U.S. Geological Survey

Water-Resources Investigations Report

U.S. Department of the Interior

Phosphorus Concentrations, Loads, and Yields

in the Illinois River Basin, Arkansas and

Oklahoma, 1997-2001

03-4168

Prepared in cooperation with the

OKLAHOMA SCENIC RIVERS COMMISSION

OKLAHOMA WATER RESOURCES BOARD

Photograph by Edward H. Fite, III, Oklahoma Scenic Rivers Commission
U.S. Geological Survey

Water-Resources Investigations Report

U.S. Department of the Interior

Phosphorus Concentrations, Loads, and Yields

in the Illinois River Basin, Arkansas and

Oklahoma, 1997-2001

By Barbara E. Pickup1, William J. Andrews1, Brian E. Haggard2, and W. Reed Green1

03–4168

Prepared in cooperation with the

OKLAHOMA SCENIC RIVERS COMMISSION

OKLAHOMA WATER RESOURCES BOARD

1

U.S. Geological Survey

2

U.S. Department of Agriculture
Pickup, B.E., and others—Phosphorus Concentrations, Loads, and Yields in the Illinois River Basin, Arkansas and Oklahoma, 1997-2001—USGS/WRIR 03–4168

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iii

Contents

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

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

Purpose and scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Study area description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Streamflow in the Illinois River basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Phosphorus concentrations, loads, and yields in the Illinois River basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Concentrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Estimated annual loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Estimated seasonal loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Yields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Estimated mean flow-weighted concentrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Estimated phosphorus loads into Lake Tenkiller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

References cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Appendixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

1a. Instantaneous streamflows and total phosphorus concentrations for Illinois River near

Watts, Oklahoma, from 1997-2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

1b. Instantaneous streamflows and total phosphorus concentrations for Flint Creek near

Kansas, Oklahoma, from 1997-2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

1c. Instantaneous streamflows and total phosphorus concentrations for Illinois River

at Chewey, Oklahoma, from 1997-2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

1d. Instantaneous streamflows and total phosphorus concentrations for Illinois River near

Tahlequah, Oklahoma, from 1997-2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

1e. Instantaneous streamflows and total phosphorus concentrations for Baron Fork

at Eldon, Oklahoma, from 1997-2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

2. Residuals plots of In(instantaneous load) – In(predicted load) in relation to In(instananeous load)

for stations in the Illinois River basin, periods 1997-1999, 1998-2000, and 1999-2001 . . . . . . . . . . . . 37

Figures

1–2. Maps showing:

1.TheIllinoisRiverbasin,Oklahoma,withlocationsofsurface-waterandwater-quality

stations in the basin and of towns with wastewater-treatment facilities that discharge

into streams in the basin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.LanduseandaveragedpercentageofphosphorusloadsintheIllinois

River basin, Oklahoma. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

3.Graph showing streamflowdivided into totalflow andbase flow, andbase-flow andrunoff

water samples collected at water-quality stations in the Illinois River basin,

Oklahoma, 1997-2001. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

4.Scatterplotsshowingphosphorusconcentrationsfrombase-flowandrunoffwatersamples

collected at water-quality stations in the Illinois River basin, Oklahoma, 1997-2001 . . . . . . . . . . . . . . . . 11
iv

5–7. Boxplots showing:

5.Distributionsofbase-flowphosphorusconcentrationsfromwatersamplescollected

at water-quality stations in the Illinois River basin, Oklahoma, periods 1997-1999,

1998-2000, and 1999-2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

6.Distributionsofrunoffphosphorusconcentrationsfromwatersamplescollected

at water-quality stations in the Illinois River basin, Oklahoma, periods 1997-1999,

1998-2000, and 1999-2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

7. Instantaneous phosphorus concentrations from water samples collected at waterquality stations in the Illinois River basin, Oklahoma, periods 1997-1999, 1998-2000,

and 1999-2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Tables

1. Station information and streamflow statistics for surface-water water-quality stations in the

Illinois River basin, Oklahoma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2. Summary statistics of phosphorus concentrations from base-flow and runoff water samples

collected at water-quality stations in the Illinois River basin, Oklahoma, periods 1997-1999,

1998-2000, and 1999-2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3. Mann-Whitney rank-sum test results comparing base-flow phosphorus

concentrations to runoff phosphorus concentrations from water samples collected

at water-quality stations in the Illinois River basin, Oklahoma, periods 1997-1999, 1998-2000,

and 1999-2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

4. Regression models developed using total phosphorus concentrations from water samples and

streamflows collected at water-quality stations in the Illinois River basin, Oklahoma, periods

1997-1999, 1998-2000, and 1999-2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

5. Mean annual phosphorus loads and yields estimated from phosphorus concentrations in water

samples collected at water-quality stations in the Illinois River basin, Oklahoma, periods

1997-1999, 1998-2000, and 1999-2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

6. Number of days of base flow and runoff designated by Base-Flow Index (BFI) program at waterquality stations in the Illinois River basin, Oklahoma, periods 1997-1999, 1998-2000, and 1999-2001 . .17

7. Seasonal phosphorus loads estimated from phosphorus concentrations in water samples

collected at water-quality stations in the Illinois River basin, Oklahoma, periods 1997-1999,

1998-2000, and 1999-2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

8. Mean annual phosphorus loads, mean annual streamflows, and mean flow-weighted

phosphorus concentrations for water-quality stations in the Illinois River basin, Oklahoma,

periods 1997-1999, 1998-2000, and 1999-2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

9. Summary of phosphorus loads to Lake Tenkiller, Oklahoma, periods 1997-1999, 1998-2000,

and 1999-2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
v

Conversion Factors and Datum

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F = (1.8 × °C) + 32

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C = (°F - 32) / 1.8

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).

Elevation, as used in this report, refers to distance above or below NAVD 88.

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

Multiply By To obtain

square mile (mi2) 2.590 square kilometer (km2)

cubic foot per second (ft3

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

pound (lb) 0.4536 kilogram (kg)

pound per day (lb/d) 0.4536 kilogram per day (kg/d)

pound per year (lb/yr) 0.4536 kilogram per year (kg/yr)

pound per year per square mile

(lb/yr/mi2) 0.17514

kilogram per year per square kilometer

(kg/yr/(km2)
Phosphorus Concentrations, Loads, and Yields in the

Illinois River Basin, Arkansas and Oklahoma, 1997-2001

By Barbara E. Pickup, William J. Andrews, Brian E. Haggard, and W. Reed Green

Abstract

The Illinois River and tributaries, Flint Creek and the

Baron Fork, are designated scenic rivers in Oklahoma. Recent

phosphorus increases in streams in the basin have resulted in the

growth of excess algae, which have limited the aesthetic benefits of water bodies in the basin, especially the Illinois River and

Lake Tenkiller. The Oklahoma Water Resources Board has

established a standard for total phosphorus not to exceed the 30-

day geometric mean concentration of 0.037 milligram per liter

in Oklahoma Scenic Rivers. Data from water-quality samples

from 1997 to 2001 were used to summarize phosphorus concentrations and estimate phosphorus loads, yields, and flowweighted concentrations in the Illinois River basin.

Phosphorus concentrations in the Illinois River basin generally were significantly greater in runoff-event samples than in

base-flow samples. Phosphorus concentrations generally

decreased with increasing base flow, from dilution, and

increased with runoff, possibly because of phosphorus resuspension, stream bank erosion, and the addition of phosphorus

from nonpoint sources.

Estimated mean annual phosphorus loads were greater at

the Illinois River stations than at Flint Creek and the Baron

Fork. Loads appeared to generally increase with time during

1997-2001 at all stations, but this increase might be partly

attributable to the beginning of runoff-event sampling in the

basin in July 1999. Base-flow loads at stations on the Illinois

River were about 10 times greater than those on the Baron Fork

and 5 times greater than those on Flint Creek. Runoff components of the annual total phosphorus load ranged from 58.7 to

96.8 percent from 1997-2001. Base-flow and runoff loads were

generally greatest in spring (March through May) or summer

(June through August), and were least in fall (September

through November).

Total yields of phosphorus ranged from 107 to 797 pounds

per year per square mile. Greatest yields were at Flint Creek

near Kansas (365 to 797 pounds per year per square mile) and

the least yields were at Baron Fork at Eldon (107 to 440 pounds

per year per square mile).

Estimated mean flow-weighted concentrations were more

than 10 times greater than the median and were consistently

greater than the 75th percentile of flow-weighted phosphorus

concentrations in samples collected at relatively undeveloped

basins of the United States (0.022 milligram per liter and 0.037

milligram per liter, respectively). In addition, flow-weighted

phosphorus concentrations in 1999-2001 at all Illinois River

stations and at Flint Creek near Kansas were equal to or greater

than the 75th percentile of all National Water-Quality Assessment program stations in the United States (0.29 milligram per

liter).

The annual average phosphorus load entering Lake Tenkiller was about 577,000 pounds per year, and more than 86 percent of the load was transported to the lake by runoff.

Introduction

The Oklahoma Scenic Rivers Act of 1969 designated the

Illinois River in northeastern Oklahoma (fig. 1) a ‘Scenic River’

to protect water quality and preserve fish, wildlife, and outdoor

recreational values for the benefit of the people of Oklahoma

and visitors to the state. The Oklahoma Scenic Rivers Commission (OSRC) was created in 1977 to enforce the stipulations of

this Act. A 1981 supplement to the Oklahoma Scenic Rivers

Act designated Flint Creek and Baron Fork, two Illinois River

tributaries, as scenic rivers (Oklahoma Statutes, Title O.S.

Supp. 1981, Sec. 1451).

Streams in the Illinois River basin are used for primary

body contact recreation (in which there is a possibility of human

ingestion of water) and fisheries. Water from these streams also

is used for public and private water supply and non-irrigation

agriculture (Oklahoma Water Resources Board, 2000). About

350,000 tourists spend an estimated $9 million per year in the

basin (Linda Loucks, Oklahoma Water Resources Board, written commun., 2001). The Illinois River flows into Tenkiller

Ferry Lake (referred to as Lake Tenkiller). An estimated $16.5

million is generated annually by about 1,500,000 visitors per

year to the area around this lake (John Marnell, U.S. Army

Corps of Engineers, written commun., 2001).

