Scientific Investigations Report 2010–5119

U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with the City of Tulsa, Oklahoma

Nutrient Concentrations, Loads, and Yields in the 

Eucha-Spavinaw Basin, Arkansas and Oklahoma, 

2002–09
Front cover: Spavinaw Creek, Delaware County, Oklahoma (photograph by James Wellman, July 2004). 

Back cover:

Top, Spavinaw Creek near Colcord, Delaware County, Oklahoma (071912213), upstream from the 

streamflow-gaging station (photograph by Monica L. Allen, November 2006).

Bottom, Lake Eucha, Delaware County, Oklahoma, at dam site (photograph by Robert L. Blazs, U.S. 

Geological Survey, July 2001). 
Nutrient Concentrations, Loads, and Yields 

in the Eucha-Spavinaw Basin, Arkansas 

and Oklahoma, 2002–09 

By Rachel A. Esralew and Robert L. Tortorelli

In cooperation with the City of Tulsa, Oklahoma

Scientific Investigations Report 2010–5119

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

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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:

Esralew, R.A., and Tortorelli, R.L., 2010, Nutrient concentrations, loads, and yields in the Eucha-Spavinaw Basin, 

Arkansas and Oklahoma, 2002–09: U.S. Geological Survey Scientific Investigations Report 2010–5119, 61 p. 
iii

Contents

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

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

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

Study Area Description .......................................................................................................................5

Streamflow in the Eucha-Spavinaw Basin ......................................................................................5

Methods ..........................................................................................................................................................5

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

Streamflow Separation .....................................................................................................................11

Statistical Tests ..................................................................................................................................12

Load and Yield Estimation .................................................................................................................12

Nutrient Concentrations in Undeveloped Basins .........................................................................15

Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin .....................................15

Concentrations ...................................................................................................................................15

Nitrogen ......................................................................................................................................15

Phosphorus ................................................................................................................................23

Estimated Mean Annual Loads ........................................................................................................24

Nitrogen ......................................................................................................................................24

Phosphorus ................................................................................................................................25

Estimated Mean Seasonal Loads ....................................................................................................28

Nitrogen ......................................................................................................................................28

Phosphorus ................................................................................................................................29

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

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

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

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

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

Phosphorus ................................................................................................................................33

Estimated Mean Annual Nutrient Loads into Lake Eucha ..........................................................34

Summary .......................................................................................................................................................35

Acknowledgments .............................................................................................................................37

References Cited .........................................................................................................................................37

Appendixes 

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

Spavinaw Creek near Maysville, Arkansas, 2002–09 ..........................................................43

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

Spavinaw Creek near Cherokee, Arkansas, 2002–09 ..........................................................47

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

Spavinaw Creek near Sycamore, Oklahoma, 2002–09 ........................................................51

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

Spavinaw Creek near Colcord, Oklahoma, 2002–09 .............................................................54

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

Creek near Jay, Oklahoma, 2002–09 .......................................................................................58
iv

Figures

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

streamflow-gaging water-quality, and lake-level stations in the basin and towns 

with wastewater-treatment plants that discharge into streams in the basin ...................3

2. Comparison of land use in the basins draining to Spavinaw Creek near Colcord, Oklahoma (071912213), and Beaty Creek near Jay, Oklahoma (07191222), in the 

Eucha-Spavinaw Basin, Arkansas and Oklahoma .................................................................6

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, 2002–09 ............................................................................................7

4. Mean seasonal streamflow at five water-quality stations in the Eucha-Spavinaw 

Basin, Arkansas and Oklahoma, 2002–09 ..............................................................................10

5. Distribution of (A) total nitrogen and (B) total phosphorus concentrations in water 

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

and Oklahoma, 2002–09 ............................................................................................................16

6. Distributions of seasonal total nitrogen concentrations in water samples collected 

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

2002–09 ........................................................................................................................................17

7. Distributions of seasonal total phosphorus concentrations in water samples 

collected at water-quality stations in the Eucha-Spavinaw Basin, Arkansas and 

Oklahoma, 2002–09 ....................................................................................................................18

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

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

2002–09 ........................................................................................................................................19

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

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

2002–09 ........................................................................................................................................20

10. Total nitrogen annual total load, separated by annual load from base flow and 

annual load from runoff, and mean annual streamflow, at water-quality stations in 

the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09 ........................................25

11. Total phosphorus total annual load, separated by annual load from base flow and 

annual load from runoff, and mean annual streamflow, at water-quality stations in 

the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09 ........................................26

12. Instantaneous and estimated mean flow-weighted (A) total nitrogen and (B) total 

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

the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09 ........................................32

13. Graph showing percentage of estimated mean annual (A) total nitrogen and 

(B) total phosphorus load to Lake Eucha, for the period 2002-09, that is from base 

flow and from runoff, and the percentage of load contributed from Beaty Creek 

near Jay, Oklahoma (USGS station identifier 07191222) and Spavinaw Creek near 

Colcord, Oklahoma (USGS station identifier 071912213) .....................................................34

Tables

1. Estimates of fertilizer application, number of cattle and calves, and number of 

broilers and other chickens sold for counties in the Eucha-Spavinaw Basin, 

Arkansas and Oklahoma, 2002 and 2007 ..................................................................................4
v

2. Station information and streamflow statistics for surface-water and waterquality stations in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09 .......10

3. Mean base-flow index for surface-water and water-quality stations in the EuchaSpavinaw Basin, Arkansas and Oklahoma, 2002–09 ...........................................................11

4. 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 2002–09 ..........................................................................................................13

5. 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 2002–09 ..........................................................................................................14

6. 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, 2002–09 ..........................................................................................21

7. 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, 2002–09 ..........................................................................................22

8. Mann-Whitney rank-sum test results comparing base-flow total nitrogen or 

total phosphorus concentrations to runoff total nitrogen or total phosphorus 

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

Eucha-Spavinaw Basin, 2002–09 ............................................................................................23

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

methods from concentrations in water-quality samples collected at waterquality stations in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, for the 

period 2002–09 ............................................................................................................................27

10. 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, 2002–09 ....................28

11. 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, 2002–09 ....................................................................................................................29

12. 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, 

2002–09 ........................................................................................................................................29

13. 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, 2002–09 ....................................................................................................................30

14. 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, 2002–09 ....................33

15. Estimated mean annual total phosphorus loads, mean annual streamflows, and 

estimated mean flow-weighted total phosphorus concentrations at water-quality 

stations in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09 ....................33

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

Lake Eucha, Oklahoma, 2002–09 .............................................................................................35
vi

Conversion Factors

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)

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

/s)

Mass

pound (lb) 0.4536 kilogram (kg) 

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

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

pound per year per square mile 

[(lb/yr)/ mi2

]

 0.1751 kilogram per year per square kilometer 

[(kg/yr)/mi2]

ton 0.9072 megagram

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. These values are 

reevaluated annually based on the most current quality-control data and may, therefore, change 

(Childress and others, 1999). 
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. 

The city has spent millions of dollars over the last decade to 

eliminate taste and odor problems in the drinking water from 

the Eucha-Spavinaw system, which may be attributable to 

blue-green algae. Increases in the algal biomass in the lakes 

may be attributable to increases in nutrient concentrations 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 total nitrogen and total phosphorus concentrations in water samples and provided estimates of nitrogen 

and phosphorus loads, yields, and flow-weighted concentrations during base flow and runoff for two streams discharging 

to Lake Eucha for the period January 2002 through December 

2009. This report updates a previous report that used data from 

water-quality samples collected from January 2002 through 

December 2006.

Based on the results from the Mann-Whitney statistical 

test, unfiltered total nitrogen concentrations were significantly greater in runoff water samples than in base-flow water 

samples collected from Spavinaw Creek near Maysville and 

near Cherokee City, Arkansas; Spavinaw Creek near Colcord, 

Oklahoma, and Beaty Creek near Jay, Oklahoma. Nitrogen 

concentrations in runoff water samples collected from all stations generally increased with increasing streamflow.

Nitrogen concentrations in base-flow and runoff water 

samples collected in Spavinaw Creek significantly increased 

from the station furthest upstream (near Maysville) to the 

Sycamore station and then significantly decreased from the 

Sycamore station to the station furthest downstream (near 

Colcord). Nitrogen concentrations in base-flow and runoff 

water samples collected from Beaty Creek were significantly 

less than base-flow and runoff water samples collected from 

Spavinaw Creek. 

Based on the results from the Mann-Whitney statistical 

test, unfiltered total phosphorus concentrations were significantly greater in runoff water samples than in base-flow water 

samples for the entire period for most stations, except in water 

samples collected from Spavinaw Creek near Cherokee City, 

in which no significant difference was detected for the entire 

period nor for any season. Phosphorus concentrations in runoff 

water samples collected from all stations generally increased 

with increasing streamflow. 

Based on results from a multi-stage Kruskal-Wallis 

statistical test, phosphorus concentrations in base-flow 

water samples collected from Spavinaw Creek significantly 

increased from the Maysville station to the Cherokee City 

station, probably because of discharge from a municipal 

wastewater-treatment plant between those stations. Phosphorus 

concentrations significantly decreased downstream from the 

Cherokee City station to the Colcord station. Phosphorus concentrations in base-flow water samples collected from Beaty 

Creek were significantly less than phosphorus in base-flow 

water samples collected from Spavinaw Creek downstream 

from the Maysville station. 

Estimated mean annual nitrogen total and base-flow loads 

were substantially greater in Spavinaw Creek than in Beaty 

Creek, and increased downstream from the Maysville station 

to the Colcord station in Spavinaw Creek. Estimated mean 

annual phosphorus total loads were greater for the Spavinaw 

Creek stations from the Cherokee City station to the Colcord station than for the Beaty Creek station, and increased 

downstream from the Maysville station to the Colcord station 

in Spavinaw Creek. The runoff component of the mean annual 

nitrogen total load for Beaty Creek was 88 percent; whereas, 

for the Spavinaw Creek stations, the range in the runoff 

component accounted for 67 to 73 percent of the mean annual 

nitrogen load. 

The runoff component of the mean annual phosphorus 

total load for the Beaty Creek station was 98 percent; whereas, 

at the Spavinaw Creek stations, the range in the runoff component accounted for 79 to 93 percent of the mean annual phosphorus load. Annual nitrogen and phosphorus total, base-flow, 

and runoff loads were greatest during the calendar year 2008 

and lowest during the calendar year 2006.

Estimated mean annual nitrogen total yields ranged from 

6,160 to 8,070 pounds per year per square mile with the greatest yield at the Colcord station and the least yield at the Beaty 

Creek station.

Estimated mean annual phosphorus total yields ranged 

from 300 to 620 pounds per year per square mile with greatest 

the yield at the Beaty Creek station and the least yield at the 

Maysville station. 

Nutrient Concentrations, Loads, and Yields in the EuchaSpavinaw Basin, Arkansas and Oklahoma, 2002–09

By Rachel A. Esralew and Robert L. Tortorelli 
2 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

Estimated mean flow-weighted nitrogen concentrations at 

all stations in the basin were about 7 to 10 times greater than 

the 75th percentile of flow-weighted nitrogen concentrations 

(0.50 milligram per liter) in other mostly undeveloped basins 

of the United States. Estimated mean flow-weighted phosphorus concentrations at all stations in the basin were about five 

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

phosphorus concentrations (0.037 milligram per liter) in other 

mostly undeveloped basins of the United States. 

Spavinaw Creek and Beaty Creek contributed an estimated mean annual nitrogen total load of 1,681,000 pounds 

per year, 76 percent of which was transported to Lake Eucha 

by runoff. Spavinaw Creek and Beaty Creek contributed an 

estimated mean annual phosphorus total load of 108,390 

pounds per year, 91 percent of which was 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 (U.S. Geological 

Survey lake-level station at Spavinaw Lake, station identifier 

07191300, fig. 1) on Spavinaw Creek began in 1922 and was 

completed in 1924 (Oklahoma Water Resources Board, 2002). 

A series of pipelines 60-miles long was constructed to transfer 

water from the base of Spavinaw Lake Dam to a wastewatertreatment plant in Tulsa. Spavinaw Lake supplied Tulsa with a 

safe, reliable water supply (Oklahoma Water Resources Board, 

2002). In 1950, city officials decided to create an impoundment of Spavinaw Creek four miles upstream from Spavinaw 

Lake to serve as “an environmental and hydrologic barrier” 

for Spavinaw Lake to ensure a constant supply of clean water. 

This second dam came to be known as Eucha Dam (U.S. Geological Survey lake-level station at Lake Eucha, station identifier 07191285, fig. 1) that was finished in 1954 to impound 

Lake Eucha (fig. 1) (City of Tulsa City Services, 2008a).

The Eucha-Spavinaw system continues to be designated 

as a system for public water supply as well as for recreation, 

fish and wildlife, agriculture, and aesthetics (City of Tulsa 

City Services, 2008b). The Eucha-Spavinaw system provides 

59 million gallons per day (Mgal/d) to the Tulsa metropolitan 

area. During peak demand, the system can produce a maximum of 100 Mgal/d (City of Tulsa City Services, 2008b). 

Taste and odor problems in the drinking water have 

been reported by consumers to the City of Tulsa municipal 

agency (COT) (City of Tulsa City Services, 2008c). The Tulsa 

Metropolitan Utility Authority (TMUA) spent millions of 

dollars from 1998–2005 to eliminate taste and odor problems, 

likely attributable to the chemicals produced by blue-green 

algae, notably geosmin, in the drinking water from the EuchaSpavinaw system (Oklahoma Water Resources Board, 2002; 

City of Tulsa City Services, 2008c). Changes in the algal biomass and abundance in the lakes are the result of increases in 

nutrient concentrations in the tributaries of the lakes (City of 

Tulsa City Services, 2008c). 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). A study of phosphorous loading in this basin 

by the Oklahoma Conservation Commission report indicated 

increasing nutrient content of Spavinaw Creek, a main tributary to Lake Eucha (fig. 1), between 1975 and 1995 (Wagner 

and Woodruff, 1997). Lake Eucha and Spavinaw Lake were 

nutrient-enriched (phosphorus was the limiting nutrient), and 

high or excessive levels of algal production were detected in 

the lakes (Oklahoma Water Resources Board, 2002). 

Nitrogen and phosphorus can enter streams in discharges from wastewater-treatment plants (point-source 

components) and in agricultural and urban runoff (nonpointsource components) (Oklahoma Water Resources Board, 

2002). The main sources of elevated nitrogen and phosphorus 

concentrations in streams in the Eucha-Spavinaw Basin are 

from nonpoint sources (notably runoff from fertilized pastures) 

and point sources (notably wastewater discharge) (Tortorelli, 

2008; City of Tulsa, 2010). Pastures fertilized with animal 

manure or commercial fertilizer probably are substantial 

sources of nitrogen and phosphorus delivered to the streams in 

this basin, especially during runoff (Storm and others, 2002). 

One possible major contributor of nutrients to the creeks 

feeding Lake Eucha and Spavinaw Lake is the phosphorousrich waste produced by commercial poultry raising 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 (Storm and others, 2002). As of 2001, production of 1,500 tons of nitrogen and phosphorous-rich waste in 

the basin per year was estimated (Tulsa Metropolitan Utility 

Authority, 2001). As of 2007, the poultry operations in the 

Eucha-Spavinaw Basin have the capacity to produce more than 

160 million birds (U.S. Department of Agriculture, 2009; table 

1). More than 84,000 acres were treated with manure in 2002, 

but this amount was reduced to about 52,000 acres in 2007 

(U.S. Department of Agriculture 2004 and 2009, table 1). In 

2001, the COT filed suit against several poultry-producing 

companies. The lawsuit was settled out of court and in 2004 

resulted in a substantial reduction in land application of poultry litter (City of Tulsa, 2010). The reduction in litter application may have led to the decrease in treated acres between 

2002 and 2007.

Nutrient concentrations in streams vary throughout the 

year, mainly in response to variation in precipitation and 

streamflow, and to variation in the timing of fertilizer or 

manure applications (U.S. Geological Survey, 1999). Nutrient 

concentrations in streams may be greater during occurrences 

of high streamflow, especially during spring and summer after 

fertilizer application. Increased nutrient concentrations were 
Introduction 

3

Figure 1. The Eucha-Spavinaw Basin, Arkansas and Oklahoma, with locations of selected streamflow-gaging water-quality, and lake-level stations in the basin and towns with wastewater-treatment plants that discharge into streams in the basin. 

Study area

Oklahoma Arkansas

Index map

Spavinaw Lake07191300

Boundary ofbasin

Arkansas Oklahoma

Lake Eucha07191285

Eucha07191288 Jay

07191222

Colcord071912213

Sycamore07191220

Cherokee City07191179

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

07191288

071912213

07191285

0 50 5

10 KILOMETERS

10 MILES

U.S. Geological Survey streamflow-gaging  station and numberU.S. Geological Survey streamflow-gaging  and water-quality station and number (table 1)U.S. Geological Survey lake-level station  and numberTown with water-treatment plant that 

 discharges into streams in the Eucha- Spavinaw Basin

EXPLANATION

36°30’

95°00’ 94°45’ 94°15’ 94°30’

36°15’

LakeHudson

SpavinawLake

LakeEucha

Creek

Beaty

Creek

Spavinaw

Tulsa

Benton County

Delaware County
4 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

detected in streams during seasonal low flows. In particular, 

nitrogen and phosphorus concentrations may be elevated in 

streams downstream from urban areas during seasonal low 

flows when contributions from point sources, such as wastewater treatment plants, are greater relative to streamflow, and 

dilution is minimal (U.S. Geological Survey, 1999).

Potential means of minimizing eutrophication in the 

Eucha-Spavinaw Basin include: (a) reduction in the quantities of nutrients running off or seeping into surface water, 

and (b) control of the ratios of nitrogen and phosphorus in 

tributaries that deliver these nutrients to the lakes. Nitrogen-tophosphorus ratios are useful for general guidance as to what 

nutrient may be most likely to encourage plant growth in surface water, but if nutrient concentrations are sufficiently large, 

then these nutrients may be available for uptake regardless of 

the ratio. Nitrogen-to-phosphorus ratios of 20 to 1 or greater 

indicate potential deficiency of phosphorus; whereas, ratios of 

10 to 1 or less indicate potential deficiency of nitrogen (United 

Nations Environmental Programme, 2007). Blue-green algae 

tend to bloom when phosphorus concentrations are increased 

relative to nitrogen (Levich, 1996). However, total phosphorus 

and total nitrogen may not be readily available for uptake, 

because these constituents may be bound to small colloids or 

other particles (Jones and Knowlton, 1993). 

As of 2010, the USGS has operated five continuous 

streamflow-gaging and water-quality data collection stations 

in the Eucha-Spavinaw Basin in Arkansas and Oklahoma: 

Spavinaw Creek near Maysville, Arkansas; Spavinaw 

Creek near Cherokee City, Arkansas; Spavinaw Creek near 

Sycamore, Oklahoma; Spavinaw Creek near Colcord, Oklahoma; and Beaty Creek near Jay, Oklahoma (fig. 1). For the 

remainder of this report, these stations are referred to as the 

Maysville station, Cherokee City station, Sycamore station, 

and Colcord station on Spavinaw Creek (or collectively as 

the “Spavinaw Creek stations”), and the Beaty Creek station, 

respectively.

Historically, water-quality data collection for stations 

in the Eucha-Spavinaw Basin has been on a fixed monthly 

schedule. Most of the water samples were collected during 

base flow (nonrunoff) because runoff events are variable and 

infrequent. For this report, all samples are water samples. 

Because of the lack of runoff samples collected, 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 COT, supplemented 

scheduled monthly water-quality sampling with six targeted 

runoff samplings per year for five stations to better determine 

water quality over a broader range of streamflows in the basin. 

The period 2002–09 encompasses a period where the runoff 

sampling protocol was in effect. The USGS, in cooperation 

with COT, 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 from January 2002 through 

December 2009.

