This picture is from USGS FS-116-99
Concentrations of nutrients and pesticides in streams and shallow ground water generally increase with increasing amounts of agricultural and urban land. This pattern is evident within small watersheds, as well as regionally, where similar land-use settings and chemical applications extend over broad areas. For example, intensive herbicide and fertilizer use in the Upper Midwest has resulted in elevated concentrations of atrazine, nitrogen, and phosphorus in streams throughout the region, including the Mississippi River. Management strategies that are successful in reducing use and transport of herbicides and fertilizers could lead to regional improvements in water quality. (Photo by Thomas L. Huntzinger)