Phosphorus can enter streams in discharges from wastewater-treatment plants (point-source components) and in agricultural and urban runoff (nonpoint-source components) (Okla-
2 Phosphorus Concentrations, Loads, and Yields in the Illinois River Basin, Arkansas and Oklahoma, 1997-2001

homa Water Resources Board, 2002b). Streams in the Illinois

River basin are susceptible to potentially large concentrations

of phosphorus from both types of sources. Total phosphorus

(referred to as phosphorus) is the concentration of dissolved

phosphorus and particulate phosphorus in the sample. Elevated

phosphorus concentrations may promote algae growth in

streams (Sharpley, 1995), and are associated with accelerated

eutrophication of lakes (Daniel and others, 1998). Recent phosphorus increases in streams in the basin have resulted in the

growth of excess algae, which have reduced the aesthetic benefits of water bodies in the basin, especially the Illinois River and

Lake Tenkiller (Oklahoma Water Resources Board, 2002a).

The recreation-based economy of the area relies on maintenance of aesthetically pleasing water quality in the Illinois

River basin.

The 1998 Federal Clean Water Action Plan directs the

states, in conjunction with the U.S. Environmental Protection

Agency (USEPA), to develop numeric criteria for nutrients,

including phosphorus. Oklahoma Water Resources Board

(OWRB) has established a standard, which will be fully implemented by the year 2012, for total phosphorus concentration not

to exceed the 30-day geometric mean concentration of 0.037

milligram per liter (mg/L) in Oklahoma Scenic Rivers. That

standard is based on the 75th percentile of flow-weighted total

phosphorus concentrations from streams draining 85 relatively

undeveloped basins from across the United States (referred to as

relatively undeveloped basins of the United States) selected

from three programs of the USGS — the Hydrologic Benchmark Network, the National Water-Quality Assessment program (NAWQA), and the Research Program (Clark and others,

2000).

The NAWQA program, initiated by the USGS in 1991, is

a primary source for long-term, nationwide information on the

quality of streams, ground water, and aquatic ecosystems. The

information gathered through the program supports national,

regional, state, and local decision making and policy formation

for water-quality management (Gilliom and others, 2001).

Long-term goals of the program are to describe the status and

trends in the quality of the Nation’s surface- and ground-water

resources and determine the natural and anthropogenic factors

affecting water quality (Gilliom and others, 1995).

Historical water-quality data collection in the Illinois

River basin has been biased towards sampling during base-flow

(non-runoff) conditions. Because of insufficient historic sampling during runoff events, calculations using historic data may

have underestimated true phosphorus concentrations, loads, and

yields. In July 1999, the U.S. Geological Survey (USGS), in

cooperation with the OSRC and the OWRB, supplemented

fixed period, bimonthly water-quality sampling with six runoffevent samplings per year to better determine water quality over

the range of streamflows in the basin.

Purpose and Scope

The purpose of this report is to summarize phosphorus

concentrations and provide estimates of phosphorus loads,

yields, and flow-weighted concentrations in the Illinois River

and tributaries, Flint Creek and the Baron Fork, from January

1997 through December 2001. Phosphorus concentrations are

compared among stations in the Illinois River basin, to those

measured at relatively undeveloped basins of the United States,

and to those measured at all USGS NAWQA program stations.

Phosphorus loads are computed using LOADEST2, a program

to compute mean constituent loads in rivers using the ratingcurve method. LOADEST2 uses instantaneous phosphorus

concentrations and mean daily streamflows to estimate annual

and seasonal (spring, summer, fall, and winter) average phosphorus loads for the study period (Crawford, 1999). This report

comprises a preliminary analysis of data collected for a multiyear monitoring program.

Study Area Description

The Illinois River basin is about equally divided between

northeastern Oklahoma and northwestern Arkansas (fig. 1). The

basin is in the southwestern portion of the Ozark Plateaus physiographic province (Fenneman, 1938), and is underlain by the

cherty limestone of the Springfield Plateau aquifer (Adamski

and others, 1995; Renken, 1998).

The basin is dominated by about equal proportions of agricultural and forested land uses and is interspersed with minor

amounts of industrial, mining, and urban land uses (fig. 2).

Livestock production is the primary form of agriculture in the

basin. About 48 percent of agricultural land use in the basin is

pasture for cattle and horses. Numerous large-scale poultry and

swine production facilities are in the basin and poultry and

swine manures are used to fertilize pastures (Sims and Wolf,

1994). There also are several municipal wastewater-treatment

plants that discharge phosphorus-containing wastewater to the

river or tributaries (Oklahoma Water Resources Board, 2002b;

figs. 1 and 2).

 Streams in the Illinois River basin are susceptible to

potentially large concentrations of phosphorus from point

sources (such as wastewater-treatment plants) and nonpoint

sources (such as runoff from fertilized pastures). Phosphorus

concentrations in Ozark streams typically are greater in streams

draining agricultural lands than in those draining forested lands

(Petersen and others, 1998, 1999), because runoff from pastures

fertilized with animal manure probably are substantial sources

of phosphorus to the rivers in this basin (Arkansas Department

of Environmental Quality, 2000). Streams receiving municipal

wastewater from treatment plants can have phosphorus concentrations substantially greater than those in streams draining

agricultural areas (Petersen and others, 1998, 1999). The Illinois River and Flint Creek (fig. 2) receive discharges from

wastewater treatment plants, whereas the Baron Fork does not.

Streamflow in the Illinois River Basin

Streamflow in the Illinois River basin was highly variable

and generally increased with basin drainage area (table 1, fig.
Introduction 3

Flin t C re e k

Ill ni o si R vi e r

C ane y C reek

B aron Fo rk

Lake

Tenkiller

Lake

Frances

O s a g e

C reek

Rogers

Westville

Tahlequah

Springdale

Fayetteville

Prairie Grove

Siloam Springs

Base from U.S. Geological Survey digital data, 1:100,000, 1983Stream data from U.S. Environmental Protection Agency enhanced River Reach File 1Albers Equal Area Conic projection, North America Datum 1983

Oklahoma Arkansas

ARKANSAS OKLAHOMA 35°45'

35°30'

36°

36°15'

95° 94°45' 94°30' 94°15' 94° 93°45'

07196500

07197000

07196090

07196000

07195500

Tahlequah

Eldon

Chewey

Kansas

Watts

Watershed BoundaryLakesStreamsStateline

U.S Geological Survey

surface-water monitoring.stations and numbers(table 1)

U.S Geological Surveywater-quality monitoringsite and number (table 1)Locations of towns withwastewater-treatmentfacilities that dischargeinto streams in theIllinois River basin

0 10 20 5 Miles

0 10 20 5 Kilometers

07195500

07196090

Figure 1. The Illinois River basin, Oklahoma, with locations of surface-water and water-quality stations in the basin and of towns with wastewater-treatment facilities

that discharge into streams in the basin. [07195500, Illinois River near Watts; 07196000, Flint Creek near Kansas; 07196090, Illinois River at Chewey; 07196500, Illinois Rivernear Tahlequah; 07197000, Baron Fork at Eldon]
4 Phosphorus Concentrations, Loads, and Yields in the Illinois River Basin, Arkansas and Oklahoma, 1997-2001 Rogers Westville Tahlequah Springdale Fayetteville Prairie Grove Siloam Springs Base from U.S. Geological Survey digital data, 1:100,000, 1983 Stream data from U.S. Environmental Protection Agency enhanced River Reach File 1 Land Cover from U.S. Geological Survey NLCD 1992 Albers Equal Area Conic projection, North America Datum 1983 Oklahoma Arkansas 07196500 07197000 071960900719600007195500

ARKANSAS

OKLAHOMA

Tahlequah

Eldon

Chewey

Kansas

Watts

72.6

80.7

82.1

92.7

84.1

Averaged percentageof phosphorus loadsdelivered during runoffand base flow (table 5)

Base-Flow

Station NameStation Number

Runoff

95° 94°45' 94°30' 94°15' 94° 93°45'

35°45'35°30'

36°

36°15'

Land Cover Classes

Watershed BoundaryLake TenkillerOpen WaterResidentialCommercial/SamplingWatershed BoundaryStreams

U.S Geological Surveywater-quality monitoringsite and number (table 1)Locations of towns withwastewater-treatmentfacilities that dischargeinto streams in theIllinois River basin

Transportation

Forest/ShrublandPasture/GrasslandsCroplandsWetlandsStatelineU.S Geological Surveysurface-water monitoringstations and numbers(table 1)

0 10 20 5 Miles0 10 20 5 Kilometers

Figure 2. Land use and averaged percentage of phosphorus loads in the Illinois River basin, Oklahoma. [07195500, Illinois River near Watts; 07196000, Flint Creek near

Kansas; 07196090, Illinois River at Chewey; 07196500, Illinois River near Tahlequah; 07197000, Baron Fork at Eldon]
Introduction 5

Table 1. Station information and streamflow statistics for surface-water and water-quality stations in the Illinois River basin, Oklahoma[The Illinois River at Chewey is ungaged; streamflow is estimated by adding streamflow from Illinois River near Watts to streamflow from Flint Creek near Kansas. ft3/s, cubic foot per second; ddmmss, degrees,minutes, seconds; mi2, square mile; N/A, not applicable]

Mean annual streamflow

(ft3/s)

Minimum and maximum

mean daily streamflow for

study period

(1997-2001)

 (ft3/s)

Station name

(number)

Period of

record for

station

Latitude

(ddmmss)

Longitude

(ddmmss)

Drainage

area

(mi2)

1997-1999 1998-2000 1999-2001 Period of record Minimum (date) Maximum (date)

Illinois River nearWatts (07195500)

1955- 360748 943419 635 692 718 696 638 88

(Sept. 10,1998)

18,200(June 21,2000)

Flint Creek nearKansas (07196000)

1955-1976;1979-1990;

1992-

361111 944224 110 110 122 123 120 8.3

(Sept. 9,1998)

7,820(June 21,2000)

Illinois River atChewey (07196090)

N/A 360615 944657 820 802 840 819 N/A 97

(Sept. 10,1998)

26,000(June 21,2000)

Illinois River nearTahlequah(07196500)

