U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2008–5174

Prepared in cooperation with the City of Tulsa, Oklahoma

Nutrient Concentrations, Loads, and Yields in the EuchaSpavinaw Basin, Arkansas and Oklahoma, 2002–2006
Cover Photograph Credits:

Top Left Picture is Beaty Creek near Jay, Delaware County, Oklahoma, downstream from the streamflow-gaging 

station, taken November 6, 2006. Photographer: Monica Allen, U.S. Geological Survey.

Top Right Picture is Spavinaw Creek near Colcord, Delaware County, Oklahoma, downstream from the streamflow-gaging station, taken November 6, 2006. Photographer: Monica Allen, U.S. Geological Survey.

Bottom Picture is Lake Eucha, Delaware County, Oklahoma, at dam site, taken July 2001. Photographer: Robert L. 

Blazs, U.S. Geological Survey.
Nutrient Concentrations, Loads, and Yields 

in the Eucha-Spavinaw Basin, Arkansas 

and Oklahoma, 2002–2006

By Robert L. Tortorelli

Prepared in cooperation with the City of Tulsa, Oklahoma

Scientific Investigations Report 2008–5174

U.S. Department of the Interior

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

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2008

This and other USGS information products are available at:

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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:

Tortorelli, R.L., 2008, Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–2006: U.S. Geological Survey Scientific Investigations Report 2008–5174, 56 p.
iii

Contents

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

Introduction ....................................................................................................................................................2

Purpose and Scope ..............................................................................................................................4

Study Area Description........................................................................................................................4

Streamflow in the Eucha-Spavinaw Basin.......................................................................................4

Acknowledgments................................................................................................................................9

Methods ..........................................................................................................................................................9

Water-Quality Data Collection and Analysis....................................................................................9

Streamflow Separation........................................................................................................................9

Statistical Tests ...................................................................................................................................10

Nutrient Concentrations in Undeveloped Basins..........................................................................10

Load and Yield Estimation..................................................................................................................10

Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin ......................................11

Concentrations....................................................................................................................................11

Nitrogen.......................................................................................................................................18

Phosphorus.................................................................................................................................18

Estimated Mean Annual Loads.........................................................................................................18

Nitrogen.......................................................................................................................................18

Phosphorus.................................................................................................................................26

Estimated Mean Seasonal Loads.....................................................................................................26

Nitrogen.......................................................................................................................................26

Phosphorus.................................................................................................................................30

Estimated Mean Annual Yields.........................................................................................................30

Nitrogen.......................................................................................................................................30

Phosphorus.................................................................................................................................30

Estimated Mean Flow-Weighted Concentrations .........................................................................31

Nitrogen.......................................................................................................................................31

Phosphorus.................................................................................................................................31

Estimated Mean Annual Nutrient Loads into Lake Eucha ...........................................................31

Summary........................................................................................................................................................31

Selected References ..................................................................................................................................38

Appendixes ...................................................................................................................................................41

1. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw 

Creek near Maysville, Arkansas, 2002–2006. ........................................................................42

2. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw 

Creek near Cherokee, Arkansas, 2002–2006. ........................................................................45

3. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw 

Creek near Sycamore, Oklahoma, 2002–2006. .......................................................................48

4. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw 

Creek near Colcord, Oklahoma, 2002–2006. ...........................................................................50

5. Streamflows, and total nitrogen and total phosphorus concentrations for Beaty Creek 

near Jay, Oklahoma, 2002–2006................................................................................................53
iv

Figures

1–2. Maps showing:

1. The Eucha-Spavinaw basin, Arkansas and Oklahoma, with locations of selected 

streamflow and water-quality stations in the basin and the towns with wastewatertreatment plants that discharge into streams in the basin....................................................3

2. Land use in the Eucha-Spavinaw basin, Arkansas and Oklahoma. .....................................5

3–11. Graphs showing:

3. Streamflow divided into total flow and base flow, and base-flow and runoff water 

samples collected at water-quality stations in Eucha-Spavinaw basin, Arkansas and 

Oklahoma, 2002–2006. ..................................................................................................................7

4. Total nitrogen concentrations in base-flow and runoff water samples collected 

at water-quality stations in the Eucha-Spavinaw basin, Arkansas and Oklahoma, 

2002–2006. ....................................................................................................................................14

5. Total phosphorus concentrations in base-flow and runoff water samples collected 

at water-quality stations in the Eucha-Spavinaw basin, Arkansas and Oklahoma, 

2002–2006. ....................................................................................................................................15

6. Distributions of base-flow total nitrogen concentrations in water samples collected at 

water-quality stations in the Eucha-Spavinaw basin, Arkansas and Oklahoma, periods 

2002–2004, 2003–2005, and 2004–2006.....................................................................................20

7. Distributions of runoff total nitrogen concentrations in water samples collected at 

water-quality stations in the Eucha-Spavinaw basin, Arkansas and Oklahoma, periods 

2002–2004, 2003–2005, and 2004–2006.....................................................................................21

8. Distribution of base-flow total phosphorus concentrations in water samples collected 

at water-quality stations in the Eucha-Spavinaw basin, Arkansas and Oklahoma, periods 2002–2004, 2003–2005, and 2004–2006. ............................................................................22

9. Distributions of runoff total phosphorus concentrations in water samples collected at 

water-quality stations in the Eucha-Spavinaw basin, Arkansas and Oklahoma, periods 

2002–2004, 2003–2005, and 2004–2006.....................................................................................23

10. Instantaneous total nitrogen concentrations in water samples collected at 

water-quality stations in the Eucha-Spavinaw basin, Arkansas and Oklahoma, periods 

2002–2004, 2003–2005, and 2004–2006.....................................................................................32

11. Instantaneous total phosphorus concentrations in water samples collected at waterquality stations in the Eucha-Spavinaw basin, Arkansas and Oklahoma, periods 

2002–2004, 2003–2005, and 2004–2006.....................................................................................34

Tables

1. Station information and streamflow statistics for surface-water and water-quality stations in the Eucha-Spavinaw basin, Arkansas and Oklahoma..............................................6

2. Regression models for estimating total nitrogen loads at water-quality stations in the 

Eucha-Spavinaw basin, Arkansas and Oklahoma, developed by using data collected 

during 2002–2006.........................................................................................................................12

3. Regression models for estimating total phosphorus loads at water-quality stations in 

the Eucha-Spavinaw basin, Arkansas and Oklahoma, developed by using data collected during 2002–2006. ...........................................................................................................13

4. Summary statistics of total nitrogen concentrations in base-flow and runoff water 

samples collected at water-quality stations in the Eucha-Spavinaw basin, Arkansas 
v

and Oklahoma, periods 2002–2004, 2003–2005, and 2004–2006...........................................16

5. Summary statistics of total phosphorus concentrations in base-flow and runoff water 

samples collected at water-quality stations in the Eucha-Spavinaw basin, Arkansas 

and Oklahoma, periods 2002–2004, 2003–2005, and 2004–2006...........................................17

6. Wilcoxon rank-sum test results comparing base-flow total nitrogen and total 

phosphorus concentrations to runoff total nitrogen and total phosphorus concentrations from water samples collected at water-quality stations in the Eucha-Spavinaw 

basin, Arkansas and Oklahoma, periods 2002–2004, 2003–2005, and 2004–2006.............19

7. Estimated mean annual total nitrogen loads and yields by using regression methods 

from concentrations in water-quality samples collected at water-quality stations in 

the Eucha-Spavinaw basin, Arkansas and Oklahoma, periods 2002–2004, 2003–2005, 

and 2004–2006. ............................................................................................................................24

8. Estimated mean annual total phosphorus loads and yields by using regression methods from concentrations in water-quality samples collected at water-quality stations 

in the Eucha-Spavinaw basin, Arkansas and Oklahoma, periods 2002–2004, 2003–2005, 

and 2004–2006. ............................................................................................................................25

9. Number of days of base flow and runoff designated by Base-Flow Index (BFI) program 

at water-quality stations in the Eucha-Spavinaw basin, Arkansas and Oklahoma, periods 2002–2004, 2003–2005, and 2004–2006. ............................................................................27

10. Estimated mean seasonal total nitrogen base-flow and runoff loads estimated by 

using regression methods from concentrations in water-quality samples collected at 

water-quality stations in the Eucha-Spavinaw basin, Arkansas and Oklahoma, periods 

2002–2004, 2003–2005, and 2004–2006.....................................................................................28

11. Estimated mean seasonal total phosphorus base-flow and runoff loads estimated by 

using regression methods from concentrations in water-quality samples collected at 

water-quality stations in the Eucha-Spavinaw basin, Arkansas and Oklahoma, periods 

2002–2004, 2003–2005, and 2004–2006.....................................................................................29

12. Estimated mean annual total nitrogen loads, mean annual streamflows, and estimated 

mean flow-weighted total nitrogen concentrations at water-quality stations in the 

Eucha-Spavinaw basin, Arkansas and Oklahoma, periods 2002–2004, 2003–2005, and 

2004–2006. ....................................................................................................................................33

13. Estimated mean annual total phosphorus loads, mean annual streamflows, and estimated mean flow-weighted total nitrogen concentrations at water-quality stations in 

the Eucha-Spavinaw basin, Arkansas and Oklahoma, periods 2002–2004, 2003–2005, 

and 2004–2006. ............................................................................................................................35

14. Summary of estimated mean annual total nitrogen and total phosphorus loads to Lake 

Eucha, Oklahoma, periods 2002–2004, 2003–2005, and 2004–2006. ....................................36
vi

Conversion Factors and Definitions

Multiply By To obtain

Length

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2) 2.590 square kilometer (km2) 

Flow rate

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

gallon per day (gal/d) 0.003785 cubic meter per day (m3/d)

Mass

pound (lb) 0.4536 kilogram (kg) 

ton, short (2,000 lb) 0.9072 megagram (Mg) 

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

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

Yield

pound per year per square mile [(lb/yr)/mi2] 0.1751 kilogram per year per kilometer [(kg/yr)/km2]

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 in milligrams per liter (mg/L). 

Method detection limit (MDL)—Minimum concentration of a substance that can be measured 

and reported with 99-percent confidence that the analyte concentration is greater than zero. 

It is determined from the analysis of a sample in a given matrix containing the analyte (U.S. 

Environmental Protection Agency, 1997). At the MDL concentration, the risk of a false positive is 

predicted to be less than or equal to 1 percent (Childress and others, 1999).

Long-term method detection level (LT–MDL)—A detection level derived by determining the standard 

deviation of a minimum of 24 MDL spike sample measurements over an extended period of time. LT–

MDL data are collected on a continuous basis to assess year-to-year variations in the LT–MDL. The 

LT–MDL controls false positive error. The chance of falsely reporting a concentration at or greater 

than the LT–MDL for a sample that did not contain the analyte is predicted to be less than or equal to 

1 percent (Childress and others, 1999).

Laboratory reporting level (LRL)—Generally equal to twice the yearly determined LT–MDL. The LRL 

controls false negative error. The probability of falsely reporting a non-detection for a sample that 

contained an analyte at a concentration equal to or greater than the LRL is predicted to be less 

than or equal to 1 percent. The value of the LRL will be reported with a “less than” remark code for 

samples in which the analyte was not detected. The National Water Quality Laboratory collects 

quality-control data from selected analytical methods on a continuing basis to determine long-term 

method detection levels (LT–MDLs) and establish laboratory reporting levels (LRLs). These values 

are re-evaluated annually based on the most current quality-control data and may, therefore, 

change (Childress and others, 1999).

Estimated concentration (“E” remark code)—Positive detections below the LRL are not censored. 

Detected analytes with concentrations between the LT–MDL and the LRL are reported as estimated 

(“E” remark code). This is because a detection in this region should have a ≤1-percent probability of 

being a false positive (Childress and others, 1999). There are several circumstances that dictate this 

code, this is one of the most common.

Minimum reporting level (MRL)—Smallest measured concentration of a constituent that may be 

reliably reported by using a given analytical method (Timme, 1995).
Abstract 

The City of Tulsa, Oklahoma, uses Lake Eucha and 

Spavinaw Lake in the Eucha-Spavinaw basin in northwestern 

Arkansas and northeastern Oklahoma for public water supply. 

Taste and odor problems in the water attributable to bluegreen algae have increased in frequency. Changes in the algae 

community in the lakes may be attributable to increases in 

nutrient levels in the lakes, and in the waters feeding the lakes. 

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

Tulsa, investigated and summarized nitrogen and phosphorus 

concentrations and provided estimates of nitrogen and phosphorus loads, yields, and flow-weighted concentrations in the 

Eucha-Spavinaw basin for three 3-year periods—2002–2004, 

2003–2005, and 2004–2006, to update a previous report that 

used data from water-quality samples for a 3-year period from 

January 2002 through December 2004. This report provides 

information needed to advance knowledge of the regional 

hydrologic system and understanding of hydrologic processes, 

and provides hydrologic data and results useful to multiple 

agencies for interstate agreements.

Nitrogen and phosphorus concentrations were significantly greater in runoff samples than in base-flow samples for 

all three periods at Spavinaw Creek near Maysville, Arkansas; Spavinaw Creek near Colcord, Oklahoma, and Beaty 

Creek near Jay, Oklahoma. Runoff concentrations were not 

significantly greater than base-flow concentrations at Spavinaw Creek near Cherokee, Arkansas; and Spavinaw Creek 

near Sycamore, Oklahoma except for phosphorus during 

2003–2005.

Nitrogen concentrations in base-flow samples significantly increased downstream in Spavinaw Creek from the 

Maysville to Sycamore stations then significantly decreased 

from the Sycamore to the Colcord stations for all three 

periods. Nitrogen in base-flow samples from Beaty Creek 

was significantly less than in samples from Spavinaw Creek. 

Phosphorus concentrations in base-flow samples significantly increased from the Maysville to Cherokee stations 

in Spavinaw Creek for all three periods, probably because 

of a wastewater-treatment plant point source between those 

stations, and then significantly decreased downstream from 

the Cherokee to Colcord stations. Phosphorus in base-flow 

samples from Beaty Creek was significantly less than phosphorus in base-flow samples from Spavinaw Creek downstream from the Maysville station. Nitrogen concentrations 

in runoff samples were not significantly different among the 

stations on Spavinaw Creek for most of the three periods, 

except during 2003–2005 when runoff samples at the Colcord 

station were less than at the Sycamore station; however, the 

concentrations at Beaty Creek were significantly less than at 

all other stations. Phosphorus concentrations in runoff samples 

were not significantly different among the three downstream 

stations on Spavinaw Creek and were significantly different at 

the Maysville station on Spavinaw Creek and the Beaty Creek 

station, only during 2004–2006. Phosphorus and nitrogen 

concentrations in runoff samples from all stations generally 

increased with increasing streamflow. 

 Estimated mean annual nitrogen total loads for the three 

3-year periods were substantially greater at the Spavinaw 

Creek stations than at Beaty Creek and increased downstream 

from Maysville to Colcord in Spavinaw Creek, with the load 

at the Colcord station about 2 times that at Maysville station. Estimated mean annual nitrogen base-flow loads at the 

Spavinaw Creek stations were about 5 to 11 times greater 

than base-flow loads at Beaty Creek. The runoff component 

of the annual nitrogen total load for Beaty Creek was 85 to 

89 percent; whereas, the range in the runoff component at the 

Spavinaw Creek stations was 60 to 71 percent. 

Estimated mean annual phosphorus total loads for the 

three 3-year periods were greater at the Spavinaw Creek 

stations from Cherokee to Colcord than at Beaty Creek and 

increased downstream from Maysville to Colcord in Spavinaw 

Creek, with the load at the Colcord station about 2.5 times 

that at Maysville station. Estimated mean annual phosphorus 

base-flow loads at the Spavinaw Creek stations were about 2.5 

to 19 times greater than at Beaty Creek. Phosphorus base-flow 

loads increased about 4 to 8 times from Maysville to Cherokee 

in Spavinaw Creek; the base-flow loads were about the same 

at the three downstream stations. The runoff component of the 

annual phosphorus total load for Beaty Creek was 98 percent; 

whereas, the range in the runoff component at the Spavinaw 

Creek stations was 66 to 93 percent.

Estimated mean seasonal nitrogen base-flow and runoff 

loads generally were least in autumn for all three periods and 

greatest in spring at all stations in the Eucha-Spavinaw basin 

for 2002–2004 and 2003–2005; and greatest in spring and 

winter for 2004–2006. Seasonal base-flow loads at stations 

on Spavinaw Creek were about 3 to 20 times greater than at 

Nutrient Concentrations, Loads, and Yields in the EuchaSpavinaw Basin, Arkansas and Oklahoma, 2002-2006

By Robert L. Tortorelli
2 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006

the station on Beaty Creek and increased downstream from 

Maysville to Colcord in Spavinaw Creek, with the seasonal 

base-flow load at the Colcord station about 2 times that at 

Maysville station. Estimated mean seasonal phosphorus 

base-flow and runoff loads generally were least in autumn 

and greatest in spring for base-flow loads and greatest in the 

summer for runoff loads at all stations in the Eucha-Spavinaw 

basin. Seasonal phosphorus base-flow loads at Spavinaw 

Creek stations were about 2 to 30 times greater than at the 

station on Beaty Creek; with the seasonal base-flow load at the 

Cherokee station about 4 to 10 times that at Maysville station.

Estimated mean annual nitrogen total yields ranged from 

4,340 to 7,490 pounds per year per square mile, with greatest 

yield at the Sycamore station in 2003–2005, and the least yield 

at Beaty Creek near Jay for all three periods. Estimated mean 

annual nitrogen base-flow yields ranged from 549 to 2,640 

pounds per year per square mile, and estimated mean annual 

nitrogen runoff yields ranged from 3,680 to 5,150 pounds per 

year per square mile. Estimated mean annual phosphorus total 

yields ranged from 227 to 478 pounds per year per square 

mile, with the greatest yield at Beaty Creek, and the least yield 

at Spavinaw Creek near Maysville. Most of the yield at Beaty 

Creek was delivered during runoff. Estimated mean annual 

phosphorus base-flow yields at the three downstream Spavinaw Creek stations ranged from 46.1 to 112 pounds per year 

per square mile and were about 5 to 11 times greater than at 

Beaty Creek. 

Estimated mean flow-weighted nitrogen concentrations 

at all stations in the basin for three 3-year periods were about 

7 to 10 times greater than the 75th percentile of flow-weighted 

nitrogen concentrations (0.50 milligram per liter) in mostly 

undeveloped basins of the United States. Estimated mean 

flow-weighted phosphorus concentrations at all stations in the 

basin for all three periods were about 4 to 10 times greater 

than the 75th percentile of flow-weighted phosphorus concentrations (0.037 milligram per liter) in mostly undeveloped 

basins of the United States. 

Spavinaw Creek and Beaty Creek contributed an estimated mean annual nitrogen total load of about 1,350,000 

to 1,490,000 pounds per year, and about 65 to 72 percent of 

the annual nitrogen total load was transported to Lake Eucha 

by runoff. Spavinaw Creek and Beaty Creek contributed an 

estimated mean annual phosphorus total load of about 77,700 

to 88,700 pounds per year with about 86 to 89 percent of the 

annual phosphorus total load being transported to Lake Eucha 

by runoff. 

Introduction 

The City of Tulsa, Oklahoma, uses Lake Eucha and 

Spavinaw Lake in the Eucha-Spavinaw basin in northwestern Arkansas and northeastern Oklahoma for public water 

supply (fig. 1). Construction of Spavinaw Dam on Spavinaw 

Creek began in 1922 and was completed in 1924. A series 

of pipelines 60-miles long, from the base of Spavinaw Dam 

to the City of Tulsa, were constructed to transfer water from 

Spavinaw Lake to a treatment plant in Tulsa. Spavinaw Lake 

supplied Tulsans with a safe, reliable water supply until 1950 

(Oklahoma Water Resources Board, 2002). During that year, 

city officials decided to create an impoundment of Spavinaw 

Creek 4 miles upstream from Spavinaw Lake to serve as “an 

environmental and hydrologic barrier” (City of Tulsa City Services, 2008a) for Spavinaw Lake to ensure a constant supply 

of clean water. This second dam came to be known as Eucha 

Dam and was finished in 1954 to impound Lake Eucha 

(fig. 1).

The Eucha-Spavinaw system continues to be designated 

as a system for public water supply along with recreation, fish 

and wildlife, and aesthetics. Eucha-Spavinaw provides a yield 

of 59 million gallons per day (mgd) to the Tulsa metropolitan 

area. In a drought, the system can produce a maximum of 100 

mgd (City of Tulsa City Services, 2008b). 

Consumer complaints of taste and odor in the finished 

water have been reported. The Tulsa Metropolitan Utility Authority (TMUA) has spent millions of dollars from 

1998–2005 to eliminate taste and odor problems in the drinking water from the Eucha-Spavinaw system. City staff has 

determined that taste and odor problems attributable to bluegreen algae have increased in frequency. Changes in the algae 

community in the lakes may be attributable to increases in 

nutrient levels in the lakes, and in the waters feeding the lakes 

(City of Tulsa City Services, 2008c). Studies of phosphorous 

loading began with a 1997 Oklahoma Conservation Commission report indicating increasing phosphate content of Spavinaw Creek (Wagner and Woodruff, 1997). Other studies were 

made in 2001–2002 (Oklahoma Water Resources Board, 2002; 

Storm and others, 2001 and 2002).

Nitrogen and phosphorus enters streams in discharges 

from wastewater-treatment plants (point-source components) 

and in agricultural and urban runoff (nonpoint-source components) (Oklahoma Water Resources Board, 2002). Streams 

in the Eucha-Spavinaw basin are susceptible to contamination from point and nonpoint sources. Elevated nitrogen and 

phosphorus concentrations promote algae growth in streams 

(Sharpley, 1995; U.S. Geological Survey, 1999), and accelerate eutrophication of lakes (Daniel and others, 1998; U.S. 

