U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2009–5182

In cooperation with the Oklahoma Scenic Rivers Commission

Summary of Surface-Water Quality Data from the Illinois 

River Basin in Northeast Oklahoma, 1970–2007
Front cover:

Underwater photo, Baron Fork near Eldon, Oklahoma, August 2003. Photograph by W.J. Andrews, U.S. 

Geological Survey. 
Summary of Surface-Water Quality Data 

from the Illinois River Basin in Northeast 

Oklahoma, 1970–2007

By William J. Andrews, Mark F. Becker, S. Jerrod Smith, and Robert L. Tortorelli

In cooperation with Oklahoma Scenic Rivers Commission

Scientific Investigations Report 2009–5182

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2009

This and other USGS information products are available at http://store.usgs.gov/

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Denver, CO 80225

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U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Andrews, William J., Becker, Mark F., S. Jerrod Smith, and Robert L. Tortorelli, 2009, Summary of surface-water 

quality data from the Illinois River Basin in North Oklahoma, 1970–2007: U.S. Geological Survey Scientific Investigations Report 2009–5182, 39 p. 
iii

Contents

Abstract ..........................................................................................................................................................1

Introduction ....................................................................................................................................................1

Purpose and Scope .............................................................................................................................3

Methods ..........................................................................................................................................................3

Hydrologic Setting ........................................................................................................................................3

Hydrology ..............................................................................................................................................3

Climate ..........................................................................................................................................3

Streamflow ...................................................................................................................................4

Groundwater ................................................................................................................................4

Land Use, Water Use, and Economics .............................................................................................5

Land Use .......................................................................................................................................5

Water Use ..................................................................................................................................10

Water and the Local Economy ................................................................................................10

Water-Quality Degradation by Nutrients ..............................................................................14

Water Quality ...............................................................................................................................................15

General-Water Quality ......................................................................................................................15

Nutrients ..............................................................................................................................................15

Concentrations ..........................................................................................................................17

Loads, Flow-Weighted Concentrations, and Trends ...........................................................19

Chlorophyll-a .......................................................................................................................................19

Bacteria ...............................................................................................................................................19

Types of Bacteria Analyzed .....................................................................................................24

Bacterial Abundance ...............................................................................................................24

Possible Sources of Bacteria .................................................................................................24

Trends in Bacteria with Streamflow ......................................................................................25

Sediment ..............................................................................................................................................26

Types of Suspended Sediment ...............................................................................................27

Relations of Sediment with Streamflow and Phosphorus Concentrations .....................27

Summary .......................................................................................................................................................33

References Cited .........................................................................................................................................33

Glossary ........................................................................................................................................................38

Figures

1. Map showing the Illinois River Basin, Arkansas and Oklahoma, with locations of 

long-term water-quality monitoring sites and of permitted point discharge sites ...........2

2. Schematic diagram of the hydrologic cycle in the Illinois River Basin, Arkansas 

and Oklahoma ...............................................................................................................................5

3. Map showing karstic areas of the United States ..................................................................6

4. Photographs of karstic features and plant life in the Illinois River Basin in 

Oklahoma ......................................................................................................................................7
iv

5–6. Maps showing: 

5. Land cover in the Illinois River Basin, Arkansas and Oklahoma in 2008 ...................8

6. Distribution of poultry confined animal feeding houses in the Illinois River 

Basin, Arkansas and Oklahoma in 2006 ..........................................................................9

7. Stacked bar charts of approximate daily nitrogen and phosphorus output, in 

pounds per day, by humans and livestock in the parts of counties in the Illinois 

River Basin in 2007 .....................................................................................................................11

8–9. Maps showing: 

8. Distribution of human population density in the Illinois River Basin, Arkansas 

and Oklahoma in 2000 ......................................................................................................12

9. Locations of public water supply intakes and wells in the Illinois River Basin, 

Arkansas and Oklahoma ..................................................................................................13

10. Water use in 2005 in the Illinois River Basin, Arkansas and Oklahoma ...........................14

11. Percentages of major ions in milliequivalents per liter in surface-water samples 

collected at selected stations in the Illinois River Basin in Oklahoma .............................16

12–19. Graphs showing: 

12. Molar ratios of total nitrogen and total phosphorus with time for long-term 

water-quality monitoring sites in the Illinois River Basin in Oklahoma ...................18

13. Mean daily streamflow and mean daily streamflow on sampling days for 

total nitrogen for long-term water-quality monitoring sites in the Illinois River 

Basin in Oklahoma ............................................................................................................20

14. Mean daily streamflow and mean daily streamflow on sampling days for 

total phosphorus for long-term water-quality monitoring sites in the Illinois 

River Basin in Oklahoma .................................................................................................21

15. Total nitrogen concentration compared to mean daily streamflow for longterm water-quality monitoring sites in the Illinois River Basin in Oklahoma ..........22

16. Total phosphorus concentration compared to mean daily streamflow for longterm water-quality monitoring sites in the Illinois River Basin in Oklahoma ..........23

17. Mean daily streamflow compared to chlorophyll-a concentration in water 

samples from long-term water-quality monitoring sites in the Illinois River 

Basin in Oklahoma ............................................................................................................25

18. Total nitrogen concentration compared to chlorophyll-a concentration in 

water samples from long-term water-quality monitoring sites in the Illinois 

River Basin in Oklahoma ..................................................................................................26

19. Total phosphorus concentration compared to chlorophyll-a concentration in 

water samples from long-term water-quality monitoring sites in the Illinois 

River Basin in Oklahoma ..................................................................................................27

20. Photographs showing filamentous periphyton algae growing on streambed 

rocks at a) Flint Creek north of New Hope Ranch, and b) Baron Fork near Eldon, 

Oklahoma ....................................................................................................................................28

21–24. Graphs showing:

21. Fecal coliform bacteria counts with time for long-term water-quality 

monitoring sites in the Illinois River Basin in Oklahoma ............................................29

22. Fecal coliform bacteria counts compared to streamflow for long-term 

water-quality monitoring sites in the Illinois River Basin in Oklahoma ..................30

23. Suspended sediment concentration compared to mean daily streamflow 

for long-term water-quality monitoring sites in the Illinois River Basin in 

Oklahoma ...........................................................................................................................31

24. Suspended sediment concentration compared to total phosphorus 

concentration for long-term water-quality monitoring sites in the Illinois 

River Basin in Oklahoma ..................................................................................................32
v

Tables

1. Drainage-basin area of long-term water-quality monitoring sites in the Illinois 

River Basin in Oklahoma .............................................................................................................4

2. Mean monthly streamflow for long-term water-quality monitoring sites in the 

Illinois River Basin in Oklahoma during the period of record and the 10 year 

period, 1996–2006 .........................................................................................................................4

3. Approximate numbers of livestock and human residents in the counties 

comprising the Illinois River Basin, and in the parts of those counties in the 

basin, 2005–2007 ........................................................................................................................10

4. Trends of streamflow, and total nitrogen and phosphorus concentrations, loads, 

and flow-adjusted concentrations at long-term water-quality monitoring sites in 

the Illinois River Basin from 1997–2004 ..................................................................................24

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

Flow rate

cubic foot per second (ft3

/s) 0.02832 cubic meter per second (m3/s)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3

/s)

Mass

pound (lb) 0.4536 kilogram (kg) 

ton per year (ton/yr) 0.9072 metric ton per year

Load

pound per day (lb/day) 0.4546 Kilogram per day (kg/day)

Application rate

pound per acre per year [(lb/acre)/yr] 1.121 kilogram per hectare per year [(kg/ha)/yr]

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) 

or micrograms per liter (μg/L).
Blank Page
Abstract

The quality of streams in the Illinois River Basin of 

northeastern Oklahoma is potentially threatened by increased 

quantities of wastes discharged from increasing human populations, grazing of about 160,000 cattle, and confined animal 

feeding operations raising about 20 million chickens. Increasing numbers of humans and livestock in the basin contribute 

nutrients and bacteria to surface water and groundwater, causing greater than the typical concentrations of those constituents for this region. Consequences of increasing contributions 

of these substances can include increased algal growth (eutrophication) in streams and lakes; impairment of habitat for 

native aquatic animals, including desirable game fish species; 

impairment of drinking-water quality by sediments, turbidity, 

taste-and-odor causing chemicals, toxic algal compounds, and 

bacteria; and reduction in the aesthetic quality of the streams.

The U.S. Geological Survey, in cooperation with the 

Oklahoma Scenic Rivers Commission, prepared this report 

to summarize the surface-water-quality data collected by the 

U.S. Geological Survey at five long-term surface-water-quality 

monitoring sites. The data summarized include major ions, 

nutrients, sediment, and fecal-indicator bacteria from the Illinois River Basin in Oklahoma for 1970 through 2007.

General water chemistry, concentrations of nitrogen 

and phosphorus compounds, chlorophyll-a (an indicator 

of algal biomass), fecal-indicator bacteria counts, and sediment concentrations were similar among the five long-term 

monitoring sites in the Illinois River Basin in northeast 

Oklahoma. Most water samples were phosphorus-limited, 

meaning that they contained a smaller proportion of phosphorus, relative to nitrogen, than typically occurs in algal tissues. 

Greater degrees of nitrogen limitation occurred at three of the 

five sites which were sampled back to the 1970s, probably 

due to use of detergents containing greater concentrations of 

phosphorus than in subsequent periods. Concentrations of 

nitrogen, phosphorus, and sediment, and counts of bacteria 

generally increased with streamflow at the five sites, probably due to runoff from the land surface and re-suspension 

of streambed sediments. Phosphorus concentrations typically 

exceeded the Oklahoma standard of 0.37 milligrams per liter 

for Scenic Rivers. Concentrations of chlorophyll-a in phytoplankton in water samples collected at the five sites were not 

well correlated with streamflow, nor to concentrations of the 

nutrients nitrogen and phosphorus, probably because much of 

the algae growing in these streams are periphyton attached to 

streambed cobbles and other debris, rather than phytoplankton 

in the water column. Sediment concentrations correlated with 

phosphorus concentrations in water samples collected at the 

sites, probably due to sorption of phosphorus to soil particles 

and streambed sediments and runoff of soils and animal wastes 

at the land surface and resuspension of streambed sediments 

and phosphorus during wet, high-flow periods. Fecal coliform 

bacteria counts at the five sites sometimes exceeded the Oklahoma Primary Body Contact Standard of 400 colonies per 100 

milliliters when streamflows were greater than 1000 cubic feet 

per second.

Ultimately, Lake Tenkiller, an important ecological and 

economic resource for the region, receives the compounds that 

runoff the land surface or seep to local streams from groundwater in the basin. Because of eutrophication from increased 

nutrient loading, Lake Tenkiller is listed for impairment by 

diminished dissolved oxygen concentrations, phosphorus, 

and chlorophyll-a by the State of Oklahoma in evaluation of 

surface-water quality required by section 303d of the Clean 

Water Act.

Stored phosphorus in soils and streambed and lakebed 

sediments may continue to provide phosphorus to local 

streams and lakes for decades to come. Steps are being made 

to reduce local sources of phosphorus, including upgrades in 

capacity and effectiveness of municipal wastewater treatment 

plants, and exporting phosphorus-rich poultry litter from parts 

of the basin to cropland outside of the basin.

Introduction

The Illinois River Basin drains 1,653 square miles (4,281 

square kilometers) in northeastern Oklahoma and northwestern Arkansas (fig. 1). The topography, ecology, and economy 

of the Illinois River Basin are all derived, at least in part, by 

the quantities and patterns of naturally flowing water. The 

Oklahoma Scenic Rivers Act of 1970 designated the Illinois 

River, and two of its tributaries, Flint Creek and Baron Fork 

(formerly Barren Fork), as Scenic Rivers to protect water quality and preserve fish, wildlife, and outdoor recreational values 

Summary of Surface-Water Quality Data from the Illinois 

River Basin in Northeast Oklahoma, 1970–2007

By William J. Andrews, Mark F. Becker, S. Jerrod Smith, and Robert L. Tortorelli
2 Summary of Surface-Water Quality Data from the Illinois River Basin in Northeast Oklahoma, 1970–2007

Figure 1. The Illinois River Basin, Arkansas and Oklahoma, with locations of permitted point discharge sites. 