1935- 355522 945524 959 1,000 1,090 1,090 946 82

(Sept. 9-10,1998)

32,800(June 22,2000)

Baron Fork at Eldon(07197000)

1948- 355516 945018 307 369 382 360 333 13

(Sept. 9-12,1998)

22,300(June 21,2000)
6 Phosphorus Concentrations, Loads, and Yields in the Illinois River Basin, Arkansas and Oklahoma, 1997-2001

Illinois River near Watts

MEAN DAILY STREAMFLOW, IN CUBIC FEET PER SECOND

Flint Creek near Kansas

Illinois River at Chewey Illinois River near Tahlequah

Baron Fork at Eldon

TIME

TIME

EXPLANATION

Total flow (Mean daily streamflow)

Base flow (Mean daily streamflow)

Base-flow water-quality sample

(Instantaneous streamflow)

Runoff water-quality sample

(Instantaneous streamflow)

1/1/97

7/1/97

1/1/98

7/1/98

1/1/99

7/1/99

1/1/00

7/1/00

1/1/01

7/1/01

1/1/02

100

101

102

103

104

105

1/1/97

7/1/97

1/1/98

7/1/98

1/1/99

7/1/99

1/1/00

7/1/00

1/1/01

7/1/01

1/1/02

100

101

102

103

104

105

100

101

102

103

104

105

Figure 3. Streamflow divided into total flow and base flow, and base-flow and runoff water samples collected at water-quality stations in the Illinois River basin, Oklahoma, 1997-2001.
Methods 7

3). The maximum mean daily streamflow during the study

period occurred in June 2000 and the minimum mean daily

streamflow during the study period occurred in September 1998

at all stations (table 1, fig. 3). Greatest mean monthly streamflows occurred from January through June and least mean

monthly streamflows occurred from mid-summer through

October at all of the stations (Blazs and others, 1998, 1999,

2000, 2001, 2002, 2003). Continuous streamflow was not measured at the Illinois River near Chewey, so estimated mean daily

streamflows for that station were computed by adding streamflow from Illinois River near Watts to streamflow from Flint

Creek near Kansas (table 1, Appendix 1).

Acknowledgments

The authors thank many people for their contributions to

the data collection and data analysis presented in this report.

There were numerous USGS personnel that participated in the

bimonthly and runoff-event water-quality sampling, but a special thanks goes to Royce Johnson for his leadership and contribution to the data collection. Additional special thanks go to

Charlie Crawford for his help with load estimations and the

LOADEST2 program and to Dave Mueller for his statistical

guidance.

Methods

The USGS collects water-quality data and operates several

continuous streamflow gaging stations and ungaged stations in

the Illinois River basin in Oklahoma. Four continuous streamflow gaging stations were selected for use in this report: Illinois

River near Watts, Flint Creek near Kansas, Illinois River near

Tahlequah, and Baron Fork at Eldon (table 1, fig. 1). The Illinois River at Chewey is an ungaged station at which streamflow

is only measured when water-quality samples are collected

(table 1, fig. 1). Stream gages were operated and streamflows

were measured according to methods described in Rantz and

others (1982). Prior to July 1999, bimonthly water-quality samples were collected at these stations. Starting in July 1999, six

additional water-quality samples were collected annually during runoff events at these stations (fig. 3). Representative waterquality samples were collected using equal-width increment

methods (Edwards and Glysson, 1999).

The USGS National Water-Quality Laboratory in Lakewood, Colorado, analyzed the water-quality samples for total

phosphorus using methods described in Patton and Truitt

(1992).

Streamflow data and phosphorus concentrations measured

from 1997 through 2001 are analyzed in this report. All streamflow and water-quality data are available through the world

wide web at http://water.usgs.gov/ok/nwis.

Streamflow was separated into base-flow and runoff components using a hydrograph separation program, Base Flow

Index (BFI) (Institute of Hydrology, 1980a, 1980b; Wahl and

Wahl, 1995) (fig. 3). Base flow is the sustained runoff or natural

flow of the stream and is largely composed of ground-water

seepage (Langbein and Iseri, 1960). Base-flow contributions

were estimated by BFI using a method proposed by the Institute

of Hydrology (1980a, 1980b). The minimum daily mean flow

was identified in consecutive 5-day increments, and minimums

less than 90 percent of adjacent minimums were defined as

turning points (Wahl and Wahl, 1988; Wahl and Tortorelli,

1997). The BFI program estimated the base-flow hydrograph by

drawing straight lines through successive turning points. Runoff components were calculated as the difference between total

streamflow and base-flow components. Each day was designated to be either base flow or runoff. Base-flow days were

defined as days when base flow was greater than or equal to 70

percent of total flow; runoff days were defined as days when

runoff contributed more than 30 percent of total flow.

Water-quality data and streamflow data were divided into

three 3-year periods: 1997-1999, 1998-2000, and 1999-2001.

The Mann-Whitney rank-sum test (Helsel and Hirsch, 1992),

used to compare pairs of data sets, was used to determine the

statistical significance of differences between base-flow and

runoff phosphorus concentrations at each station within each

period. The Kruskal-Wallis test (Helsel and Hirsch, 1992, p.

159, 355), used to compare multiple data sets at one time, was

used to determine the statistical significance of differences in

phosphorus concentrations between stations in the Illinois River

basin. The tests were selected because neither test requires normally distributed data. The null hypotheses of both tests state

that there are no differences in median concentrations between

the data sets being compared. The null hypothesis was rejected

and medians were described as being significantly different if

the two-sided p-value of the test was less than or equal to 0.05

(Helsel and Hirsch, 1992). If the null hypothesis of the KruskalWallis test was rejected and the medians were described as significantly different, the Tukey (Helsel and Hirsch, 1992, p. 196)

multiple comparison test was applied to determine which sites

were different and which were not.

Linear regression was used to evaluate relations between

phosphorus concentrations and total streamflow for each of the

periods. Regression methods have been developed to estimate

continuous constituent loads, because water-quality data are

collected intermittently. The regression method requires discrete water-quality samples and mean daily streamflow data

collected over several years. Sample dates, times, instantaneous

streamflows, and phosphorus concentrations used in this analysis are provided in Appendix 1 or through the world wide web

at http://water.usgs.gov/ok/nwis.

Constituent load (L) is the product of streamflow (Q) and

the constituent concentration in the water (C) multiplied by a

conversion factor for consistent units. Load is the amount of a

constituent transported past a selected point in a stream in a

given amount of time, usually one year. The LOADEST2 program (Crawford, 1991, 1996) was used to estimate constituent

loads by the rating-curve method (Cohn and others, 1989;

Crawford, 1991) in the Illinois River, Flint Creek, and Baron

Fork. LOADEST2 estimates rating-curve parameters and mean
8 Phosphorus Concentrations, Loads, and Yields in the Illinois River Basin, Arkansas and Oklahoma, 1997-2001

load using several regression methods and a ratio estimator.

Because some of the constituent concentrations included in this

analysis were censored (values less than the laboratory method

detection limit), parameters were estimated by maximum likelihood estimation (MLE) methods (Dempster and others, 1977;

Wolynetz, 1979). In the absence of censored data, the MLE

method is equivalent to ordinary least squares regression. An

estimate of the uncertainty in the estimated load was obtained

using the method described by Likes (1980) and Gilroy and others (1990). LOADEST2 contains 10 rating-curve models that

can test the relation between constituent load and streamflow.

The model used for this report (equation 1) includes a time variable to model the relation between the natural logarithms of L

and Q:

ln(L) = b0 + b1 ln(Q) + b2dectime (1)

where

L = constituent load, in pounds per day (lb/d);

b0 = regression constant, dimensionless;

b1 and b2 = regression coefficients, dimensionless;

Q = daily mean streamflow, in cubic feet per

second (ft3/s); and

dectime = time, in fractional years.

Plots of residuals (ln(instantaneous load) - In(estimated

load)) with LOWESS curves are shown in Appendix 2. The

LOWESS curve is a central line that represents the moving

average or middle smooth through the data (Helsel and Hirsch,

1992). The shape of the curve indicates fluctuations in the data.

The plots indicate the goodness of fit of this model, with a perfect fit indicated by the curve fluctuating around a value of zero.

Data from stations on the Illinois river generally appeared to fit

the model better than data from Flint Creek and Baron Fork.

The goodness of fit also generally appeared to increase with

time at most stations in the basin. Other LOADEST2 predefined

regression models using various combinations of streamflow,

time, and seasonal coefficients did not have lesser residuals

than the model used for this report.

Estimated mean annual phosphorus loads and estimates of

the standard deviations of the mean loads were calculated by

LOADEST2 using all base-flow and runoff data. The daily load

values generated by LOADEST2 were then separated into baseflow and runoff sample sets according to the number of baseflow days and the number of runoff days in each 3-year period.

Mean annual base-flow loads were calculated as the mean of the

base-flow sample set. Mean annual runoff loads were calculated

as the mean of the runoff sample set. Seasonal base-flow and

runoff loads were calculated in the same way based on the number of base-flow and runoff days in each season of each period.

Phosphorus yields for each of the three periods at each station were calculated by dividing mean annual phosphorus loads

by drainage area. Flow-weighted concentrations for each of the

three periods at each station were calculated by dividing mean

annual phosphorus loads by mean annual streamflow.

Phosphorus Concentrations, Loads, and

Yields in the Illinois River basin

Phosphorus in the Illinois River basin is described in terms

of three 3-year periods (1997-1999, 1998-2000, and 1999-

2001) of mean concentrations, loads, and yields in base-flow

and runoff samples, and in terms of mean flow-weighted concentrations.

Concentrations

Phosphorus concentrations were significantly greater (p <

0.05) in runoff-event samples than in base-flow samples for the

1998-2000 and 1999-2001 periods at Flint Creek near Kansas,

Illinois River at Chewey, Illinois River near Tahlequah, and

Baron Fork at Eldon, but this difference was not significant at

Illinois River near Watts (tables 2 and 3, fig. 4). The similarity

of phosphorus concentrations during base flow and runoff at the

Watts station may be caused by phosphorus cycling in Lake

Frances, immediately upstream from that station. Phosphorus

may precipitate with sediments to the lake bed during runoff, to

be gradually released from those sediments into the water column during base flow. Phosphorus concentrations were not significantly greater in runoff-event samples than in base-flow

samples for the period 1997-1999 at Illinois River near Watts,

Flint Creek near Kansas, Illinois River at Chewey, and Baron

Fork at Eldon. This lack of difference may be attributed to the

lack of water-quality samples collected during runoff events

during this period.

