Significant Findings of Water-Quality Studies and Implications

for Cheney Reservoir Watershed, South-Central Kansas, 1996–2001

U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet 009–02

March 2002

—Larry M. Pope

Prepared in cooperation with the

CITY OF WICHITA, KANSAS

Figure 1. Location of Cheney Reservoir watershed, surface-water-quality sampling sites, and nonagricultural soil-coring sites, south-central Kansas.

C heney R eservoir

North Fork

R iver

S ilver

C reek

Goose C reek

Irish C r

R ed R oc k

Arkansas R iver

Creek

Ninnescah

0 5 10 15 20 MILES

0 5 10 15 20 KILOMETERS

R eno C ounty

K ingman C ounty

Edwards C ounty

K iowa C ounty

Pawnee C ounty

S edgwick

C ounty

S tafford C ounty

Pratt C ounty

Stafford

Sylvia Abbyville Zenith

Penalosa

Pretty Prairie

Haven

Kingman Pratt

Langdon

Castle- ton

Turon

Preston

99 45' 30' 15' 98 97 45'

38

37 45'

50 Partridge

54

61

14

14

17

96

Base from U.S. Bureau of Census digital data, 1992, scales vary from 1:24,000 to 1:100,000,

Geographic projection and U.S. Geological Survey digital data, 1:100,000, 1983,

Universal Transverse Mercator projection, Zone 14

Converted to Albers Equal-Area Conic projection, standard parallels 29 30' and 45 30',

central meridian -96

EX PLANAT ION

Hutchinson

Index map

C ontributing drainage area

Noncontributing drainage area

B oundary of C heney R eservoir watershed

S urface-water-quality sampling site

and number

Nonagricultural soil-coring site

1

2

3

4

5

6

5 C heney R eservoir watershed

Wichita

K ANSAS

Water-quality issues in the Cheney Reservoir watershed were investigated from 1996Ð2001 as part of a cooperative effort between

the U.S. Geological Survey (USGS) and the city of Wichita, Kansas. Water quality in the Cheney Reservoir watershed is important

because much of the population of the area, which includes the Wichita metropolitan area, relies on Cheney Reservoir as a drinkingwater source and for recreational activities. Water-quality studies conducted during the investigation addressed the transport of

important water-quality constituents that included nutrients (nitrogen and phosphorus species), pesticides, bacteria, and suspended

solids. Conclusions drawn for most water-quality studies conducted in the Cheney Reservoir watershed were the result of samples

collected at six surface-water-quality sampling sites (five upstream and one downstream from Cheney Reservoir) and reservoirsediment and watershed-soil studies (fig. 1).

The water-quality studies are documented in the reports referenced in this fact sheet. Reports of all of these studies are available

on the World Wide Web at http://ks.water.usgs.gov/Kansas/qw/cheney/

Mean concentrations of nitrate in streamflow were much

less than drinking-water criteria.

Mean concentrations of phosphorus in streamflow

exceeded the established water-quality goal at all

sampling sites.

Agricultural activities have accounted for 65 percent of

the phosphorus transported to Cheney Reservoir.

Substantial reductions in phosphorus transported to

Cheney Reservoir may involve a combination of

approaches such as reducing phosphorus application

and changes in land-use, land-management, and

agricultural practices.

Median concentrations of pesticides in streamflow were less

than drinking-water criteria.

Numbers of fecal coliform bacteria in streams were large

during runoff but were less than water-quality criteria in

Cheney Reservoir.

Sediment accumulation in Cheney Reservoir was less than

expected.

Overview
0.50 

0.30 

0.25 

0.36 

0.23 

0.17 

0.10 

0.12 

0.08 

0.09 

0 

0.10 

0.20 

0.30 

0.40 

0.50 

0.60 

S urfa ce-w a ter -qua lity s a m pling s ite (fig. 1) 

P hos phorus concentra tio n, in m illigra m s per liter 

E stimated mean natural phosphorus concentrations 

L ong-ter m water-quality 

goal for str eams 

M ean phosphor us 

concentr ations 

(1 9 9 7 –2 0 0 0 ) 

Figure 2. Comparison of mean phosphorus concentrations in water samples from five 

surface-water-quality sampling sites in Cheney Reservoir watershed to mean 

concentrations estimated on the basis of an agricultural-enrichment factor of 2.9. The 

long-term water-quality goal for phosphorus in streams was established by the Cheney 

Reservoir Watershed Task Force Committee. 

