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
Onega Canal of the lake. At the mouth of the canal, in the selo of Voznesenye, a memorial obelisk has been erected. The canal lost its significance after Mariinsk Canal System was reconstructed and became Volga-Baltic Waterway. Onezhsky Canal was not reconstructed and became too shallow for larger boats. It is still navigable, but not used for regular navigation. Two rivers, Vozheroksa and Oshta, tributaries of Lake Onega, cross the canal. from the Vytegra, the canal crosses Lake Megrskoye, a large freshwater lake. There is weak current in the canal in the direction of the Svir. Onega Canal The Onega Canal ()