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 Vozhe the fourth lake (also behind the Rybinsk Reservoir). Historically, Lake Vozhe was on the trading route connecting the basings of the Volga and the Onega via the Sheksna River. There is one big island on the lake, Spassky Island. On the island, ruins of the former monastery are located. The only inhabited locality on the lakeshore is the village of Charonda which is a former trading settlement founded in the 13th century, currently having the population under ten and almost deserted. Charonda does not have all-seasonal land connections. Formerly, the village of Vasilyevskaya was located on the northern lakeshore. It