Resumen
The Volga River is the largest river in Europe in terms of basin area (1.36 mio. km2), length (3531 km), and water content (annual flow 254 km3). We conduct long-term water quality studies in the Volga headwaters: in the Upper Volga Lakes, the free-flowing section, as well as in the Ivankovskoye and Uglich Reservoirs. At the source of the river, the water is very soft, slightly mineralized, characterized by high color indicators (up to 400 degrees Pt-Co scale) and permanganate oxidation (60.3?72 mgO/L). In the Upper Volga Lakes, water mineralization increases to 110 mg/L, and the color of the water decreases significantly. In the Ivankovo Reservoir, higher concentrations of manganese and BOD5 are noted than in the Volga above Tver. Based on total phosphorus concentrations, the Upper Volga Reservoir (Lake Volgo) and the free-flowing section of the Upper Volga (from Selizharovo to Tver) belong to the ?mesotrophic? class, and the Ivankovskoye Reservoir belongs to the ?eutrophic? class. We characterize the Volga headwaters based on physico-chemical parameters ?balanced? and discuss the relevance of ?natural pollution?. Especially the free-flowing section comprises an important reference section for lowland rivers; thus, long-term monitoring of abiotic and biotic aspects is an important issue.