Numanodai district near Hijiori Spa is characterized by abundance of small lakelets formed by landslide. Lake Onuma and Lake Naganuma among them are presented in this paper.
1. The morphometrical data calculated from the bathymetric maps in text are summarized in the following table.
2. From the hydrological point of view, the lakes are fed by melt water to a great extent. The airbone salt in snow deposit which covers the basin determines the quality of lake water. Therefore, the main solute in lake water is sodium choloride. The lakes are poor in nutrients such as phosphate and nitrogen compounds.
3. In midsummer, the thermal and chemical stratifications develop distinctly in the lakes. The seasonal investigation of Lake Onuma indicates that water temperature keeps constant through the year in the hypolimnion below the depth of 13m. In other words, this lake belongs to meromictic lake.