Phosphorus concentrations in base-flow samples during all

3-year periods significantly (p < 0.05) decreased in the downstream direction in the Illinois River from the Chewey to Tahlequah stations (fig. 5), as has been reported for other pointsource affected streams in the region (Haggard, 2000; Haggard

and others, 2001). Phosphorus concentrations in base-flow samples from the Illinois River generally decreased with increasing

streamflow (fig. 4). As base flow increases by addition of

ground water, dilution reduces the concentration of phosphorus

from point sources such as municipal wastewater-treatment

plants. The Illinois River and Flint Creek receive phosphorus

concentrations from point sources. The Baron Fork receives

treated wastewater from the relatively small community of Lincoln, Arkansas. Consequently, phosphorus concentrations in

base-flow samples from the Baron Fork were significantly less

than those in base-flow samples from the Illinois River and

Flint Creek during all 3-year periods (fig. 5).

Phosphorus concentrations in runoff samples for all 3-year

periods were not significantly different among the four stations

on Flint Creek and the Illinois River, but concentrations at the

Baron Fork were significantly less than at all other stations (fig.

6). Phosphorus concentrations in runoff samples from the Illinois River, Flint Creek, and the Baron Fork generally increased

with increasing streamflow (fig. 4). Possible causes of larger

concentrations of phosphorus during runoff events than in base

flow are resuspension of phosphorus from the streambed,
Phosphorus Concentrations, Loads, and Yields in the Illinois River basin 9

Table 2. Summary statistics of phosphorus concentrations from base-flow and runoff water samples collected at water-quality stations in the Illinois River basin, Oklahoma, periods 1997-1999, 1998-2000, and 1999-2001[Min, minimum concentration; Med, median concentration; Mean, mean concentration; Max, maximum concentration; Obs, number of observations; mg/L, milligram per liter; all concentration data, includingcensored data, were used to calculate statistics. Censored data (concentrations less than minimum reporting limit) were entered in the statistics calculations as one-half the minimum reporting limit.]

Base Flow Runoff

Station name

(number) 3-year period Min (mg/L) Med (mg/L) Mean (mg/L) Max (mg/L) Obs Min (mg/L) Med (mg/L) Mean (mg/l) Max (mg/L) Obs

Illinois River nearWatts, Oklahoma(07195500)

1997-1999 0.06 0.17 0.17 0.28 21 0.07 0.13 0.14 0.28 131998-2000 0.06 0.21 0.19 0.38 16 0.07 0.18 0.26 0.65 171999-2001 0.16 0.25 0.26 0.38 12 <0.06 0.30 0.37 0.88 20

Flint Creek nearKansas, Oklahoma(07196000)

1997-1999 0.09 0.12 0.15 0.66 17 0.09 0.13 0.18 0.88 161998-2000 0.10 0.13 0.16 0.66 16 0.10 0.17 0.39 1.66 171999-2001 0.10 0.12 0.17 0.66 12 0.10 0.21 0.41 1.66 20

Illinois River atChewey, Oklahoma(07196090)

1997-1999 0.05 0.13 0.12 0.17 17 0.07 0.15 0.20 0.93 181998-2000 0.05 0.14 0.14 0.22 14 0.07 0.21 0.33 0.96 191999-2001 0.12 0.16 0.18 0.26 10 0.07 0.27 0.42 0.96 21

Illinois River nearTahlequah, Oklahoma (07196500)

1997-1999 0.02 0.07 0.06 0.11 20 0.07 0.10 0.19 1.14 151998-2000 0.03 0.08 0.08 0.12 16 0.07 0.15 0.26 1.14 191999-2001 0.04 0.09 0.09 0.12 11 <0.06 0.22 0.31 1.14 24

Baron Fork at Eldon,Oklahoma(07197000)

1997-1999 <0.01 0.02 0.02 0.05 20 <0.01 0.03 0.04 0.09 141998-2000 <0.01 0.03 0.03 0.06 15 <0.01 0.04 0.24 1.65 191999-2001 0.03 0.03 0.03 0.05 12 0.04 0.09 0.26 1.65 21
10 Phosphorus Concentrations, Loads, and Yields in the Illinois River Basin, Arkansas and Oklahoma, 1997-2001

Table 3. Mann-Whitney rank-sum test (Helsel and Hirsch, 1992) results comparing base-flow phosphorus concentrations to runoff phosphorus concentrations from water samples collected at water-quality stations in the Illinois River basin, Oklahoma, periods 1997-1999,

1998-2000, and 1999-2001

[p-values in bold indicate statistically significant (p < 0.05) differences between groups of data]

3-year period

Station name (number) 1997-1999 1998-2000 1999-2001

Illinois River near Watts (07195500) z = 1.190

p = 0.2341

z = 0.7210

p = 0.4709

z = 0.9155

p = 0.3599

Flint Creek near Kansas (07196000) z = 0.6371

p = 0.5240

z = 2.049

p = 0.0405

z = 2.659

p = 0.0078

Illinois River at Chewey (07196090) z = 1.259

p = 0.2080

z = 2.664

p = 0.0077

z = 2.940

p = 0.0033

Illinois River near Tahlequah (07196500) z = 3.752

p = 0.0002

z = 3.988

p = 0.0001

z = 3.913

p = 0.0001

Baron Fork at Eldon (07197000) z = 1.532

p = 0.1257

z = 2.160

p = 0.0308

z = 2.414

p = 0.0158
Phosphorus Concentrations, Loads, and Yields in the Illinois River basin 11

INSTANTANEOUS DISCHARGE,

IN CUBIC FEET PER SECOND

TOTAL PHOSPHORUS CONCENTRATION, IN MILLIGRAMS PER LITER

Illinois River near Watts

Illinois River at Chewey Illinois River near Tahlequah

INSTANTANEOUS DISCHARGE,

IN CUBIC FEET PER SECOND

Baron Fork at Eldon

Flint Creek near Kansas

0.01

0.1

1

2

0.01

0.1

1

2

101 102 10 4 105 103 0.01

0.1

1

2 101 102 10 4 105 103

Base-flow phosphorus concentration

Runoff phosphorus concentration

EXPLANATION

0.037 milligram per liter phosphorus

concentration (75th percentile of

flow-weighted phosphorus concentrations

from relatively undeveloped basins of the

United States (Clark and others, 2000))

0.022 milligram per liter phosphorus

concentration (Median of flow-weighted

phosphorus concentrations from relatively

undeveloped basins of the United States

(Clark and others, 2000))

Figure 4. Phosphorus concentrations from base-flow and runoff water samples collected at water-quality stations in the Illinois

River basin, Oklahoma, 1997-2001.
12 Phosphorus Concentrations, Loads, and Yields in the Illinois River Basin, Arkansas and Oklahoma, 1997-2001

Illinois River

near Watts,

Oklahoma

(07195500)

Flint Creek

near Kansas,

Oklahoma

(07196000)

Illinois River

at Chewey,

Oklahoma

(07196090)

Illinois River

near Tahlequah,

Oklahoma

(07196500)

Baron Fork

at Eldon,

Oklahoma

(07197000)

1

0.01

0.1

0.005

PHOSPHORUS CONCENTRATION, IN MILLIGRAM PER LITER

1

0.01

0.1

0.005

1

0.01

0.1

0.005

(21) (17)

(17)

(20)

(20)

A

A A

B

C

1997-1999

(16) (16)

(14)

(16)

(15)

A

A A

B

C

1998-2000

(12)

(12)

(10)

(11)

(12)

A

B B

C

D

1999-2001

EXPLANATION

95th percentile

75th percentile

Median

25th percentile

5th percentile

(15) Number of samples

A

Distributions with the

same letter are not

significantly (p<0.05)

different

0.037 milligram per liter

phosphorus concentration

(75th percentile of flowweighted phosphorus

concentrations from relatively

undeveloped basins of the

United States (Clark and

others, 2000))

0.022 milligram per liter

phosphorus concentration

(Median of flow-weighted

phosphorus concentrations

from relatively undeveloped

basins of the United States

(Clark and others, 2000))

Figure 5. Distributions of base-flow phosphorus concentrations from water samples collected at water-quality stations in the

Illinois River basin, Oklahoma, periods 1997-1999, 1998-2000, and 1999-2001.
Phosphorus Concentrations, Loads, and Yields in the Illinois River basin 13

1

0.01

0.1

0.005

5

1

0.01

0.1

0.005

5

1

0.01

0.1

0.005

5

PHOSPHORUS CONCENTRATION, IN MILLIGRAMS PER LITER

Illinois River

near Watts,

Oklahoma

(07195500)

Flint Creek

near Kansas,

Oklahoma

(07196000)

Illinois River

at Chewey,

Oklahoma

(07196090)

Illinois River

near Tahlequah,

Oklahoma

(07196500)

Baron Fork

at Eldon,

Oklahoma

(07197000)

EXPLANATION

95th percentile

75th percentile

Median

25th percentile

5th percentile

(15) Number of samples

A

Distributions with the

same letter are not

significantly (p<0.05)

different

0.037 milligram per liter

phosphorus concentration

(75th percentile of flowweighted phosphorus

concentrations from relatively

undeveloped basins of the

United States (Clark and

others, 2000))

0.022 milligram per liter

phosphorus concentration

(Median of flow-weighted

phosphorus concentrations

from relatively undeveloped

basins of the United States

(Clark and others, 2000))

(13)

(16) (18) (15)

(14) A A A A

B

(17)

(17) (19) (19) (19)

A A A A

B

(20)

(20) (21) (24) (21)

A A A A

B

B

1997-1999

1998-2000

1999-2001

Figure 6. Distributions of runoff phosphorus concentrations from water samples collected at water-quality stations in the Illinois River basin, Oklahoma, periods 1997-1999, 1998-2000, and 1999-2001.
14 Phosphorus Concentrations, Loads, and Yields in the Illinois River Basin, Arkansas and Oklahoma, 1997-2001

stream bank erosion, and the addition of phosphorus from nonpoint sources.

