The influence of dam construction on the Uldza river in Mongolia on the hydrological regime of the Torey Lakes
V.M. NIKITIN, N.V. ABASOV, E.N. OSIPCHUK
L.A. Melentiev Energy Systems Institute, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia
Keywords: reservoir, modeling, transboundary basin, flow change, long-term flow regulation, water balance
Abstract
This paper addresses the possible consequences of the construction of the Uldza river reservoir in Mongolia which are associated with a change in the hydrological regime of the Torey Lakes and the transboundary basin. Based on data of hydrological observations from 1965-2020, the features of the climatic and hydrological characteristics of the Uldza river and the Torey Lakes are analyzed. It is noted that that the main factor for variability in their hydrological regimes is the cyclic behavior of climate change accompanied by a large amplitude of temperature fluctuations, an extremely uneven distribution of precipitation over seasons and individual years, high water filtration and evaporation losses (often exceeding the local runoff), and periodic drying up of rivers and lakes. Available material of the tender documentation for the Mongolian Onon-Ulz project, open raster data of satellite sounding of the Earth and various GIS sources, and other global data were used to simulate the configuration of the projected reservoir, and its filling and drawdown modes under different water conditions. Based on the simulation results, the quantitative estimates of the possible average monthly deviations of the regulated runoff, levels and area of the water surface of Lake Barun-Torey from the natural conditions were obtained. Calculations of the operating conditions of the designed reservoir show that it can only be filled when the flow rate is 50 % or lower. Thus it will remain unfilled for a long time, which casts some doubt upon the economic expediency of its creation. Despite the low absolute values of the runoff, its relative deviations from the natural conditions vary widely (from 3 to 192 %). The most substantial influence of the reservoir on the deviation of runoff indices, levels, and area of the lakes compared to natural conditions occurs in dry periods. Thus the reservoir creation can lead to a significant change in the natural hydrological conditions of the Uldza river and Torey Lakes and negative consequences for the ecosystem.
|