Nutrients 

Mean concentrations of nitrate were small compared to 

the U.S. Environmental Protection Agency (USEPA) 

drinking-water criterion of 10 mg/L. Among the five 

surface-water-quality sampling sites upstream from 

Cheney Reservoir, mean concentrations of nitrate ranged 

from 0.43 (sampling site 2, fig. 1) to 1.6 mg/L 

(milligrams per liter) (sampling site 5) in surface-water 

samples collected during 1997Ð2000. However, mean 

concentrations of nitrate in water from four of the five 

sites were larger than the national mean background 

concentration of 0.6 mg/L, which may indicate that 

nitrate concentrations in streamflow in the Cheney 

Reservoir watershed are enriched as a result of 

agricultural activities (Milligan and Pope, 2001). 

Mean concentrations of total phosphorus exceeded 

water-quality goals. The long-term mean stream-waterquality goal of 0.10 mg/L for total phosphorus 

established by the Cheney Reservoir Watershed Task 

Force Committee was exceeded by mean concentrations 

of total phosphorus in water samples collected during 

1997Ð2000 from all five surface-water-quality sampling 

sites upstream from Cheney Reservoir (fig. 2). These 

mean concentrations ranged from 0.23 (sampling site 2, 

fig. 1) to 0.50 mg/L (sampling site 5) and were 

substantially larger than the 0.10-mg/L national mean 

background concentration of total phosphorus in streams, 

which indicates enrichment by agricultural activities or 

large natural concentrations in soils (Milligan and Pope, 

2001). Historically (1965Ð98), however, the mean total 

phosphorus concentration in the surface-water inflow to 

Cheney Reservoir was 0.76 mg/L as calculated on the 

basis of phosphorus deposited in the reservoir sediment 

(Mau, 2001). The implication of these relatively large 

mean phosphorus concentrations is that 

phosphorus input to Cheney Reservoir is 

sufficient to produce algal blooms (excessive 

growth of algae), possible taste-and-odor 

problems in treated drinking water, and 

potentially could reduce the aesthetic and 

recreational appeal of the reservoir. 

Phosphorus concentrations have been 

increasing over time. An analysis of 

reservoir bottom sediment indicated an 

increasing trend (since construction of the 

reservoir in 1965) in total phosphorus 

concentrations in water from the Cheney 

Reservoir watershed. This trend probably is 

related to human activities such as fertilizer 

use in crop production, which more than 

doubled between 1965 and 1996 (Mau, 2001). 

The amount of phosphorus annually 

transported from the watershed varied. 

Annual fluctuations in the amount of 

phosphorus transported by streams in the 

watershed resulted, in large part, from 

variability in precipitation and resulting runoff. Wetter 

years produced more phosphorus transport. Most of the 

annual phosphorus transport to Cheney Reservoir 

occurred during runoff (high-flow) conditions. For 

example, during 1997Ð2000, 72 percent of the 

phosphorus transport in streamflow at sampling site 4 

(fig. 1) occurred during runoff (Pope and others, 2002). 

The estimated mean annual phosphorus yield for the 

entire Cheney Reservoir watershed for 1997Ð98 was 

0.20 pound per acre (Pope and Milligan, 2000). 

Historically (1965Ð98), however, the mean annual 

phosphorus yield of the watershed was estimated at 

0.38 pound per acre (Mau, 2001). Estimated mean 

annual yields from watersheds of other reservoirs in 

Kansas have ranged from 0.02 to 1.76 pounds per acre. 

Agricultural activities accounted for 65 percent of the 

phosphorus transported to Cheney Reservoir. A 

comparison of the historical (1965Ð98) mean 

concentrations of phosphorus in sediment transported to 

Cheney Reservoir with the mean concentration of 

phosphorus in soil from 43 nonagricultural sites (fig. 1) 

in the Cheney Reservoir watershed indicated that 

agricultural activities increased the transport of 

phosphorus into Cheney Reservoir 2.9 times greater than 

that expected under natural conditions of phosphorus in 

soil. It was estimated that during 1965Ð98, 8.4 million 

pounds of phosphorus were transported to Cheney 

Reservoir. Ninety-two (92) percent of this phosphorus 

was deposited in the bottom sediment of the reservoir. 

The amount of phosphorus transported to Cheney 

Reservoir related to agricultural activities (65 percent of 

the total) was calculated from the total amount 

transported (8.4 million pounds) and the agriculturalenrichment factor (2.9). The implication of this large 

percentage of agriculturally related phosphorus is that a 

Nutrients 
0.001 

0.01 

0.1 

1. 0 

10 

1 2 3 4 5 6 

A lachlor 

A trazine 

M etolachlor 

A tra zine M C L (3 . 0 μg/ L ) 

A lachlor M C L (2 . 0 μg/ L ) 

* 

* L ess than analytical method r eporting limit 

S urfa ce-w a ter-qua lity s a m pling s ite (fig. 1) 

C oncentra tion, in m icrogr a m s per liter (μg/L ) Figure 3. Comparison of median concentrations of the three most 

commonly detected pesticides (alachlor, atrazine, and metolachlor) in 

water from surface-water-quality sampling sites in Cheney Reservoir 

watershed, 1997–99, and Maximum Contaminant Levels (MCLs) 

established by the U.S. Environmental Protection Agency. 

large potential exists for reducing phosphorus transport to 

Cheney Reservoir by changing agricultural activities 

(Pope and others, 2002). 