DELAWARE

CHEROKEE

SEQUOYAH

ADAIR

CRAWFORD

WASHINGTON

BENTON OKLAHOMA

ARKANSAS

36° 30’

36° 00’

35° 30’

95° 00’

94° 00’ 94° 00’

0 5 10 20 MILES

0 10 20 5 KILOMETERS

Tenkiller

Lake

Illinois

Caney

Flint

Baron

Osage

Creek

River

Creek

Fork

Creek

Arkansas

River

07197000

07196500

07196090

07196000

07195500

Tahlequah

Westville

Prairie Grove

Fayetteville

Springdale

Rogers

Siloam

Springs

07197000

EXPLANATION

State boundary

Stream

Permitted point discharge

U.S.Geological Survey streamflow gage

with station number (long-term

water-quality monitoring site having

data summarized in this report)

City

Lake

County boundary

Gage-defined watershed boundary

Illinois River watershed boundary

Albers Equal-Area Conic Projection, North American Datum 1983

Streams modified from U.S. Geological Survey (2008)

Watershed boundaries modified from Natural Resources Conservation Service (2008)

Oklahoma point discharge locations from Oklahoma Department of Environmental Quality (2008)

Arkansas point discharge locations from GeoStor (2008)

OKLAHOMA

ARKANSAS

Illinois

River
Hydrologic Setting 3

for the benefit of the people of Oklahoma and visitors to the 

State (Oklahoma Legislature, 1970). The Oklahoma Scenic 

Rivers Commission, created in 1977, enforces the Oklahoma 

Scenic Rivers Act (Oklahoma Legislature, 1977).

About half of the basin is devoted to grazing of cattle 

and horses and raising poultry, consisting mostly of about 

20 million broiler chickens. Wastes generated by rapid growth 

in human populations in parts of the basin are additional 

potential sources of nutrients and bacteria. These sources of 

nutrients and bacteria, combined with the relatively high vulnerability of water in the basin to contamination because 

of the karstic setting, have combined to increase contamination of local streams by nutrients, bacteria, chlorophyll-a, and 

sediment.

The upstream half of the basin has a rapidly growing 

economy with a large livestock agriculture sector and has had 

rapid growth in human population because of growth of large 

corporate headquarters, a state university, and retirement 

communities. The downstream half of the basin is less intensively developed, relying on water-based recreation in scenic 

rivers and Lake Tenkiller as a large part of local economic 

activity. In addition to aesthetic issues possibly reducing 

tourism, numerous cities, towns, and other landowners in 

both states rely on surface water for drinking-water supplies 

or on groundwater from wells very near to streams, that can 

be affected by degraded surface-water quality. Many streams 

in the area may be phosphorus-limited, meaning that relatively 

small additions of phosphorus may notably increase growth 

of algae. Phosphorus typically is sorbed to soil and sediments. 

So phosphorus tends to wash into local streams or be resuspended into local water bodies in greatest amounts during 

storm runoff/high-flow periods. Bacteria from animal wastes 

also tend to increase greatly in local streams during high 

streamflows, similarly being washed from land surfaces by 

rainfall.

The U.S. Geological Survey (USGS), in cooperation with 

the Oklahoma Scenic Rivers Commission (OSRC), prepared 

this report to summarize the surface-water-quality data collected by the USGS at five long-term water-quality monitoring 

sites. These data include major ions, nutrients, sediment, fecalindicator bacteria, chlorophyll-a, and from the Illinois River 

Basin in Oklahoma from 1970 through 2007.

Purpose and Scope

The purpose of this report is to summarize water-quality 

data and describe probable sources of and transport of common water contaminants in streams designated as Scenic 

Rivers in the Oklahoma part of the Illinois River Basin. Waterquality data collected by the U.S. Geological Survey at five 

long-term water-quality monitoring sites for periods as long as 

1970 to 2007, including major ions, nutrients, fecal-indicator 

bacteria, chlorophyll-a, sediment, and are summarized in this 

report. This report is intended to inform the OSRC and the 

general public about water-quality issues and data collected in 

this basin in a readily understandable manner.

Methods

Water-quality and streamflow data described in the 

Hydrology and Water Quality sections of this report were 

retrieved from the U.S. Geological Survey National Water 

Information System (NWIS; http://waterdata.usgs.gov/nwis). 

Information regarding hydrogeology, climatology, populations 

of livestock and humans, and water-quality degradation in the 

Illinois River Basin were gathered from a variety of reports by 

the U.S. Geological Survey, state agencies, and universities. 

Estimates of livestock numbers were based on the 2007 census 

of agriculture (Arkansas Agricultural Statistics Service, 2008; 

and Oklahoma Agricultural Statistics Service, 2008). Estimates of per capita emissions of nutrients in waste for humans 

and livestock were based on livestock numbers for counties in 

the basin in 2007. County livestock numbers were amortized 

for the part of each county in the Illinois River Basin, which 

assumes that livestock are equally distributed in those counties. Per capita and from nutrient-emission data for humans 

and livestock derived from Strauss (2000) and Gollehon and 

others (2001). Locations of poultry houses in the upstream 

part of the Basin in 2006 were from Arkansas State Highway 

and Transportation (2008). Locations of poultry houses in the 

downstream part of the basin in summer 2006 were determined from National Agriculture Imagery Program aerial photographs obtained from Oklahoma GIS Council (2007). The 

five long-term water-quality monitoring stations summarized 

in this report were selected based on location, from near to 

where the Illinois River flows from Arkansas into Oklahoma, 

to downstream from Tahlequah, the largest city close to the 

river in Oklahoma. Those 5 sites had from 8 to more than 40 

years of water-quality sampling and streamflow data.

Hydrologic Setting

Hydrology

The Illinois River Basin is underlain by cherty limestones 

of the Springfield Plateau aquifer that commonly are karstic 

(fractured and partially dissolved, with fissures, sinkholes, 

underground streams, and caverns) and are deeply incised by 

streams and rivers. The karstic nature of the rocks underlying 

this basin is responsible for the rolling hills topography and 

underground caverns and conduits that facilitate rapid recharge 

and seepage of groundwater.

Climate

The climate of the Illinois River Basin is humid temperate. Average annual precipitation in the basin ranges from 

46.5 to 48.6 inches; average annual temperatures range from 

60 to 61 degrees Fahrenheit, with average maximum temperatures of 70 to 71 degrees, and average minimum temperatures 
4 Summary of Surface-Water Quality Data from the Illinois River Basin in Northeast Oklahoma, 1970–2007

of 48 to 49 degrees (National Oceanic and Atmospheric 

Administration, 2007; Oklahoma Climatological Survey, 

2007a, b, c, d). Precipitation amounts tend to vary over the 

basin during the spring storm season, with several inches 

per day commonly falling from storms. About 40 percent 

(20 inches) of the annual mean precipitation of nearly 50 

inches falls from March to June in the basin (Oklahoma 

Climatological Survey, 2007e). After the spring storm season, 

summer tends to be dry. During a second storm season in 

autumn (September to November), nearly 30 percent of annual 

precipitation falls (Oklahoma Climatological Survey, 2007e). 

Winters in the basin are relatively dry (Oklahoma Climatological Survey, 2007e). Mean annual lake evaporation in this 

basin has been estimated to be about 50 inches (Johnson and 

Duchon, 1995), with evapotranspiration (the combination of 

evaporation from soils and transpiration of water by plants) 

estimated to range from 30 to 35 inches per year in Oklahoma 

(Hanson, 1991).

Streamflow

Streamflow in the Illinois River Basin is highly varied 

and generally increases with the basin drainage area associated with any given site (tables 1 and 2). The greatest mean 

monthly streamflows in the basin are from March through 

June (when spring rains occur) and the least mean monthly 

streamflows occur in summer dry periods from July through 

August (table 2, Blazs and others, 2001–2006).

The USGS has continuously operated a stream gage on 

the Illinois River near Tahlequah since 1936. Streamflow at 

that and other gages is reported in cubic feet per second (ft3

/s); 

that is, a volume of water moving through a cross-sectional 

area of the stream in one second. Peak streamflow and low 

streamflow are reported by various methods. One method is 

to report the average streamflow during a specific period of 

time. Examples of the variability of streamflow in the Illinois 

River are the extreme flows recorded at the Illinois River near 

Tahlequah gage such as: (1) the maximum mean daily streamflow of 90,400 ft3

/s on May 11, 1950, and (2) the minimum 

mean daily streamflow of 0.10 ft3/s on October 10, 1956. The 

mean annual streamflow at that gage from 1936 to 2007 is 

929 ft3/s. 

Streamflow during periods of no runoff from precipitation is referred to as base flow. Base flow in the Illinois River 

is sustained by a combination of groundwater discharging 

from seeps and springs and discharges by humans into the 

river and tributaries, such as municipal wastewater emanating 

from treatment plants and seepage from on-site septic systems. 

Extended dry periods or droughts can reduce ground-water 

levels thus reducing the base flow in the Illinois River (fig. 2). 

For 1936 to 2007, base flow ranged from 29.7 (in 1943) to 

72.5 (in 1963) percent of annual flow at the Illinois River near 

Tahlequah gage (Jason M. Lewis, U.S. Geological Survey, 

written commun., 2009).

Groundwater

The Illinois River Basin is underlain by a series of limestone, sandstone, and shale strata on the southwestern edge of 

the Ozarks uplift (Marcher and Bingham, 1989; and Petersen 

and others, 1999a). Lands underlain by limestone, gypsum, 

Table 2. Mean monthly streamflow for long-term water-quality monitoring sites in the Illinois River Basin in Oklahoma during the period of record 

and the 10 year period, 1996–2006. 

[units in cubic feet per second; POR, period of record or length of gage operation, data not available for the Illinois River at Chewey, Oklahoma, which is ungaged] 

Station

Month

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep

Illinois River near Watts, 1956–2006 (POR) 346 646 665 601 698 956 1,016 968 685 368 239 289

Illinois River near Watts, 1996–2006 234 568 569 756 765 840 891 735 734 431 233 289

Flint Creek near Kansas, 1956–2006 (POR) 69 126 124 113 122 172 176 178 147 67 45 57

Flint Creek near Kansas, 1996–2006 38 82 84 121 131 143 118 122 143 83 39 38

Baron Fork at Eldon, 1949–2006 (POR) 166 321 319 318 392 523 579 613 341 151 76 114

Baron Fork at Eldon, 1996–2006 110 323 315 429 420 463 547 393 390 161 77 116

Illinois River near Tahlequah, 1936–2006 (POR) 519 900 907 882 1,118 1,426 1,562 1,612 1,042 509 353 360

Illinois River near Tahlequah, 1996–2006 357 798 865 1,130 1,155 1,289 1,309 1,118 1,132 660 320 363

Table 1. Drainage-basin area of long-term water-quality 

monitoring sites in the Illinois River Basin in Oklahoma. 

Station 

number Station name

Drainage 

basin area 

(square miles)

07195500 Illinois River near Watts, Oklahoma 635

07196000 Flint Creek near Kansas, Oklahoma 110

07196090 Illinois River at Chewey, Oklahoma 825

07197000 Baron Fork at Eldon, Oklahoma 307

07196500 Illinois River near Tahlequah, Oklahoma 959
Hydrologic Setting 5

and other highly soluble rocks in humid environments commonly are characterized by karstic topography, that has hilly 

relief, sinkholes, caves, and numerous springs (figs. 2, 3 

and 4). Because of rapid seepage of water from the land surface to underlying aquifers and dissolution of carbonate rocks, 

human activities, such as urbanization, agriculture, water withdrawals, and deforestation, can quickly have negative effects 

on water quality, land-surface stability, and underground cave 

ecosystems (Petersen and others, 1999a; and U.S. Geological 

Survey, 2007). 

Land Use, Water Use, and Economics

Land Use

Land uses in the Illinois River Basin are primarily 

agriculture (pasture and hay (42.17 percent) and forested 

(43.52 percent)). Minor amounts of commercial and residential land uses are in agricultural areas, with most of urban and 

suburban areas occurring in the upstream end of the basin in 

Arkansas (fig. 5, and Multi-Resolution Land Characteristics 

Consortium, 2008).

Major agricultural activities in the basin include the raising of poultry and swine in confined animal feeding operations (CAFOs) and cattle grazed on pastures fertilized with 

commercial fertilizer, and litter and manure from CAFOs. 

In 2007, approximately 20 million laying hens, broilers, or 

turkeys; 14,000 hogs; and 160,000 cattle on pasture resided in 

the basin, with the most of those livestock being raised in the 

upstream part of the basin (fig. 6, table 3, Arkansas Agricultural Statistics Service, 2008; and Oklahoma Agricultural 

Statistics Service, 2008). Manures from CAFOs commonly 

are applied as fertilizers to pastures in the basin, potentially 

comprising many tons per day production of nitrogen and 

phosphorus compounds (fig. 7, Carreira and others, 2007). 

Nitrogen production in manures in these counties ranged from 

a few hundred pounds to more than 60,000 pounds per day 

(fig. 7). Phosphorus production in manures in these counties 

ranged from a few hundred pounds about 21,000 pounds per 

Figure 2. Schematic diagram of the hydrologic cycle in the Illinois River Basin, Arkansas and Oklahoma. 

Water Table

Saturated Zone

Unsaturated

Zone

Water

seeps

preferentially

from land

surface to water table

along conduits

Erosion-resistant

sandstone

forms ridge cap

Ground-water flow

Karstic

limestone of

the Ozark

Aquifer

System

Bedded

sandstone

Springs seeping

from conduit

openings on

ridge face

River valley incised 

through karstic limestone 

into underlying sandstone.

