In this paper the writer studied the annual temperature change of impounded water at the Miura reservoir, Nagano prefecture, for purpose of power generation.
Though the change of impounded water in a natural lake had been precisely studied by late Dr. S. Yoshimura, the change ofimpounded water at an artificial reservoir has not been clear. So, he first intended to study a correspondence about an annual temperature change of water between a natural lake and an artificial reservoir.
The limnological appreciation is thought to be as follows. Al though a reservoir gives rise to a larger fluctuation of a water surface, its annual change of impounded water shows a considerable correspondence with that of a natural lake. That is to say, in summer the temperature gradient toward the bottom becomes a direct stratification and in winter it turns to a inverse stratification.
The obvious difference in comparison with a case of a natural lake is found out by a thin or lacking of a epilimnion, whai chscuorvofeafrc se water and shows a higher temperature, and temperature of deep part of reservoir is always higher than 40C in summer. The another difference is the fact in winter that cold water showing about 1.2deg;C goes down to a deep part.
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