TRIBUTARY AND POINT-SOURCE TOTAL PHOSPHORUS LOADING TO LAKE ERIE

Total phosphorus data from tributaries, municipal and industrial sources, connecting channels, and atmospheric deposition have been evaluated to estimate the loading of phosphorus to Lake Erie. The annual total load from these sources has declined over the study period from a high of 27,944 tons in 1968 to a low of 10,452 tons in 1981. Of all sources the Detroit River represented the single largest component of the total load. Reductions in the Detroit River annual load, which is a complement of both U. S. and Canadian loads, from 17,822 tons to 3,541 tons was principally responsible for the overall total phosphorus loading decrease. These decreases were attributed principally to the phosphorus abatement program on municipal sources and the restriction of phosphate concentrations in detergents.