Ohio Phosphorus Loading Trends to Lake Erie
Figure 1. Ohio Phosphorus Loading Trends to Lake Erie
The phosphorus loading information summarized in Figure 1 is based on data from the Maumee, Sandusky, Cuyahoga, and Grand Rivers. Loadings fluctuate a great deal from year to year, reflecting the influence of weather, particularly the timing and intensity of storm events relative to the agricultural cycle. Intense storms that occur at times when fields are bare can result in one storm runoff event dominating the entire annual load.
A high loading year for one tributary tends to be a high loading year for all tributaries. Generally, loads and concentrations are higher for most years in the Maumee and Sandusky Rivers than they are in the Cuyahoga and Grand Rivers. This reflects the larger watershed area of the Maumee and the dominance of agricultural land use in the Maumee and Sandusky. The Cuyahoga and Grand Rivers have more forest and urban land use and smaller amounts of agriculture. In addition, the finer soils associated with the lake plains in the western Lake Erie drainage basin are conducive to higher loadings of fine-grained sediment and the phosphorus that is attached to it.