An artificial reservoir with a volume of more than 1 million m3, the level and water exchange of which are regulated by hydraulic structures. Reservoirs for the accumulation and subsequent use of water for domestic purposes. There are river reservoirs, lake reservoirs and lake-river reservoirs.

A reservoir (French: réservoir) is a hermetically sealed or open, stationary container filled with a liquid substance. It comes from the word "reserve" (French: réserve, from the Latin reservare - to save, preserve).

Man-made. There are two main ways of their construction: filling with water artificially created tanks outside natural reservoirs (most of sports pools, excavations, some reservoirs); dams on rivers (most of reservoirs and ponds). Most of the water in artificial reservoirs is concentrated in reservoirs - artificial reservoirs with a volume of more than 1 million m3 of water. They may also include dammed lakes. Like other artificial reservoirs, reservoirs are created for the purpose of water storage and subsequent use, for flood control, because the natural water regime, which is very uneven from year to year and throughout the year, usually does not meet the requirements of various economic demands on water resources.

Reservoirs are characterised by: increasing depth towards the dam (except for some that contain lakes), very slow water exchange and flow velocity compared to the river, as well as a number of other hydrological features. There are reservoirs with daily, weekly, seasonal and long-term flow regulation, redistributing the natural flow within a day, within a week, between individual seasons and years.