U.S. Department of the Interior

U.S. Geological Survey

Historical Contributions of Phosphorus From

Natural and Agricultural Sources and

Implications for Stream Water Quality,

Cheney Reservoir Watershed,

South-Central Kansas

By LARRY M. POPE, CHAD R. MILLIGAN, and DAVID P. MAU

Water-Resources Investigations Report 02–4021

Prepared in cooperation with the

CITY OF WICHITA, KANSAS

Lawrence, Kansas

2002

U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with the

CITY OF WICHITA, KANSAS

Historical Contributions of Phosphorus From

Natural and Agricultural Sources and

Implications for Stream Water Quality,

Cheney Reservoir Watershed,

South-Central Kansas

Water-Resources Investigations Report 02–4021
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

For additional information write to: Copies of this report can be purchased from:

District Chief U.S. Geological Survey

U.S. Geological Survey Information Services

4821 Quail Crest Place Building 810

Lawrence, KS 66049–3839 Box 25286, Federal Center

Denver, CO 80225–0286
Content

CONTENTS

Abstract.................................................................................................................................................................................. 

Introduction ........................................................................................................................................................................... 

Setting.......................................................................................................................................................................... 

Previous Investigations ................................................................................................................................................ 

Purpose and Scope....................................................................................................................................................... 

Methods ................................................................................................................................................................................. 

Soil-Core Collection, Processing, and Analysis.......................................................................................................... 

Quality Control............................................................................................................................................................ 

Sequential Replicate Samples............................................................................................................................ 

Split Replicate Samples..................................................................................................................................... 

Historical Contributions of Phosphorus................................................................................................................................. 

Natural Soil Concentrations......................................................................................................................................... 

Agricultural Enrichment .............................................................................................................................................. 

Particle-Size Weighted Concentrations ............................................................................................................. 

Phosphorus Mass ............................................................................................................................................... 

Natural and Agricultural Sources ................................................................................................................................ 

Phosphorus and Sediment Retention Efficiencies of Cheney Reservoir ............................................................................... 

Implications for Stream Water Quality.................................................................................................................................. 

Summary and Conclusions .................................................................................................................................................... 

References ............................................................................................................................................................................. 

FIGURES

1. Maps showing location of Cheney Reservoir watershed and nonagricultural soil-coring sites, south-central

Kansas ..................................................................................................................................................................... 

2. Photograph showing soil-coring site 27, cemetery east of Langdon, Kansas ......................................................... 

3. Graph showing comparison of total phosphorus concentrations and particle sizes less than 0.062 millimeter

in diameter between 2-inch and 8-inch soil-core samples collected from 43 nonagricultural sites in and

near Cheney Reservoir watershed, September 1999............................................................................................... 

4. Map showing distribution of total phosphorus concentrations in 2-inch and 8-inch soil-core samples at

43 nonagricultural coring sites in and near Cheney Reservoir watershed, September 1999 .................................. 

5. Map showing distribution of soil particle size in 2-inch and 8-inch soil-core samples at 43 nonagricultural

coring sites in and near Cheney Reservoir watershed, September 1999................................................................. 

6–9. Graphs showing:

6. Relation between total phosphorus concentrations in bottom-sediment core samples and normalized depth

of samples from selected coring sites in Cheney Reservoir, 1965–97 .............................................................. 

7. Relation between mean percentage of bottom-sediment particles less than 0.062 millimeter in diameter and

mean concentrations of total phosphorus in bottom-sediment samples from 10 coring sites in Cheney

Reservoir, August 1997 ..................................................................................................................................... 

8. Comparison of particle-size weighted mean total phosphorus concentrations in soil-core samples from

43 nonagricultural sites in and near Cheney Reservoir watershed, September 1999, and in bottom-sediment

samples from Cheney Reservoir, August 1997.................................................................................................. 

9. Comparison of phosphorus transported to Cheney Reservoir from natural and agricultural sources, 1965–98 

10. Map showing location of streamflow sampling sites in Cheney Reservoir watershed ........................................... 

11. Graph showing comparison of measured mean total phosphorus concentrations in water samples from five

streamflow sampling sites in Cheney Reservoir watershed and mean concentrations estimated on basis

of agricultural-enrichment factor of 2.9 .................................................................................................................. 
IV Historical Contributions of Phosphorus From Natural and Agricultural Sources and Implications for Stream Water Quality, Cheney Reservo

South-Central Kansas

TABLES

1. Location of soil-coring sites in and near Cheney Reservoir watershed, south-central Kansas ...................

2. Results of analyses of total phosphorus concentrations and particle-size determinations for selected soil 

in and near Cheney Reservoir watershed, south-central Kansas, September 1999 .....................................

3. Description of streamflow sampling sites in Cheney Reservoir watershed, south-central Kansas .............

4. Number of samples analyzed and mean concentrations of total phosphorus in streamflow during base-flo

runoff, and long-term streamflow conditions at sampling sites 1–5 in Cheney Reservoir watershed, south

Kansas, 1997–2000......................................................................................................................................

CONVERSION FACTORS AND ABBREVIATIONS

Multiply By To obtain

acre-foot (acre-ft) 1,233 cubic meter

cubic foot per second (ft3/s) 0.02832 cubic meter per second

degree Fahrenheit (oF) (1)

1

Temperature can be converted to degrees Celsius (oC) or degrees Fahrenheit (oF) by the

equations: oC = 5/9 (oF - 32) o

F = 9/5 (oC) + 32.

degree Celsius

foot (ft) 0.3048 meter

gram per second (g/s) 0.0022 pound per second

inch (in.) 2.54 centimeter

mile (mi) 1.609 kilometer

milligram per kilogram (mg/kg) 1.6 x 10-5 ounce per pound

milligram per liter (mg/L) 1.0 part per million

millimeter (mm) 0.03937 inch

pound (lb) 0.4536 kilogram

pound per acre (lb/acre) 1.121 kilogram per hectare

square mile (mi2

) 2.590 square kilometer
Abstrac

Historical Contributions of Phosphorus From Natural and

Agricultural Sources and Implications for Stream Water

Quality, Cheney Reservoir Watershed, South-Central Kansas

By Larry M. Pope, Chad R. Milligan, and David P. Mau

Abstract

An examination of soil cores collected from

43 nonagricultural coring sites in the Cheney

Reservoir watershed of south-central Kansas was

conducted by the U.S. Geological Survey in

September 1999. The cores were collected as part

of an ongoing cooperative study with the city of

Wichita, Kansas. The 43 sites (mostly cemeteries)

were thought to have total phosphorus concentrations in the soil that are representative of natural

conditions (unaffected by human activity). The

purpose of this report is to present the analysis

and evaluation of these soil cores, to quantify the

phosphorus contributions to Cheney Reservoir

from natural and agricultural sources, and to provide estimates of stream-water-quality response to

natural concentrations of total phosphorus in the

soil.

Analysis of soil cores from the 43 sites produced natural concentrations of total phosphorus

that ranged from 74 to 539 milligrams per kilogram with a median concentration of 245 milligrams per kilogram in 2-inch soil cores and from

50 to 409 milligrams per kilogram with a median

concentration of 166 milligrams per kilogram in

8-inch soil cores. Natural concentrations of total

phosphorus in soil were statistically larger in samples from coring sites in the eastern half of the

watershed than in samples from coring sites in the

western half of the watershed. This result partly

explains a previously determined west-to-east

increase in total phosphorus yields in streams of

the Cheney Reservoir watershed. A comparison of

total phosphorus concentrations in soil under 

ural conditions to the historical mean total ph

phorus concentration in agriculturally enriche

bottom sediment in Cheney Reservoir indicat

that agricultural activities within the watershe

have increased total phosphorus concentration

watershed soil that is transported in streams to

about 2.9 times natural concentrations.

Retention efficiencies for phosphorus and 

iment historically transported to Cheney Rese

voir were calculated at 92 and 99 percent,

respectively. Most of the phosphorus was

retained in bottom sediment. Sediment accum

tion in Cheney Reservoir was less than reserv

design-life specifications on the basis of the a

of the reservoir.

Estimates of mean total phosphorus conce

trations for selected streams in the Cheney Re

voir watershed under natural concentrations o

total phosphorus in soil and a historic set of

watershed conditions indicate that water from 

of the five streamflow sampling sites would n

meet the total phosphorus water-quality goal o

0.10 milligram per liter established by the Che

Reservoir Watershed Task Force Committee.

These results imply that the water-quality goa

total phosphorus in some streams of the water

shed may not be met simply by reducing the

amount of phosphorus applied. Instead, meet

the goal could involve a combination of

approaches—for example, reducing the agricu

tural distribution of phosphorus and implemen
2 Historical Contributions of Phosphorus From Natural and Agricultural Sources and Implications for Stream Water Quality, Cheney Reser

Watershed, South-Central Kansas

changes in watershed activities to mitigate phosphorus movement to surface water.

INTRODUCTION

Fertilizers are an important component of modern

agriculture. Their use increases soil fertility and

increases crop yields. Phosphorus is a macronutrient

required by plants for growth and reproduction and

occurs naturally in soils in varying concentrations as

the result of weathering of inorganic compounds such

as the mineral apatite (calcium phosphate) (Morgan,

1997); however, in soils routinely used for crop production, phosphorus may be depleted through plant

uptake and subsequent harvest of the crop. Therefore,

during much of the 20th century, the annual application of phosphorus-containing fertilizers to agricultural soils became a common practice.

Phosphorus often is added to agricultural soils in

the form of an inorganic phosphate or in an organic

form as a component of manure from confined animalfeeding operations (Smith and others, 1998) or human

sewage disposal (Eberle and others, 1994). Historically, however, the routine annual application of phosphorus to agricultural soils has been in excess of crop

requirements and has led to a buildup of soil phosphorus concentrations beyond that of agronomic need

(Sharpley and others, 1994; Carpenter and others,

1998). This buildup of soil phosphorus has increased

the potential for phosphorus transport to surface water

in runoff from agricultural fields (Smith and others,

1986; Sharpley and others, 1999).

The use of phosphorus compounds as fertilizers

can have detrimental effects on surface-water bodies

receiving runoff from areas of application. Excess

phosphorus in surface water can accelerate the natural

eutrophication (nutrient enrichment) of lakes and reservoirs (Daniel and others, 1998). Eutrophication in

its broadest definition is the enrichment of a water

body due to an increase in nutrient loading (Horne and

Goldman, 1994). Phosphorus is considered a major

component of eutrophication because it is normally

the nutrient in shortest supply and, thus, can be the

controlling factor in biological production rates (Hem,

1985, p. 128). Accelerated phosphorus enrichment

may be characterized by extensive algal growth (algal

blooms) that may reduce the aesthetic and recreational

value of the water, produce taste-and-odor problems in

drinking water, and, in severe cases, stress or kill

aquatic organisms as a result of dissolved oxygen

depletion or the release of neuro- and hepatot

when algal blooms die (Sharpley, 1995).