Substantial reduction in phosphorus transported to 

Cheney Reservoir may involve a combination of 

approaches such as reducing phosphorus application 

and changes in land-use, land-management, and 

agricultural practices. To determine if reductions in 

phosphorus application alone would reduce mean 

concentrations of total phosphorus in streams to 

acceptable levels (equal to or less than 0.10 mg/L), the 

agriculturally affected long-term (1997Ð2000) mean 

concentrations presented in figure 2 were divided by the 

agricultural-enrichment factor (2.9). These calculations 

produced estimated long-term mean concentrations of 

total phosphorus under natural concentrations of 

phosphorus in watershed soil (fig. 2). These estimated 

concentrations indicate that even under natural 

concentrations of phosphorus in watershed soil two 

(sampling sites 3 and 5, fig. 1) of the five surface-waterquality sampling sites in the Cheney Reservoir watershed 

still may not meet the long-term water-quality goal of 

0.10 mg/L. The implication of this finding is that in 

order to meet water-quality goals for total phosphorus in 

the watershed, a combination of approaches such as 

reducing phosphorus application and changes in land-use, 

land-management, and agricultural practices may be 

involved (Pope and others, 2002). 

Pesticides 

The occurrence of pesticides in surface water of the 

Cheney Reservoir watershed is widespread. At least 

one pesticide was detected in 99 percent of the 

streamflow samples collected between 1997 and 1999. 

Fifteen herbicides, one herbicide metabolite, and six 

insecticides were detected in streamflow samples from 

the Cheney Reservoir watershed. The herbicides alachlor, 

atrazine, and metolachlor were detected in 61, 99, and 

96 percent, respectively, of all streamflow samples 

(Milligan and Pope, 2000). 

Median concentrations of pesticides generally were 

small and less than drinking-water criteria. Median 

concentrations of alachlor and atrazine were less than 

their respective Maximum Contaminant Levels (MCLs) 

established by the U.S. Environmental Protection Agency 

(USEPA) (fig. 3). An MCL has not been established for 

metolachlor. The variability in median concentrations of 

alachlor, atrazine, and metolachlor among the six surfacewater-quality sampling sites probably is the result of 

variations in pesticide usage, amount of precipitation and 

runoff, topography, agricultural practices, and soil 

characteristics such as particle-size composition, porosity, 

and erodibility among the subwatershed areas represented 

by the sampling sites (Milligan and Pope, 2000). 

Potential adverse human health risks appear small. The 

implication of long-term exposure to small 

concentrations of pesticides in most streamflow samples 

for the population that relies on Cheney Reservoir as a 

drinking-water source is not of great concern on the basis 

of current (2001) water-quality criteria. However, the 

long-term effects of small concentrations of pesticides on 

aquatic life are not well known and may be an issue 

within the watershed (Milligan and Pope, 2000). 

Bacteria 

Bacteria of fecal origin are common in streams of the 

Cheney Reservoir watershed. The sanitary quality of 

water and its use as a public drinking-water supply and 

for recreation were evaluated on the basis of fecal 

coliform bacteria densities. Fecal coliform bacteria were 

detected in streamflow samples from all surface-waterquality sampling sites in the watershed (fig. 4) (Mau and 

Pope, 1999). 

Large fecal coliform densities are common in streams 

during runoff conditions. Relatively large median fecal 

coliform densities were associated with runoff conditions 

at sampling sites upstream from Cheney Reservoir, and 

the median density at sampling site 3 was substantially 

larger than the 2,000-col/100 mL (colonies per 

100 milliliters of water) water-quality criterion for 

secondary contact recreation (such as wading and fishing) 

established by the Kansas Department of Health and 

Environment (fig. 4). In contrast, median densities during 

base-flow (low-flow) conditions were substantially less 

than the 2,000-col/100 mL criterion in water from all five 

surface-water-quality sampling sites upstream from 

Cheney Reservoir. Fecal coliform densities are typically 

much greater in streams during runoff conditions because 

of nonpoint-source contributions from the watershed. 

These contributions can originate from deposition of 

fecal material by livestock and wildlife or from the use of 

manure as a soil amendment (Mau and Pope, 1999). 

Pesticides Bacteria 
0 

500 

200 

1, 000 

1, 500 

2, 000 

2, 500 

3, 000 

3, 500 

4, 000 

1 2 3 4 5 6 

S urfa ce-w a ter-quality s a m pling s ite (fig. 1) 

M edia n fecal co lifo r m ba cteria dens ity , in colonies 

per 100 m illiliters o f w a ter 

B ase flow 

R unoff S econdary contact 

recreation criterion 

C riterion applicable only 

during bas e-flow conditions . 

