Abstract
Mt. Yakeishi-dake (1548m) is a quaternary volcano which is located in 20km of western in Mizusawa city, Iwate, and belongs in Kurikoma National Park. Mt. Yakeishi-dake circumference is known for within the prefecture as an area with many natural lakes together with the outskirts of Hachimantai. Lake Ishi-numa is one of the natural lake groups with which Mt. Yakeishi-dake is dotted, and is a closed lake without an inflow river with an altitude of 905m and an outflow river. Moreover, Lake Naka-numa is an open lake with an inflow river and an outflow river. Since Lake Ishi-numa is a closed lake, the mechanism of stable regulation of a water level has many unknown points. Moreover, Lake Naka-numa in similar environment is an open lake, and there is a difference in the self-regulation function of a water level. Then, a lake basin figure exact in this research a water level change and water temperature change were observed and it aimed at clarifying about difference with the seasonal change of water income and outgo, and water temperature and water quality and the open lake in a closed lake.
