between the Rivers Naka and Kuji in the province of Hitachi, there occurred the recession of ground-water fall line from the cliff end and the fall of ground-water table. This brought about the disappearance of water in the valley, making elongated depressions where marshes and swamps dried up. Shallow wells area left when ground-water fall line receded becomes the area of perched water.