1. Kumano Freshwater Biological Station of Hiroshima University is located below Kumano Reservoir and is supplied with cold water which exists under the thermocline in the reservoir, during the stagnation period.
2. In order to operate the station more effectively, the annual changes in the physico-chemical features of the riservoir were investigated (as shown in fig. 3-15)
3. The date of the beginning of thermal stagnation in the reservoir was from late March to early April, and that of the ending from late October to early Nobember.
4. During the midsummer period of com plate stagnation, the thermocline existed from 3 m to 5 m depth, and the surface water temperature rose to above 30oC, but that of the hypolimnion was below 20°C. The saturation degree of dissolved oxygen in the water of the hypolimnion was under 5%.
5. From September to October, considerable amounts of NH3 -N, Fe and H 2S were observed in the bottom water.