The Forms of Phreatic Level Fluctuations in the Littoral Low-land of Japan.

The forms on the fluctuations of the water levels may be divided into two main types; The spontanious and artificial generations.The main fluctuation of the former is a periodic type which is high in summer and low in winter in consequence of recharge of ground-water and tide, and the rests are affected by air-pressure, earthquake and etc. According to the condition of under-ground environment (permeability of an aquifer, the capacity of the reserve, the amount of well-pumping), the latter may be divided, once more, into two types that; One is the phenomena seen in summer, that shows a drop of the water level which seems to be caused mainly by industrial well-pumping and so on, while thd other shows fluctuations in consequence of sine period.