The effects of eutrophication can be most 

nounced on lakes and reservoirs that serve as 

quality integrators (summation of upstream c

ent characteristics) for their watersheds. Chen

Reservoir, on the North Fork Ninnescah Rive

south-central Kansas (fig. 1), may be a reserv

the potential for detrimental effects from nutr

enrichment and, in fact, has a history of algal 

and taste-and-odor problems in treated drinki

(Cheney Reservoir Watershed Task Force Com

written commun., 1996).

To address the eutrophication issues in C

Reservoir and nutrient (nitrogen and phospho

cies) transport from the Cheney Reservoir wa

the U.S. Geological Survey (USGS) entered i

cooperative study with the city of Wichita in 

The study was designed to assess the occurre

transport of selected water-quality constituen

including phosphorus, within the watershed a

describe their potential effect on Cheney Rese

major source of public-water supply for Wich

surrounding communities.

Results from the study will be useful to w

managers in evaluating the sources and transp

phosphorus in the Cheney Reservoir watershe

potential for meeting in-stream total maximum 

loads (TMDLs) for phosphorus under existing 

posed land-use and land-management practic

TMDL is a calculation of the maximum amou

contaminant that a water body can receive wit

lating State water-quality standards. Results 

have transferability to other watersheds in Kan

similar land-use characteristics and phosphor

bution patterns. The rather unique sampling m

used for this study could have transferability 

out the Nation where a comparison of the his

transport of water-quality constituents to natu

ditions (unaffected by human activity) is requ

This comparison would be particularly suited 

sheds with downstream impoundments where 

record of historical transport may be containe

bottom sediment.

Setting

Cheney Reservoir is a 15-mi2 surface are

impoundment constructed in 1965 mainly for 

control. The reservoir also serves as a water-s
Introductio

Cheney

Reservoir

North

Fork

River

Silver

Creek

Goose Creek

Irish Cr

Red Rock

Arkansas River

Creek

Ninnescah

0 5 10 15 

0 5 10 15 20 KILOMETERS

50

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°00'

EXPLANATION

Hutchinson

Index map

Cheney

Reservoir

watershed

Konza Prairie

Biological Station

Wichita

Hillsdale KANSAS Lake

Contributing drainage area

Noncontributing drainage area

Boundary of Cheney Reservoir watershed

Nonagricultural soil-coring site and number

Haviland

Wellsford

Byers

Saint John

Iuka

Cunningham

Lerado

Huntsville

Sain

Plevna

18

18

26

17

16

13

28

27

23

12

15 10

14

22

25

24

20 19

21

32

31

30

35

33

34

36 37

39

40

41

43

4

38

29

8 9

4

3

2 1

7

11

6 5 Reno County

Kingman County

Edwards County

Kiowa County

Pawnee County

Sedg

Coun

Stafford County

Pratt County

Stafford

Sylvia Abbyville Zenith

Penalosa

Arlington

Pretty Prairie

Haven

Kingman Pratt

Langdon

Castleton

Turon

Preston

99° 45' 30' 15' 98° 97°45

38°

37°45'

Partridge

Western half of basin Eastern half of basin

source for about 350,000 people in and around Wichita (Jerry Blain, city of Wichita, Kansas, Water and

Sewer Department, oral commun., 2000). The reservoir has a mean depth of about 16 ft and a

conservation-pool storage of 151,800 acre-ft with

an additional flood-control pool capacity of

80,860 acre-ft.

The watershed of Cheney Reservoir is a 933-mi2

contributing drainage area of the North Fork Ninnescah River used almost exclusively for crop and

livestock production. Since 1965, the percentage of

watershed used for major crop production (corn, sorghum, soybean, and wheat) has averaged about 52 percent annually. The remainder of the watershed is used

mainly as pasture for livestock production. Annual

inventories of livestock since 1965 have averaged

about 64,000 cattle and calves, 18,000 hogs and pigs,

and 9,400 sheep and lambs (Kansas State Board of

Agriculture and U.S. Department of Agriculture,

1964–94; Kansas Department of Agriculture and U.S.

Department of Agriculture, 1995–97).

Human population in the watershed is less tha

4,000, much of which is associated with the appro

mately 1,000 farms in the watershed (Cheney Res

voir Watershed Task Force Committee, written

commun., 1996). Populations of the six largest to

in the watershed range from less than 200 to sligh

more than 1,200 people (Helyar, 1994).

In south-central Kansas, precipitation and tem

ature vary substantially throughout the year. The

mean annual (1961–90) precipitation is about 27 

but ranges in the vicinity of the Cheney Reservoir

watershed from about 25.8 in. at Pratt (fig. 1) to a

29.2 in. at Hutchinson (National Oceanic and Atm

spheric Administration, 1992). The mean annual 

perature is 56.6 o

F, with a mean monthly range of

30.7 o

F in January to 81.3 oF in July (Kansas Dep

ment of Agriculture and U.S. Department of

Agriculture, 1997, p. 8).

Topography in the Cheney Reservoir watersh

ranges from flat to gently sloping hills. Total topo

graphic relief is about 550 ft, with maximum loca

relief (within 1 mi) of about 50 ft.

Figure 1. Location of Cheney Reservoir watershed and nonagricultural soil-coring sites, south-central Kansas.
4 Historical Contributions of Phosphorus From Natural and Agricultural Sources and Implications for Stream Water Quality, Cheney Reser

Watershed, South-Central Kansas

The North Fork Ninnescah River Valley and the

surrounding plains are underlain by consolidated rocks

(mainly with thin layers of limestone, dolomite, siltstone, gypsum, and salt) of Permian age (230 to

280 million years old) covered by unconsolidated

stream-related (mainly sand and gravel) and windblown (mainly silt and clay) deposits of Pleistocene

age (less than 1.5 million years old) (Zeller, 1968).

The unconsolidated deposits are a source of water for

domestic supply, irrigation, and livestock and range in

thickness from little or no saturated thickness east of

Red Rock Creek (fig. 1) to more than 160 ft in the

northern part of Pratt County (Hansen, 1991).

Soils in the Cheney Reservoir watershed generally

are classified as clayey loam on the uplands to sand or

sandy loam on low-lying areas or where slopes are less

than about 3 percent. Many of the soils in the watershed are subject to erosion by wind and rainfall runoff

(Rockers and others, 1966).

Previous Investigations

Previous investigations of the Cheney Reservoir

watershed have described the extent of point-source

discharges within the watershed (Christensen and

Pope, 1997), the accumulation of phosphorus in bottom sediment of the reservoir (Pope, 1998), the transport of phosphorus (loads and yields) from selected

subwatershed areas (Pope and Milligan, 2000), and

historical sediment and phosphorus loading into

Cheney Reservoir (Mau, 2001). These investigations

have concluded (1) that point-source discharges are

not a major source of nutrients in the Cheney Reservoir watershed probably because of the small human

population, (2) that agricultural activities probably are

the dominant source of nutrient contamination of surface water in the watershed, (3) that phosphorus transport from the watershed has been increasing over time

probably because of increasing fertilizer use, (4) that

phosphorus transport is not uniform across the watershed and appears to be related to water yield, soil

types, and topography, and (5) that sediment deposition in Cheney Reservoir was less than reservoir

design-life specifications and that historical phosphorus transport to Cheney Reservoir was more than

determined previously.

Purpose and Scope

Soil phosphorus concentrations in the Ch

Reservoir watershed have been increasing at 

since the construction of the reservoir (Pope, 

However, the extent to which these concentra

have increased relative to natural concentratio

predominantly agricultural watershed is unkn

determine how or if agricultural activities may 

be modified or land-management practices im

mented to control phosphorus transport, it is fi

essary to define the extent to which these acti

have increased phosphorus transport to the re

Therefore, the purposes of this report are (1) t

the results of a study that examined soil phosp

concentrations from areas in and near Cheney 

voir watershed believed to be representative o

conditions, (2) to quantify the historical (196

phosphorus contribution to Cheney Reservoir 

natural and agricultural sources, and (3) to pr

estimates of stream-water-quality response th

have occurred under natural conditions of tota

phorus in soil.

Natural concentrations of total phosphoru

were compared to total phosphorus concentra

previously determined (Pope, 1998) in bottom

sediment samples from Cheney Reservoir. Be

the land-use characteristics of the watershed, 

rus concentrations in Cheney Reservoir botto

ment are considered agriculturally enriched.

Agricultural-enrichment factors were calculat

used to discuss implications for stream water 

under natural concentrations of phosphorus in 

METHODS

Soil-core samples were collected at 43 co

(fig. 1, table 1) in and near Cheney Reservoir 

shed on September 1–9, 1999. The sites were 

to represent soils with natural concentrations 

total phosphorus and to provide as wide a spa

distribution as possible in and near Cheney

Reservoir watershed.

Soil-Core Collection, Processing, and An

The North Fork Ninnescah River Basin h

in agricultural production since the middle of 

century. Although the widespread use of com
Method

Table 1. Location of soil-coring sites in and near Cheney Reservoir watershed, south-central Kansas

Coringsite

number

(fig.1) Coring-site name

Latitude

(degrees,

minutes,

seconds)

Longitude

(degrees,

minutes,

seconds)

1 Cemetery north of Haviland, Kansas 37o37'44" 99o

06'26"

2 Cemetery northeast of Wellsford, Kansas 37o37'31" 99o

00'53"

3 Cemetery 2 miles southwest of Byers, Kansas 37o45'42" 98o

54'11"

4 Cemetery 0.5 mile northwest of Byers, Kansas 37o47'46" 98o

52'34"

5 IOOF Cemetery north of Iuka, Kansas 37o44'04" 98o

43'52"

6 St. Paul Lutheran Cemetery 3 miles east of Iuka, Kansas 37o

43'34" 98o39'53"

7 Rose Valley Cemetery 9 miles north of Iuka, Kansas 37o51'41" 98o

43'44"

8 Cemetery 7 miles southeast of Saint John, Kansas 37o53'57" 98o

41'31"

9 Cemetery 4 miles southwest of Stafford, Kansas 37o53'50" 98o

39'00"

10 Cemetery 6 miles northwest of Preston, Kansas 37o50'22" 98o

38'05"

11 Friendship Cemetery 3 miles northwest of Preston, Kansas 37o46'37" 98o

37'12"

12 Haynesville Cemetery 2 miles north of Preston, Kansas 37o47'30" 98o

34'19"

13 Cemetery 3.5 miles southeast of Stafford, Kansas 37o55'30" 98o

33'16"

14 Abandoned farmstead 4 miles south of Zenith, Kansas 37o53'55" 98o

29'58"

15 Old Neda Cemetery 3 miles northwest of Turon, Kansas 37o50'12" 98o

29'26"

16 Pleasant Valley Geist Cemetery northeast of Preston, Kansas 37o46'34" 98o

29'48"

17 Turon Cemetery near Turon, Kansas 37o47'56" 98o

26'48"

18 Shelman Cemetery 4 miles northeast of Cunningham, Kansas 37o42'11" 98o

21'49"

19 Hayes Township Cemetery 4 miles southwest of Huntsville, Kansas 38o02'44" 98o

24'33"

20 Cemetery south of Huntsville, Kansas 38o02'35" 98o

20'05"