Purpose and Scope

The purpose of this report is to summarize nutrient 

concentrations, loads, and yields in the Eucha-Spavinaw Basin 

from January 2002 through December 2009. Specifically, total 

nitrogen and total phosphorus concentrations in water samples 

are summarized and estimates of nitrogen and phosphorus 

loads, yields, and flow-weighted concentrations in base flow 

Table 1. Estimates of fertilizer application, number of cattle and calves, and number of broilers and other chickens sold for counties in 

the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002 and 2007.

[modified from U.S. Department of Agriculture (2004, 2009)]

County

Percentage 

of county 

in drainage 

basin of 

Beaty Creek 

near Jay 

(station 

07191222)

Percentage 

of county 

in drainage 

basin of 

Spavinaw 

Creek near 

Colcord 

(station 

071912213)

Farmland 

(acres)

Year

Acres 

treated 

with 

commercial 

fertilizer

Acres 

treated 

with 

manure

Total 

acres 

treated

Percent of 

county area 

(farms only) 

treated with 

fertilizer1

Number of 

cattle and 

calves

Number 

of broilers 

and other 

chickens 

sold

Delaware, Okla. 67.4 23.5 282,106

2002 53,185 21,346 74,531 26 74,719 37,154,935

2007 57,613 17,926 75,539 27 83,197 47,971,853

Benton, Ark. 32.6 76.5 312,646

2002 84,703 62,829 147,532 47 113,588 128,066,609

2007 57,786 33,779 91,565 29 94,588 116,599,600

1

 Fertilizer application to land other than farms (for example, golf courses or residences) was not included.
Methods 5

and runoff are provided. This report updates the work of 

Tortorelli (2008), which used water-quality and streamflow 

data from 2002 to 2006 and was a preliminary analysis of data 

collected for a multiyear monitoring program.

Nitrogen and phosphorus concentrations are compared 

among five 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, U.S. Geological Survey, written 

commun., 2006). S-LOADEST, based on LOADEST (LOAD 

ESTimator, Runkel and others, 2004), uses instantaneous 

nutrient concentrations and daily mean streamflows to 

estimate mean annual and mean seasonal (spring, summer, 

autumn, and winter) nutrient loads and mean annual nutrient 

yields for the study period. 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.

Study Area Description

The Eucha-Spavinaw Basin is a 415-square mile drainage basin divided between northeastern Oklahoma (70 

percent), and northwestern Arkansas (30 percent) (fig. 1). 

Lake Eucha and Spavinaw Lake collect and store water from 

Spavinaw Creek and Beaty Creek, the main drainage channels 

for the basin, to supply the Tulsa metropolitan area and other 

local water users (Oklahoma Water Resources Board, 2002). 

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). Soils are mostly classified as 

silty loam or gravelly silty loam (Storm and others, 2002). 

The basin is dominated by pasture and hay and forested land, with interspersed minor amounts of urban land 

use (fig. 2). Spavinaw Creek Basin has more land covered 

by forest (39 percent) than Beaty Creek Basin (31 percent), 

and has less land covered by pasture and hay (54 percent) 

than Beaty Creek Basin (62 percent) (fig. 2). Nitrogen and 

phosphorus concentrations in Ozark streams typically are 

greater in streams draining agricultural lands than in streams 

draining forested lands (Petersen and others, 1998). Livestock 

production on pasture land is the primary form of agriculture 

in the basin; the basin is densely populated with poultry/beef 

cattle operations that use poultry litter as a fertilizer source 

for pastures (DeLaune and others, 2006, table 1). Litter 

application rates are greater in the Spavinaw Creek Basin 

than in Beaty Creek Basin (Storm and others, 2002, p. 25). 

A municipal wastewater-treatment plant, operated by 

the city of Decatur, Arkansas, discharges an estimated 1.3 

Mgal/d of wastewater effluent containing nitrogen and phosphorus to the Spavinaw Creek Basin according to data collected in 1999 (Haggard and others, 2001; Storm and others, 

2002; DeLaune and others, 2006). This wastewater-treatment 

plant is referred to as the “Decatur wastewater-treatment 

plant” for this report. The Decatur wastewater-treatment plant 

has a wasteload allocation permit of 2.2 Mgal/d and a discharge limit of 1 milligram per liter (mg/L) total phosphorus 

and 10 mg/L ammonia as nitrogen (U.S. Environmental 

Protection Agency and Oklahoma Department of Environmental Quality, 2009). A smaller wastewater-treatment plant 

located in Beaty Creek Basin has a wasteload allocation permit of 0.56 Mgal/d, but nutrient contributions to Lake Eucha 

from that plant are considered substantially less because of 

the intermittent nature of the discharge (U.S. Environmental 

Protection Agency and Oklahoma Department of Environmental Quality, 2009). 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).

Streamflow in the Eucha-Spavinaw Basin

Streamflow in the Eucha-Spavinaw Basin was highly 

varied from 2002 to 2009 and generally increased with basin 

drainage area (table 2, figs. 3–4). The maximum daily mean 

streamflow during the study period was in July 2004 for the 

three upstream Spavinaw Creek stations, March 2008 for the 

Colcord station, and January 2008 for the Beaty Creek station 

(table 2, fig. 3). The minimum daily mean streamflow during 

the study period was in August 2006 for the three upstream 

Spavinaw Creek stations; July 2006 at the Colcord station; 

and zero flow happened several times at the Beaty Creek 

station in September–October 2002, August 2003, October 2005, and July–October 2006 (table 2, fig. 3). Greatest monthly mean streamflows generally were from March 

through May and least monthly mean streamflows generally 

were from August through December at all stations (Blazs 

and others, 2003, 2004, 2005, 2006; U.S. Geological Survey, 

2007, 2008b, 2009). Seasonal mean streamflows during the 

period 2002–2009 were greater for spring and winter than for 

summer and autumn (fig. 4). In this report, spring is March 

through May, summer is June through August, autumn is September through November, and winter is December through 

February. 

Methods

This section describes the water-quality data-collection 

and analysis methods. These methods include streamflow 

separation into base flow and runoff, statistical tests used to 

compare groups of data, and methods used to estimate total 

nitrogen and phosphorus loads and yields. Flow-weighted 

nutrient concentrations for stations in undeveloped basins used 

to compare with the data collected in the Eucha-Spavinaw 

Basin also are presented.
6 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

Figure 2. Comparison of land use in the basins draining to Spavinaw Creek near Colcord, Oklahoma (071912213), and Beaty Creek near Jay, Oklahoma (07191222), in the EuchaSpavinaw Basin, Arkansas and Oklahoma. 

#*

#*

Oklahoma

Arkansas

!

Tulsa Benton County

Delaware County

Oklahoma

Arkansas

*

*

Study Area

Land-use in the drainage basin of 

Beaty Creek near Jay (07191222)

Land-use in the drainage basin of Spavinaw 

Creek near Colcord (071912213)

Pasture/Hay

62%

Forested

31%

Other

2% Row Crops

1%

Urban

4%

Pasture/Hay

54%

Other

2% Urban 4%

Forested

39%

Row Crops

EXPLANATION

Land-cover classes

#*

UrbanForestedPasture/HayRow CropsOtherBoundary of sampling basin 

Spavinaw Creek

Beaty Creek

Jay (07191222)

Colcord (071912213)

94°30'W 94°45'W

36°15'N

0%

Percent

%

U.S. Geological Survey streamflowgaging station and water-quality monitoring station and number

Sycamore (07191220)

Maysville (07191160)

Cherokee City (07191179) 

Based on National Landcover Databaset (Mulit-Resolution Land Characteristics Consortium, 2008) and National Hydrography Dataset (U.S. Geological Survey, 2008a)Albers Equal-Conic projectionNorth American Datum of 1983
Methods 7

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, 2002–09.

104

103

102

101

100

10-1

10-2

104

103

102

101

100

10-1

10-2

YEAR

STREAMFLOW, IN CUBIC FEET PER SECOND

Spavinaw Creek near Maysville, Arkansas

Spavinaw Creek near Cherokee City, Arkansas

2002 2003 2004 2005 2006 2007 2008 2009

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, 2002-09
8 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

Figure 3.—Continued.

104

103

102

101

100

10-1

10-2

104

103

102

101

100

10-1

10-2

YEAR

STREAMFLOW, IN CUBIC FEET PER SECOND

Spavinaw Creek near Sycamore, Oklahoma

Spavinaw Creek near Colcord, Oklahoma

2002 2003 2004 2005 2006 2007 2008 2009
Methods 9

Water-Quality Data Collection and Analysis

Streamflow-gaging stations 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 a range of streamflow, 

from low to high, and be reasonably balanced among seasons 

(A.V. Vecchia, U.S. Geological Survey, written commun., 

2005). Prior to July 2001, only scheduled, monthly waterquality samples were collected at these stations by staff from 

COT and included few runoff samples. Starting in July 2001 

at the Cherokee City station, Colcord station, and Beaty 

Creek station and December 2001 at the Maysville station and 

Sycamore station, six rwater-quality samples were targeted 

to be collected annually during runoff at these stations by the 

USGS. Because of climate variability, more than six runoff 

samples were collected in some wet years and fewer than six 

runoff samples were collunoff ected in some dry years (fig. 3). 

Representative water-quality samples were collected by USGS 

during high flow by using equal-width increment methods 

(Edwards and Glysson, 1999). USGS staff attempted to collect most runoff samples close to the storm peak, but some 

storm samples were collected before or after the storm peak. 

Samples collected by the COT, mostly during low flow at fixed 

monthly intervals, were collected at a single point near the 

midpoint of the stream. Fewer samples were collected from 

the Sycamore station than other stations because this station 

was located between the stations near Colcord, Oklahoma, 

and near Cherokee City, Arkansas. Samples for nitrogen and 

phosphorus constituents were not filtered in the field. Nitrogen 

and phosphorus concentrations represent both dissolved and 

particulate components. 

The COT Water Quality Laboratory in Tulsa, Oklahoma, 

analyzed all water-quality samples by using methods described 

by the U.S. Environmental Protection Agency (U.S. Environmental Protection Agency, 1983, 1993). EPA method code 

Figure 3.—Continued. .

EXPLANATION

Base flow water-quality sample (Instantaneous streamflow)

Runoff water-quality sample (Instantaneous streamflow)

Total flow (daily mean streamflow)

Base flow (daily mean streamflow)
10 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

Figure 4. Mean seasonal streamflow at five water-quality stations in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09. 

0

50

100

150

200

250

Spavinaw Creek near 

Maysville, Ark,

Spavinaw Creek near 

Cherokee City, Ark.

Spavinaw Creek near 

Sycamore, Okla,

Spavinaw Creek near 

Colcord, Okla,

Beaty Creek near 

Jay, Okla,

EXPLANATION

Spring, March through May

Summer, June through August

Autumn, September through November

Winter, December through February

MEAN SEASONAL STREAMFLOW, IN CUBIC FEET PER SECOND

Table 2. Station information and streamflow statistics for surface-water and water-quality stations in the Eucha-Spavinaw Basin, 

Arkansas and Oklahoma, 2002–09.

[WY, water year (October 1 through September 30); mi2, square mile; ft3/s, cubic foot per second]

 Station name 

(number, fig. 1)

Period of 

record for 

station 

(WY)

Drainage 

area 

(mi2

)

Annual mean 

streamflow 

for analysis 

period1

(ft3

/s) 

Range of streamflow

Minimum 

streamflow 

(ft3

/s and date) 

Maximum 

streamflow 

(ft3/s and date) 

Spavinaw Creek near Maysville, Ark. (07191160) 2002–present 88.2 71.0 4.2 

(08/04/2006) 

4,150 

(07/03/2004) 

Spavinaw Creek near Cherokee City, Ark. (07191179) 2002–present 104 86.9 7 

(08/01/2006)

5,180 

(07/03/2004) 

Spavinaw Creek near Sycamore, Okla. (07191220) 1962–present 133 107.0 7.7 

(08/18/2006)

6,300 

(07/03/2004) 

Spavinaw Creek near Colcord, Okla. (071912213) 2002–present 163 148.9 8.7 

(07/29/2006)

8,720 

(03/19/2008) 

Beaty Creek near Jay, Okla. (07191222) 1998–present 59.2 53.1 0 at times 

(2002, 2003, 

2005, 2006)

6,320 

(01/8/2008) 

1

 Analysis period for this report was January 1, 2002 to December 31, 2009.
Methods 11

351.2 was used to analyze for total Kjeldahl Nitrogen, EPA 

method code 353.2 was used to analyze for nitrate plus nitrite, 

and EPA method code 365.2 was used to analyze for total 

phosphorus (U.S. Environmental Protection Agency, 1983, 

1993). Total nitrogen concentrations were calculated by adding total Kjeldahl Nitrogen (measure of ammonia plus organic 

nitrogen) and nitrite plus nitrate analyses. Total 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 2009 were analyzed for 

this report. All streamflow and water-quality data in this report 

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 waterquality field studies (U.S. Geological Survey, 2006) and 

compose an integral 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 environmental 

samples. The COT collected QC samples at the rate of about 

11 percent.

Two blank samples were collected from the Beaty Creek 

station in 2006 and one blank sample was collected from the 

Sycamore station in 2007. Total phosphorus concentrations 

were 0.011 and 0.006 mg/L in the two samples collected from 

the Beaty Creek station; whereas the total phosphorus concentration was nondetectable (<0.015 mg/L) in the blank sample 

collected at the Sycamore station. Total nitrogen constituents 

were nondetectable (<0.1 mg/L total Kjehldahl Nitrogen and 

<.047 mg/L nitrate plus nitrite) in the two blank samples collected at Beaty Creek. Total Kjehldahl Nitrogen was nondetectable (<0.1 mg/L) but the nitrate plus nitrite concentration 

was 0.22 mg/L for the blank sample collected at the Sycamore 

station. The results from the blank samples indicate that some 

contamination may have been as a result of sample collection 

or sample processing and some bias from potential contamination should be considered in evaluating the nutrient data in 

this report. Concentrations in field samples collected between 

2002 and 2009 and used in this report ranged from 0.67 to 

10.4 mg/L for total nitrogen and 0.02 to 1.60 mg/L for total 

phosphorus. Sequential replicate analyses were conducted 

for 78 samples: 13 replicate samples were collected from the 

Maysville Station, 10 replicate samples were collected from 

the Cherokee City station, 10 replicate samples were collected 

from the Sycamore station, 2 replicate samples were collected from the Colcord station, and 43 replicate samples were 

collected from the Beaty Creek station,. The relative percentage difference between sequential replicate analyses for nitrate 

plus nitrite, the main component of total nitrogen, was less 

than 1 percent. The relative percentage difference between 

sequential replicate total phosphorus analyses was 3 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 considered the runoff 

sustained after the end of storm runoff or fair-weather flow of 

the stream. Base flow is largely composed of ground-water 

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

components were separated because base-flow concentrations 

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 Wahl, 1995). 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. 

The mean fraction of annual total flow that was runoff, 

computed by using streamflow data for the period 2002–2009, 

ranged from 44 to 50 percent at stations on Spavinaw Creek 

and 69 percent at the Beaty Creek station (table 3). The lesser 

runoff percentage at Spavinaw Creek may indicate a greater 

proportion of groundwater inputs in the Spavinaw Creek Basin 

than in the Beaty Creek Basin.

Each day of the study period was designated to be base 

flow or runoff by using results from the base-flow index 

program. Base-flow days in this report were defined as days 

during which base flow contributed greater than or equal to 

Table 3. Mean base-flow index for surface-water and waterquality stations in the Eucha-Spavinaw Basin, Arkansas and 

Oklahoma, 2002–09.

Station name 

(number)

Mean baseflow index 

(percent)1

Mean 

percent 

runoff

Spavinaw Creek near Maysville, Ark. 

(07191160)

56 44

Spavinaw Creek near Cherokee City, Ark. 

(07191179)

54 46

Spavinaw Creek near Sycamore, Okla. 

(07191220)

50 50

Spavinaw Creek near Colcord, Okla. 

(071912213)

52 48

Beaty Creek near Jay, Okla. (07191222) 31 69

1

 The mean ratio of base flow to total flow, computed using the Base-Flow 

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

Wahl, 1995).
12 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

70 percent of total flow; runoff days were defined as days during which runoff contributed greater than 30 percent of total 

flow (Tortorelli and Pickup, 2006; Tortorelli, 2006).

Statistical Tests

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

1992), used to compare the median and distribution of two 

independent groups of data, was used to determine the statistical significance of differences between base-flow and runoff 

nitrogen concentrations and base-flow and runoff phosphorus 

concentrations in samples collected at each station in the 

study period. Mann-Whitney rank-sum tests were performed 

to compare differences between base-flow and runoff nutrient 

concentrations in samples collected during the entire period 

and between base-flow and runoff nutrient concentrations in 

samples collected during different seasons (spring, summer, 

autumn, and winter). The Mann-Whitney test was not performed for any given season if less than 10 base-flow or runoff 

samples were available for comparison.

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 seasons in base-flow 

and runoff data groups for each station. The Kruskal-Wallis 

test also 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 in samples collected during the entire period.

The Mann-Whitney and Kruskal-Wallis statistical tests 

were selected because the tests do not require normally distributed data. The null hypothesis of the tests is no differences 

in the median and distribution of concentrations among the 

datasets being compared. The null hypothesis was rejected and 

concentrations 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 concentrations were 

described as being significantly different, the multiple-stage 

Kruskal-Wallis test was applied to determine which seasons 

were different or which stations were different and which were 

not (Helsel and Hirsch, 1992).

Load and Yield Estimation

Linear regression was used to evaluate relations between 

nitrogen and phosphorus loads (dependent variables) and 

streamflow and time (independent 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 by using 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 for discrete water-quality samples 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. 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, U.S. Geological Survey, written 

commun., 2006) was used to estimate constituent loads in the 

Eucha-Spavinaw Basin by the rating-curve method (Cohn 

and others, 1989; Crawford, 1991). S-LOADEST is based 

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

in the computer program Spotfire S-Plus (TIBCO Software 

Incorporated, 2008) to facilitate graphical analysis and tabular 

results. S-LOADEST estimates rating-curve parameters and 

mean daily loads by using maximum likelihood regression 

methods (Dempster and others, 1977; Wolynetz, 1979; Cohn, 

1988; and Cohn and others, 1992). 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

 by using a derivation of the following 

equation:

ln(L) = bo + b1 lnQ + b2 lnQ2 + b3T + b4T2

(1) + b5

 sin SS + b6 cos SS

where

ln is natural logarithm

L is constituent load, in pounds per day;

b0 is regression constant, dimensionless;

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

Q is daily mean streamflow, in cubic feet per 

second; 

T is dectime, time parameter in decimal 

years;

sin is sine;

SS is seasonality parameter (2πdectime); and

cos is cosine. 

S-LOADEST allows users to select the “best” model to 

estimate constituent load given a various combination of 

streamflow, time, and seasonal coefficients, by using one or 

all the variables from equation (1). S-LOADEST computes the 

Akaike Information Content (AIC) from each possible model, 

and the model with the lowest AIC is selected as the “best” 

model (Runkel and others, 2004) that most closely fits the data 

with a minimum number of independent variables (Akaike, 

1974).

Modeling scenarios in equation 1 will have multicollinearity present between the streamflow and time terms (Q 

and T, respectively) because the quadratic terms are included 

in the regression model. Multicollinearty arises when one of 

the independent variables is related to one or more of the other 

independent variables (Helsel and Hirsch, 1992). The presence 
Methods 13

of collinear independent variables is undesirable because it 

confounds interpretation of model coefficients and tests of the 

significance (Runkel and others, 2004; p. 13). To avoid multicollinearity, S-LOADEST computes the center of the calibration data (Cohn and others, 1992) with the following equation:

(2)

Where,

Ĉ is the centering constant for the S-LOADEST 

calibration dataset,

N is the number of observations in S-LOADEST 

calibration data set and is an integer that defines the 

upper bound of summation,

─

k is the first integer of the lower bound of summatio

 С is the mean of the data, and 

C is the quantity to be centered (decimal time or the 

natural logarithm of daily mean streamflow).

