At present preliminary development of the projects on construction of hydropower plants (HPPs) in the basin of the Selenga River in Mongolia is going on. Their realization can lead to essential changes in hydrological regime of the Selenga River basin in the Russian Federation, which will influence the state of regional ecosystems and economy. The international status of natural objects in Russia, which can be affected by realization of these projects, is an important factor. First of all, this concerns the Lake Baikal – the World natural heritage site. The study of the transboundary basin of the Selenga River comprises the analysis of hydrological characteristics of the Mongolian and Russian parts of the Selenga basin, the state of the art and prospects for development of water supply systems of Mongolia and the Russian Federation, the energy system including HPPs in Mongolia. The regulated runoff of the Selenga River is modeled for different possible operation conditions of projects of HPPs and hydraulic engineering structures (projects of Shuren HPP, Egiin Gol HPP, Orkhon-Gobi water transfer). Potential changes in hydrological characteristics in the Russian part of the Selenga basin are estimated with comparative analysis of the annual natural and regulated runoffs for individual seasons and areas under different conditions of water content (normal and extreme). Possible risks of the effect of potential HPPs are revealed. Their possible impact within the Russian Federation is estimated quantitatively and qualitatively. The estimates include the effect of HPPs on work of water users and consumers in the Russian part of the Selenga basin and the impact on ecosystems. The influence are estimated for separated and joined projects (cumulative influence). The ecological requirements are defined and the estimate of environmental flow on the border of the Russian Federation and Mongolia is validated.

Bychkov Igor Vyacheslavovich, Academician of RAS, Scientific Director, Irkutsk Scientific Center SB RAS, 134, Lermontov st., Irkutsk, 664033, Russian Federation, tel.: (3952) 45–30–70, Acting Rector, Irkutsk State University, 1, K. Marx st., Irkutsk, 664003, Russian Federation, tel.: (3952) 52–19–00, e-mail: bychkov@icc.ru 

Nikitin Vyacheslav Mikhailovich, Doctor of Sciences (Technics), Head of Laboratory, Melentiev Energy Systems Institute SB RAS, 130, Lermontov st., Irkutsk, 664033, Russian Federation, tel.: (3952) 52–63–07, Irkutsk Scientific Center SB RAS, 134, Lermontov st., Irkutsk, 664033, Russian Federation, tel.: (3952) 45–30–70, e-mail: nikitin1310@mail.ru 

Abasov Nikolay Viktorovich, Candidate of Sciences (Technics), Senior Research Scientist, Melentiev Energy Systems Institute SB RAS, 130, Lermontov st., Irkutsk, 664033, Russian Federation, tel.: (3952) 50–06–46 (333), e-mail: nva@isem.irk.ru 

Osipchuk Evgeny Nikolayevich, Candidate of Sciences (Technics), Research Scientist, Melentiev Energy Systems Institute SB RAS, 130, Lermontov st., Irkutsk, 664033, Russian Federation, tel.: (3952) 50–06–46 (333), e-mail: eugene.os@mail.ru 

Berezhnykh Tamara Vasilyevna, Candidate of Sciences (Geography), Senior Research Scientist, Melentiev Energy Systems Institute SB RAS, 130, Lermontov st., Irkutsk, 664033, Russian Federation, tel.: (3952) 50–06–46 (443), e-mail: berejn@isem.irk.ru 

Orlova Irina Ilinichna, Doctor of Sciences (Economics), Senior Research Scientist, Irkutsk Scientific Center SB RAS, 134, Lermontov St., Irkutsk, 664033, Russian Federation, tel.: (903) 79–55–123, e-mail: maksimova.irina.il@gmail.com 

Borisova Natalya Gennadievna, Candidate of Science (Biology), Head of Laboratory, Institute of General and Experimental Biology SB RAS, 6, Sakhyanova st., Ulan-Ude, 670047, Russian Federation, tel.: (3012) 43–32–47, e-mail: nboris@list.ru

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