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Mongolian River and freshwater reserve

A vast territory bordering 2 big countries, Mongolia shares water resources with some of them such as Russia and China. Mongolia is located on the divide of three continental basins. The Northern Arctic Ocean Basin, the Pacific Ocean Basin, and the Central Asian Internal Basin. The Northern Arctic Ocean Basin drains about 50% of the total river runoff of Mongolia, while the Pacific Ocean Basin drains about 10% and the Central Asian Internal Basin about 40%. These three continental basins are further divided into 29 river basins. The yearly renewable water availability is highest in the Northern Arctic Ocean Basin at 53,100 m3 per km2, as compared with 19,200 m3 per km2 in the Pacific Ocean Basin and 13,000 m3 per km2 in the Central Asian Internal Basin. However, since the population is also concentrated in the Northern Arctic Ocean Basin, the annual renewable water availability per capita is lowest in that basin at 8,800 m3 per capita, as compared with the Pacific Ocean Basin’s 19,000 m3 per capita and the Central Asian Internal Basin’s 16,500 m3 per capita. Draining to the north is the Northern Arctic Ocean Basin, which feeds the rivers of the Russian Federation that debouch into the Arctic Ocean. The main river is the Selenge River, which contributes to the large Baikal Lake in the Russian Federation. Important tributaries are the Orkhon and the Tuul Rivers. The Tuul River is a tributary of the Orkhon River, while the Orkhon River joins the Selenge River just before the border with the Russian Federation. About 65% of the Mongolian population lives in the Northern Arctic Ocean Basin, where the majority of the country’s socioeconomic activities occur. The Pacific Ocean Basin drains to the east, forming the headwaters of the Amur River. This river runs along the border between the Russian Federation and Manchuria in the People’s Republic of China (PRC) before debouching into the Pacific Ocean. The main river is the Onon River, which rises in the Khentii Mountain Range in northeastern Mongolia.

The Central Asian Internal Basin, which is the largest of the three continental basins, contains rivers that supply water to the aimags in the water-scarce, semi-desert area. Rivers located in the western aimags flow into the internally drained Great Lakes Depression. The river runoff is crucial for the sustenance of these lakes, of which several are ecologically important. River discharges vary significantly from year to year and fluctuate throughout the year. Snow and ice melts are the main sources of flow during spring. The largest flow is generated by rainfall in July and August. After September, the flows decrease substantially and, in November, the water starts to freeze and the flow stops until the spring melt. Year-to-year variability is large, and important rivers such as the Tuul and the Orkhon rivers show extended periods (from 5 years to more than 10 years) of above or below long-term (i.e., more than 20 years) average flows. Because of the variability of river flows and since rivers freeze in winter, groundwater is tapped as Mongolia’s main water source (99%) for drinking and industrial water. Livestock also relies on groundwater from wells in areas away from rivers. Likewise, a majority of the country’s mines use groundwater. For irrigation, surface water is primarily used, but the use of groundwater is also increasing. A decline in groundwater levels has been observed, most likely caused by increased groundwater use. But a lack of good data on the groundwater resources and their quality makes conclusions on long-term trends and causes difficult. As these resources are economically and socially important, data collection should be improved. Climate studies reveal that the average annual temperature has increased considerably (by about 2.2°C) since the late 1950s. In these climate studies, no long-term trend in precipitation change was detected and the observed variability of river flows seems unrelated to climate change, possibly because an observed drying climate trend is now being reversed by melting glaciers and a projected increase in precipitation. Still, the increase in temperature will impact the permafrost, increase evaporation and evapotranspiration, and influence the hydrology. Trends in river flows cannot be accurately confirmed. However, a 2015 study showed indications of a reduction in lake areas on the Mongolian Plateau from the late 1980s to 2010.12 The study suggested that Mongolia’s precipitation was the primary driver of lake changes, but it also noted that the rate of loss in lake areas was greater in the PRC’s Inner Mongolia Autonomous Region, where coal mining and irrigation were important factors. The study concluded that the observed decline of lake areas is likely to continue as a result of climate change and the increasing exploitation of underground mineral and groundwater resources on the Mongolian Plateau. Although ground-based measurements of groundwater resources in Mongolia are insufficient to assess trends, the use of satellite measurement of changes in terrestrial water storage (TWS) indicates some remarkable temporal and regional variations. In the Altai Mountains, the Great Lakes Depression (also known as the Great Lakes Hollow), and the northern region of the PRC, a continuous decrease in TWS can be found, which can be attributed to glacier retreat, thereby lowering the water levels of lakes and groundwater. TWS has been continuously decreasing in central Mongolia, most notably in Ulaanbaatar. In the southeast, TWS has been fairly constant. Most river water is suitable for any use, but water pollution has become a major local issue. The rivers are heavily polluted by domestic, livestock-related, and industrial wastewater discharges. Water pollution is mainly a problem downstream of urban areas, such as in Ulaanbaatar and in Aimag and soum centers. Overview of Mongolia’s Water Resources System and Management are limited and often in poor condition. Mining activities also cause pollution of heavy metals, especially from small mining operations. Surface water forms an important habitat for many bird species in the sometimes harsh (dry, cold) conditions in Mongolia. Lakes and wetlands are vital breeding grounds for seasonal birds. Hence, the environmental flow requirements in Mongolia are set high at 90%–95% of the long-term average flows. Environmental flow, which comprises the amount of water (e.g., within river basins, lakes, or wetlands) allotted to sustain ecosystem functioning and human livelihoods, is an essential element of integrated water resources management (IWRM).

source: Water Resources and its Utilization Department, Institution of Geology Mongolian Academy of Sciences

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