Within S-LOADEST, is subtracted from each Ĉ C in 

the calibration dataset, and the resulting “centered” values are 

used to develop the linear model. As a result, the linear and 

quadratic terms are orthogonal and no longer collinear. 

Separate linear regression models were developed in 

S-LOADEST for the estimation of nitrogen and phosphorus 

loads for the period 2002–09 at each station. The regression 

models developed by S-LOADEST are listed in tables 4 and 5. 

The centering constants for each variable are included for each 

regression model. 

The “best” model indicated in S-LOADEST was different for each nutrient and station. One general model (based 

on equation 1) was selected for all stations for each nutrient: 

(1) to use a consistent general model to estimate daily loads 

at all stations in the basin for each nutrient, and (2) because 

an analysis of the “best” models compared with this general model indicated a very small improvement in reduction 

in variance for each estimate. Each final model selected to 

estimate daily nitrogen and phosphorus load included the 

least number of independent variables that contained all the 

independent variables selected for any of the “best” models 

for each constituent and station (tables 4 and 5). The general equation selected to estimate daily nitrogen load for all 

stations was the same as equation 1. The general equation 

selected to estimate daily phosphorus load for each station 

was similar to equation 1, but did not include a quadratic term 

for time (T2

) because the quadratic form of this variable was 

not a statistically significant estimator of phosphorus load 

at the 95 percent confidence limit in any of the regression 

equations.

Only one model was developed for each nutrient at 

all stations for the period 2002–09 in this report. In previous reports, 3-year periods were used to average annual 

climate variation and to emulate a 3-year moving average 

(Tortorelli, 2006, 2008). Different model coefficients for each 

3-year period (2002–04, 2003–05, and 2004–06) were used in 

previous reports to allow the slope between L and Q to vary 

Table 4. 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 2002–09.

[no., number; obs., observations; ln, natural logarithm; L, daily load in pound per day; Q, mean daily streamflow in cubic foot per second; T, decimal time, time 

parameter in decimal years; sin, sine; cos, cosine; SS, seasonality parameter; R2, coefficient of determination]

Station name 

(number)

No. of 

obs. Total nitrogen load regression model1

Estimated 

residual 

variance2

R2

(percent)

Spavinaw Creek near Maysville, 

Ark. (07191160)

Spavinaw Creek near Cherokee 

City, Ark. (07191179)

Spavinaw Creek near Sycamore, 

Okla. (07191220)

Spavinaw Creek near Colcord, 

Okla. (071912213)

Beaty Creek near Jay, Okla. 

(07191222)

139

140

102

152

146

ln(L) = 8.09 + 1.13*(lnQ-4.93) - 0.018*(lnQ-4.93)2

 - 0.005*(T-2005.92) 

+ 0.002*(T-2005.92)2 - 0.013*sin SS + 0.14*cos SS

ln(L) = 8.44 + 1.08*(lnQ-5.18) - 0.015*(lnQ-5.18)2

 + 0.002*(T-2005.92) 

- 0.002*(T-2005.92)2 + 0.002*sin SS + 0.176*cos SS

ln(L) = 8.78 + 1.07*(lnQ-5.41) + 0.003*(lnQ-5.41)2

 - 0.001*(T-2005.92) 

- 0.003*(T-2005.92)2 + 0.012*sin SS + .169*cos SS

ln(L) = 8.66 + 1.10*(lnQ-5.50) - 0.010*(lnQ-5.50)2 - 0.006*(T-2005.97) 

- 0.001*(T-2005.97)2 + 0.025*sin SS + 0.176*cos SS

ln(L) = 5.51 + 1.14*(lnQ-2.80) - 0.001*(lnQ-2.80)2 + 0.014*(T-2005.99) 

+ 0.013*(T-2005.99)2 + 0.124*sin SS - 0.124*cos SS

0.048

.026

.021

.029

.076

98.3

99.0

99.1

99

98.9

1

 The seasonality parameter (SS) is computed as 2*π*dectime. 

2

 Estimated residual variance is the variance corrected for the number of observations and number of parameters in the regression model. 
14 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

with time instead of having one slope for the 5-year period, 

2002–06, to improve model fit. However, the variability of 

the slope between L and Q with time is accounted for in one 

model by including time (T) as a parameter in the regression 

model. The use of one equation facilitates comparison of 

resulting models for each station for the entire sampling period 

and is a more efficient means of computing total constituent 

load because only one estimate of annual load is generated 

(David K. Mueller, U.S. Geological Survey, oral and written 

commun., April 2009). Annual and seasonal load estimates 

presented in this report may differ slightly from estimates 

presented in Tortorelli (2008) because an updated load model 

was used.

The use of one equation also is helpful for evaluation of 

changes in the slope between L and Q with time (T) for the 

entire sampling period. A statistically significant time variable 

(T) that is positive or negative may signify a trend in flowadjusted constituent concentrations during the sampling period 

that is upward or downward, respectively (Helsel and Hirsch, 

1992, p. 337–371). Further evaluation of the time variable may 

be used to assess the statistical significance and magnitude of 

trends in constituent concentration over time. Documentation 

of the significance and magnitude of trends in nitrogen and 

phosphorus concentrations over time was beyond the scope of 

this report.

For consistency with previous publications (Tortorelli, 

2006, 2008), S-LOADEST was used to estimate daily constituent load, which was used to compute annual loads. All 

annual loads are computed by calendar year (January 1 to 

December 31). The daily load estimate from the S-LOADEST 

model is considered a daily mean load, and instantaneous 

loads were not estimated. A limitation of this approach is the 

assumption that daily mean load is not substantially different 

than maximum or minimum instantaneous load. A potential 

bias of this approach is that total daily load may be over or 

underestimated, depending on the flow condition (Christensen 

and others, 2008; Tortorelli, 2008). Such bias may occur 

during extremely flashy runoff because peak instantaneous 

streamflow is substantially greater than daily mean streamflow resulting in a total daily load that is greater than daily 

mean load. Therefore, the S-LOADEST methods used in this 

approach may underestimate total constituent load at a daily 

time scale. This bias may affect the computation of annual 

load from daily load estimates during years in which substantial runoff events are frequent. 

Data from most stations generally fit the model better 

for nitrogen than for phosphorus (tables 4 and 5). Data from 

the Beaty Creek station fit the model for phosphorus better 

than data from the Spavinaw stations, as indicated by a higher 

coefficient of determination (R2

) for the Beaty Creek load 

model (table 5). The R2 of a model is the square of sample correlation coefficient that is a measure of differences in observed 

data and data estimated from the model (Helsel and Hirsch, 

1992) and ranges from 0 to 1. An R2 of 1 indicates no difference between observed and estimated data (Helsel and Hirsch, 

1992). Nitrogen S-LOADEST equation coefficients for Q and 

T terms were similar to the equation coefficients reported in 

Tortorelli (2008) for all three 3-year moving periods. Phosphorus S-LOADEST equation coefficients for Q terms were 

similar to the equation coefficients reported in Tortorelli 

(2008), but the T terms were not comparable because the 

S-LOADEST equation from this report did not include a 

Table 5. 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 2002–09.

[no., number; obs., observations; ln, natural logarithm; L, daily load in pound per day; Q, mean daily streamflow in cubic foot per second; T, decimal time, time 

parameter in decimal years; sin, sine; cos, cosine; SS, seasonality parameter; R2, coefficient of determination]

Station name 

(number)

No. of 

obs. Total phosphorus load regression model1

Estimated 

residual 

variance2

R2

(percent)

Spavinaw Creek near 

Maysville, Ark. (07191160)

133 ln(L) = 3.63 + 1.54*(lnQ-4.93) + 0.159*(lnQ-4.93)2 + 0.023*(T-2005.93) 

- 0.089*sin SS - 0.135*cos SS

0.200 96.3

Spavinaw Creek near Cherokee City, Ark. (07191179)136 ln(L) = 4.80 + 1.22*(lnQ-5.18) + 0.146*(lnQ-5.18)2

 - 0.125*(T-2005.93) 

- 0.125*sin SS + 0.005*cos SS

.126 96.0

Spavinaw Creek near Sycamore, Okla. (07191220)100 ln(L) = 4.91 + 1.30*(lnQ-5.41) + 0..123*(lnQ-5.41)2

 - 0.084*(T-2005.92) 

- 0.014*sin SS - 0.044*cos SS

.101 97.1

Spavinaw Creek near Colcord, 

Okla. (071912213)

148 ln(L) = 5.06 + 1.37*(lnQ-5.50) + 0.093*(lnQ-5.50)2

 - 0.061*(T-2005.97) 

- 0.062*sin SS - 0.081*cos SS

.169 96.0

Beaty Creek near Jay, Okla. 

(07191222)

144 ln(L) = 1.31 + 1.30*ln(Q-2.80) + 0.059*ln(Q-2.80)2

 + 0.018*(T-2005.99) 

- 0.178*sin SS - 0.075*cos SS

.149 98.4

1

 The seasonality parameter (SS) is computed as 2*π*dectime.

2

 Estimated residual variance is the variance corrected for the number of observations and number of parameters in the regression model.
Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin 15

squared T term; whereas, this term was included in the phosphorus S-LOADEST equations reported previously. 

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 for the entire sampling 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. 

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 2). 

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 in Undeveloped Basins

Flow-weighted nitrogen and phosphorus concentrations 

were compared among stations in the Eucha-Spavinaw Basin. 

Flow-weighted concentrations also were 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. These 

streams were selected from three programs of the USGS—

the Hydrologic Benchmark Network (Cobb and Biesecker, 

1971; Mast and Turk, 1999), the National Water-Quality 

Assessment program (Gilliom and others, 1995, 2001), and 

the USGS National Research Program (Clark and others, 

2000). 

The USGS National Research Program provided research 

data for the assessment of flow-weighted total nitrogen and 

phosphorus concentrations 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).

Nutrient Concentrations, Loads, and 

Yields in the Eucha-Spavinaw Basin

Nitrogen and phosphorus in the Eucha-Spavinaw Basin 

are described in terms of mean concentrations, loads, and 

yields from 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 the remainder of 

this report. 

Concentrations

The summary statistics of nitrogen and phosphorus 

concentrations in water samples for the entire analysis period 

by season, divided into base-flow and runoff samples, are 

presented in tables 6 and 7. Results from the Mann-Whitney 

test of constituent concentrations in base-flow and runoff 

samples are presented in table 8. Boxplots showing comparisons of concentrations among stations for base-flow and 

runoff samples as a result of the Kruskal-Wallis test are shown 

in figure 5. Boxplots showing comparisons of concentrations 

among seasons for base flow and runoff samples as a result of 

the Kruskal-Wallis test are presented in figures 6 and 7. Base 

flow or runoff distributions with the same letter are not significantly different (p less than or equal 0.05) as a result of the 

Kruskal-Wallis test on distributions for each station (figs. 5–7). 

Two letters indicate the distribution was not different from 

more than one data set (fig. 5). Graphs showing the nutrient 

concentrations in base-flow and runoff samples are presented 

in figures 8 and 9.

The Mann-Whitney test was not performed to test statistical differences in constituent concentrations from base-flow 

and runoff samples for the summer, autumn, and winter seasons for nitrogen and the autumn and winter seasons for phosphorus for the Sycamore station because less than 10 baseflow samples were collected for each constituent during these 

seasons (tables 6 and 7). The Kruskal-Wallis test also was not 

performed for testing statistical differences among seasonal 

concentrations in samples collected at this station because less 

than 10 samples were collected during the seasons previously 

listed. 

Nitrogen

Nitrogen concentrations were significantly different 

(p ≤ 0.05) between runoff samples and base-flow samples 

collected during the entire period from most stations except for 

samples collected at the Sycamore station (table 8). Boxplots 

indicate that nitrogen concentrations were greater in runoff 

samples than in base-flow samples (fig. 5–6) where concentrations were significantly different as a result of the Mann-Whitney test (table 8). Significant differences in nitrogen concentrations in base-flow and runoff samples were variable by 

season and station. Nitrogen concentrations were significantly 

greater in runoff samples than in base-flow samples collected 

during the summer, autumn, and winter 

seasons from the Maysville station and the Beaty Creek 

station. Nitrogen concentrations were significantly greater in 
16 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

-quality stations in the Eucha-Spavinaw Basin, Arkansas Distribution of (A) total nitrogen and (B) total phosphorus concentrations in water samples collected at water Figure 5.

and Oklahoma, 2002–09. 

0.01

3.0

1.0

0.1

1210

8

6

42

A.B.

Base flow

Base flow

EXPLANATION

(23) Number of samples

Outlier

Data value less thanor equal to 1.5 times the interquartile range 

75th percentile

Median

25th percentile

Data value greater thanor equal to 1.5 times the inter quartile range 

Interquartile

range

A B C D A

(68) (64)

(34)

(66)

(53)

A B C D E

(63)

(62)

(34)

(63)

(52)

Spavinaw Creek near 

Maysville, Arkansas

Spavinaw Creek near 

Cherokee City, Arkansas

Spavinaw Creek near 

Sycamore, Oklahoma

Spavinaw Creek near 

Colcord, Oklahoma

Beaty Creek near Jay, 

Oklahoma

Spavinaw Creek near 

Maysville, Arkansas

Spavinaw Creek near 

Cherokee City, Arkansas

Spavinaw Creek near 

Sycamore, Oklahoma

Spavinaw Creek near 

Colcord, Oklahoma

Beaty Creek near Jay, 

Oklahoma

TO TAL P H O S P H O R U S C O NC E NT R AT IO N, IN 

MIL L IG R AMS P E R L IT E R AS P H O S P H O R U S

TO TAL NIT R O G E N C O NC E NT R AT IO N, IN 

MIL L IG R AMS P E R L IT E R AS NIT R O G E N

Runoff

A

A B A C

B

(71)

(76)

(68) (86)

(93)

Runoff

A B B B C

(70)

(74)

(66) (92)

(85)

A

Base flow or runoff distributionswith the same letter are not significantly different(p less than or equal 0.05) as a result of a multi-stage KruskalWallis test on distributions for each station. Two letters indicate distribution was not different from more than one data set.0.5 milligram per liter nitrogen concentration0.037 milligram per liter phosphorus concentration[75th percentile of flow-weighted concentrations from relatively undeveloped basins of the United States (Clark and others, 2000)]
Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin 17

Figure 6. Distributions of seasonal total nitrogen concentrations in water samples collected at water-quality stations in the EuchaSpavinaw Basin, Arkansas and Oklahoma, 2002–09. 

Runoff Samples

(31)

(14)

(14)

(17)

A A A B

EXPLANATION

(25)

75th percentile

Median

25th percentile

Outlier

Number of samples

Interquartile

range

Base-flow Samples Runof f Samples

Base-flow Samples

Base-flow Samples Runof f Samples Base-flow Samples Runof f Samples

Spavinaw Creek near Maysville, Arkansas

Spavinaw Creek near Cherokee City, Arkansas

Spavinaw Creek near Colcord, Oklahoma Beaty Creek near Jay, Oklahoma

(15)

(18) (19)

(16)

(15)

(18) (17)

(14)

(19) (18)

(14)

(15)

A B B A

A B C A

A B B A

TO TA L NIT R O G E N C O NC E NT R AT IO N, IN MIL L IG R A MS P E R L IT E R A S NIT R O G E N

o

(29)

(13) (14)

(15)

A A A B

(34)

(16)

(18)

(18)

A A A B

x

(36) (20)

(17)

(20)

A B A C

(13) (17)

(11) (12)

A B B A

B

A Base flow or runoff 

distributions with the 

same letter are not 

significantly different (p

less than or equal 0.05) 

as a result of a multistage Kruskal-Wallis test

on distributions for each 

season. Two letters 

indicate distribution was 

not different from more 

than one data set.

0.50 milligram per liter 

nitrogen concentration

[75th percentile of flowweighted concentrations 

from relatively undeveloped 

basins of the United States 

(Clark and others, 2000)]

12

10

8

6

4

2

0

12

10

8

6

4

2

0

12

10

8

6

4

2

0

 Spring Samples

 Summer Samples

 Autumn Samples

 Winter Samples

 Spring Samples

 Summer Samples

 Autumn Samples

 Winter Samples

 Spring Samples

 Summer Samples

 Autumn Samples

 Winter Samples

 Spring Samples

 Summer Samples

 Autumn Samples

 Winter Samples

Data value greater than

the interquartile range

or equal to 1.5 times

Data value less than

or equal to 1.5 times 

the interuartile range
18 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

Figure 7. Distributions of seasonal total phosphorus concentrations in water samples collected at water-quality stations in the EuchaSpavinaw Basin, Arkansas and Oklahoma, 2002–09. 

Runof f Samples (14)

(29) (13) (14)

A A A A

Base-flow Samples

0.01

(13)

(18) (16)

(16)

(15) (18)

(15) (14)

Base-flow Samples

0.01

0.01

0.1

1.0

3.0

A B B A

A A A A A A A A

EXPLANATION

(13)

75th percentile

Median

25th percentile

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

0.1

1.0

3.0

0.1

1.0

3.0

Runof f Samples

o

(30)

(15) (13) (16)

Base-flow Samples Runof f Samples

0.01

0.1

1.0

3.0

o

(15) (19)

(15)

(14)

(33) (17)

(18) (17)

A A A A A A A A

Base-flow Samples

(10) (15)

(15)

(12)

A A A A

Runof f Samples

(36) (20) (17)

(19)

A A A A

A Base flow or runoff 

distributions with the 

same letter are not 

significantly different (p

less than or equal 0.05) 

as a result of a multistage Kruskal-Wallis test 

on distributions for each 

season. Two letters 

indicate distribution was 

not different from more 

than one data set.

0..37 milligram per liter 

phosphorus concentration

[75th percentile of flowweighted concentrations 

from relatively undeveloped 

basins of the United States 

(Clark and others, 2000)]

TO TA L P H O S P H O R U S C O NC E NT R AT IO N, IN MIL L IG R A MS P E R L IT E R A S P H O S P H O R U S

Spavinaw Creek near Maysville, Arkansas

Spavinaw Creek near Cherokee City, Arkansas

Spavinaw Creek near Colcord, Oklahoma Beaty Creek near Jay, Oklahoma

 Spring Samples

 Summer Samples

 Autumn Samples

 Winter Samples

 Spring Samples

 Summer Samples

 Autumn Samples

 Winter Samples

 Spring Samples

 Summer Samples

 Autumn Samples

 Winter Samples

 Spring Samples

 Summer Samples

 Autumn Samples

 Winter Samples
Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin 19

Figure 8. Total nitrogen concentrations in base-flow and runoff water samples collected at water-quality stations in the EuchaSpavinaw Basin, Arkansas and Oklahoma, 2002–09. TO TAL NITR O G E N C O NC E NTR ATIO N, IN MIL L IG R AMS P E R L ITE R AS NITR O G E N

STREAMFLOW, IN CUBIC FEET PER SECOND

STREAMFLOW, IN CUBIC FEET PER SECOND

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

0

2

4

6

8

10

12

Spavinaw Creek near

Maysville, Arkansas 

Spavinaw Creek near

Cherokee City, Arkansas

Spavinaw Creek near

Sycamore, Oklahoma

1.0 10 100 1,000 10,000

Spavinaw Creek near

Colcord, Oklahoma

0

2

4

6

8

10

12

0.01 0.1 1.0 10 100 1,000 10,000

Beaty Creek near

Jay , Oklahoma

0

2

4

6

8

10

12

Winter Samples

Summer Samples

Spring Samples

Autumn Samples

Winter Samples

Summer Samples

Spring Samples

Autumn Samples

1.0 10 100 1,000 10,000
20 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

Figure 9. Total phosphorus concentrations in base-flow and runoff water samples collected at water-quality stations in the EuchaSpavinaw Basin, Arkansas and Oklahoma, 2002–09. 

