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Hydrochemical regime of the Aydar-Arnasay lakes

CEU eTD Collection
Generally speaking, it is known that there is a strong connection between water and hydrochemical regimes of drainless lakes located in arid zones and it can be clearly observed on the example of Aydar-Arnasay lakes. The features of the water regime of these lakes basically are explained by the annual fluctuations of mineralization (Nurbaev and Gorelkin 2004). Summer-autumn increase of mineralization and its winter-spring decrease is recorded in lakes Tuzkan and Aydarkul. The significant increase of mineralization during the summer period is due to intensive evaporation, i.e. annual evaporation losses amount to 15-20% of total volume of water in lakes. This fact considerably influences the formation of their hydrochemical regime and patterns of mineralization distribution through the lake’s profile. Intensive evaporation promotes the regular increase of salt concentration in the surface layers of the lakes. The decrease of mineralization in Aydarkul and Tuzkan lakes during winter- spring time is primarily caused by increase of precipitation and decrease of mineralization of collector-drainage water (Chembarisov and Shamsiev 2007).
In the 1980s some investigations of the hydrochemical regime of these lakes have been accomplished. Mahmudova specifies that depending on the proportion of the balance’s components, a distinct hydrochemical regime forms in different parts of the AALS (Mahmudova 2004a). Moreover, Ivanov and Nikitin in their book “Hydrometeorology of lakes and reservoirs in Central Asia” consider shallow zone of the Aydar-Arnasay lakes system which is distinguished by a particular hydrochemical regime. They describe that a huge number of shallow bays and small lakes formed around the whole Aydar-Arnasay system make the regime very heterogeneous. Taking into account the constant reduction of water level resulted from substantial evaporation, the majority of shallow bays of the coastal lake zone turn into separate tiny lakes, and subsequently into solonchaks (Ivanov and Nikitin 1978).
Summarizing, it should be outlined that a gradual increase of mineralization is observed in all Aydar-Arnasay lakes except East Arnasay lakes. This increase is caused by all types of salt inflow. Moreover, sharp reduction of water volume resulted from evaporation losses is also observed. Aydarkul and Tuzkan lakes are characterized by the most intensive increase of mineralization in recent years. The water regime and distribution of mineralization in the East-Arnasay lakes differ from the regimes of Aydarkul and Tuzkan. The principal distinction consists in the features of collector-drainage inflow. Increase of water inflow, which relates to entering of less mineralized water to the lakes, brings about the general decrease of mineralization with minimal amounts of salt concentration in the area of the Chardara water discharges (Nurbaev and Gorelkin 2004).

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