The article examines the environmental consequences of the construction and operation of reservoirs – the responses of aquatic and terrestrial ecosystems and their components to changes in the water regime. Such reactions depend on the surrounding landscape and are zonally specific. They are especially pronounced in the steppe zone. The authors systematized the consequences, natural and anthropogenic factors determining their evolution, measures to minimize negative environmental consequences that can be traced from the upper reaches of the reservoir to the reservoir – receiver of the river flow, where it is built. In particular, the decrease in bioproductivity and biodiversity caused the problem of reservoir drainage. As a result of lengthy discussions, an opinion has been formed that the descent of small reservoirs, which have lost their importance, as well as orphan ones, is currently environmentally justified. At the same time, it is necessary to carry out special hydro-reclamation and phytomeliorative measures aimed at stabilizing the hydrological and ecological situation.