Lake Onega water per year, of which 46% are industrial and household water, 25% is stormwater runoff and 16% is melioration-related drainage. This drainage contains of phosphorus and of nitrogen; respectively of these elements are removed through the River Svir whereas the rest accumulates in the lake. Ships and motor boats (about 8,000 units) bring oil pollution at the level of about per navigation year, as well as phenols (), lead () and oxides of sulfur, nitrogen, and carbon. The lake basin is a major source of granite, marble and black schist in Russia which have been exploited in the area since
Lake Onega Lake Onega has a surface area of without islands and a volume of ; its length is about and width about . It is the second largest lake in Europe, and the 18th largest lake by area in the world. Its southern banks are mostly low and continuous, whereas northern banks are rocky and rugged. They contain numerous elongated bays shaping the lake into a giant crayfish. In the northern part lies a large Zaonezhye Peninsula (); south of it, is the Big Klimenetsky () island. To the west of them lies the deep (deeper than ) Greater Onega ()