Abstract

Water release from reservoirs to improve the environmental condition of floodplains is of great relevance. Thus, the aim of this study was to propose a method to assess ecological drawdowns from power station reservoirs. An example of its application for the Volga River downstream area is presented. The efficiency of the quantitative assessment of ecological water discharge from the reservoir of the Volgograd hydroelectric power station is analyzed and discussed in relation to the improvement of the environmental condition of the Volga-Akhtuba floodplain, which covers an area of 6.1 × 10³ km². It is shown that a decrease of spring-summer flooding worsened significantly its environmental condition, i.e. biodiversity decreased by 2-3 times, soil fertility declined by 25%, floodplain relief deformation occurred and the productivity of semi-migratory fish decreased by more than 3 times. The economic benefit accumulated from river flow regulation was » 300 × 10⁶ USD in 2011, and economic damage related to the deterioration of the ecological situation was estimated at » 400 × 10⁶ USD in the same year. It is impossible to fully satisfy the needs of all the participants in the water-economic complex in the assessment of the environmental flows. Priority should be given to environmental requirements. It was found that assessing the ecological drawdowns confirmed the possibility of improving the floodplain environment by reducing between 15-20% the electricity production. This would allow conserving the region’s biodiversity and increasing about 60-80% the natural vegetation productivity. This will prevent deformation of the floodplain relief and doubling the productivity of semi-migratory fish.

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