Intermittent stream

Ground-water seepage providing

baseflow of river.

Precipitation

Storm

runoff
6 Summary of Surface-Water Quality Data from the Illinois River Basin in Northeast Oklahoma, 1970–2007

Figure 3. Karstic areas of the United States (U.S. Geological Survey, 2008). 

EXPLANATION

Karst

Illinois River watershed boundary
Hydrologic Setting 7

day (fig. 7). Concern about saturation of local soils with phosphorus and subsequent runoff of that nutrient to local streams 

and lakes led the State of Arkansas to enact nutrient management statutes in 2003 (Carreira and others, 2007). Since 2005, 

poultry litter export from the Illinois River Basin has increased 

to almost 70,000 tons per year of about 350,000 tons produced 

annually. Litter export is assisted by state subsidies, though 

concerns exist that the amount of litter exported from the basin 

is not yet sufficient to notably reduce phosphorus loading to 

local streams and lakes (Smith, 2008; and Oklahoma Conservation Commission, 2009a). Litter production and application 

amounts reported by county in Oklahoma in 2008 (Oklahoma 

Conservation Commission, 2009b), if scaled for the percentages of the four counties in the basin (table 3), indicate that 

about 26,700 tons of litter were produced and 15,600 tons of 

litter were applied, indicating export of about 11,100 tons of 

litter from the basin. Several factors may affect such estimates, 

such as long-term storage and composting of poultry litter by 

producers (Dan Parrish, Oklahoma Department of Agriculture, 

Food, and Forestry, oral commun., 2009), incorrect reporting of litter production and application, or variable rates of 

production and application across those counties. Most of the 

poultry litter exported from the Illinois River Basin has been 

applied to cropland in other parts of Oklahoma, though 

a potential market exists in cotton-growing areas in the 

Mississippi Embayment in eastern Arkansas (Smith, 2008; and 

Carriera and others, 2007).

The number and distribution of the human population 

in the Illinois River Basin also have important implications 

for water quality. The upstream part of the basin in northwestern Arkansas contains the Fayetteville-Springdale-Rogers 

Metropolitan Statistical Area (MSA, urban center), that was 

the sixth-fastest-growing MSA in the U.S. from 1990 to 2007, 

having a 74 percent increase in population from 211,000 

to 367,000 (fig. 8; Carreira and others, 2007). Reasons for 

growth in that area include the presence of headquarters of 

large, fast-growing international corporations such as Walmart, 

Tyson Foods, and J.B. Hunt Transportation; growing educational institutions such as the University of Arkansas (enrolled 

student body of 17,929 in 2007), and increasing numbers of 

retirees seeking relatively low-cost rural living (Rogers-Lowell 

Area Chamber of Commerce, 2006; and University of Arkansas, 2007). Population centers and the approximate numbers of 

residents in the basin include: Springdale, Arkansas (63,082, 

2006 estimate); Fayetteville, Arkansas (68,726, 2006 estimate); Rogers, Arkansas (52,181, 2006 estimate), Siloam 

Springs, Arkansas (10,843 in the 2000 Census); Prairie Grove, 

Arkansas (2,540 in the 2000 Census); Tahlequah, Oklahoma 

(14,458 in the 2000 Census); and Westville, Oklahoma (1,596 

in the 2000 Census) (U.S. Census Bureau, 2008b).

Watercress and water willow

growing along the spring-fed

Caney Creek in the Illinois River

Basin (Jim Petersen, U.S.

Geological Survey photo).

Photograph showing incision of

the Illinois River throgh

limestone strata (Ed Fite,

Oklahoma Scenic Rivers

Commission photo).

Elephant Rock, an example

of karstic dissolution of

limestone and a spring

discharging from underground

caves in Sparrowhawk Loop of

the Illinois River Valley

(Northeastern State University

photo).

Figure 4. Karstic features and plant life in the Illinois River Basin in Oklahoma. 
8 Summary of Surface-Water Quality Data from the Illinois River Basin in Northeast Oklahoma, 1970–2007

Figure 5. Land cover in the Illinois River Basin, Arkansas and Oklahoma in 2008. 

DELAWARE

CHEROKEE

SEQUOYAH

ADAIR

CRAWFORD

WASHINGTON

BENTON OKLAHOMA

ARKANSAS

36° 30’

36° 00’

35° 30’

95° 00’

94° 00’ 94° 00’

0 5 10 20 MILES

0 10 20 5 KILOMETERS

Tenkiller Lake

Illinois

Caney

Flint

Baron

Osage

Creek

River

Creek

Fork

Creek

Arkansas

River

07197000

07196500

07196090

07196000

07195500

Tahlequah

Westville

Prairie Grove

Fayetteville

Springdale

Rogers

Siloam

Springs

07197000

EXPLANATION

State boundary

Stream

U.S. Geoogical Survey streamflow gage

with station number

City

Lake

County boundary

Gage-defined watershed boundary

Illinois River watershed boundary

Water and wetlands

Developed

Forest

Grasslands

Pasture/hay

Cultivated crops

Land cover, 2008, in percent of total land area

Albers Equal-Area Conic Projection, North American Datum 1983

Streams modified from U.S. Geological Survey (2008)

Watershed boundaries modified from Natural Resources Conservation Service (2008)

Land cover from National Land Cover Dataset (Multi-Resolution Land Characteristics Consortium, 2008)

2.05

8.74

43.52

3.36

42.17

0.16
Hydrologic Setting 9

Figure 6. Distribution of poultry confined animal feeding houses in the Illinois River Basin, Arkansas and Oklahoma in 2006. 

DELAWARE

CHEROKEE

SEQUOYAH

ADAIR

CRAWFORD

WASHINGTON

BENTON OKLAHOMA

ARKANSAS

36° 30’

36° 00’

35° 30’

95° 00’

94° 00’ 94° 00’

0 5 10 20 MILES

0 10 20 5 KILOMETERS

Tenkiller

Lake

Illinois

Caney

Baron

Creek

River

Fork

Creek

Arkansas

River

07197000

07196500

07196090

07196000

07195500

Tahlequah

Westville

Prairie Grove

Fayetteville

Springdale

Rogers

Siloam

Springs

07197000

!

!

!

!

!!

! !!

!

!

!

!

!

!!

!

!

EXPLANATION

State boundary

Stream

U.S. Geological Survey streamflow gage

with station number

City

Lake

County boundary

Gage-defined watershed boundary

Illinois River watershed boundary

Poultry house or complex of houses

Albers Equal-Area Conic Projection, North American Datum 1983

Streams modified from U.S. Geological Survey, 2008)

Watershed boundaries modified from Natural Resources Conservation Service (2008)

Arkansas poultry houses from 2006 images from Arkansas State Highway and Transportation Department (2008)

Oklahoma poultry houses from 2006 summer images from National Agriculture Imagery Program (Oklahoma GIS Council, 2007)

Creek

Flint

Osage
10 Summary of Surface-Water Quality Data from the Illinois River Basin in Northeast Oklahoma, 1970–2007

Water Use

Water use is an important element in describing the 

Illinois River Basin because it: (1) affects the amount of 

water in local streams and lakes available to dilute and 

assimilate contaminants, and (2) can affect the quantities of 

contaminants discharged to local streams, depending on the 

activity, water treatment methods, and the proximity of the 

use to those streams. The water-use estimates for this basin 

were for the year 2005 (Holland, 2007; and Robert L. Tortorelli, U.S. Geological Survey, written commun., 2009). The 

compilation for the part of the basin in Oklahoma was done 

specifically for the Illinois River Basin. Because data for the 

part of the basin in Arkansas were computed by county (Holland, 2007) water uses for the parts of those counties in the 

Illinois River Basin were estimated by scaling county wateruse numbers by the percentages of the counties in the basin 

(listed on table 3), which assumes that water uses were evenly 

distributed across those counties. Water withdrawals of nearly 

378 million gallons per day at the American Electric Power 

plant from Swepco Lake and Siloam Springs in Arkansas were 

not included in water-use estimates in this report. Surfacewater withdrawal sites for public supplies tend to be clustered 

along Osage and Flint Creeks in the upstream part of the basin 

and around Lake Tenkiller in the downstream part of the basin 

(fig. 9). Most of the public-supply wells in the basin are along 

the Illinois River in the downstream part of the basin (fig. 9).

A slightly greater amount of water use was estimated 

for the upstream part of the basin in Arkansas (23.33 million 

gallons per day) than in the downstream part of the basin in 

Oklahoma (21.88 million gallons per day). Surface-water use 

is predominant in the Illinois River Basin, comprising about 

93 percent of total water use (fig. 10). Domestic self-supplied 

ground-water use comprised 6.5 percent of total water use 

in the downstream part of the basin in Oklahoma and comprised 1.1 percent of total water use in the upstream part of 

the basin in Arkansas. Approximately 20,000 gallons per day 

of groundwater were withdrawn by public water supplies in 

the downstream part of the basin in Oklahoma, whereas about 

380,000 gallons per day of groundwater were withdrawn for 

that purpose in the upstream part of the basin in Arkansas.

Water and the Local Economy

The lower part of the basin, in particular along the 

Illinois River and Flint and Baron Fork Creeks in Oklahoma, 

including small cities such as Tahlequah in Oklahoma, relies 

strongly on tourism to support the local economy. The amount 

of tourism and economic effect of tourism in the basin is 

highly dependent on aesthetically pleasing water and water 

Table 3. Approximate numbers of livestock and human residents in the counties comprising the Illinois River Basin, and in the parts of 

those counties in the basin, 2005–2007. 

[%, percentage; --, unknown]

County, state

Estimated total livestock numbers by county, 2007 Estimated 

human 

residents, 2007

Cattle and 

calves Swine Broilers Layers Turkeys Horses

Benton, Arkansas 1

94,588 -- 120,360,012 11,664,829 1577,344 13,415 3203,107

Washington, Arkansas 1

102,394 128,417 120,487,381 11,482,401 11,347,582 14,808 3194,292

Adair, Oklahoma 2

61,191 2609 24,405,354 2266,977 -- 22,330 321,902

Cherokee, Oklahoma 2

49,048 2552 2347,183 221,552 289,607 22,803 345,393

Delaware, Oklahoma 2

83,197 2449 29,174,334 21,113,570 -- 22,791 340,406

Sequoyah, Oklahoma 2

40,701 -- 2282,656 2459,876 276 22,330 341,024

County, state 

(percentage of county 

land area in basin)

Estimated total livestock numbers in the Illinois River watershed by county, 2007 Estimated 

human 

residents, 2007

Cattle and 

calves Swine Broilers Layers Turkeys Horses

Benton, Arkansas (34.2%) 32,349 -- 6,963,124 569,372 197,452 1,168 69,463

Washington, Arkansas (47.6%) 48,740 13,526 9,751,993 705,623 641,449 2,289 92,483

Adair, Oklahoma (69.0%) 42,222 420 3,039,694 184,214 -- 1,608 15,112

Cherokee, Oklahoma (44.7%) 21,924 247 155,191 9,634 40,054 1,253 20,291

Delaware, Oklahoma (9.74%) 8,103 44 893,580 108,462 -- 272 3,936

Sequoyah, Oklahoma (10.5%) 4,274 -- 29,679 47,827 8 242 4,308

Estimated total numbers 157,612 14,237 20,833,261 1,625,132 878,963 6,832 205,593

1 2007 County Estimates (Arkansas Agricultural Statistics Service, 2008).

2

 2007 County Estimates (Oklahoma Agricultural Statistics Service, 2008).

3

 2007 County Population Estimates (U.S. Census Bureau, 2008a). 
Hydrologic Setting 11

Figure 7. Stacked bar charts of approximate daily nitrogen and phosphorus output, in pounds per day, by humans and livestock in the 

parts of counties in the Illinois River Basin in 2007. ESTIMATED NITROGEN EMISSION, IN POUNDS PER DAY ESTIMATED PHOSPHORUS EMISSION, IN POUNDS PER DAY

Humans

Horses and Ponies

Turkeys

Layers

Broilers

Swine

Cattle and Calves

0

20,000

40,000

60,000

70,000

Benton, Arkansas

Washington, Arkansas

Adair, Oklahoma

Cherokee, Oklahoma

Delaware, Oklahoma

Sequoyah, Oklahoma

PART OF COUNTY IN ILLINOIS RIVER BASIN

Humans

Horses and Ponies

Turkeys

Layers

Broilers

Swine

Cattle and Calves

0

5,000

10,000

15,000

20,000

22,500

(Data Sources: Arkansas Agricultural Statistics Service, 2008; Oklahoma Agricultural Statistics

Service, 2008; Strauss, 2000; and Gollihon and others, 2001)
12 Summary of Surface-Water Quality Data from the Illinois River Basin in Northeast Oklahoma, 1970–2007

Figure 8. Distribution of human population density in the Illinois River Basin, Arkansas and Oklahoma in 2000. 