21 Pleasant View Cemetery northeast of Huntsville, Kansas 38o04'21" 98o

17'20"

22 Sylvia Cemetery east of Sylvia, Kansas 37o57'21" 98o

23'21"

23 Cemetery 2 miles west of Plevna, Kansas 37o

57'56" 98o21'44"

24 Plevna Cemetery west of Plevna, Kansas 37o58'10" 98o

19'00"

25 Glendale Cemetery 3.5 miles south of Sylvia, Kansas 37o54'15" 98o

23'54"

26 Lerado Cemetery near Lerado, Kansas 37o46'59" 98o

16'56"

27 Cemetery east of Langdon, Kansas 37o

51'12" 98o18'29"

28 Cemetery 3 miles northeast of Langdon, Kansas 37o52'38" 98o

16'15"

29 Cemetery 3 miles west of Arlington, Kansas 37o53'26" 98o

15'09"

30 Sego Cemetery 7 miles south of Arlington, Kansas 37o47'29" 98o

09'51"

31 Cemetery near Arlington, Kansas 37o54'20" 98o

10'08"

32 Abbyville Cemetery near Abbyville, Kansas 37o58'34" 98o

11'52"

33 Partridge Cemetery near Partridge, Kansas 37o57'46" 98o

05'13"

34 Cemetery northeast of Partridge, Kansas 37o

59'05" 98o03'42"

35 Cemetery 6 miles southeast of Arlington, Kansas 37o51'14" 98o

04'39"

36 KSU Experiment Station 4 miles southeast of Partridge, Kansas 37o55'37" 98o

01'29"

37 Pleasant View Cemetery 4 miles north of Castleton, Kansas 37o55'30" 97o

58'37"

38 Abandoned farmstead 2.5 miles southwest of Castleton, Kansas 37o

51'31" 98o00'49"

39 St. Agnes Cemetery near Castleton, Kansas 37o49'56" 97o

58'41"

40 Menonite Church cemetery near Pretty Prairie, Kansas 37o46'46" 97o

57'50"

41 Old cemetery northwest of Cheney Dam, Kansas 37o45'25" 97o

51'46"

42 Nichols Cemetery 3 miles north of Saint Joe, Kansas 37o

47'06" 97o44'09"

43 Old cemetery south of Cheney Dam, Kansas 37o42'16" 97o

48'58"
6 Historical Contributions of Phosphorus From Natural and Agricultural Sources and Implications for Stream Water Quality, Cheney Reser

Watershed, South-Central Kansas

fertilizers in crop production did not become commonplace until after the Second World War, pasturing of

livestock and manure applications to crop fields have

provided some phosphorus input to the watershed for

much of the agricultural history of the basin. This long

history of supplementing natural concentrations of

phosphorus in soil makes the identification of nonagriculturally affected soils difficult. However, cemeteries represent unique locations where soils have been

protected from agricultural activities for extended

periods.

Most of the cemeteries in and near Cheney Reservoir watershed have existed since at least the latter part

of the 19th century, and therefore, soils from these

locations may provide estimates of natural concentrations of soil phosphorus. These natural conditions,

however, could be compromised by the addition of

landscape fertilizers and by wind erosion from nearby

agricultural fields.

Forty of the 43 locations selected for this study

were in cemeteries (an example is shown in figure 2),

two were on abandoned farmsteads, and one was on

Kansas State University (KSU) land. Although several

of the selected cemeteries were not located in the

Cheney Reservoir watershed, it was believed that soil

conditions at these nearby cemeteries would be similar

to those soils within the watershed and that the positive benefits from a larger, spatially diverse data set

would offset possible negative effects of dissimilar

soils. Discussions with local residents and cemetery

caretakers indicated that landscape fertilizers are not

commonly, if ever, applied to cemetery soils in this

watershed. However, to avoid sampling soils that may

have been fertilized, cemeteries with unusually viable,

well-maintained lawns were not selected for this study.

The two abandoned farmsteads were included to

increase spatial definition in the coring-site distribution. Each farmstead had been abandoned for more

than 50 years, and the KSU land had no history of fertilizer applications.

Within each cemetery, sampling locations were

selected in the oldest part, as indicated by headstone

dates, or in areas as yet to receive burials. At each

sampling location (fig. 1), soil cores of two lengths

(2 and 8 in.) were collected using a 2-in. diameter soil

auger. Two soil-core lengths were collected to determine vertical variability in soil phosphorus concentrations and to represent the parts of the soil profile most

likely eroded and transported in runoff. The soil auger

was cleaned between sampling locations in a sequence

of nonphosphorus soap/water mix, tapwater rinse, and

deionized-water rinse. Each soil sample was s

through a

2-mm opening sieve (U.S. Standard No. 10) to 

plant debris, mechanically homogenized, and 

pled for analytical determinations. All soil sam

were analyzed for total phosphorus at the USG

National Water-Quality Laboratory in Denver

rado, according to methods described in Fishm

(1993). Soil particle size was determined for t

centage of sand and silt and (or) clay (percent

greater than or less than 0.062 mm in diamete

tively) at the USGS sediment analysis laborat

Iowa City, Iowa, according to methods descri

Guy (1969).

Quality Control

Soil-core samples for analysis of total pho

and soil particle size were collected to determ

potential within-site variability (variability am

multiple sampling locations within a coring si

Information on within-site variability is usefu

uating the representativeness of samples colle

single location within a coring site. Large wit

variability would complicate the evaluation of 

distribution and estimation of mean soil phosp

concentrations in nonagricultural areas of the 

shed. Additional soil-core samples were analy

total soil phosphorus to determine variability

associated with a combination of sample colle

processing, and analytical procedures.

Figure 2. Soil-coring site 27, cemetery east of Langdon

Location of coring site shown in figure 1.
Method

Sequential Replicate Samples

Within-site variability was evaluated through the

collection and analysis of primary and two sequential

replicate soil-core samples (table 2) collected at coring

sites 13, 20, 26, 27, and 40 (fig. 1). Sequential replicate soil-core samples were collected from different

locations within the coring sites (cemeteries). All coring locations in cemeteries were either in the oldest

developed parts or in unused areas (areas as yet to

receive burials). Variation among the three resulting

soil phosphorus concentrations and percentage of particle size less than 0.062 mm (silt and clay) at each

coring location and depth was evaluated with a technique used by Dufour and others (1981) that

expressed variation as a percentage of the mean with

the equation:

, (1)

where

s is the standard deviation,

n is the number of replicate analyses, and

x is the mean of replicate values from the

analyses.

Within-site variability in soil phosphorus

concentrations ranged from 2.2 percent of the mean in

the 2-in. core samples from coring site 20 (fig. 1) to

31 percent of the mean in the 2-in. core samples from

coring site 13. The average within-site variability was

16 percent of the mean for the 2-in. core samples and

11 percent of the mean for the 8-in. core samples from

all five coring sites. The average within-site variability

for both coring depths (2 and 8 in.) at all five coring

sites with sequential replicate core samples (table 2)

was 13 percent of the mean.

Within-site variability in percentage of soil core as

silt and (or) clay (particle size less than 0.062 mm in

diameter) was not as large as that for soil phosphorus

concentrations. Variability in percentage of silt and

(or) clay ranged from 0.2 percent of the mean in the

8 in. core samples from coring site 26 to 25 percent of

the mean in the 2-in. core samples from coring site 27.

The average within-site variability was 9.8 percent of

the mean for the 2-in. core samples and 5.4 percent of

the mean for the 8-in. core samples from all five coring

sites. The average within-site variability for both coring depths at all five coring sites with sequential replicate core samples was 7.6 percent of the mean.

Evaluation of within-site variability for soil

phosphorus and percentage of silt- and (or) clay-size

particles produced two conclusions. First, the 2-in

core samples had greater within-site variability th

the 8-in. core samples. This greater variability in 

shorter core samples may be related to natural var

ability in organically bound phosphorus near the 

face of the soil profile. This near-surface variabilit

turn, probably is the result of variation in vegetati

cover (organic production) within the coring site (

etery). The greater particle-size variability in the 

core samples probably is the result of preferential 

ing and distribution of certain soil particles sizes 

result from water and windblown processes. Clos

associated with these erosional processes are vari

tions in microenvironments that either may promo

mitigate the movement, distribution, and segregat

of certain soil particle sizes within a coring site.

Microenvironmental characteristics include type a

percentage of vegetative cover, land slope, precip

tion, orientation to prevailing wind direction, and

proximity to structures, obstacles, or natural featu

that affect the potential for water or windblown er

sion. The variability in these surface characteristi

has less effect (smaller variability) on longer (8-in

core samples because of the larger mass of these 

ples and their ability to dilute these near-surface

effects. Second, soil phosphorus concentrations a

percentage of silt- and (or) clay-size particles from 

analysis of sequential replicate samples indicate t

although within-site variability may be large at so

coring sites, the average soil phosphorus concentr

tions and percentage of silt- and (or) clay-size part

from the entire network of coring sites would be r

sonably represented by single sampling locations

within sampling sites.

Split Replicate Samples

Variability in total phosphorus concentrations 

soil cores resulting from a combination of sample 

lection, processing, and analytical procedures wa

evaluated with split replicate core samples (table 

collected at coring sites 9, 18, 28, 29, and 34 (fig. 

Split replicate samples of both 2- and 8-in. soil-co

samples were prepared by mechanically homogen

ing each sample at the collection site and splitting 

homogenized mass into two separate samples eac

which was independently analyzed for total phosp

rus. Variability between split replicate analyses

was calculated as a percentage of the mean using

equation 1.

variation s/( n )

x ---------------- ⋅ 100     =
8 Historical Contributions of Phosphorus From Natural and Agricultural Sources and Implications for Stream Water Quality, Cheney Reser

Watershed, South-Central Kansas

Variability in total phosphorus concentrations in

split replicate soil-core samples ranged from 0.7 percent of the mean in the 2-in. core samples from coring

site 18 to 46 percent of the mean in the 2-in. core samples from coring site 9. The average variability was

14 percent of the mean for the 2-in. split replicate samples and 7.6 percent of the mean for the 8-in. split replicate samples. The average variability for all split

replicate samples from both coring depths at all five

coring sites was 11 percent. With the exception of the

unusually large 46 percent of the mean from coring

site 9, variability between all other split replicate samples was less than 17 percent of the mean. Excluding

the 46 percent of the mean from the calculation of

average variability reduced average variability for both

coring depths at all five coring sites from 11 to 6.9 percent of the mean. Generally, therefore, results from the

analyses of split replicate soil-core samples presented

in table 2 indicate that sample collection, processing,

and analysis of soil-core samples for total phosphorus were adequate and not a substantial source of

variability.