Estimated Annual Loads

Linear regression models developed by LOADEST2 for

the estimation of phosphorus loads for all 3-year periods at each

station are listed in table 4. Estimated mean annual phosphorus

loads (referred to as mean annual total loads) were substantially

greater at the Illinois River stations than at Flint Creek and the

Baron Fork, primarily because of greater streamflow at the stations on the Illinois River (tables 1 and 5). Annual total loads in

the Illinois River increased from Watts to Tahlequah, mostly

because of the increase in runoff load with drainage area (table

5). Annual total loads appeared to generally increase with time

during 1997-2001 at all stations, but this increase might be

partly attributable to the beginning of runoff-event sampling in

the basin in July 1999.

Annual base-flow loads were least in the Baron Fork,

despite a larger drainage basin and greater base flow than Flint

Creek, which receives phosphorus from larger wastewater discharges (fig. 2). Annual base-flow loads at stations on the Illinois River were about 10 times greater than those on the Baron

Fork and were about 5 times greater than those on Flint Creek.

Except for the Illinois River near Watts, 1999-2001 period,

annual base-flow phosphorus loads did not substantially

increase in the basin from 1997-2001 (table 5).

Annual runoff loads in the basin increased with increasing

drainage area and with increasing streamflow (tables 1 and 5).

The portion of annual phosphorus load contributed by runoff

increased in the downstream direction in the Illinois River

(Watts to Tahlequah) (table 5). Runoff components of the

annual total load ranged from 58.7 to 96.8 percent from 1997 to

2001 (table 5). At Flint Creek and Illinois River stations, the

range in average runoff component was 58.7 to 87.4 percent of

the annual total load with less than 41.5 percent of the days

including substantial runoff (runoff component greater than 30

percent of total flow) (tables 5 and 6). Runoff components of the

annual total load at the Baron Fork ranged from 86.6 to 96.8

percent (table 5). Annual runoff loads appeared to substantially

increase over the three time periods at all stations in the basin.

The most significant increase occurred between the 1997-1999

period and the 1998-2000 period, which coincides with the

beginning of runoff-event sampling in the basin in July 1999.

Therefore, the increase may be partly caused by the beginning

of runoff-event sampling in the basin. The resuspension of temporarily retained phosphorus on the streambed or banks or additions of non-point source phosphorus components in the watershed that occur during runoff seem to dominate phosphorus

transport in the Illinois River basin.

Estimated Seasonal Loads

Base-flow phosphorus loads generally were least in fall

(September through November) and greatest in spring (March

through May) for all periods at all stations in the Illinois River

basin (table 7). Runoff phosphorus loads were least in fall for

all periods at all stations. Runoff loads generally were greatest

in spring for period 1997-1999, but were greatest in summer

(June through August) for periods 1998-2000 and 1999-2001.

The shift in seasonal trends between the 3-year periods may be

a result of the 1999 onset of sampling of runoff events. Streamflows and phosphorus concentrations from runoff events like

the June 2000 peak flow (maximum streamflow event for the

1997-2001 period; table 1, fig. 3) may have been sufficient to

shift the greatest seasonal loads from spring to summer at all

stations for periods 1998-2000 and 1999-2001.

Yields

Total yields of phosphorus ranged from 107 to 797 pounds

per year per square mile (lbs/yr/mi2), with greatest yields being

reported for Flint Creek near Kansas (365 to 797 lbs/yr/mi2) and

the least yields being reported for Baron Fork at Eldon (107 to

440 lbs/yr/mi2) (table 5). The greater yields in Flint Creek may

be caused by the wastewater-treatment plant discharging to that

stream (fig. 2). Base-flow yields did not substantially change

over the three periods at any station except Illinois River near

Watts (1999-2001). Base-flow yields also decreased downstream in the Illinois River possibly because of dilution. Runoff

yields more than doubled between the 1997-1999 period and the

1999-2001 period. Because yield (mean load divided by drainage area) is proportional to load, this increase might be partly

attributable to the beginning of runoff-event sampling in the

basin in July 1999.

Estimated Mean Flow-Weighted Concentrations

Estimated mean flow-weighted phosphorus concentrations

at the stations in the basin were more than 10 times greater than

the median and were consistently greater than the 75th percentile of flow-weighted phosphorus concentrations in relatively

undeveloped basins of the United States (0.022 mg/L and 0.037

mg/L, respectively, Clark and others, 2000; fig. 7, table 8). In

addition, flow-weighted phosphorus concentrations in 1999-

2001 at all Illinois River stations and at Flint Creek were equal

to or greater than the 75th percentile of all NAWQA stations in

the United States (0.29 mg/L, David Mueller, U.S. Geological

Survey, written commun., 2003).

Estimated Phosphorus Loads into Lake Tenkiller

Phosphorus loads entering Lake Tenkiller can be estimated

by adding the loads of the Baron Fork and the Illinois River near

Tahlequah. Phosphorus loads at these stations do not represent
Phosphorus Concentrations, Loads, and Yields in the Illinois River basin 15

Table 4. Regression models developed using total phosphorus concentrations from water samples and streamflows collected at water-quality stations in the Illinois Riverbasin, Oklahoma, periods 1997-1999, 1998-2000, and 1999-2001[ln, natural logarithm; L, daily load in pounds per day; Q, mean daily streamflow in cubic foot per second; dectime, time factor in decimal years]

Station name (number) 3-year period Number of observations Number of uncensored observations1

1 Censored observations are most often a result of an analysis value lower than the laboratory reporting limit.

Regression model

Estimated

residual

variance2

2 Estimated residual variance is the maximum likelihood estimation variance corrected for the number of observations, number of censored observations, and number of parameters in the

model.

Illinois River near Watts(07195500)

1997-1999 34 34 ln(L) = 5.56 + 0.703*ln(Q) + 0.150*dectime 0.1671998-2000 33 33 ln(L) = 5.43 + 1.09*ln(Q) + 0.480*dectime 0.1631999-2001 32 31 ln(L) = 6.53 + 1.12*ln(Q) + 0.320*dectime 0.287

Flint Creek near Kansas(07196000)

1997-1999 33 33 ln(L) = 3.71 + 1.22*ln(Q) + 0.192*dectime 0.1601998-2000 33 33 ln(L) = 3.98 + 1.39*ln(Q) + 0.140*dectime 0.1661999-2001 32 32 ln(L) = 4.73 + 1.43*ln(Q) - 0.00295*dectime 0.142

Illinois River at Chewey(07196090)

1997-1999 35 35 ln(L) = 5.61 + 1.20*ln(Q) + 0.228*dectime 0.1651998-2000 33 33 ln(L) = 6.13 + 1.30*ln(Q) + 0.336*dectime 0.1611999-2001 31 31 ln(L) = 7.10 + 1.35*ln(Q) + 0.213*dectime 0.112

Illinois River near Tahlequah (07196500) 1997-1999 35 35 ln(L) = 5.28 + 1.39*ln(Q) + 0.285*dectime 0.261 1998-2000 35 35 ln(L) = 5.75 + 1.45*ln(Q) + 0.274*dectime 0.189

1999-2001 35 34 ln(L) = 6.63 + 1.50*ln(Q) + 0.0566*dectime 0.108

Baron Fork at Eldon(07197000)

1997-1999 34 24 ln(L) = 2.85 + 1.28*ln(Q) + 0.349*dectime 0.3461998-2000 34 21 ln(L) = 3.16 + 1.60*ln(Q) + 0.380*dectime 0.5601999-2001 33 22 ln(L) = 4.35 + 1.64*ln(Q) + 0.168*dectime 0.375
16 Phosphorus Concentrations, Loads, and Yields in the Illinois River Basin, Arkansas and Oklahoma, 1997-2001 Table 5. Mean annual phosphorus loads and yields estimated from phosphorus concentrations in water samples collected at water-quality stations in the Illinois River basin, Oklahoma, periods 1997-1999, 1998-2000, and 1999-2001 [mi2, square miles; lb/yr, pounds per year; lb/yr/mi2, pounds per year per square mile; SD, standard deviation. Mean and standard deviation of the total load are calculated by LOADEST2 and are statistics of all data in the 3-year period. Means of base-flow loads are calculated from base-flow data only; means of runoff loads are calculated from runoff data only. Differences between total load and the sum of base-flow plus runoff loads are due to rounding within LOADEST2.] Station name (number) Drainage area (mi2

)

3-year

period

Mean annual

total load

(±SD)

(lb/yr)

Total yield

(lb/yr/mi2

)

Mean annual

base-flow load

(lb/yr)

Base-flow

yield

(lb/yr/mi2

)

Mean annual runoff

load

(lb/yr)

Runoff yield

(lb/yr/mi2

)

Load

delivered

during

runoff

Illinois River nearWatts (07195500)

635 1997-1999 164,000 ± 17,900 258 69,600 110 96,200 151 58.7

1998-2000 329,000 ± 33,200 518 73,500 116 256,000 403 77.81999-2001 438,000 ± 51,100 690 97,700 154 356,000 561 81.3

Flint Creek nearKansas(07196000)

110 1997-1999 40,200 ± 5,110 365 11,900 108 29,500 268 73.4

1998-2000 80,400 ± 9,500 731 12,200 111 68,300 621 85.01999-2001 87,700 ± 8,400 797 12,700 115 73,400 667 83.7

Illinois River atChewey(07196090)

820 1997-1999 292,000 ± 29,200 356 74,300 90.6 217,000 265 74.3

1998-2000 438,000 ± 43,800 534 74,200 90.5 382,000 466 87.21999-2001 548,000 ± 40,200 668 79,400 96.8 465,000 567 84.9

Illinois River nearTahlequah(07196500)

959 1997-1999 307,000 ± 47,400 320 68,800 71.7 238,000 248 77.5

1998-2000 511,000 ± 65,800 533 67,000 69.9 446,000 465 87.31999-2001 621,000 ± 47,500 648 68,600 71.5 543,000 566 87.4

Baron Fork atEldon (07197000)

307 1997-1999 32,800 ± 7,300 107 4,570 14.9 28,400 92.5 86.6

1998-2000 124,000 ± 33,600 404 4,920 16.0 120,000 391 96.81999-2001 135,000 ± 24,800 440 5,980 19.5 128,000 417 94.8
Phosphorus Concentrations, Loads, and Yields in the Illinois River basin 17

