Abstract
In order to elucidate the hydraulic behaviors of flash flood-inflow and sweeping out of salt water into or from lake Abashiri, we have been carrying out synthetic field observation more than thirty times and numerical simulation since 1992. Through the field work, we found that the elevation of the boundary between the fresh water of the upper layer and the salt water of the lower one is influenced by inflow and sweeping out of the salt water caused by flash floods. Further, Aoshio, which is the appearance of salt water in the lower layer without dissolved oxygen in the surface of the lake in strong wind, affects the elevation of the boundary and water quality in the upper layer. Remodeling a ultra-sonic fish-finder, we could visualize the shaded patterns of the inflow caused by snow-melt flood and sweeping out of lake-water. Through visualizing the flow patterns in the lake, we found that there are two types of outflow from the lake. One is sweeping out of the lower water by the faster upper layer and the other is entrainment mechanism of the lower water by diffusion.