P rimary contact 

recreation criterion 

R eservoir outflow 

Figure 4. Comparison of median densities of fecal coliform bacteria in water from surface-waterquality sampling sites in Cheney Reservoir watershed during base-flow and runoff conditions for 

1997–98 (primary and secondary contact recreation criteria from Kansas Department of Health and 

Environment). 

* 

* 

* 

Fecal coliform densities were much less in Cheney 

Reservoir than in its tributary streams. The median 

fecal coliform density in water samples from the outflow 

of Cheney Reservoir (sampling site 6, fig. 1) for 1997Ð98 

was about 11 col/100 mL, substantially less than the 

200-col/100 mL water-quality criterion for primary 

contact recreation (such as swimming) (fig. 4). The 

relatively small median density of fecal coliform bacteria 

in the outflow from Cheney Reservoir is attributed to the 

fact that bacteria transported into the reservoir by 

tributary streams are subject to die off and predation by 

other organisms. The physical process of dilution by 

reservoir water and deposition also play a role in 

decreasing bacterial densities in reservoir outflow. The 

implication of the relatively small median density of fecal 

coliform bacteria is that water flowing out of the reservoir 

generally is of acceptable sanitary quality for swimming 

and other contact activities (Mau and Pope, 1999). 

Suspended solids 

Deposition of suspended solids in Cheney Reservoir was 

less than expected. One of the principal concerns with 

the transport of suspended solids (sediment) into Cheney 

Reservoir is a loss of reservoir storage capacity. Cheney 

Reservoir has a sediment-trapping efficiency of 

99 percent (Pope and others, 2002). Decreases in 

reservoir storage capacity can affect reservoir allocations 

used for flood control, drinking-water supplies, 

recreation, and wildlife habitat. Reservoirs in Kansas 

commonly were designed to provide 100 years of 

sediment deposition. As of 1998, 34 years of sediment 

deposition had occurred in Cheney Reservoir, which 

equates to 34 percent of the design life of the reservoir. 

However, only 27 percent of the allocated sediment 

storage capacity had been used. The implication of this 

finding is that although sediment is 

effectively trapped in Cheney 

Reservoir, it is accumulating at a rate 

less than expected, which may extend 

the useful life of the reservoir beyond 

100 years. Also, this finding may be 

an indication that efforts to reduce 

erosion (transport of sediment) in the 

watershed have been effective (Mau, 

2001). 

References 

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 

Investigations Report 97Ð4153, 13 

p. 

Mau, D.P., 2001, Sediment deposition 

and trends and transport of 

phosphorus and other chemical constituents, Cheney Reservoir 

watershed, south-central Kansas: U.S. Geological Survey 

Water-Resources Investigations Report 01Ð4085, 40 p. 

Mau, D.P., and Pope, L.M., 1999, Occurrence of fecal coliform 

bacteria in the Cheney Reservoir watershed, south-central 

Kansas, 1997Ð99: U.S. Geological Survey Fact 

Sheet 170Ð99, 4 p. 

Milligan, C.R., and Pope, L.M., 2000, Occurrence of pesticides 

in streams of the Cheney Reservoir watershed, south-central 

Kansas, 1997Ð99: U.S. Geological Survey Fact Sheet 096Ð00, 

4 p. 

______2001, Occurrence of phosphorus, nitrate, and suspended 

solids in streams of the Cheney Reservoir watershed, southcentral Kansas, 1997Ð2000: U.S. Geological Survey WaterResources Investigations Report 01Ð4199, 18 p. 

Pope, L.M., 1998, Watershed trend analysis and water-quality 

assessment using bottom-sediment cores from Cheney 

Reservoir, south-central, Kansas, 1997Ð98: U.S. Geological 

Survey Water-Resources Investigations Report 98Ð4227, 

24 p. 

Pope, L.M., and Milligan, C.R., 2000, Preliminary assessment of 

phosphorus transport in the Cheney Reservoir watershed, 

south-central Kansas, 1997Ð98: U.S. Geological Survey 

Water-Resources Investigations Report 00Ð4023, 29 p. 

Pope, L.M., Milligan, C.R., and Mau, D.P., 2002, Historical 

contributions of phosphorus from natural and agricultural 

sources and implications for stream water quality, Cheney 

Reservoir watershed, south-central Kansas: U.S. Geological 

Survey Water-Resources Investigations Report 02Ð4021, 

25 p. 

For World Wide Web access to Cheney Reservoir watershed publications: 

http://ks.water.usgs.gov/Kansas/qw/cheney 

or contact: 

District Chief, U.S. Geological Survey 

4821 Quail Crest Place, Lawrence, Kansas 66049 

(785) 842–9909 

email: dc_ks@usgs.gov 

Suspended solids 

References