DELAWARE

CHEROKEE

SEQUOYAH

ADAIR

CRAWFORD

WASHINGTON

BENTON OKLAHOMA

ARKANSAS

36° 30’

36° 00’

35° 30’

95° 00’

94° 00’ 94° 00’

0 5 10 20 MILES

0 10 20 5 KILOMETERS

Tenkiller

Lake

Illinois

Caney

Flint

Baron

Osage

Creek

River

Creek

Fork

Creek

Arkansas

River

07197000

07196500

07196090

07196000

07195500

Tahlequah

Westville

Prairie Grove

Fayetteville

Springdale

Rogers

Siloam

Springs

07197000

EXPLANATION

State boundary

Stream

U.S. Geological Survey streamflow gage

with station number

City

Lake

County boundary

Gage-defined watershed boundary

Illinois River watershed boundary

Albers Equal-Area Conic Projection, North American Datum 1983

Streams modified from U.S. Geological Survey (2008)

Watershed boundaries modified from Natural Resources Conservation Service (2008).

Census tract population data from U.S. Census Bureau (2007).

Census tract population density, in people

per square mile, 2000

Less than 50

50 - 500

500 - 100

1,000 - 2,000

2,000 - 3,000

Greater than 3,000
Hydrologic Setting 13

Figure 9. Locations of public water supply intakes and wells in the Illinois River Basin, Arkansas and Oklahoma. 

DELAWARE

CHEROKEE

SEQUOYAH

ADAIR

CRAWFORD

WASHINGTON

BENTON OKLAHOMA

ARKANSAS

36° 30’

36° 00’

35° 30’

95° 00’

94° 00’ 94° 00’

0 5 10 20 MILES

0 10 20 5 KILOMETERS

Illinois

C aney

Flint

Baron

Osage

Creek

River

Creek

F ork

Creek

Arkansas

R iver

07197000

07196500

07196090

07196000

07195500

Tahlequah

Westville

Prairie Grove

Fayetteville

Springdale

Rogers

Siloam

Springs

07197000

EXPLANA TION

State boundary

Stream

U.S. Geological Survey streamflow gage

with station number

City

Lake

County boundary

Gage-defined watershed boundary

Illinois River watershed boundary

Public water-supply well (Ground water)

Public water-supply intake (Surface water)

Public water-supply intake (Spring)

!

!

!

!

! !

!

!

!

!

! !

! !

!

!

!

!

!

! !

!

!

!

!

! !

! !

!

!

!

!

!

!

!

Albers Equal-Area Conic Projection, North American Datum 1983

Streams modified from U.S. Geological Survey (2008)

Watershed boundaries modified from Natural Resources Conservation Service (2008)

Oklahoma water-supply sites from Oklahoma Department of Environmental Quality (2008)

Arkansas water-supply sites from Arkansas Department of Environmental Quality (written commun.,

Terry Holland, U.S. Geological Survey, 2008)

Lake Tenkille r

Illinois

River
14 Summary of Surface-Water Quality Data from the Illinois River Basin in Northeast Oklahoma, 1970–2007

quality that is safe for primary body contact for the 400,000 

tourists who spend about $12 million annually in the basin, 

much of that on water-related recreational activities (Ed 

Fite, Oklahoma Scenic Rivers Commission, oral commun., 

2009). An additional $30 million is spent each year by about 

2,000,000 visitors to Lake Tenkiller (Don Nowlin, Greater 

Tenkiller Area Association, oral commun., 2009).

Water-Quality Degradation by Nutrients

Six streams in Arkansas and five streams in Oklahoma 

in the Illinois River Basin were listed for exceeding waterquality standards established by Section 303d of the Clean 

Water Act in 2004 (U.S. Environmental Protection Agency, 

2007). The quality of 7 of those 11 streams was impaired by 

total phosphorus, including the Illinois River and Tenkiller 

Ferry Lake (commonly referred to as Lake Tenkiller) (fig. 1). 

Nitrate was the cause of water-quality impairment in 2 of the 

11 impaired streams, and bacteria, organic enrichment (lack 

of dissolved oxygen), and the condition of fish habitat being 

the causes of impairment of one stream each in the basin 

(U.S. Environmental Protection Agency, 2007). The quality of water in Lake Tenkiller has been notably degraded for 

several years by algal blooms (that limit recreational use and 

can be toxic to livestock and aquatic animals), anoxic water 

because of metabolism of living algae and decay of plant matter (that can suffocate aquatic animals and cause taste and odor 

problems), and increased turbidity (Steele and others, 2003). 

Some species of algae also produce organic compounds that 

can be toxic to fish, shellfish, humans, livestock, and wildlife 

(Creekmore, 1999).

Phosphorus and nitrogen are necessary nutrients for plant 

and animal growth. However, only limited amounts of nutrients can be effectively used by plants and animals in an ecosystem. An overabundance of nutrients causes vigorous plant 

growth. This plant growth is commonly in the form of algae 

in waterways. Nutrients entering the watershed are classified 

by the general sources and pathways. A point source directly 

discharges nutrients and/or other substances into the environment, an example being a wastewater treatment plant that 

discharges treated municipal wastewater to a stream. Another 

type of source is nonpoint that introduces contaminants to surface water diffusely in precipitation runoff. Runoff of manure 

and inorganic fertilizer applied to the land surface are common 

nonpoint sources of nutrients and/or bacteria in rural areas. 

Phosphorous and ammonium-nitrogen tend to adsorb 

to soil particles. Ammonium (NH4

+

) in soils, animal wastes, 

and water is converted rapidly to nitrate (NO3

-

) in oxidizing 

conditions. Nitrate is much more soluble in water and more 

available to plants than ammonium. Soils over much of the 

basin are believed to contain as much phosphorus as can be 

effectively absorbed (Nelson and Trost, 2002). Most additional 

loading from livestock manure is believed to be transported 

in runoff to local streams that can cause eutrophication of 

streams and lakes and build up phosphorus-enriched sediments 

in those water bodies that can continue to be sources of phosphorus to the streams through erosion and leaching. Storm and 

others (1996) estimated dissolved phosphorus yields (amounts 

of a substance running off or leaching from a given unit of 

land area per unit of time) of more than 1 pound per acre per 

year for much of the upstream part of the basin. Storm and 

others (1996) also estimated that nonpoint sources produced 

ARKANSAS

Water Use in Million Gallons per Day

OKLAHOMA

TOTAL=21.88 TOTAL=23.33

(from Robert L. Tortorelli, U.S. Geological Survey, written commun., 2009; and Holland, 2007)

Public Water Supply

Surface Water (11.3)

Domestic Self-Supplied

Ground Water (1.43)

Commercial/Industrial

Self-Supplied

Surface Water (1.29)

Public Water Supply

Ground Water (0.02)

Irrigation and Livestock

Ground Water (0.26)

Irrigation and Livestock

Surface Water (7.58)

Public Water Supply

Surface Water (20.1)

Commercial/Industrial

Self-Supplied

Surface Water (0.12)

Irrigation and Livestock

Surface Water (1.55)

Domestic Self-Supplied

Ground Water (0.26)

Public Water Supply

Ground Water (0.38)

Irrigation and Livestock

Ground Water (0.95)

Figure 10. Water use in 2005 in the Illinois River Basin, Arkansas and Oklahoma. 
Water Quality 15

by humans (such as pastures, poultry houses, and septic tanks) 

produced about two-thirds (67 percent) of the phosphorus 

reaching the Illinois River, with point sources (such as outfalls 

from municipal wastewater treatment plants) producing all 

but 2 percent of the remaining phosphorus loading (31 percent 

total). Phosphorus concentrations in streams in the upstream 

part of the basin tend to decrease exponentially with distance 

downstream from wastewater outfalls to streams, indicating 

storage in streambed sediments (Haggard and others, 2003), 

and uptake by aquatic plants and animals. Substantial investments ($186,500,000) have been made since 2000 on upgrading capacity and phosphorus removal capabilities at municipal wastewater treatment plants in northwestern Arkansas 

(Melnichak, 2008). Such improvements are likely to diminish 

loading of phosphorus to stream segments downstream from 

such plant outfalls and perhaps to farther downstream areas. 

Efforts to export poultry litter from the basin also may help, 

with time, to reduce loading of phosphorus to streams in the 

basin (Young and others, 2005).

Water Quality

Surface water and groundwater in the Illinois River Basin 

and the surrounding Ozarks region generally contains large 

amounts of calcium and bicarbonate dissolved from limestone, 

making most water in the region relatively hard (Adamski, 

2000). Nitrate dissolved in the water is derived from natural 

sources such as bedrock, and human activities such as agriculture, seepage of human wastewater from septic tanks, and 

discharges of municipal wastewater from point sources.

Streamflow has a substantial effect on surface-water 

quality in the Illinois River Basin and adjoining basins in the 

Ozarks, with storm runoff flushing contaminants from the 

land surface, increasing concentrations of nutrients, bacteria, 

and sediment in streams (Petersen and others, 1999a). Runoff 

water from storms is likely to contain phosphorus that is commonly attached to particles of soil and other organic matter 

(Hem, 1992). Large streamflows from storms also may scour 

and resuspend streambed sediments containing phosphorus. 

Nitrogen and phosphorus compounds such as nitrate, ammonium, and orthophosphate can contribute to eutrophication, or 

excessive growth of algae and other plants, in streams.

General-Water Quality

Groundwater seeping to rivers and streams in the Illinois River Basin is likely to be classified as hard water, containing abundant calcium and bicarbonate. Trace element 

concentrations in water are generally low in this basin. Forested areas of the region typically have the best water quality, 

with agricultural and urban land uses contributing greater 

amounts of nutrients, pesticides, and fecal-indicator bacteria 

to water in streams and aquifers (Petersen and others, 1999a 

and 1999b). Median concentrations of the major ions—

calcium, magnesium, sodium, potassium, bicarbonate, chloride, and sulfate—were similar between sites sampled in the 

basin (fig. 11), although water samples from the Baron Fork at 

Eldon, Oklahoma, site had slightly smaller median concentrations of those ions than the other gaging stations. About 90 

percent of the water samples analyzed for major ions collected 

at the five stations were collected at base-flow conditions, so 

those concentrations primarily reflect the quality of groundwater seeping to these streams.

Nutrients

Water quality in 11 stream segments in the Illinois River 

Basin, including the Illinois River, Flint Creek, the Baron 

Fork, and Lake Tenkiller have been listed as being impaired 

by elevated phosphorus concentrations under section 303d of 

the Clean Water Act (U.S. Environmental Protection Agency, 

2007). Gollehon and others (2001) estimated that Washington 

and Benton Counties in Arkansas produced greater quantities 

of nitrogen and phosphorus in livestock manure than could 

be assimilated by soils. According to Goodwin (2004), 

phosphorus-based best management practices and local soil 

phosphorus concentrations indicate that 300,000 tons of poultry litter would need to be exported from those counties annually to minimize runoff of phosphorus to local streams and 

lakes. Counties in the Oklahoma part of the basin, with smaller 

quantities of manure from livestock (table 3), have generated 

quantities of nitrogen and phosphorus from livestock manure 

that were estimated to be 25 percent or less of the soil capacity 

to assimilate those nutrients (Gollehon and others, 2001). 

Groundwater, the source of base flow to streams in the 

basin, had greater nutrient concentrations in areas of agricultural land uses, compared to forested land uses, but nitrate 

nitrogen concentrations in groundwater in the basin rarely 

exceed the drinking-water standard of 10 milligrams per liter 

(Petersen and others, 1999a).

Critical issues for minimizing eutrophication of surface 

waters are: (a) reduction in the quantities of nutrients running 

off to or seeping into surface water, and (b) control of the 

ratios of nutrients, particularly of nitrogen and phosphorus 

in surface water. The ratio between nitrogen and phosphorus by weight in most green algae is 7.2 to 1, or 16 to 1 on a 

molecular-ratio basis (Allan, 1995). Because green algae take 

up those nutrients in a similar ratio in algal biomass, those 

ratios between nitrogen and phosphorus are considered to be 

ideal for growth. Nitrogen-to-phosphorus ratios of 20 to 1 

or greater indicate potential deficiency of phosphorus; 

whereas, ratios of 10 to 1 or less indicate potential deficiency 

of nitrogen (United Nations Environment Programme, 2007). 

Nitrogen-to-phosphorus ratios are useful for general guidance 

as to what nutrient may be most likely to encourage plant 

growth in surface water, but if nutrient concentrations are sufficiently large, then these nutrients also may be available for 

uptake, regardless of the ratios. A greater part of total phosphorus than total nitrogen also may not be readily available for 

plant uptake, being bound to small colloids or other particles 
16 Summary of Surface-Water Quality Data from the Illinois River Basin in Northeast Oklahoma, 1970–2007

Figure 11. Percentages of major ions in milliequivalents per liter in surface-water samples collected at selected stations in the Illinois

River Basin in Oklahoma. 

