The technology for reduction of fishes suffocation during winter period on example of Dnieper reservoirs

The two ways of modification the oxygen conditions of dam reservoirs in order to protect fish from suffocation at freezing periods were presented: 1) the ice-hole size enlargement, and 2) short-term rises of a water level to raise oxygen concentration in the waters in fishes wintering sites. Both the methods are based on the modifications of the water flow through hydroelectric power stations as the only management tool. The mathematical formulae for calculating water flows and its effects are presented, as well as examples of calculation for January and February for Kremenchuk Reservoir (Dnieper River).