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 nitrogen

concentrations from relatively undeveloped basins

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

Base-flow phosphorus concentration

Runoff phosphorus concentration

Winter Samples

Summer Samples

Spring Samples

Autumn Samples

Winter Samples

Summer Samples

Spring Samples

Autumn Samples

Spavinaw Creek near

Sycamore, Oklahoma

Beaty Creek near

Jay , Oklahoma

0.01

0.1

1

2

0.01

0.1

1

2

0.01

0.1

1

2

TO TA L P H O S P H O R U S C O NC E NT R AT IO N, IN MIL L IG R A MS P E R L IT E R A S P H O S P H O R U S

Spavinaw Creek near

Maysville, Arkansas 

Spavinaw Creek near

Cherokee City, Arkansas 

Spavinaw Creek near

Colcord, Oklahoma

1.0 10 100 1,000 10,000

0.01 0.1 1.0 10 100 1,000 10,000

1.0 10 100 1,000 10,000
Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin 21

runoff samples than in base-flow samples collected only during the winter season from the Cherokee City station. Nitrogen 

concentrations were significantly greater in runoff samples 

than in base-flow samples collected during the summer and 

winter seasons from the Colcord station. No significant difference in nitrogen concentrations was detected between baseflow and runoff samples collected during the spring season 

from any station.

Nitrogen concentrations in base-flow samples often were 

significantly greater (p ≤ 0.05) in samples collected during 

winter and spring than during summer or autumn seasons. An 

exception was observed for the Beaty Creek station in which 

the Kruskal-Wallis test indicated that concentrations in winter 

base-flow samples were similar to other seasons (fig. 6). 

Possible explanations for greater nitrogen concentrations in 

base-flow samples collected during spring and winter than in 

other seasons may be caused by (1) a lesser uptake of nitrate 

or ammonium from terrestrial vegetation resulting in increased 

leaching of nitrate from groundwater, (2) lack of growth of 

aquatic vegetation that allows nitrogen to build up in the 

stream during these seasons compared to summer and autumn 

months, or (3) an increase in fertilizer applications in late 

winter or early spring, which contributes to greater ammonium 

and nitrate concentrations in groundwater. 

Nitrogen concentrations were significantly greater (p ≤

0.05) in runoff samples collected during winter than all other 

Table 6. 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, 2002–09.

[Obs, number of observations; mg/L, milligram per liter; N, nitrogen]

Station name

(number)

Time 

period

Base-flow concentrations Runoff concentrations

Obs

Minimum

Median Mean Maximum Obs

Minimum

Median Mean Maximum

(mg/L as N) (mg/L as N)

Spavinaw 

Creek near 

Maysville, 

Ark. 

(07191160)

All Seasons 68 1.98 3.36 3.50 6.00 71 0.69 4.16 4.32 9.34

Spring 15 2.60 4.20 3.98 5.40 29 .69 3.97 4.01 7.40

Summer 18 1.98 2.98 3.07 3.91 13 2.29 3.82 3.84 5.61

Autumn 19 2.39 2.85 3.12 4.30 14 2.71 4.18 4.10 5.43

Winter 16 2.73 3.95 3.97 6.00 15 3.40 5.57 5.54 9.34

Spavinaw 

Creek near 

Cherokee 

City, Ark. 

(07191179)

All Seasons 64 2.45 4.12 4.08 6.08 76 2.48 4.31 4.59 10.4

Spring 15 3.22 4.44 4.43 5.70 31 2.96 4.26 4.36 6.82

Summer 18 2.45 3.39 3.44 4.48 14 2.48 4.01 3.86 5.04

Autumn 17 3.11 3.90 3.92 4.90 14 2.85 4.46 4.41 6.12

Winter 14 3.54 4.55 4.74 6.08 17 3.60 5.58 5.75 10.4

Spavinaw 

Creek near 

Sycamore, 

Okla. 

(07191220)

All Seasons 34 2.80 4.50 4.59 7.35 68 3.03 4.75 4.84 9.36

Spring 12 3.41 4.60 4.67 5.80 29 3.15 4.40 4.64 7.10

Summer 9 2.80 3.92 3.76 4.40 12 3.03 4.15 4.21 5.48

Autumn 4 4.21 4.40 4.40 4.60 10 3.58 4.58 4.52 5.50

Winter 9 4.60 5.36 5.41 7.35 17 3.20 5.70 5.81 9.36

Spavinaw 

Creek near 

Colcord, 

Okla. 

(071912213)

All Seasons 66 2.20 3.66 3.70 5.84 86 2.08 4.06 4.33 9.62

Spring 15 2.68 4.10 4.05 5.01 34 2.30 4.00 4.20 6.29

Summer 19 2.20 3.02 3.12 4.37 16 2.08 3.66 3.83 8.11

Autumn 18 2.82 3.19 3.49 4.50 18 2.70 3.80 3.94 5.29

Winter 14 3.21 4.20 4.40 5.84 18 3.80 5.03 5.41 9.62

Beaty Creek 

near Jay, 

Okla. 

(07191222)

All Seasons 53 .67 1.84 2.07 4.10 93 1.13 2.93 3.02 7.27

Spring 11 1.04 3.00 2.64 4.10 36 1.16 2.97 3.08 7.27

Summer 13 .89 1.85 1.94 2.80 20 1.70 2.52 2.58 5.12

Autumn 17 .67 1.16 1.58 3.40 17 1.13 2.83 2.59 4.24

Winter 12 1.18 2.03 2.40 4.07 20 2.50 3.68 3.70 5.00
22 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

seasons at all four stations tested (fig. 6). Possible explanations 

for greater nitrogen concentrations in runoff samples collected 

during winter than in other seasons may be a greater amount 

of organic nitrogen or ammonium available for runoff in leaflitter during the previous season or less dilution of nitrate from 

groundwater because low flow generally is reduced during 

winter months compared to other seasons (fig. 3). Investigation into the variability or loading of various forms of total 

nitrogen was beyond the scope of this report but would help 

in evaluation of possible causes for temporal and flow-related 

variability of nitrogen concentrations.

Nitrogen concentrations in base-flow samples significantly increased (p ≤ 0.05) downstream from the Maysville 

station to the Sycamore station (fig. 5). Nitrogen concentrations in base-flow samples collected from Spavinaw Creek 

significantly decreased (p ≤ 0.05) in a downstream direction 

from the Sycamore station to the Colcord station (fig. 5). 

Nitrogen concentrations in base-flow samples from stations in 

the Eucha-Spavinaw Basin generally increased with increasing streamflow (fig. 8). Nitrate can be more prone to leach into 

groundwater from soils and subsoils than phosphorus (Cooke 

and Williams, 1970). As base flow increased by addition 

Table 7. 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, 2002–09.

[Obs, number of observations; mg/L, milligram per liter; P, phosphorus]

Station name 

(number)

Time 

period

Base-flow concentrations Runoff concentrations

Obs

Minimum

Median Mean Maximum Obs

Minimum

Median Mean Maximum

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

Spavinaw 

Creek near 

Maysville, 

Ark. 

(07191160)

All Seasons 63 0.02 0.03 0.03 0.12 70 0.02 0.05 0.17 1.2

Spring 13 .02 .03 .03 .04 29 .03 .05 .17 .94

Summer 18 .02 .03 .03 .07 13 .02 .04 .13 .92

Autumn 16 .02 .03 .03 .06 14 .02 .05 .15 .90

Winter 16 .02 .02 .03 .12 14 .02 .05 .21 1.2

Spavinaw 

Creek near 

Cherokee 

City, Ark. 

(07191179)

All Seasons 62 .06 .14 .15 .32 74 .03 .14 .23 1.6

Spring 15 .06 .11 .13 .23 30 .03 .15 .23 1.6

Summer 18 .08 .15 .15 .23 15 .03 .14 .21 1.3

Autumn 15 .07 .16 .18 .32 13 .09 .12 .21 1.1

Winter 14 .07 .13 .15 .30 16 .07 .13 .24 1.2

Spavinaw 

Creek near 

Sycamore, 

Okla. 

(07191220)

All Seasons 34 .02 .10 .11 .18 66 .07 .13 .21 1.2

Spring 11 .08 .11 .11 .15 29 .07 .14 .22 .98

Summer 10 .08 .11 .11 .15 11 .08 .11 .18 .98

Autumn 4 .08 .08 .09 .12 10 .08 .12 .14 .24

Winter 9 .02 .09 .10 .18 16 .07 .11 .24 1.2

Spavinaw 

Creek near 

Colcord, 

Okla. 

(071912213)

All Seasons 63 .04 .08 .09 .26 85 .06 .12 .24 1.6

Spring 15 .04 .08 .09 .13 33 .06 .13 .26 1.6

Summer 19 .06 .08 .09 .15 17 .07 .10 .23 1.5

Autumn 15 .07 .08 .08 .11 18 .07 .12 .18 .83

Winter 14 .07 .08 .10 .26 17 .06 .11 .25 1.1

Beaty Creek 

near Jay, 

Okla. 

(07191222)

All Seasons 52 .02 .04 .05 .10 92 .02 .07 .18 1.1

Spring 10 .03 .04 .04 .07 36 .02 .09 .19 1.1

Summer 15 .03 .05 .05 .09 20 .04 .07 .13 .89

Autumn 15 .03 .05 .05 .07 17 .03 .10 .26 1.0

Winter 12 .02 .04 .04 .10 19 .03 .08 .15 .58
Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin 23

of groundwater, additional nitrate in the groundwater may 

increase the concentration of nitrogen in the stream. Spavinaw 

Creek received substantial nitrogen concentrations from the 

Decatur wastewater-treatment plant, but Beaty Creek did not. 

This difference may be a cause of lesser nitrogen concentrations in base-flow samples collected from the Beaty Creek 

station compared to the Spavinaw Creek stations (fig. 5).

Nitrogen concentrations in runoff samples collected 

from Spavinaw Creek were significantly greater for the 

Sycamore station compared to the upstream Maysville station 

but significantly decreased from the Sycamore station to the 

downstream Colcord station (fig. 5). Nitrogen concentrations 

in runoff samples collected from the Beaty Creek station were 

significantly less than at all other stations (fig. 5). Nitrogen 

concentrations in runoff samples collected from all stations 

generally increased with increasing streamflow (fig. 8). The 

larger concentrations of nitrogen during runoff likely indicate 

addition of nitrogen from nonpoint sources. 

Phosphorus

Phosphorus concentrations were significantly different 

(p ≤ 0.05) between runoff samples and base-flow samples for 

most stations for the entire period or for individual seasons 

or both (table 8). Boxplots indicate that nitrogen concentrations were greater in runoff samples than in base-flow samples 

Table 8. Mann-Whitney rank-sum test results comparing base-flow total nitrogen or total phosphorus concentrations to runoff total 

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

2002–09.

[z-score, normal test statistic with correction for ties; p-value, probability value; 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); <, less than]

Station name 

(number) Time period Nitrogen Phosphorus

z-score p-value z-score p-value

Spavinaw Creek near 

Maysville, Ark. 

(07191160)

All Seasons -4.473 <0.0001 -6.287 <0.0001

Spring .0867 .9309 -4.233 <.0001

Summer -2.943 .0032 -2.565 .0103

Autumn -3.391 .0007 -2.644 .0082

Winter -3.223 .0013 -2.623 .0087

Spavinaw Creek near 

Cherokee City, Ark. 

(07191179)

All Seasons -2.284 .0224 -.3256 .7447

Spring .6327 .5269 -1.313 .1892

Summer -1.862 .0626 .9767 .3287

Autumn -1.747 .0806 .2536 .7998

Winter -2.164 .0304 .0208 .9834

Spavinaw Creek near 

Sycamore, Okla. 

(07191220)

All Seasons -.6177 .5368 -2.58 .0099

Spring .5015 .616 -2.016 .0438

Summer NA1 NA1 .3174 .7509

Autumn NA1 NA1 NA1 NA1

Winter NA1 NA1 NA1 NA1

Spavinaw Creek near 

Colcord, Okla. 

(071912213)

All Seasons -3.047 .0023 -5.141 <.0001

Spring .0326 .974 -2.904 .0037

Summer -2.054 .04 -2.219 .0265

Autumn -1.788 .0738 -2.515 .0119

Winter -2.185 .0289 -1.707 .0878

Beaty Creek near Jay, 

Okla. (07191222)

All Seasons -5.031 <.0001 -6.165 <.0001

Spring -.8421 .3997 -2.73 .0063

Summer -2.415 .0157 -2.785 .0054

Autumn -3.083 .002 -3.458 .0005

Winter -2.843 .0045 -3.469 .0005

1

 The Mann-Whitney rank-sum test was not performed because there were less than 10 base-flow samples available for this season.
24 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

(figs. 5 and 7) where concentrations were significantly different as a result of the Mann-Whitney test (table 8). However, 

no significant difference in phosphorus concentrations were 

detected between base-flow and runoff samples collected from 

the Cherokee City station during the entire period or during 

any season (table 8). Phosphorus concentrations also were not 

significantly different between base-flow and runoff samples 

collected from the Sycamore station during the summer season 

and collected from the Colcord station during the winter 

season (table 8). Phosphorus concentrations were significantly 

different between base-flow and runoff samples collected 

from the Maysville station and the Beaty Creek station for all 

seasons. 

Phosphorus concentrations in base-flow samples were 

generally not significantly different (p ≤ 0.05) between seasons (fig. 7). An exception was observed for the Maysville station in which the multistage Kruskal-Wallis test indicated that 

phosphorus concentrations in samples collected during summer and autumn were significantly greater than concentrations 

in samples collected during spring and winter as indicated in 

figure 7. Possible explanations for greater phosphorus concentrations in base-flow samples collected from the Maysville 

station during summer and autumn than during other seasons 

may be caused by an increased concentration in dissolved 

phosphorus related to variability in seasonal agricultural activities, nutrient cycling from more frequent and abundant algal 

blooms in the spring and summer, or increased mobility of 

inorganic phosphates as a product of soil decomposition that 

can increase with warmer temperatures. Differences in phosphorus concentrations from samples among seasons may not 

be observed for other Spavinaw Creek stations because those 

stations, unlike the Maysville station, are downstream from the 

Decatur wastewater-treatment plant. The plant is a source of 

dissolved phosphorus to Spavinaw Creek (Haggard and others, 

2001) and may not be subject to substantial seasonal variability in waste discharge. Phosphorus concentrations in runoff 

samples were not significantly different among seasons for any 

station (fig. 7). Investigation into the variability or loading of 

dissolved (inorganic phosphates and total dissolved phosphorus) and sediment-sorbed phosphorus was beyond the scope of 

this report but would help in evaluation of possible causes for 

temporal variability of total phosphorus concentrations.

Phosphorus concentrations in base-flow samples collected from Spavinaw Creek significantly increased (p ≤

0.05) from the Maysville station to the Cherokee City station 

perhaps because of discharges from the Decatur wastewatertreatment plant between the two stations (fig. 5). Phosphorus 

concentrations in base-flow samples collected from Spavinaw 

Creek significantly decreased (p ≤ 0.05) from the Cherokee 

City station to the Colcord station (fig. 7). In Spavinaw Creek, 

phosphorus concentrations in base-flow samples collected 

from the Maysville station, Sycamore station, and Colcord 

station generally did not change with increasing streamflow; 

whereas, phosphorus concentrations in base-flow samples for 

the Cherokee City station generally decreased with increasing streamflow (fig. 9). Localized increases in phosphorus 

concentrations near point-sources have been reported for 

other point-source affected streams in the region (Haggard, 

2000; Haggard and others, 2001; Tortorelli and Pickup, 2006). 

As base flow increased by addition of groundwater, dilution 

likely reduced the concentration of dissolved phosphorus from 

the Decatur wastewater-treatment plant upstream from the 

Cherokee City station. Phosphorus concentrations were lesser 

in base-flow and runoff samples collected from the Beaty 

Creek station than from the Spavinaw Creek stations downstream from the Maysville station (fig. 5). This difference may 

be caused by the wastewater discharge that affects Spavinaw 

Creek.

Phosphorus concentrations in runoff samples were not 

significantly different among the three downstream stations on 

Spavinaw Creek but were significantly different between the 

Maysville station and the Beaty Creek station (fig. 5). Phosphorus concentrations in runoff samples collected from all stations generally increased with increasing streamflow (fig. 9). 

Larger concentrations of phosphorus present in streams during 

runoff than during base flow are likely caused by 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 9–10 and figures 10–11.

Nitrogen

Estimated mean annual nitrogen total loads (the sum 

of base flow and runoff loads) were substantially greater at 

Spavinaw Creek stations than at the Beaty Creek station (about 

two to four times), primarily because of greater streamflow 

and possibly because of greater nitrogen concentrations in 

samples collected at the Spavinaw Creek stations (tables 2 and 

9, fig. 8). Annual total loads increased in Spavinaw Creek in 

a downstream direction from the Maysville station to the Colcord station with the annual total load at the Colcord station 

about twice that of the Maysville station (table 9). 

Mean annual base-flow loads at the Spavinaw Creek 

stations were about five to nine times greater than base-flow 

loads at the Beaty Creek station (table 9). Annual nitrogen 

base-flow loads increased in Spavinaw Creek in a downstream 

direction from the Maysville station to the Colcord station 

with the annual base-flow load at the Colcord station almost 

twice that of the Maysville station (table 9).

Estimated mean annual nitrogen runoff loads in the basin 

increased with increasing drainage area and with increasing 

streamflow (tables 2 and 9). The runoff component of the 
Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin 25

mean annual nitrogen load for Beaty Creek was 88 percent 

(table 9). The range in the runoff component of the mean 

annual nitrogen load at the Spavinaw Creek stations was 67 

to 73 percent and increased with increasing drainage area 

(tables 2 and 9). Runoff was indicated no more than 34 percent 

of the time for any station (table 11), but accounted for most of 

the annual nitrogen total load for every station. The fraction of 

load delivered during runoff on all stations also exceeded the 

fraction of total flow that is runoff for every station (table 3).

Annual nitrogen total, base-flow, and runoff loads were 

the greatest during the calendar year 2008 and lowest during 

the calendar year 2006 for all stations (fig. 10). Increases and 

decreases in annual nitrogen load correspond strongly 

to increases and decreases in mean annual streamflow 

(fig. 10). This strong correspondence is likely because of the 

importance of the streamflow in transport of nitrogen and is 

expressed by the dominance of streamflow terms in estimating daily mean nitrogen load from the S-LOADEST equations 

(table 4). 

Phosphorus

Estimated mean annual phosphorus total loads were substantially greater in Spavinaw Creek from the Cherokee City 

station to the Colcord station than at the Beaty Creek station, 

possibly because of greater streamflow and greater phosphorus 

0

500,000

1,000,000

1,500,000

2,000,000

2,500,000

3,000,000

3,500,000

2002 2003 2004 2005 2006 2007 2008 2009

500,000

1,000,000

1,500,000

2,000,000

2,500,000

3,000,000

3,500,000

EXPLANATION

Total nitrogen annual load from runoff

Total nitrogen annual load from base flow

Mean annual streamflow

0

500,000

1,000,000

1,500,000

2,000,000

2,500,000

3,000,000

3,500,000

Spavinaw Creek near Maysville, Arkansas Spavinaw Creek near Cherokee City, Arkansas 

Spavinaw Creek near Sycamore, Oklahoma Spavinaw Creek near Colcord, 

Oklahoma

Beaty Creek near Jay, Oklahoma

2002 2003 2004 2005 2006 2007 2008 2009

YEAR

YEAR

TO TAL NIT R O G E N ANNU AL L O AD , IN P O U ND S AS NIT R O G E N

ME AN ANNU AL S T R E AMF L O W, IN C U BIC F E E T P E R S E C O ND

2002 2003 2004 2005 2006 2007 2008 2009

0

400

350

300

250

200

150

100

50

0

400

350

300

250

200

150

100

50

0

400

350

300

250

200

150

100

50

0

Figure 10. Total nitrogen annual total load, separated by annual load from base flow and annual load from runoff, and mean annual 

streamflow, at water-quality stations in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09.
26 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

concentrations at those stations (tables 2, figs. 9 and 10). 

