USGS Fact Sheet 001-94
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. Nonpoint-source contaminants from agricultural activities include pesticides, sediment,
nutrients (nitrogen and phosphorus), and fecal bacteria. 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.
Herbicides, including atrazine, are applied before planting and (or) as pre- and postcrop
emergent compounds during or after planting. In addition to agricultural usage, herbicides are
used in urban areas and in large quantities for weed control in industrial applications, such
as along railroad right-of-ways. 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 1986, as part of the National Water-Quality Assessment (NAWQA) Program, the U.S. Geological
Survey (USGS) began a study of the quality of surface water in a 15,300-square-mile (mi²)
area of the lower Kansas River Basin in southeastern Nebraska and northeastern Kansas
(see location map). The Delaware River Basin, which is a subbasin of the lower Kansas
River Basin, drains an area of 1,117 (mi²) at the outflow from Perry Lake. 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.
About 85 percent of the Delaware River Basin is agricultural land with about 40 percent in
row crops such as sorghum, soybeans, wheat, and corn. Mean annual precipitation is about 35
inches, and mean annual runoff is about 8 inches. Most of the precipitation falls from April
through September, which generally coincides with the growing season. Mean monthly runoff is
largest in spring and summer and smallest in fall and winter. Perry Lake is used for flood
control, recreation, and public-water supply. Outflows from the lake contribute about 9
percent of the streamflow in the Kansas River and can substantially affect the water quality
downstream on the Kansas River.
Herbicides, including, atrazine, alachlor, cyanazine, and metolachlor have been extensively
applied in the Delaware River Basin. Atrazine was applied in the largest amounts and was the
herbicide most frequently detected in the Delaware River. In 1989, an estimated 240,000
pounds of atrazine was applied to fields planted with corn and sorghum in the basin.
From January 1989 to February 1990, water samples were collected at least monthly from the
Delaware River upstream from Perry Lake near Muscotah, Kansas, and at the outflow of the
map). A markedly different pattern in seasonal fluctuations of atrazine concentrations in
streamflow is apparent between the unregulated upstream reaches of the Delaware River and the
regulated reach of the river downstream from Perry Lake. Atrazine concentrations (shown as
dots in graph) in the Delaware River upstream from the lake were lowest in January,
March, and April before atrazine was applied to the fields and highest in May, June, and July
after it was applied to the fields. The increase in atrazine concentrations from May through
July reflects the effects of precipitation and the subsequent surface runoff to streams. The
largest concentrations were 22 micrograms per liter (µ/L) in June 1989 and 9.4 µ/L in July.
After July, regardless of the amounts of streamflow in the Delaware River (shown as blue in
graph), atrazine concentrations began to decline; by February 1990, they had
decreased to 0.2 µ/L. The mean atrazine concentration for the 1989 calendar year was 2.8
In contrast to the unregulated upstream reach of the Delaware River, atrazine concentrations
in water samples collected from the Delaware River at the outflow of Perry Lake showed
little or no seasonal variability. Concentrations of atrazine gradually decreased from 5.0
µ/L in January 1989 to 1.7 µ/L in February 1990. The mean atrazine concentration for the
1989 calendar year was 3.5 µ/L, which is greater than the maximum contaminant level (MCL)
of 3.0 µ/L for atrazine that has been established by the U.S. Environmental Protection
Agency. Because the volume of water in Perry Lake is large in relation to its inflows, the
lake appears to attenuate the seasonal fluctuations in atrazine concentrations in the lake.
Atrazine concentrations in samples collected from the outflow of the lake are representative
of atrazine concentrations in the lake.
Public-water supplies are withdrawn from Perry Lake for two rural water districts and
several Federal- and State-owned recreational areas. Water withdrawn from the Delaware River
and Perry Lake receives no special treatment to remove atrazine. Water in the Kansas River
downstream from Perry Lake also is used for public-water supplies for Lawrence, Kansas, and
the Kansas City, Kansas, metropolitan area. Because withdrawn water from the Delaware River
and Perry Lake is not treated, concentrations of atrazine in these water supplies can
potentially exceed the annual MCL of 3.0 µ/L. Several studies have shown that atrazine can
be hazardous because of its extensive use, persistence in water, and water solubility and
because conventional water treatment (flocculation, sand filtration, chlorination) does not
effectively remove atrazine from the finished water.
Results from the NAWQA study were used by the Technical Advisory Committee of the Kansas State
Board of Agriculture as the basis for establishing the Delaware River Basin as a Pesticide
Management Area (PMA). This PMA is the first in the Nation in which land-management strategies
focus on decreasing the amount of atrazine in runoff that enters inland surface waters.
Administration of the PMA includes components of management and conservation practices,
education, monitoring, research, enforcement, and evaluation. The USGS provides streamflow and
water-quality information that is useful for the research and monitoring components of the PMA
through a Federal-State Cooperative Program between the USGS and the State of Kansas.
For information and selected readings about the lower Kansas River Basin study, write
U.S. Geological Survey
4821 Quail Crest Place
Lawrence, Kansas 66049
Adams, C.D., and Randtke, S.J., 1992, Removal of atrazine from drinking water by ozonation:
Journal American Water Works Association, v. 84, no. 9, p. 91-102.
Baker, M., Peterson, N., and Kamble, S.T., 1990, Pesticide use on crops in Nebraska--1987:
Lincoln, University of Nebraska Agricultural Research Division, 34 p.
Kansas State Board of Agriculture, 1990, Kansas farm facts: Topeka, Kansas, State Board of
Agriculture, 112 p.
Miltner, R.J., Baker, D.B., Speth, T.F., and Fronk, C.A., 1989, Treatment of seasonal
pesticides in surface waters: Journal American Water Works Association, v. 81, no. 1,
Nilson, E.B., Regehr, D.L., Russ, O.G., Fick, W.H., Morishita, D.W., Stahlman, P.W., Ohlen
busch, P.D., and Kuhlman, D.K., 1989, Chemical weed control for field crops, pastures,
rangeland, and noncropland: Manhattan, Kansas State University, 48 p.
U.S. Environmental Protection Agency 1992, Drinking water regulations and health advisories:
Washington, D.C., U.S. Environmental Protection Agency, 11 p.