Geological Survey, 1999).

One possible major contributor of nutrients to the creeks 

feeding Lake Eucha and Spavinaw Lake is the phosphorousrich waste produced by commercial poultry growing operations in the watershed. This waste is routinely spread onto 

fields as fertilizer, and can be a source of nitrogen and phosphorous washed into streams as nonpoint-source pollution, 

which ultimately reaches the water-supply lakes and promotes 

growth of unwanted algae. Today, the poultry operations in the 

Eucha-Spavinaw basin have the capacity to produce more than 

84 million birds, along with some 1,500 tons of nitrogen and 

phosphorous-rich waste per year (Tulsa Metropolitan Utility 

Authority, 2001).

Historical water-quality data collection in the EuchaSpavinaw basin has been biased toward sampling during base 
Introduction 

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4 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006

flow (nonrunoff). Because of insufficient historic sampling 

during runoff, calculations using historic data may have underestimated true nutrient concentrations, loads, and yields. In 

July 2001, the U.S. Geological Survey (USGS), in cooperation 

with the TMUA, supplemented fixed period, monthly waterquality sampling with six runoff samplings per year to better 

determine water quality over a broader range of streamflows 

in the basin. The period 2002–2006 encompasses a period 

where the runoff sampling protocol was in effect. The USGS, 

in cooperation with the City of Tulsa, Oklahoma, investigated 

and summarized nitrogen and phosphorus concentrations and 

provided estimates of nitrogen and phosphorus loads, yields, 

and flow-weighted concentrations in the Eucha-Spavinaw 

basin for three 3-year periods from January 2002 through 

December 2006.

Purpose and Scope

The purpose of this report is to summarize nitrogen and 

phosphorus concentrations and provide estimates of nitrogen 

and phosphorus loads, yields, and flow-weighted concentrations in the Eucha-Spavinaw basin, Spavinaw Creek and 

Beaty Creek tributary, from January 2002 through December 

2006 for three 3-year periods—2002–2004, 2003–2005, and 

2004–2006. This report updates the work of Tortorelli (2006), 

which used water-quality and streamflow data from 2002 to 

2004, and comprises a preliminary analysis of data collected 

for a multi-year monitoring program.

Nitrogen and phosphorus concentrations are compared 

among stations in the Eucha-Spavinaw basin and to concentrations measured at mostly undeveloped basins of the United 

States. Nitrogen and phosphorus loads are computed by using 

S-LOADEST, a program to compute mean constituent loads 

in rivers by using the rating-curve method (Dave Lorenz, 

USGS, written commun., 2006). S-LOADEST, based on 

LOADEST (LOAD ESTimator), uses instantaneous nutrient 

concentrations and daily mean streamflows to estimate annual 

and seasonal (spring, summer, autumn, and winter) average 

nutrient loads for the study period (Runkel and others, 2004). 

The report provides information needed to advance knowledge of the regional hydrologic system and understanding of 

hydrologic processes, and provides hydrologic data and results 

useful to multiple agencies for interstate agreements.

Study Area Description

The Eucha-Spavinaw basin is a 388-square-mile drainage 

basin divided between northeastern Oklahoma (63 percent), 

and northwestern Arkansas (37 percent) (fig. 1) (R. Esralew, 

U.S. Geological Survey, written commun., 2008). Lake Eucha 

and Spavinaw Lake collect and store water from Spavinaw 

Creek (the main drainage channel for the basin) to supply the 

Tulsa metropolitan area and other local water users. 

The basin is in the southwestern part of the Ozark Plateaus physiographic province (Fenneman, 1938), and is underlain by the cherty limestone of the Springfield Plateau aquifer 

(Adamski and others, 1995).

The basin is dominated by about equal proportions of 

agricultural (pasture and row crops) and forest land uses and 

is interspersed with minor amounts of urban land uses (Storm 

and others, 2002; DeLaune and others, 2006) 

(fig. 2). Livestock production on pasture is the primary 

form of agriculture in the basin; the drainage area is densely 

populated with poultry/beef cattle operations that use poultry 

litter as a fertilizer source for pastures (DeLaune and others, 

2006). Poultry operations in the Eucha-Spavinaw basin have 

the capacity to produce more than 84 million birds, along with 

some 1,500 tons of nitrogen and phosphorous-rich waste per 

year (Tulsa Metropolitan Utility Authority, 2001). There also 

is a municipal wastewater-treatment plant, operated by the city 

of Decatur, Arkansas, that discharges nitrogen and phosphorus 

containing wastewater to the Eucha-Spavinaw basin (Storm 

and others, 2002; DeLaune and others, 2006). 

Streams in the basin receive potentially large concentrations of nitrogen and phosphorus from point sources (such as 

septic tanks and wastewater-treatment plants) and nonpoint 

sources (such as runoff from fertilized pastures and row 

crops). Nitrogen and phosphorus concentrations in Ozark 

streams are typically greater in streams draining agricultural 

lands than in streams draining forested lands (Petersen and 

others, 1998), because runoff from pastures fertilized with 

animal manure probably are substantial sources of nitrogen 

and phosphorus to the streams in this basin (Storm and others, 

2002). Streams receiving municipal wastewater from a treatment plant can have nitrogen and phosphorus concentrations 

substantially greater than concentrations in streams draining 

agricultural areas (Petersen and others, 1998). Spavinaw Creek 

(fig. 1) receives discharges from wastewater-treatment plants, 

whereas, Beaty Creek does not.

Streamflow in the Eucha-Spavinaw Basin

Streamflow in the Eucha-Spavinaw basin was highly 

varied from 2002 to 2006, and generally increased with basin 

drainage area (table 1, fig. 3). The maximum daily mean 

streamflow during the study period was in July 2004 at all 

stations, and the minimum daily mean streamflow during 

the study period was in August 2006 at the three upstream 

Spavinaw Creek stations, July 2006 at Spavinaw Creek 

near Colcord; and zero flow was at Beaty Creek near Jay 

at several times in September–October 2002, August 2003, 

October 2005, and July–October 2006 (table 1, fig. 3). Greatest monthly mean streamflows generally were from March 

through June and least monthly mean streamflows generally 

were from August through December at all stations (Blazs and 

others, 2003–2006, U.S. Geological Survey, 2007 and 2008). 
Introduction 

5

Spavinaw Lake07191300

Arkansas Oklahoma

Lake Eucha07191285

Eucha

07191288 Jay

07191222

Colcord071912213

Sycamore07191220

Cherokee07191179

Maysville07191160

Spavinaw

Eucha

Jay

Sycamore

Colcord

Decatur

CherokeeCity

Maysville

Gravette Hiwasse

Base from U.S. Geological Survey digital data, 1:100,000, 1983, andU.S. Environmental Protection Agency enhanced River Reach File 3Albers Equal-Area Conic projection, North American Datum of 1983

Land use from U.S. Geological Survey National Land Cover Dataset, 1992

07191288

07191285

071912213

0 50 5

10 KILOMETERS

10 MILES

U.S. Geological Survey streamflow-gaging

station and number

U.S. Geological Survey streamflow-gaging

station and water-quality monitoring stationand number (table 1)

U.S. Geological Survey lake-level station

and number

Town with water-treatment plant that

discharges into streams in the EuchaSpavinaw Basin

EXPLANATION

36°30’

’51°49 ’03°49 ’54°49 ’00°59

36°15’

LakeHudson

SpavinawLake

LakeEucha

Creek

Beaty

Creek

Spavinaw

Land-cover classes

WaterUrbanForest/shrublandGrassland/pastureRow cropsWetlands

Boundary of sampling

watershed

Boundary ofwatershed

Study area

Oklahoma Arkansas

Index map

Tulsa

Figure 2. Land use in the Eucha-Spavinaw basin, Arkansas and Oklahoma.
6 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006 Table 1. Station information and streamflow statistics for surface-water and water-quality stations in the Eucha-Spavinaw basin, Arkansas and Oklahoma. [WY, water year (October 1 through September 30); ddmmss, degrees, minutes, seconds; mi2, square mile; ft3/s, cubic foot per second] Mean annual streamflow (ft3/s) Minimum and maximum daily mean streamflow for study period, 2002–2006 (ft3/s) Station name (number) Period of record for station (WY) Latitude (ddmmss) Longitude (ddmmss) Drainage area (mi2

)

2002–2004 2003–2005 2004–2006 Period of 

record 1

Minimum 

(date)

Maximum 

(date)

(calendar year)

Spavinaw Creek near 2002–present 362152 943304 88.2 61.9 63.0 59.9 52.7 4.2 4,150Maysville, Ark. (07191160) (08/04/2006) (07/03/2004) Spavinaw Creek near 2002–present 362031 943515 104 74.4 77.8 74.8 64.5 7.0 5,180Cherokee, Ark. (07191179) (08/01/2006) (07/03/2004) Spavinaw Creek near 1962–present 362005 943829 133 96.6 99.1 92.5 110 7.7 6,300Sycamore, Okla. (07191220) (08/18/2006) (07/03/2004) Spavinaw Creek near 2002–present 361921 944106 163 127 132 125 106 8.7 7,720Colcord, Okla. (071912213) (07/29/2006) (07/03/2004) Beaty Creek near 1998–present 362119 944634 59.2 38.7 44.1 42.4 39.6 0 4,080Jay, Okla. (07191222) at times (07/03/2004) 

2002, 20032005, 2006

1 Based on streamflow statistics through Water Year 2007.
Introduction 7

Spavinaw Creek near

Maysville, Arkansas

100

101

102

103

104

Spavinaw Creek near

Cherokee, Arkansas

100

101

102

103

104

STREAMFLOW, IN CUBIC FEET PER SECOND

Spavinaw Creek near

Sycamore, Oklahoma

100

101

102

103

104

2002 2003 2004 2005 2006

TIME

Figure 3. Streamflow divided into total flow and base flow, and base-flow and runoff water samples collected at water-quality 

stations in Eucha-Spavinaw basin, Arkansas and Oklahoma, 2002–2006.—Continued
8 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006

Spavinaw Creek near

Colcord, Oklahoma

100

101

102

103

104

STREAMFLOW, IN CUBIC FEET PER SECOND

Beaty Creek near Jay, Oklahoma

10-2

10-1

100

101

102

103

104

2002 2003 2004 2005 2006

TIME

Total flow

Base flow

Base-flow water-quality sample

Runoff water-quality sample

(daily mean streamflow)

(instantaneous streamflow)

(daily mean streamflow)

(daily mean streamflow)

EXPLANATION

Figure 3. Streamflow divided into total flow and base flow, and base-flow and runoff water samples collected at water-quality stations 

in Eucha-Spavinaw basin, Arkansas and Oklahoma, 2002–2006.
Methods 9

Acknowledgments

The author thanks several people for their contributions 

to the data collection and data analysis presented in this report. 

Numerous City of Tulsa personnel participated in monthly 

water-quality sampling, and numerous USGS personnel participated in the runoff water-quality sampling. The Oklahoma 

Water Science Center Data Section at all three field offices 

added to the effort, but special thanks goes to the Tulsa Field 

Office for their contribution to the data collection. Thanks to 

Rachel Esralew of the Oklahoma City Office for her assistance 

in the compilation of the nitrogen and phosphorus data set. 

Additional special thanks go to Dave Lorenz for his help in the 

use of the load estimation program, S-LOADEST; and Dave 

Mueller for his insight into load estimation equations. 

Methods 

This section describes the water-quality data-collection 

and analysis protocols, method of streamflow separation into 

base flow and runoff, statistical tests used to compare groups 

of data, statistics of nutrient concentrations of undeveloped 

basins used to compare the basin data, and methods used to 

estimate total nitrogen and phosphorus loads and yields.

Water-Quality Data Collection and Analysis

The USGS operates several continuous streamflow 

gaging stations and collects water-quality data in the EuchaSpavinaw basin in Arkansas and Oklahoma. Five continuous 

streamflow gaging stations were selected for use in this report: 

Spavinaw Creek near Maysville, Arkansas; Spavinaw Creek 

near Cherokee, Arkansas; Spavinaw Creek near Sycamore, 

Oklahoma; Spavinaw Creek near Colcord, Oklahoma; and 

Beaty Creek near Jay, Oklahoma (table 1, fig. 1). Stream gages 

were operated and streamflows were measured according to 

methods described in Rantz and others (1982). 

Surface-water quality data used for load and yield estimation should represent different flow conditions (from low to 

high) and be reasonably balanced among seasons (A.V. Vecchia, USGS, written commun., 2005). Prior to July 2001, only 

fixed period, monthly water-quality samples were collected 

at these stations by staff from the City of Tulsa, Oklahoma, 

and included few runoff events. Starting in July 2001 at the 

Cherokee, Colcord, and Jay streamflow gages and December 

2001 at the Maysville and Sycamore streamflow gages, six 

water-quality samples were targeted to be collected annually 

during runoff at these stations by the USGS. Because of climate variability, more than six samples were collected in some 

wet years and fewer than six samples were collected in some 

dry years (fig. 3). Representative water-quality samples were 

collected by USGS during runoff by using equal-width increment methods (Edwards and Glysson, 1999). Samples for total 

nitrogen and phosphorus were whole-water samples and were 

not filtered in the field. Total nitrogen and phosphorus concentrations represent dissolved and particulate components.

The City of Tulsa Water Quality Laboratory analyzed the 

water-quality samples (U.S. Environmental Protection Agency, 

1983 and 1993). Total nitrogen concentrations were calculated by adding Kjeldahl-Nitrogen (measure of ammonia plus 

organic nitrogen) and nitrite plus nitrate analyses. Nitrogen 

and total phosphorus concentrations were reported if values 

were greater than the laboratory reporting level (LRL). The 

LRL is set to reduce false positive error, and is equal to twice 

the yearly determined long-term method detection level (Childress and others, 1999).

Streamflow data and nitrogen and phosphorus concentration data collected from 2002 through 2006 were analyzed 

for this report. All streamflow and water-quality data from 

samples are available through the internet at http://water.usgs.

gov/ok/nwis. 

Quality assurance was achieved mainly through following a prescribed method of protocols and procedures as 

described in the National Field Manual (U.S. Geological 

Survey, 2006). Additionally, the collection and analysis of 

quality-control (QC) samples are mandated components of 

USGS water-quality field studies (U.S. Geological Survey, 

2006) and compose an important part of the overall quality 

assurance of the project. The goal of QC sampling is to identify, quantify, and document bias and variability in data that 

result from the collection, processing, shipping, and handling 

of samples. Field blanks and field sequential replicates were 

collected by the USGS at the rate of about 20 percent of the 

number of environmental samples. The City of Tulsa collected 

QC samples at the rate of about 11 percent.

The two blank samples collected were from the Beaty 

Creek site in 2006. Total nitrogen components analyses were 

nondetectable. Total phosphorus analyses had values of 

0.011mg/L (USGS) and 0.006 mg/L (City of Tulsa). Those 

results indicate that some contamination occurred as a result 

of sample collection or sample processing and the potential 

contamination should be considered when evaluating the 

phosphorus data in this report. Concentrations for this report 

ranged from 0.019 to 1.30 mg/L. The median relative percent 

difference between sequential replicate analyses for the main 

component of total nitrogen (nitrite plus nitrate) was acceptable at less than one percent. The median relative percent difference between sequential replicate total phosphorus analyses 

was acceptable at 2.7 percent. 

Streamflow Separation

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

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

1995) (fig. 3). Base flow is the sustained runoff or fair-weather 

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

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

components were separated because base-flow concentrations 
10 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006

are more indicative of point sources and runoff concentrations 

are more indicative of nonpoint sources. 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 Tortorelli, 1997). 

The Base-Flow Index 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 in this report were defined as days when base 

flow contributed greater than or equal to 70 percent of total 

flow; runoff days were defined as days when runoff contributed greater than 30 percent of total flow (Tortorelli and 

Pickup, 2006; Tortorelli, 2006).

Statistical Tests

Streamflow data and water-quality data were divided into 

three 3-year periods: 2002–2004, 2003–2005, and 2004–2006, 

on the basis of calendar year. Three-year periods were used to 

average annual climate variation and emulate a 3-year moving 

average. Three-year periods and a 3-year moving average 

were done to determine if there are any indications of major 

changes in concentrations and loads with time, because more 

data are needed for true trend analysis.

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

1992), used to compare two groups of data, was used to 

determine the statistical significance of differences between 

base-flow and runoff nitrogen and phosphorus concentrations 

at each station in the study period. The Kruskal-Wallis test 

(Helsel and Hirsch, 1992), used to compare multiple datasets 

at one time, was used to determine the statistical significance 

of differences in nitrogen and phosphorus concentrations 

among stations in the Eucha-Spavinaw basin in base-flow and 

runoff data groups. 

The tests were selected because neither test requires 

normally distributed data. The null hypotheses of the tests 

are that there are no differences in median concentrations 

among the datasets 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 Kruskal-Wallis test was rejected and the medians were 

described as being significantly different, the multiple-stage 

Kruskal-Wallis test (that is individual Kruskal-Wallis tests on 

smaller subsets of data) was applied to determine which sites 

were different and which were not (Helsel and Hirsch, 1992).

Nutrient Concentrations in Undeveloped Basins

Nitrogen and phosphorus concentrations were compared 

among stations in the Eucha-Spavinaw basin and compared 

with the median and 75th percentile of flow-weighted total 

nitrogen and phosphorus concentrations of mostly undeveloped basins. These comparisons were from streams draining 

85 mostly undeveloped basins from across the United States 

selected from three programs of the USGS — the Hydrologic 

Benchmark Network, the National Water-Quality Assessment 

program, and the USGS Research Program (Clark and others, 

2000). 

The Hydrologic Benchmark Network program, started 

by the USGS in 1958, was established to track water-quality 

trends in streams draining basins free from anthropogenic 

influence and to study cause and effect relation between 

several physiologic, meteorologic, and hydrologic variables 

(Cobb and Biesecker, 1971). The Hydrologic Benchmark 

Network is primarily composed of mostly undeveloped basins 

encompassing a wide variety of natural environments nationwide (Mast and Turk, 1999).

The National Water-Quality Assessment program, started 

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).

The USGS Research Program provided research data 

for the assessment in Clark and others (2000) from 20 USGS 

research basins nationwide. These small basins ranged in size 

from about 0.04 to 8.5 square miles, and were predominately 

in the Appalachian and Rocky Mountains (Clark and others, 

2000).

Load and Yield Estimation

Linear regression was used to evaluate relations between 

nitrogen and phosphorus loads (dependent variables) and 

streamflow and time variables (explanatory variables). Daily 

nitrogen and phosphorus loads could not be calculated directly 

because water-quality data were collected intermittently. 

Regression methods allow estimation of daily water-quality 

constituent loads based on continuous streamflow records. 

Regression methods require daily mean streamflow data and 

discrete water-quality samples collected during several years. 

Sample dates, times, streamflows, and nitrogen and phosphorus concentrations used in this analysis are provided in appendixes 1-5 and are available through the internet at 

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

Load is the amount of a constituent transported past a 

selected point in a stream in a given amount of time, usually 

one year. Constituent load (L) is the product of streamflow 

(Q) and the constituent concentration in the water (C) multiplied by a conversion factor to convert cubic feet per second 

(ft3/s) and milligrams per liter (mg/L) to pounds per day (lb/d). 

The S-LOADEST program (Dave Lorenz, USGS, written 
Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin 11

commun., 2006) was used to estimate constituent loads by 

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

1991) in the Eucha-Spavinaw basin. S-LOADEST is based on 

LOADEST (Runkel and others, 2004) and is incorporated in 

the computer program S-Plus (Insightful Corporation, 2005) to 

facilitate graphical analysis and tabular results. S-LOADEST 

estimates rating-curve parameters and mean daily loads by 

using several regression methods and a ratio estimator. If some 

of the constituent concentrations included in this analysis were 

censored, parameters would be estimated by the adjusted maximum likelihood estimation method (Cohn, 1988; Cohn and 

others, 1992); however, none were present (censored values 

are the value of the LRL reported with a “less than” remark 

code for samples in which the concentration was not detected). 

In the absence of censored data, the method converts to the 

maximum likelihood estimation method (Dempster and others, 

1977; Wolynetz, 1979). An estimate of the uncertainty in the 

estimated load was obtained by using the method described 

by Likes (1980) and Gilroy and others (1990). S-LOADEST 

contains nine predefined rating-curve models that can test the 

relation between constituent load and streamflow. The model 

used for this report (equation 1) includes time variables and 

seasonality variables to simulate the relation between the natural logarithms of L, Q and Q2

:

ln(L) = bo + b1 lnQ + b2 lnQ2 + b3T + b4T2 + b5 sin SS + b6 cos SS (1)

where

ln = natural logarithm

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

b0 = regression constant, dimensionless;

b1, b2, b3, b4, b5, b6 = regression coefficients, dimensionless;

Q = daily mean streamflow, in cubic feet per 

second (ft3/s); 

T = dectime, time parameter in decimal years;

sin = sine;

cos = cosine; and 

SS = seasonality parameter (2πdectime).

Linear regression models developed by S-LOADEST 

for the estimation of nitrogen and phosphorus loads for all 

3-year periods at each station are listed in tables 2 and 3. Data 

from all stations generally fit the model well for nitrogen. 

Data from all stations in Oklahoma generally fit the model 

for phosphorus better than data from the stations in Arkansas. 