Table 6. Number of days of base flow and runoff designated by Base-Flow Index (BFI) program at water-quality stations in the Illinois River basin, Oklahoma, periods 1997-1999,1998-2000, and 1999-2001

Spring Summer Fall Winter Total Percent

of runoff

days in

period Station name (number) 3-year period Base flow Runoff Base flow Runoff Base flow Runoff Base flow Runoff Base flow Runoff

Illinois River near Watts(07195500)

1997-1999 150 126 207 69 206 67 142 128 705 390 35.61998-2000 142 134 189 87 198 75 152 119 681 415 37.91999-2001 160 116 172 104 204 69 138 133 674 422 38.5

Flint Creek near Kansas(07196000)

1997-1999 171 105 201 75 207 66 174 96 753 342 31.21998-2000 158 118 194 82 193 80 187 84 732 364 33.21999-2001 182 94 185 91 189 84 161 110 717 379 34.6

Illinois River at Chewey(07196090)

1997-1999 155 121 209 67 205 68 143 127 712 383 35.01998-2000 142 134 192 84 198 75 153 118 685 411 37.51999-2001 159 117 176 100 203 70 139 132 677 419 38.2

Illinois River near Tahlequah (07196500) 1997-1999 175 101 201 75 179 94 147 123 702 393 35.9 1998-2000 159 117 193 83 167 106 147 124 666 430 39.2

1999-2001 166 110 159 117 187 86 129 142 641 455 41.5

Baron Fork at Eldon(07197000)

1997-1999 117 159 197 79 184 89 149 121 647 448 40.91998-2000 91 185 194 82 172 101 148 123 605 491 44.81999-2001 130 146 168 108 196 77 129 142 623 473 43.2
18 Phosphorus Concentrations, Loads, and Yields in the Illinois River Basin, Arkansas and Oklahoma, 1997-2001

Table 7. Seasonal phosphorus loads estimated from phosphorus concentrations in water samples collected at water-quality stations in

the Illinois River basin, Oklahoma, periods 1997-1999, 1998-2000, and 1999-2001

[Values are loads in pounds per season; spring is March through May, summer is June through August, fall is September through November, and winter is December through February]

Flow type Station name

(number) Spring Summer Fall Winter

1997-1999

Base

Flow

Illinois River near Watts (07195500) 22,200 17,900 14,600 14,900

Flint Creek near Kansas (07196000) 4,880 2,290 1,770 2,970

Illinois River at Chewey (07196090) 31,400 17,100 10,900 15,000

Illinois River near Tahlequah (07196500) 37,500 12,300 5,300 13,800

Baron Fork at Eldon (07197000) 1,810 788 389 1,570

Runoff Illinois River near Watts (07195500) 41,300 15,000 8,750 31,100

Flint Creek near Kansas (07196000) 12,700 5,220 1,590 9,980

Illinois River at Chewey (07196090) 97,200 34,200 11,600 73,200

Illinois River near Tahlequah (07196500) 103,000 38,000 13,400 84,500

Baron Fork at Eldon (07197000) 14,000 2,270 1,680 10,400

1998-2000

Base

Flow

Illinois River near Watts (07195500) 23,700 18,800 14,300 16,900

Flint Creek near Kansas (07196000) 3,970 2,980 1,810 3,490

Illinois River at Chewey (07196090) 27,400 18,600 11,700 16,400

Illinois River near Tahlequah (07196500) 33,000 14,500 5,790 13,800

Baron Fork at Eldon (07197000) 1,660 1,250 343 1,660

Runoff Illinois River near Watts (07195500) 79,100 116,000 19,300 41,300

Flint Creek near Kansas (07196000) 15,600 41,300 2,990 8,650

Illinois River at Chewey (07196090) 110,000 191,000 20,500 60,600

Illinois River near Tahlequah (07196500) 112,000 240,000 23,300 71,100

Baron Fork at Eldon (07197000) 30,200 67,800 5,220 17,100

1999-2001

Base

Flow

Illinois River near Watts (07195500) 35,000 22,900 18,600 21,300

Flint Creek near Kansas (07196000) 5,190 2,860 1,340 3,330

Illinois River at Chewey (07196090) 31,100 18,700 12,400 17,400

Illinois River near Tahlequah (07196500) 34,000 13,900 6,360 14,200

Baron Fork at Eldon (07197000) 2,680 1,140 421 1,750

Runoff Illinois River near Watts (07195500) 76,900 124,000 26,700 129,000

Flint Creek near Kansas (07196000) 13,000 40,600 2,260 17,400

Illinois River at Chewey (07196090) 94,000 194,000 21,700 156,000

Illinois River near Tahlequah (07196500) 106,000 248,000 20,000 169,000

Baron Fork at Eldon (07197000) 24,300 62,600 2,950 38,100
Phosphorus Concentrations, Loads, and Yields in the Illinois River basin 19

PHOSPHORUS CONCENTRATION, IN MILLIGRAMS PER LITER

Illinois River

near Watts,

Oklahoma

(07195500)

Flint Creek

near Kansas,

Oklahoma

(07196000)

Illinois River

at Chewey,

Oklahoma

(07196090)

Illinois River

near Tahlequah,

Oklahoma

(07196500)

Baron Fork

at Eldon,

Oklahoma

(07197000)

5

1

0.1

0.01

0.005

1997-1999

1998-2000

1999-2001

Estimated mean flow-weighted

phosphorus concentration

EXPLANATION

Outlier

95th percentile

75th percentile

Median

25th percentile

5th percentile

Outlier

(34) Number of samples

(34)

(33)

(32) (33)

(33) (32)

(35)

(33) (31)

(35)

(35) (35)

(34)

(33) (33)

0.037 milligram per liter phosphorus concentration

(75th percentile of flow-weighted phosphorus

concentrations from relatively undeveloped basins of the

United States (Clark and others, 2000))

0.022 milligram per liter phosphorus concentration

(Median of flow-weighted phosphorus concentrations

from relatively undeveloped basins of the United States

(Clark and others, 2000))

Figure 7. Instantaneous phosphorus concentrations from water samples collected at water-quality stations in the Illinois River

basin, Oklahoma, periods 1997-1999, 1998-2000, and 1999-2001. Mean flow-weighted phosphorus concentrations are calculated

from loads estimated by LOADEST2.
20 Phosphorus Concentrations, Loads, and Yields in the Illinois River Basin, Arkansas and Oklahoma, 1997-2001

Table 8. Mean annual phosphorus loads, mean annual streamflows, and mean flow-weighted phosphorus concentrations for waterquality stations in the Illinois River basin, Oklahoma, periods 1997-1999, 1998-2000, and 1999-2001

[lb/yr, pounds per year; ft3/s, cubic foot per second; mg/L, milligram per liter]

Station name (number) 3-year period

Mean annual

phosphorus load

(lb/yr)

Mean annual

streamflow for years

of study

(ft3

/s)

Mean flowweighted

phosphorus

concentration

(mg/L)

Illinois River near Watts

(07195500)

1997-1999 164,000 692 0.120

1998-2000 329,000 718 0.233

1999-2001 438,000 696 0.320

Flint Creek near Kansas

(07196000)

1997-1999 40,200 110 0.186

1998-2000 80,400 122 0.335

1999-2001 87,700 123 0.362

Illinois River at Chewey

(07196090)

1997-1999 292,000 802 0.185

1998-2000 438,000 840 0.265

1999-2001 548,000 819 0.339

Illinois River near Tahlequah (07196500)1997-1999 307,000 1,000 0.156

1998-2000 511,000 1,090 0.238

1999-2001 621,000 1,090 0.289

Baron Fork at Eldon

(07197000)

1997-1999 32,800 369 0.045

1998-2000 124,000 382 0.165

1999-2001 135,000 360 0.190
Summary 21

the entire phosphorus load into Lake Tenkiller, but the drainage

area of these stations accounts for more than 80 percent of the

drainage basin of the lake. The Illinois River and Baron Fork

contributed a mean load of about 577,000 pounds per year of

phosphorus to Lake Tenkiller from 1997 through 2001 (table 9).

More than 86 percent of the annual phosphorus load was transported to Lake Tenkiller by runoff. The Illinois River transported about 13 times more of the phosphorus load during base

flow and almost 5 times more of the phosphorus load during

runoff to the lake than the Baron Fork (table 9).

Summary

The Illinois River and tributaries, Flint Creek and the

Baron Fork, are designated scenic rivers in Oklahoma. Streams

in the Illinois River basin are susceptible to potentially large

concentrations of phosphorus from point sources and non-point

sources. Recent phosphorus increases in streams in the basin

have resulted in excess algae growth, which have limited the

aesthetic benefits of water bodies in the basin, especially the

Illinois River and Lake Tenkiller. The Oklahoma Water

Resources Board has established a standard for total phosphorus not to exceed the 30-day geometric mean concentration of

0.037 milligram of phosphorus per liter in Oklahoma Scenic

Rivers.

In July 1999, the U.S. Geological Survey, in cooperation

with the Oklahoma Scenic Rivers Commission and the Oklahoma Water Resources Board, supplemented fixed period,

bimonthly water-quality sampling with six runoff-event samplings per year to better determine water quality over the range

of streamflows in the basin for 1997-2001. Phosphorus concentrations, loads, and yields were determined for three 3-year periods—1997-1999, 1998-2000, and 1999-2001.

Phosphorus concentrations were significantly greater in

runoff-event samples than in base-flow samples for the 1998-

2000 and 1999-2001 periods at Flint Creek near Kansas, Illinois

River at Chewey, Illinois River near Tahlequah, and Baron Fork

at Eldon, but this difference was not significant at Illinois River

near Watts. Phosphorus concentrations generally decreased

with increasing base flow in the Illinois River as a result of

ground-water dilution. Phosphorus concentrations during runoff events increased with increasing streamflow in all streams,

possibly because of resuspension of phosphorus from the streambed, stream bank erosion, and the addition of non-point

source phosphorus components.

