Pesticides in streams in part of the Upper Mississippi River Basin, Minnesota and Wisconsin, 1974-94

Analysis of historical pesticide information by the National Water-Quality Assessment (NAWQA) Program indicates that land use and pesticide use affect detections of pesticides in streams in part of the Upper Mississippi River Basin (UMIS). Agricultural pesticide use was greatest in the Minnesota River Basin. Greater than twenty-seven times more herbicides than insecticides were used for agriculture. Pesticide detections were greatest in or downstream of agricultural and urban areas. Herbicides were detected most frequently in stream water; whereas, organochlorine insecticides were detected most frequently in streambed sediment. Most concentrations were below levels considered harmful to human and aquatic health.