HISTORICAL CONTRIBUTIONS OF PHOSPHORUS

Estimates of natural concentrations of total phosphorus in soil were made from the analyses of soilcore samples collected from 43 nonagricultural sites in

and near Cheney Reservoir watershed. These natural

concentrations were compared to total phosphorus

concentrations in Cheney Reservoir bottom sediment

to estimate the extent to which the agricultural distribution of phosphorus has enriched soil phosphorus

concentrations in the watershed. A phosphorusenrichment factor was calculated and used to estimate

mean total phosphorus concentrations in water at

selected streamflow sampling sites in the Cheney

Reservoir watershed that may have occurred under

conditions of natural concentrations of soil phosphorus. Before results from coring sites with qualitycontrol samples (table 2) were used in calculations,

statistical analyses, or graphical presentations, primary

and replicate analyses were averaged.

Natural Soil Concentrations

Natural concentrations of total phosphorus in

soil in and near Cheney Reservoir watershed were

estimated from soil-core samples collected from

43 nonagricultural sites (fig. 1) and analyzed 

phosphorus (table 2). Generally, total phosph

centrations were larger and had a wider range 

2-in. soil-core samples than in the 8-in. core s

(fig. 3). Total phosphorus concentrations rang

74 to 539 mg/kg with a median concentration 

245 mg/kg in 2-in. soil-core samples compare

range of 50 to 409 mg/kg with a median conc

of 166 mg/kg in 8-in. soil-core samples. In co

there was little difference in soil particle-size

composition (percentage of particle size less 

0.062 mm) in either ranges or median values 

the 2-in. and 8-in. soil-core samples. Soil par

less than 0.062 mm ranged from 0.4 to 88 per

both 2-in. and 8-in. soil-core samples with me

ues of 44 and 41 percent, respectively. Some 

potential reasons for differences in total phos

concentrations between the 2-in. and 8-in. soi

samples were discussed previously in the “Qu

Control” section of this report.

A previous investigation of total phospho

transport in streams of the Cheney Reservoir 

shed in 1997–98 (Pope and Milligan, 2000) id

an increasing trend in total phosphorus yields 

west-to-east direction. Phosphorus yields rang

about 0.13 lb/acre in the western part of the w

to about 0.37 lb/acre in the eastern part. To de

if this trend is partly the result of natural varia

total phosphorus concentrations in soil, a plot 

spatial distribution of total phosphorus conce

(fig. 4) in core samples from the 43 nonagricu

coring sites (fig. 1) sampled during the Septem

1999 investigation was examined. Although n

nitely evident in figure 4, it appeared that the 

part of the watershed had the larger natural co

tions of total phosphorus in soil. To verify thi

vation, a statistical comparison was made bet

coring sites located in the western half of the 

shed (coring sites 1–19, 22, 23, 25, fig. 1) with 

the eastern half (coring sites 20, 21, 24, 26–4

Median total phosphorus concentrations i

and 8-in core samples were 36 and 47 percen

respectively, in samples collected from the ea

coring sites than in samples collected from th

western coring sites. These percentages were 

cally significant at least at the 0.07 level of si

cance (p-value 0.07 or less) as determined by 

Wilcoxon rank-sum test. Part of the west-to-e

increase in phosphorus concentrations may be 

ated with a corresponding increase in the perc
Historical Contributions of Phosphoru

Coringsite

number

(fig. 1)

Depth of

soil core

(inches) Type of sample

Total

phosphorus

concentration

(mg/kg)

Soil particle

size less than

0.062 mm

(percent)

1 2 Primary 202 31.5

8 do. 144 35.2

2 2 do. 263 49.1

8 do. 215 50.7

3 2 do. 262 20.2

8 do. 87.5 19.3

4 2 do. 110 28.6

8 do. 94.7 24.7

5 2 do. 99.1 48.7

8 do. 129 46.6

6 2 do. 157 28.4

8 do. 105 19.5

7 2 do. 200 34.0

8 do. 79.7 34.4

8 2 do. 167 44.8

8 do. 134 38.0

9 2 do. 146 18.6

8 do. 65.5 26.2

2 Split replicate 54.6 --

8 do. 70.0 --

10 2 Primary 219 25.6

8 do. 158 22.4

11 2 do. 121 40.1

8 do. 49.8 34.1

12 2 do. 341 54.2

8 do. 205 42.7

13 2 do. 195 50.0

8 do. 60.6 48.9

2 Sequential replicate 75.6 53.9

8 do. 74.0 50.0

2 do. 93.1 57.5

8 do. 78.6 60.6

14 2 Primary 323 21.3

8 do. 409 2.8

15 2 do. 293 42.8

8 do. 227 38.5

16 2 do. 355 48.0

8 do. 243 35.5

17 2 do. 325 49.6

8 do. 187 42.9

18 2 do. 204 52.6

8 do. 106 .4

2 Split replicate 207 --

8 do. 118 --

19 2 Primary 186 13.8

8 do. 140 17.7

20 2 do. 287 35.7

8 do. 216 31.9

2 Sequential replicate 266 36.1

20 8 Sequential replicate 207 3

2 do. 279 4

8 do. 274 3

21 2 Primary 325 4

8 do. 282 5

22 2 do. 395 6

8 do. 322 5

23 2 do. 326 7

8 do. 271 7

24 2 do. 199 2

8 do. 103 2

25 2 do. 111 1

8 do. 114 1

26 2 do. 302 3

8 do. 132 3

2 Sequential replicate 213 3

8 do. 99.0 3

2 do. 115 2

8 do. 141 3

27 2 Primary 268 4

8 do. 214 4

2 Sequential replicate 163 8

8 do. 226 4

2 do. 231 3

8 do. 202 4

28 2 Primary 263 3

8 do. 226 4

2 Split replicate 242 

8 do. 183 

29 2 Primary 211 3

8 do. 145 3

2 Split replicate 202 

8 do. 167 

30 2 Primary 472 5

8 do. 360 5

31 2 do. 344 4

8 do. 186 4

32 2 do. 539 5

8 do. 129 6

33 2 do. 359 5

8 do. 137 5

34 2 do. 86.8 3

8 do. 71.4 4

2 Split replicate 61.9 

8 do. 90.4 3

35 2 Primary 294 

8 do. 201 

Coringsite

number

(fig. 1)

Depth of

soil core

(inches) Type of sample

Total

phosphorus

concentration

(mg/kg)

Soil pa

size les

0.062 

(perc

Table 2. Results of analyses of total phosphorus concentrations and particle-size determinations for selected soil cores in and near C

Reservoir watershed, south-central Kansas, September 1999

[mg/kg, milligrams per kilogram; mm, millimeter; --, not determined]
10 Historical Contributions of Phosphorus From Natural and Agricultural Sources and Implications for Stream Water Quality, Cheney Reser

Watershed, South-Central Kansas

of silt- and (or) clay-size particles (particles less than

0.062 mm in diameter) in samples from the eastern

coring sites (fig. 5). Median percentages of silt- and

(or) clay-size particles were 17 and 34 percent larger

in 2-in. and 8-in. soil-core samples, respectively, from

the eastern coring sites than in samples from the western coring sites. The determination that soils are sandier in the western part of the watershed is substantiated

by Rockers and others (1966), Horsch and others

(1968), and Dodge and others (1978). Although the

west-to-east variability in natural soil phosphorus concentrations in the Cheney Reservoir watershed has a

part in explaining the previously determined west-toeast trend in total phosphorus yield, other factors such

as variability in land-use and land-management

characteristics, precipitation and water yield, and

topography may contribute substantially more to the

185-percent increase in total phosphorus yields from

west to east in the Cheney Reservoir watershed.

Agricultural Enrichment

To evaluate the effects of agriculture on soil phosphorus concentrations in the Cheney Reservoir

watershed, concentrations of total phosphorus 

from nonagricultural areas were compared to 

phosphorus concentrations in Cheney Reservo

tom sediment. A previous examination (Pope, 

Cheney Reservoir bottom sediment indicated 

phosphorus transport from the watershed has 

increasing since at least construction of the re

probably as a result of agricultural activities, a

dent in bottom-sediment cores from Cheney R

(fig. 6) and that a direct relationship exists bet

total phosphorus concentrations and percentag

and (or) clay-size particles in bottom sedimen

This relation of particle size to total phosphor

has been identified by other researchers (Keul

1982; Dong and others, 1983; Viner, 1984). Th

variability in total phosphorus concentrations 

samples of soil or sediment with varying parti

composition may reflect only the variability w

cle size and not that associated with agricultu

make comparisons of this type, all samples fir

be normalized relative to particle-size compos

This normalization process also compensates 

preferential transport of silt- and (or) clay-siz

cles in runoff from agricultural fields (Rhoton 

ers, 1979; Dean, 1983). The preferential trans

silt and clay particles with their potentially lar

phosphorus concentrations relative to the sour

naturally would tend to enrich deposited mate

Cheney Reservoir.

Particle-Size Weighted Concentrations

Soil samples collected from nonagricultur

tions (fig. 1) for this study and previously coll

bottom sediment from Cheney Reservoir (Pop

were normalized (weighted) relative to the pe

of the silt and (or) clay fraction of the particle

composition. Particle-size weighted (hereinaf

referred to as weighted) mean total phosphoru

centrations for both the 2-in. and 8-in. soil-co

samples from nonagricultural locations in the

Cheney Reservoir watershed were calculated 

the equation:

where

weighted mean total phosphorus concentration

1

43

∑

1

4

∑

= --------

Table 2. Results of analyses of total phosphorus concentrations

and particle-size determinations for selected soil cores in and near

Cheney Reservoir watershed, south-central Kansas, September

1999—Continued

36 2 Primary 373 74.9

8 do. 339 71.1

37 2 do. 245 29.9

8 do. 250 27.8

38 2 do. 241 7.9

8 do. 166 26.9

39 2 do. 218 53.3

8 do. 253 49.7

40 2 do. 257 48.6

8 do. 94.0 31.6

2 Sequential replicate 288 50.0

8 do. 223 47.1

2 do. 304 47.5

8 do. 239 48.6

41 2 Primary 277 65.5

8 do. 255 66.4

42 2 do. 394 87.6

8 do. 317 87.6

43 2 do. 145 .4

8 do. 160 53.0

Coringsite

number

(fig. 1)

Depth of

soil core

(inches) Type of sample

Total

phosphorus

concentration

(mg/kg)

Soil particle

size less than

0.062 mm

(percent)
Historical Contributions of Phosphorus 

0

Total

phosphorus

Particle

size

Particle

size

Total

phosphorus

100

200

300

Total phosphorus concentration, in milligrams per kilogram

400

500

600

2–inch 8–inch

0

10

20

30

40

50

Percentage of particle size less than 0.062 millimeter in diameter

60

70

80

90

100

Soil cores

Median

concentration

Median

concentration

Median particle

size

Median particle

size

C is the concentration of total phosphorus in

2- or 8-in. soil-core samples, and

P is the percentage of the silt and (or) clay

particle-size fraction in 2- or 8-in. soilcore samples.

A similar technique was used to calculate weighted

mean total phosphorus concentrations in Cheney Reservoir sediment from results of bottom-sediment core

analysis as presented in Pope (1998).