Estimated mean annual phosphorus loads were substantially greater at the Illinois River stations than at Flint Creek and

the Baron Fork, and loads appeared to generally increase with

time during 1997-2001 at all stations, but this increase might be

partly attributable to the beginning of runoff-event sampling in

the basin in July 1999.

Base-flow phosphorus loads at stations on the Illinois

River were about 10 times greater than those on the Baron Fork

and 5 times greater than those on Flint Creek. Runoff phosphorus loads increased with increasing drainage area and increasing

streamflow. Runoff components of the annual total phosphorus

load ranged from 58.7 to 96.8 percent from 1997-2001.

Seasonal base-flow loads generally were least in fall (September through November) and were greatest in spring (March

through May) for all periods at all stations in the Illinois River

basin. Seasonal runoff loads were least in fall for all periods,

were greatest in spring in 1997-1999, and were greatest in summer (June through August) for 1998-2000 and 1999-2001.

Total yields of phosphorus ranged from 107 to 797 pounds

per year per square mile. Greatest yields were at Flint Creek

near Kansas (365 to 797 pounds per year per square mile) and

the least yields were at Baron Fork at Eldon (107 to 440 pounds

per year per square mile). Base-flow yields did not substantially

change over the three periods at any station except Illinois River

near Watts (1999-2001). Runoff yields more than doubled

between the 1997-1999 period and the 1999-2001 period at all

stations, but this increase might be partly attributable to the

beginning of runoff-event sampling in the basin.

Estimated mean flow-weighted concentrations were more

than 10 times greater than the median and were consistently

greater than the 75th percentile of flow-weighted phosphorus

concentrations in samples collected at relatively undeveloped

basins of the United States (0.022 milligram per liter and 0.037

milligram per liter, respectively). In addition, flow-weighted

phosphorus concentrations in 1999-2001 at all Illinois River

stations and at Flint Creek near Kansas were equal to or greater

than the 75th percentile of all National Water-Quality Assessment Program stations in the United States (0.29 milligram per

liter).

The annual average (1997-2001) phosphorus load entering

Lake Tenkiller was about 577,000 pounds per year. More than

86 percent of the phosphorus load was transported to the lake by

runoff.

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Appendixes
26 Phosphorus Concentrations, Loads, and Yields in the Illinois River Basin, Arkansas and Oklahoma, 1997-2001
Appendixes 27

Appendix 1a. Instantaneous streamflows and total phosphorus concentrations for Illinois River near Watts, Oklahoma, from 1997-2001

[ft3/s, cubic foot per second; mg/L, milligram per liter; <, less than; all water-quality and streamflow data available at http://water.usgs.gov/ok/nwis]

Date Sample time

Instantaneous

streamflow

(ft3

/s)

Total phosphorus

concentration

(mg/L)

01-23-1997 1145 385 .10

02-11-1997 1145 557 .08

03-21-1997 1245 945 .09

04-24-1997 1000 479 .18

05-20-1997 1550 361 .25

06-24-1997 1115 410 .17

07-24-1997 0900 183 .24

08-22-1997 1025 315 .24

09-16-1997 1040 224 .22

10-20-1997 1515 236 .19

11-18-1997 0950 355 .10

12-02-1997 1330 398 .12

01-23-1998 1210 673 .15

02-09-1998 1520 462 .06

03-24-1998 1200 1,600 .07

04-23-1998 1100 455 .07

05-13-1998 0850 420 .06

06-23-1998 1437 204 .17

07-15-1998 1500 180 .28

08-19-1998 1335 128 .17

09-23-1998 1455 492 .18

10-20-1998 0935 270 .21

11-17-1998 0950 315 .13

12-08-1998 1420 493 .11

01-07-1999 1030 404 .10

02-03-1999 0850 709 .13

03-24-1999 1230 1,220 .10

04-07-1999 1040 1,840 .18

05-04-1999 1035 1,370 .16

06-16-1999 1230 562 .23

08-12-1999 0810 260 .16

10-21-1999 1115 148 .25

12-01-1999 1420 158 .25
28 Phosphorus Concentrations, Loads, and Yields in the Illinois River Basin, Arkansas and Oklahoma, 1997-2001

12-10-1999 1610 729 .28

02-18-2000 0835 1,560 .29

04-12-2000 0920 1,270 .27

05-07-2000 1052 2,410 .59

06-18-2000 0950 10,600 .57

06-22-2000 0745 24,100 .65

07-18-2000 1345 398 .20

08-15-2000 1445 191 .26

09-26-2000 1530 341 .30

10-24-2000 1030 176 .38

11-07-2000 0720 1,400 .34

12-08-2000 1430 279 .21

01-30-2001 1100 2,740 .30

02-15-2001 1100 7,660 .67

04-18-2001 1115 352 .18

05-18-2001 1120 851 .88

06-15-2001 1230 3,930 <.06

08-15-2001 1530 163 .37

09-18-2001 1250 815 .36

10-11-2001 1230 2,490 .59

10-23-2001 0800 236 .31

12-11-2001 1515 284 .36

12-17-2001 1420 17,300 .59

Appendix 1a. Instantaneous streamflows and total phosphorus concentrations for Illinois River near Watts, Oklahoma, from 1997-

2001—Continued.

Date Sample time

Instantaneous

streamflow

(ft3

/s)

Total phosphorus

concentration

(mg/L)
Appendixes 29

Appendix 1b. Instantaneous streamflows and total phosphorus concentrations for Flint Creek near Kansas, Oklahoma, from 1997-2001

[ft3/s, cubic foot per second; mg/L milligram per liter; all water-quality and streamflow data available at http://water.usgs.gov/ok/nwis]

Date Sample time

Instantaneous

streamflow

(ft3

/s)

Total phosphorus

concentration

(mg/L)

01-22-1997 1515 45 .09

02-12-1997 1420 58 .10

03-13-1997 1210 350 .09

04-23-1997 1100 104 .14

05-15-1997 1030 74 .10

06-23-1997 1210 57 .13

07-23-1997 1420 22 .14

08-21-1997 1210 64 .12

09-17-1997 1350 34 .11

10-15-1997 1810 41 .14

11-19-1997 1215 37 .11

12-02-1997 1520 90 .12

01-13-1998 1205 255 .10

02-09-1998 1245 74 .10

03-10-1998 1600 199 .10

04-22-1998 1625 74 .13

06-04-1998 0730 47 .16

07-14-1998 0825 29 .14

08-18-1998 1205 16 .12

09-22-1998 0805 24 .16

10-21-1998 0935 54 .13

11-16-1998 1040 77 .14

12-09-1998 1320 80 .11

01-07-1999 0835 87 .10

02-02-1999 0955 129 .13

03-24-1999 1530 209 .12

04-06-1999 1115 225 .20

05-04-1999 1145 2,760 .88

06-15-1999 1520 119 .66

08-12-1999 1320 48 .12

10-20-1999 1705 29 .10

12-02-1999 1000 32 .12

12-10-1999 1315 115 .18
30 Phosphorus Concentrations, Loads, and Yields in the Illinois River Basin, Arkansas and Oklahoma, 1997-2001

02-18-2000 0830 81 .14

04-17-2000 1200 48 .14

05-07-2000 0922 170 .19

06-17-2000 1200 5,150 1.66

06-21-2000 1700 5,450 .90

06-28-2000 1430 8,970 1.17

07-19-2000 1520 102 .15

08-15-2000 0730 47 .14

10-11-2000 1230 33 .12

10-27-2000 1100 73 .17

11-06-2000 2000 191 .26

12-12-2000 1020 64 .12

01-29-2001 1130 191 .11

02-15-2001 0830 678 .28

02-24-2001 1435 4,090 .85

04-17-2001 1335 85 .11

06-15-2001 1040 304 .26

08-14-2001 1035 26 .14

10-11-2001 1045 224 .22

10-30-2001 1430 34 .12

12-06-2001 1330 55 .15

12-17-2001 1045 1,030 .32

Appendix 1b. Instantaneous streamflows and total phosphorus concentrations for Flint Creek near Kansas, Oklahoma, from 1997-

2001—Continued.

Date Sample time

Instantaneous

streamflow

(ft3

/s)

Total phosphorus

concentration

(mg/L)
Appendixes 31

Appendix 1c. Instantaneous streamflows and total phosphorus concentrations for Illinois River at Chewey, Oklahoma, from 1997-2001

[ft3/s, cubic foot per second; mg/L, milligram per liter; all water-quality and streamflow data available at http://water.usgs.gov/ok/nwis]

Date Sample time

Instantaneous

streamflow

(ft3

/s)

Total phosphorus

concentration

(mg/L)

01-21-1997 1645 376 .09

02-11-1997 0915 671 .08

03-25-1997 1130 1,060 .10

04-24-1997 1430 638 .09

05-13-1997 0900 422 .13

06-25-1997 1010 478 .16

07-15-1997 0845 244 .14

08-26-1997 1440 250 .15

09-10-1997 1250 176 .12

10-21-1997 0945 253 .13

11-14-1997 1010 371 .10

12-03-1997 0900 577 .10

01-28-1998 0935 1,180 .09

02-19-1998 1550 807 .08

03-18-1998 1600 4,490 .13

04-23-1998 1450 564 .05

05-13-1998 1200 527 .17

06-18-1998 0955 256 .13

07-15-1998 1405 249 .13

08-18-1998 1105 169 .13

09-22-1998 1330 182 .23

10-20-1998 0920 358 .15

11-05-1998 1100 426 .14

12-16-1998 1050 775 .11

01-06-1999 1510 590 .07

02-02-1999 0920 1,320 .17

03-15-1999 1700 4,660 .20

04-06-1999 1400 3,600 .21

05-04-1999 0905 3,240 .43

06-24-1999 1530 1,610 .20

07-01-1999 1110 23,300 .93

08-13-1999 1100 282 .14

10-20-1999 1550 194 .12
32 Phosphorus Concentrations, Loads, and Yields in the Illinois River Basin, Arkansas and Oklahoma, 1997-2001

12-01-1999 1235 203 .15

12-11-1999 1140 886 .21

02-16-2000 1105 231 .17

04-12-2000 1445 1,400 .37

05-07-2000 1450 3,340 .47

06-18-2000 1235 16,800 .86

06-22-2000 1215 34,700 .96

08-16-2000 1310 251 .16

09-26-2000 1330 840 .23

10-23-2000 1430 230 .22

11-07-2000 1230 1,900 .27

12-07-2000 1255 415 .14

01-30-2001 1245 4,980 .40

02-15-2001 1320 6,670 .83

02-25-2001 1010 20,600 .46

04-18-2001 1715 518 .14

05-18-2001 1635 1,220 .24

06-27-2001 0945 376 .18

08-15-2001 1300 200 .25

10-11-2001 1605 1,110 .22

12-11-2001 1210 335 .26

12-17-2001 1740 17,400 .86

Appendix 1c. Instantaneous streamflows and total phosphorus concentrations for Illinois River at Chewey, Oklahoma, from 1997-

2001—Continued.