Other S-LOADEST predefined regression models that used 

various combinations of streamflow, time, and seasonal coefficients had lesser residuals than the model used for this report; 

however, the “best” model indicated in S-LOADEST was 

different for each nutrient and station. Therefore, one general 

model (equation 1) was selected for all stations and nutrients: 

(1) to use a consistent general model to estimate loads for all 

stations in a basin for each nutrient, (2) because an analysis of 

the “best” models compared with this general model indicated 

a very small improvement in reduction in variance for each 

nutrient, and (3) because seasonality parameters were in most 

of the “best” models for each nutrient.

Three-year periods were used to average annual climate 

variation and to emulate a 3-year moving average. Different 

model coefficients for each 3-year period were used (1) to 

allow the slope between L and Q to vary with time instead of 

having one slope for the 5-year period, and (2) because most 

of the model variances were lower by using different 3-year 

models instead of a single 5-year model, indicating a better 

model fit.

Estimated mean annual nitrogen and phosphorus loads 

and estimates of the standard deviations of the mean loads 

were calculated by S-LOADEST by using all base-flow and 

runoff data. The daily load values generated by S-LOADEST 

were separated into base-flow and runoff sample sets according to the number of base-flow days and the number of runoff 

days in each 3-year period. Estimated mean annual base-flow 

loads were calculated as the mean of the base-flow day sample 

set. Estimated mean annual runoff loads were calculated as 

the mean of the runoff day sample set. Estimated seasonal 

base-flow and runoff loads were calculated in the same way on 

the basis of the number of base-flow and runoff days in each 

season. In this report, spring is March through May, summer 

is June through August, autumn is September through November, and winter is December through February.

Nitrogen and phosphorus yields for the study period 

at each station were calculated by dividing mean annual 

nitrogen and phosphorus loads by drainage area (table 1). 

Flow-weighted concentrations for the study period at each 

station were calculated by dividing mean annual nitrogen and 

phosphorus loads by mean annual streamflow and multiplying 

by a conversion factor to adjust the units.

Nutrient Concentrations, Loads, and 

Yields in the Eucha-Spavinaw Basin

Nitrogen and phosphorus in the Eucha-Spavinaw basin 

are described in terms of three 3-year periods (2002–2004, 

2003–2005, and 2004–2006) of mean concentrations, loads, 

and yields in base-flow and runoff samples, and in terms of 

mean flow-weighted concentrations. All annual and seasonal 

loads, yields, and flow-weighted concentrations are estimated 

mean values that were calculated by S-LOADEST. All total 

nitrogen values are referred to as nitrogen and total phosphorus values are referred to as phosphorus in this report.

Concentrations

The summary statistics of nitrogen and phosphorus 

concentrations divided into base-flow and runoff samples are 

presented in tables 4 and 5. Graphs showing the nitrogen and 

phosphorus concentrations from base-flow and runoff water 

samples are presented in figures 4 and 5.
12 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006 Table 2. Regression models for estimating total nitrogen loads at water-quality stations in the Eucha-Spavinaw basin, Arkansas and Oklahoma, developed by using data collected during 2002–2006. [no., number; obs., observations; ln, natural logarithm; L, daily load in pound per day; Q, mean daily streamflow in cubic foot per second; T, dectime, time parameter in decimal years; SS, seasonality parameter, (2*pi*dectime); R2, coefficient of determination; +, Indicates >99.5% but <100%] Station name (number) 3-year period No. of obs. Total nitrogen load regression model Estimated residual variance 1

R2

(percent)

Spavinaw Creek near 2002–2004 54 ln(L) = 7.92 + 1.06*lnQ + 0.0091*lnQ2 + 0.0623*T + 0.108*T2 + 0.156*sin SS + 0.0014*cos SS 0.018 99Maysville, Ark. 2003–2005 51 ln(L) = 8.21 + 1.11*lnQ – 0.0009*lnQ2 + 0.0115*T – 0.0754*T2 + 0.0914*sin SS + 0.0665*cos SS 0.017 99+(07191160) 2004–2006 47 ln(L) = 7.91 + 1.10*lnQ + 0.0062*lnQ2 – 0.186*T – 0.0120*T2 – 0.0362*sin SS + 0.139*cos SS 0.072 98Spavinaw Creek near 2002–2004 57 ln(L) = 8.28 + 1.00*lnQ – 0.0129*lnQ2 + 0.0760*T + 0.0881*T2 + 0.114*sin SS + 0.0943*cos SS 0.025 99Cherokee, Ark. 2003–2005 53 ln(L) = 8.58 + 1.03*lnQ – 0.0092*lnQ2 + 0.0360*T – 0.0963*T2 + 0.0572*sin SS + 0.167*cos SS 0.028 99(07191179) 2004–2006 46 ln(L) = 8.48 + 1.06*lnQ – 0.0203*lnQ2 – 0.0743*T – 0.0144*T2 – 0.0345*sin SS + 0.188*cos SS 0.026 99Spavinaw Creek near 2002–2004 40 ln(L) = 8.89 + 1.05*lnQ + 0.0181*lnQ2 + 0.0554*T + 0.0485*T2 + 0.0482*sin SS + 0.0834*cos SS 0.022 99Sycamore, Okla. 2003–2005 36 ln(L) = 9.15 + 1.06*lnQ + 0.0180*lnQ2 + 0.0534*T – 0.0794*T2 + 0.0465*sin SS + 0.139*cos SS 0.012 99+(07191220) 2004–2006 33 ln(L) = 8.73 + 1.07*lnQ + 0.0079*lnQ2 – 0.0641*T – 0.0187*T2 + 0.0048*sin SS + 0.165*cos SS 0.016 99+Spavinaw Creek near 2002–2004 58 ln(L) = 8.47 + 1.02*lnQ + 0.0027*lnQ2 + 0.0770*T + 0.105*T2 + 0.155*sin SS + 0.0651*cos SS 0.024 99Colcord, Okla. 2003–2005 55 ln(L) = 8.77 + 1.05*lnQ + 0.0047*lnQ2 + 0.0319*T – 0.101*T2 + 0.114*sin SS + 0.125*cos SS 0.028 99(071912213) 2004–2006 48 ln(L) = 8.58 + 1.08*lnQ – 0.0052*lnQ2 – 0.0881*T – 0.0383*T2 + 0.0232*sin SS + 0.166*cos SS 0.021 99+Beaty Creek near 2002–2004 57 ln(L) = 5.19 + 1.07*lnQ + 0.0074*lnQ2 + 0.0673*T + 0.244*T2 + 0.295*sin SS – 0.0035*cos SS 0.051 99Jay, Okla. 2003–2005 55 ln(L) = 5.38 + 1.10*lnQ + 0.0034*lnQ2 + 0.0508*T - 0.201*T2 + 0.268*sin SS + 0.0780*cos SS 0.060 99(07191222) 2004–2006 45 ln(L) = 5.28 + 1.14*lnQ – 0.0050*lnQ2 – 0.199*T - 0.0342*T2 + 0.0244*sin SS + 0.126*cos SS 0.058 99

 1 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 regression 

model.
Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin 13

Table 3. Regression models for estimating total phosphorus loads at water-quality stations in the Eucha-Spavinaw basin, Arkansas and Oklahoma, developed by using data collected during 2002–2006.[no., number; obs., observations; ln, natural logarithm; L, daily load in pound per day; Q, mean daily streamflow in cubic foot per second; T, dectime, time parameter in decimal years; SS, seasonality parameter, (2*pi*dectime); R2, coefficient of determination]

Station name

(number)

3-year 

period

No. of 

obs. Total phosphorus load regression model

Estimated 

residual 

variance 1

R2

(percent)

Spavinaw Creek near 2002–2004 53 ln(L) = 3.76 + 1.61*lnQ + 0.128*lnQ2 – 0.0553*T – 0.195*T2 – 0.208*sin SS – 0.155*cos SS 0.240 96Maysville, Ark. 2003–2005 50 ln(L) = 3.64 + 1.65*lnQ + 0.120*lnQ2 + 0.0134*T + 0.299*T2 – 0.211*sin SS – 0.248*cos SS 0.277 96(07191160) 2004–2006 43 ln(L) = 3.83 + 1.60*lnQ + 0.151*lnQ2 + 0.236*T – 0.141*T2 – 0.100*sin SS – 0.0556*cos SS 0.207 97Spavinaw Creek near 2002–2004 57 ln(L) = 5.05 + 1.13*lnQ + 0.135*lnQ2 – 0.204*T – 0.0070*T2 – 0.111*sin SS – 0.0926*cos SS 0.177 94Cherokee, Ark. 2003–2005 53 ln(L) = 4.99 + 1.21*lnQ + 0.131*lnQ2 – 0.180*T + 0.0760*T2 – 0.115*sin SS + 0.0466*cos SS 0.210 95(07191179) 2004–2006 42 ln(L) = 5.06 + 1.26*lnQ + 0.104*lnQ2 + 0.0579*T + 0.0244*T2 – 0.139*sin SS – 0.0463*cos SS 0.074 98Spavinaw Creek near 2002–2004 39 ln(L) = 5.68 + 1.35*lnQ + 0.162*lnQ2 – 0.171*T – 0.126*T2 – 0.122*sin SS – 0.0302*cos SS 0.055 98Sycamore, Okla. 2003–2005 35 ln(L) = 5.49 + 1.41*lnQ + 0.186*lnQ2 – 0.215*T + 0.149*T2 – 0.0654*sin SS – 0.0466*cos SS 0.064 99(07191220) 2004–2006 33 ln(L) = 4.77 + 1.31*lnQ + 0.109*lnQ2 – 0.0153*T + 0.0011*T2 – 0.0280*sin SS – 0.0400*cos SS 0.100 98Spavinaw Creek near 2002–2004 58 ln(L) = 5.30 + 1.37*lnQ + 0.0780*lnQ2 – 0.136*T – 0.192*T2 – 0.0839*sin SS – 0.0835*cos SS 0.116 97Colcord, Okla. 2003–2005 55 ln(L) = 5.07 + 1.40*lnQ + 0.0877*lnQ2 – 0.175*T + 0.189*T2 – 0.0628*sin SS – 0.142*cos SS 0.125 98(071912213) 2004–2006 44 ln(L) = 4.93 + 1.32*lnQ + 0.107*lnQ2 + 0.0023*T – 0.0386*T2 + 0.0553*sin SS – 0.0109*cos SS 0.121 98Beaty Creek near 2002–2004 57 ln(L) = 1.32 + 1.36*lnQ + 0.0688*lnQ2 – 0.0967*T + 0.0636*T2 – 0.317*sin SS – 0.131*cos SS 0.128 99Jay, Okla. 2003–2005 55 ln(L) = 1.26 + 1.32*lnQ + 0.0633*lnQ2 + 0.104*T + 0.0380*T2 – 0.256*sin SS – 0.121*cos SS 0.107 99(07191222) 2004–2006 43 ln(L) = 1.25 + 1.27*lnQ + 0.0624*lnQ2 + 0.0784*T – 0.0825*T2 – 0.211*sin SS – 0.0337*cos SS 0.145 99

 1 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 regression model
14 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006 TOTAL NITROGEN CONCENTRATION, IN MILLIGRAMS PER LITER AS NITROGEN

STREAMFLOW, IN CUBIC FEET PER SECOND

STREAMFLOW, IN CUBIC FEET PER SECOND

0

2

4

6

8

10

12

Spavinaw Creek near

Maysville, Arkansas

Spavinaw Creek near

Cherokee, Arkansas

100 101 102 103 104 0

2

4

6

8

10

Spavinaw Creek near

Sycamore, Oklahoma

101 102 103 104

Spavinaw Creek near

Colcord, Oklahoma

10-2 10-1 100 101 102 103 104 0

2

4

6

8

Beaty Creek near

Jay, Oklahoma EXPLANATION

Nitrogen concentration,

0.50 milligram per liter

[75th percentile of flow-weighted nitrogen

concentrations from relatively undeveloped basins

of the United States (Clark and others, 2000)]

Base-flow nitrogen concentration

Runoff nitrogen concentration

2002

2003

2004

2005

2006

2002

2003

2004

2005

2006

Figure 4. Total nitrogen concentrations in base-flow and runoff water samples collected at water-quality stations in the 

Eucha-Spavinaw basin, Arkansas and Oklahoma, 2002–2006.
Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin 15

STREAMFLOW, IN CUBIC FEET PER SECOND

STREAMFLOW, IN CUBIC FEET PER SECOND

EXPLANATION

Phosphorus concentration,

0.037 milligram per liter

[75th percentile of flow-weighted phosphorus

concentrations from relatively undeveloped basins

of the United States (Clark and others, 2000)]

Base-flow phosphorus concentration

Runoff phosphorus concentration

2002

2003

2004

2005

2006

2002

2003

2004

2005

2006

0.01

0.1

1

Spavinaw Creek near

Maysville, Arkansas

2

Spavinaw Creek near

Cherokee, Arkansas

100 101 102 103 104

0.01

0.1

1

Spavinaw Creek near

Sycamore, Oklahoma

2

101 102 103 104

Spavinaw Creek near

Colcord, Oklahoma

10-2 10-1 100 101 102 103 104 0.01

0.1

1

Beaty Creek

near Jay, Oklahoma

2

ARTNECNOCSUROHPSOHPLATOT RETILREPSMARGILLIMNI,NOIT SUROHPSOHPSA

Figure 5. Total phosphorus concentrations in base-flow and runoff water samples collected at water-quality stations in 

the Eucha-Spavinaw basin, Arkansas and Oklahoma, 2002–2006.
16 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006 Table 4. Summary statistics of total nitrogen concentrations in base-flow and runoff water samples collected at water-quality stations in the Eucha- Spavinaw basin, Arkansas and Oklahoma, periods 2002–2004, 2003–2005, and 2004–2006. [Obs., number of observations; mg/L, milligram per liter; N, nitrogen] Station name (number) 3-year period Base-flow concentrations Runoff concentrations Minimum Median Mean Maximum Obs. Minimum Median Mean Maximum Obs. (mg/L as N) (mg/L as N) Spavinaw Creek near 2002–2004 2.57 3.36 3.51 4.86 26 3.01 4.18 4.37 7.40 28 Maysville, Ark. 2003–2005 2.57 3.34 3.40 4.86 26 3.01 4.28 4.57 9.34 25 (07191160) 2004–2006 1.98 2.82 3.22 4.86 25 0.69 4.50 4.41 9.34 22 Spavinaw Creek near 2002–2004 3.11 4.12 4.07 5.46 26 2.48 4.27 4.40 6.82 31 Cherokee, Ark. 2003–2005 3.28 4.10 4.11 5.46 25 2.48 4.30 4.62 10.45 28 (07191179) 2004–2006 2.56 4.02 4.06 5.46 22 2.68 4.59 4.70 10.45 24 Spavinaw Creek near 2002–2004 3.65 4.44 4.59 5.50 12 3.20 4.88 4.79 7.10 28 Sycamore, Okla. 2003–2005 3.92 4.34 4.60 5.45 10 3.54 4.96 5.01 9.31 26 (07191220) 2004–2006 3.18 4.34 4.51 5.45 10 3.03 5.17 5.06 9.31 23 Spavinaw Creek near 2002–2004 2.82 3.78 3.79 5.20 28 2.30 4.16 4.30 6.29 30 Colcord, Okla. 2003–2005 2.90 3.72 3.75 5.18 26 2.30 4.50 4.48 9.62 29 (071912213) 2004–2006 2.28 3.58 3.61 5.18 24 2.08 4.55 4.49 9.62 24 Beaty Creek near 2002–2004 0.87 1.79 1.92 4.02 23 1.13 3.03 3.02 4.93 34 Jay, Okla. 2003–2005 0.87 1.82 1.94 4.02 26 1.13 3.16 2.98 4.93 29 (07191222) 2004–2006 0.67 1.46 1.89 4.02 22 1.16 3.28 3.09 4.93 23
Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin 17

Table 5. Summary statistics of total phosphorus concentrations in base-flow and runoff water samples collected at water-quality stations in the EuchaSpavinaw basin, Arkansas and Oklahoma, periods 2002–2004, 2003–2005, and 2004–2006.[Obs., number of observations; mg/L, milligram per liter; P, phosphorus]

Station name 

(number) 3-year period

Base-flow concentrations Runoff concentrations

Minimum Median Mean Maximum

Obs.

Minimum Median Mean Maximum

Obs.

(mg/L as P) (mg/L as P)

Spavinaw Creek near 2002–2004 0.019 0.025 0.027 0.041 26 0.017 0.045 0.153 0.920 27Maysville, Ark. 2003–2005 0.019 0.028 0.029 0.059 26 0.017 0.056 0.203 1.200 24(07191160) 2004–2006 0.019 0.029 0.035 0.120 21 0.017 0.052 0.202 1.200 22Spavinaw Creek near 2002–2004 0.114 0.223 0.216 0.315 26 0.030 0.170 0.235 1.300 31Cherokee, Ark. 2003–2005 0.081 0.160 0.169 0.257 25 0.030 0.181 0.272 1.300 28(07191179) 2004–2006 0.081 0.143 0.139 0.189 20 0.082 0.150 0.281 1.300 22Spavinaw Creek near 2002–2004 0.092 0.142 0.132 0.153 12 0.088 0.153 0.229 0.980 27Sycamore, Okla. 2003–2005 0.081 0.114 0.113 0.140 10 0.088 0.138 0.269 1.200 25(07191220) 2004–2006 0.081 0.110 0.110 0.140 11 0.083 0.120 0.272 1.200 22Spavinaw Creek near 2002–2004 0.081 0.100 0.101 0.147 28 0.075 0.126 0.238 0.990 30Colcord, Okla. 2003–2005 0.065 0.086 0.090 0.147 26 0.075 0.123 0.269 1.100 29(071912213) 2004–2006 0.065 0.081 0.093 0.260 21 0.074 0.100 0.258 1.100 23Beaty Creek near 2002–2004 0.021 0.038 0.039 0.089 23 0.024 0.070 0.178 1.000 34Jay, Okla. 2003–2005 0.021 0.040 0.042 0.089 26 0.024 0.077 0.183 1.000 29(07191222) 2004–2006 0.028 0.045 0.050 0.100 21 0.032 0.098 0.226 1.000 22
18 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006

Nitrogen

Nitrogen concentrations were significantly greater 

(p ≤ 0.05) in runoff samples than in base-flow samples for 

all three periods, 2002–2004, 2003–2005, and 2004–2006, at 

Spavinaw Creek near Maysville, Arkansas; Spavinaw Creek 

near Colcord, Oklahoma, and Beaty Creek near Jay, Oklahoma 

(tables 4 and 6, fig. 4). Nitrogen concentrations in runoff samples were not significantly greater than in base-flow samples 

at Spavinaw Creek near Cherokee, Arkansas, and Spavinaw 

Creek near Sycamore, Oklahoma.

Nitrogen concentrations in base-flow samples during all 

3-year periods significantly increased (p ≤ 0.05) downstream 

in Spavinaw Creek from the Maysville to Sycamore stations, 

except 2004–2006 (fig. 6). Nitrogen concentrations in baseflow samples during all 3-year periods significantly decreased 

(p ≤ 0.05) downstream in Spavinaw Creek from the Sycamore to Colcord stations (fig. 6). Nitrogen concentrations in 

base-flow samples from the Eucha-Spavinaw basin generally 

increased with increasing streamflow (fig. 4, table 4). As base 

flow increased by addition of ground water, additional nitrate 

in the ground water may increase the concentration of nitrogen 

as nitrogen is more prone to leach than phosphorus. Spavinaw 

Creek received nitrogen concentrations from a point source 

(the City of Decatur, Arkansas, municipal wastewater treatment plant), but Beaty Creek did not. Nitrogen concentrations 

in base-flow samples from Beaty Creek were significantly 

less than nitrogen concentrations in base-flow samples from 

Spavinaw Creek during all 3-year periods (fig. 6).

Nitrogen concentrations in runoff samples during 

2002–2004 and 2004–2006 were not significantly different 

among the stations on Spavinaw Creek; but during 2003–2005, 

the concentrations at the Colcord station were significantly 

less than concentrations at the Sycamore station (fig. 7). 

However, the concentrations at Beaty Creek were significantly 

less than at all other stations during all 3-year periods (fig. 7). 

Nitrogen concentrations in runoff samples from all stations 

generally increased with increasing streamflow (fig. 4). The 

larger concentrations of nitrogen during runoff indicates addition of nitrogen from nonpoint sources. 

Phosphorus

 Phosphorus concentrations were significantly greater 

(p ≤ 0.05) in runoff samples than in base-flow samples during 

all 3-year periods at Spavinaw Creek near Maysville, Arkansas; Spavinaw Creek near Colcord, Oklahoma, and Beaty 

Creek near Jay, Oklahoma (tables 5 and 6, fig. 5). Phosphorus 

concentrations in runoff samples were not significantly greater 

than in base-flow samples at Spavinaw Creek near Cherokee, 

Arkansas, and Spavinaw Creek near Sycamore, Oklahoma, 

except during 2003–2005.

Phosphorus concentrations in base-flow samples during 

all 3-year periods significantly increased (p ≤ 0.05) from the 

Maysville to Cherokee stations in Spavinaw Creek probably 

because of a point source between those stations (the City of 

Decatur, Arkansas, municipal wastewater treatment plant) 

(fig. 8). Phosphorus concentrations in base-flow samples 

significantly decreased (p ≤ 0.05) downstream in Spavinaw 

Creek from the Cherokee to Colcord stations (fig. 8), as has 

been reported for other point-source affected streams in the 

region (Haggard, 2000; Haggard and others, 2001; Tortorelli 

and Pickup, 2006). Phosphorus concentrations in base-flow 

samples from Spavinaw Creek generally decreased with 

increasing streamflow (fig. 5, table 5). As base flow increased 

by addition of ground water, dilution reduced the concentration of phosphorus from point sources. Spavinaw Creek 

received phosphorus concentrations from a point source, but 

Beaty Creek did not. Phosphorus concentrations in baseflow samples from Beaty Creek were significantly less than 

phosphorus in base-flow samples from the Spavinaw Creek 

stations downstream from Maysville station during all 3-year 

periods (fig. 8).