The weighted mean total phosphorus concentration in Cheney Reservoir bottom sediment was substantially larger than weighted mean total phosphorus

concentrations in either the 2-in. (1.8 times larger) or

8-in. (2.6 times larger) soil-core samples from nonagricultural areas in and near Cheney Reservoir

watershed (fig. 8). The sediment in Cheney Reservoir

was derived almost exclusively from lands used for

agricultural purposes (crops and livestock); therefore,

the agricultural enrichment of phosphorus in this sediment as evident from figure 8 is prob

the result of agricultural use of comm

cial phosphorus fertilizers and the sur

application of livestock manure.

The differences between weighte

mean total phosphorus concentration

the two soil-core depths (fig. 8) proba

reflect a natural buildup near the surf

of the core profile of organic phospho

from plant or microbial origins or pos

windblown deposits from nearby agri

tural land. Because of a much smalle

sample mass associated with the shor

soil core, this buildup would have a

greater effect on mean total phosphor

concentrations (produce a larger mea

concentration) in a short (2-in.) core 

ple than it would on the larger mass i

longer (8-in.) core sample.

Wind-transport processes also mi

be a reason for the larger weighted m

total phosphorus concentration in the

shorter soil cores. Nearly all coring s

shown in figure 1 are surrounded by o

close proximity to agricultural lands

where phosphorus fertilizers are used

South-central Kansas is subject to str

winds during times when cropland is 

tively bare of vegetation. These wind

have the potential for erosion of crop

with chemical transport to and depos

on nonagricultural areas. If phosphorus enrichme

resulting from wind transport is substantial, then 

differences between Cheney Reservoir bottom sed

ment and the nonagricultural soil samples could b

even greater than that indicated in figure 8. Unfor

nately, the extent, if any, of phosphorus enrichme

resulting from wind transport is not known and pr

bly cannot be quantified.

The 2.6 enrichment factor calculated using 8-

soil-core samples collected at the 43 nonagricultu

sites probably is the more representative factor fo

Cheney Reservoir watershed because

(1) results from 8-in. soil cores would minimize t

effects (relative to results from 2-in. soil cores) of

phosphorus enrichment by wind transport from ne

agricultural fields, and (2) results from 8-in. soil c

probably are more indicative of total phosphorus a

ability from land tilled for crop production, which 

substantial land use in the Cheney Reservoir wate

Figure 3. Comparison of total phosphorus concentrations and particle sizes less

than 0.062 millimeter in diameter between 2-inch and 8-inch soil-core samples

collected from 43 nonagricultural sites in and near Cheney Reservoir watershed,

September 1999.
12 Historical Contributions of Phosphorus From Natural and Agricultural Sources and Implications for Stream Water Quality, Cheney Reser

Watershed, South-Central Kansas

Arkansas R

Ch

 Reser eney

voir

Noncontributing

drainage area

Contributing

drainage area

99° 45' 30' 15' 98° 

38°

37°45'

Reno

County

Kingman County

Stafford County

Edwards

County

Kiowa

County

Pawnee County

Pratt County

Silver Creek

43

40 

41

39

38

37

36

22 33

27

25

34

31 29 28

24 32

21

20 19

35

30 26

18

16

12

10

9 8

7

11

6 5

3

4

2

1

15

14

13

17

Boundary of Cheney

Reservoir watershed

200

0

400

600

145

200

0

400

600

373

200

0

400

600

74.4 

200

0

400

600

359

200

0

400

600

344

200

0

400

600

800

539

200

0

400

600

277

200

0

400

600

283

200

0

400

600

218

200

0

400

600

241

200

0

400

600

294

200

0

400

600

472

200

0

400

600

252

200

0

400

600

210

200

0

400

600

221

200

0

400

600

200

206 

0

400

600

355

200

0

400

600

341

200

0

400

600

121

200

0

400

600

157

200

0

400

600

99.1

200

0

400

600

202

200

0

400

600

263

200

0

400

600

325

206

200

0

400

600

200

186

0

400

600

326

200

0

400

600

395

200

0

400

600

200

121

0

400

600

100

200

0

400

600

200

200

0

400

600

110

200

0

400

600

262

200

0

400

600

219 200

0

400

600

167

200

400

600

323

200

0

400

600

277

200

0

400

600

325 200

0

400

600

199

200

 0

400

600

111

200

0

400

600

293

 A. 2-inch soil cores

B. 8-inch soil cores

0

Arkansas R

0 5 10 

0 5 10 15 20 KILOMETE

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°00'

Mean concentration of total

 phosphorus, in milligrams

 per kilogram

Coring site and number

EXPLANATION

Cheney

 Reservoir

Noncontributing

drainage area

Contributing

drainage area

99° 45' 30' 15' 98° 

38°

37°45'

Reno

County

Kingman County

Stafford County

Edwards

County

Kiowa

County

Pawnee County

Pratt County

Silver Creek

43

40

41

39

38

37

36

22 33

27

25

34

31 29 28

32 24

21

20 19

35

30 26

18

16

12

10

9 8

7

11

6

6

5

3

4

2 1

15

14

13

Boundary of Cheney

Reservoir watershed

200

0

400

600

160

317

200

0

400

600

339

200

0

400

600

80.9

200

0

400

600

137

200

0

400

600

186

0

400

600

129

200

0

400

600

255

200

0

400

600

185

200

0

400

600

253

200

0

400

600

166

200

0

400

600

201

200

0

400

600

360

200

0

400

600

360

200

0

400

600

204

200

0

400

600

200

124

0

400

600

214

200

0

400

600

112

200

0

400

600

243

200

0

400

600

200

205

0

400

600

49.8

200

0

400

600

105

200

0

400

600

129

200

0

400

600

144

200

0

400

600

215

200

0

400

600

187

156

200

0

400

600

140

200

0

400

600

271

200

0

400

600

322

200

0

400

600

71.1

200

0

400

600

67.8

200

0

400

600

79.7

200

0

400

600

94.7

200

0

400

600

87.5

200

0

400

600

158 200

0

400

600

134

200

0

400

600

409

200

0

400

600

232

200

0

400

600

282 200

0

400

600

103

200

0

400

600

114

200

0

400

600

227

17

North

Fork Ninnescah River

200

0

400

600

North

Fork Ninnescah River

200

0

400

600

Western half of basin Easte

of b

Western half of basin Easte

of b

23

23

Figure 4. Distribution of total phosphorus concentrations in (A) 2-inch and (B) 8-inch soil-core samples at 43 nonagricultural 

sites in and near Cheney Reservoir watershed, September 1999.
Historical Contributions of Phosphorus 

Arkansas River

Arkansas River

Ch

 Res eney

ervoir

Noncontributing

drainage area

Contributing

drainage area

99° 45' 30' 15' 98° 97°

38°

37°45'

Reno

County

Har

Cou

Kingman County

Stafford County

Edwards

County

Kiowa

County

Pawnee County

Pratt County

Sed

C

N F Ninnescah R

Silver Creek

0 5 10 15 

0 5 10 15 20 KILOMETERS

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°00'

 Coring site and number

EXPLANATION

Cheney Reservoir

Noncontributing

drainage area

Contributing

drainage area

99° 45' 30' 15' 98° 97°

38°

37°45'

Reno

County

Har

Cou

Kingman County

Stafford County

Edwards

County

Kiowa

County

Pawnee County

Pratt County

Sed

C

N F Ninnescah R

Silver Creek

43

40

41

39

38

37 36

33 22

27

25

34

29 31

28

24 32

21 19 20

35

30 26

18

17

16

12

10

8 9

7

11

6 5

3

4

1 2

15

14

13

43

40 

41

39

38

37

36

33 22

27

25

34

31 29 28

24 32

21

19 20

35

30 26

18

17

16

12

10

9 8

7

11

11

5 6

3

4

1 2

15

14

13

Boundary of Cheney

Reservoir watershed

Boundary of Cheney

Reservoir watershed

Particle-size distribution, in percent (%)

Silt and (or) clay (less than 0.062 millimeter 

 in diameter)

 

Sand (greater than 0.062 millimeter 

 in diameter)

.4%

99.6% 65.5%

53.3%

7.9%

48.7%

34.5%

46.7%

92.1%

51.3%

44.7% 55.3%

56.2%

61.6% 38.4%

43.8% 44.5% 55.5%

52.6%

50.4% 49.6%

52.0% 48.0% 47.4%

45.8% 54.2%

35.1%

18.0%

42.8% 57.2%

64.9%

82.0%

40.1%

28.4%

48.7%

50.9% 49.1%

51.3% 71.6% 59.9%

25.6%

74.4%

31.5%

20.2%

68.5%

79.8%

28.6%

71.4%

34.0%

66.0%

55.2% 44.8%

81.4%

18.6%

46.2% 53.8% 21.3%

78.7%

28.8%

71.2%

65.8%

34.2%

13.8%

86.2%

39.2%

51.2%

60.8%

28.9%

71.1%

48.8%

49.4% 50.6%

55.6% 44.4%

54.7% 45.3%

87.6%

70.1% 12.4%

29.9%

74.9%

25.1%

60.2%39.8%

A. 2-inch soil cores

B. 8-inch soil cores

67.3%

32.7%

53.0%

66.4% 33.6%

57.6% 42.4%

47.0%

50.3%

73.1%

49.0%

45.8% 58.9%

68.6%

56.4%

31.4%

43.6%

41.1%

54.2%

51.0%

26.9%

49.7%

99.6%

57.1%

64.5%

57.3%

65.9%

80.5% 53.4%

49.3%

64.8%

35.2%

80.7%

19.3%

50.7%

46.6%

19.5%

34.1%

42.7%

35.5%

64.5%

35.5%

42.9%

0.4%

34.1%

65.9%

85.6% 61.5%

77.6%

22.4%

38.5%

14.4%

75.3%

65.6%

34.4%

24.7%

62.0%

38.0%

73.8%

26.2%

53.2%

2.8%

97.2%

46.8%

26.1%

59.8% 73.9%

17.7% 49.9% 50.1%

32.9% 33.2%

66.8% 67.1%

71.0% 53.5%

44.8% 55.2%

60.5%

28.9%

72.2%

27.8%

12.4%

87.6%

71.1%

46.5%

29.0%

82.3% 40.2%

39.5%

Western half of basin Eastern half of basin

Western half of basin Eastern half of basin

North

Fork Ninnescah River

North

Fork Ninnescah River

23

23

Figure 5. Distribution of soil particle size in (A) 2-inch and (B) 8-inch soil-core samples at 43 nonagricultural coring sites in and ne

Cheney Reservoir watershed, September 1999.
14 Historical Contributions of Phosphorus From Natural and Agricultural Sources and Implications for Stream Water Quality, Cheney Reser

Watershed, South-Central Kansas

shed. Most tilled (plowe

tivated) land probably is 

to at least an 8-in. depth a

land most susceptible to 

and transport of phospho

Phosphorus Mass

The calculation of an 

tural-enrichment factor f

phosphorus can have wat

quality implications whe

factor is used to quantify 

cal contributions of phos

from natural and agricult

sources and to estimate t

ability of stream-water-q

goals under natural conc

tions of total phosphorus 

Therefore, the validity of 

calculated enrichment fa

critical. To verify the 2.6 

tural-enrichment factor f

phosphorus previously d

mined, the factor also wa

lated on the basis of info

presented in a recently pu

report quantifying sedim

and phosphorus loading 

Cheney Reservoir (Mau, 

Mau (2001) estimate

total mass of sediment (1

lion lb) and mass of phos

(7.7 million lb) associate

that sediment in Cheney 

voir. These masses were 

mated on the basis of bat

surveys of the reservoir co

in 1964 and 1998 and on 

density and phosphorus c

trations determined in bo

sediment samples collect

(1997–98) from a networ

sedimentcoring sites within the re

For the purpose of this re

these two masses were u

calculate a mean total ph

concentration (500 mg/k

Cheney

Reservoir bottom sedime

Figure 6. Relation between total phosphorus concentrations in bottom-sediment core

samples and normalized depth of samples from selected coring sites in Cheney

Reservoir, 1965–97 (modified from Pope, 1998, fig. 10; r is correlation coefficient).