BARON FORK AT ELDON, OKLAHOMA

1975-2007

ILLINOIS RIVER AT CHEWEY, OKLAHOMA

1996-2007

ILLINOIS RIVER NEAR WATTS, OKLAHOMA

1970-2007

ILLINOIS RIVER NEAR TAHLEQUAH, OKLAHOMA

1975-2007

FLINT CREEK NEAR KANSAS, OKLAHOMA

1975-2007

[pie charts are percentages of major ions, expressed in milliequivalents per lite; milliequivalents per liter in parenthesesr]

(0.2)

(0.1)

(0.3)

CALCIUM

(2.1)

SODIUM

(0.5)

(1.8)

CHLORIDE

(0.4)

MAGNESIUM

(0.1)

SODIUM

(0.1)

(0.2)

CHLORIDE

(0.1)

CALCIUM

(1.7)

(<0.1) BICARBONATE

1.5 MG/L

(0.2)

SODIUM

(0.6)

(0.1)

(0.4)

CALCIUM,

(2.2)

(2.0)

CHLORIDE

(0.5)

CALCIUM,

(0.2) (2.3)

SODIUM

(0.5)

(0.1)

(2.1) (0.2)

CHLORIDE

(0.3)

CALCIUM,

(2.0) (0.2)

SODIUM

(0.3)

(0.1)

(1.8) (0.2)

CHLORIDE

(0.3)

BICARBONATE

MAGNESIUM

POTASSIUM

SULFATE

POTASSIUM

BICARBONATE BICARBONATE

BICARBONATE

MAGNESIUM

MAGNESIUM MAGNESIUM

POTASSIUM POTASSIUM

POTASSIUM

SULFATE

SULFATE

SULFATE

SULFATE
Water Quality 17

in water (Jones and Knowlton, 1993). When phosphorus 

concentrations are increased relative to nitrogen, commonly 

because of use and discharge of phosphorus-containing 

detergents or runoff of phosphorus-rich fertilizers and soils 

into water bodies, blue-green algae (known as cyanobacteria) tend to bloom (Levich, 1996). In addition to blooming in 

phosphorus-enriched waters, blue-green algae, that can extract 

nitrogen from air to supplement relatively nitrogen-poor 

environments, can exacerbate “hypereutrophic” conditions.

Hypereutrophic conditions in lakes and streams happen 

when water has concentrations of greater than 40 micrograms 

per liter (mg/L) chlorophyll-a (a pigment used by plants for 

photosynthesis), total phosphorus concentration greater than 

100 mg/L, and total nitrogen concentration greater than 1,200 

mg/L) (Jones and Knowlton, 1993). Hypereutrophic conditions are characterized by extreme growth of algae that: 

(a) discolor and cloud water (reducing feeding of predator 

fish), (b) decrease dissolved oxygen concentrations in water 

as part of algal respiration and plant-tissue decay, (c) increase 

sedimentation (filling in lakes and gravel spawning beds), 

(d) emit organic chemicals that cause taste and odor in water 

and can be toxic, (e) decrease diversity of aquatic species, 

and (f) change the dominant aquatic biota (Mason, 2002; 

Creekmore, 1999). Although suspended algae (phytoplankton) 

tend to be washed downstream in rivers, flowing water is not 

immune to the effects of eutrophication. Attached filamentous 

and colonial algae (periphyton), and other plants that can cover 

stream bottoms, affect the habitats of fish and other aquatic 

animals by covering gravel streambeds used for spawning.

Growth of colonial and filamentous blue-green algae in 

nutrient-enriched waters tends to be unimpeded by naturally 

occurring grazing crustaceans that have difficulty consuming blue-green algae because of the physical structure, poor 

nutritional quality, and toxins contained in the blue-green algal 

tissues (Levich, 1996). Such lack of grazing limits available 

food for organisms higher up in the food chain when bluegreen algae are dominant in streams and lakes (Levich, 1996). 

Water samples intermittently collected from the Illinois River 

Basin, from 1975–2007 generally were deficient in total 

phosphorus, relative to nitrogen, meaning that phosphorus 

may be a limiting nutrient for eutrophication in the basin (fig. 

12). For waters in which algal and plant growth is limited by 

phosphorus, controlling phosphorus discharges to the river and 

the tributaries can be the most cost-effective means of limiting 

eutrophication.

Phosphorus in the Illinois River Basin is derived from 

point and nonpoint sources. Large concentrations of phosphorous relative to nitrogen in the Illinois River prior to 1982 

(fig. 12) may be, in part, related to the use of phosphorus in 

laundry detergents (Litke, 1999). The use of phosphorous in 

detergents gradually tapered off after peaking in 1970, due 

partly to the voluntary withdrawal of phosphates from those 

products by the industry from 1972 to 1994 (Litke, 1999). 

Stream sites draining agricultural areas of the basin (nonpoint 

source) tend to have fish communities dominated by primarily 

planktivorous (plant-eating) fish such as stonerollers; whereas 

fish communities in streams in this region receiving lesser 

amounts of nutrients in forested basins had greater numbers 

of carnivorous (animal-eating) members of the sunfish group, 

including basses, that are more popular with anglers (Petersen 

and others, 1999a).

Concentrations

Phosphorus concentrations in Ozark streams typically are 

greater in streams draining agricultural areas and downstream 

from wastewater-treatment plants, than in streams draining 

forested areas (Petersen and others, 1999a, 1999b). Runoff 

from pastures fertilized with animal manures may be substantial sources of phosphorus to rivers in the basin (Arkansas 

Department of Environmental Quality, 2000). Streams receiving point-source inflows of wastewater from municipal and 

industrial treatment plants can have phosphorus concentrations 

substantially greater than concentrations typically detected in 

streams draining agricultural areas of the basin (Petersen and 

others, 1999a, 1999b; Haggard and others, 2003). Numerous 

cities, towns, and smaller entities discharge treated municipal 

wastewater to the Illinois River and the tributaries (fig. 1).

U.S. Environmental Protection Agency (1986) recommends that the concentration of total phosphorus not exceed 

0.1 mg/L in streams at the point of inflow to lakes or reservoirs (Petersen and others, 1999b). The State of Oklahoma 

set a standard/limit for total phosphorus of 0.037 mg/L, 

with not more than 25 percent of samples allowed to exceed 

that standard during any 3-month period to minimize potential 

eutrophication of Scenic Rivers in Oklahoma (State of Oklahoma, 2006). That standard is based on the 75th percentile 

of flow-weighted total phosphorus concentrations in streams 

draining 85 relatively undeveloped basins across the United 

States (Clark and others, 2000).

Water-quality samples were collected at the Illinois 

River near Watts and near Tahlequah, Oklahoma stations 

on a periodic basis prior to 1999, without regard to streamflow. Because streamflow is typically at or near base flow 

during much of the year, most of the water-quality samples 

prior to 1999 were collected at or near base-flow conditions 

(figs. 13 and 14). Water-quality sampling procedures at these 

and neighboring stations were modified after 1999 to collect 

samples at six high-flow and six base-flow periods annually, 

to gain better understanding of the effects of high streamflows 

on nutrient concentrations and to better determine annual 

flow-weighted concentrations of nutrients and time-trends in 

flow-weighted nutrient concentrations in the Illinois River, 

as described in Pickup and others (2003) and Tortorelli and 

Pickup (2006).

Concentrations of total nitrogen (sum of nitrate, nitrite, 

ammonium, and organic nitrogen) and of total phosphorus 

generally increased with increasing streamflow at all of the 

long-term water-quality monitoring sites, with most phosphorus concentrations exceeding the Oklahoma standard 

for Scenic Rivers of 0.037 mg/L, except at the Baron Fork 

at Eldon, Oklahoma site (figs. 15 and 16). Increases in 
18 Summary of Surface-Water Quality Data from the Illinois River Basin in Northeast Oklahoma, 1970–2007

Figure 12. Molar ratios of total nitrogen and total phosphorus with time for long-term water-quality monitoring sites in the Illinois River 

Basin in Oklahoma. 

1990 1995 2000 2005

NITROGEN LIMITED

INTERMEDIATE N:P

PHOSPHORUS

LIMITED

Flint Creek Near Kansas, Oklahoma,

1990-2007

1

10

100

1000

2005

Baron Fork at Eldon, Oklahoma,

1975-2007

1

100

1000

1975 1980 1985 1990 1995 2000

10

0.1

10000

Pre-1982 No Analyses

NITROGEN LIMITED

INTERMEDIATE N:P

PHOSPHORUS

LIMITED

1991-2007

Post-1988 Pre1982

1975 1980 1985 1990 1995 2000 2005

0.1

No Analyses

NITROGEN LIMITED

INTERMEDIATE N:P

PHOSPHORUS

LIMITED

Illinois River Near Tahlequah, Oklahoma,

1975-2007

1

10

100

1000

YEAR

Pre-1982 Post-1988

1975 1980 1985 1990 1995 2000 2005

No

Analyses

NITROGEN LIMITED

INTERMEDIATE N:P

PHOSPHORUS

LIMITED

Illinois River Near Watts, Oklahoma,

1975-2007

1

10

100

1000

2005

NITROGEN

LIMITED

INTERMEDIATE N:P

PHOSPHORUS

LIMITED

Illinois River at Chewey, Oklahoma,

1996-2007

NITROGEN TO PHOSPHORUS, MOLAR RATIO (N:P)

1

10

100

1000

200420032002200120001999199819971996 2006 2007
Water Quality 19

concentrations of these nutrients with increases in streamflow 

indicate that storm runoff in parts of the basin upstream from 

these stations carries substantial quantities of nutrients from 

soils, animal wastes, and other sources. If point-sources of 

nutrients, such as municipal wastewater treatment plants, were 

the primary sources of nutrients in the river, then nutrient 

concentrations would tend to decrease with increasing streamflow, because of dilution of relatively constant discharges of 

nutrients from such sources. The data at these sites indicated 

that nonpoint sources of nutrients exceeded contributions from 

nutrient point sources (figs. 15 and 16). However, build-up of 

nutrient-rich sediments in stream segments downstream from 

wastewater treatment plants may become re-suspended during 

high streamflows, complicating analysis of relative proportions of nutrient sources at varying streamflow conditions.

Loads, Flow-Weighted Concentrations, and 

Trends

Pickup and others (2003) reported for 1997 through 2001 

that flow-weighted total phosphorus concentrations generally increased at these long-term water-quality monitoring 

sites, but that the increase may have been partially because 

of increased sampling at high flows starting in 1999. Flowweighted concentrations are estimates of the mean concentrations of a substance in the total volume of water flowing past 

a given point in a stream for a given period of time. During 

the period from 1997-2001, an annual average of 577,000 

pounds of phosphorus flowed down the Illinois River into 

Lake Tenkiller, with more than 86 percent of that phosphorus 

being transported during runoff (Pickup and others, 2003). 

Tortorelli and Pickup (2006) reported for 2000 through 2004 

that estimated annual phosphorus loads were greater at the 

sites on the Illinois River, ranging from 331,000 to 559,000 

pounds per year, compared to 32,300 to 154,000 pounds 

per year in the Flint Creek and Baron Fork tributaries to the 

Illinois River. Seasonal estimated base-flow loads were greatest in the spring and least in autumn, with seasonal estimated 

runoff-loads varying, depending on the time periods measured 

(Tortorelli and Pickup, 2006). For 2000 through 2004 at these 

sites, flow-weighted total phosphorus concentrations tended to 

decrease slightly, except at the Flint Creek near Kansas, Oklahoma station (Tortorelli and Pickup, 2006). Mean annual phosphorus loads from 2000-2004 flowing down the Illinois River 

to Lake Tenkiller ranged from 391,000 pounds to 712,000 

pounds, with 83–90 percent of those loads being transported 

during runoff (Tortorelli and Pickup, 2006).

Rebich and Demcheck (2007) reported on changes in 

streamflow, and concentrations, loads, and flow-adjusted 

concentrations of nutrients at these sites and about 100 other 

sites in the south-central U.S. from 1997–2004. That report 

indicated that flow-weighted concentrations of total nitrogen 

and total phosphorus were increasing during that period at 

most of the sampled sites in the Illinois River Basin (table 4). 

Analyses of changes in fertilizer use, livestock manure production, human population density and land management practices during that period in this basin indicated that for most 

stations, annual increases of 5 to 10 kilograms of phosphorus 

per square kilometer seeping to local streams from increases 

in fertilizer use and 5 to more than 10 kilograms per square 

kilometer in annual increases in phosphorus reaching local 

streams from increases in livestock raised in the basin (Rebich 

and Demcheck, 2007).