Phosphorus concentrations in runoff samples during all 

3-year periods were not significantly different among the three 

downstream stations on Spavinaw Creek; and were significantly different at the Maysville station on Spavinaw Creek 

and the Beaty Creek station, only during 2004–2006 (fig. 9). 

Phosphorus concentrations in runoff samples from all stations 

generally increased with increasing streamflow 

(fig. 5). Possible causes of larger concentrations of phosphorus 

during runoff than in base flow are the addition of phosphorus 

from nonpoint sources, resuspension of phosphorus from the 

streambed sediment, and streambank erosion. Wagner and 

Woodruff (1997) and Storm and others (2001) attribute most 

of the phosphorus transported in the basin to nonpoint sources 

during runoff.

Estimated Mean Annual Loads

Estimated mean annual nitrogen and phosphorus loads 

are discussed in this section. Total annual loads are divided 

into base-flow and runoff components as presented in tables 7 

and 8.

Nitrogen

Estimated mean annual nitrogen total loads were substantially greater at Spavinaw Creek stations than at Beaty Creek 

(about 2 to 5 times), primarily because of greater streamflow 

at the stations on the Spavinaw Creek (tables 1 and 7). Annual 

total loads increased downstream (table 7) from Maysville to 

Colcord in Spavinaw Creek, with the annual total load at the 

Colcord station about 2 times that of Maysville station during 

all 3-year periods (table 7). 

Estimated mean annual nitrogen base-flow loads were 

substantially less in Beaty Creek than in the Spavinaw Creek 

stations (table 7). Annual base-flow loads at stations on Spavinaw Creek were about 5 to 11 times greater than base-flow 

loads at the station on Beaty Creek. Annual nitrogen base-flow 

loads increased in a downstream direction during all 3-year 
Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin 19

Table 6. Wilcoxon rank-sum test results comparing base-flow total nitrogen and total phosphorus concentrations to runoff total 

nitrogen and total phosphorus concentrations from water samples collected at water-quality stations in the Eucha-Spavinaw 

basin, Arkansas and Oklahoma, periods 2002–2004, 2003–2005, and 2004–2006.

[z, normal test statistic with correction for ties; p, probability value; p-values in bold indicate statistically significant differences between groups of data 

at 95-percent confidence level (probability value less than or equal to 0.05)]

Station name (number)

3-year period 

 2002-2004 2003-2005 2004-2006

Nitrogen Phosphorus Nitrogen Phosphorus Nitrogen Phosphorus

Spavinaw Creek near Maysville, Ark. z = -3.480 z = -4.383 z = -3.976 z = -3.965 z = -3.071 z = -3.028

 (07191160) p = 0.0005 p < 0.0001 p = 0.0001 p = 0.0001 p = 0.0021 p < 0.0025

Spavinaw Creek near Cherokee, Ark. z = -1.354 z = 1.835 z = -1.604 z = -0.624 z = -1.264 z = -1.299

 (07191179) p = 0.1757 p = 0.0665 p = 0.1088 p = 0.5328 p = 0.2061 p = 0.1938

Spavinaw Creek near Sycamore, Okla. z = -0.398 z = -1.583 z = -0.671 z = -2.266 z = -1.116 z = -1.666

 (07191220) p = 0.6903 p = 0.1133 p = 0.5022 p = 0.0234 p = 0.2642 p = 0.0957

Spavinaw Creek near Colcord, Okla. z = -2.070 z = -3.557 z = -2.318 z = -4.579 z = -2.186 z = -3.808

 (071912213) p = 0.0385 p = 0.0004 p = 0.0204 p < 0.0001 p = 0.0288 p = 0.0001

Beaty Creek near Jay, Okla. z = -4.140 z = -3.801 z = -3.717 z = -3.685 z = -3.611 z = -3.621

 (07191222) p < 0.0001 p = 0.0001 p = 0.0002 p = 0.0002 p = 0.0003 p = 0.0003
20 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006

EXPLANATION

(23)

75th percentile

Median

25th percentile

Outlier

Data value less than

or equal to 1.5 times

the interquartile range

Data value greater than

or equal to 1.5 times

the interquartile range

Outlier

Number of samples

Interquartile

range

A Distributions with the

same letter are not

significantly different

(p less than or equal

0.05). Two letters

indicate tests run on

smaller subsets of data

0.50 milligram per liter

nitrogen concentration

[75th percentile of flowweighted concentrations

from relatively undeveloped

basins of the United States

(Clark and others, 2000)]

0

2

4

6

8

10

Base Flow 2002-2004

(26)

(12) (28) (26)

(23)

A

B

D

C A

B

TOTAL NITROGEN CONCENTRATION, IN MILLIGRAMS PER LITER AS NITROGEN

0

2

4

6

8

10

Base Flow 2003-2005

(26)

(10) (26)

(25)

(26)

A

B

E

C

D

0

2

4

6

8

10

Base Flow 2004-2006

(25)

(10) (24) (22)

(22)

A

B

D

B

C

Spavinaw Creek near

Sycamore, Okla. (07191220)

Beaty Creek near

Jay, Okla. (07191222)

Spavinaw Creek near

Maysville, Ark. (07191160)

Spavinaw Creek near

Colcord, Okla. (071912213)

Spavinaw Creek near

Cherokee, Ark. (07191179)

Figure 6. Distributions of base-flow total nitrogen concentrations in water samples collected at water-quality stations in the EuchaSpavinaw basin, Arkansas and Oklahoma, periods 2002–2004, 2003–2005, and 2004–2006.
Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin 21

A Distributions with the

same letter are not

significantly different

(p less than or equal

0.05). Two letters

indicate tests run on

smaller subsets of data

0.50 milligram per liter

nitrogen concentration

[75th percentile of flowweighted concentrations

from relatively undeveloped

basins of the United States

(Clark and others, 2000)]

EXPLANATION

(28)

75th percentile

Median

25th percentile

Outlier

Data value less than

or equal to 1.5 times

the interquartile range

Data value greater than

or equal to 1.5 times

the interquartile range

Outlier

Number of samples

Interquartile

range

0

2

4

6

8

10

12

Runoff 2002-2004

(28) (28)

(30)

(31)

(34)

A

B

A A A

T

O

T

A

L

NIT

ROG

E

N

C

ONC

E

N

TRA

TIO

N, IN

MILLIGRA

M

S PE

R

LIT

E

R

A

S

NIT

ROG

E

N

0

2

4

6

8

10

12

Runoff 2003-2005

(25) (26) (29)

(28)

(29) A

C

B

A A

B B

0

2

4

6

8

10

12

Runoff 2004-2006

(22) (23) (24)

(24)

(23)

A

B

A A A

Spavinaw Creek near

Sycamore, Okla. (07191220)

Beaty Creek near

Jay, Okla. (07191222)

Spavinaw Creek near

Maysville, Ark. (07191160)

Spavinaw Creek near

Colcord, Okla. (071912213)

Spavinaw Creek near

Cherokee, Ark. (07191179)

Figure 7. Distributions of runoff total nitrogen concentrations in water samples collected at water-quality stations in the EuchaSpavinaw basin, Arkansas and Oklahoma, periods 2002–2004, 2003–2005, and 2004–2006.
22 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006

EXPLANATION

(23)

75th percentile

Median

25th percentile

Outlier

Data value less than

or equal to 1.5 times

the interquartile range

Data value greater than

or equal to 1.5 times

the interquartile range

Outlier

Number of samples

Interquartile

range

A Distributions with the

same letter are not

significantly different

(p less than or equal

0.05).

0.037 milligram per liter

phosphorus concentration

[75th percentile of flowweighted concentrations

from relatively undeveloped

basins of the United States

(Clark and others, 2000)]

0.01

0.1

1

Base Flow 2002-2004

(26)

(12) (28)

(26)

(23)

A

D

B

E

C

TOTAL PHOSPHORUS CONCENTRATION, IN MILLIGRAMS PER LITER AS PHOSPHORUS 0.01

0.1

1

Base Flow 2003-2005

(26)

(10) (26)

(25)

(26)

A

D

B

E

C

0.01

0.1

1

Base Flow 2004-2006

(21) (11)

(21)

(20)

(21)

A

D

B

E

C

Spavinaw Creek near

Sycamore, Okla. (07191220)

Beaty Creek near

Jay, Okla. (07191222)

Spavinaw Creek near

Maysville, Ark. (07191160)

Spavinaw Creek near

Colcord, Okla. (071912213)

Spavinaw Creek near

Cherokee, Ark. (07191179)

Figure 8. Distribution of base-flow total phosphorus concentrations in water samples collected at water-quality stations in the 

Eucha-Spavinaw basin, Arkansas and Oklahoma, periods 2002–2004, 2003–2005, and 2004–2006.
Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin 23

EXPLANATION

A Distributions with the

same letter are not

significantly different

(p less than or equal

0.05).

0.037 milligram per liter

phosphorus concentration

[75th percentile of flowweighted concentrations

from relatively undeveloped

basins of the United States

(Clark and others, 2000)]

(28)

75th percentile

Median

25th percentile

Outlier

Data value less than

or equal to 1.5 times

the interquartile range

Data value greater than

or equal to 1.5 times

the interquartile range

Outlier

Number of samples

Interquartile

range

0.01

0.1

1

Runoff 2002-2004

(27) (27) (30) (31) (34)

5

B

A

B B

A

TOTAL PHOSPHORUS CONCENTRATION, IN MILLIGRAMS PER LITER AS PHOSPHORUS 0.01

0.1

1

Runoff 2003-2005

(24) (25) (29) (28) (29)

5

B

A

B B

A

0.01

0.1

1

Runoff 2004-2006

(22) (22) (23) (22) (22)

5

B

A

B B B

Spavinaw Creek near

Sycamore, Okla. (07191220)

Beaty Creek near

Jay, Okla. (07191222)

Spavinaw Creek near

Maysville, Ark. (07191160)

Spavinaw Creek near

Colcord, Okla. (071912213)

Spavinaw Creek near

Cherokee, Ark. (07191179)

Figure 9. Distributions of runoff total phosphorus concentrations in water samples collected at water-quality stations in the 

Eucha-Spavinaw basin, Arkansas and Oklahoma, periods 2002–2004, 2003–2005, and 2004–2006.
24 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006 Table 7. Estimated mean annual total nitrogen loads and yields by using regression methods from concentrations in water-quality samples collected at water-quality stations in the Eucha-Spavinaw basin, Arkansas and Oklahoma, periods 2002–2004, 2003–2005, and 2004–2006. [mi2, square mile; lb/yr, pound per year; lb/yr/mi2, pound per year per square mile; SEP, standard error of prediction; N, nitrogen; Differences between total load and the sum of the base-flow load plus runoff loads are due to rounding.] Station name (number) Drainage area (mi2

)

 3-year 

period

Estimated mean annual

Load delivered 

during runoff 

(percent) Total load 1 (+/– SEP1) 

(lb/yr as N)

Total yield 

(lb/yr/mi2 as N)

Base-flow 

load 2

(lb/yr as N)

Base-flow 

yield 

(lb/yr/mi2 as N)

Runoff 

load 3 

(lb/yr as N)

Runoff 

yield 

(lb/yr/mi2 as N)

Spavinaw Creek near 88.2 2002–2004 521,000 (13,700) 5,910 187,000 2,120 335,000 3,800 64Maysville, Ark. 2003–2005 552,000 (15,100) 6,260 202,000 2,290 350,000 3,970 63(07191160) 2004–2006 520,000 (31,600) 5,900 186,000 2,120 334,000 3,790 64Spavinaw Creek near 104 2002–2004 656,000 (18,400) 6,310 262,000 2,520 394,000 3,790 60Cherokee, Ark. 2003–2005 737,000 (24,600) 7,090 267,000 2,570 469,000 4,510 64(07191179) 2004–2006 709,000 (23,500) 6,820 243,000 2,250 466,000 4,480 66Spavinaw Creek near 133 2002–2004 914,000 (28,300) 6,870 312,000 2,350 602,000 4,530 66Sycamore, Okla. 2003–2005 996,000 (23,100) 7,490 311,000 2,340 685,000 5,150 69(07191220) 2004–2006 932,000 (26,000) 7,010 271,000 2,040 661,000 4,970 71Spavinaw Creek near 163 2002–2004 1,090,000 (31,000) 6,690 430,000 2,640 659,000 4,040 61Colcord, Okla. 2003–2005 1,190,000 (39,800) 7,300 413,000 2,530 781,000 4,790 65(071912213) 2004–2006 1,140,000 (34,800) 6,990 370,000 2,270 767,000 4,710 67Beaty Creek near 59.2 2002–2004 257,000 (15,300) 4,340 39,300 664 218,000 3,680 85Jay, Okla. 2003–2005 296,000 (19,400) 5,000 38,700 654 257,000 4,340 87(07191222) 2004–2006 285,000 (19,200) 4,810 32,500 549 253,000 4,270 89

1 Calculated by S-LOADEST and are statistics of all data in the 3-year period.2 Means of the base-flow loads are calculated from base-flow days data only.3 Means of the runoff loads are calculated from runoff days data only.
Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin 25

Table 8. Estimated mean annual total phosphorus loads and yields by using regression methods from concentrations in water-quality samples collected at water-quality stations in the Eucha-Spavinaw basin, Arkansas and Oklahoma, periods 2002–2004, 2003–2005, and 2004–2006.[mi2, square mile; lb/yr, pound per year; lb/yr/mi2, pound per year per square mile; SEP, standard error of prediction; P, phosphorus. Differences between total load and the sum of the base-flow load plus runoff loads are due to rounding.]

Station name 

(number)

Drainage 

area

 (mi2

)

 3-year 

period

Estimated mean annual Load 

delivered 

during runoff 

(percent)

Total load 1 

(+/– SEP1) 

(lb/yr as P)

Total yield

(lb/yr/mi2 as P)

Base-flow 

load 2

(lb/yr as P)

Base-flow 

yield 

(lb/yr/mi2 as P)

Runoff 

load 3

(lb/yr as P)

Runoff 

yield 

(lb/yr/mi2 as P)

Spavinaw Creek near 88.2 2002–2004 20,000 (8,430) 227 1,480 16.8 18,600 211 93Maysville, Ark. 2003–2005 25,800 (10,900) 292 1,770 20.1 24,000 272 93(07191160) 2004–2006 24,200 (8,280) 274 1,750 19.8 22,500 255 93Spavinaw Creek near 104 2002–2004 34,500 (4,800) 332 11,600 112 22,900 220 66Cherokee, Ark. 2003–2005 38,400 (6,900) 369 9,020 86.7 29,500 284 77(07191179) 2004–2006 35,600 (3,920) 342 7,210 69.3 28,400 273 80Spavinaw Creek near 133 2002–2004 47,800 (6,110) 359 10,400 77.9 37,400 281 78Sycamore, Okla. 2003–2005 55,000 (7,920) 414 8,990 67.6 46,000 346 84(07191220) 2004–2006 45,600 (7,040) 343 6,130 46.1 39,500 297 87Spavinaw Creek near 163 2002–2004 50,700 (7,340) 311 10,200 62.5 40,500 249 80Colcord, Okla. 2003–2005 60,400 (9,610) 371 8,960 55.0 51,400 315 85(071912213) 2004–2006 55,000 (8,330) 337 8,370 51.3 46,700 287 85Beaty Creek near 59.2 2002–2004 27,000 (7,630) 456 600 10.1 26,400 446 98Jay, Okla. 2003–2005 28,300 (6,010) 478 644 10.7 27,700 468 98(07191222) 2004–2006 26,700 (6,200) 451 637 10.8 26,000 439 98

1 Calculated by S-LOADEST and are statistics of all data in the 3-year period.2 Means of the base-flow loads are calculated from base-flow days data only.3 Means of the runoff loads are calculated from runoff days data only.
26 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006

periods (table 7) from Maysville to Colcord in Spavinaw 

Creek, with the annual base-flow load at the Colcord station 

about 2 times that of Maysville station (table 7).

Estimated mean annual nitrogen runoff loads in the basin 

increased with increasing drainage area and with increasing 

streamflow during all 3-year periods (tables 1 and 7). The 

runoff component of the annual nitrogen total load for Beaty 

Creek was 85 to 89 percent (table 7). At the Spavinaw Creek 

stations, the range in the runoff component of the annual nitrogen runoff load was 60 to 71 percent and increased in the three 

downstream stations even with the drier years of 2005 and 

2006 included in the 3-year periods (tables 1 and 7). Runoff 

occurred no more than 31 percent of the time for any station 

(table 9), but accounted for most of the annual nitrogen total 

load for every station. 

Annual nitrogen runoff loads seemed to be greater in the 

2003–2005 period compared to the other two time periods at 

all stations in the basin (table 7). The most significant increase 

was between the 2002–2004 period and the 2003–2005 period, 

which coincides with the increase in mean annual streamflow 

(table 1).

Phosphorus

Estimated mean annual phosphorus total loads were 

greater at the Spavinaw Creek stations from Cherokee to 

Colcord than at Beaty Creek, primarily because of greater 

streamflow at those stations (tables 1 and 8). Annual total 

loads increased downstream during all 3-year periods 

(table 8) from Maysville to Colcord in Spavinaw Creek, with 

the annual total load at the Colcord station about 2.5 times that 

of Maysville station (table 8). 

Estimated mean annual phosphorus base-flow loads were 

substantially less in Beaty Creek than in the Spavinaw Creek 

stations during all 3-year periods (table 8). Annual base-flow 

loads at stations on Spavinaw Creek were about 2.5 to 19 

times greater than base-flow loads at the station on Beaty 

Creek. Annual phosphorus base-flow loads increased substantially downstream from Maysville to Cherokee in Spavinaw 

Creek (table 8), probably because of the inflow of discharges 

from a wastewater-treatment plant, with the annual baseflow load at the Cherokee station about 4 to 8 times that of 

Maysville station (table 8). The annual base-flow loads at the 

three downstream stations on Spavinaw Creek from Cherokee to Colcord were about the same during all 3-year periods 

(table 8).

Estimated mean annual phosphorus runoff loads in 

the basin increased with increasing drainage area and with 

increasing streamflow during all 3-year periods (tables 1 and 

8). The portion of annual phosphorus load contributed by 

runoff at the three downstream Spavinaw Creek stations generally increased downstream (Cherokee to Colcord) (table 8). 

The runoff component of the annual phosphorus total load for 

Beaty Creek was 98 percent during all 3-year periods 

(table 8). At the Spavinaw Creek stations, the range in the runoff component of the annual phosphorus total load was 66 to 

93 percent and increased in the three downstream stations even 

with the drier years of 2005 and 2006 included in the 3-year 

periods (tables 1 and 8). Almost all the phosphorus loads for 

Beaty Creek are delivered during runoff, and the annual runoff 

load for Beaty Creek was larger than runoff loads of the two 

upper Spavinaw Creek stations (table 8). Runoff occurred no 

more than 31 percent of the time for any station (table 9), but 

accounted for most of the annual phosphorus total load for 

every station during all 3-year periods.

Annual runoff loads seemed to be greater in the 

2003–2005 period compared to the other two time periods 

at all stations in the basin. The most significant increase was 

between the 2002–2004 period and the 2003–2005 period, 

which coincides with the increase in mean annual streamflow 

(table 1).

Estimated Mean Seasonal Loads

Nutrient concentrations in streams vary throughout the 

year, mainly in response to variation in precipitation and 

streamflow, and differences in time because of fertilizer or 

manure applications (U.S. Geological Survey, 1999). Nutrient concentrations in streams generally are higher during 

high streamflow during spring and summer after fertilizer 

application. High nutrient concentrations also can be in 

streams during seasonal low flows. Nitrogen and phosphorus 

concentrations in streams downstream from urban areas may 

be high during seasonal low flows, when contributions from 

point sources (such as wastewater-treatment plants) are greater 

relative to streamflow, and dilution is less (U.S. Geological 

Survey, 1999). Estimated mean seasonal nitrogen and phosphorus loads are discussed in this section and are divided into 

base-flow and runoff components (tables 10 and 11).

Nitrogen

Estimated mean seasonal nitrogen base-flow loads generally were least in autumn (September through November) 

and greatest in spring (March through May) at all stations in 

the Eucha-Spavinaw basin for 2002–2004 and 2003–2005, 

and greatest in spring and winter for 2004–2006 (table 10). 

The seasonal base-flow loads showed the same pattern as the 

annual base-flow loads (tables 7 and 10) in terms of variability among stations. Seasonal nitrogen base-flow loads were 

substantially less in Beaty Creek than in the Spavinaw Creek 

stations (table 10). Seasonal base-flow loads at stations on 

Spavinaw Creek were about 3 to 20 times greater than baseflow loads at the station on Beaty Creek. Seasonal nitrogen 

base-flow loads increased downstream from Maysville to 

Colcord in Spavinaw Creek, with the seasonal base-flow load 

at the Colcord station about 2 times that at Maysville station 

(table 10).

