April 1995 Atrazine Concentrations in the Delaware River, Kansas By John K. Stamer, Kathryn D. Gunderson, and Barbara J. Ryan Contamination of surface and ground water from nonpoint agricultural sources is a national issue. Of these contaminants, pesticides in water receive the most attention because at elevated levels, many are potential human carcinogens and are toxic to aquatic life.
Farmers depend on pesticides, including herbicides, to increase crop yields.
Herbicides prevent or inhibit the growth of weeds that compete for nutrients and moisture needed by the crops. If weeds are harvested with the crops, then the value of the crop decreases. The amount and timing of pesticide use, as well as the quantity of streamflow at certain times of the year, can affect concentrations of pesticides in water. The subbasin is characterized by deposits of glacial till, which comprises silt, clay, sand, gravel, and boulders. The topography is hilly, particularly in areas in the headwaters of the subbasin.