Chlorophyll-a

Chlorophyll-a, a green pigment contributing to photosynthesis in algae and plants, is a commonly measured surrogate 

for the biomass of phytoplankton (suspended algae) in water 

of lakes and the biomass of periphyton (attached algae) on 

streambeds. Concentrations of chlorophyll-a in water samples 

collected at four stations in the Illinois River Basin in Oklahoma did not show substantive relations with total streamflow (fig. 17), nor with the concentrations of total nitrogen 

(fig. 18) and total phosphorus (fig. 19). Substantial numbers 

of phytoplankton commonly bloom in near-surface waters of 

lakes, such as Lake Tenkiller, that receive water with elevated 

concentrations of nitrogen and phosphorus during the summer, 

when sunlight needed for photosynthesis is strongest.

Phytoplankton tend to be continuously washed downstream in flowing streams rather than accumulating in large 

numbers in the water column. In flowing streams receiving 

water with elevated concentrations of nutrients, periphyton 

(algae attached to streambed rocks and gravels) are more 

likely to grow in dense filaments or colonies than suspended 

phytoplankton (fig. 20), although single-celled suspended 

algae such as diatoms also may increase turbidity of streams. 

Agricultural areas in the Ozarks region tend to contribute 

greater concentrations of nutrients to streams than forested 

areas and have fewer trees shading stream channels, contributing to increased growth of periphyton and increased abundance of species of fish known as stonerollers, that graze on 

streambed periphyton (Peterson and others, 1999a and 1999b; 

and Petersen and Femmer, 2002). Filamentous, nitrogen-fixing 

blue-green algae of the genus Calothrix (fig. 20) are among 

the most common periphyton in Ozark streams (Petersen and 

Femmer, 2002).

Bacteria

Bacteria are everywhere and are intricately linked to 

larger ecosystem processes. Bacteria have adapted to very 

specific environmental conditions. When the conditions are 

favorable, bacteria thrive and multiply. Because bacteria are 

specific to environments, some are used as indicators of nutrient sources and ecologic health. Of concern in the Illinois 

River Basin are bacteria that are referred to as “enteric” that 

live in the intestines of birds and mammals. These bacteria are 

commonly referred to as “fecal indicator bacteria” or simply 

“fecal bacteria.” When found in abundance, these bacteria 

indicate the introduction of animal waste into the environment. 

These waste products may contain other harmful bacteria or 
20 Summary of Surface-Water Quality Data from the Illinois River Basin in Northeast Oklahoma, 1970–2007

Figure 13. Mean daily streamflow and mean daily streamflow on sampling days for total nitrogen for long-term water-quality 

monitoring sites in the Illinois River Basin in Oklahoma. 

1975 1980 1985 1990 1995 2000 2005

0

10,000

20,000

30,000

40,000

TOTAL NITROGEN SAMPLES,

ILLINOIS RIVER NEAR WATTS,

OKLAHOMA

1975 1980 1985 1990 1995 2000 2005

10,000

20,000

30,000

40,000

0

YEAR

1975 1980 1985 1990 1995 2000 2005

10,000

20,000

30,000

40,000

50,000

0

TOTAL NITROGEN

SAMPLES, ILLINOIS

RIVER NEAR

TAHLEQUAH,

OKLAHOMA

1975 1980 1985 1990 1995 2000 2005

0

4,000

8,000

TOTAL NITROGEN

SAMPLES,

FLINT CREEK NEAR

KANSAS,

OKLAHOMA

MEAN DAILY STREAMFLOW, IN CUBIC FEET PER SECOND

1995 1997 1999 2001 2003 2005 2007

TOTAL NITROGEN

SAMPLES, ILLINOIS

RIVER AT

CHEWEY,

OKLAHOMA

EXPLANATION

Streamflow

Streamflow at time of

sampling

10,000

20,000

30,000

0

TOTAL NITROGEN

SAMPLES, BARON FORK AT

ELDON,

OKLAHOMA
Water Quality 21

Figure 14. Mean daily streamflow and mean daily streamflow on sampling days for total phosphorus for long-term water-quality 

monitoring sites in the Illinois River Basin in Oklahoma. 

TOTAL PHOSPHORUS SAMPLES,

ILLINOIS RIVER NEAR WATTS,OKLAHOMA

1965 1970 1975 1980 1985 1990 1995 2000 2005

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

0

1975 1980 1985 1990 1995 2000 2005

10,000

20,000

30,000

40,000

50,000

0

TOTAL PHOSPHORUS SAMPLES,

ILLINOIS RIVER NEAR TAHLEQUAH,

OKLAHOMA

YEAR

1975 1980 1985 1990 1995 2000 2005

0

4,000

8,000

TOTAL PHOSPHORUS

SAMPLES,

FLINT CREEK NEAR

KANSAS,

OKLAHOMA

1975 1980 1985 1990 1995 2000 2005

0

10,000

20,000

30,000

40,000

TOTAL PHOSPHORUS

SAMPLES, BARON FORK AT

ELDON,

OKLAHOMA

MEAN DAILY STREAMFLOW, IN CUBIC FEET PER SECOND

1995 1997 1999 2001 2003 2005 2007

TOTAL PHOSPHORUS

SAMPLES, ILLINOIS

RIVER AT

CHEWEY,

OKLAHOMA

EXPLANATION

Streamflow

Streamflow at time of

sampling

10,000

20,000

30,000

0
22 Summary of Surface-Water Quality Data from the Illinois River Basin in Northeast Oklahoma, 1970–2007

Figure 15. Total nitrogen concentration compared to mean daily streamflow for long-term water-quality monitoring sites in the Illinois 

River Basin in Oklahoma. 

10,000

FLINT CREEK NEAR KANSAS, OKLAHOMA,

1975–2007

1 10 100 1,000

6

8

10

4

2

0

10,000 0

MEAN DAILY STREAMFLOW, IN CUBIC FEET PER SECOND

ILLINOIS RIVER NEAR TAHLEQUAH,

OKLAHOMA, 1975–2007

10 100 1,000 100,000

1

2

3

4

5

6

7

8

9

10

10 100 1,000 10,000 100,000

1

2

3

4

ILLINOIS RIVER NEAR

WATTS,

OKLAHOMA,

1975–2007

0

5

TOTAL NITROGEN CONCENTRATION, IN MILLIGRAMS PER LITER

ILLINOIS RIVER AT CHEWEY, OKLAHOMA,

1997–2007

6

5

4

3

2

1

0

10 100 1,000 10,000 100,000 10,000

BARON FORK AT ELDON, OKLAHOMA,

1975–2007

10 100 1,000 100,000 0

1

2

3

4

5

1

6
Water Quality 23

Figure 16. Total phosphorus concentration compared to mean daily streamflow for long-term water-quality monitoring sites in the 

Illinois River Basin in Oklahoma. 

1

BARON FORK AT ELDON, OKLAHOMA,

1975–2007 0.001

0.1

0.01

0.0001

10

Oklahoma Scenic

Rivers Phosphorus

Standard

10,000 1 10 100 1,000 10,000 100,000

1

ILLINOIS RIVER AT CHEWEY, OKLAHOMA,

1996–2007

TOTAL PHOSPHORUS CONCENTRATION, IN MILLIGRAMS PER LITER

10 100 1,000

0.1

0.01

10

Oklahoma Scenic Rivers

Phosphorus Standard

100,000

10,000

1

ILLINOIS RIVER NEAR TAHLEQUAH,

OKLAHOMA,

1975–2007

MEAN DAILY STREAMFLOW, IN CUBIC FEET PER SECOND

10 100 1,000 100,000

0.1

0.01

0.001

0.0001

10

100

Oklahoma Scenic

Rivers Phosphorus

Standard

ILLINOIS RIVER NEAR WATTS,

OKLAHOMA, 1969–2007

10

10 100 1,000 10,000 100,000

1

0.1

0.01

0.001

Oklahoma Scenic Rivers Phosphorus Standard

10,000

1

FLINT CREEK NEAR KANSAS, OKLAHOMA,

1975–2007

10 100 1,000

0.1

0.01

10

Oklahoma Scenic Rivers

Phosphorus Standard
24 Summary of Surface-Water Quality Data from the Illinois River Basin in Northeast Oklahoma, 1970–2007

viruses that are not easily detected. Because of the potential 

for disease outbreaks from ingestion of bacteria by recreational users of streams, the State of Oklahoma set “primary 

body contact” limits of 400 colonies of fecal coliform bacteria, 235 colonies of Escherichia coli (E. coli) bacteria, and 

33 colonies of enterococci (a subgroup of fecal streptococci) 

as geometric means of 5 samples collected during 30 days 

(for Scenic Rivers) per 100 milliters (mL) of water (State of 

Oklahoma, 2006).

Bacteria and the nutrients nitrogen and phosphorus have 

similar patterns of occurrence in the Illinois River and neighboring Ozark Basins. Bacteria are detected generally in greatest abundance in agricultural areas, with more than 25 percent 

of surface-water samples in those areas containing fecal 

coliform bacteria at counts greater than 200 colonies/100 mL 

(Petersen and others, 1999a). 

Types of Bacteria Analyzed

Water samples collected from the Illinois River, Flint 

Creek, and Baron Fork were periodically analyzed by the 

USGS for fecal coliform, E. coli, and fecal streptococcal 

bacteria from 1993 to 2006. E. coli bacteria are a subgroup 

of fecal coliform bacteria that typically are detected in smaller 

counts than fecal coliform bacteria. Rates and timing of 

transport from the land surface to water bodies such as rivers and lakes can have substantial effects on fecal-indicator 

bacteria counts in those water bodies. Fecal-indicator bacteria, being acclimated to conditions in the digestive tracts of 

animals, tend to die-off with time after exiting the host animals 

in solid wastes. A study by Schumacher (2003) showed that 

E. coli in land-applied litter can survive in fields for as long 

as 8 weeks after application. Runoff soon after land application of animal manures is more likely to cause runoff of 

larger numbers of viable bacteria than runoff several weeks 

after such applications. Although fecal streptococcal bacteria 

generally are detected in smaller numbers than fecal coliform 

bacteria in animal wastes, fecal streptococcal bacteria tend 

to survive for longer periods of time outside of the hosts—as 

long as 20.1 days, as opposed to 13.4 days in soils for fecal 

coliform bacteria (Van Donsel and others, 1967; and Cohen 

and Shuval, 1972). Although fecal streptococcal bacteria 

tend to survive longer outside of the hosts, concerns about 

variability in their survival rates and in methodology used 

to culture this type of bacteria have led to greater reliance 

on counts of fecal coliform bacteria and enterococci (a 

subgroup of fecal streptococcal bacteria) to indicate possible 

contamination of water by fecal matter (Wilhelm and Maluk, 

1998).

Bacterial Abundance

Water quality in five stream segments in the Illinois 

River Basin, including the Illinois River, Flint Creek, and the 

Baron Fork have been listed as being impaired by elevated 

fecal streptococcal (enterococci) bacteria counts under section 

303d of the Clean Water Act (U.S. Environmental Protection 

Agency, 2007). Fecal coliform bacteria counts in water samples from the five stations summarized in this report generally 

ranged from 1 to 10,000 colonies per 100 mL (fig. 21). As 

with other constituents, apparent increases in bacteria counts 

after 1999 may be primarily artifacts of a change in sampling 

regime at that time that targeted sampling of six high-flow and 

six base-flow samples per year, compared to previous periodic sampling, that primarily sampled those sites at base-flow 

conditions.

Possible Sources of Bacteria

Humans, livestock, and wildlife comprise the major 

probable sources of fecal-indicator bacteria to the Illinois 

River and the tributaries. Whereas E. coli bacteria are believed 

to come only from the wastes of warm-blooded animals, fecal 

coliform bacteria can be derived from other sources, including effluents from paper mills, textile mills, and sugar beet 

processing (Dufour, 1976), but those sources are not present in 

the upstream parts of the Illinois River Basin. Viable bacteria from human wastes may be directly discharged to local 

streams from outfalls of municipal wastewater treatment plants 

or may seep from septic tanks through local soils into the 

karstic Springfield Plateau aquifer. Karstic aquifers, because 

Table 4. Trends of streamflow, and total nitrogen and phosphorus concentrations, loads, and flow-adjusted concentrations at long-term waterquality monitoring sites in the Illinois River Basin from 1997-2004 (Rebich and Demcheck, 2007).

Station name

Trends, in percent per year, by parameter

Streamflow

Total 

nitrogen 

concentration

Total 

nitrogen 

load

Flow-adjusted 

total nitrogen 

concentration

Total 

phosphorus 

concentration

Total 

phosphorus 

load

Flowadjusted total 

phosphorus 

concentration

Illinois River near Watts, Oklahoma -3.9 None -4.1 None 5.4 None 6.5

Flint Creek near Kansas Oklahoma -3.5 4.1 None 4.8 8.3 None 10

Baron Fork at Eldon, Oklahoma -4.5 None None 3.1 None None 5

Illinois River near Tahlequah, 

Oklahoma

-3.8 None None 2.0 5.4 None 9.4
Water Quality 25

of large interconnected voids, can have relatively small 

filtering ability, and can have relatively high ground-water 

flow rates from recharge areas to local streams (Lindsey and 

others, 2009). Rapidly-flowing groundwater is more likely to 

transport live bacteria to streams than groundwater that takes 

weeks, months, or years to seep from recharge areas to springs 

and streams. Wastes and entrained bacteria from livestock 

and wildlife typically are discharged in more diffuse manners 

(nonpoint source) than human wastes (point source), with livestock wastes being spread on land as fertilizers and through 

annual deposition on pastures.

