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DIFFUSE BIOGENIC POLLUTION OF WATER BODIES IN THE VOLGA RIVER BASIN — EXAMPLE OF CHEBOKSARY RESERVOIR BASIN
Since 1990, water use in Russia has decreased significantly (up to 30%). However, significant improvement in surface water quality has not occurred, especially in the Volga River Basin, Russia’s main river. Unsatisfactory water quality in the Volga River Basin seems to result from uncontrolled nonpoint (or diffuse) pollution from basins. To localize the primary sources of diffuse pollution in the Volga River Basin was selected representative site: Cheboksary Reservoir Basin. The Cheboksary Reservoir is located in the central part of the Volga River Basin and has the largest local basin of the Volga reservoirs (135,000 km2). To calculate the diffuse flow of biogenic elements (BE) from the Cheboksary Reservoir Basin, we used the landscape-hydrological method. The landscape structure of the basin, the anthropogenic influences, and the processes of flow modification in the basin were accounted. In general, from the entire basin area, the Cheboksary Reservoir receives an average of 20,900 tons of mineral nitrogen and 950 tons of mineral phosphorus by diffuse flow, which makes up approximately 80% of the total flow of BE entering the Reservoir. The contribution of fertilization and household waste products to the diffuse removal from the entire catchment of the Cheboksary Reservoir is about 30%. The diffuse nitrogen flow from the basin to the mouth is reduced due to basin retaining by almost two and phosphorus by three times in the Cheboksary Reservoir Basin.