The results of assessing the dynamics of water quality changes in artificial reservoirs after annual seasonal pumping are presented. The hydrochemical index was the criterion for evaluation, a comparative environmental assessment of the quality of the channel water was carried out by quantity of this index. It is proved that the hydroecosystem of the "Dnipro-Donbas" channel is a dynamic system that requires constant monitoring, identification, elimination of sources of pollution and conducting of hydrotechnical and melioration works. The index of the specific indicator block and the trophic-saprophytic indicator block are twice bigger than the salinity index, that means the indices of these blocks have a significant effect on the deterioration of water quality in the channel. It was established that hydrotechnical arrangements affect the level of mineralization in the reservoir: there are processes of salts migration in the water, the level of sulfates and chlorides significantly decreases. The carrying out of hydrotechnical arrangements affects the level of saprobity in the reservoirs, which leads to a significant increase of the oxygen level in water. In the channel water before pumping a high content of 90 Sr is observed, although in the organisms of fish (goldfish Carassius auratus gibelio, silver carp Hypophthalmichthys molitrix, grass carp Ctenopharyngodon idella, common carp Cyprinus carpio, eastern bream Abramis brama) the content of radionuclides (137 Cs, 90 Sr) remains within permissible levels. After pumping water, the content of radionuclides decreases by 9.7 times. Fish products in the "Dnipro-Donbas" channel are safe by radioecological indicators. Due to the dilution of water the dynamics of eutrophication processes decreases; during mixing aeration of water masses occurs, which undoubtedly positively affects the state of the ecosystem of the "Dnipro-Donbas" channel. The water quality of the "Dnipro-Donbas" channel with the average values of the indicators before pumping and after it belongs to the second class of quality and can be evaluated as "good" and "clean". The above calculations show the positive influence of hydrotechnical works on the quality of water in the channel. Hydrobiological, biochemical, microbiological indicators and indicators of biological testing require further research for effective compensatory environmental arrangements, development of recommendations on the mode of operation of the "Dnipro-Donbas" channel. To assess objectively the environmental status of the channel it is necessary to develop and implement an effective environmental monitoring system.

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