An assessment of environmental flow for modelling the operating conditions of Mongolian hydropower plants in the transboundary basin of the Selenga River

The decision of Mongolia’s Government to implement the projects for the construction of hydropower plants (HPPs) in the transboundary basin of the Selenga River caused the need to study their possible impact on the Russian part of the basin and Lake Baikal. To assess the impact of planned in Mongolia HPPs on the territory of the Russian Federation (water resources and ecosystem), we have studied the expected changes in the yearly hydrological regimes due to flow regulation. A methodology developed at the Melentiev Energy Systems Institute (MESI) allows integrating various models (hydrological, energy, environmental, etc.) into a single system. We have employed this system to model the parameters of the planned HPPs reservoirs and their regulation modes, as well as the deviations of hydrological regimes of Selenga River due to the HPPs construction from those under natural conditions. The concept of “environmental flow” is used to assess changes in the intra-annual hydrological regime of a river. We determine the boundaries of the environmental flow for each month based on an analysis of a variety of biotic and abiotic restrictions for the entire river bed from the border of the Russian Federation to the Selenga River delta.