Abstract
The formation of thermal stratification during summer in dam reservoirs suppresses the vertical mixing of their water body. When a reservoir is thermally stratified, oxygen supply from water surface to the bottom layer is limited.Since oxygen consumption in the bottom layer is intensive due to the degradation of organic matter in eutrophicated reservoirs, anoxic bottom layer is likely to be seen in such reservoirs. This anoxic condition may lead to the release of nutrients and metals from bottom sediments. Stable stratification can also be suitable for the accumulation of nuisance algae such as blue-green algae. Destratification method is thus sometimes applied in eutrophicated dam reservoirs to remedy above mentioned problems.
We have done a field experiment to see the effect of the destratification on water quality of Aono dam reservoir in Hyogo prefecture. The destratification operation was suspended for one month in summer during the experiment. We have observed the development of a significant bottom anoxia and phosphate release while the operation was suspended.With the aid of numerical simulation, we have discussed the effect of destratification on water quality in Aono dam reservoir.
