U.S. Geological Survey Water-Resources Investigations Report 97-4153
Prepared in cooperation with the CITY OF WICHITA, KANSAS
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Occurrence of Dissolved Solids, Nutrients, Atrazine, and Fecal Coliform Bacteria During
Low Flow in the Cheney Reservoir Watershed, South-Central Kansas, 1996
By V.G. Christensen and L.M. Pope
Abstract
A network of 34 stream sampling sites was established in the 1,005-square-mile Cheney
Reservoir watershed, south-central Kansas, to evaluate spatial variability in concentrations
of selected water-quality constituents during low flow. Land use in the Cheney Reservoir
watershed is almost entirely agricultural, consisting of pasture and cropland. Cheney
Reservoir provides 40 to 60 percent of the water needs for the city of Wichita, Kansas.
Sampling sites were selected to determine the relative contribution of point and nonpoint
sources of water-quality constituents to streams in the watershed and to identify areas of
potential water-quality concern. Water-quality constituents of interest included dissolved
solids and major ions, nitrogen and phosphorus nutrients, atrazine, and fecal coliform
bacteria.
Water from the 34 sampling sites was sampled once in June and once in September 1996 during
Phase I of a two-phase study to evaluate water-quality constituent concentrations and loading
characteristics in selected subbasins within the watershed and into and out of Cheney
Reservoir. Information summarized in this report pertains to Phase I and was used in the
selection of six long-term monitoring sites for Phase II of the study.
The average low-flow constituent concentrations in water collected during Phase I from all
sampling sites was 671 milligrams per liter for dissolved solids, 0.09 milligram per liter for
dissolved ammonia as nitrogen, 0.85 milligram per liter for dissolved nitrite plus nitrate as
nitrogen, 0.19 milligram per liter for total phosphorus, 0.20 microgram per liter for
dissolved atrazine, and 543 colonies per 100 milliliters of water for fecal coliform bacteria.
Generally, these constituents were of nonpoint-source origin and, with the exception of
dissolved solids, probably were related to agricultural activities. Dissolved solids probably
occur naturally as the result of the dissolution of rocks and ancient marine sediments
containing large salt deposits. Nutrients also may have resulted from point-source discharges
from wastewater-treatment plants.
An examination of water-quality characteristics during low flow in the Cheney Reservoir
watershed provided insight into the spatial variability of water-quality constituents and
allowed for between-site comparisons under stable-flow conditions; identified areas of the
watershed that may be of particular water-quality concern; provided a preliminary evaluation
of contributions from point and nonpoint sources of contamination; and identified areas of the
watershed where long-term monitoring may be appropriate to quantify perceived water-quality
problems.
Christensen, V.G., and Pope, L.M., 1997, Occurrence of Dissolved Solids, Nutrients,
Atrazine, and Fecal Coliform Bacteria During Low Flow in the Cheney Reservoir Watershed,
South-Central Kansas, 1996: U.S. Geological Survey Water-Resources Investigation Report
97-4153, 13 p.
To request a paper copy of this publication, email:
GS-W-KS_info@usgs.gov
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