Lakes

Lakes are one of the most important geographical elements of Mongolia. Mongolia boasts more than 4000 lakes, 3500 of which have a surface area of more than O.I sq. km. An overwhelming majority (95 pel cent) are small lakes with a plane area of less than 5.0 sq. km. There are a few (5 pel cent) with a plane area of more than 5 sq. km. but their total area is large compilsing almost 90 pel cent of the total water surface of lakes (16.000 sq. km which is more than 1 pec cent of the country's territory). According to lough estimate. the total volume of lake waters is close to 500 cubic km. I.e. 13 times more than the total yearly flow of all the rivers in Mongolia. Many of the lakes are freshwater (more than SO pel cent of the total volume).
Lake Depressions Lakes with a depression of tectonic origin are numeious in the mountains and quite rare In the lowlands (Uvs. Khar Us. Hyargas. Bull and other large lakes). There are volcanic lakes in a number of mountainous regions (Terhiin-Tsagaan Nuur In Khangai is a typical volcanic lake). A large number of the high-mountain lakes in Mongolia are connected with modem and ancient glaciers (Khoton. Dayan and Khagiin Khar lakes). There are many cryogenic lakes in permafrost zones in the country's norfh. There are also lakes of aeolian origin.

The Water Regime of Lakes

The main sources of alimentation of most of the mountain lakes are seasonal snowmelt water rain and groundwater. Thaw waters of glaciers basically feed Periglacial clique and barrier lakes and snow patches while rain and unconfined groundwater generally feed lowland lakes. An overwhelming majority of lakes obtain the bulk of their waters (river flow and precipitation) during two 01 three summer months. The yearly water level fluctuation at large drainage lakes is 0.7-0.9 m. in rare instances a little higher and in smaller pools it is 2 -3 m.
Because of the continental climate lakes become extremely healed in summer and in winter they remain frozen for a long period of time. accompanied by the formation of a thick ice-sheet. Quite often they are frozen to their floor. The temperature regime of lake waters vanes sharply during the year. The waters of the lakes warm up fast in June. the highest temperature is registered in July-August, in September the temperature first starts dropping rather fast. but gradually this slows down. The change in the temperature of water from depth is much more complicated although characteristic for an overwhelming majority of lakes is the reverse temperature stratification in winter the transition through homothermy in spring. and direct temperature stratification in summer. Long and stable freezing depends directly on the severe continental climate of Mongolia. In the mountainous regions, lakes remain ice-covered for 7-8 months and in the plains from 6 to 7 months. Towards the end of winter (in March) the thickness of the ice sheet on the lakes is 1.0-1.5 m. The water purity in high mountain lakes leaches 15-25 m and in the Gobi lakes 1-3 m. Many of these lakes are used for extracting salt and for balneological purposes.
The Distribution of Lakes is unevenly distributed throughout the territory of Mongolia. Most are In regions with a relatively humid climate (especially in the mountainous regions) and in zones of insufficient humidity (steppe and semidesert regions). They are located mostly at an altitude of 1.500-2.000 m above sea level very rarely higher. Thirty pel cent of all the lakes in Mongolia are In the mountainous regions, only 0.5 pel cent of them cover an area of over 100 sq. km.

