Известия Томского политехнического университета: Инжиниринг георесурсов (Apr 2018)
Anthropogenic transformations of water resources and maximum water levelsof the Irtysh river in the lowland part of the basin in the Republic of Kazakhstan
Abstract
Relevance of the study. The paper introduces the results of analysis of characteristic features of the maximum annual water levels regime of the Irtysh River in the transit section downstream of the Upper Irtysh cascade of reservoirs under natural and regulated conditions. Maximum levels determine the situation with floods, destructive effects of river flow on objects in the river bed and floodplain, watering of floodplain massifs. The latter now seems to be an important problem for Pavlodar region of the Republic of Kazakhstan, as the productivity of vast floodplain pastures along the Irtysh depends to a large extent on the post-spring water supply in the soils and their washing. Reducing the frequency, duration and depth of flooding of the Irtysh floodplain against the background of increasing aridity in the region has the most adverse effect on agricultural activities. Therefore, the problem of conservation of the floodplain, with the total area from the Shulbinskaya hydropower station to the border with Russia of more than 400,000 ha, is one of the most urgent and today almost unresolved. Aim of the work is the analysis of the maximum water levels regime of the Irtysh river and the flooding conditions of the floodplain in the flat part of the watershed area within the Republic of Kazakhstan. Methods of research. The authors used geographic-hydrological and statistical methods of analysing the materials of observations of water levels in the Irtysh river at four gauge stations (Semey, Semyarskoye, Pavlodar and Irtyshskoye), located on the river downstream from the cascade of reservoirs. Due to the limited data, the regime of maximum levels for two time intervals - in natural (1935-1959) and in regulated (1967-2011) conditions - was investigated for Pavlodar station, and for the remaining gauges - only under regulated conditions. We used the methods of mathematical statistics to test time series for homogeneity (Fisher's and Student's criteria), and significance of trends (parametric and nonparametric criteria). The estimated maximum levels for inhomogeneous series were determined from the composite probability curves according to the existing standard SP 33-101-2003. The results. It is shown that the regime of maximum water levels in the Irtysh river in a lowland area between the gauge stations Semey and Irtyshskoye has undergone significant changes in comparison with the natural regime of 1937-1959. The genetic homogeneity of the maximum levels at Semey and Semiarskoe was disrupted: the annual maximum levels began to be observed also in winter. The decrease in water level of 1 % probability of exceedance at the city of Pavlodar is estimated as 1,11 m; 5 % - 0,94 m, and 10 % - 0,66 m compared to the period of unregulated flow regime 1937-1959. The amplitude of maximum water level fluctuations at Pavlodar decreased by 0,44 m. At present time the Irtysh floodplain, despite the environmental releases of water from the cascade of reservoirs, is flooded annually in the Republic of Kazakhstan only along the lower part of the river course (Pavlodar, Irtyshskoye), providing better conditions for maintaining floodplain soils fertility than higher upstream.
