Abstract
The purpose of this study is to make an improvement plan of water hazards caused by AOSHIO, the ascending of the anoxic water from the bottom to the surface, at the Lake Abashiri in Hokkaidou.The field observation shows the following results;
1) The lake is vertically divided into two layers, the lower layer with salt waters and the upper with fresh waters.
2) The interface between two layers shows the regular oscillation of internal waves on gentle wind.
3) The interface shows the uniform decline toward the wind direction on strong wind.
