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The Delaware River Watershed is located in northeastern Kansas and consists of surface water in ten sub-watersheds draining 2,893 square kilometers. Approximately 85 percent of the land area in the basin is cultivated cropland. The Delaware River flows into Perry Reservoir near Lawrence, Kansas. Releases from the reservoir are used to maintain streamflow in the Kansas River during low flow periods, contributing 10 percent of the mean flow of the Kansas River which is used as sources of public drinking water and meet many of the municipal drinking water supply needs of the urban population in Kansas along the Kansas River.

Elevated concentrations of pesticides in the Delaware River and Perry Reservoir caused legislative authority to implement the first pesticide management area in Kansas. The purpose of this management area was to assess the sources of the contamination and potential systems to reduce the daily loading of those contaminants. Pesticides cause significant problems for municipal water treatment plants in Kansas, as they are not appreciably removed during conventional water treatment processes unless activated carbon filtering is used. Pesticides have been detected during all months of the year with average annual concentrations exceeding maximum contaminate levels. If high concentration in water is associated with high flow conditions, then large mass losses of pesticides can flow into these water supplies. This paper investigated the use of a monitoring program to assess the non-point source of this watershed contamination. Atrazine application timing was examined for its ability to remediate or prevent these impairments. The success of this practice has been shown with continued monitoring and the Delaware River and Perry Reservoir being removed from the Kansas reported TMDL impaired water bodies.