Abstract
Investigation on water balance, water temperature, dissolved oxygen and other chemical analyses were made for Lake Saino-ko, Nikko, from May 1980 to April 1983.
The results are as follows :
(1) As estimated by electric prospecting of geology around the lake, the lake was dammed by coarse gravel from the river. Because of this permeable material in the downstream section, the water level of the lake shows a wide seasonal variation. The level falls by about 11m in winter compared with early summer, then the water surface area and the water volume decrease to 1/2 and 1/6, respectively, in winter.
(2) The rate of leakage from the lake is estimated from water balance in winter when noticeable inflows are not observed. A high rate of leakage is obtained at a high water level and vice versa.
(3) In summer, water balance calculated including the effect of water level has a close relationship to the effective precipitation. The equilibrium water level in summer is estimated to be 13.3m.
(4) Water circulation is effective in shallow layers as deduced from dissolved oxygen and water temperature. This may be influenced by the position of leakage. A phenomenal circulation was observed during and after floods.
