Degradation of glaciers

Degradation of glaciers

Climate change has a negative effect on the glaciation area in mountain ecosystems, but the speed and nature of such effect is different in the different from one to another mountain region across the world. Such an effect constitutes a particular danger in the Central Asian region situated at the centre of the continent, in the arid zone, away from humid oceanic atmospheric flows.

Climate change in Central Asia first manifests itself in the form of decrease in precipitation in summer and melting of glaciers that represent essential components of feeding of Central Asian rivers.

Depending on the elevation of catchment area, degree and period of its moistening by rainfall, the share of particular sources in feeding rivers varies considerably; consequently, the regime of runoff changes to some extent. For example, the Kyrgyzstan mountain rivers belong to the Tien Shan type with two pronounced phases: spring & summer snowmelt flood (high water) and autumn & winter low water; at that, two peaks are observed during snowmelt flood – spring peak (April-June) related to the period of snowmelt in mountains and summer peak (July-September) caused by melting of glaciers and snow patches in high mountain regions.

The main catchment part of the biggest rivers of the region, Amudarya and Syrdarya, is located in mountain and high mountain area. They are chiefly fed by the melt waters of seasonal snow cover; lesser proportion is represented by the glacial and rain waters.

The rivers of the Balhash lake basin (Ili, Aksu, Lepsy, the Ayaguz) also originate in mountains, i.e. on the glaciers of Northern and Eastern Tien Shan as well as of Djungarskoe Alatau. They are typically nourished mainly due to melting glaciers (except for the Lepsy river for which snow and glacial nourishment is typical).

One more Central Asian river having its origin in Tien Shan (Central part) is the Chu river that flows through Kyrgyzstan and Kazakhstan. The glacial-snow feeding is also typical of it.

The major flow (80%) of the Amudarya river is formed at the Pamir-Alay mountains in the territory of Tajikistan, and some part in Northern Afghanistan. The Amudarya river formed by the confluence of the Pyandj and Vahsh rivers unites the basins of the Surkhandarya, Sherabad, Kashkadarya, and the Zarafshan rivers. The basins of the Sherabad and Kashkadarya rivers are located in the territory of Uzbekistan.

The most part of Syrdarya water resources are formed in Kyrgyzstan (Naryn River – over 74%); Uzbekistan contributes approximately 14% (Karadarya River); Tajikistan accounts for about 3%; and 9% is contributed by Kazakhstan (Arys and Keles rivers).

In total, there are more than 8000 glaciers in the Tien Shan area. The glaciation area is 7300 km². The freshwater reserves preserved in mountain glaciers are estimated at 650 bln m³. During the period of 1960-2005 about 100 glaciers disappeared in the Zailiyskiy Alatau (a mountain range in the north-west part of Tien Shan); the glaciation zone of the Western Tien Shan (the Pskem range) decreased by 16.8% for 20 years.

Over 10000 glaciers are found on the Pamir-Alay range on an area of 9820 km². From 1957 to 2000, that is only within a 43-year period, the water reserves of the Pamir-Alay glaciers decreased by over 25% (according to other sources, more than 1000 glaciers disappeared during the period of 1960–2005 in the Pamir-Alay territory). And these processes are going on. If breaking down the data by countries it becomes obvious that the glaciers in Tajikistan decreased by 20-30% in the 20th century; the glaciers in Afghanistan (left bank of the Pyandj river) decreased by 50-70%; the area of glaciers in Kyrgyzstan by the year of 2000 had decreased by 14.9% as compared to the 1960s. In total, during the period of 1957–1980, the glaciers of the Aral Sea basin lost 115.5 km³ of ice (this comes to about 104 km³ of water), which consists almost 20% of the ice reserves in 1957. The main cause of the glaciers destruction (deglaciation) is global warming which is intensified by natural phenomena (pollution of glaciers by dust carried by dust storms from Afghanistan, Iran, China, and deserts of Central Asia), and anthropogenic activity (carry-over of salts and dust from the drained Aral Sea bed: over 1 million ton of salt and sand containing remains of fertilizers from are annually carried out from the dry bed of the Aral Sea to an area of 400,000 km²). Deposition of natural and anthropogenic aerosols on the glaciers and snow covers entails the change of snow and ice reflectance, increases the amount of absorbed solar energy, and accelerates melting process.

According to UNEP, within recent decades the surface air temperature has risen approximately by 0.6° С, and by 1.6° С in mountain regions. Though, the temperature data for the Central Asian region differ from the worldwide tendency: the highest rate of warming was registered in plain regions, whereas in mountain regions even fall of temperature were registered in some cases. Nevertheless, the fact of systematic increase of average annual surface air temperature is not disputed. Further air temperature increase will accelerate the glacier melting process which in aggregate with decrease in precipitation and increase in water consumption will aggravate the strained situation in the region on a mid-term and long-term horizon. The runoff volume in summer season (July-September) will reduce as the water reserves in glaciers decrease. Considering the existing tendency of glaciation degradation glaciologists have forecasted that the glaciers will completely disappear by the end of the 21st century. As was predicted by Tajikistan specialists, thousands of small glaciers would disappear by 2025, the glacial area would decrease by 20%, and ice reserves would reduce by 25%. As a result, the cumulative runoff of the rivers flowing through the territory of Tajikistan (Zarafshan, Kafirnigan, Vakhsh, and Pyandj) will reduce by 7%. Under the influence of climate change the river runoff volume in the Amudarya river basin will reduce by 10-15% and in the Syrdarya river basin by 6-10% by 2050. Although according to short-range forecasts, rivers’ water content will increase due to intense melting of glaciers, which in particular will cause intensification of floods and mudflows.

Unequal distribution of water resources is keenly sensed in the light of their rising scarcity, and subsequently intergovernmental confrontation will become more severe. It is natural that in relation this issue the “line of battle” lies between upstream water-abundant countries and downstream water-stressed countries, or put it otherwise, between hydropower generating countries and countries with irrigated agriculture.

Nevertheless, in spite of all negative forecasts the average annual cumulative river flow in Kyrgyzstan has increased from 48.9 km³ in the period until 1973 up to 51.9 km³ for the period of 1973-2000. In addition, in the territory of Uzbekistan as well as in Kazakhstan no consistent trends indicative of already observed shrinkage of water reserves are revealed. Furthermore, the runoff volume of the rivers of the Balkhash Lake basin in Kazakhstan has increased by 8% in the second half of the 20th century and beginning of the 21st century. The runoff volume increase is mainly caused by degradation of mountain glaciers and inflow of additional volume of melt water. For over 50 years of observations, no considerable transformation of year-to-year and within-year variability of the runoff volume of the main rivers in the Amudarya basin is revealed.

Source: Borisova, E.A. Aspects of the water crisis in Central Asia // “History and Modern Times” journal, Issue # 1 (15)/2012