Estimated mean seasonal nitrogen runoff loads were 

generally least in autumn at all stations for the study period 

(table 10). Runoff loads were greatest in spring at all stations 
Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin 27

Table 9. Number of days of base flow and runoff designated by Base-Flow Index (BFI) program at water-quality stations in the Eucha-Spavinaw basin, Arkansas and Oklahoma, periods 2002–2004, 2003–2005, and 2004–2006.[Spring is March through May, Summer is June through August, Autumn is September through November, and Winter is December through February]

Station name 

(number)

3-year 

period

Seasons

Percent 

of runoff days 

in period

Spring Summer Autumn Winter Total

Base 

flow Runoff Base flow Runoff Base flow Runoff Base flow Runoff Base flow Runoff

Spavinaw Creek near 2002–2004 139 137 232 44 245 28 205 66 821 275 25Maysville, Ark. 2003–2005 174 102 221 55 245 28 207 64 847 249 23(07191160) 2004–2006 188 88 218 58 229 44 219 52 854 242 22Spavinaw Creek near 2002–2004 150 126 231 45 239 34 199 72 819 277 25Cherokee, Ark. 2003–2005 175 101 217 59 234 39 194 77 820 276 25(07191179) 2004–2006 172 104 209 67 214 59 207 64 802 294 27Spavinaw Creek near 2002–2004 143 133 228 48 236 37 188 83 795 301 27Sycamore, Okla. 2003–2005 172 104 220 56 236 37 177 94 805 291 27(07191220) 2004–2006 172 104 220 56 219 54 193 78 804 292 27Spavinaw Creek near 2002–2004 161 115 228 48 226 47 202 69 817 279 25Colcord, Okla. 2003–2005 182 94 214 62 219 54 190 81 805 291 27(071912213) 2004–2006 175 101 212 64 219 54 201 70 807 289 26Beaty Creek near 2002–2004 133 143 204 72 238 35 190 81 765 331 30Jay, Okla. 2003–2005 145 131 204 72 238 35 172 99 759 337 31(07191222) 2004–2006 166 110 225 51 250 23 181 90 822 274 25
28 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006

Table 10. Estimated mean seasonal total nitrogen base-flow and runoff loads estimated by using regression 

methods from concentrations in water-quality samples collected at water-quality stations in the Eucha-Spavinaw 

basin, Arkansas and Oklahoma, periods 2002–2004, 2003–2005, and 2004–2006.

[Values are loads in pound per season as nitrogen; Spring is March through May, Summer is June through August, Autumn is September through November, and Winter is December through February]

Flow type Station name (number) Estimated mean seasonal total nitrogen load

Spring Summer Autumn Winter

2002–2004 

Base flow Spavinaw Creek near Maysville, Ark. (07191160) 56,800 54,600 28,700 46,500

Spavinaw Creek near Cherokee, Ark. (07191179) 82,200 70,100 40,300 69,600

Spavinaw Creek near Sycamore, Okla. (07191220) 94,000 94,400 49,300 74,700

Spavinaw Creek near Colcord, Okla. (071912213) 140,000 105,000 63,000 122,000

Beaty Creek near Jay, Okla. (07191222) 16,700 8,160 3,580 10,800

Runoff Spavinaw Creek near Maysville, Ark. (07191160) 203,000 80,600 16,800 33,900

Spavinaw Creek near Cherokee, Ark. (07191179) 234,000 82,200 26,100 52,000

Spavinaw Creek near Sycamore, Okla. (07191220) 337,000 139,000 42,300 84,000

Spavinaw Creek near Colcord, Okla. (071912213) 380,000 150,000 51,400 78,100

Beaty Creek near Jay, Okla. (07191222) 120,000 52,800 22,600 22,300

2003–2005 

Base flow Spavinaw Creek near Maysville, Ark. (07191160) 68,300 41,400 26,300 66,300

Spavinaw Creek near Cherokee, Ark. (07191179) 90,300 53,700 40,500 82,800

Spavinaw Creek near Sycamore, Okla. (07191220) 106,000 75,300 44,700 85,300

Spavinaw Creek near Colcord, Okla. (071912213) 144,000 79,800 58,400 131,000

Beaty Creek near Jay, Okla. (07191222) 16,900 5,960 3,090 12,700

Runoff Spavinaw Creek near Maysville, Ark. (07191160) 149,000 80,900 16,600 104,000

Spavinaw Creek near Cherokee, Ark. (07191179) 180,000 84,900 27,300 177,000

Spavinaw Creek near Sycamore, Okla. (07191220) 256,000 135,000 43,800 250,000

Spavinaw Creek near Colcord, Okla. (071912213) 312,000 148,000 52,600 268,000

Beaty Creek near Jay, Okla. (07191222) 114,000 47,100 19,100 77,400

2004–2006 

Base flow Spavinaw Creek near Maysville, Ark. (07191160) 56,600 35,500 26,800 67,000

Spavinaw Creek near Cherokee, Ark. (07191179) 76,300 46,900 37,600 82,000

Spavinaw Creek near Sycamore, Okla. (07191220) 90,100 62,100 37,600 81,000

Spavinaw Creek near Colcord, Okla. (071912213) 117,000 68,700 58,700 126,000

Beaty Creek near Jay, Okla. (07191222) 11,900 5,850 2,980 11,800

Runoff Spavinaw Creek near Maysville, Ark. (07191160) 125,000 78,500 20,900 110,000

Spavinaw Creek near Cherokee, Ark. (07191179) 161,000 84,700 35,000 186,000

Spavinaw Creek near Sycamore, Okla. (07191220) 228,000 127,000 46,800 259,000

Spavinaw Creek near Colcord, Okla. (071912213) 282,000 143,000 53,700 289,000

Beaty Creek near Jay, Okla. (07191222) 98,300 44,400 25,100 85,000
Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin 29

Table 11. Estimated mean seasonal total phosphorus base-flow and runoff loads estimated by using regression 

methods from concentrations in water-quality samples collected at water-quality stations in the Eucha-Spavinaw 

basin, Arkansas and Oklahoma, periods 2002–2004, 2003–2005, and 2004–2006.

[Values are loads in pound per season as phosphorus; Spring is March through May, Summer is June through August, Autumn is September 

through November, and Winter is December through February]

Flow type Station name (number) Estimated mean seasonal total phosphorus load

Spring Summer Autumn Winter

2002–2004 

Base flow Spavinaw Creek near Maysville, Ark. (07191160) 404 544 257 270

Spavinaw Creek near Cherokee, Ark. (07191179) 2,930 3,230 2,480 2,960

Spavinaw Creek near Sycamore, Okla. (07191220) 2,570 3,440 2,140 2,210

Spavinaw Creek near Colcord, Okla. (071912213) 3,430 3,060 1,380 2,310

Beaty Creek near Jay, Okla. (07191222) 231 162 71.9 135

Runoff Spavinaw Creek near Maysville, Ark. (07191160) 4,690 13,400 234 270

Spavinaw Creek near Cherokee, Ark. (07191179) 10,200 9,770 904 1,980

Spavinaw Creek near Sycamore, Okla. (07191220) 13,800 20,400 1,190 2,040

Spavinaw Creek near Colcord, Okla. (071912213) 18,200 18,800 1,750 1,800

Beaty Creek near Jay, Okla. (07191222) 4,990 17,100 3,820 540

2003–2005 

Base flow Spavinaw Creek near Maysville, Ark. (07191160) 552 489 272 460

Spavinaw Creek near Cherokee, Ark. (07191179) 2,540 2,190 1,870 2,420

Spavinaw Creek near Sycamore, Okla. (07191220) 2,550 2,570 1,830 2,030

Spavinaw Creek near Colcord, Okla. (071912213) 3,120 2,240 1,270 2,330

Beaty Creek near Jay, Okla. (07191222) 251 134 75.1 184

Runoff Spavinaw Creek near Maysville, Ark. (07191160) 3,640 15,800 291 4,320

Spavinaw Creek near Cherokee, Ark. (07191179) 7,660 11,800 961 9,070

Spavinaw Creek near Sycamore, Okla. (07191220) 10,200 24,600 1,230 10,000

Spavinaw Creek near Colcord, Okla. (071912213) 14,400 22,400 1,980 12,700

Beaty Creek near Jay, Okla. (07191222) 4,420 13,500 3,220 6,530

2004–2006 

Base flow Spavinaw Creek near Maysville, Ark. (07191160) 529 380 275 564

Spavinaw Creek near Cherokee, Ark. (07191179) 2,050 1,800 1,400 1,950

Spavinaw Creek near Sycamore, Okla. (07191220) 2,010 1,690 894 1,530

Spavinaw Creek near Colcord, Okla. (071912213) 2,770 1,800 1,300 2,500

Beaty Creek near Jay, Okla. (07191222) 227 134 70.1 206

Runoff Spavinaw Creek near Maysville, Ark. (07191160) 2,950 13,600 340 5,540

Spavinaw Creek near Cherokee, Ark. (07191179) 6,600 11,900 1,180 8,690

Spavinaw Creek near Sycamore, Okla. (07191220) 9,790 17,800 1,350 10,500

Spavinaw Creek near Colcord, Okla. (071912213) 12,400 18,500 1,750 14,100

Beaty Creek near Jay, Okla. (07191222) 4,380 11,300 3,250 7,150
30 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006

in the Eucha-Spavinaw basin for 2002–2004 and 2003–2005; 

and greatest in spring and winter for 2004–2006. Estimated 

mean seasonal nitrogen runoff loads increased with increasing drainage area and with increasing streamflow showing the 

same pattern as annual runoff loads (tables 7 and 10).

Phosphorus

Estimated mean seasonal phosphorus base-flow loads 

generally were least in autumn (September through November) and greatest in spring (March through May) at all stations 

in the Eucha-Spavinaw basin during all 3-year periods 

(table 11). The seasonal base-flow loads showed the same 

pattern as the annual base-flow loads (tables 8 and 11) in 

terms of variability among stations. Seasonal phosphorus 

base-flow loads were substantially less in Beaty Creek than 

in the Spavinaw Creek stations (table 11). Seasonal base-flow 

loads at stations on Spavinaw Creek were about 2 to 30 times 

greater than base-flow loads at the station on Beaty Creek. 

Seasonal phosphorus base-flow loads increased substantially 

downstream from Maysville to Cherokee in Spavinaw Creek, 

probably because of the inflow of wastewater discharges from 

the City of Decatur, with the seasonal loads at the Cherokee 

station about 4 to 10 times that at Maysville station (table 11). 

The seasonal base-flow loads at the three downstream stations 

on Spavinaw Creek from Cherokee to Colcord were about the 

same (table 11).

Estimated mean seasonal phosphorus runoff loads generally were least in autumn (September through November); and 

greatest in summer (June through August) at all stations in the 

Eucha-Spavinaw basin during all 3-year periods (table 11). 

Estimated mean seasonal phosphorus runoff loads in the basin 

generally increased with increasing drainage area and with 

increasing streamflow at the Spavinaw Creek stations (tables 1 

and 11). Almost all the phosphorus loads at Beaty Creek were 

delivered during runoff events, and seasonal runoff loads at 

Beaty Creek generally were larger than some of the Spavinaw 

Creek stations, especially during the autumn (table 11).

Estimated Mean Annual Yields

Estimated mean annual nitrogen and phosphorus yields 

are discussed in this section. The total annual yields also are 

divided into base-flow and runoff components.

Nitrogen

Estimated mean annual nitrogen total yields generally 

increased slightly in a downstream direction for 2002–2004 in 

Spavinaw Creek; in 2003–2005 and 2004–2006 yields generally increased slightly downstream, but remained about the 

same at Sycamore and Colcord sites (table 7). The total yields 

ranged from 5,900 to 7,490 pounds per year per square mile 

(lbs/yr/mi2), with the greatest yield being reported for Spavinaw Creek near Sycamore in 2003–2005 (7,490 lbs/yr/mi2

), 

and the least yield being reported for Spavinaw Creek near 

Maysville in 2004–2006 (5,900 lbs/yr/mi2) (table 7). Beaty 

Creek near Jay had a slightly lower yield than Maysville during all 3-year periods (4,340 to 5,000 lbs/yr/mi2

).

Estimated mean annual nitrogen base-flow yields also 

generally increased slightly from the Maysville to the Cherokee station and then remained about the same in a downstream 

direction at the Spavinaw Creek stations, ranging from 2,040 

to 2,640 lbs/yr/mi2. However, the base-flow yield at Beaty 

Creek (549 to 664 lbs/yr/mi2) was substantially less than baseflow yield of the Spavinaw Creek stations, which were about 3 

to 4 times greater (table 7).

Estimated mean annual nitrogen runoff yields also generally increased slightly from the Maysville to the Cherokee 

station and then remained about the same in a downstream 

direction at the Spavinaw Creek stations, ranging from 3,790 

to 5,150 lbs/yr/mi2 and slightly less on Beaty Creek (3,680 to 

4,340 lbs/yr/mi2) (table 7). 

Phosphorus

Estimated mean annual phosphorus total yields during 

all 3-year periods in Spavinaw Creek generally increased in 

a downstream direction, ranging from 227 to 414 lbs/yr/mi2, 

with greatest yields being reported for Spavinaw Creek near 

Sycamore (359 to 414 lbs/yr/mi2), and the least yield being 

reported for Spavinaw Creek near Maysville (227 to 

292 lbs/yr/mi2) (table 8). The total yield for Beaty Creek (451 

to 478 lbs/yr/mi2), was greater than any Spavinaw Creek station. The greater yield in Beaty Creek may be caused by the 

addition of phosphorus from nonpoint sources, resuspension 

of phosphorus from the streambed, and streambank erosion.

Estimated mean annual phosphorus base-flow yield was 

substantially less in Beaty Creek (10.1 to 10.8 lbs/yr/mi2)than 

in the three downstream Spavinaw Creek stations (46.1 to 

112 lbs/yr/mi2) (table 8). Annual base-flow yields at stations 

on Spavinaw Creek were about 5 to 11 times greater than 

base-flow yields at the station on Beaty Creek. Annual phosphorus base-flow yield increased substantially downstream 

from Maysville to Cherokee in Spavinaw Creek (table 8), 

probably because of the inflow of wastewater discharges from 

the City of Decatur, with the annual base-flow yield at the 

Cherokee station about 4 to 7 times that of Maysville station 

(table 8).

Estimated mean annual phosphorus runoff yields were 

about the same at all Spavinaw Creek stations in the basin in 

all 3-year periods, ranging from 211 to 346 lbs/yr/mi2. The 

runoff yield for Beaty Creek (439 to 468 lbs/yr/mi2), was 

greater than runoff yields of any Spavinaw Creek station 

(table 8); about 98 percent of the phosphorus loads at Beaty 

Creek were delivered during runoff.
Summary 31

Estimated Mean Flow-Weighted Concentrations

Nitrogen

Estimated mean flow-weighted nitrogen concentrations 

at all stations in the basin during all 3-year periods were more 

than the median flow-weighted concentration (0.26 mg/L) 

in mostly undeveloped basins of the United States and were 

about 7 to 10 times greater than the 75th percentile of flowweighted nitrogen concentrations in those basins (0.50 mg/L, 

Clark and others, 2000) (fig. 10, table 12). 

Estimated mean flow-weighted nitrogen concentrations at 

each station in the basin during all 3-year periods were consistently greater than the median instantaneous nitrogen concentrations at each station shown in figure 10. The collected 

water-quality data have a wide range (table 4, appendixes 1-5) 

and high values during runoff events can greatly affect the 

computation of the mean flow-weighted concentrations. For 

example, the maximum concentration during 2005 at Spavinaw Creek near Colcord (9.62 mg/L, table 4, appendix 4) was 

collected during high runoff in January 2005 and contributed 

to a large nitrogen load, and similar runoffs were in April 

and July 2004 (appendix 4). Because mean flow-weighted 

concentration (mean load divided by mean streamflow times 

a conversion factor) is proportional to load, the result was a 

large estimated mean flow-weighted nitrogen concentration. 

Phosphorus

Estimated mean flow-weighted phosphorus concentrations at all stations in the basin during all 3-year periods were 

greater than the median flow-weighted concentration 

(0.022 mg/L) in mostly undeveloped basins of the United 

States and were about 4 to 10 times greater than the 75th percentile of flow-weighted phosphorus concentrations in those 

basins (0.037 mg/L, Clark and others, 2000; fig. 11, table 13). 

Estimated mean flow-weighted phosphorus concentrations at each station were consistently greater than the median 

instantaneous phosphorus concentrations shown in figure 11. 

The collected water-quality data have a wide range (table 5, 

appendixes 1-5) and high values during runoff events can 

greatly effect the computation of the mean flow-weighted concentrations. For example, the maximum concentration during 

2004 at Beaty Creek near Jay (1 mg/L, table 5, appendix 5) 

was collected during high runoff in November 2004 and contributed to a large phosphorus load. However, the highest daily 

mean streamflow and load occurred during a July 2004 event 

and was responsible for a large portion of the load during all 

3-year periods at Beaty Creek. Because mean flow-weighted 

concentration (mean load divided by mean streamflow times 

a conversion factor) is proportional to load, the result was a 

large estimated mean flow-weighted phosphorus concentration. 

Estimated Mean Annual Nutrient Loads into 

Lake Eucha

Most of the mean annual nutrient loads entering Lake 

Eucha can be estimated by adding the loads of Beaty Creek 

near Jay and the Spavinaw Creek near Colcord. Nutrient 

loads at these stations do not represent the entire nutrient load 

into Lake Eucha, but the drainage area upstream from these 

stations accounts for about 62 percent of the drainage basin 

upstream from the lake. 

Spavinaw Creek and Beaty Creek contributed a mean 

annual nitrogen total load of about 1,350,000 to 1,490,000 

pounds per year (lbs/yr) (table 14) and about 65 to 72 percent of the annual nitrogen total load was transported to Lake 

Eucha by runoff. Spavinaw Creek transported about 11 times 

more nitrogen load during base flow and about 3 times more 

nitrogen load during runoff to the lake than Beaty Creek 

(table 14).

Spavinaw Creek and Beaty Creek contributed a mean 

annual phosphorus total load of about 77,700 to 88,700 lbs/yr 

(table 14) with about 86 to 89 percent of the annual phosphorus total load being transported to Lake Eucha by runoff. Spavinaw Creek transported about 13 to 16 times more 

phosphorus load during base flow and about 1.5-2 times more 

phosphorus load during runoff to the lake than Beaty Creek 

(table 14).

Summary

The City of Tulsa, Oklahoma, uses Lake Eucha and 

Spavinaw Lake in the Eucha-Spavinaw basin in northwestern 

Arkansas and northeastern Oklahoma for public water supply. 

Consumer complaints of taste and odor in the finished water 

have been reported. The Tulsa Metropolitan Utility Authority (TMUA) has spent millions of dollars from 1998–2005 to 

eliminate taste and odor problems in the drinking water from 

the Eucha-Spavinaw system. City staff has determined that 

taste and odor problems attributable to blue-green algae have 

increased in frequency over time. Changes in the algae community in the lakes may be attributable to increases in nutrient 

levels in the lakes, and in the waters feeding the lakes. 

In July 2001, the USGS, in cooperation with the TMUA, 

supplemented fixed period, monthly water-quality sampling 

with six runoff samplings per year to better determine water 

quality over the range of streamflows in the basin. Nitrogen 

and phosphorus concentrations, loads, and yields were determined for three 3-year periods—2002–2004, 2003–2005, and 

2004–2006, to update a previous report that used data from 

water-quality samples collected during a 3-year period from 

January 2002 through December 2004.

Nitrogen and phosphorus concentrations were significantly greater in runoff samples than in base-flow samples for 

all three periods collected at Spavinaw Creek near Maysville, 

Arkansas; Spavinaw Creek near Colcord, Oklahoma, and 

Beaty Creek near Jay, Oklahoma. Runoff concentrations were 
32 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006

0

2

4

6

8

10

12

TOTAL NITROGEN CONCENTRATION, IN MILLIGRAMS PER LITER AS NITROGEN

Spavinaw Creek

near Maysville, Ark.

(07191160)

(51) (47) (36) (33)

(57)

(46)(53)

(40)

(58)

(55) (48)

(57) (55) (45)

Spavinaw Creek

near Sycamore, Okla.

(07191220)

Spavinaw Creek

near Cherokee, Ark.

(07191179)

Spavinaw Creek

near Colcord, Okla.

(071912213)

Beaty Creek

near Jay, Okla.

(07191222)

EXPLANATION

2002-2004

2003-2005

2004-2006

Estimated mean flow-weighted

nitrogen concentration (table 12)

0.50 milligram per liter

nitrogen concentration

[75th percentile of flow-weighted nitrogen

concentrations from relatively undeveloped

basins of the United States

(Clark and others, 2000)]

(54)

ALL FLOW NITROGEN

(53)

75th percentile

Median

25th percentile

Outlier

Data value less than

or equal to 1.5 times

the interquartile range

Data value greater than

or equal to 1.5 times

the interquartile range

Outlier

Number of samples

Interquartile

range

Figure 10. Instantaneous total nitrogen concentrations in water samples collected at water-quality stations in the EuchaSpavinaw basin, Arkansas and Oklahoma, periods 2002–2004, 2003–2005, and 2004–2006.
Summary 33

Table 12. Estimated mean annual total nitrogen loads, mean annual streamflows, and estimated 

mean flow-weighted total nitrogen concentrations at water-quality stations in the Eucha-Spavinaw 

basin, Arkansas and Oklahoma, periods 2002–2004, 2003–2005, and 2004–2006.

[lb/yr, pound per year; ft3/s, cubic foot per second; mg/L, milligram per liter; N, nitrogen.]

