Ecosystem condition and water quality control at impounded sections of rivers by the regulated hydrological regime

Hydrological regime at impounded sections of rivers is regulated by releases from upstream hydroelectric power stations (HEPS). Therefore regulated hydrological regimes can be used to manage ecosystem condition and waterquality control. The hydraulic regime determines the functioning of main channel ecosystems; the daily level fluctuations caused by the peak operational regime of HEPS provide the well-being of the connected network (side-arms, flood-plain lakes, ox-bows etc.) and its effect on the water quality in the main channel. The dissolved oxygen concentration and biochemical oxygen demand are the integrated indices of ecosystem condition and water quality. The reason is that these indices reflect structure and functioning of water ecosystems as a whole, particularly the dependence of organic matter production and decomposition biological processes (self-contamination and self-purification) on hydrological parameters as abiotic components of ecosystems. The models describing dissolved oxygen dynamics and organic matter (by BOD t o t ) concentration at impounded sections of rivers in dependence on water regime parameters are developed. This controlling method is aplied at the impounded sections of Dnieper-River.