Mean annual phosphorus total loads were greater at the Beaty 

Creek station than at the Maysville station on Spavinaw Creek 

(table 10) even though annual mean streamflow was greater at 

the Maysville station (table 2). This observation indicated that 

the difference was likely because of greater phosphorus concentrations at the Beaty Creek station than the Maysville station (fig. 5). Mean annual phosphorus total loads increased in 

a downstream direction in Spavinaw Creek (table 10) from the 

Maysville station to the Colcord station; the annual total load 

at the Colcord station was about three times that of Maysville 

station (table 10). 

Estimated mean annual phosphorus base-flow loads were 

substantially less in Beaty Creek than in Spavinaw Creek 

(table 10). Mean annual phosphorus base-flow loads at the 

Spavinaw Creek stations were about two to nine times greater 

than base-flow loads at the Beaty Creek station. Mean annual 

phosphorus base-flow loads increased substantially in Spavinaw Creek from the Maysville station to the Cherokee City 

station. This increase was observed perhaps because of inflows 

from discharges from the Decatur wastewater-treatment plant; 

the mean annual base-flow load at the Cherokee City station 

was about four times that of Maysville station (table 10). The 

mean annual base-flow loads at the three downstream stations 

on Spavinaw Creek from the Cherokee City station to the 

Colcord station were similar (table 10).

Estimated mean annual phosphorus runoff loads in the 

basin increased with increasing drainage area in Spavinaw 

Figure 11. Total phosphorus total annual load, separated by annual load from base flow and annual load from runoff, and mean annual 

streamflow, at water-quality stations in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09. 

0

50

100

150

200

250

300

350

400

0

50

100

150

200

250

300

350

400

0

50

100

150

200

250

300

350

400

EXPLANATION

Total phosphorus annual load from runoff

Total phosphorus annual load from base flow

Mean annual streamflow

Spavinaw Creek near Maysville, Arkansas Spavinaw Creek near Cherokee City, Arkansas

Spavinaw Creek near Sycamore, Oklahoma Spavinaw Creek near Colcord, 

Oklahoma

Beaty Creek near Jay, Oklahoma

2002 2003 2004 2005 2006 2007 2008 2009

YEAR

YEAR

TO TAL P H O S P H O R U S ANNU AL L O AD , IN P O U ND S AS NIT R O G E N

ME AN ANNU AL S T R E AMF L O W, IN C U BIC F E E T P E R S E C O ND

250,000

0

200,000

150,000

100,000

 50,000

250,000

0

200,000

150,000

100,000

 50,000

250,000

0

200,000

150,000

100,000

 50,000

275,000

275,000

275,000

2002 2003 2004 2005 2006 2007 2008 2009

Total annual loads less than 1,000 pounds are not 

depicted in this figure.
Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin 27

Creek (tables 2 and 10). The range in the runoff component 

of the mean annual phosphorus total load for the Spavinaw 

Creek stations was 79 to 93 percent (table 10). The mean 

annual phosphorus load contributed by runoff at the three 

downstream Spavinaw Creek stations generally increased from 

the Cherokee City station to the Colcord station (table 10). 

The runoff component of the mean annual phosphorus total 

load for Beaty Creek was 98 percent (table 10). Most of the 

phosphorus loads for Beaty Creek are delivered during runoff, 

and the mean annual runoff load for Beaty Creek was larger 

than either of the runoff loads of the two upper Spavinaw 

Creek stations (table 10). Runoff was indicated no more than 

34 percent of the time for any station (table 11), but accounted 

for most of the annual phosphorus total load for every station 

(table 10). The phosphorus load delivered during runoff for all 

stations also substantially exceeded the fraction of total flow 

that is runoff for every station (table 3). The percentage of 

the estimated mean annual phosphorus load delivered during 

runoff at each station ranged from 9 to 25 percent higher than 

the percentage of the estimated mean annual nitrogen load 

delivered during runoff for the same station (tables 9 and 10), 

that indicates that phosphorus delivery is likely more runoffdriven than nitrogen delivery in the Eucha-Spavinaw Basin. 

Greater phosphorus delivery and loading during runoff may 

be because the main source of phosphorus loading was likely 

from phosphorus-sorption to sediment, which was delivered 

to the stream during runoff by overland erosion, resuspension 

of phosphorus from the streambed, or streambank erosion. 

However, a substantial source of nitrogen loading may be from 

nitrate delivered to the stream primarily from groundwater. 

Similar to annual nitrogen loads, estimated annual 

phosphorus total, base-flow and runoff loads were the greatest 

during the calendar year 2008 and least during the calendar 

year 2006 for all stations (fig. 11). Increases and decreases 

in annual phosphorus loads generally correspond strongly to 

increases and decreases in annual mean streamflow (fig. 11). 

Table 9. 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, for the period 2002–09.

[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 because of rounding.]

Station name 

(number)

Drainage 

area 

(mi2

)

Estimated mean annual Load 

delivered 

during 

runoff 

(percent)

Total load1

(+/- SEP2

) 

(lb/yr as N)

Total yield 

(lb/yr/mi2

as N)

Base-flow 

load3

(lb/yr as N)

Base-flow 

yield 

(lb/yr/mi2

as N)

Runoff load4

(lb/yr as N)

Runoff yield 

(lb/yr/mi2

as N)

Spavinaw Creek 

near Maysville, 

Ark. (07191160)

88.2 604,800

(16,400)

6,850 197,000 2,230 407,800 4,620 67

Spavinaw Creek 

near 

Cherokee City, 

Ark. (07191179)

104 804,000 

(15,600)

7,730 260,000 2,500 543,900 5,230 68

Spavinaw Creek 

near Sycamore, 

Okla. (07191220)

133 1,041,000 

(19,000)

7,830 301,600 2,270 739,200 5,560 71

Spavinaw Creek 

near 

Colcord, Okla. 

(071912213)

163 1,316,000 

(27,600)

8,070 360,900 2,210 955,300 5,860 73

Beaty Creek 

near Jay, Okla. 

(07191222)

59.2 364,800 

(17,900)

6,160 42,100 710 322,700 5,450 88

1

 The mean of annual total load (base flow and runoff) for the study period.

2

 Calculated by S-LOADEST and are statistics of all data.

3

 Means of the base-flow loads are calculated from base-flow days data only.

4

 Means of the runoff loads are calculated from runoff days data only.
28 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

Like nitrogen loads, this strong correspondence was likely 

because of the importance of the streamflow in transport of 

phosphorus and is expressed by the dominance of streamflow terms in estimating daily mean nitrogen load from the 

S-LOADEST equations (table 5).

Estimated Mean Seasonal Loads

Estimated mean seasonal nitrogen and phosphorus 

loads are discussed in this section. Estimated mean seasonal 

loads are subdivided into base-flow and runoff components 

(tables 12 and 13).

Nitrogen

Estimated mean seasonal nitrogen base-flow loads generally were least in summer or autumn and greatest in spring at 

all stations in the Eucha-Spavinaw Basin. Seasonal base-flow 

loads generally corresponded with mean seasonal streamflow, 

whereby, mean streamflow also was least in autumn and greatest in spring at all stations (fig. 4). The mean seasonal baseflow loads indicated the same pattern as the annual base-flow 

loads (tables 9 and 12) in terms of variability among stations. 

Mean seasonal base-flow loads for the Spavinaw Creek stations were about 4 to 11 times greater than seasonal base-flow 

loads at the Beaty Creek station (table 12). Mean seasonal 

nitrogen base-flow loads increased in a downstream direction 

in Spavinaw Creek from the Maysville station to the Colcord 

station; the seasonal base-flow load at the Colcord station was 

about twice that at the Maysville station for any given season 

(table 12).

Estimated mean seasonal nitrogen runoff loads were 

least in summer and greatest in spring at all stations for the 

study period (table 12). In general, seasonal runoff loads corresponded to seasonal streamflow for spring and winter but 

Table 10. 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, 2002–09.

[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 because of rounding.]

Station name 

(number)

Drainage 

area 

(mi2

)

Estimated mean annual Runoff 

yield 

(lb/yr/mi2

as P)

Load 

delivered 

during 

runoff 

(percent)

Total load1 

(+/- SEP2) 

(lb/yr as P)

Total yield 

(lb/yr/mi2

 as P)

Base-flow 

load3

(lb/yr as P)

Base-flow 

yield 

(lb/yr/mi2

 as P)

Runoff 

load4

(lb/yr as P)

Spavinaw Creek 

near Maysville, 

Ark. (07191160)

88.2 26,700

(3,110)

300 1,990 20 24,700 280 93

Spavinaw Creek 

near Cherokee City, Ark. 

(07191179)

104 38,000 

(3,530)

370 8,130 80 29,800 290 79

Spavinaw Creek 

near Sycamore, Okla. 

(07191220)

133 44,900 

(3,960)

330 7,300 50 37,600 280 84

Spavinaw Creek 

near Colcord, Okla. 

(071912213)

163 72,000 

(8,390)

450 8,990 60 63,000 390 88

Beaty Creek 

near Jay, Okla. 

(07191222)

59.2 36,400 

(5,570)

620 900 20 35,500 600 98

1

 The mean of annual total load (base flow and runoff) for the study period.

2

 Calculated by S-LOADEST and are statistics of all data.

3

 Means of the base-flow loads are calculated from base-flow days data only.

4

 Means of the runoff loads are calculated from runoff days data only.
Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin 29

not summer and autumn. Summer runoff loads were slightly 

less than autumn runoff loads even though mean summer 

streamflow was slightly greater than mean autumn streamflow (fig. 4), indicating that differences in the loads between 

these seasons may be caused by differences in concentration 

rather than streamflow. Summer and autumn concentrations 

in runoff samples were similar at Spavinaw Creek stations 

(although autumn concentrations were greater than summer 

concentrations at the Beaty Creek station, fig. 6). Even though 

mean nitrogen concentrations in runoff samples were not 

significantly different (p ≤ 0.05) between summer and autumn 

seasons for stations on Spavinaw Creek, the upper end of the 

distribution in nitrogen concentrations in runoff samples was 

greater in autumn than in summer at Spavinaw Creek stations 

(fig. 6). These slight differences in seasonal concentrations 

may be the reason for the lesser summer loads compared to 

autumn loads. 

Estimated mean seasonal nitrogen runoff loads increased 

with increasing drainage area (tables 2 and 12) and with 

increasing streamflow (fig. 4) indicating the same pattern as 

annual runoff loads (table 9).

Phosphorus

Estimated mean seasonal phosphorus base-flow loads 

were greatest in spring for all stations, but minimum seasonal 

Table 11. Number of days of base flow and runoff designated by Base-Flow Index (BFI) program at water-quality stations in the EuchaSpavinaw Basin, Arkansas and Oklahoma, 2002–09.

[Spring is March through May, Summer is June through August, Autumn is September through November, and Winter is December through February]

Station name 

(number)

Seasons Total for all 

seasons during 

2002–09

Percent 

of runoff 

days for 

2002–09

Spring Summer Autumn Winter

Base 

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

Spavinaw Creek near Maysville, 

Ark. (07191160) 440 296 585 151 597 131 515 207 2,137 785 27

Spavinaw Creek near Cherokee 

City, Ark. (07191179) 437 299 575 161 575 153 499 223 2,086 836 29

Spavinaw Creek near Sycamore, 

Okla. (07191220) 425 311 574 162 568 160 472 250 2,039 883 30

Spavinaw Creek near Colcord, 

Okla. (071912213) 439 297 559 177 540 188 472 250 2,010 912 31

Beaty Creek near Jay, Okla. 

(07191222) 395 341 528 208 585 143 433 289 1,941 981 34

Table 12. 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, 

2002–09.

[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

Base flow Spavinaw Creek near Maysville, Ark. (07191160) 63,100 41,100 39,640 53,100

Spavinaw Creek near Cherokee City, Ark. (07191179) 85,800 52,700 53,300 68,400

Spavinaw Creek near Sycamore, Okla. (07191220) 102,300 65,900 58,600 74,800

Spavinaw Creek near Colcord, Okla. (071912213) 125,000 69,000 68,600 98,100

Beaty Creek near Jay, Okla. (07191222) 17,600 6,550 7,310 10,600

Runoff Spavinaw Creek near Maysville, Ark. (07191160) 196,000 52,550 64,400 110,500

Spavinaw Creek near Cherokee City, Ark. (07191179) 245,000 68,200 72,000 167,700

Spavinaw Creek near Sycamore, Okla. (07191220) 322,000 96,500 115,000 234,000

Spavinaw Creek near Colcord, Okla. (071912213) 422,000 125,000 141,000 284,000

Beaty Creek near Jay, Okla. (07191222) 132,000 48,200 60,600 96,800
30 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

base-flow loads varied among stations. Mean seasonal phosphorus base-flow loads were least in autumn at the Cherokee 

City, Sycamore, and Colcord stations on Spavinaw Creek, 

least in winter at Spavinaw Creek near Maysville, and least in 

summer at the Beaty Creek station (table 13). The variability 

of mean seasonal base-flow loads among stations had a similar 

pattern to the annual base-flow loads (tables 10 and 13). Mean 

seasonal phosphorus base-flow loads were substantially less 

in Beaty Creek than in the Spavinaw Creek stations (table 13). 

Mean seasonal base-flow loads at stations on Spavinaw Creek 

were about 2 to 13 times greater than base-flow loads at the 

station on Beaty Creek (table 13). Mean seasonal phosphorus 

base-flow loads in Spavinaw Creek increased substantially 

from the Maysville station to the Cherokee City station, perhaps because of the inflow of wastewater discharges from the 

Decatur wastewater-treatment plant; the mean seasonal loads 

at the Cherokee City station were about three and one-half to 

five times that at the Maysville station for any given season 

(table 13). The mean seasonal base-flow loads at the three 

downstream stations on Spavinaw Creek from Cherokee City 

to Colcord were similar (table 13). However, mean summer, 

mean autumn, and mean winter base-flow loads were greater 

at the Cherokee City station than at the Sycamore station 

on Spavinaw Creek. As base flow increased by addition of 

groundwater, dilution may have reduced the load of phosphorus from point sources. 

Similar to estimated mean seasonal phosphorus baseflow loads, estimated mean seasonal phosphorus runoff loads 

generally were least in autumn and greatest in spring at most 

stations. An exception was observed for the Beaty Creek station where mean runoff phosphorus loads were less in summer 

than in autumn (table 13). Seasonal phosphorus loads from 

runoff generally corresponded to seasonal streamflow. However, at Beaty Creek, mean summer streamflow was slightly 

greater than mean autumn streamflow (fig. 4) even though the 

mean summer phosphorus runoff load was less during summer 

than autumn. Even though mean phosphorus concentrations in 

runoff samples were not significantly different between summer and autumn seasons for the Beaty Creek station, the upper 

end of the distribution in phosphorus concentrations in runoff 

samples was greater in autumn than in summer (fig. 7). These 

slight differences in seasonal concentrations may be the reason 

for the lesser mean summer load compared to autumn load for 

the Beaty Creek station. 

Estimated mean seasonal phosphorus runoff loads in the 

basin generally increased with increasing drainage area and 

with increasing streamflow at the Spavinaw Creek stations 

(fig. 4 and table 13). Much of the phosphorus loads at the 

Beaty Creek station were delivered during runoff (table 10), 

and autumn and winter runoff phosphorus loads at the Beaty 

Creek station generally were larger than loads at some of the 

Spavinaw Creek stations (table 13).

Estimated Mean Annual Yields

Estimated mean annual nitrogen and phosphorus yields 

are discussed in this section. Total annual yields are divided 

into base-flow and runoff components.

Table 13. 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, 

2002–09.

[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

Base flow Spavinaw Creek near Maysville, Ark. (07191160) 660 519 408 403

Spavinaw Creek near Cherokee City, Ark. (07191179) 2,300 2,120 1,830 1,880

Spavinaw Creek near Sycamore, Okla. (07191220) 2,520 1,950 1,290 1,540

Spavinaw Creek near Colcord, Okla. (071912213) 3,200 2,220 1,600 1,960

Beaty Creek near Jay, Okla. (07191222) 368 170 180 180

Runoff Spavinaw Creek near Maysville, Ark. (07191160) 12,800 6,250 2,800 3,550

Spavinaw Creek near Cherokee City, Ark. (07191179) 13,500 7,200 2,400 6,990

Spavinaw Creek near Sycamore, Okla. (07191220) 18,000 8,780 3,520 8,110

Spavinaw Creek near Colcord, Okla. (071912213) 32,000 12,500 6,900 12,500

Beaty Creek near Jay, Okla. (07191222) 10,700 6,890 7,540 12,200
Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin 31

Nitrogen

Estimated mean annual nitrogen total yields generally 

increased slightly in a downstream direction in Spavinaw 

Creek (table 9). The estimated mean annual nitrogen total 

yields in Spavinaw Creek ranged from 6,850 to 8,070 pounds 

per year per square mile (lbs/yr/mi2

); the greatest yield was 

reported for the Colcord station, and the least yield was 

reported for the Maysville station (table 9). An even lesser 

yield was calculated for the Beaty Creek station (6,160 lbs/yr/

mi2

) than for the Maysville station. No substantial point source 

was contributing nitrogen to Spavinaw Creek at the Maysville 

station, therefore, a possible explanation for the difference 

between yields at these stations could be a greater application 

rate of fertilizer, notably from poultry litter, in the Spavinaw 

Basin (Storm and others, 2002).

Estimated mean annual nitrogen base-flow yields in 

Spavinaw Creek were similar between the Maysville, Sycamore, and Colcord stations (ranging from 2,210 to 2,270 

lbs/yr/mi2

), and slightly greater at the Cherokee City station 

(2,500 lbs/yr/mi2

). The mean base-flow yield at the Beaty 

Creek station (710 lbs/yr/mi2

) was about one-third of the mean 

base-flow yields of the Spavinaw Creek stations (table 9). Possible explanations for this difference in base-flow yield may be 

a greater influence of groundwater on streamflow and greater 

nitrogen base-flow concentrations at Spavinaw Creek (downstream from the Maysville station) than Beaty Creek (tables 

3 and 9), and, therefore, a greater percentage of nitrogen load 

delivered during base flow for Spavinaw Creek compared to 

Beaty Creek (table 9).

Estimated mean annual nitrogen runoff yields in Spavinaw Creek generally increased from the Maysville to the Colcord station, ranging from 4,620 to 5,860 lbs/yr/mi2

 (table 9). 

Unlike mean annual base-flow yields, Beaty Creek mean 

annual runoff yields were similar to runoff yields in Spavinaw 

Creek (5,450 lbs/yr/mi2

) (table 9).

Phosphorus

Estimated mean annual phosphorus total yields in 

Spavinaw Creek generally increased in a downstream direction, ranging from 300 to 450 lbs/yr/mi2

; the greatest yield 

was reported for the Colcord station, and the least yield was 

reported for the Maysville station (table 10). The mean total 

phosphorus yield for Beaty Creek (620 lbs/yr/mi2

) was greater 

than for any Spavinaw Creek station. 

Estimated mean annual phosphorus base-flow yield was 

substantially less in Beaty Creek (20 lbs/yr/mi2

)than in the 

three downstream Spavinaw Creek stations (50 to 80 lbs/yr/

mi2

) but was the same as the Maysville station (table 10). 

