Oneida Lake, the largest lake within New York State, supports massive algae blooms that interfere with one of its major uses, recreation. As part of a study of the algae problem, a chemical balance for the lake and its drainage basin has been made. The quantities of major dissolved species entering the lake are determined for each of the hydrochemically homogeneous terrains comprising the basin. The largest terrain, the Tug Hill terrain to the north of the lake contributes more than half the total streamflow to the lake, but is underlain by chemically unreactive bedrock and glacial deposits and its mean annual dissolved-solids contribution is only 0.25 t per d per sq mi (tons per day per square mile). Adjacent to Oneida Lake and extensive to the south and west is the Lake Plain terrain, underlain by sediments from ancestral Oneida Lake and contributing dissolved solids to streams at the moderate rate of 0.57 t per d per sq mi. At the foot of the Appalachian Upland escarpment is the Salina Group terrain, underlain by gypsiferous shales and carbonate rocks, and contributing more dissolved solids than any other terrain--32 t per d per sq mi. Within the Appalachian Upland, in the extreme southern part of the basin are two terrains underlain by glacial sand and gravel and by glacial till and bedrock. Their contributions are 0.58 and 0.85 t per d per sq mi, respectively. Throughout the basin, the dissolved-solid contribution of precipitation is 0.06 t per d per sq mi. Lake input is balanced by lake output for all major species except sulfate and possibly calcium and magnesium, which are retained in the lake.

Stream nitrogen loads are about 0.0016 t per d per sq mi throughout the basin, a value lower than that typical of undeveloped grassland and forest. In the southern part of the basin, this load is increased to 0.0020 t per d per sq mi by sewered wastes. Nitrogen loads leaving balance those entering the lake.

Phosphate loads are consistent with the geology of the several terrains and range from 0.0006 to 0.0034 t per d per sq mi. Domestic and industrial wastes, lakeshore cottages, and boaters and recreationists probably contribute not more than 30 percent of the phosphate entering the lake. Phosphate is strongly retained in the lake.