Aral Sea Basin Evolution: Geodynamic Aspect

Abstract

The Aral Sea lies in the Aral-Sarykamysh depression, which is bordered by the low plains of Central Asia. The climate is continental and extremely dry, and surface runoff is virtually zero. Since direct precipitation over the lake comprises only 10% of the water budget, lake-level fluctuations are largely determined by changes in inflow from the Amu Darya and Syr Darya rivers. These rivers originate in the highest part of the Pamir and Tien-Shan mountains 1500 km southeast of the Aral Sea. Since 1960 the lake level has been affected by irrigation activity in the basins of the Amu Darya and Syr Darya. The evolution of continental erosion and landforms is controlled by several parameters: tectonic, climatic and anthropogenic factors. The arid climate developing in the region also lead to a decrease of the Aral sea surface and an increase of desertification (Kovda,1980). The important development of the agriculture (cotton cultivation) since 50 years ago has led to a significant modification of the geomorphic system of the Aral basin: (1) the natural drainage network has been diverted for the irrigation, (2) the Aral sea surface has strongly decreased, (3) the desertification has increased. Caution is important when identifying these observations as manifestation of only antropogenic impacts, because sea level changes may be complicated by strong natural variability. For example, in the Arctic, thisKeywordsAnthropogenic FactorLower Lake LevelGeomorphic SystemGeodynamic AspectContinental ErosionThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.