Estimation of water runoff perennial change of the Upper Irtysh River for water resource stability
The condition of the natural environment and water supply in the basin of the Irtysh River affects the state and economic interests of three neighbouring countries - China, the Republic of Kazakhstan and the Russian Federation, which have their own interests in using its runoff. On the territory of the Republic of Kazakhstan the flow of the Irtysh is regulated by the Upper Irtysh cascade of water reservoirs: the Bukhtarma Reservoir (filled and started in 1960-1966); the Ust-Kamenogorsk Reservoir (filled in 1952-1954, started in full capacity in 1966), the Shulbinsky Reservoir (the construction began in 1976, started in 1987-1994). The reservoirs consistently carry out long-term, weekly, seasonal flow regulation and in accordance with their function change the hydrological regime of the Irtysh from their filling and start of operation. The Irtysh-Karaganda Canal constructed in 1968-1975 withdraws some water from the Irtysh for Karaganda and Akmola Regions, as well as for the capital of the Republic of Kazakhstan, Astana. Modification of the hydrological regime of the Irtysh River as a result of its flow regulation by the existing cascade of hydroelectric power stations, high water consumption and development of the flood lands led to a reduction in the natural capacity of the ecosystem of the river and its floodplain arrays with significant changes in the qualitative and quantitative indicators of the river flow. At the present stage the water balance in the North-Eastern region of Kazakhstan is considered to be tense. In this work changes in the water flow of the Black Irtysh and the Irtysh within the Republic of Kazakhstan for the period of 1903-2010 are studied. The assessment of its current state in the conditions of intensification of water use and modern climatic changes is made. Results of natural and anthropogenic changes estimation are given for the average annual and monthly runoff of the Black Irtysh and the Irtysh within the Republic of Kazakhstan during 1903-2010. It is shown that the regulation of water runoff by the Upper Irtysh water reservoirs, as well as water withdrawal in the headstream on the territory of China, led to an essential change in the general water content and hydrological mode of the Upper Irtysh: reduction of the average long-term discharge of water in the cross section of the Black Irtysh and Buran village was 19% (1973-2010) in comparison with the annual runoff for the previous period of observation (1938-1972); reduction of the average annual runoff in the modern period (1992-2010) in the cross section at Semiyarskoye village was 7 % in comparison with the natural mode; withdrawal of part of the runoff from the Irtysh River by the Irtysh-Karaganda Canal reduced the average long-term runoff by 10 % in the cross section of the Irtysh River and Cherlak village (1975-2010) located in Omsk Region at the border with the Republic of Kazakhstan; the most considerable changes happened in the monthly distribution of the runoff.