Natural lakes in Hokkaido

点击翻译按钮获取中文摘要

This study was carried out for the purpose of making clear the hydrogical and hydraulic properties of Lake abashiri which located in northeast of Hokkaido Island in Japan, and suggesting purification method of the lake. From the field observations in 1993. We concluded that ecological system and environment of the lake have been influenced by two-layr structure of fresh and salt water and eutrophication in the lake. Based on these results and numerical analysis, we predicted the long-term behavior of the salinecline, and investigated behaviors of jet induced by river flow into the lake in 1994. We found that the salinecline gradually has been rising, closely linked with decreasing of annual precipitation in the Abashiri Basin in these 60 years. It is necessary to consider coriolis force in small sized lake like Lake Abashiri. In 1995, we made clear the relationships between two-layr structures and flow of the lake, and suggested methods for freshwater in the lake. We found that the flow around center of the lake formed four-layr structure in vertical direction, influenced by dense layr structure, wind, formation, coriolis force and river. Aoshio occured with the strong wind which blows for a long time. In order to control Aoshio, it is effective descending the boundary surface between fresh and salt water. We confirmed that it is necessary to induce artificial method for fresh water.