Khovsgol

The most notable mountain lake in Mongolia is Khovsgol the deepest lake not only in Mongolia. but In the whole of Central Asia. In area (2.760 sq. km) Hovsgol is the second largest lake in the country after Uvs Num.. II is 136 km long. its greatest width is 36.5 km. the depth in the middle of the lake is 262 m. and the total volume of water is 380.7 cubic km - 1 pel cent of the world's fresh water. The volume of fresh water is 10 times more than the total yearly run-off of all the rivers in Mongolia. More than 90 rivers flow into Lake Khovsgol the Egiyn Gol river flows out of it. The water of Khovsgol is extremely transparent the mean transparency of the water is 16-18 m and the highest almost 25 m. Other large mountain lakes are in the Altai and Khangai ranges.Achit Nuur
This is the largest lake in the Altai. It is situated at an altitude of 1.435 m. with a plane area of 297.0 sq. km. and is 24 km long and 18 km wide. The lake is not very deep. mostly in the region of 1-3 m. with the deepest point at just 5 m. Among the mountain lakes of Khangai and Khentii. only Telmen (194 sq. km) and Sangiin Dalai (165 sq. km) lakes have an area of more than 100 sq. km each. Seventy pel cent of all the lakes are in the plains of Mongolia. including 15 pel cent of all the lakes with individual areas of more than 1.000 sq. km. Most of the lakes here are remains of extinct large water bodies and the bulk of them are closed 01 have a temporary flow.

Uvs Nuur

This is the largest lake in Mongolia. It covers an area of 3.350 sq. km. its maximum length is 84 km. its breadth 79 km. the length of its shore line 425 km. its average depth 12 m. its greatest depth 20 m. its water capacity 40 cubic km. and its drainage area 71.100sq. km. The lake is situated at an altitude of 759 m above sea level. Uvs Nuur is a salt-water lake. The salt content is comparatively low. 11-12 pel cent. which is approximately three times smaller than the salinity of the world's oceans.

Khar Us Nuur

This lake lies at an altitude of 1.153 m. covering an area of 1.852 sq/km. with a maximum length of 72 km a width of 27 km and a depth of only 4 m. The lake area Includes the high rocky island of Ak-Bash (up to 270 m higher than the surface), which divides the Har Us Nuur lake into two unequal pans. The island is 26 km long and 19.3 km wide. covering an area of 274 sq.km.

Hyargas Nuur

This is the end base level of erosion of the lake group consisting of the Khar Us, Dorgon Nuur, Khar Nuur and Airag Nuur lakes. Hyargas Nuur is one of the largest lakes in Mongolia, with a water surface of 1.407 sq. km. The lake is 75 km long and 31 km wide. Its mean depth is 47 m. with the deepest point reaching 8O m. and its total water volume is 66.034 cubic km and drainage basin 115.500 sq. km. The only water flowing into it is Galbiyn Hooloi.

Khar Nuur

This is at an altitude of 1.132 m above sea level. its water surface area is 575-sq. km. II is a shallow water body with the greatest depth reaching only 7m.

Boontsagaan

This is in the Valley of Lakes, at an altitude of 1.312 m above sea level. The lake is 24 km long and 19 km wide. The area of its water plane is 252 sq. km and the maximum depth is 16 m. The Dorgon (305 sq. km). Airag (143 sq. km). Orog Nuur (140 sq. km) and Ulaan Nuur (175 sq. km) lakes in the Depression of the Great Lakes and the Valley of Lakes are Gobi desert lakes. Bull Nuur and Khokh Nuur are lowland steppe lakes.

Buir Nuur

This lake lies at an altitude of 581 m above sea level and comes under the Pacific basin. The area of its water plane is 615 sq. km. its length is 40 km its width 21 km. and its maximum depth 10.5 m. The state border
of Mongolia with the PRC runs along its northwestern shore.

Main Lakes Area (sq. km.)

1.Uvs 3350 7592
2.Khovsgol 2620 1645 262.4
3.Khar Us 1852 1157 4.4
4.Khiargas 1407 102S SO 5.Buir 615 581 10
6.Khar nuur 575 1132 7
7.Achit nuur 297 1435 5
8.Durgen nuur 305____1132 27
9.Boontsagaan 252 1312 16
1O.Ooreg nuur 2381425 42
11.Telmen nuur 194 1789 27
12.Tolbo nuur 84 2079 12
13.Sangijn dalai nuur 165 1888 30
14.Ayrag nuur 143 1030 10
15.Ulaan nuur 175 1008
16.0rog nuur 140 1217 5
17.Khokh nuur 94 552 14
18.Dayan nuur 67 2232 4