The main purpose of the Sengileevsky reservoir is currently the flow part accumulation of the Nevinnomyssky canal for municipal and industrial water supply of the city of Stavropol, the city of Mikhailovsk, Shpakovsky and Grachevsky districts, the irrigation of the river Egorlyk and the water supply regulation in the Rostov region and the Republic of Kalmykia, provision of water to the Right-Egorlyk Canal, Mezhdurechenskaya Environmental Protection Agency and incidentally, Egorlykskaya and Novotroitskaya Hydroelectric Power Station, Stavropol CPP. From the Sengileev reservoir water is supplied to the city of Stavropol and several other districts of the region, with more than 1 million people being provided with water. Water intake structures with a pumping station on the Sengileev reservoir are unique and have no analogues in Russia. Water is taken by pumps from a depth of 10 meters and then supplied by three pumping stations to a height of about 500 meters. The water quality in the reservoir in different years mainly corresponds to classes II – III, “pure” or “moderately polluted” with a WPI close to 1, whereas in the tributaries for a number of sections the water quality may decline in certain periods to V-VI as “Dirty” and “extremely dirty”. The main idea of the work is to use an environmentally safe technology to combat drainage, pre-purification of water in front of the sewage treatment plant and ensuring uninterrupted water supply in settlements at any time of the year.

The main design flaws in terms of protection against young fish entering the water intake bucket, sediment inflows, sludge and floating objects, which largely do not provide the current regulatory environmental requirements for ensuring environmental safety (ES) of water intake technological complexes (WITC) directly interacting with the natural water environment (WE) of the water body (MPWS) as a part of the natural technical system (NTS) “WE-WITC-MPWS” were identified during the comprehensive studies to assess the functional effectiveness of existing water intake structures (about 44) of multi-purpose water supply systems (“MPWS.”) of urban farms and settlements in the Lower course of the river Don from the Tsimlyansky reservoir to the mouth (Azov). In order to ensure the operating “WITC” operating systems based on the results of constructive studies using domestic experience in the use of high-strength synthetic fabric materials, an innovative design of a water intake structure in the form of a soft floating structure (SFS) has been developed providing the regulatory requirements on the main indicators of ES by 85%-95%.

The article represents the results of integrated studies of development of protective measures providing environmental safety in areas affected by water-intake technological complexes as a technological component of specified type of natural-technical systems (NTS) ‘natural aqueous medium – water intake technological complex – multiple-use water supply system’ (NAS-WITC-MUSS) concerned with a stable residential water supply of urban households.

In the development of a specialized type of natural and technical systems (PTS) "Natural water environ-ment-water Intake technological complex-multi - purpose water supply System" ("P. V. S. - V. T. K.-S. M. V.") of urban households and economic objects on the basis of the results of long-term studies of the existing "V. T. K." in the Lower reaches of the Don river, the methodological basis for assessing the zones of their influ-ence in the considered spatial limits of the basin geosystem has been developed. On the basis of the formulat-ed principles of ecological acceptability of the used constructive and technological solutions on the basis of "V. T. K." quantitative and qualitative criteria environmental indicators of environmental safety, which are manifested in the established boundaries of the zones of influence in the considered region of the basin ge-osystem, have been developed. The main quantitative criteria are: preservation of the diversity of fauna and flora in the water body as a water source, protection of the water treatment system "S. M. V." from blue-green algae and river dreysen . The results of the research are implemented in the Alexander "V. T. K." urban farms of Rostov-on-don, Aksai and Bataysk .

Basing on the results of long-term research of currently functioning and constructing of waterworks known as ‘activity objects’ (‘AO’) as parts of natural-technical systems (NTS) ‘natural medium – activity object – population’ (‘NM-AO-P’) limited by basin geosystems of Kuban, Lower Don and Terek rivers, in this article are presented the methodological basics of evaluation of level of environmental safety affected by functioning ‘AO’, forming in their impact areas space-time environmental state of NM (surface stratum of the atmosphere, waterbodies of hydrographic river system limited by the water-taking territory where the surface water discharge is formed; higher layers of the lithosphere where the underground water discharge is formed; soil surface with underlying layer),what influences all the processes of life activity of biota, fauna and health of local population.