Sediment cores were collected August 1997.

Figure 7. Relation between mean percentage of bottom-sediment particles less than

0.062 millimeter in diameter (silt and clay) and mean concentrations of total phosphorus in

bottom-sediment samples from 10 coring sites in Cheney Reservoir, August 1997 (modified

from Pope, 1998).

Bottom-sediment coring site in Cheney Reservoir

Total phosphorus concentration, in milligrams per kilogram

0

0.2

0.4

0.6

0.8

1.0

Normalized depth of samples, dimensionless

Site P1

500 700 800 600

r = 0.78

p-value = 0.07

Site P4

400 500 600

r = 0.95

p-value = less 

 than 0.001

Site P10 

0 100 200

r = 0.71

p-value = 0.07 1997

1997

1997

1965 1965 1965

0

100

200

300

400

500

600

700

0 10 20 30 40 50 60 70 80 90 100

Mean percentage of bottom-sediment particles

less than 0.062 millimeter in diameter 

Mean concentration of total phoshorus,

in milligrams per kilogram

r = 0.96

p-value = less than 0.001

 Data point

y = 5.16x + 69.8
Historical Contributions of Phosphorus 

506

198

275

0

100

200

300

400

500

600

2-inch 8-inch Cheney Reservoi

bottom-sediment

samples

Soil cores

Weighted mean total phosphorus concentration,

in milligrams per kilogram

(2001) reported a sedimentvolume weighted mean phosphorus concentration of 498

mg/kg. Because the

500 mg/kg mean concentration was calculated from the

ratio of total phosphorus

mass to total sediment mass

in the reservoir, variability in

particle size (as previously

discussed) was not an issue.

A direct comparison between

mean total phosphorus concentration in reservoir bottom

sediment and mean

concentration in nonagricultural soils could be made.

An agriculturalenrichment factor for total

phosphorus was calculated

using the mean total phosphorus concentration in

Cheney Reservoir bottom

sediment (500 mg/kg) and the

mean total phosphorus concentration (184 mg/kg) in

8-in. soil-core samples collected from 43 nonagricultural coring sites (fig. 1, table 1) used in the study

described in this report. The mean total phosphorus

concentration in 8-in. soil-core samples was calculated

from data presented in table 2 after first averaging, by

coring site, results of primary and replicate sample

analyses. The agricultural-enrichment factor for total

phosphorus in the Cheney Reservoir watershed was

calculated by dividing the mean concentration in

Cheney Reservoir bottom sediment (500 mg/kg) by

the mean concentration (184 mg/kg) in 8-in. soil-core

samples. The result of this calculation (2.7) produced

an agricultural-enrichment factor for total phosphorus

that was essentially the same as the 2.6 factor calculated from the results of the study described in this

report. In summary, the information presented by Mau

(2001) and the agricultural-enrichment factor calculated from that information provide supporting evidence for the validity of the particle-size weighted

approach and methodology used in the study described

in this report.

Both the 2.6 and 2.7 calculated enrichment factors

for total phosphorus are conservative estimates of the

effect of agricultural inputs of phosphorus in the

Cheney Reservoir watershed because the factors do

not account for (1) the phosphorus mass dissolved 

suspended in the water at the time of collection o

tom-sediment samples, and (2) the mass of phosp

rus historically discharged from the reservoir. The

masses, however, can be estimated, added to the t

mass of phosphorus in bottom sediment in Chene

Reservoir as determined by Mau (2001), and subs

quently, used in the calculation of a historical me

agricultural-enrichment factor.

The phosphorus mass (in pounds) dissolved o

suspended in the water at the time of collection o

tom-sediment samples (1997–98) was estimated f

a calculation of the storage capacity of Cheney R

voir at the conservation-pool elevation in 1998,

154,000 acre-ft (Putnam and others, 2000; Mau,

2001), multiplied by the mean concentration of to

phosphorus, 0.10 mg/L (Milligan and Pope, 2001

water in storage and by a unit conversion factor

(2.720). The mean concentration of total phospho

in water in storage was estimated as the mean con

tration in water discharged from Cheney Reservo

during the course of the Cheney Reservoir waters

study (1997–2000). Estimated total phosphorus m

in Cheney Reservoir water at the time of collectio

bottom-sediment samples was 42,000 lb.

Figure 8. Comparison of particle-size weighted mean total phosphorus concentrations in soil

samples from 43 nonagricultural sites in and near Cheney Reservoir watershed, September 1

and in bottom-sediment samples from Cheney Reservoir, August 1997.
16 Historical Contributions of Phosphorus From Natural and Agricultural Sources and Implications for Stream Water Quality, Cheney Reser

Watershed, South-Central Kansas

The phosphorus mass historically discharged from

Cheney Reservoir was estimated as a combination of

mass actually discharged (into the North Fork Ninnescah River) and mass as part of the volume of water

withdrawn by the city of Wichita for municipal supply.

The phosphorus mass (in pounds) actually discharged

from the reservoir was estimated from a calculation of

volume of water discharged from the reservoir October 1, 1965, through September 30, 1998 (2.96 million

acre-ft; Mau, 2001), multiplied by an estimated

historical mean concentration of total phosphorus

(0.07 mg/L) and by a unit conversion factor (2.720).

The historical mean concentration of total phosphorus

was estimated on the basis of the fact that the mean

concentration of total phosphorus in reservoir discharge during the course of the Cheney Reservoir

watershed study (1997–2000) was 0.10 mg/L (Milligan and Pope, 2001) and that total phosphorus transport from the watershed has been increasing with time

(Pope, 1998; Mau, 2001). Therefore, the 0.10-mg/L

mean concentration calculated for reservoir discharge

(1997–2000) probably reflects a historical maximum

mean concentration. No comprehensive historical

(1965–98) database exists for concentrations of

total phosphorus in water discharged or withdrawn

from Cheney Reservoir. Consequently, the estimated

0.07-mg/L concentration of total phosphorus represents a compromise between what is believed to be an

upper limit (0.10 mg/L) in mean total phosphorus concentration and an estimated lower limit (0.05 mg/L)

determined on the basis of best professional judgement. Estimated total phosphorus mass actually discharged from Cheney Reservoir (1965–98) was

calculated at 564,000 lb.

The phosphorus mass (in pounds) as part of the

volume of water withdrawn by the city of Wichita for

municipal supply was estimated from a calculation of

volume of water withdrawn from the reservoir October

1, 1965, through September 30, 1998 (694,000 acre-ft;

Mau, 2001), multiplied by an estimated historical

mean concentration of total phosphorus (0.07 mg/L)

and by a unit conversion factor (2.720). Estimated

total phosphorus mass as part of the volume of water

withdrawn for municipal supply was calculated at

132,000 lb.

Mau (2001) calculated the total mass of phosphorus in bottom sediment of Cheney Reservoir at

7.7 million lb. The total mass of phosphorus historically transported into Cheney Reservoir from the

watershed is a summation of phosphorus mass in

bottom sediment (7.7 million lb), in the reserv

water at the time of bottom-sediment sample 

tion (42,000 lb), in water discharged from the 

(564,000 lb), and in water withdrawn from th

voir (132,000 lb). Total phosphorus mass his

transported (1965–98) into Cheney Reservoir 

8.4 million lb.

A historical mean agricultural-enrichmen

for total phosphorus can be calculated as the 

the historical phosphorus mass, expressed as 

concentration of total phosphorus in sedimen

ported into Cheney Reservoir, to (divided by) 

mean concentration of total phosphorus in so

nonagricultural areas of the Cheney Reservoi

shed. The historical mean total phosphorus c

tion in sediment transported into Cheney Res

(542 mg/kg) was calculated as total phosphor

divided by total sediment mass. Total phosph

mass (8.4 million lb) was previously calculate

(2001) calculated the total sediment mass dep

Cheney Reservoir during 1965–98 (15.4 billio

however, this mass did not include an estimat

sediment discharged from the reservoir.

Sediment mass discharged from the reser

(actually discharged and withdrawn) was calc

using the same method and water volumes as 

the calculation of phosphorus mass except a h

mean concentration of sediment in water disc

from Cheney Reservoir was estimated on the b

mean concentration of total suspended solids 

(9.8 mg/L) discharged from the reservoir duri

1997–2000 (Milligan and Pope, 2001). Total 

mass discharged from the reservoir during 19

was calculated at 97.0 million lb. Total sedim

reservoir water at the time of bottom-sedimen

collection (1998) was believed to be insignifi

was not calculated. Therefore, total sediment 

historically (1965–98) transported into Chene

voir was 15.5 billion lb, and the historical me

cultural-enrichment factor was 2.9 (542 mg/kg 

by 184 mg/kg).

It should be emphasized that the 2.9 enric

factor is a historical mean and that a current (

enrichment factor may be greater because of 

ent increasing trend in phosphorus transport f

watershed (fig. 6). In summary, agricultural a

during 1965–98 have increased the transport 

phorus into Cheney Reservoir 2.9 times great

that expected under natural concentrations of 

phorus in watershed soil.
Phosphorus and Sediment Retention Efficiencies of Cheney Reservoir 

Agricultural

sources

(65 percent)

Natural

sources

(35 percent)

Natural and Agricultural Sources

Historical contributions of phosphorus to Cheney

Reservoir from natural and agricultural sources could

not be measured directly, but instead, were estimated

from the previously calculated 2.9 historical mean

agricultural-enrichment factor for total phosphorus.

The enrichment factor, in effect, indicates that the

mass of phosphorus historically transported into

Cheney Reservoir is 2.9 times greater than the mass

expected under conditions where the watershed soil

contains an average natural concentration of soil phosphorus. In other words, the total mass of phosphorus

historically transported into Cheney Reservoir

(8.4 million lb) is about 2.9 times the mass from natural sources; thus, the mass from natural sources is

about 8.4 million lb divided by 2.9, or 2.9 million lb

(35 percent of the total mass historically transported).

The percentage of this total mass of phosphorus transported into Cheney Reservoir that originated from

agricultural sources, therefore, was about 65 percent

(5.5 million lb) (fig. 9).