Station name 

(number)

3-year 

period

Estimated 

mean annual 

total nitrogen 

load 

(lb/yr as N)

Mean annual 

streamflow 

(ft3/s)

Estimated 

mean flow-weighted 

total nitrogen concentration 

(mg/L as N)

Spavinaw Creek near 2002–2004 521,000 61.9 4.27

Maysville, Ark. (07191160) 2003–2005 552,000 63.0 4.45

2004–2006 520,000 59.9 4.41

Spavinaw Creek near 2002–2004 656,000 74.4 4.48

Cherokee, Ark. (07191179) 2003–2005 737,000 77.8 4.81

2004–2006 709,000 74.8 4.81

Spavinaw Creek near 2002–2004 914,000 96.6 4.81

Sycamore, Okla. (07191220) 2003–2005 996,000 99.1 5.10

2004–2006 932,000 92.5 5.12

Spavinaw Creek near 2002–2004 1,090,000 127 4.37

Colcord, Okla. (071912213) 2003–2005 1,190,000 132 4.58

2004–2006 1,140,000 125 4.63

Beaty Creek near 2002–2004 257,000 38.7 3.37

Jay, Okla. (07191222) 2003–2005 296,000 44.1 3.41

2004–2006 285,000 42.4 3.41
34 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006

0.01

0.1

1

TOTAL PHOSPHORUS CONCENTRATION, IN MILLIGRAMS PER LITER AS PHOSPHORUS

Spavinaw Creek

near Maysville, Ark.

(07191160)

(50) (43) (35) (33) (57) (53) (42)

(39) (58) (55) (44) (57) (55) (43)

5

Spavinaw Creek

near Sycamore, Okla.

(07191220)

Spavinaw Creek

near Cherokee, Ark.

(07191179)

Spavinaw Creek

near Colcord, Okla.

(071912213)

Beaty Creek

near Jay, Okla.

(07191222)

EXPLANATION

2002-2004

2003-2005

2004-2006

Estimated mean flow-weighted

phosphorus concentration (table 13)

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)]

(53)

ALL FLOW PHOSPHORUS

(53)

75th percentile

Median

25th percentile

Outlier

Data value less than

or equal to 1.5 times

the interquartile range

Data value greater than

or equal to 1.5 times

the interquartile range

Outlier

Number of samples

Interquartile

range

Figure 11. Instantaneous total phosphorus concentrations in water samples collected at water-quality stations in the EuchaSpavinaw basin, Arkansas and Oklahoma, periods 2002–2004, 2003–2005, and 2004–2006.
Summary 35

Table 13. Estimated mean annual total phosphorus loads, mean annual streamflows, and estimated 

mean flow-weighted total nitrogen concentrations at water-quality stations in the Eucha-Spavinaw basin, 

Arkansas and Oklahoma, periods 2002–2004, 2003–2005, and 2004–2006.

[lb/yr, pound per year; ft3/s, cubic foot per second; mg/L, milligram per liter; P, phosphorus.]

Station name 

(number) 3-year period

Estimated mean 

annual total 

phosphorus 

load 

(lb/yr as P)

Mean annual 

streamflow 

(ft3/s)

Estimated 

mean flow-weighted 

total phosphorus 

concentration 

(mg/L as P)

Spavinaw Creek near 2002–2004 20,000 61.9 0.164

Maysville, Ark. (07191160) 2003–2005 25,800 63.0 0.208

2004–2006 24,200 59.9 0.205

Spavinaw Creek near 2002–2004 34,500 74.4 0.236

Cherokee, Ark. (07191179) 2003–2005 38,400 77.8 0.251

2004–2006 35,600 74.8 0.242

Spavinaw Creek near 2002–2004 47,800 96.6 0.251

Sycamore, Okla. (07191220) 2003–2005 55,000 99.1 0.282

2004–2006 45,600 92.5 0.250

Spavinaw Creek near 2002–2004 50,700 127 0.203

Colcord, Okla. (071912213) 2003–2005 60,400 132 0.232

2004–2006 55,000 125 0.224

Beaty Creek near 2002–2004 27,000 38.7 0.354

Jay, Okla. (07191222) 2003–2005 28,300 44.1 0.326

2004–2006 26,700 42.4 0.320
36 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006 Table 14. Summary of estimated mean annual total nitrogen and total phosphorus loads to Lake Eucha, Oklahoma, periods 2002–2004, 2003–2005, and 2004–2006. [lb/yr, pound per year; N, nitrogen; P, phosphorus] Lake Eucha Spavinaw Creek near Colcord, Okla. Beaty Creek near Jay, Okla. Lake Eucha Spavinaw Creek near Colcord, Okla. Beaty Creek near Jay, Okla. Flow type Mean annual nitrogen load 1 Component of mean annual nitrogen load (percent) Component of mean annual nitrogen load (percent) Mean annual phosphorus load 1 Component of mean annual phosphorus load (percent) Component of mean annual phosphorus load (percent) (lb/yr as N) (percent) (lb/yr as P) (percent) 2002–2004 Base Flow 2 469,000 35 92 8 10,800 14 94 6 Runoff 3 877,000 65 75 25 66,900 86 61 39 Total 4 1,350,000 100 81 19 77,700 100 65 35 2003–2005 Base Flow 2 452,000 30 91 9 9,630 11 93 7 Runoff 3 1,040,000 70 75 25 79,100 89 65 35 Total 4 1,490,000 100 80 20 88,700 100 68 32 2004–2006 Base Flow 2 402,000 28 92 8 9,010 11 93 7 Runoff 3 1,020,000 72 75 25 72,700 89 64 36 Total 4 1,420,000 100 80 20 81,700 100 67 33

1 Loads to Lake Eucha are calculated by adding loads from Spavinaw Creek near Colcord, Okla. to loads from Beaty Creek near Jay, Okla. (tables 7 and 8). These two locations account for 62 percent 

of drainage area that inflows to Lake Eucha.

2 Means of the base-flow loads are calculated from base-flow day data only by S-LOADEST and are statistics of all data in the 3-year period.3 Means of the runoff loads are calculated from runoff day data only by S-LOADEST and are statistics of all data in the 3-year period.4 Differences between total load and the sum of the base-flow load plus runoff loads are due to rounding.
Summary 37

not significantly greater than base-flow concentrations in 

samples collected at Spavinaw Creek near Cherokee, Arkansas; and Spavinaw Creek near Sycamore, Oklahoma except for 

phosphorus during 2003–2005.

Nitrogen concentrations in base-flow samples significantly increased downstream in Spavinaw Creek from the 

Maysville to Sycamore stations then significantly decreased 

from the Sycamore to the Colcord stations for all three 

periods. Nitrogen in base-flow samples collected from Beaty 

Creek was significantly less than base-flow samples from 

Spavinaw Creek. Phosphorus concentrations in base-flow 

samples significantly increased from the Maysville to Cherokee stations in Spavinaw Creek for all three periods, probably 

because of a point source between those stations, and then 

significantly decreased downstream from the Cherokee to Colcord stations. Phosphorus in base-flow samples collected from 

Beaty Creek was significantly less than phosphorus in baseflow samples collected from Spavinaw Creek downstream 

from the Maysville station during all 3-year periods.

Nitrogen concentrations in runoff samples were not 

significantly different among the stations on Spavinaw Creek 

for most of the three periods, except during 2003–2005 when 

runoff samples at the Colcord station were less than at the 

Sycamore station; however, the concentrations at Beaty Creek 

were significantly less than at all other stations. Phosphorus 

concentrations in runoff samples were not significantly different among the three downstream stations on Spavinaw; 

and were significantly different at the Maysville station on 

Spavinaw Creek and the Beaty Creek station, only during 

2004–2006. Nitrogen and phosphorus concentrations in runoff 

samples collected from all stations generally increased with 

increasing streamflow. The larger concentrations of nitrogen 

during runoff indicates addition of nitrogen from nonpoint 

sources and the larger concentrations of phosphorus during 

runoff indicates phosphorus resuspension, stream bank erosion, or addition of phosphorus from nonpoint sources.

Estimated mean annual nitrogen total loads for the three 

3-year periods were substantially greater at the Spavinaw 

Creek stations than at Beaty Creek and increased downstream 

from Maysville to Colcord in Spavinaw Creek, with the load 

at the Colcord station about 2 times that of Maysville station. Estimated mean annual nitrogen base-flow loads at the 

Spavinaw Creek stations were about 5 to 11 times greater 

than base-flow loads at Beaty Creek. The runoff component 

of the annual nitrogen total load for Beaty Creek was 85 to 89 

percent; whereas, at the Spavinaw Creek stations, the range 

in the runoff component was 60 to 71 percent. Annual runoff 

loads seemed to be greater in the 2003–2005 period compared 

to the other two time periods at all stations in the basin. The 

most significant increase was between the 2002–2004 period 

and the 2003–2005 period, which coincides with the increase 

in mean annual streamflow.

Estimated mean annual phosphorus total loads for the 

three 3-year periods were greater at the Spavinaw Creek 

stations from Cherokee to Colcord than at Beaty Creek and 

increased downstream from Maysville to Colcord in Spavinaw 

Creek, with the load at the Colcord station about 2.5 times 

that of Maysville station. Estimated mean annual phosphorus 

base-flow loads at the Spavinaw Creek stations were about 2.5 

to 19 times greater than at Beaty Creek. Phosphorus base-flow 

loads increased substantially downstream from Maysville to 

Cherokee in Spavinaw Creek, probably because of the inflow 

of discharges from a wastewater-treatment plant. Phosphorus 

base-flow loads increased about 4 to 8 times from Maysville to 

Cherokee in Spavinaw Creek; the base-flow loads were about 

the same at the three downstream stations. The runoff component of the annual phosphorus total load for Beaty Creek was 

98 percent; whereas, at the Spavinaw Creek stations, the range 

in the runoff component was 66 to 93 percent. Almost all the 

phosphorus loads at Beaty Creek are delivered during runoff, 

and the annual runoff load at Beaty Creek was larger than the 

two upper Spavinaw Creek stations. 

Estimated mean seasonal nitrogen base-flow and runoff 

loads generally were least in autumn for all three periods and 

greatest in spring at all stations in the Eucha-Spavinaw basin 

for 2002–2004 and 2003–2005 and greatest in spring and 

winter for 2004–2006. Seasonal nitrogen base-flow loads at 

stations on Spavinaw Creek were about 3 to 20 times greater 

than at the station on Beaty Creek and increased downstream 

from Maysville to Colcord in Spavinaw Creek, with the seasonal base-flow load at the Colcord station about 2 times that 

at Maysville station. Estimated mean seasonal nitrogen runoff 

loads in the basin increased with increasing drainage area and 

with increasing streamflow.

Estimated mean seasonal phosphorus base-flow and 

runoff loads generally were least in autumn and greatest in 

spring for base-flow loads and greatest in the summer for 

runoff loads during all 3-year periods at all stations in the 

Eucha-Spavinaw basin. Seasonal phosphorus base-flow loads 

at Spavinaw Creek stations were about 2 to 30 times greater 

than at the station on Beaty Creek and increased substantially 

downstream from Maysville to Cherokee in Spavinaw Creek, 

probably because of the inflow of discharges from a wastewater-treatment plant. The seasonal base-flow loads at the 

Cherokee station were about 4 to 10 times that at Maysville 

station and the seasonal base-flow loads at the three downstream stations on Spavinaw Creek from Cherokee to Colcord 

were about the same.

Estimated mean seasonal phosphorus runoff loads in the 

basin generally increased with increasing drainage area and 

with increasing streamflow at the Spavinaw Creek stations. 

Almost all the phosphorus loads at Beaty Creek are delivered 

during runoff, and several of the seasonal loads at Beaty Creek 

were generally larger than the Spavinaw Creek stations, especially during the autumn.

Estimated mean annual nitrogen total yields generally 

increased slightly in a downstream direction for 2002–2004 in 

Spavinaw Creek; in 2003–2005 and 2004–2006 yields generally increased slightly downstream, but remained about the 

same at Sycamore and Colcord sites. Estimated mean annual 

nitrogen total yields ranged from 4,340 to 7,490 pounds per 

year per square mile, with greatest yield at the Sycamore 
38 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006

station in 2003–2005, and the least yield at Beaty Creek near 

Jay for all three periods. Estimated mean annual nitrogen 

base-flow yields ranged from 549 to 2,640 pounds per year per 

square mile, and also generally increased slightly downstream 

at the Spavinaw Creek stations. However, the base-flow yield 

at Beaty Creek was substantially less than base-flow yields of 

the Spavinaw Creek stations, which were about 3 to 4 times 

greater. The estimated mean annual nitrogen runoff yields 

ranged from 3,680 to 5,150 pounds per year per square mile. 

Estimated mean annual phosphorus total yields ranged 

from 227 to 478 pounds per year per square mile, with greatest 

yield at Beaty Creek, and the least yield at Spavinaw Creek 

near Maysville. Most of the yield was delivered during runoff; 

about 98 percent of the phosphorus loads at Beaty Creek are 

delivered during runoff. The greater yield in Beaty Creek 

may be caused by the addition of phosphorus from nonpoint 

sources, resuspension of phosphorus from the streambed, and 

stream bank erosion. Estimated mean annual phosphorus baseflow yields at the three downstream Spavinaw Creek stations 

ranged from 46.1 to 112 pounds per year per square mile and 

were about 5 to 11 times greater than at Beaty Creek, probably 

because of the inflow of discharges from a wastewater-treatment plant, with the annual base-flow yield at the Cherokee 

station about 4 to 7 times that of Maysville station.

Estimated mean flow-weighted nitrogen concentrations 

at all stations in the basin for three 3-year periods were about 

7 to 10 times greater than the 75th percentile of flow-weighted 

nitrogen concentrations (0.50 milligram per liter) in mostly 

undeveloped basins of the United States. Estimated mean 

flow-weighted phosphorus concentrations at all stations in the 

basin for all three periods were about 4 to 10 times greater 

than the 75th percentile of flow-weighted phosphorus concentrations (0.037 milligram per liter) in mostly undeveloped 

basins of the United States. 

Spavinaw Creek and Beaty Creek contributed an estimated mean annual nitrogen total load of about 1,350,000 to 

1,490,000 pounds per year and about 65 to 72 percent of the 

annual nitrogen total load was transported to Lake Eucha by 

runoff. Spavinaw Creek transported about 11 times more nitrogen load during base flow and about 3 times more nitrogen 

load during runoff to the lake than Beaty Creek. Spavinaw 

Creek and Beaty Creek contributed an estimated mean annual 

phosphorus total load of about 77,700 to 88,700 pounds per 

year with about 86 to 89 percent of the annual phosphorus 

total load being transported to Lake Eucha by runoff. Spavinaw Creek transported about 13 to 16 times more phosphorus 

load during base flow and about 1.5 to 2 times more phosphorus load during runoff to the lake than Beaty Creek.

Selected References 

Adamski, J.C., Petersen, J.C., Freiwald, D.A., and Davis, J.V., 

1995, Environmental and hydrologic setting of the Ozark 

Plateaus study unit, Arkansas, Kansas, Missouri, and Oklahoma: U.S. Geological Survey Water-Resources Investigations Report 94–4022, 69 p.

Blazs, R.L., Walters, D.M., Coffey, T.E., Boyle, D.L., and 

Wellman, J.J., 2003, Water resources data, Oklahoma, water 

year 2002: U.S. Geological Survey Water-Data Report 

OK–02–1, 375 p.

Blazs, R.L., Walters, D.M., Coffey, T.E., Boyle, D.L., and 

Wellman, J.J., 2004, Water resources data, Oklahoma, water 

year 2003: U.S. Geological Survey Water-Data Report 

OK–03–1, 394 p.

Blazs, R.L., Walters, D.M., Coffey, T.E., Boyle, D.L., and 

Wellman, J.J., 2005, Water resources data, Oklahoma, water 

year 2004: U.S. Geological Survey Water-Data Report 

OK–04–1, 408 p.

Blazs, R.L., Walters, D.M., Coffey, T.E., Boyle, D.L., and 

Wellman, J.J., 2006, Water resources data, Oklahoma, water 

year 2005: U.S. Geological Survey Water-Data Report 

OK–05–1, 473 p.

Childress, C.J.O., Foreman, W.T., Connor, B.F., and Maloney, T.J., 1999, New reporting procedures based on longterm method detection levels and some considerations for 

interpretations of water-quality data provided by the U.S. 

Geological Survey National Water Quality Laboratory: 

U.S. Geological Survey Open-File Report 99–193, 19 p.

City of Tulsa City Services, 2008a, Water supply lakes—

Eucha and Spavinaw watersheds: (online only), accessed 

June 3, 2008, at http://www.cityoftulsa.org/CityServices/

Water/EuchaSpavinaw.asp

City of Tulsa City Services, 2008b, Water treatment–history: 

(online only), accessed June 3, 2008, at http://www.

cityoftulsa.org/CityServices/Water/TreatmentHistory.asp

City of Tulsa City Services, 2008c, Water treatment process: (online only), accessed June 3, 2008, at http://www.

cityoftulsa.org/CityServices/Water/TreatmentProcess.asp

Clark, G.M., Mueller, D.K., and Mast, M.A., 2000, Nutrient 

concentrations and yields in undeveloped stream basins of 

the United States: Journal of the American Water Resources 

Association, v. 36, no. 4, p. 849–860.

Cobb, E.D., and Biesecker, J.E., 1971, The National Hydrologic Benchmark Network: U.S. Geological Survey Circular 

460–D, 38 p.

Cohn, T.A., 1988, Adjusted maximum likelihood estimation of 

the moments of lognormal populations from type I censored 

samples: U.S. Geological Survey Open-File Report 88–350, 

34 p.

Cohn, T.A., 1995, Recent advances in statistical methods for 

the estimation of sediment and nutrient transport in rivers: 

Reviews of Geophysics, v. 33 (Supplement), 

p. 1,117–1,124.
Summary 39

Cohn, T.A., DeLong, L.L., Gilroy, E.J., Hirsch, R.M., and 

Wells, D.K., 1989, Estimating constituent loads: Water 

Resources Research, v. 25, no. 5, p. 937–942.

Cohn, T.A., Gilroy, E.J., and Baier, W.G., 1992, Estimating 

fluvial transport of trace constituents using a regression 

model with data subject to censoring: Proceedings of the 

Joint Statistical Meeting, Boston, August 9–13, 1992, 

p. 142–151.

Crawford, C.G., 1991, Estimation of suspended-sediment rating curves and mean suspended-sediment loads: Journal of 

Hydrology, v. 129, p. 331–348.

Daniel, T.C., Sharpley, A.N., and Lemunyon, J.L., 1998, 

Agricultural phosphorus and eutrophication—A symposium 

overview: Journal of Environmental Quality, v. 27, no. 2, 

p. 251–257.

DeLaune, P.B., Haggard, B.E., Daniel, T.C., Chaubey, Indrajeet, and Cochran, M.J. 2006, The Eucha/Spavinaw phosphorus index—A court mandated index for litter management: Journal of Soil and Water Conservation, v. 61, no. 2, 

p. 1–10.

Dempster, A.P., Laird, N.M., and Rubin, D.B., 1977, Maximum likelihood from incomplete data via the EM algorithm: Journal of the Royal Statistical Society, Series B, 

v. 39, no. 1, p. 1–38.

Edwards, T.K, and Glysson, G.D., 1999, Field methods for 

measurement of fluvial sediment: U.S. Geological Survey 

Techniques of Water-Resources Investigations, book 3, 

chap. C2, 89 p.

Fenneman, N.M., 1938, Physiography of eastern United 

States: New York, McGraw-Hill, p. 631–662.

Gilliom, R.J., Alley, W.M., and Gurtz, M.E., 1995, Design of 

the National Water-Quality Assessment program—Occurrence and distribution of water-quality conditions: U.S. 

Geological Survey Circular 1112, 33 p.

Gilliom, R.J., Hamilton, P.A., and Miller, T.L., 2001, The 

National Water-Quality Assessment program—Entering a 

new decade of investigation: U.S. Geological Survey Fact 

Sheet 071–01, 6 p.

Gilroy, E.J., Hirsch, R.M., and Cohn, T.A., 1990, Mean square 

error of regression-based constituent transport estimates: 

Water Resources Research, v. 26, no. 9, p. 2,069–2,077.

Haggard, B.E., 2000, Stream nutrient retention in the Lake 

Eucha-Spavinaw basin: Stillwater, Okla., Oklahoma State 

University, Ph.D. dissertation, 165 p.

Haggard, B.E., Storm, D.E., and Stanley, E.H., 2001, Effect of 

a point source input on stream nutrient retention: Journal of 

the American Water Resources Association, v. 37, no. 5, 

p. 1,291–1,299.

Helsel, D.R., and Hirsch, R.M., 1992, Statistical methods in 

water resources: Amsterdam, Netherlands, Elsevier, 522 p.

Insightful Corporation, 2005, S-Plus 7.0 for Windows professional developer edition with release 3.0 of the U.S. Geological Survey S-PLUS library: Seattle, Washington.

Institute of Hydrology, 1980a, Low flow studies: Wallingford, 

Oxon, United Kingdom, Report No. 1, 41 p.

Institute of Hydrology, 1980b, Low flow studies: Wallingford, 

Oxon, United Kingdom, Report No. 3, p. 12–19.

Langbein, W.B., and Iseri, K.T., 1960, General introductions 

and hydrologic definitions—Manual of Hydrology—Part 1, 

general surface-water techniques: U.S. Geological Survey 

Water-Supply Paper 1541–A, 29 p.

Likes, Jiri, 1980, Variance of the MVUE for lognormal variance: Technometrics, v. 22, no. 2, p. 253–258.

Mast, M.A., and Turk, J.T., 1999, Environmental characteristics and water quality of Hydrologic Benchmark Network 

Stations in the midwestern United States, 1963-95: 

U.S. Geological Survey Circular 1173–B, 130 p.

Oklahoma Water Resources Board, 2002, Water quality evaluation of the Eucha/Spavinaw Lake system, 528 p. 