Mean annual phosphorus base-flow yield increased substantially in Spavinaw Creek from the Maysville station to the 

Cherokee City station (table 10); the mean annual base-flow 

yield at the Cherokee City station was four times that of the 

Maysville station (table 10). Mean annual phosphorus baseflow yields decreased slightly from the Cherokee City station 

to the Colcord station. This variability of base-flow yield 

among stations probably happened because of the inflow of 

wastewater discharges from the Decatur wastewater-treatment 

plant between the Maysville station and Cherokee City station 

and yields decreased downstream from the Cherokee City 

station by addition of groundwater, resulting in dilution of 

phosphorus from the point source. 

Estimated mean annual phosphorus runoff yields in 

Spavinaw Creek were similar at the Maysville station, the 

Cherokee City station, and the Sycamore station, ranging from 

280 to 290 lbs/yr/mi2

. Estimated mean annual phosphorus 

runoff yields increased slightly to 390 lbs/yr/mi2 at the Colcord 

station. The mean runoff yield for the Beaty Creek station 

(600 lbs/yr/mi2) was greater than runoff yields for any Spavinaw Creek station (table 11). 

The greater total and runoff phosphorus yield in Beaty 

Creek compared to Spavinaw Creek may be caused by a 

greater contribution of nonpoint sources of phosphorus in 

Beaty Creek, resuspension of phosphorus from the streambed, 

and streambank erosion. The greater runoff yield in Beaty 

Creek compared to Spavinaw Creek also may be caused by a 

lesser amount of groundwater contributions to streamflow and 

a greater percentage of phosphorus load delivered during runoff for Beaty Creek compared to Spavinaw Creek (table 10).

Although substantial differences in mean annual phosphorus runoff yield were detected between Beaty Creek and 

Spavinaw Creek, no substantial differences in estimated mean 

annual nitrogen runoff yield were detected between creeks. 

Because Beaty Creek is more runoff-driven than Spavinaw 

Creek, this observation further supports the concept that phosphorus delivery is more runoff-driven than nitrogen delivery in 

the Eucha-Spavinaw Basin.

Estimated Mean Flow-Weighted Concentrations

Nitrogen

Estimated mean flow-weighted nitrogen concentrations 

(mean nitrogen load divided by mean streamflow times a 

conversion factor) for stations in the basin ranged from 3.49 

to 4.94 mg/L as nitrogen (table 14, fig. 12). These concentrations were about 13 to 19 times greater than the median flowweighted concentration (0.26 mg/L) for stations in mostly 

undeveloped basins of the United States and were about 7 to 

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

nitrogen concentrations in undeveloped basins (0.50 mg/L, 

Clark and others, 2000) (fig. 12, table 14). 

Estimated mean flow-weighted nitrogen concentrations 

for each station in the basin were consistently greater than 

the median instantaneous nitrogen concentrations in samples 

collected from each station shown in figure 12. A varied 

range of total nitrogen concentrations were observed (table 6, 

appendixes 1–5). Greater nitrogen concentrations in samples 
32 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

-quality stations in ected at water Instantaneous and estimated mean flow-weighted (A) total nitrogen and (B) total phosphorus concentrations in water samples coll Figure 12.

he Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09. t

0.01

3.0

1.0

0.1

A.

B.

EXPLANATION

(23) Number of samples

Outlier

Data value less thanor equal to 1.5 times the interquartile range 

75th percentile

Median

25th percentile

Data value greater thanor equal to 1.5 times the interquartile range

Interquartile

range

1210

8

6

42

Spavinaw Creek near 

Maysville, Arkansas

Spavinaw Creek near 

herokee City, Arkansas

Spavinaw Creek near 

Sycamore, Oklahoma

Spavinaw Creek near 

Colcord, Oklahoma

Beaty Creek near Jay, 

Oklahoma

Estimated mean flowweighted concentration (tables 14 and 15)

75th percentile of flowweighted concentrations from relatively undeveloped basins of the United States (Clark and others, 2000)

0.5 milligram per liter nitrogen concentration0.037 milligram per liter phosphorus concentration

TO TAL P H O S P H O R U S C O NC E NT R AT IO N, IN 

MIL L IG R AMS P E R L IT E R AS P H O S P H O R U S

TO TAL NIT R O G E N C O NC E NT R AT IO N, IN 

MIL L IG R AMS P E R L IT E R AS NIT R O G E N

C
Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin 33

collected during runoff can greatly affect the computation 

of the mean flow-weighted concentrations. For example, the 

maximum concentration during 2005 at the Colcord station 

(9.62 mg/L, table 6, appendix 4) was collected during substantial runoff in January 2005 and contributed to a large nitrogen 

load (appendix 4). Because mean flow-weighted concentration 

is proportional to load, the result was a large estimated mean 

flow-weighted nitrogen concentration. 

Phosphorus

Estimated mean flow-weighted phosphorus concentrations at stations in the basin ranged from 0.19 to 0.35 mg/L 

as phosphorus (table 15). These concentrations were 9 to 

16 times greater than the median flow-weighted concentration (0.022 mg/L) in mostly undeveloped basins of the 

United States and were about 5 to 9 times greater than the 

75th percentile of flow-weighted phosphorus concentrations 

in undeveloped basins (0.037 mg/L, Clark and others, 2000; 

fig. 12, table 15). 

Similar to estimated mean flow-weighted nitrogen 

concentrations, estimated mean flow-weighted phosphorus 

concentrations at each station were consistently greater than 

the median instantaneous phosphorus concentrations shown 

in figure 12. The phosphorus data have a varied range (table 6, 

appendixes 1–5). High phosphorus concentrations in samples 

collected during runoff can greatly affect the computation 

of the mean flow-weighted concentrations. For example, 

the maximum concentration during May 2009 at the Beaty 

Creek station (1.1 mg/L, table 7, appendix 5) was collected 

during substantial runoff and contributed to a large phosphorus load. However, the greatest daily mean streamflow and 

load was during a January 2008 event (table 2) with a concentration of 0.58 mg/L (appendix 5) and was responsible for a 

large proportion of the mean annual load at the Beaty Creek 

station. 

Table 14. 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, 2002–09.

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

Station name (number)

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 Maysville, Ark. (07191160) 604,800 71.0 4.33

Spavinaw Creek near Cherokee City, Ark. (07191179) 804,000 86.9 4.70

Spavinaw Creek near Sycamore, Okla. (07191220) 1,041,000 107 4.94

Spavinaw Creek near Colcord, Okla. (071912213) 1,316,000 149 4.49

Beaty Creek near Jay, Okla. (07191222) 364,800 53.1 3.49

Table 15. Estimated mean annual total phosphorus loads, mean annual streamflows, and estimated mean flow-weighted total 

phosphorus concentrations at water-quality stations in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09.

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

Station name (number)

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 Maysville, Ark. (07191160) 26,700 71.0 0.19

Spavinaw Creek near Cherokee City, Ark. (07191179) 38,000 86.9 .22

Spavinaw Creek near Sycamore, Okla. (07191220) 44,900 107 .21

Spavinaw Creek near Colcord, Okla. (071912213) 72,000 149 .25

Beaty Creek near Jay, Okla. (07191222) 36,400 53.1 .35
34 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

Estimated Mean Annual Nutrient Loads into 

Lake Eucha

Much of the mean annual nutrient loads entering Lake 

Eucha can be estimated by adding the loads for the Beaty 

Creek station and the Colcord station on Spavinaw Creek. 

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 1,681,000 pounds per year 

(lbs/yr) (table 16) and 76 percent of the annual nitrogen 

total load was transported to Lake Eucha by runoff (fig. 13). 

Spavinaw Creek transported about nine times more nitrogen 

load during base flow and about three times more nitrogen 

load during runoff to the lake than did Beaty Creek (table 9). 

Spavinaw Creek and Beaty Creek contributed a mean 

annual phosphorus total load of 108,390 lbs/yr (table 16); 91 

percent of the mean annual phosphorus total load was transported to Lake Eucha by runoff (fig. 13). Spavinaw Creek 

transported about 10 times more phosphorus load during base 

flow and about 2 times more phosphorus load during runoff to 

the lake than did Beaty Creek (table 10). The ratio of nitrogen 

9%

91%

360,900 lbs/yr as N 

(90 %)

42,100 lbs/yr 

as N (10%)

403,000 

lbs/yr as N 

(24%)

75%

25%

Beaty Creek

Spavinaw Creek

Beaty Creek

Spavinaw Creek

Beaty Creek

Spavinaw Creek

Beaty Creek

Spavinaw Creek

955,300 lbs/yr as N 

(75%)

322,700 

lbs/yr as N 

(25%)

8,990 lbs/yr as P (91%)

900 lbs/yr 

as P (9%)

63,000 lbs/yr as P 

(64%)

35,500 lbs/yr as 

P (36%)

98,500 lbs/yr as P (91%)

9,890 lbs/yr 

as P (9%)

Base flow

Runoff

Base flow

Runoff

A.

B.

1,278,000 lbs/yr as N (76%)

Figure 13. Graph showing percentage of estimated mean annual (A) total nitrogen and (B) total phosphorus load to Lake Eucha, for 

the period 2002-09, that is from base flow and from runoff, and the percentage of load contributed from Beaty Creek near Jay, Oklahoma 

(USGS station identifier 07191222) and Spavinaw Creek near Colcord, Oklahoma (USGS station identifier 071912213). 
Summary 35

to phosphorus annual loads for the basin was about 15.5:1. 

The ratio of nitrogen to phosphorus base-flow load for the 

basin was about 41:1 but was reduced to about 13:1 for runoff 

load that indicated phosphorus loads were increased relative 

to nitrogen loads during runoff. The total ratio of the total 

nitrogen concentration to the total phosphorus concentration 

in samples collected from Spavinaw and Beaty Creeks generally were greater than 20 for most samples (appendixes 1–5), 

which may indicate phosphorus is a limiting nutrient for 

eutrophication in the basin. Because phosphorus was the 

limiting nutrient in Lake Eucha and Spavinaw Lake, delivery 

of increased total phosphorus compared to total nitrogen 

during runoff may increase the risk of algal blooms in the 

lakes. Total phosphorus likely is less bioavailable than total 

nitrogen in the basin because a large part of total phosphorus 

loads are bound to sediment, whereas a major component 

of total nitrogen are dissolved nitrates, but dissolved nitrogen components were not analyzed. Evaluation of the ratio 

of nitrogen to phosphorus loads for dissolved or bioavailable 

components would be a better indicator of eutrophication 

potential in the lake, but was beyond the scope of this 

report.

Annual nitrogen and phosphorus loads and the percentage of total load contributed during runoff computed by using 

data from 2002–09 were greater than the loads reported in 

Tortorelli (2008) that used data from 2002–06. The mean 

annual nitrogen total load reported in Tortorelli (2008) ranged 

from 1,350,000 to 1,490,000 lbs/yr and ranged from 65 to 72 

percent of the annual nitrogen total load transported to Lake 

Eucha during runoff. The mean annual phosphorus total load 

reported in Tortorelli (2008) ranged from 77,000 to 88,700 

lbs/yr and ranged from 86 to 89 percent of the annual phosphorus total load transported to Lake Eucha during runoff. 

The greater annual total loads computed by using data from 

2002–09 could be attributed to substantially greater streamflow in calendar year 2008 than other years. Greater streamflow in 2008 also could have contributed to greater average 

contribution of runoff to total flow for the period 2002–09 

compared to 2002–06.

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. The city has spent millions of dollars from 1998–2005 to 

eliminate taste and odor problems in the drinking water from 

the Eucha-Spavinaw system, that may be attributable to bluegreen algae. Increases in algal biomass in the lakes may be 

attributable to increases in nutrient concentrations in the lakes 

and in the waters feeding the lakes. 

In July 2001, the U.S. Geological Survey, in cooperation with the City of Tulsa municipal agency, supplemented 

fixed period, monthly water-quality sampling with six runoff 

samplings per year for four stations along Spavinaw Creek and 

one station on Beaty Creek to better determine water quality during a range of streamflows in the basin. Nitrogen and 

phosphorus concentrations, loads, and yields were determined 

for the period January 2002 through December 2009 to update 

a previous report that used data from water-quality samples 

collected from January 2002 through December 2006.

Table 16. Summary of estimated mean annual total nitrogen and total phosphorus loads to Lake Eucha, Oklahoma, 2002–09.

[lb/yr, pound per year; N, nitrogen; P, phosphorus]

Flow type

Lake Eucha

mean annual 

nitrogen load1

Spavinaw 

Creek near 

Colcord, 

Okla.

component 

of mean 

annual 

nitrogen 

load

(percent)

Beaty 

Creek near 

Jay, Okla.

component 

of mean 

annual 

nitrogen 

load

(percent)

Lake Eucha

mean annual 

phosphorus load

Spavinaw 

Creek near 

Colcord, Okla. 

component of 

mean annual 

phosphorus 

load

(percent)

Beaty Creek 

near Jay, Okla.

component of 

mean annual 

phosphorus 

load

(percent) (lb/yr as N) (percent) (lb/yr as P) (percent)

Base flow2 403,000 24 90 10 9,890 9 91 9

Runoff3 1,278,000 76 75 25 98,500 91 64 36

Total4 1,681,000 100 78 22 108,390 100 66 34

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 9 and 10). 

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 from 2002–09.

3

 Means of the runoff loads are calculated from runoff day data only by S-LOADEST and are statistics of all data from 2002–09.

4

 Differences between total load and the sum of the base-flow load plus runoff loads are because of rounding. 
36 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

Nitrogen concentrations were significantly greater 

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

entire period collected from Spavinaw Creek near Maysville 

and near Cherokee City, Arkansas; Spavinaw Creek near 

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

Significant differences in nitrogen concentrations in base-flow 

and runoff samples were variable by season and station. No 

significant difference in nitrogen concentrations were detected 

between base-flow and runoff samples collected from any station during the spring season. Nitrogen concentrations in baseflow and runoff samples were most often statistically greater 

in samples collected during winter and spring than summer or 

autumn seasons. Nitrogen concentrations in samples collected 

from all stations generally increased with increasing streamflow. Greater concentrations of nitrogen in samples collected 

during runoff than during base flow may indicate addition of 

nitrogen from nonpoint sources.

Nitrogen concentrations in base-flow and runoff samples 

collected in Spavinaw Creek significantly increased (p ≤ 0.05) 

downstream from the Maysville station to the Sycamore station and then significantly decreased downstream from the 

Sycamore station to the Colcord station. Nitrogen concentrations in base-flow and runoff samples collected from Beaty 

Creek were significantly less than in base-flow and runoff 

samples collected from Spavinaw Creek. 

Phosphorus concentrations were significantly greater 

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

collected from all stations for the entire period except from 

the Cherokee City station. Significant differences in phosphorus concentrations in base-flow and runoff samples were 

variable by season and station. Phosphorus concentrations 

were significantly different between base-flow and runoff 

samples collected from the Maysville station and the Beaty 

Creek station for all seasons. The larger concentration of 

phosphorus in samples collected during runoff likely indicates 

phosphorus resuspension, stream bank erosion, or addition of 

phosphorus from nonpoint sources. Phosphorus concentrations 

in base-flow samples were not significantly different among 

seasons at most stations. Phosphorus concentrations in runoff 

samples were not significantly different among seasons for 

any station.

Phosphorus concentrations in base-flow samples collected from Spavinaw Creek significantly increased (p ≤

0.05) from the Maysville station to the Cherokee City station, 

perhaps because of municipal wastewater discharge between 

those stations, and then significantly decreased downstream 

from the Cherokee City station to the Colcord station. Phosphorus concentrations in base-flow samples collected from 

Beaty Creek were significantly less than phosphorus concentrations in base-flow samples collected from Spavinaw Creek 

downstream from the Maysville station. 

Estimated mean annual nitrogen total and base-flow loads 

were substantially greater at the Spavinaw Creek stations than 

at the Beaty Creek station and increased downstream from the 

Maysville station to the Colcord station on Spavinaw Creek. 

The runoff component of the annual nitrogen total load for 

Beaty Creek was 88 percent; at the Spavinaw Creek stations, the range in the runoff component was 67 to 73 percent. Annual nitrogen total, base-flow, and runoff loads were 

greatest during the calendar year 2008, and least during the 

calendar year 2006, the years with the greatest and least mean 

annual streamflow, respectively.

Estimated mean annual phosphorus total loads were 

greater at the Spavinaw Creek stations from the Cherokee City 

station to the Colcord station than at the Beaty Creek station 

and increased downstream from the Maysville station to the 

Colcord station in Spavinaw Creek. Estimated mean annual 

phosphorus base-flow loads at the Spavinaw Creek stations 

were about two to nine times greater than at the Beaty Creek 

station. Phosphorus base-flow loads increased downstream 

by a factor of four from the Maysville station to the Cherokee 

City station in Spavinaw Creek, perhaps because of the inflow 

of discharges from the Decatur wastewater-treatment plant. 

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 79 to 

93 percent. Similar to annual nitrogen loads, annual phosphorus total, base-flow, and runoff loads were the greatest during 

the calendar year 2008 and least during the calendar year 

2006.

Estimated mean seasonal nitrogen base-flow loads generally were least in autumn and greatest in spring and estimated 

mean seasonal nitrogen runoff loads generally were least 

in summer and greatest in spring. Estimated mean seasonal 

phosphorus base-flow and runoff loads generally were least in 

autumn and greatest in spring at all stations with the exception of the Beaty Creek station in which phosphorus base-flow 

loads were least in summer. 

Estimated mean annual nitrogen total yields generally 

increased in a downstream direction in Spavinaw Creek and 

ranged from 6,850 to 8,070 pounds per year per square mile. 

A lesser yield was calculated for the Beaty Creek station 

(6,160 pounds per year per square mile) than for the Maysville 

station (6,850 pounds per year per square mile). Estimated 

mean annual nitrogen base-flow yields ranged from 710 to 

2,500 pounds per year per square mile with the least yield at 

the Beaty Creek station; similar yields among the Maysville 

station, the Sycamore station, and the Colcord station; and the 

greatest yield at the Cherokee City station. The nitrogen baseflow yields at all stations on Spavinaw Creek were about three 

times greater than at the Beaty Creek station. The estimated 

mean annual nitrogen runoff yields ranged from 4,620 to 5,860 

pounds per year per square mile.

Estimated mean annual phosphorus total yields ranged 

from 300 to 620 pounds per year per square mile. The greatest phosphorus total yield was at the Beaty Creek station, 

and the least phosphorus total yield was at the Maysville station in Spavinaw Creek. Estimated mean annual phosphorus 

base-flow yields at the three downstream Spavinaw Creek 

stations ranged from 50 to 80 pounds per year per square 

mile. Estimated mean annual phosphorus base-flow yields 

were the same at the Maysville station in Spavinaw Creek 
References Cited 37

and the Beaty Creek station. Mean annual base-flow yields 

were greater at the three downstream stations on Spavinaw 

Creek than at the Beaty Creek station, and were greater at the 

Cherokee City station than at the Maysville station, probably because of the inflow of discharges from the Decatur 

wastewater-treatment plant between the stations. Estimated 

mean annual phosphorus runoff yields ranged from 280 to 

390 pounds per year per square mile at stations on Spavinaw 

Creek, and the mean runoff yield for Beaty Creek was 600 

pounds per year per square mile. The greater yield in Beaty 

Creek than Spavinaw Creek may be caused by a greater 

contribution of nonpoint sources of phosphorus in Beaty 

Creek, or greater rates of resuspension of phosphorus from the 

streambed and greater rates of streambank erosion. The greater 

runoff yield in Beaty Creek compared to Spavinaw Creek also 

may be related to a lesser influence of groundwater on streamflow for Beaty Creek compared to Spavinaw Creek.

