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 at present. Cargo on Lake Onega amounts to 10–12 million tonnes per year with about 10,300 ship voyages. Lake shores contain two ports (Petrozavodsk and Medvezhyegorsk), 5 wharves (Kondopoga, Povenets, Shala, Vytegra and Ascension ()) and 41 piers. Fishery is an important activity on the lake. About 17 species are being fished commercially, mostly European cisco, smelt, whitefishes, roaches, burbot, pike-perch, perch, ruffe, carp bream, lake salmon, pike and somewhat less ide, graylings, common dace, common bleak and crucian carp. Whereas there is no regular passenger service on the lake, there are several tourist trips per day along the routes