 Petersen, J.C., Adamski, J.C., Bell, R.W., Davis, J.V., Femmer, S.R., Freiwald, D.A., and Joseph, R.L., 1998, Water 

quality in the Ozark Plateaus, Arkansas, Kansas, Missouri, 

and Oklahoma, 1992–1995: U.S. Geological Survey Circular 1158, accessed July 11, 2003, at http://water.usgs.gov/

pubs/circ/circ1158

Rantz, S.E. and others, 1982, Measurement and computation 

of streamflow—Volume 2, computation of discharge: U.S. 

Geological Survey Water-Supply Paper 2175, v. 2, 

p. 285– 631

Runkel, R.L., Crawford, C.G., and Cohn, T.A., 2004, Load 

Estimator (LOADEST)—A FORTRAN program for estimating constituent loads in streams and rivers: U.S. Geological Survey Techniques and Methods, book 4, chap. A5, 

69 p. (online only), accessed October 12, 2005, at http://

pubs.usgs.gov/tm/2005/tm4A5/

Sharpley, A.N., 1995, Fate and transport of nutrients—

Phosphorus: U.S. Department of Agriculture, Agricultural 

Research Service Working Paper No. 8, 28 p.

Storm, D.E., White, Michael, Smolen, M.D., and Zhang, 

Hailin, 2001, Modeling phosphorus loading for the Lake 

Eucha basin: Stillwater, Okla., Oklahoma State University, 

Biosystems and Agricultural Engineering Department, 14 p.
40 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006

Storm, D.E., White, M.J., and Smolen, M.D., 2002, Modeling 

the Lake Eucha basin using SWAT 2000: Stillwater, Okla., 

Oklahoma State University, Biosystems and Agricultural 

Engineering Department, 60 p.

Timme, P.J., 1995, National Water Quality Laboratory 1995 

services catalog: U.S. Geological Survey Open-File Report 

95–352, 120 p.

Tortorelli, R.L., 2006, Nutrient concentrations, loads, and 

yields in the Eucha-Spavinaw basin, Arkansas and Oklahoma, 2002–2004: U.S. Geological Survey Scientific Investigations Report 2006–5250, 44 p.

Tortorelli, R.L., and Pickup, B.E., 2006, Phosphorus concentrations, loads, and yields in the Illinois River basin, Arkansas and Oklahoma, 2000-2004: U.S. Geological Survey 

Scientific Investigations Report 2006–5175, 38 p.

Tulsa Metropolitan Utility Authority, 2001, Eucha/Spavinaw 

watershed project: (online only), accessed August 10, 2006, 

at http:www.tulsawater.com/eucha.html

U.S. Environmental Protection Agency, 1983, Methods for 

chemical analysis of water and wastes, Method 365.2 (2nd 

ed.): EPA–600/4–79–20 Revised March 1983 [variously 

paged]

U.S. Environmental Protection Agency, 1993, Methods for 

the determination of inorganic substances in environmental 

samples: EPA–600/R–93–100 [variously paged]

U.S. Environmental Protection Agency, 1997, Guidelines 

establishing test procedures for the analysis of pollutants 

[App. B, Part 136, Definition and procedures for the determination of the method detection limit]: U.S. Code of Federal Regulations, Title 40, revised July 1, 1997, p. 265–267.

U.S. Geological Survey, 1999, The quality of our nation’s 

waters—Nutrients and Pesticides: U.S. Geological Survey 

Circular 1225, 82 p.

U.S. Geological Survey, 2006, National field manual for 

the collection of water-quality data, collection of water 

samples: U.S. Geological Survey Techniques of WaterResources Investigations, book 9, chap. A4, 166 p., 

accessed September 25, 2008, at http://water.usgs.gov/owq/

FieldManual/chapter4/pdf/Chap4_v2.pdf

U.S. Geological Survey, 2007, Water-resources data for the 

United States, Water Year 2006: (online only), accessed 

January 9, 2008, at http://wdr.water.usgs.gov/wy2006/

search.jsp

U.S. Geological Survey, 2008, Water-resources data for the 

United States, Water Year 2007: (online only), accessed 

April 10, 2008, at http://wdr.water.usgs.gov/wy2007/search.

jsp

Wagner, Kevin, and Woodruff, Scott, 1997, Phase I clean lakes 

project, diagnostic and feasibility study of Lake Eucha: 

Oklahoma Conservation Commission, Final Report.

Wahl, K.L., and Tortorelli, R.L., 1997, Changes in flow in the 

Beaver-North Canadian River basin upstream from Canton 

Lake, western Oklahoma: U.S. Geological Survey WaterResources Investigations Report 96–4304, 58 p.

Wahl, K.L., and Wahl, T.L., 1995, Determining the flow of 

Comal Springs at New Braunfels, Texas, in Proceedings 

of Texas water, ‘95, A Component Conference of the First 

International Conference on Water Resources Engineering, American Society of Civil Engineers Symposium, San 

Antonio, Texas, August 16–17, 1995: American Society of 

Civil Engineers, p. 77–86.

Wolynetz, M.S., 1979, Algorithm 139–Maximum likelihood 

estimation in a linear model with confined and censored 

data: Applied Statistics, v. 28, p. 195–206.
Appendixes 41

Appendixes
42 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006
Appendixes 43

Appendix 1. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Maysville, 

Arkansas, 2002-2006. —Continued

[COT, City of Tulsa; USGS, U.S. Geological Survey; ft3/s, cubic foot per second; mg/L, milligram per liter; N, nitrogen; P, phosphorus; --, not 

reported; all water-quality and streamflow data available at http://water.usgs.gov/ok/nwis]

Date Sample time

Agency 

collecting 

sample

Streamflow 1

(ft3/s)

Total nitrogen

concentration

(mg/L as N) 2

Total phosphorus

concentration

(mg/L as P)

Flow

category 3

01/15/2002 0820 COT 35 4.80 0.028 Base flow

02/01/2002 1010 USGS 305 3.40 0.045 Runoff

02/12/2002 0815 COT 55 4.80 0.024 Base flow

03/12/2002 0845 COT 61 4.20 0.024 Base flow

03/20/2002 1445 USGS 221 4.00 0.028 Runoff

04/08/2002 1205 USGS 648 3.97 0.160 Runoff

04/18/2002 0817 COT 82 4.20 0.028 Base flow

05/13/2002 1320 USGS 176 3.44 0.033 Runoff

05/17/2002 1300 USGS 1,560 7.40 0.500 Runoff

05/23/2002 0808 COT 136 4.54 0.042 Runoff

06/13/2002 0838 COT 88 3.68 0.035 Runoff

07/18/2002 0832 COT 34 3.41 0.025 Base flow

08/13/2002 0820 COT 24 3.20 0.031 Base flow

09/19/2002 0810 COT 19 2.85 0.033 Base flow

10/16/2002 0735 COT 16 2.80 0.025 Base flow

11/12/2002 0753 COT 18 2.85 0.030 Base flow

12/12/2002 0818 COT 17 2.90 0.022 Base flow

 

01/07/2003 0845 COT 25 3.36 0.024 Base flow

02/06/2003 0817 COT 18 3.15 0.022 Base flow

03/05/2003 0818 COT 62 4.43 0.025 Runoff

04/09/2003 0822 COT 38 3.76 0.019 Base flow

05/08/2003 0825 COT 29 3.10 0.019 Base flow

05/16/2003 1100 USGS 92 3.63 0.220 Runoff

05/20/2003 1102 USGS 153 3.70 0.061 Runoff

05/21/2003 1115 USGS 251 4.16 0.039 Runoff

06/02/2003 1258 USGS 49 4.20 0.042 Runoff

06/03/2003 0830 COT 48 3.85 -- Runoff

06/12/2003 1102 USGS 48 3.82 0.200 Runoff

07/10/2003 0800 COT 21 3.33 0.023 Base flow

07/14/2003 1235 USGS 69 3.01 0.040 Runoff

08/05/2003 0800 COT 15 2.97 0.030 Base flow

09/11/2003 0759 COT 14 2.70 0.026 Base flow

10/09/2003 0755 COT 14 2.57 0.041 Base flow

11/06/2003 0755 COT 13 2.60 0.022 Base flow

11/19/2003 1111 USGS 33 3.06 0.029 Runoff
44 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006

Appendix 1. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Maysville, 

Arkansas, 2002-2006. —Continued

[COT, City of Tulsa; USGS, U.S. Geological Survey; ft3/s, cubic foot per second; mg/L, milligram per liter; N, nitrogen; P, phosphorus; --, not 

reported; all water-quality and streamflow data available at http://water.usgs.gov/ok/nwis]

Date Sample time

Agency 

collecting 

sample

Streamflow 1

(ft3/s)

Total nitrogen

concentration

(mg/L as N) 2

Total phosphorus

concentration

(mg/L as P)

Flow

category 3

12/10/2003 0820 COT 21 3.53 0.019 Base flow

01/06/2004 0840 COT 59 4.28 0.017 Runoff

02/05/2004 0815 COT 38 4.55 0.019 Base flow

03/04/2004 0825 COT 890 5.57 0.291 Runoff

03/04/2004 1125 USGS 809 5.79 0.140 Runoff

03/29/2004 1110 USGS 307 4.40 0.054 Runoff

04/07/2004 0845 COT 72 4.86 0.024 Base flow

04/23/2004 1040 USGS 419 3.43 0.046 Runoff

04/24/2004 1435 USGS 2,110 5.68 0.800 Runoff

05/06/2004 0817 COT 160 4.87 0.032 Runoff

06/10/2004 0815 COT 43 3.82 0.041 Base flow

07/03/2004 1100 USGS 3,970 5.61 0.920 Runoff

07/08/2004 0830 COT 170 4.61 0.022 Runoff

08/05/2004 0825 COT 64 3.91 0.040 Base flow

09/09/2004 0830 COT 29 3.59 0.028 Base flow

10/07/2004 0806 COT 22 3.37 0.028 Base flow

11/01/2004 1200 USGS 654 4.02 0.240 Runoff

11/03/2004 0848 COT 156 4.67 0.050 Runoff

12/09/2004 0840 COT 151 5.18 0.025 Runoff

01/05/2005 1215 USGS 3,190 9.34 1.200 Runoff

01/06/2005 0858 COT 855 5.57 0.170 Runoff

02/10/2005 0832 COT 84 4.80 0.025 Base flow

03/10/2005 0837 COT 72 4.36 0.029 Base flow

04/07/2005 0845 COT 167 3.88 0.059 Runoff

05/12/2005 0825 COT 41 3.87 0.028 Base flow

06/09/2005 0902 COT 33 3.53 0.031 Base flow

06/14/2005 1145 USGS 78 3.50 0.150 Runoff

07/14/2005 0827 COT 22 2.90 0.034 Base flow

08/11/2005 0757 COT 19 2.82 0.027 Base flow

09/15/2005 0835 COT 15 2.70 0.059 Base flow

10/06/2005 0815 COT 13 2.75 0.042 Base flow

11/16/2005 0752 COT 16 2.73 0.031 Base flow

12/15/2005 0812 COT 14 2.82 0.022 Base flow
Appendixes 45

Appendix 1. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Maysville, 

Arkansas, 2002-2006. —Continued

[COT, City of Tulsa; USGS, U.S. Geological Survey; ft3/s, cubic foot per second; mg/L, milligram per liter; N, nitrogen; P, phosphorus; --, not 

reported; all water-quality and streamflow data available at http://water.usgs.gov/ok/nwis]

Date Sample time

Agency 

collecting 

sample

Streamflow 1

(ft3/s)

Total nitrogen

concentration

(mg/L as N) 2

Total phosphorus

concentration

(mg/L as P)

Flow

category 3

01/12/2006 0812 COT 16 2.82 0.120 Base flow

02/09/2006 0823 COT 14 2.73 0.027 Base flow

03/09/2006 0805 COT 14 2.60 0.019 Base flow

04/12/2006 0802 COT 18 2.66 -- Base flow

04/29/2006 1330 USGS 29 2.37 0.032 Runoff

05/02/2006 1335 USGS 84 3.22 0.031 Runoff

05/10/2006 0830 COT 63 0.69 0.046 Runoff

05/10/2006 1135 USGS 61 3.15 0.041 Runoff

06/08/2006 0837 COT 28 -- 0.028 Runoff

07/13/2006 0856 COT 9.8 -- 0.038 Base flow

07/13/2006 1100 USGS 9.8 2.37 0.031 Base flow

08/10/2006 0755 COT 6 1.98 -- Base flow

08/28/2006 1135 USGS 61 2.29 0.055 Runoff

09/14/2006 0837 COT 12 2.71 -- Base flow

10/12/2006 0837 COT 11 2.85 -- Base flow

11/16/2006 0730 COT 16 2.39 -- Base flow

12/06/2006 0847 COT 70 5.00 -- Runoff

1

 Streamflow for data collected by USGS is measured instantaneous streamflow; streamflow for data collected by COT is daily mean 

streamflow unless streamflow changing rapidly during the day, then it is 15-minute unit value.

2

 Total nitrogen is calculated by adding Kjeldahl-N and nitrite plus nitrate analyses.

3

 Base flow and runoff designated by Base-Flow Index (BFI) program (Institute of Hydrology, 1980a, 1980b). 
46 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006

Appendix 2. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near 

Cherokee, Arkansas, 2002–2006.—Continued

[COT, City of Tulsa; USGS, U.S. Geological Survey; ft3/s, cubic foot per second; mg/L, milligram per liter; N, nitrogen; P, phosphorus; 

--, not reported; all water-quality and streamflow data available at http://water.usgs.gov/ok/nwis]

Date Sample 

time

Agency 

collecting 

sample

Streamflow 1

(ft3/s)

Total nitrogen

concentration

(mg/L as N) 2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category 3

01/15/2002 0835 COT 41 5.40 0.233 Base flow

02/01/2002 1236 USGS 290 3.60 0.170 Runoff

02/12/2002 0835 COT 71 5.20 0.230 Base flow

03/12/2002 0900 COT 82 4.40 0.227 Base flow

03/20/2002 1641 USGS 233 4.83 0.170 Runoff

04/08/2002 1410 USGS 700 4.26 0.190 Runoff

04/18/2002 0835 COT 101 4.60 0.204 Base flow

05/13/2002 1510 USGS 190 3.28 0.170 Runoff

05/17/2002 1630 USGS 1,590 6.82 0.380 Runoff

05/23/2002 0823 COT 150 4.40 0.170 Runoff

06/13/2002 0850 COT 107 3.92 0.186 Runoff

07/18/2002 0847 COT 42 3.59 0.234 Base flow

08/13/2002 0835 COT 26 3.33 0.234 Base flow

09/19/2002 0825 COT 25 3.16 0.301 Base flow

10/16/2002 0755 COT 17 3.11 0.315 Base flow

11/12/2002 0808 COT 24 3.49 0.312 Base flow

12/12/2002 0833 COT 19 3.54 0.299 Base flow

 

01/07/2003 0900 COT 33 4.11 0.279 Runoff

02/06/2003 0834 COT 20 4.13 0.257 Base flow

03/05/2003 0900 COT 67 4.94 0.194 Runoff

04/09/2003 0836 COT 54 4.22 0.177 Base flow

05/08/2003 0840 COT 32 3.28 0.227 Base flow

05/14/2003 0800 COT 31 4 4.44 0.223 Base flow

05/16/2003 0945 COT 134 3.05 0.500 Runoff

05/16/2003 1211 USGS 134 3.21 0.030 Runoff

05/20/2003 1258 USGS 165 4.00 0.250 Runoff

05/21/2003 1247 USGS 310 4.34 0.130 Runoff

06/02/2003 1405 USGS 54 2.48 0.190 Runoff

06/03/2003 0850 COT 52 4.27 0.142 Runoff

06/11/2003 0910 COT 38 4.10 0.194 Base flow

06/12/2003 1218 USGS 49 4.20 0.034 Runoff

07/10/2003 0815 COT 19 3.64 0.199 Base flow

07/14/2003 1054 USGS 61 3.46 0.170 Runoff

08/05/2003 0820 COT 14 3.45 0.209 Base flow

09/11/2003 0826 COT 16 3.51 0.211 Base flow
Appendixes 47

Appendix 2. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near 

Cherokee, Arkansas, 2002–2006.—Continued

[COT, City of Tulsa; USGS, U.S. Geological Survey; ft3/s, cubic foot per second; mg/L, milligram per liter; N, nitrogen; P, phosphorus; 

--, not reported; all water-quality and streamflow data available at http://water.usgs.gov/ok/nwis]

Date Sample 

time

Agency 

collecting 

sample

Streamflow 1

(ft3/s)

Total nitrogen

concentration

(mg/L as N) 2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category 3

10/09/2003 0815 COT 21 3.66 0.223 Base flow

11/06/2003 0811 COT 19 3.90 0.229 Base flow

11/19/2003 1236 USGS 41 4.22 0.230 Runoff

12/10/2003 0845 COT 29 4.21 0.182 Runoff

01/06/2004 0855 COT 79 4.99 0.146 Runoff

02/05/2004 0835 COT 49 5.46 0.140 Base flow

03/04/2004 0840 COT 1,100 5.73 0.336 Runoff

03/04/2004 1510 USGS 912 6.28 0.180 Runoff

03/29/2004 1235 USGS 375 4.52 0.100 Runoff

04/07/2004 0900 COT 80 5.12 0.114 Base flow

04/23/2004 1259 USGS 470 3.87 0.082 Runoff

04/24/2004 1735 USGS 2,210 4.99 0.640 Runoff

05/06/2004 0837 COT 207 5.22 0.110 Runoff

06/10/2004 0830 COT 57 4.21 0.143 Base flow

07/03/2004 0926 USGS 8,000 2.68 1.300 Runoff

07/08/2004 0845 COT 207 5.04 0.126 Runoff

08/05/2004 0840 COT 86 4.48 0.189 Base flow

09/09/2004 0845 COT 33 4.20 0.144 Base flow

10/07/2004 0820 COT 24 4.30 0.157 Base flow

11/01/2004 1400 USGS 657 4.66 0.240 Runoff

11/03/2004 0905 COT 199 5.20 0.152 Runoff

12/09/2004 0855 COT 184 5.58 0.110 Runoff

01/05/2005 1325 USGS 3,780 10.45 1.200 Runoff

01/06/2005 0915 COT 1,440 6.13 0.230 Runoff

02/10/2005 0848 COT 97 5.30 0.081 Base flow

03/10/2005 0852 COT 83 4.89 0.088 Base flow

04/07/2005 0900 COT 219 4.18 0.190 Runoff

05/12/2005 0840 COT 37 4.13 0.150 Base flow

06/09/2005 0919 COT 35 3.81 0.110 Base flow

06/14/2005 1440 USGS 105 3.34 0.140 Runoff

07/14/2005 0844 COT 24 3.28 0.170 Base flow

08/11/2005 0815 COT 22 3.99 0.160 Base flow

10/06/2005 0825 COT 16 3.55 0.160 Base flow

11/16/2005 0815 COT 25 4.04 0.150 Base flow

12/15/2005 0828 COT 14 3.69 0.120 Base flow
48 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006

Appendix 2. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near 

Cherokee, Arkansas, 2002–2006.—Continued

[COT, City of Tulsa; USGS, U.S. Geological Survey; ft3/s, cubic foot per second; mg/L, milligram per liter; N, nitrogen; P, phosphorus; 

--, not reported; all water-quality and streamflow data available at http://water.usgs.gov/ok/nwis]

Date Sample 

time

Agency 

collecting 

sample

Streamflow 1

(ft3/s)

Total nitrogen

concentration

(mg/L as N) 2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category 3

01/12/2006 0825 COT 18 4.37 0.140 Base flow

02/09/2006 0840 COT 16 3.98 0.160 Base flow

03/09/2006 0820 COT 19 3.71 0.120 Base flow

04/12/2006 0818 COT 26 2.96 -- Runoff

04/29/2006 1645 USGS 46 3.15 0.150 Runoff

05/02/2006 1455 USGS 103 3.51 0.130 Runoff

05/10/2006 0845 COT 112 3.37 0.140 Runoff

05/10/2006 1245 USGS 101 3.67 0.130 Runoff

06/08/2006 0853 COT 29 -- 0.150 Runoff

07/13/2006 0920 COT 13 -- 0.150 Base flow

07/13/2006 1245 USGS 13 2.97 0.130 Base flow

08/10/2006 0810 COT 10 2.56 -- Base flow

08/28/2006 1315 USGS 77 4.28 0.190 Runoff

09/14/2006 0855 COT 16 3.72 -- Base flow

10/12/2006 0857 COT 15 3.68 -- Base flow

11/16/2006 0745 COT 26 3.34 -- Runoff

12/06/2006 0905 COT 80 5.57 -- Runoff

1

 Streamflow for data collected by USGS is measured instantaneous streamflow; streamflow for data collected by COT is daily 

mean streamflow unless streamflow changing rapidly during the day, then it is 15-minute unit value.

2

 Total nitrogen is calculated by adding Kjeldahl-N and nitrite plus nitrate analyses.

3

 Base flow and runoff designated by Base-Flow Index (BFI) program (Institute of Hydrology, 1980a, 1980b). 