Estimated mean flow-weighted nitrogen concentrations 

at all stations in the basin were about 7 to 10 times greater 

than the 75th percentile of flow-weighted nitrogen concentrations (0.50 milligram per liter) at stations in mostly undeveloped basins of the United States. Estimated mean flowweighted phosphorus concentrations at all stations in the basin 

for all three periods were about five to nine times greater than 

the 75th percentile of flow-weighted phosphorus concentrations (0.037 milligram per liter) at stations in mostly undeveloped basins of the United States. 

Spavinaw Creek and Beaty Creek contributed an estimated mean annual nitrogen total load of 1,681,000 pounds 

per year, 76 percent of which was transported to Lake Eucha 

by runoff. Spavinaw Creek transported about nine times more 

nitrogen load during base flow and about three times more 

nitrogen load during runoff to the lake than did Beaty Creek. 

Spavinaw Creek and Beaty Creek contributed an estimated 

mean annual phosphorus total load of 108,390 pounds per 

year, 91 percent of which was transported to Lake Eucha by 

runoff. Spavinaw Creek transported about 10 times more 

phosphorus load during base flow and about 2 times more 

phosphorus load during runoff to the lake than Beaty Creek. 

Nutrient loads at these stations do not represent the entire 

nutrient load to Lake Eucha, but the drainage area upstream 

from these stations accounts for about 62 percent of the drainage basin upstream from the lake.

Acknowledgments

The authors thank many 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. Special 

thanks goes to the USGS Tulsa Field Office for their contribution to the data collection. Additional thanks go to 

Dave Lorenz for help in the use of the load-estimation program, S-LOADEST; and Dave Mueller for insight into loadestimation equations. 

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Childress, C.J.O., Foreman, W.T., Connor, B.F., and 

Maloney, T.J., 1999, New reporting procedures based on 

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Christensen, V.G., Esralew, R.A., and Allen, M.L., 2008, 

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U.S. Geological Survey Scientific Investigations Report 

2008–5218, 32 p.

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Appendixes 1–5

Appendixes

Appendix 1 43

Appendix 1. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Maysville, Arkansas, 

2002–09.—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

Streamflow1

(ft3

/s)

Total nitrogen 

concentration 

(mg/L as N)2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category3

1/15/2002 0820 COT 35 4.80 0.03 Base flow

2/1/2002 1010 USGS 305 3.40 .05 Runoff

2/12/2002 0815 COT 55 4.80 .02 Base flow

3/12/2002 0845 COT 61 4.20 .02 Base flow

3/20/2002 1445 USGS 221 4.00 .03 Runoff

4/8/2002 1205 USGS 648 3.97 .16 Runoff

4/18/2002 0817 COT 82 4.20 .03 Base flow

5/13/2002 1320 USGS 176 3.44 .03 Runoff

5/17/2002 1300 USGS 1,560 7.40 .50 Runoff

5/23/2002 0808 COT 136 4.54 .04 Runoff

6/13/2002 0838 COT 88 3.68 .04 Runoff

7/18/2002 0832 COT 34 3.41 .03 Base flow

8/13/2002 0820 COT 24 3.20 .03 Base flow

9/19/2002 0810 COT 19 2.85 .03 Base flow

10/16/2002 0735 COT 16 2.80 .03 Base flow

11/12/2002 0753 COT 18 2.85 .03 Base flow

12/12/2002 0818 COT 17 2.90 .02 Base flow

1/7/2003 0845 COT 25 3.36 .02 Base flow

2/6/2003 0817 COT 18 3.15 .02 Base flow

3/5/2003 0818 COT 62 4.43 .03 Runoff

4/9/2003 0822 COT 38 3.76 .02 Base flow

5/8/2003 0825 COT 29 3.10 .02 Base flow

5/16/2003 1100 USGS 92 3.63 .22 Runoff

5/20/2003 1102 USGS 153 3.70 .06 Runoff

5/21/2003 1115 USGS 251 4.16 .04 Runoff

6/2/2003 1258 USGS 49 4.20 .04 Runoff

6/3/2003 0830 COT 48 3.85 -- Runoff

6/12/2003 1102 USGS 48 3.82 .20 Runoff

7/10/2003 0800 COT 21 3.33 .02 Base flow

7/14/2003 1235 USGS 69 3.01 .04 Runoff

8/5/2003 0800 COT 15 2.97 .03 Base flow

9/11/2003 0759 COT 14 2.70 .03 Base flow

10/9/2003 0755 COT 14 2.57 .04 Base flow

11/6/2003 0755 COT 13 2.60 .02 Base flow

11/19/2003 1111 USGS 33 3.06 .03 Runoff

12/10/2003 0820 COT 21 3.53 .02 Base flow

1/6/2004 0840 COT 59 4.28 .02 Runoff

2/5/2004 0815 COT 38 4.55 .02 Base flow

3/4/2004 0825 COT 890 5.57 .29 Runoff

3/4/2004 1125 USGS 809 5.79 .14 Runoff

3/29/2004 1110 USGS 307 4.40 .05 Runoff

4/7/2004 0845 COT 72 4.86 .02 Base flow

4/23/2004 1040 USGS 419 3.43 .05 Runoff

4/24/2004 1435 USGS 2,110 5.68 .80 Runoff

Appendix 1. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Maysville, Arkansas, 

2002–09.

[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]

Appendix 1
44 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

Appendix 1. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Maysville, Arkansas, 

2002–09.—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

Streamflow1

(ft3

/s)

Total nitrogen 

concentration 

(mg/L as N)2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category3

5/6/2004 0817 COT 160 4.87 0.03 Runoff

6/10/2004 0815 COT 43 3.82 .04 Base flow

7/3/2004 1100 USGS 3,970 5.61 .92 Runoff

7/8/2004 0830 COT 170 4.61 .02 Runoff

8/5/2004 0825 COT 64 3.91 .04 Base flow

9/9/2004 0830 COT 29 3.59 .03 Base flow

10/7/2004 0806 COT 22 3.37 .03 Base flow

11/1/2004 1200 USGS 654 4.02 .24 Runoff

11/3/2004 0848 COT 156 4.67 .05 Runoff

12/9/2004 0840 COT 151 5.18 .03 Runoff

1/5/2005 1215 USGS 3,190 9.34 1.2 Runoff

1/6/2005 0858 COT 855 5.57 .17 Runoff

2/10/2005 0832 COT 84 4.80 .03 Base flow

3/10/2005 0837 COT 72 4.36 .03 Base flow

4/7/2005 0845 COT 167 3.88 .06 Runoff

5/12/2005 0825 COT 41 3.87 .03 Base flow

6/9/2005 0902 COT 33 3.53 .03 Base flow

6/14/2005 1145 USGS 78 3.50 .15 Runoff

7/14/2005 0827 COT 22 2.90 .03 Base flow

8/11/2005 0757 COT 19 2.82 .03 Base flow

9/15/2005 0835 COT 15 2.70 .06 Base flow

10/6/2005 0815 COT 13 2.75 .04 Base flow

11/16/2005 0752 COT 16 2.73 .03 Base flow

12/15/2005 0812 COT 14 2.82 .02 Base flow

1/12/2006 0812 COT 16 2.82 .12 Base flow

2/9/2006 0823 COT 14 2.73 .03 Base flow

3/9/2006 0805 COT 14 2.60 .02 Base flow

4/12/2006 0802 COT 18 2.66 -- Base flow

4/29/2006 1330 USGS 29 2.37 .03 Runoff

5/2/2006 1335 USGS 84 3.22 .03 Runoff

5/10/2006 0830 COT 63 .69 .05 Runoff

5/10/2006 1135 USGS 61 3.15 .04 Runoff

6/8/2006 0837 COT 28 --4 .03 Runoff

7/13/2006 0856 COT 9.8 --4 .04 Base flow

7/13/2006 1100 USGS 9.8 2.37 .03 Base flow

8/10/2006 0755 COT 6.0 1.98 -- Base flow

8/28/2006 1135 USGS 61 2.29 .06 Runoff

9/14/2006 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

12/6/2006 0847 COT 70 5.00 -- Runoff

1/11/2007 0908 COT 38 6.00 .07 Base flow

1/23/2007 1100 USGS 145 5.64 .04 Runoff

2/8/2007 0855 COT 39 5.20 .02 Base flow
Appendix 1 45

Appendix 1. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Maysville, Arkansas, 

2002–09.—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

Streamflow1

(ft3

/s)

Total nitrogen 

concentration 

(mg/L as N)2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category3

3/7/2007 0857 COT 41 4.74 0.03 Base flow

4/19/2007 0850 COT 40 3.43 .03 Runoff

5/8/2007 0827 COT 72 2.87 .04 Runoff

5/8/2007 1330 USGS 73 3.10 .04 Runoff

5/30/2007 1045 USGS 26 3.09 .03 Base flow

6/7/2007 0822 COT 23 3.00 .03 Base flow

6/20/2007 1330 USGS 22 2.86 .03 Base flow

7/12/2007 0829 COT 19 2.63 .03 Base flow

7/25/2007 1130 USGS 17 2.53 .07 Base flow

8/9/2007 0600 COT 12 2.50 .04 Base flow

9/7/2007 1230 USGS 67 2.71 .04 Runoff

9/13/2007 0840 COT 49 3.82 .02 Runoff

10/3/2007 1215 USGS 232 4.30 .11 Runoff

10/3/2007 1215 USGS 235 4.30 .11 Runoff

10/11/2007 0845 COT 45 4.70 .03 Runoff

11/8/2007 0805 COT 23 4.30 .03 Base flow

12/12/2007 1125 USGS 271 6.20 .05 Runoff

12/18/2007 1213 COT 147 5.90 .03 Runoff

1/8/2008 1100 USGS 1,960 7.27 .70 Runoff

1/17/2008 0910 COT 82 6.10 .04 Runoff

2/14/2008 0850 COT 88 4.90 .03 Runoff

2/17/2008 1420 USGS 1,420 5.58 .52 Runoff

3/3/2008 1100 USGS 764 4.26 .11 Runoff

3/12/2008 0850 COT 112 5.40 -- Base flow

3/18/2008 1115 USGS 3,170 5.69 .94 Runoff

4/16/2008 0850 COT 215 4.48 .04 Base flow

5/7/2008 0845 COT 120 4.00 .03 Base flow

6/12/2008 0900 COT 251 3.80 .05 Runoff

7/16/2008 0840 COT 145 4.00 .04 Runoff

8/14/2008 0900 COT 66 3.70 .04 Base flow

9/5/2008 1100 USGS 198 3.60 .05 Runoff

9/11/2008 0845 COT 67 3.90 .04 Base flow

9/14/2008 1045 USGS 789 4.05 .36 Runoff

10/9/2008 0940 COT 49 4.10 .03 Base flow

11/6/2008 0840 COT 42 3.80 .04 Base flow

12/11/2008 0915 COT 29 4.00 .04 Base flow

1/8/2009 0925 COT 31 3.90 .03 Base flow

2/12/2009 0900 COT 427 4.30 .05 Runoff

2/12/2009 1030 USGS 416 4.50 .05 Runoff

3/5/2009 0820 COT 45 4.40 .04 Base flow

4/16/2009 0850 COT 208 4.10 .09 Runoff

5/4/2009 1030 USGS 730 3.30 .07 Runoff

5/8/2009 1350 USGS 1,515 3.15 .68 Runoff

5/14/2009 0855 COT 330 4.20 .27 Runoff
46 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

Appendix 1. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Maysville, Arkansas, 

2002–09.—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

Streamflow1

(ft3

/s)

Total nitrogen 

concentration 

(mg/L as N)2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category3

6/11/2009 0855 COT 115 4.00 0.04 Runoff

7/9/2009 0840 COT 43 3.80 .04 Base flow

8/13/2009 0900 COT 51 3.60 .04 Runoff

9/10/2009 0850 COT 47 3.58 .05 Runoff

10/8/2009 0745 COT 34 3.70 .03 Base flow

10/9/2009 1015 USGS 3,580 5.43 .90 Runoff

11/5/2009 0840 COT 119 4.50 .04 Runoff

12/9/2009 0850 COT 57 4.20 .03 Base flow

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 were substituted in the total nitrogen calculation for this sample.
Appendix 2 47

Appendix 2. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Cherokee, Arkansas, 

2002–09.—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

Streamflow1 

(ft3/s)

Total nitrogen 

concentration 

(mg/L as N)2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category3

1/15/2002 0835 COT 41 5.40 0.23 Base flow

2/1/2002 1236 USGS 290 3.60 .17 Runoff

2/12/2002 0835 COT 71 5.20 .23 Base flow

3/12/2002 0900 COT 82 4.40 .23 Base flow

3/20/2002 1641 USGS 233 4.83 .17 Runoff

4/8/2002 1410 USGS 700 4.26 .19 Runoff

4/18/2002 0835 COT 101 4.60 .20 Base flow

5/13/2002 1510 USGS 190 3.28 .17 Runoff

5/17/2002 1630 USGS 1,590 6.82 .38 Runoff

5/23/2002 0823 COT 150 4.40 .17 Runoff

6/13/2002 0850 COT 107 3.92 .19 Runoff

7/18/2002 0847 COT 42 3.59 .23 Base flow

8/13/2002 0835 COT 26 3.33 .23 Base flow

9/19/2002 0825 COT 25 3.16 .30 Base flow

10/16/2002 0755 COT 17 3.11 .32 Base flow

11/12/2002 0808 COT 24 3.49 .31 Base flow

12/12/2002 0833 COT 19 3.54 .30 Base flow

1/7/2003 0900 COT 33 4.11 .30 Runoff

2/6/2003 0834 COT 20 4.13 .26 Base flow

3/5/2003 0900 COT 67 4.94 .19 Runoff

4/9/2003 0836 COT 54 4.22 .18 Base flow

5/8/2003 0840 COT 32 3.28 .23 Base flow

5/14/2003 0800 COT 31 4.44 .22 Base flow

5/16/2003 0945 COT 134 3.05 .50 Runoff

5/16/2003 1211 USGS 134 3.21 .03 Runoff

5/20/2003 1258 USGS 165 4.00 .25 Runoff

5/21/2003 1247 USGS 310 4.34 .13 Runoff

6/2/2003 1405 USGS 54 2.48 .19 Runoff

6/3/2003 0850 COT 52 4.27 .14 Runoff

6/11/2003 0910 COT 38 4.10 .19 Base flow

6/12/2003 1218 USGS 49 4.20 .03 Runoff

7/10/2003 0815 COT 22 3.64 .20 Base flow

7/14/2003 1054 USGS 61 3.46 .17 Runoff

8/5/2003 0820 COT 17 3.45 .21 Base flow

9/11/2003 0826 COT 16 3.51 .21 Base flow

10/9/2003 0815 COT 21 3.66 .22 Base flow

11/6/2003 0811 COT 19 3.90 .23 Base flow

11/19/2003 1236 USGS 41 4.22 .23 Runoff

12/10/2003 0845 COT 29 4.21 .18 Runoff

1/6/2004 0855 COT 79 4.99 .15 Runoff

2/5/2004 0835 COT 49 5.46 .14 Base flow

3/4/2004 0840 COT 1,100 5.73 .34 Runoff

3/4/2004 1510 USGS 912 6.28 .20 Runoff

3/29/2004 1235 USGS 375 4.52 .10 Runoff

Appendix 2. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Cherokee, Arkansas, 

2002–09.

[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]

Appendix 2
48 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

Appendix 2. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Cherokee, Arkansas, 

2002–09.—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

Streamflow1 

(ft3/s)

Total nitrogen 

concentration 

(mg/L as N)2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category3

4/7/2004 0900 COT 80 5.12 0.11 Base flow

4/23/2004 1259 USGS 470 3.87 .08 Runoff

4/24/2004 1735 USGS 2,210 4.99 .64 Runoff

5/6/2004 0837 COT 207 5.22 .11 Runoff

6/10/2004 0830 COT 57 4.21 .14 Base flow

7/3/2004 0926 USGS 8,000 2.68 1.30 Runoff

7/8/2004 0845 COT 207 5.04 .13 Runoff

8/5/2004 0840 COT 86 4.48 .19 Base flow

9/9/2004 0845 COT 33 4.20 .14 Base flow

10/7/2004 0820 COT 24 4.30 .16 Base flow

11/1/2004 1400 USGS 657 4.66 .24 Runoff

11/3/2004 0905 COT 199 5.20 .15 Runoff

12/9/2004 0855 COT 184 5.58 .11 Runoff

1/5/2005 1325 USGS 3,780 10.4 1.20 Runoff

1/6/2005 0915 COT 1,440 6.13 .23 Runoff

2/10/2005 0848 COT 97 5.30 .08 Base flow

3/10/2005 0852 COT 83 4.89 .09 Base flow

4/7/2005 0900 COT 219 4.18 .19 Runoff

5/12/2005 0840 COT 37 4.13 .15 Base flow

6/9/2005 0919 COT 35 3.81 .11 Base flow

6/14/2005 1440 USGS 105 3.34 .14 Runoff

7/14/2005 0844 COT 24 3.28 .17 Base flow

8/11/2005 0815 COT 22 3.99 .16 Base flow

10/6/2005 0825 COT 16 3.55 .16 Base flow

11/16/2005 0815 COT 25 4.04 .15 Base flow

12/15/2005 0828 COT 14 3.69 .12 Base flow

1/12/2006 0825 COT 18 4.37 .14 Base flow

2/9/2006 0840 COT 16 3.98 .16 Base flow

3/9/2006 0820 COT 19 3.71 .12 Base flow

4/12/2006 0818 COT 26 2.96 -- Runoff

4/29/2006 1645 USGS 46 3.15 .15 Runoff

5/2/2006 1455 USGS 103 3.51 .13 Runoff

5/10/2006 0845 COT 112 3.37 .14 Runoff

5/10/2006 1245 USGS 101 3.67 .13 Runoff

6/8/2006 0853 COT 29 --4 .15 Runoff

7/13/2006 0920 COT 13 --4 .15 Base flow

7/13/2006 1245 USGS 13 2.97 .13 Base flow

8/10/2006 0810 COT 10 2.56 -- Base flow

8/28/2006 1315 USGS 77 4.28 .19 Runoff

9/14/2006 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

12/6/2006 0905 COT 80 5.57 -- Runoff

1/11/2007 0930 COT 40 5.74 .09 Base flow
Appendix 2 49

Appendix 2. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Cherokee, Arkansas, 

2002–09.—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

Streamflow1 

(ft3/s)

