Concentrations and transport of atrazine in the Delaware River-Perry Lake system, northeast Kansas, July 1992 through September 1995

About 283,000 pounds of atrazine are applied annually in the 1,100-square-mile Delaware River basin. Of this amount, an annual average of 3,500 pounds runs off into Perry Lake, a public-water supply source and main reservoir in the basin. About 90 percent of the atrazine that runs off to streams occurs between May and July. However, annual average concentrations did not exceed the maximum contaminant level in water from any of 10 stream sites or the outflow of Perry Lake for either the 1993 or 1994 crop years.