Trends in Bacteria with Streamflow

Similar to phosphorus and nitrogen, increased amounts 

of fecal indicator bacteria are washed off of the land surface 

from soils and animal wastes during rainy periods, with bacteria counts generally increasing exponentially with streamflow 

in the Illinois River (fig. 22). If the sources of fecal indicator 

bacteria in the basin were primarily point sources, such as 

municipal wastewater treatment plants, then counts of those 

bacteria should decrease (be diluted) with increased streamflow. Upward trends of fecal indicator bacteria counts with 

Figure 17. Mean daily streamflow compared to chlorophyll-a concentration in water samples from long-term water-quality monitoring 

sites in the Illinois River Basin in Oklahoma. 

ILLINOIS RIVER NEAR WATTS,

OKLAHOMA,

1996–2003

0 NON-DETECTS

5

10

15

50 100 1,000 10,000

20

25

30

MEAN DAILY STREAMFLOW, IN CUBIC FEET PER SECOND

10

CHLOROPHYLL- IN PHYTOPLANKTON CONCENTRATION, IN MILLIGRAMS PER LITER A

BARON FORK AT ELDON, OKLAHOMA,

1996–2003

10,000

0

25

NONDETECTS

10

5

100 1,000

15

20

ILLINOIS RIVER NEAR TAHLEQUAH,

OKLAHOMA, 1996–2007

100,000

0

14

100

NON-DETECTS

12

8

4

1,000 10,000

5

FLINT CREEK NEAR KANSAS,

OKLAHOMA, 1996–2003

1,000 0 100

10

10

NONDETECTS

25

15

20
26 Summary of Surface-Water Quality Data from the Illinois River Basin in Northeast Oklahoma, 1970–2007

Figure 18. Total nitrogen concentration compared to chlorophyll-a concentration in water samples from long-term water-quality 

monitoring sites in the Illinois River Basin in Oklahoma. 

increasing streamflow indicate that nonpoint sources, such as 

urban and agricultural runoff, are more likely to be the major 

sources of these bacteria in the Illinois River as described 

in Storm and others (1996), Pickup and others (2003), and 

Tortorelli and Pickup (2006). The primary body contact standard for Oklahoma is shown on the graphs in figure 22 as a 

benchmark for bacteria counts that might pose risks to human 

health. The Oklahoma State standard is not a fixed number 

for any one sample, but rather a frequency of exceedances 

for a 30-day period. Specifically, no more than 10 percent 

of samples collected during 30-day periods shall exceed 400 

fecal coliform colonies per 100 mL of water (State of Oklahoma, 2006).

Fecal coliform bacteria counts at the five stations summarized in this report commonly exceeded the State of Oklahoma 

primary body contact standard of 400 colonies per 100 mL 

at stream discharges exceeding 1,000 ft3/sec. However, 

recreational activities that involve primary body contact with 

the water of this river are less likely to occur at higher flows, 

because of safety issues, than at base-flow conditions, when 

fecal coliform bacteria counts generally do not exceed the 

standard. 

Sediment

Sediment is composed of organic and inorganic particles 

of soils and other materials that are washed or blown into 

streams and lakes. Sediment naturally occurs in all streams, 

but the amounts of sediment running off to streams are 

ILLINOIS RIVER NEAR WATTS, OKLAHOMA,

1996–2003

0

NON-DETECTS

5

10

15

1.0 1.5 2.0 3.0 4.0 2.5 3.5 4.5

ILLINOIS RIVER NEAR TAHLEQUAH, OKLAHOMA,

1996–2007

4 0

14

0

NON-DETECTS

12

8

4

1 2 3

TOTAL NITROGEN CONCENTRATION, IN MILLIGRAMS PER LITER

10

CHLOROPHYLL- IN PHYTOPLANKTON CONCENTRATION, IN MILLIGRAMS PER LITER

A

BARON FORK AT ELDON, OKLAHOMA,

1996–2003

5 0

25

1

NON-DETECTS

0

5

2 3 4

15

20

5

FLINT CREEK NEAR KANSAS, OKLAHOMA,

1996–2003

4.5 0 3.0

10

1.5

NONDETECTS

20

15

2.0 2.5 3.5 4.0
Water Quality 27

increased by removing vegetation from the land surface 

by activities such as construction of buildings and roads, 

plowing of cropland, overgrazing of pastures, cutting of 

timber, and fires. More intense development of land for 

either urban or agricultural purposes typically increases 

yields of sediment per unit of land area in river basins. 

Increased concentrations of suspended sediment in streams 

can degrade habitat and spawning ground for fish and 

amphibians by: (a) increasing water temperatures, (b) reducing dissolved oxygen in water, (c) reducing visibility for 

predator species, and (d) infilling gravel on streambeds used 

for spawning. Increased sediment loads also can increase 

scouring of bridges and streambanks, fill up downstream 

reservoirs, and reduce the aesthetic value of recreational 

streams.

Types of Suspended Sediment

Suspended sediment is composed of two major types 

of sediment—organic and inorganic. Organic sediments are 

composed of fragments of terrestrial and aquatic plants and 

animals, organic matter from topsoil, and animal wastes. Inorganic sediments generally are composed of fragments of rocks 

and minerals dominated by silica (such as quartz and clays) or 

carbonate (such as calcite and dolomite).

Relations of Sediment with Streamflow and 

Phosphorus Concentrations

Suspended sediment concentrations in the Illinois River 

tend to increase exponentially with streamflow (fig. 23), 

Figure 19. Total phosphorus concentration compared to chlorophyll-a concentration in water samples from long-term water-quality 

monitoring sites in the Illinois River Basin in Oklahoma. 

TOTAL PHOSPHORUS CONCENTRATION, IN MILLIGRAMS PER LITER

1

CHLOROPHYLL- IN PHYTOPLANKTON CONCENTRATION, IN MILLIGRAMS PER LITER

A

BARON FORK AT ELDON, OKLAHOMA,

1996–2003

1

0.1

0.1

10

0.01

NON-DETECTS

0.001

1

ILLINOIS RIVER NEAR WATTS, OKLAHOMA,

1996–2003

1

0.1

0.1

10

0.01

100

NON-DETECTS

1

ILLINOIS RIVER NEAR TAHLEQUAH,

OKLAHOMA,

1996–2007

1

0.1

0.1

10

0.01

NON-DETECTS

1

FLINT CREEK NEAR KANSAS, OKLAHOMA,

1996–2003

1

0.1

0.1

10

0.01

NON-DETECTS

100
28 Summary of Surface-Water Quality Data from the Illinois River Basin in Northeast Oklahoma, 1970–2007

because of flushing of sediments from the land surface by 

rainfall and resuspension of streambed sediments by fasterflowing water during runoff. Phosphorus typically is strongly 

sorbed to oxides of iron, manganese, and aluminum in soils 

(Van Riemsdijk and others, 1984; Hamad and others, 1992; 

and Hem, 1992), but that sorptive capacity for phosphorus 

can be overwhelmed through application of phosphorus-rich 

animal wastes (Siddique and Robinson, 2003). Because of 

relatively large phosphorus concentrations in animal wastes 

deposited at the land surface and sorption of phosphorus to 

metallic minerals in soil particles, phosphorus is transported 

primarily by runoff of animal wastes and soil particles on or 

near the land surface, as shown by increasing total phosphorus 

concentrations in the Illinois River with increasing suspended 

sediment concentrations (and greater streamflows) (fig. 24). 

Total phosphorus concentrations generally increased with 

Figure 20. Filamentous periphyton algae growing on streambed rocks at a) Flint Creek north of New Hope Ranch, and b) Baron Fork 

near Eldon, Oklahoma (W.J. Andrews photographs U.S. Geological Survey, August 2003).. 
Water Quality 29

Figure 21. Fecal coliform bacteria counts with time for long-term water-quality monitoring sites in the Illinois River Basin in Oklahoma. 

1996 0.1 1997 1998 1999 2000 2001 2002 2003

Illinois River near Watts, Oklahoma,

1996–2003

1

10

100

1,000

10,000

100,000

Oklahoma Primary

Body Contact Limit

0.1

1

10

100

1,000

10,000

100,000

Oklahoma

Primary Body

Contact

Limit

1996

Flint Creek near Kansas, Oklahoma,

1996–2003

1997 1998 1999 2000 2002 2001 2003

Illinois River near Tahlequah, Oklahoma,

1993–2006

1993

1,000

YEAR

1995 1997 1999 2001 2003 2005

100

10

1

0.1

10,000

100,000

Oklahoma

Primary

Body

Contact

Standard

0.1

1

10

100

1,000

10,000

100,000

FECAL COLIFORM BACTERIA COUNTS, IN COLONIES PER 100 MILLILITERS

Oklahoma

Primary Body

Contact Limit

1996

Illinois River at Chewey, Oklahoma,

1996–2006

1998 2000 2002 2004 2006

Baron Fork at Eldon,

Oklahoma, 1994–2004

0.1

1

10

100

1,000

10,000

100,000

Oklahoma Primary

Body Contact Limit

1994 1996 1998 2000 2002 2004
30 Summary of Surface-Water Quality Data from the Illinois River Basin in Northeast Oklahoma, 1970–2007

Figure 22. Fecal coliform bacteria counts compared to streamflow for long-term water-quality monitoring sites in the Illinois River 

Basin in Oklahoma. 

10

Illinois River near Watts, Oklahoma,

1996–2003

10

100 1,000 10,000 100,000

1

0.1

100

1,000

10,000

100,000

Oklahoma

Primary

Body

Contact

Standard

10

Illinois River at Chewey, Oklahoma,

1996–2006

FECAL COLIFORM BACTERIA COUNTS, IN COLONIES PER 100 MILLILITERS

100 1,000 10,000

10

1

0.1

100

1,000

10,000

100,000

Oklahoma

Primary

Body

Contact

Standard

100,000

10

Illinois River near Tahlequah, Oklahoma,

1993–2006

MEAN DAILY STREAMFLOW, IN CUBIC FEET PER SECOND

100 1,000 10,000 100,000

10

1

0.1

100

1,000

10,000

100,000

Oklahoma

Primary

Body

Contact

Standard

10

Flint Creek near Kansas, Oklahoma,

1996–2003

100 1,000 10,000

10

1

0.1

100

1,000

10,000

100,000

Oklahoma Primary

Body Contact

Standard

10

Baron Fork at Eldon, Oklahoma,

1994–2004

100 1,000 10,000

10

1

0.1

100

1.000

10.000

100.000

Oklahoma Primary

Body Contact

Standard

100,000
Water Quality 31

Figure 23. Suspended sediment concentration compared to mean daily streamflow for long-term water-quality monitoring sites in the 

Illinois River Basin in Oklahoma. 

10 100 1,000 10,000 100,000

10

ILLINOIS RIVER NEAR

WATTS, OKLAHOMA,

1965–2007

1

100

1,000

1 100 1,000 10,000 100,000

MEAN DAILY STREAMFLOW, IN CUBIC FEET PER SECOND

1

ILLINOIS RIVER NEAR

TAHLEQUAH, OKLAHOMA,

1955–2007

0.1

10

100

1,000

0.1 10

1 100 1,000 10,000

1

FLINT CREEK NEAR KANSAS,

OKLAHOMA, 1991–2007

0.1

10

100

1,000

10

10,000

100 1,000 100,000

1

BARON FORK NEAR ELDON,

OKLAHOMA,1994–2007

0.1

10

100

10,000

10 10,000

1,000

100 1,000 100,000 1

SUSPENDED SEDIMENT CONCENTRATION, IN MILLIGRAMS PER LITER

1

ILLINOIS RIVER AT

CHEWEY, OKLAHOMA,

1991–2007

0.1

10

100

1,000

10 10,000
32 Summary of Surface-Water Quality Data from the Illinois River Basin in Northeast Oklahoma, 1970–2007

Figure 24. Suspended sediment concentration compared to total phosphorus concentration for long-term water-quality monitoring 

sites in the Illinois River Basin in Oklahoma. 

