The writers have taken place the survey of the underflow water of the major rivers in the Nishi-Tsugaru District, Aomori Prefecture since 1965 to 1968.
In the survey the writers discovered some interesting problems on the underflow iwater of piestic character, summarized as follows.
Among the underflow waters, there is a kind of large piestic character one in the neibourhood of the mouth of a river. The character of the underflow water is presumed to be attributed to the height difference between the recharging zone and the discharging zone near the mouth of the river and damming action by marine water at the discharging zone. And the piestic water itself may be recharged from the storage within the basement rocks.
There remains another river of this kind among comparatively large ones in the area, whose piestic underflow water undeveloped. This kind of piestic underflow water stratum is pressurised to be formed in the valley by a certain tectonic movement at the last stage of the Quaternary. And, for the decision of the case, for instance, the topographic abnomity as like as the lack of the terrace plain will give a kind of the key.