The percentages shown in figure 9 represent historical averages and may not accurately describe current (2001) conditions. However, these percentages do

indicate that, because of the large percentage of phosphorus from agricultural sources, changes to agricultural or land-management practices that would

mitigate the movement of sediment and associated

phosphorus or changes in phosphorus application and

distribution in the watershed have a large potential for

reducing the mass of phosphorus transported to

Cheney Reservoir.

PHOSPHORUS AND SEDIMENT RETENTION

EFFICIENCIES OF CHENEY RESERVOIR

The masses of phosphorus and sediment trans

ported to and retained in Cheney Reservoir can be

used to calculate the retention efficiency of the re

voir for these constituents. Retention efficiency,

expressed as a percentage, was calculated by divi

the mass deposited as or in association with reser

bottom sediment by the total mass transported int

the reservoir, and multiplying the quotient by 100

The historical retention efficiency for phosphorus 

92 percent (7.7 million lb divided by 8.4 million l

times 100). The historical retention efficiency for 

iment was 99 percent (15.4 billion lb divided by

15.5 billion lb, times 100). These results indicate

that Cheney Reservoir is a sink for much of the m

of those water-quality constituents transported fro

the watershed.

A previous investigation of Cheney Reservoir

(Pope and Milligan, 2000) calculated a retention e

ciency of 62 percent for total phosphorus. This re

tively small retention efficiency, however, was

calculated on the basis of phosphorus loads transported in streamflow into and discharged from Ch

Reservoir, and it is probable that the 2 years (1997

for that investigation was not representative of his

cal average phosphorus transport conditions beca

of the absence of substantial runoff or flooding co

tions during 1997–98 (Putnam and others, 1998–9

The potential for surface-water bodies to reta

phosphorus varies, but many studies have docume

large retention efficiencies. For example, phosph

retention efficiencies for wetland and swamp area

Florida were calculated at 72 percent (Moustafa a

others, 1998) and 82 percent (Moustafa, 1999), re

tively; an agriculturally affected lake in southwes

Finland had a retention efficiency of greater than

80 percent (Ekholm and others, 1997); and a mul

pond system in southeastern China had a retentio

efficiency of about 98 percent (Weijin and others,

1998). More locally, Juracek (1998) calculated a 

torical phosphorus budget for Hillsdale Lake in n

east Kansas (fig. 1) that produced a phosphorus

retention efficiency of 89 percent. The 92-percen

phosphorus retention efficiency calculated for Ch

Reservoir, therefore, seems reasonable.

In a process similar to that for phosphorus, re

voirs also have the potential to retain large percent

of the inflow sediment load. Jansson and Erlings

(2000) calculated a sediment retention efficiency 

Figure 9. Comparison of phosphorus

transported to Cheney Reservoir from natural

and agricultural sources, 1965–98.
18 Historical Contributions of Phosphorus From Natural and Agricultural Sources and Implications for Stream Water Quality, Cheney Reser

Watershed, South-Central Kansas

about 80 percent for Cachi Reservoir in Costa Rica.

Tobin and Hollowed (1991) calculated a sediment

retention efficiency for Kenney Reservoir in northwestern Colorado that ranged from 91 to about

98 percent; the latter percentage corresponds well

to the 99-percent sediment retention efficiency

calculated for Cheney Reservoir in the study

described in this report.

Large retention efficiencies of water-quality constituents such as phosphorus or sediment may have

water-quality implications for, and may reduce the

useful life of, a reservoir. Phosphorus accumulation in

reservoir bottom sediment may provide a source of

internal loading of phosphorus (release of bioavailable

phosphorus from sediment) (Morris and Fan, 1998),

particularly under anaerobic (absence of oxygen) conditions at the sediment-water interface (Alaoui

Mhamdi and others, 1994; Istranovics, 1994). This

released bioavailable phosphorus may increase the rate

of algal production (Horne and Goldman, 1994) and,

subsequently, the occurrence of taste-and-odor problems in treated drinking water (Juttner, 1984; Hoson,

1992). However, under aerobic (oxygenated) conditions at the sediment-water interface, phosphorus

release from sediment may be greatly suppressed

(Erickson and Auer, 1998).

On the basis of limited depth profiling of dissolved

oxygen concentrations collected during the Cheney

Reservoir watershed study (1997–2000), anaerobic

conditions in Cheney Reservoir have not occurred.

Additionally, Gibson (1997) provided evidence that

indicated there is a phosphorus-concentration threshold at approximately 1,000 mg/kg dry sediment below

which sediment tended not to release phosphorus back

into the water column. Phosphorus concentrations in

Cheney Reservoir bottom sediment did not exceed this

threshold (Pope, 1998; Mau, 2001).

Although Cheney Reservoir has a large retention

efficiency for phosphorus (92 percent), other factors

such as well-oxygenated water and relatively small

concentrations of phosphorus in bottom sediment (less

than 1,000 mg/kg) may limit algal proliferation and

subsequent occurrences of taste-and-odor problems in

treated drinking water from the reservoir by inhibiting

the internal loading of phosphorus. In fact, taste-andodor problems in treated drinking water occurred

during several summers in the early 1990s (Cheney

Reservoir Watershed Task Force Committee, written

commun., 1996) but were not observed and reported

during the Cheney Reservoir watershed water

study (1996–2001) until the summer of 2001

One of the principal concerns with the tra

sediment into Cheney Reservoir is a loss of re

storage capacity (Cheney Reservoir Watershe

Force Committee, written commun., 1996). D

in reservoir storage capacity can affect reserv

cations used for flood control, drinking-water 

recreation, and wildlife habitat. The part of a 

designed for sediment storage is called the in

conservation storage pool and commonly is d

to provide storage for 100 years of sediment d

tion (Morris and Fan, 1998). As of 1998, 34 

sediment deposition had occurred in Cheney 

voir, which equates to 34 percent of the desig

the reservoir. A previous investigation of Che

ervoir (Mau, 2001) determined that during th

34 years in the design life of Cheney Reservo

27 percent of the allocated sediment storage c

had been used. Although the sediment retent

ciency at Cheney Reservoir was large (99 perc

design life of the reservoir is being met provi

the common design-life specifications were us

design of the reservoir.

IMPLICATIONS FOR STREAM WATER QUA

Information on natural concentrations of 

phosphorus in soil of the Cheney Reservoir w

relative to total phosphorus transported from 

watershed can provide insight into the attaina

stream-water-quality goals. The U.S. Environ

Protection Agency (1986) has recommended 

0.10 mg/L of total phosphorus in flowing surf

water. Additionally, the Cheney Reservoir Wa

Task Force Committee (written commun., 19

recommended the same long-term mean wate

goal of 0.10 mg/L for streams in the Cheney R

watershed.

In 1996, the USGS entered into a coopera

study with the city of Wichita to assess the oc

and transport of selected water-quality consti

including phosphorus, within the Cheney Res

watershed. As part of that study, six streamflo

pling sites were established in the watershed 

table 3). Streamflow sampling sites 1–5 were 

on the main stem of the North Fork Ninnesca

or its tributary streams. Sampling site 6 was l

the outflow of Cheney Reservoir. A continuou

of streamflow was collected at all six samplin
Implications for Stream Water Quality 

Cheney

Reservoir

North

Fork

River

Silver

Creek

Goose Creek

Irish Cr

Red Rock

Arkansas River

Creek

Ninnescah

0 5 10 15 

0 5 10 15 20 KILOMETERS

Reno County

Kingman County

Edwards County

Kiowa County

Pawnee County

Sedg

Coun

Stafford County

Pratt County

Stafford

Sylvia Abbyville Zenith

Penalosa

Arlington

Pretty Prairie

Haven

Kingman Pratt

Langdon

Castleton

Turon

Preston

99° 45' 30' 15' 98° 97°45

38°

37°45'

50

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°

EXPLANATION

Hutchinson

Contributing drainage area

Noncontributing drainage area

Boundary of Cheney Reservoir watershed

Boundary of subwatershed area

Surface-water-quality sampling site and 

 number

Haviland

Wellsford

Byers

Saint John

Iuka

Cunningham

Lerado

Huntsville

Sain

Plevna

2

2

1 5

4

6

3

Partridge

Samples of streamflow were collected during base

flow (low-flow conditions) and during runoff (highflow conditions) (table 4).

Automatic samplers were installed at streamflow

sampling sites 1–5. The analysis of samples collected

from these automatic samplers (automatic samples)

and additional manually collected samples (manual

samples) comprised the water-quality database for the

Cheney Reservoir watershed assessment. Most runoff

samples were collected with automatic samplers. Manual samples were collected to provide depth- and

width-integrated composite samples representative of

the average chemical composition of the stream’s

cross-sectional area. Automatic samples were collected from a single point in the stream cross-sectional

area and, therefore, may not be representative of the

average chemical composition of the stream’s crosssectional area at the time of sample collection. Samples were collected from January 1997 through

December 2000. Samples were analyzed for total

phosphorus concentrations at the city of Wichita

laboratory using U.S. Environmental Protection

Agency method 365.2 (U.S. Environmental Protection

Agency, 1999).

 Concentrations of total phosphorus determin

from automatically collected point samples were

adjusted to approximate the average cross-section

phosphorus concentration provided by depth- and

width-integrated manually collected samples. Thi

approximation was accomplished through the

development and application of sampling-site-spe

linear-regression relations between total phosphor

concentrations determined for pairs of concurrent

collected automatic and manual samples from stre

flow sampling sites 1–5 (fig. 10). Details of this ad

ment procedure are presented in Milligan and Pop

(2001).

More samples of streamflow for analysis of to

phosphorus were collected during runoff than dur

base flow (table 4) because the majority of phosph

from the Cheney Reservoir watershed is transport

during runoff conditions. For example, at sampli

site 4 (fig. 10), the main inflow site to Cheney Re

voir, it was estimated that 72 percent of the phosp

rus in streamflow at this site (1997–2000) was

transported during runoff. This percentage mirror

percentage of samples collected during runoff at s

pling site 4 (73 percent, table 4).

Figure 10. Location of streamflow sampling sites in Cheney Reservoir watershed.
20 Historical Contributions of Phosphorus From Natural and Agricultural Sources and Implications for Stream Water Quality, Cheney Reser

Watershed, South-Central Kansas

The 72-percent transport estimate for phosphorus

during runoff was calculated using a regression equation that related phosphorus load (PL, dependent variable), in grams per second, to streamflow (Q,

independent variable), in cubic feet per second. This

equation [PL = 0.00063Q1.423; R2

 (coefficient of

determination) equals 0.84, p-value of less than

0.0001] was an updated version of an equation used in

a previous investigation of phosphorus transport in the

Cheney Reservoir watershed during 1997–98 (Pope

and Milligan, 2000). It was updated to include total

phosphorus and streamflow data through 2000. Daily

mean streamflow (Putnam and others, 1998–2001) for

periods of base flow and runoff were used as input

variables for the regression equation. Daily loads and,

ultimately, percentage transport for base flow and runoff were calculated.