1

FLINT CREEK NEAR KANSAS,

OKLAHOMA, 1996–2007

0.1

10

0.01

0.1 100101 1,000 10,000

10,000

1

BARON FORK NEAR ELDON,

OKLAHOMA, 1994–2007

101 100

0.1

0.01

0.1 1,000

10

0.001

1,000

1

TOTAL PHOSPHORUS CONCENTRATION, IN MILLIGRAMS PER LITER

ILLINOIS RIVER AT CHEWEY,

OKLAHOMA, 1999–2007

1 10 100

0.1

0.01

0.1

1,000

1

ILLINOIS RIVER NEAR WATTS,

OKLAHOMA, 1965–2007

1 10 100

0.1

10

0.01

1,000

SUSPENDED SEDIMENT CONCENTRATION, IN MILLIGRAMS PER LITER

1

ILLINOIS RIVER NEAR TAHLEQUAH,

OKLAHOMA,1975–2007

1 10 100

0.1

10

0.01

0.001
References Cited 33

suspended sediment concentrations greater than 20 milligrams 

per liter (fig. 24), corresponding to streamflows of about 150 

ft3/sec at both the Illinois River near Watts and the Illinois 

River near Tahlequah, Oklahoma, stations (fig. 23) These 

phosphorus increases indicate that higher streamflows transport most of the annual yield of sediment and phosphorus in 

the lower half of the Illinois River Basin.

Summary

The Illinois River Basin of northwestern Arkansas and 

northeastern Oklahoma is composed of 1,653 square miles 

of land area, about half of that is devoted to grazing of cattle 

and horses. Approximately 20 million birds, mostly broiler 

chickens, are also raised in the basin at any given time. Wastes 

generated by rapid growth in human populations in parts of 

the basin are additional potential sources of nutrients and 

bacteria. Those sources of nutrients and bacteria, combined 

with the relatively high vulnerability of water in the basin to 

contamination because of the karstic setting, have combined to 

increase contamination of local streams by nutrients, bacteria, 

and sediments.

Whereas the upstream half of the basin has a rapidly 

growing economy of livestock-based agriculture and has had 

rapid growth in human population because of growth of large 

corporate headquarters, a state university, and retirement 

communities, the downstream half of the basin is less intensively developed, relying on water-based recreation in scenic 

rivers and Lake Tenkiller as a large part of the local economy. 

In addition to aesthetic issues possibly reducing tourism, 

numerous cities, towns, and smaller entities in both states 

rely on surface water for drinking-water supplies, or on 

groundwater from wells near to streams that can be affected 

by degraded surface-water quality. Many streams in the area 

may be phosphorus-limited, meaning that relatively small 

additions of phosphorus may notably increase growth of 

algae. Phosphorus typically is sorbed to soil and sediments on 

streambeds, so phosphorus tends to wash into local streams 

or be resuspended into local water bodies in greatest amounts 

during storm runoff/high streamflow. Bacteria from animal 

wastes also tend to increase greatly in local streams during 

high streamflows, similarly being washed from land surfaces 

by rainfall.

General-water chemistry, concentrations of nitrogen and 

phosphorus compounds, chlorophyll-a (an indicator of algal 

biomass), and fecal-indicator bacteria generally were similar 

between the five sampling sites. Most water samples were 

phosphorus-limited, meaning that they contained a smaller 

proportion of phosphorus, relative to nitrogen, than typically 

occurs in algal tissues. Greater degrees of nitrogen limitation 

occurred at three of the five sites which were sampled back to 

the 1970s, probably due to use of detergents containing greater 

concentrations of phosphorus than in subsequent periods. 

Concentrations of nitrogen, phosphorus, and sediment, and 

counts of fecal-indicator bacteria generally increased with 

streamflow at the five sites, probably due to runoff from 

the land surface and re-suspension of streambed sediments. 

Phosphorus concentrations typically exceeded the Oklahoma 

standard of 0.37 milligrams per liter for Scenic Rivers. Concentrations of chlorophyll-a in phytoplankton in water samples 

collected at the five sites were not well correlated with 

streamflow, nor to concentrations of the nutrients nitrogen and 

phosphorus, probably because much of the algae growing in 

these streams are periphyton attached to streambed cobbles 

and other debris, rather than phytoplankton in the water 

column. Sediment concentrations correlated with phosphorus 

concentrations in water samples collected at the sites, probably 

due to sorption of phosphorus to soil particles and streambed 

sediments and runoff of soils and animal wastes at the land 

surface and resuspension of streambed sediments during highflow periods. Fecal coliform bacteria counts at the five sites 

sometimes exceeded the Oklahoma Primary Body Contact 

Standard of 400 colonies per 100 milliliters when streamflows 

were greater than 1,000 cubic feet per second.

Ultimately, Lake Tenkiller receives the compounds that 

runoff the land surface or seep to local streams from groundwater in the basin. Lakes are more likely than streams to suffer 

from notable degradation by algal growth (eutrophication) 

because of not having sufficient flow to wash such organisms 

downstream. The environments of flowing streams, however, 

are not immune to the effects of nutrient enrichment and algal 

growth. Nutrient enrichment of streams or lakes can cause 

eutrophication that: (a) discolors and clouds water (reducing 

feeding of predator fish), (b) decreases dissolved oxygen concentrations in water as part of algal respiration and plant-tissue 

decay, (c) increases sedimentation (filling in lakes and gravel 

spawning beds), (d) emits organic chemicals that cause taste 

and odor in water and can be toxic, (e) decreases diversity of 

aquatic species, and (f) changes the dominant aquatic biota.

Long-term storage of phosphorus in soils in the basin and 

in streambed and lakebed sediments may continue to provide 

phosphorus to local streams for decades to come, but steps are 

being taken to reduce local discharges of phosphorus, including upgrades in capacity and effectiveness of municipal wastewater treatment plants, and exporting phosphorus-rich poultry 

litter out of the basin.

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Glossary

aquatic Life forms or substances in water.

aquifer A geologic formation, group of formations, or part 

of a formation that contains sufficient saturated permeable 

material to yield large quantities of water to wells and springs 

(New Mexico Office of State Engineer, 1999).

base flow Streamflow derived from ground-water seepage, 

synonymous with “low flow”.

climate The sum total of the meteorological elements that 

characterize the average and extreme condition of the atmosphere during a long period of time at any one place or region 

of the earth’s surface (Langbein and Iseri, 1960).

concentration The mass of a substance dissolved per unit 

volume of liquid or contained in a unit mass of solid.

conduit A natural or manmade channel through that substances can be conveyed. In the context of karstic hydrology, 

a conduit is a cavernous channel eroded during centuries in 

carbonate rocks that readily conveys groundwater at relatively 

rapid flow rates.

criterion A number or narrative statement assigned to protect a designated beneficial use. A water-quality standard set 

by the state.

cubic feet per second A unit expressing rates of discharge. 

One cubic foot per second is equal to the discharge of a stream 

of rectangular cross section, 1 foot wide and 1 foot deep, with 

water flowing at an average velocity of 1 foot per second 

(Langbein and Iseri, 1960). 

datum A point, line, or surface used as a reference, such as 

in surveying.

ecosystem A natural unit including all life forms and nonliving physical elements that function together.

eutrophication Nutrient enrichment (particularly of nitrogen 

and phosphorus) in aquatic ecosystems that leads to increased 

productivity, including excessive growth of algae and other 

aquatic plants (Graham and others, 2008). Excessive eutrophication changes aquatic habitat by changes in dissolved oxygen 

concentration, water temperature, availability of spawning 

beds, and visibility for predator fish. Aesthetic effects of 

hypereutrophication include degradation of water quality for 

swimming and other recreational activities and increases in 

concentrations of taste-and-odor-producing organic compounds in drinking water.

fecal-indicator bacteria Bacteria that typically are found 

in digestive tracts of warm-blooded animals. Large numbers 

of these bacteria per unit of water indicate runoff or seepage of feces into streams and lakes and greater potential for 

pathogenic (disease-causing) microorganisms to be detected in 

water.

flow-adjusted A mean concentration of a constituent in 

water obtained by dividing the load of a constituent flowing 

down a stream in a period of time divided by the total stream 

flow during that period of time.

gage A device used to measure and record the elevation 

of water in a stream or lake in a semi-continuous manner. In 

a flowing stream, comparisons of measured streamflows to 

surface-water elevations are used to estimate streamflow, commonly at 15-minute intervals.

gage height The water-surface elevation referred to some 

arbitrary gage datum. Gage height is often used interchangeably with the more general term stage although gage height 

is more appropriate when used with a reading on a gage 

(Langbein and Iseri, 1960).

hydrograph A graph showing stage, flow, velocity, or other 

properties of water with respect to time (Langbein and Iseri, 

1960).

karst Topography that is formed on limestone, dolomite, 

gypsum beds, and other rocks by dissolution and is characterized by closed depressions, sinkholes, caves, and underground 

streams (modified from New Mexico Office of State Engineer, 

1999).

load The mass of a substance flowing past a given point in a 

stream per unit of time, derived from multiplying streamflow 

by the aqueous concentration of a substance by unit correction 

factors. Loads are typically expressed in pounds or kilograms 

per day.

milliequivalents per Liter (meq/L) The amount of material 

that will release or react with a millimole of electrical charges 

on particles such as OH-, H+, or electrons. Milliequivalents 

per Liter are computed by multiplying the concentration of an 

ionic substance by the atomic mass of the ionic substance and 

the charge of the ion.

milligrams per liter (mg/L) Milligrams of a substance 

dissolved in one liter of water, that is the same as a part per 

million in freshwater because one liter of distilled water 

weighs one million milligrams (one kilogram). This measure 

is equivalent to parts per million (ppm) (Colorado Geological 

Survey, 2008).

molar ratio Ratio of moles of two compounds with moles 

being determined by dividing concentrations by the molar 

weight (sum of atomic weights) of a substance.

nonpoint source A source of contaminant(s) discharged 

over a wide land area that runs off or seeps to streams, lakes 

and oceans, such as runoff from streets, parking lots, lawns, 

agricultural land, individual septic systems, and construction 

sites (modified from New Mexico Office of State Engineer, 

1999).

Glossary
Glossary 39

nutrient An element such as nitrogen or phosphorus needed 

for growth of plants and animals.

nutrient limitation A nutrient is considered to be limited if 

that nutrient is not available in sufficient quantities to support 

plant and animal growth. Additions of limited nutrients can 

cause rapid growth of algae and other aquatic organisms in 

streams and lakes.

periphyton A mixture of algae, cyanobactor, bacteria, and 

detritus which is attached to submerged surfaces in aquatic 

systems.

phytoplankton Microscopic plants, primarily algae that are 

suspended in the water columns of aquatic systems.

point source The source of contaminant(s) discharged from 

any identifiable point, including wastewater discharges from 

ditches, channels, sewers, tunnels and containers of various 

kinds (New Mexico State Office of Engineer, 2005).

precipitation Includes atmospheric hail, mist, rain, sleet 

and snow that descend upon the earth; the quantity of water 

accumulated from these events (New Mexico Office of State 

Engineer, 1999).

primary body contact recreation criteria Water-quality 

criteria set by the state to protect humans having direct body 

contact with the water where a possibility of ingestion exists, 

swimming being one example.

recharge Addition of water to an aquifer by infiltration, 

either directly into the aquifer or indirectly through another 

rock formation. Recharge may be natural, as when precipitation infiltrates to the water table, or artificial, as when water 

is injected through wells or spread over permeable surfaces 

for the purpose of recharging an aquifer (modified from New 

Mexico Office of State Engineer, 1999).

runoff That part of the precipitation that appears in surface 

streams (Langbein and Iseri, 1960).

secondary body contact recreation criteria Water-quality 

criteria set by the state to protect humans from having indirect 

body contact with the water where a possibility of ingestion 

exists, such as boating and fishing.

sediment Fragmented rock and organic materials that are 

transported by, suspended in, or deposited by water or air. 

Sediments tend to accumulate in horizontal layers/beds in still 

or slow-flowing water.

streamflow Discharge in a natural channel of a surface 

stream course (New Mexico Office of State Engineer, 1999). 

surrogate In hydrology, a water-quality or other constituent used to predict the concentration or occurrence of another 

water-quality constituent.

sustainability A decision-making concept describing development that meets the needs of the present generation without 

compromising the ability of future generations to meet their 

needs (modified from New Mexico Office of State Engineer, 

1999).

total nitrogen The sum of concentrations of ammonium, 

nitrate, nitrite, and organic forms of nitrogen, expressed as the 

concentration of nitrogen, in a water sample.

total phosphorus The sum of concentrations of phosphorus in the forms of orthophosphate (PO4

-3), polyphosphate 

(phosphate polymers linked by hydroxyl (OH-) groups and 

hydrogen atoms), organically bound phosphate (OP(OR)3), 

and other forms of phosphorus, expressed as the concentration 

of phosphorus, in a water sample.

wastewater Water that contains dissolved or suspended 

solids as a result of human use (New Mexico Office of State 

Engineer, 1999).

wastewater treatment Processing of wastewater for the 

removal or reduction in the concentration of dissolved solids 

or other undesirable constituents (modified from New Mexico 

Office of State Engineer, 1999).

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