Date Sample time

Instantaneous

streamflow

(ft3

/s)

Total phosphorus

concentration

(mg/L)
Appendixes 33

Appendix 1d. Instantaneous streamflows and total phosphorus concentrations for Illinois River near Tahlequah, Oklahoma, from 1997-

2001

[ft3/s, cubic foot per second; mg/L milligram per liter; E, estimated; <, less than; all water-quality and streamflow data available at http://water.usgs.gov/ok/nwis]

Date Sample time

Instantaneous

streamflow

(ft3

/s)

Total phosphorus

concentration

(mg/L)

01-09-1997 1000 505 .04

02-10-1997 1550 766 .07

03-20-1997 1300 1,580 .07

04-25-1997 1340 742 .02

05-15-1997 0835 490 .06

06-25-1997 1515 626 .11

07-17-1997 1225 294 .06

08-22-1997 1450 568 .10

09-11-1997 1555 171 .07

10-22-1997 0925 287 .09

11-13-1997 0840 302 .05

12-03-1997 1120 929 .09

01-15-1998 1220 1,930 .07

02-10-1998 1445 657 .05

03-17-1998 1430 5,700 .15

04-22-1998 1230 849 .04

05-14-1998 0920 716 .03

06-16-1998 1537 321 .09

07-13-1998 1515 302 .10

08-17-1998 1610 198 .07

09-01-1998 1150 126 .08

10-19-1998 1200 424 .09

11-02-1998 1505 410 .09

12-15-1998 1340 1,320 .13

01-05-1999 0755 785 .08

02-01-1999 1240 1,940 .24

03-23-1999 1330 2,230 .17

04-05-1999 1335 3,590 .26

05-03-1999 1450 1,160 .09

06-08-1999 1125 970 .08

07-01-1999 1615 11,800 1.14

08-11-1999 1045 302 .11

10-20-1999 1050 162 .06
34 Phosphorus Concentrations, Loads, and Yields in the Illinois River Basin, Arkansas and Oklahoma, 1997-2001

12-01-1999 1400 223 E.04

12-11-1999 1400 856 .12

02-15-2000 1700 268 .09

04-13-2000 0910 1,150 .15

05-08-2000 0920 3,010 .28

06-18-2000 1635 14,800 .62

06-22-2000 1630 33,900 .80

07-20-2000 1200 677 .12

08-29-2000 1630 189 .09

09-26-2000 1045 1,040 .15

10-19-2000 1415 251 .11

10-27-2000 1600 582 .16

11-07-2000 1400 1,540 .19

12-12-2000 1215 420 .07

01-31-2001 1040 3,840 .21

02-16-2001 1315 10,200 .38

02-25-2001 1505 25,200 .75

04-23-2001 1430 588 .11

05-19-2001 1410 2,070 .23

06-26-2001 1530 645 .13

08-16-2001 1110 312 .10

10-12-2001 1100 2,660 .22

10-24-2001 0850 368 <.06

11-05-2001 1250 1,690 .35

12-05-2001 1330 828 .16

12-18-2001 1210 19,500 .54

Appendix 1d. Instantaneous streamflows and total phosphorus concentrations for Illinois River near Tahlequah, Oklahoma, from 1997-

2001—Continued.

[ft3/s, cubic foot per second; mg/L milligram per liter; E, estimated; <, less than; all water-quality and streamflow data available at http://water.usgs.gov/ok/nwis]

Date Sample time

Instantaneous

streamflow

(ft3

/s)

Total phosphorus

concentration

(mg/L)
Appendixes 35

Appendix 1e. Instantaneous streamflows and total phosphorus concentrations for Baron Fork at Eldon, Oklahoma, from 1997-2001

[ft3/s, cubic foot per second; mg/L, milligram per liter; <, less than; E, estimated; all water-quality and streamflow data available at http://water.usgs.gov/ok/nwis]

Date Sample time

Instantaneous

streamflow

(ft3

/s)

Total phosphorus

concentration

(mg/L)

01-09-1997 1145 153 .02

02-10-1997 1240 253 <.01

03-10-1997 1510 589 .04

04-25-1997 1230 270 <.01

05-13-1997 1625 173 .02

06-25-1997 1630 213 .02

07-16-1997 1555 144 .02

08-22-1997 1230 90 .02

09-12-1997 0910 43 .01

10-22-1997 0815 86 .02

11-13-1997 1330 100 .03

12-03-1997 1700 431 .02

01-15-1998 0945 648 .03

02-10-1998 1210 228 .01

03-19-1998 1300 2,630 .08

04-22-1998 1420 248 <.01

05-11-1998 1550 205 <.01

06-02-1998 1055 133 .05

07-21-1998 0830 35 .03

08-18-1998 0820 21 .01

09-21-1998 1340 37 .03

10-19-1998 1420 195 E.04

11-16-1998 1125 242 <.05

12-14-1998 1420 638 .03

01-05-1999 0945 211 <.05

02-01-1999 1120 565 .08

03-23-1999 1645 831 E.04

04-05-1999 1420 1,000 .09

05-03-1999 1105 481 E.05

06-07-1999 1135 361 E.04

08-11-1999 0830 44 <.05

10-20-1999 0845 30 <.05

12-02-1999 0750 44 <.05
36 Phosphorus Concentrations, Loads, and Yields in the Illinois River Basin, Arkansas and Oklahoma, 1997-2001

12-10-1999 1115 225 <.05

02-16-2000 0730 66 <.05

04-13-2000 1050 350 <.05

05-07-2000 1645 985 .08

06-17-2000 1540 7,520 1.12

06-21-2000 1345 49,100 1.65

06-28-2000 1630 5,350 .98

07-20-2000 0930 150 E.04

08-30-2000 1100 50 <.05

10-24-2000 1435 51 <.06

10-27-2000 1320 110 E.04

11-07-2000 0930 1,180 .10

12-20-2000 1530 192 <.06

01-30-2001 1015 1,270 .13

02-16-2001 1145 3,300 .17

02-25-2001 1240 4,900 .26

04-23-2001 1610 153 <.06

05-18-2001 1500 673 E.04

06-25-2001 1630 231 E.04

08-16-2001 0930 51 E.03

10-11-2001 1740 927 .15

10-23-2001 1555 136 .13

12-05-2001 1245 231 E.04

12-17-2001 1400 6,650 .15

Appendix 1e. Instantaneous streamflows and total phosphorus concentrations for Baron Fork at Eldon, Oklahoma, from 1997-2001—Continued.

Date Sample time

Instantaneous

streamflow

(ft3

/s)

Total phosphorus

concentration

(mg/L)
Appendixes 37

Appendix 2. Residuals plots of In(instantaneous load) – In(predicted load) in relation to In(instananeous load) for stations in the Illinois

River basin, periods 1997-1999, 1998-2000, and 1999-2001.

Illinois River near Watts

(07195500)

RESIDUALS OF LN (INST. LOAD) - LN (PRED. LOAD)

LN (INST. L)

Flint Creek near Kansas

(07196000)

LN (INST. L)

1997-1999 1997-1999

1998-2000 1998-2000

1999-2001 1999-2001

4.5 5.0 5.5 6.0 6.5 7.0 7.5

-1

-0.5

0

0.5

1

5 7 9 11 13

-2

-1.5

-1

-0.5

0

0.5

1

1 3 5 7 9 11

-1.5

-1

-0.5

0

0.5

1

1.5

-1

-0.5

0

0.5

1

1.5

-1

-0.5

0

0.5

1

1.5

-1

-0.5

0

0.5

1

4 6 8 10 12 1 3 5 7 9 11

1 3 5 7 9 11
38 Phosphorus Concentrations, Loads, and Yields in the Illinois River Basin, Arkansas and Oklahoma, 1997-2001

Appendix 2. Residuals plots of In(instantaneous load) – In(predicted load) in relation to In(instananeous load) for stations in the Illinois

River basin, periods 1997-1999, 1998-2000, and 1999-2001.—Continued

LN (INST. L) LN (INST. L)

Illinois River at Chewey

(07196090)

Illinois River near Tahlequah

(07196500)

4 6 8 10 12

-2

-1

0

1

2

1997-1999

4 6 8 10 12 14

1998-2000

1999-2001

-1.5

-0.75

0

0.75

1.5

2 4 6 8 10 12

1997-1999

1998-2000

-1

-0.5

0

0.5

1

1.5

1999-2001

-2

-1

0

1

2

-1.5

-0.75

0

0.75

1.5

-1.5

-0.75

0

0.75

1.5

2 4 6 8 10 12

4 6 8 10 12 14 2 4 6 8 10 12

RESIDUALS OF LN (INST. LOAD) - LN (PRED. LOAD)
Appendixes 39

Appendix 2. Residuals plots of In(instantaneous load) – In(predicted load) in relation to In(instananeous load) for stations in the Illinois

River basin, periods 1997-1999, 1998-2000, and 1999-2001.—Continued

Baron Fork at Eldon

(07197000)

EXPLANATION

LOWESS Curve

Line of central tendency

(residuals = 0)

02468

0 4 8 12 16

1 3 5 7 9 11 13

1997-1999

1998-2000

1999-2001

-1.5

-0.75

0

0.75

1.5

-2

-1

0

1

2

-2

-1

0

1

2

RESIDUALS OF LN (INST. LOAD) - LN (PRED. LOAD)

LN (INST. L)

Ln Natural log

Inst. Load Instantaneous load

Pred. Load Predicted Load
40 Phosphorus Concentrations, Loads, and Yields in the Illinois River Basin, Arkansas and Oklahoma, 1997-2001