On average, total phosphorus concentration in

samples of streamflow collected during runoff were

about 2.0 (sampling site 2) to 4.4 (sampling sites 3 and

5) times larger than concentrations in sample

streamflow collected during base flow (table 4

concentrations of total phosphorus in samples 

streamflow also were calculated as a long-term

(1997–2000) average (table 4) using all availa

(base-flow and runoff) adjusted automatic and 

sample concentrations (fig. 11).

One of the purposes of determining natur

centrations of total phosphorus in soil is the es

of the potential to achieve stream-water-quali

under natural conditions, all other watershed 

being historically constant. This information m

substantial watershed-management implicatio

Mean total phosphorus concentrations at 

flow sampling sites 1–5 that have occurred un

ral concentrations of total phosphorus in soil 

estimated by dividing the previously determin

total phosphorus concentrations calculated fro

streamflow samples (1997–2000) by an agric

enrichment factor of 2.9. A comparison of me

Table 3. Description of streamflow sampling sites in Cheney Reservoir watershed, south-central Kansas

Sampling-site

map index

number

(fig. 10)

U.S. Geological Survey

site identification

number Sampling-site name

Co

dra

(squ

1 07144601 North Fork Ninnescah River at Arlington, Kansas 4

2 07144660 Silver Creek near Arlington, Kansas 1

3 07144680 Goose Creek near Arlington, Kansas 

4 07144780 North Fork Ninnescah River near Pretty Prairie, Kansas 7

5 07144730 Red Rock Creek near Pretty Prairie, Kansas 

6 07144795 North Fork Ninnescah River at Cheney Dam, Kansas 9

Table 4. Number of samples analyzed and mean concentrations of total phosphorus in streamflow during base-flow, runoff, and 

streamflow conditions at sampling sites 1–5 in Cheney Reservoir watershed, south-central Kansas, 1997–2000

[N, number of samples analyzed; mg/L, milligrams per liter]

Sampling-site map

index number

(fig. 10)

Base flow1

1

Data from Milligan and Pope (2001).

Runoff1

Long term1

(1997–2000)

N

Mean concentration

(mg/L) N

Mean concentration

(mg/L) N

Mean conce

(mg/

2

Calculated using all available base-flow and runoff analyses.

1 36 0.13 92 0.29 128 0.25

2 38 .14 78 .28 116 .23

3 40 .11 78 .48 118 .36

4 32 .10 85 .38 117 .30

5 37 .14 106 .62 143 .50
Implications for Stream Water Quality 

123 4 50.50 0.30

0.25

0.36

0.23

0.17

0.10

0.12

0.09

0.08

0

0.10

0.20

0.30

0.40

0.50

0.60

Surface-water-quality sampling site (fig. 10)

Phosphorus concentration,

in milligrams per liter

Estimated mean

natural phosphorus

concentrations

Long-term water-quality

goal for streams

Mean phosphorus

concentrations

(1997–2000)

mean and estimated mean total phosphorus concentrations (on the basis of a historical mean agriculturalenrichment factor of 2.9) in water from streamflow

sampling sites 1–5 is presented in figure 11. An examination of results presented in figure 11 indicates that

under natural concentrations of total phosphorus in

soil, mean total phosphorus concentrations in water

from two of the five streamflow sampling sites

upstream from Cheney Reservoir (sampling sites 3 and

5) would not meet the water-quality goal of 0.10 mg/L

established by the Cheney Reservoir Watershed Task

Force Committee. The conclusion, therefore, is that

even if soils in the Cheney Reservoir watershed were

maintained with natural concentrations of total phosphorus, some streams or stream segments would not

meet water-quality goals assuming all the other historical watershed conditions remained the same.

The implication of the information presented in

figure 11 is that the water-quality goal for total phosphorus in some streams in the Cheney Reservoir

watershed may not be met simply by reducing phosphorus concentrations in soil (reducing the amount of

phosphorus applied). Instead, meeting the goal could

involve a combination of approaches—for example,

reducing the agricultural distribution of phosphorus

and implementing changes in land-use, land-management, and agricultural practices that reduce the loss of

phosphorus from soil to water 

the movement of phosphorus-l

soil in runoff (Devlin and other

1998). Previous investigations 

shown a direct relation betwee

phosphorus concentrations and 

centages of the fine silt- and (o

clay-size (less than 0.062 mm) 

ticles (Galeone, 1996; Pope, 19

Therefore, changes in the water

that would mitigate the transpo

these fine particles also would

reduce the movement of phosp

rus to surface water and, poten

tially, the eutrophication of

Cheney Reservoir.

The possibility of substant

reductions in estimated long-te

mean concentrations of total ph

phorus in water from several sa

pling sites (for example, sites 1, 

and 4; figs. 10 and 11) probably 

not great. An analysis of total p

phorus concentrations in water from Kings Creek

(USGS gaging station 06879650) located on the

Konza Prairie Biological Station (KPBS) (fig. 1) 

northeast Kansas was conducted to compare resul

from the agriculturally dominated Cheney Reserv

watershed to a

“natural” (predevelopment) prairie-grass environm

The KPBS is representative of an eastern Kansas

native tallgrass prairie ecosystem (Kansas State U

versity, 2001).

Between 1980 and 1996, the USGS collected 

analyzed 76 samples of streamflow from Kings C

for total phosphorus. The mean concentration of 

phosphorus in these samples was 0.06 mg/L (data 

file at USGS office in Lawrence, Kansas), not too

dissimilar to the estimated long-term mean conce

tions determined under natural soil phosphorus co

tions at sampling sites 1, 2, and 4 in the Cheney

Reservoir watershed (fig. 11). This 0.06-mg/L co

centration may provide insight as to a lower thres

limit of total phosphorus in eastern Kansas, tallgr

prairie streams under “natural” conditions. There

it is probably unrealistic to expect that a long-term

mean concentration of total phosphorus in water f

a managed agricultural watershed would be less t

0.06 mg/L regardless of whether the soil phospho

concentrations in the watershed were natural conc

Figure 11. Comparison of measured (1997–2000) mean total phosphorus concentrations in

water samples from five streamflow sampling sites in Cheney Reservoir watershed and

mean concentrations estimated on basis of agricultural-enrichment factor of 2.9. Long-term

stream-water-quality goal established by Cheney Reservoir Watershed Task Force

Committee (written commun., 1996).
22 Historical Contributions of Phosphorus From Natural and Agricultural Sources and Implications for Stream Water Quality, Cheney Reser

Watershed, South-Central Kansas

trations or not. However, this supposition is qualified

with the fact that in 1987 the KPBS had a permanent

herd of bison established in the Kings Creek watershed and that in 1992 an experimental herd of cattle

was introduced (Kansas State University, 2001). It is

unknown to what extent these animal populations have

affected the long-term mean concentration of total

phosphorus in water from Kings Creek. The available

data set is not adequate for that type of analysis.

SUMMARY AND CONCLUSIONS

Phosphorus has been added routinely to agricultural soils to increase crop production. Historically,

however, applications have been in excess of crop

requirements and have led to a buildup of phosphorus

concentrations in soil beyond agronomic need. This

buildup of soil phosphorus has increased the potential

for phosphorus transport to surface water in runoff

from agricultural lands.

Excess phosphorus in surface water can accelerate

eutrophication (nutrient enrichment) particularly in

lakes and reservoirs. Cheney Reservoir in southcentral Kansas may be a reservoir with the potential

for detrimental effects from eutrophication and, in

fact, has a history of algal blooms and taste-and-odor

problems in treated drinking water.

To address the eutrophication issues in Cheney

Reservoir and nutrient transport from the Cheney Reservoir watershed, the U.S. Geological Survey, in 1996,

entered into a cooperative study with the city of Wichita, Kansas. Results from this study will be useful to

watershed managers in evaluating the sources and

transport of phosphorus in the Cheney Reservoir

watershed and the potential for meeting in-stream total

maximum daily loads for phosphorus under existing or

proposed land-use and land-management practices.

Concentrations of soil phosphorus transported to

Cheney Reservoir have been increasing at least since

the construction of the reservoir as indicated by bottom-sediment cores collected in 1997. However, the

extent to which these concentrations have increased

compared to natural concentrations is unknown. To

help determine if agricultural activities need to be

modified or land-management practices implemented

to control phosphorus transport, it was first necessary

to define the extent to which these activities have

increased phosphorus transport to the reservoir. Therefore, soil-core samples were collected at 43 nonagricultural coring sites (mostly cemeteries) in and near

Cheney Reservoir watershed in September 19

These sites were selected to represent soils w

ral concentrations of total phosphorus. Analy

soil-core samples from these 43 nonagricultu

resulted in natural concentrations of total pho

that ranged from 74 to 539 mg/kg with a med

centration of 245 mg/kg in 2-in. soil-core sam

from 50 to 409 mg/kg with a median concent

166 mg/kg in 8-in. soil-core samples. Natural 

trations of total phosphorus in soil were statis

larger in coring-site samples from the eastern 

the watershed than in coring-site samples from 

western half of the watershed. This determina

partly explains a previously determined west-

increase in total phosphorus yields in streams 

Cheney Reservoir watershed.

A comparison of soil phosphorus concen

from 43 nonagricultural sites in and near Che

ervoir watershed to the historical mean total p

rus concentration in agriculturally enriched b

sediment of Cheney Reservoir was made. Res

of this comparison indicated that agricultural

activities within the watershed have increased 

phosphorus concentrations in soil to about 2.9 

natural concentrations.

Retention efficiencies for the mass of pho

and sediment historically transported to Chen

ervoir were calculated at 92 and 99 percent, r

tively. Most of the phosphorus was retained i

bottom sediment. These large retention effici

raise concerns about potential water-quality is

loss of reservoir storage. However, reservoir 

such as well-oxygenated water and total phos

concentrations in bottom sediment less than a 

old concentration of 1,000 mg/kg, believed to 

phosphorus back into the water column, may 

problems associated with phosphorus in sedim

Sediment accumulation in Cheney Reservoir 

than reservoir design-life specifications on the 

the age of the reservoir.

Information on agricultural enrichment o

phosphorus concentrations in soil was used to 

mean total phosphorus concentrations in selec

streams of the Cheney Reservoir watershed th

have occurred under natural total phosphorus 

tions in soil. These estimates were made by d

the mean total phosphorus concentrations cal

from water samples collected at five streamflo

pling sites during 1997–2000 by an agricultur

enrichment factor of 2.9. Results of these esti
References 

indicated that, under natural phosphorus conditions in

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total phosphorus concentrations in water from two of

the five streamflow sampling sites in the Cheney Reservoir watershed would not meet a water-quality goal

of 0.10 mg/L established by the Cheney Reservoir

Watershed Task Force Committee. The implication of

these results is that the water-quality goal for total

phosphorus in some streams of the Cheney Reservoir

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goal could involve a combination of approaches—for

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phosphorus and implementing changes in watershed

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Agricultural activities have had an effect on phosphorus input to Cheney Reservoir and may have

contributed to past reservoir algal blooms and tasteand-odor problems in treated drinking water and may

reduce the aesthetic and recreational value of the reservoir. Information concerning the extent of phosphorus enrichment in soil of the Cheney Reservoir

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in eutrophication of Cheney Reservoir.

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