4

 Nitrite plus nitrate analyses not reported, nitrate analyses was substituted in the total nitrogen calculation for this sample.
Appendixes 49

Appendix 3. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Sycamore, 

Oklahoma, 2002–2006. —Continued

[COT, City of Tulsa; USGS, U.S. Geological Survey; ft3/s, cubic foot per second; mg/L, milligram per liter; N, nitrogen; P, phosphorus; --, not 

reported; all water-quality and streamflow data available at http://water.usgs.gov/ok/nwis]

Date Sample 

time

Agency 

collecting 

sample

Streamflow 1

(ft3/s)

Total nitrogen

concentration

(mg/L as N) 2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category 3

01/15/2002 0755 COT 54 5.50 0.144 Base flow

02/01/2002 1506 USGS 384 3.20 0.160 Runoff

02/12/2002 0750 COT 92 5.30 0.147 Base flow

03/12/2002 0815 COT 105 4.50 0.153 Base flow

03/21/2002 1123 USGS 268 4.40 0.140 Runoff

04/08/2002 1708 USGS 952 5.06 0.180 Runoff

04/18/2002 0817 COT 131 4.70 0.149 Base flow

05/13/2002 1205 USGS 203 3.84 0.170 Runoff

05/17/2002 1428 USGS 885 7.10 0.310 Runoff

05/23/2002 0740 COT 174 4.30 0.153 Runoff

06/13/2002 0803 COT 135 3.96 0.146 Base flow

07/18/2002 0800 COT 46 3.65 0.143 Base flow

 

01/07/2003 0818 COT 44 4.07 0.163 Runoff

03/05/2003 0700 COT 110 4.97 0.138 Runoff

04/09/2003 0757 COT 57 4.02 0.140 Base flow

05/16/2003 1335 USGS 151 3.68 0.190 Runoff

05/20/2003 1705 USGS 242 4.10 0.270 Runoff

05/21/2003 1437 USGS 345 4.29 0.130 Runoff

06/02/2003 1519 USGS 68 3.87 0.130 Runoff

06/03/2003 0800 COT 71 4.25 -- Runoff

06/16/2003 1312 USGS 72 3.99 0.130 Runoff

09/02/2003 1220 COT 31 3.58 0.170 Runoff

01/06/2004 0815 COT 93 5.38 0.117 Runoff

01/18/2004 1540 USGS 137 5.70 0.120 Runoff

02/05/2004 0740 COT 56 5.36 0.110 Base flow

03/04/2004 0754 COT 1,500 6.15 0.461 Runoff

03/04/2004 1135 USGS 1,310 6.44 0.190 Runoff

03/29/2004 1430 USGS 462 4.82 0.100 Runoff

04/07/2004 0817 COT 100 5.22 0.092 Base flow
50 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006

Appendix 3. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Sycamore, 

Oklahoma, 2002–2006. —Continued

[COT, City of Tulsa; USGS, U.S. Geological Survey; ft3/s, cubic foot per second; mg/L, milligram per liter; N, nitrogen; P, phosphorus; --, not 

reported; all water-quality and streamflow data available at http://water.usgs.gov/ok/nwis]

Date Sample 

time

Agency 

collecting 

sample

Streamflow 1

(ft3/s)

Total nitrogen

concentration

(mg/L as N) 2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category 3

04/23/2004 1445 USGS 561 3.54 0.120 Runoff

04/24/2004 1445 USGS 3,120 5.97 0.970 Runoff

05/06/2004 0750 COT 291 5.17 0.104 Runoff

06/10/2004 0750 COT 62 4.24 0.129 Base flow

07/03/2004 1327 USGS 4,810 5.48 0.980 Runoff

07/08/2004 0800 COT 323 5.05 0.116 Runoff

08/05/2004 0755 COT 148 4.39 0.120 Base flow

09/09/2004 0800 COT 50 4.21 0.117 Base flow

11/01/2004 1600 USGS 1,010 4.95 0.240 Runoff

11/03/2004 0818 COT 343 5.21 0.145 Runoff

12/09/2004 0812 COT 309 5.58 0.088 Runoff

01/05/2005 1440 USGS 3,860 9.31 1.200 Runoff

01/06/2005 0827 COT 1,690 5.89 0.250 Runoff

02/10/2005 0805 COT 117 5.45 0.081 Base flow

03/10/2005 0811 COT 100 4.88 0.110 Base flow

04/07/2005 0815 COT 292 4.87 0.090 Runoff

05/12/2005 0755 COT 51 4.29 0.140 Base flow

06/09/2005 0836 COT 41 3.92 0.095 Base flow

06/15/2005 1115 USGS 89 3.85 0.110 Runoff

04/29/2006 1845 USGS 27 3.15 0.110 Runoff

05/02/2006 1515 USGS 109 3.83 0.083 Runoff

05/10/2006 0803 COT 101 3.86 0.130 Runoff

05/10/2006 1330 USGS 150 3.52 0.130 Runoff

07/13/2006 0825 COT 5.8 -- 0.120 Base flow

07/13/2006 0900 USGS 5.8 3.18 0.100 Base flow

08/28/2006 1145 USGS 18 3.03 0.120 Runoff

12/06/2006 0814 COT 104 5.60 -- Runoff

1

 Streamflow for data collected by USGS is measured instantaneous streamflow; streamflow for data collected by COT is daily mean 

streamflow unless streamflow changing rapidly during the day, then it is 30-minute unit value.

2

 Total nitrogen is calculated by adding Kjeldahl-N and nitrite plus nitrate analyses.

3

 Base flow and runoff designated by Base-Flow Index (BFI) program (Institute of Hydrology, 1980a, 1980b). 
Appendixes 51

Appendix 4. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Colcord, 

Oklahoma, 2002–2006.—Continued

[COT, City of Tulsa; USGS, U.S. Geological Survey; ft3/s, cubic foot per second; mg/L, milligram per liter; N, nitrogen; P, phosphorus; --, not 

reported; all water-quality and streamflow data available at http://water.usgs.gov/ok/nwis]

Date Sample 

time

Agency 

collecting 

sample

Streamflow 1

(ft3/s)

Total nitrogen

concentration

(mg/L as N) 2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category 3

01/15/2002 0905 COT 73 5.20 0.105 Base flow

02/01/2002 1706 USGS 388 3.90 0.140 Runoff

02/12/2002 0900 COT 113 5.00 0.108 Base flow

03/12/2002 0927 COT 132 4.10 0.111 Base flow

03/21/2002 1445 USGS 349 4.10 0.120 Runoff

04/09/2002 1026 USGS 769 4.10 0.130 Runoff

04/18/2002 0902 COT 176 4.40 0.130 Base flow

05/13/2002 1342 USGS 269 3.51 0.130 Runoff

05/17/2002 1850 USGS 1,670 6.29 0.390 Runoff

05/23/2002 0852 COT 210 4.00 0.122 Base flow

06/13/2002 0917 COT 168 3.62 0.121 Base flow

07/18/2002 0914 COT 58 3.42 0.104 Base flow

08/13/2002 0902 COT 36 3.22 0.101 Base flow

09/19/2002 0805 COT 22 2.82 0.100 Base flow

10/16/2002 0820 COT 21 2.91 0.087 Base flow

11/12/2002 0837 COT 33 3.18 0.092 Base flow

12/12/2002 0900 COT 34 3.21 0.095 Base flow

 

01/07/2003 0925 COT 59 3.80 0.108 Runoff

02/06/2003 0900 COT 30 3.67 0.089 Base flow

03/05/2003 0930 COT 113 4.39 0.101 Base flow

04/09/2003 0902 COT 61 3.86 0.104 Base flow

05/08/2003 0907 COT 48 3.23 0.102 Base flow

05/14/2003 0830 COT 61 4 5.27 0.132 Runoff

05/16/2003 1010 COT 467 2.89 0.980 Runoff

05/16/2003 1504 USGS 446 3.86 0.180 Runoff

05/20/2003 1435 USGS 349 2.30 0.280 Runoff

05/21/2003 1607 USGS 446 4.81 0.110 Runoff

06/02/2003 1639 USGS 113 4.22 0.120 Runoff

06/03/2003 0920 COT 102 3.76 0.149 Runoff

06/11/2003 0945 COT 57 3.78 0.115 Base flow

06/16/2003 1452 USGS 80 3.69 0.110 Runoff

07/10/2003 0841 COT 27 3.23 0.087 Base flow

08/05/2003 0845 COT 24 3.01 0.090 Base flow

09/02/2003 1418 USGS 88 3.13 0.120 Runoff

09/11/2003 0901 COT 44 3.19 0.085 Runoff
52 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006

Appendix 4. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Colcord, 

Oklahoma, 2002–2006.—Continued

[COT, City of Tulsa; USGS, U.S. Geological Survey; ft3/s, cubic foot per second; mg/L, milligram per liter; N, nitrogen; P, phosphorus; --, not 

reported; all water-quality and streamflow data available at http://water.usgs.gov/ok/nwis]

Date Sample 

time

Agency 

collecting 

sample

Streamflow 1

(ft3/s)

Total nitrogen

concentration

(mg/L as N) 2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category 3

10/09/2003 0840 COT 23 3.00 0.089 Base flow

11/06/2003 0840 COT 23 3.20 0.086 Base flow

11/19/2003 1545 USGS 80 3.80 0.088 Runoff

12/10/2003 0925 COT 34 3.77 0.084 Base flow

01/06/2004 0922 COT 138 4.59 0.123 Runoff

01/18/2004 1350 USGS 270 4.50 0.099 Runoff

02/05/2004 0850 COT 95 5.05 0.087 Base flow

03/04/2004 0909 COT 2,390 5.70 0.550 Runoff

03/04/2004 0945 USGS 2,320 6.23 0.280 Runoff

03/29/2004 1600 USGS 646 4.94 0.099 Runoff

04/07/2004 0931 COT 150 4.74 0.084 Base flow

04/23/2004 1315 USGS 792 3.32 0.100 Runoff

04/24/2004 1235 USGS 4,130 6.08 0.990 Runoff

05/06/2004 0904 COT 337 4.62 0.093 Runoff

06/10/2004 0900 COT 74 4.37 0.085 Base flow

07/03/2004 1405 USGS 7,200 3.54 0.940 Runoff

07/08/2004 0910 COT 424 4.51 0.092 Runoff

08/05/2004 0910 COT 172 3.98 0.147 Base flow

09/09/2004 0910 COT 69 4.04 0.114 Base flow

10/07/2004 0845 COT 34 3.81 0.081 Base flow

11/01/2004 1730 USGS 1,280 4.68 0.190 Runoff

11/03/2004 0935 COT 397 4.70 0.131 Runoff

12/09/2004 0927 COT 374 5.03 0.075 Runoff

01/05/2005 1430 USGS 5,700 9.62 1.100 Runoff

01/06/2005 0945 COT 2,190 5.54 0.230 Runoff

02/10/2005 0917 COT 155 5.18 0.081 Base flow

03/10/2005 0920 COT 129 4.59 0.082 Base flow

04/07/2005 0928 COT 296 3.90 0.093 Runoff

05/12/2005 0907 COT 84 4.07 0.110 Base flow

06/09/2005 0950 COT 47 3.64 0.075 Base flow

06/15/2005 1350 USGS 90 3.63 0.150 Runoff

07/14/2005 0915 COT 34 2.90 0.087 Base flow

08/11/2005 0850 COT 30 3.02 0.081 Base flow

09/15/2005 0925 COT 21 2.90 0.066 Base flow

10/06/2005 0900 COT 19 3.06 0.078 Base flow
Appendixes 53

Appendix 4. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Colcord, 

Oklahoma, 2002–2006.—Continued

[COT, City of Tulsa; USGS, U.S. Geological Survey; ft3/s, cubic foot per second; mg/L, milligram per liter; N, nitrogen; P, phosphorus; --, not 

reported; all water-quality and streamflow data available at http://water.usgs.gov/ok/nwis]

Date Sample 

time

Agency 

collecting 

sample

Streamflow 1

(ft3/s)

Total nitrogen

concentration

(mg/L as N) 2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category 3

11/16/2005 0845 COT 27 3.46 0.071 Base flow

12/15/2005 0857 COT 21 3.55 0.065 Base flow

01/12/2006 0855 COT 21 3.64 0.260 Base flow

02/09/2006 0913 COT 22 3.61 0.083 Base flow

03/09/2006 0850 COT 30 3.32 0.069 Base flow

04/12/2006 0850 COT 34 2.94 -- Runoff

04/29/2006 1355 USGS 68 2.67 0.097 Runoff

05/02/2006 1410 USGS 153 3.41 0.092 Runoff

05/10/2006 0917 COT 142 3.18 0.098 Runoff

05/10/2006 1150 USGS 191 3.41 0.130 Runoff

06/08/2006 0925 COT 39 -- 0.100 Runoff

07/13/2006 0947 COT 13 -- 0.074 Base flow

07/13/2006 1300 USGS 12 2.47 0.065 Base flow

08/10/2006 0842 COT 11 2.28 -- Base flow

08/28/2006 1345 USGS 30 2.08 0.074 Runoff

09/14/2006 0927 COT 29 3.01 -- Base flow

10/12/2006 0926 COT 15 3.07 -- Base flow

11/16/2006 0815 COT 24 2.94 -- Base flow

12/06/2006 0940 COT 132 5.03 -- Runoff

1

 Streamflow for data collected by USGS is measured instantaneous streamflow; streamflow for data collected by COT is daily mean 

streamflow unless streamflow changing rapidly during the day, then it is 15-minute unit value.

2

 Total nitrogen is calculated by adding Kjeldahl-N and nitrite plus nitrate analyses.

3

 Base flow and runoff designated by Base-Flow Index (BFI) program (Institute of Hydrology, 1980a, 1980b). 

4

 Nitrite plus nitrate analyses not reported, nitrate analyses was substituted in the total nitrogen calculation for this sample.
54 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006

Appendix 5. Streamflows, and total nitrogen and total phosphorus concentrations for Beaty Creek near Jay, Oklahoma, 

2002–2006. —Continued

[COT, City of Tulsa; USGS, U.S. Geological Survey; ft3/s, cubic foot per second; mg/L, milligram per liter; N, nitrogen; P, phosphorus; --, not 

reported; all water-quality and streamflow data available at http://water.usgs.gov/ok/nwis]

Date Sample 

time

Agency 

collecting 

sample

Streamflow 1

(ft3/s)

Total nitrogen

concentration

(mg/L as N) 2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category 3

01/15/2002 0940 COT 9.6 3.20 0.043 Base flow

02/01/2002 1911 USGS 99 2.60 0.049 Runoff

02/12/2002 0755 COT 25 3.20 0.033 Runoff

03/12/2002 0750 COT 33 2.70 0.031 Runoff

04/08/2002 1837 USGS 189 3.60 0.150 Runoff

04/18/2002 0752 COT 29 2.90 0.043 Runoff

05/17/2002 1220 USGS 231 3.98 0.170 Runoff

05/23/2002 0805 COT 54 2.80 0.053 Runoff

05/28/2002 1542 USGS 519 4.68 0.810 Runoff

06/13/2002 0735 COT 58 2.57 0.053 Runoff

07/18/2002 0742 COT 7.2 2.27 0.033 Base flow

08/13/2002 0820 COT 1.8 1.45 0.045 Base flow

09/19/2002 0755 COT 0.08 1.15 0.048 Base flow

10/16/2002 0800 COT 0.07 1.24 0.041 Base flow

11/12/2002 0920 COT 2.8 1.34 0.032 Base flow

12/12/2002 0755 COT 4.4 1.34 0.029 Base flow

 

01/07/2003 0750 COT 7.2 1.79 0.039 Base flow

02/06/2003 0755 COT 3.9 1.53 0.021 Base flow

03/05/2003 0735 COT 39 2.93 0.024 Runoff

04/09/2003 0720 COT 17 2.16 0.028 Base flow

05/08/2003 0725 COT 12 1.53 0.038 Base flow

05/14/2003 0850 COT 26 4 2.01 0.039 Runoff

05/16/2003 1048 COT 127 1.41 0.077 Runoff

05/16/2003 1741 USGS 414 3.27 0.150 Runoff

05/20/2003 1929 USGS 263 3.60 0.280 Runoff

05/21/2003 1743 USGS 135 3.01 0.073 Runoff

06/02/2003 1755 USGS 118 3.78 0.064 Runoff

06/03/2003 0730 COT 108 2.30 0.040 Runoff

06/11/2003 1000 COT 22 2.27 0.038 Runoff

06/26/2003 1044 USGS 12 1.87 0.036 Runoff

07/10/2003 0750 COT 7.5 1.85 0.033 Base flow

08/05/2003 0730 COT 0.36 1.62 0.041 Base flow

09/02/2003 1549 USGS 15 1.13 0.043 Runoff

09/11/2003 0727 COT 3 0.87 0.032 Base flow

10/09/2003 0705 COT 4 0.93 0.032 Base flow
Appendixes 55

Appendix 5. Streamflows, and total nitrogen and total phosphorus concentrations for Beaty Creek near Jay, Oklahoma, 

2002–2006. —Continued

[COT, City of Tulsa; USGS, U.S. Geological Survey; ft3/s, cubic foot per second; mg/L, milligram per liter; N, nitrogen; P, phosphorus; --, not 

reported; all water-quality and streamflow data available at http://water.usgs.gov/ok/nwis]

Date Sample 

time

Agency 

collecting 

sample

Streamflow 1

(ft3/s)

Total nitrogen

concentration

(mg/L as N) 2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category 3

11/06/2003 0730 COT 6.4 1.00 0.036 Base flow

11/19/2003 1722 USGS 15 1.51 0.033 Runoff

12/10/2003 0750 COT 6.7 2.26 0.025 Base flow

01/06/2004 0735 COT 26 2.58 0.032 Runoff

01/18/2004 1205 USGS 212 3.45 0.110 Runoff

02/05/2004 0725 COT 25 4.02 0.032 Base flow

03/04/2004 0744 COT 1,350 4.93 0.964 Runoff

03/04/2004 1345 USGS 916 4.13 0.260 Runoff

03/29/2004 1720 USGS 346 3.39 0.094 Runoff

04/07/2004 0729 COT 29 3.42 0.039 Base flow

04/23/2004 1115 USGS 162 2.66 0.079 Runoff

04/24/2004 1030 USGS 1,080 3.28 0.460 Runoff

05/06/2004 0724 COT 186 3.32 0.045 Runoff

06/10/2004 0720 COT 20 2.66 0.045 Base flow

07/03/2004 1635 USGS 953 2.67 0.490 Runoff

07/08/2004 0720 COT 104 3.16 0.067 Runoff

08/05/2004 0729 COT 18 2.57 0.089 Base flow

09/09/2004 0718 COT 7.1 2.20 0.050 Base flow

10/07/2004 0720 COT 4 1.84 0.047 Base flow

11/01/2004 1120 USGS 2,050 4.24 1.000 Runoff

11/03/2004 0738 COT 181 3.05 0.102 Runoff

12/09/2004 0740 COT 144 3.67 0.077 Runoff

01/06/2005 0720 COT 603 4.11 0.270 Runoff

01/13/2005 1325 USGS 486 3.50 0.230 Runoff

02/10/2005 0730 COT 48 3.78 0.042 Base flow

03/10/2005 0730 COT 25 3.13 0.044 Base flow

04/07/2005 0735 COT 142 3.28 0.068 Runoff

05/12/2005 0625 COT 15 2.58 0.056 Base flow

06/09/2005 0755 COT 9.6 2.07 0.047 Base flow

06/14/2005 1030 USGS 85 1.89 0.070 Runoff

07/14/2005 0725 COT 4.0 1.47 0.055 Base flow

08/11/2005 0735 COT 0.61 0.89 0.043 Base flow

09/15/2005 0755 COT 0.09 0.88 0.068 Base flow

10/06/2005 0745 COT 0.04 0.99 0.054 Base flow

11/16/2005 0734 COT 2.8 1.16 0.040 Base flow
56 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002-2006

Appendix 5. Streamflows, and total nitrogen and total phosphorus concentrations for Beaty Creek near Jay, Oklahoma, 

2002–2006. —Continued

[COT, City of Tulsa; USGS, U.S. Geological Survey; ft3/s, cubic foot per second; mg/L, milligram per liter; N, nitrogen; P, phosphorus; --, not 

reported; all water-quality and streamflow data available at http://water.usgs.gov/ok/nwis]

Date Sample 

time

Agency 

collecting 

sample

Streamflow 1

(ft3/s)

Total nitrogen

concentration

(mg/L as N) 2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category 3

12/15/2005 0750 COT 1.7 1.18 0.029 Base flow

01/12/2006 0740 COT 2.1 1.37 0.100 Base flow

02/09/2006 0905 COT 1.7 1.21 0.031 Base flow

03/09/2006 0806 COT 2.6 1.45 0.028 Base flow

04/12/2006 0738 COT 2.1 1.04 -- Base flow

04/29/2006 1210 USGS 26 1.16 0.036 Runoff

05/02/2006 1125 USGS 35 1.57 0.034 Runoff

05/10/2006 0810 COT 535 2.70 0.230 Runoff

05/10/2006 1030 USGS 519 3.11 0.210 Runoff

06/08/2006 0745 COT 7.5 -- 0.039 Base flow

07/13/2006 0735 COT 5 0.1 -- 0.063 Base flow

08/29/2006 1125 USGS 19 1.77 0.051 Runoff

09/14/2006 0745 COT 2.8 0.67 -- Base flow

11/16/2006 0835 COT 0.67 0.91 -- Base flow

12/06/2006 0745 COT 32 3.47 -- Runoff

1

 Streamflow for data collected by USGS is measured instantaneous streamflow; streamflow for data collected by COT is daily mean 

streamflow unless streamflow changing rapidly during the day, then it is 30-minute unit value.

2

 Total nitrogen is calculated by adding Kjeldahl-N and nitrite plus nitrate analyses.

3

 Base flow and runoff designated by Base-Flow Index (BFI) program (Institute of Hydrology, 1980a, 1980b); with the additional qualifier 

that any discharge less than 10 ft3/s was designated base flow.

4

 Nitrite plus nitrate analyses not reported, nitrate analyses was substituted in the total nitrogen calculation for this sample.

5

 Instantaneous streamflow estimated by author for this sample from recorded 30-minute streamflow data.

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For more information concerning this publication, contact:

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202 NW 66th St., Bldg. 7

Oklahoma City, OK 73116

(405) 810-4400

Or visit the Oklahoma Water Science Center Web site at:

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