Total nitrogen 

concentration 

(mg/L as N)2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category3

1/23/2007 1400 USGS 187 6.04 0.09 Runoff

2/8/2007 0912 COT 52 6.08 .09 Base flow

3/7/2007 0912 COT 47 5.07 .09 Base flow

4/19/2007 0910 COT 54 3.73 .08 Runoff

5/8/2007 0845 COT 103 3.27 .09 Runoff

5/8/2007 1430 USGS 101 3.31 .09 Runoff

5/30/2007 1200 USGS 33 3.22 .10 Base flow

6/7/2007 0738 COT 29 3.26 .09 Base flow

6/20/2007 1145 USGS 27 3.20 .10 Base flow

7/12/2007 0845 COT 26 2.82 .10 Base flow

7/25/2007 1230 USGS 20 2.52 .10 Base flow

8/9/2007 0827 COT 15 2.45 .11 Base flow

9/7/2007 1345 USGS 77 2.85 .12 Runoff

9/13/2007 0900 COT 71 3.98 .09 Runoff

10/3/2007 1600 USGS 292 4.80 .16 Runoff

10/11/2007 0905 COT 77 5.40 .12 Runoff

10/18/2007 1405 USGS 75 4.60 .10 Runoff

11/8/2007 0822 COT 34 4.90 .10 Base flow

12/12/2007 1235 USGS 409 5.80 .08 Runoff

12/18/2007 1230 COT 143 6.70 .07 Runoff

1/8/2008 1330 USGS 2,370 7.14 .63 Runoff

1/17/2008 0928 COT 103 6.70 .09 Runoff

2/14/2008 0905 COT 117 5.30 .07 Runoff

2/17/2008 1530 USGS 1,950 6.04 .38 Runoff

3/3/2008 1345 USGS 832 4.32 .11 Runoff

3/12/2008 0915 COT 131 5.70 .06 Base flow

3/18/2008 1530 USGS 5,030 6.14 1.60 Runoff

4/16/2008 0905 COT 276 4.60 .08 Base flow

5/7/2008 0905 COT 125 4.20 .06 Base flow

6/12/2008 0920 COT 327 3.90 .10 Runoff

7/16/2008 0855 COT 184 4.20 .08 Runoff

8/14/2008 0920 COT 78 4.10 .09 Runoff

9/5/2008 1230 USGS 208 4.09 .09 Runoff

9/11/2008 0900 COT 87 4.40 .08 Base flow

9/14/2008 1200 USGS 923 4.33 .18 Runoff

10/9/2008 0925 COT 60 4.60 .08 Base flow

11/6/2008 0900 COT 46 4.40 .07 Base flow

12/11/2008 0935 COT 35 4.30 .08 Base flow

1/8/2009 0945 COT 38 4.60 .07 Base flow

2/12/2009 0915 COT 366 4.80 .07 Runoff

2/12/2009 1115 USGS 358 4.60 .07 Runoff

3/5/2009 0838 COT 54 4.80 .07 Base flow

4/16/2009 0910 COT 251 4.50 .07 Runoff

5/4/2009 1145 USGS 626 3.80 .07 Runoff
50 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

Appendix 2. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Cherokee, Arkansas, 

2002–09.—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

Streamflow1 

(ft3/s)

Total nitrogen 

concentration 

(mg/L as N)2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category3

5/8/2009 1330 USGS 1,030 6.40 0.43 Runoff

5/14/2009 0915 COT 273 5.24 .11 Runoff

6/11/2009 0915 COT 128 4.30 .09 Runoff

7/9/2009 0855 COT 46 4.20 .08 Base flow

8/13/2009 0920 COT 63 3.80 .09 Runoff

9/10/2009 0900 COT 58 3.40 .10 Runoff

10/8/2009 0800 COT 40 4.00 .10 Base flow

10/9/2009 1200 USGS 3,800 6.12 1.10 Runoff

11/5/2009 0900 COT 133 4.80 .09 Runoff

12/9/2009 0910 COT 62 4.50 .09 Base flow

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 were substituted in the total nitrogen calculation for this sample.
Appendix 3 51

Appendix 3. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Sycamore, Oklahoma, 

2002–09.—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

Streamflow1

(ft3

/s)

Total nitrogen 

concentration 

(mg/L as N)2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category3

1/15/2002 0755 COT 54 5.50 0.14 Base flow

2/1/2002 1506 USGS 384 3.20 .16 Runoff

2/12/2002 0750 COT 92 5.30 .15 Base flow

3/12/2002 0815 COT 105 4.50 .15 Base flow

3/21/2002 1123 USGS 268 4.40 .14 Runoff

4/8/2002 1708 USGS 952 5.06 .18 Runoff

4/18/2002 0817 COT 131 4.70 .15 Base flow

5/13/2002 1205 USGS 203 3.84 .17 Runoff

5/17/2002 1428 USGS 885 7.10 .31 Runoff

5/23/2002 0740 COT 174 4.30 .15 Runoff

6/13/2002 0803 COT 135 3.96 .15 Base flow

7/18/2002 0800 COT 46 3.65 .14 Base flow

1/7/2003 0818 COT 44 4.07 .16 Runoff

3/5/2003 0700 COT 110 4.97 .14 Runoff

4/9/2003 0757 COT 57 4.02 .14 Base flow

5/16/2003 1335 USGS 151 3.68 .19 Runoff

5/20/2003 1705 USGS 242 4.10 .27 Runoff

5/21/2003 1437 USGS 345 4.29 .10 Runoff

6/2/2003 1519 USGS 68 3.87 .13 Runoff

6/3/2003 0800 COT 71 4.25 -- Runoff

6/16/2003 1312 USGS 72 3.99 .13 Runoff

9/2/2003 1220 USGS 22 3.58 .17 Runoff

1/6/2004 0815 COT 93 5.38 .12 Runoff

1/18/2004 1540 USGS 137 5.70 .12 Runoff

2/5/2004 0740 COT 56 5.36 .11 Base flow

3/4/2004 0754 COT 1,500 6.15 .46 Runoff

3/4/2004 1135 USGS 1,310 6.44 .19 Runoff

3/29/2004 1430 USGS 462 4.82 .10 Runoff

4/7/2004 0817 COT 100 5.22 .09 Base flow

4/23/2004 1445 USGS 561 3.54 .12 Runoff

4/24/2004 1445 USGS 3,120 5.97 .97 Runoff

5/6/2004 0750 COT 291 5.17 .10 Runoff

6/10/2004 0750 COT 62 4.24 .13 Base flow

7/3/2004 1327 USGS 4,810 5.48 .98 Runoff

7/8/2004 0800 COT 330 5.05 .12 Runoff

8/5/2004 0755 COT 148 4.39 .12 Base flow

9/9/2004 0800 COT 50 4.21 .12 Base flow

11/1/2004 1600 USGS 1,010 4.95 .24 Runoff

11/3/2004 0818 COT 353 5.21 .15 Runoff

12/9/2004 0812 COT 317 5.58 .09 Runoff

1/5/2005 1440 USGS 3,860 9.36 1.2 Runoff

1/6/2005 0827 COT 1,690 5.89 .25 Runoff

2/10/2005 0805 COT 117 5.45 .10 Base flow

3/10/2005 0811 COT 100 4.88 .11 Base flow

Appendix 3. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Sycamore, Oklahoma, 

2002–09.

[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]

Appendix 3
52 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

Appendix 3. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Sycamore, Oklahoma, 

2002–09.—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

Streamflow1

(ft3

/s)

Total nitrogen 

concentration 

(mg/L as N)2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category3

4/7/2005 0815 COT 292 4.87 0.09 Runoff

5/12/2005 0755 COT 51 4.29 .14 Base flow

6/9/2005 0830 COT 41 3.92 .10 Base flow

6/15/2005 1115 USGS 89 3.85 .11 Runoff

4/29/2006 1845 USGS 27 3.15 .11 Runoff

5/2/2006 1515 USGS 109 3.83 .08 Runoff

5/10/2006 0803 COT 101 3.86 .13 Runoff

5/10/2006 1330 USGS 150 3.52 .13 Runoff

7/13/2006 0825 COT 5.8 -- .12 Base flow

7/13/2006 0900 USGS 5.8 3.18 .10 Base flow

8/28/2006 1145 USGS 18 3.03 .12 Runoff

12/6/2006 0814 COT 104 5.60 -- Runoff

1/11/2007 0837 COT 42 7.35 .18 Base flow

1/23/2007 1430 USGS 293 6.24 .08 Runoff

2/8/2007 0827 COT 58 5.90 .08 Base flow

3/7/2007 0825 COT 51 5.32 .09 Base flow

4/19/2007 0822 COT 65 4.03 .09 Runoff

5/8/2007 0755 COT 233 3.59 .10 Runoff

5/8/2007 1100 USGS 226 3.50 .08 Runoff

5/29/2007 1115 USGS 35 3.41 .08 Base flow

6/20/2007 1030 USGS 36 3.26 .09 Base flow

7/25/2007 0945 USGS 29 2.80 .08 Base flow

9/10/2007 1145 USGS 163 3.75 .10 Runoff

9/13/2007 0811 COT 83 3.83 .10 Runoff

10/3/2007 1400 USGS 663 5.20 .19 Runoff

10/11/2007 0810 COT 96 5.50 .09 Runoff

12/11/2007 1515 USGS 640 5.70 .09 Runoff

12/18/2007 1142 COT 214 6.60 .07 Runoff

1/8/2008 1305 USGS 3,040 7.67 .75 Runoff

1/17/2008 0835 COT 134 6.70 .10 Runoff

2/14/2008 0818 COT 143 5.50 .07 Runoff

2/17/2008 1245 USGS 2,320 5.91 .40 Runoff

3/3/2008 1215 USGS 1,200 4.93 .23 Runoff

3/12/2008 0817 COT 137 5.80 -- Base flow

3/18/2008 1130 USGS 5,280 5.84 .98 Runoff

4/16/2008 0810 COT 318 4.50 .08 Base flow

5/7/2008 0815 COT 150 4.38 .11 Base flow

6/12/2008 0824 COT 434 4.00 .10 Runoff

7/16/2008 0810 COT 266 4.20 .08 Runoff

8/14/2008 0825 COT 106 4.20 .08 Runoff

9/5/2008 1400 USGS 297 4.00 .09 Runoff

9/11/2008 0810 COT 119 4.30 .08 Base flow

9/14/2008 1320 USGS 1,210 4.36 .20 Runoff

10/9/2008 0840 COT 63 4.60 .08 Base flow
Appendix 3 53

Appendix 3. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Sycamore, Oklahoma, 

2002–09.—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

Streamflow1

(ft3

/s)

Total nitrogen 

concentration 

(mg/L as N)2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category3

11/6/2008 0810 COT 45 4.50 0.08 Base flow

12/11/2008 0845 COT 32 4.60 .09 Base flow

1/8/2009 0855 COT 45 4.60 .08 Base flow

2/11/2009 1345 USGS 249 4.80 .10 Runoff

2/12/2009 0830 COT 472 4.80 .08 Runoff

3/5/2009 0752 COT 58 5.00 .08 Base flow

4/16/2009 0815 COT 167 4.6 .10 Runoff

5/4/2009 1400 USGS 689 4.10 .07 Runoff

5/8/2009 1515 USGS 975 6.16 .42 Runoff

5/14/2009 0820 COT 358 4.70 .22 Runoff

6/11/2009 0820 COT 181 4.50 .08 Runoff

7/9/2009 0800 COT 61 4.40 .08 Base flow

8/13/2009 0830 COT 87 4.10 .09 Runoff

11/5/2009 0805 COT 163 4.80 .08 Runoff

12/9/2009 0815 COT 71 4.60 .02 Base flow

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).
54 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

Appendix 4. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Colcord, Oklahoma, 

2002–09.—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

Streamflow1

(ft3

/s)

Total nitrogen 

concentration 

(mg/L as N)2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category3

1/15/2002 0905 COT 73 5.20 0.11 Base flow

2/1/2002 1706 USGS 388 3.90 .14 Runoff

2/12/2002 0900 COT 113 5.00 .11 Base flow

3/12/2002 0927 COT 132 4.10 .11 Base flow

3/21/2002 1445 USGS 349 4.10 .12 Runoff

4/9/2002 1026 USGS 769 4.10 .13 Runoff

4/18/2002 0902 COT 176 4.40 .13 Base flow

5/13/2002 1342 USGS 269 3.51 .13 Runoff

5/17/2002 1850 USGS 1,670 6.29 .39 Runoff

5/23/2002 0852 COT 210 4.00 .12 Base flow

6/13/2002 0917 COT 168 3.62 .12 Base flow

7/18/2002 0914 COT 58 3.42 .10 Base flow

8/13/2002 0902 COT 36 3.22 .10 Base flow

9/19/2002 0805 COT 22 2.82 .10 Base flow

10/16/2002 0820 COT 21 2.91 .09 Base flow

11/12/2002 0837 COT 33 3.18 .09 Base flow

12/12/2002 0900 COT 34 3.21 .10 Base flow

1/7/2003 0925 COT 59 3.80 .10 Runoff

2/6/2003 0900 COT 30 3.67 .09 Base flow

3/5/2003 0930 COT 113 4.39 .10 Base flow

4/9/2003 0902 COT 61 3.86 .10 Base flow

5/8/2003 0907 COT 48 3.23 .10 Base flow

5/14/2003 0830 COT 61 5.27 .13 Runoff

5/16/2003 1010 COT 467 2.89 .98 Runoff

5/16/2003 1504 USGS 446 3.86 .18 Runoff

5/20/2003 1435 USGS 349 2.30 .28 Runoff

5/21/2003 1607 USGS 446 4.81 .11 Runoff

6/2/2003 1639 USGS 113 4.22 .12 Runoff

6/3/2003 0920 COT 102 3.76 .15 Runoff

6/11/2003 0945 COT 57 3.78 .12 Base flow

6/16/2003 1452 USGS 80 3.69 .11 Runoff

7/10/2003 0841 COT 27 3.23 .09 Base flow

8/5/2003 0845 COT 24 3.01 .09 Base flow

9/2/2003 1418 USGS 88 3.13 .12 Runoff

9/11/2003 0901 COT 44 3.19 .09 Runoff

10/9/2003 0840 COT 23 3.00 .09 Base flow

11/6/2003 0840 COT 23 3.20 .09 Base flow

11/19/2003 1545 USGS 80 3.80 .09 Runoff

12/10/2003 0925 COT 33 3.77 .08 Base flow

1/6/2004 0922 COT 138 4.59 .12 Runoff

1/18/2004 1350 USGS 270 4.50 .10 Runoff

2/5/2004 0850 COT 95 5.05 .09 Base flow

3/4/2004 0909 COT 2,390 5.7 .60 Runoff

3/4/2004 0945 USGS 2,320 6.23 .28 Runoff

Appendix 4. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Colcord, Oklahoma, 

2002–09.

[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]

Appendix 4
Appendix 4 55

Appendix 4. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Colcord, Oklahoma, 

2002–09.—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

Streamflow1

(ft3

/s)

Total nitrogen 

concentration 

(mg/L as N)2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category3

3/29/2004 1600 USGS 646 4.94 0.10 Runoff

4/7/2004 0931 COT 150 4.74 .08 Base flow

4/23/2004 1315 USGS 792 3.32 .10 Runoff

4/24/2004 1235 USGS 4,130 6.08 .99 Runoff

5/6/2004 0904 COT 337 4.62 .09 Runoff

6/10/2004 0900 COT 74 4.37 .09 Base flow

7/3/2004 1405 USGS 7,200 3.54 .94 Runoff

7/8/2004 0910 COT 424 4.51 .09 Runoff

8/5/2004 0910 COT 172 3.98 .15 Base flow

9/9/2004 0910 COT 69 4.04 .11 Base flow

10/7/2004 0845 COT 34 3.81 .08 Base flow

11/1/2004 1730 USGS 1,280 4.68 .19 Runoff

11/3/2004 0935 COT 397 4.70 .13 Runoff

12/9/2004 0927 COT 374 5.03 .08 Runoff

1/5/2005 1430 USGS 5,700 9.62 1.10 Runoff

1/6/2005 0945 COT 2,190 5.54 .23 Runoff

2/10/2005 0917 COT 155 5.18 .08 Base flow

3/10/2005 0920 COT 129 4.59 .08 Base flow

4/7/2005 0928 COT 296 3.90 .09 Runoff

5/12/2005 0907 COT 84 4.07 .11 Base flow

6/9/2005 0950 COT 47 3.64 .08 Base flow

6/15/2005 1350 USGS 90 3.63 .15 Runoff

7/14/2005 0915 COT 34 2.90 .09 Base flow

8/11/2005 0850 COT 30 3.02 .08 Base flow

9/15/2005 0925 COT 21 2.90 .07 Base flow

10/6/2005 0900 COT 19 3.06 .08 Base flow

11/16/2005 0845 COT 27 3.46 .07 Base flow

12/15/2005 0857 COT 21 3.55 .07 Base flow

1/12/2006 0855 COT 21 3.64 .26 Base flow

2/9/2006 0913 COT 22 3.61 .08 Base flow

3/9/2006 0850 COT 30 3.32 .07 Base flow

4/12/2006 0850 USGS 34 2.94 -- Runoff

4/29/2006 1355 USGS 68 2.67 .10 Runoff

5/2/2006 1410 USGS 153 3.41 .09 Runoff

5/10/2006 0917 COT 142 3.18 .10 Runoff

5/10/2006 1150 USGS 191 3.41 .13 Runoff

6/8/2006 0925 COT 39 --4 .10 Runoff

7/13/2006 0947 COT 13 --4 .07 Base flow

7/13/2006 1300 USGS 12 2.47 .07 Base flow

8/10/2006 0842 USGS 11 2.28 -- Base flow

8/28/2006 1345 USGS 30 2.08 .07 Runoff

9/14/2006 0927 USGS 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
56 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

Appendix 4. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Colcord, Oklahoma, 

2002–09.—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

Streamflow1

(ft3

/s)

Total nitrogen 

concentration 

(mg/L as N)2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category3

12/6/2006 0940 COT 132 5.03 -- Runoff

1/11/2007 1002 COT 82 5.44 0.07 Base flow

1/23/2007 1600 USGS 306 5.69 .09 Runoff

2/8/2007 0945 COT 99 5.84 .08 Base flow

3/7/2007 0938 COT 88 5.01 .07 Base flow

4/19/2007 0942 COT 90 3.79 .08 Runoff

5/7/2007 1410 USGS 329 3.14 .35 Runoff

5/8/2007 0918 COT 325 3.12 .12 Runoff

5/8/2007 1320 USGS 311 3.17 .24 Runoff

5/29/2007 1245 USGS 57 2.68 .04 Base flow

6/7/2007 0910 COT 43 3.01 .07 Base flow

6/12/2007 1445 USGS 700 8.11 1.50 Runoff

6/13/2007 1315 USGS 199 2.73 .10 Runoff

6/18/2007 1030 USGS 82 3.02 .08 Runoff

7/12/2007 0918 COT 53 2.60 .06 Base flow

7/24/2007 1000 USGS 37 2.38 .06 Base flow

8/2/2007 1330 USGS 28 2.20 .07 Base flow

8/9/2007 0900 COT 21 2.25 .07 Base flow

9/10/2007 1315 USGS 187 3.36 .10 Runoff

9/13/2007 0930 COT 129 3.37 .07 Runoff

10/2/2007 1045 USGS 57 3.10 .11 Runoff

10/3/2007 1200 USGS 741 5.24 .24 Runoff

10/11/2007 0930 COT 132 4.90 .09 Runoff

10/18/2007 1200 USGS 90 4.50 .09 Base flow

11/8/2007 0855 COT 53 4.50 .08 Base flow

12/11/2007 1400 USGS 564 5.10 .12 Runoff

12/18/2007 1255 COT 239 6.10 .06 Runoff

1/8/2008 1000 USGS 5,520 7.58 .90 Runoff

1/17/2008 1000 COT 195 6.20 .08 Runoff

2/14/2008 0935 COT 206 5.00 .07 Runoff

2/17/2008 1100 USGS 3,470 6.00 .71 Runoff

3/3/2008 1100 USGS 2,180 5.10 .25 Runoff

3/12/2008 0940 COT 187 5.40 .06 Runoff

3/18/2008 1445 USGS 9,620 6.22 1.60 Runoff

4/1/2008 1000 USGS 1,100 3.80 .12 Runoff

4/16/2008 0935 COT 404 4.20 .08 Base flow

5/7/2008 0935 COT 184 3.80 .06 Base flow

6/10/2008 1400 USGS 1,780 3.26 .16 Runoff

6/12/2008 0950 COT 585 3.60 .09 Runoff

7/16/2008 0923 COT 321 3.70 .07 Runoff

8/14/2008 0950 COT 137 3.70 .08 Runoff

9/5/2008 1200 USGS 305 3.80 .08 Runoff

9/11/2008 0930 COT 137 4.00 .08 Base flow

9/14/2008 1245 USGS 2,060 4.02 .33 Runoff
Appendix 4 57

Appendix 4. Streamflows, and total nitrogen and total phosphorus concentrations for Spavinaw Creek near Colcord, Oklahoma, 

2002–09.—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

Streamflow1

(ft3

/s)

Total nitrogen 

concentration 

(mg/L as N)2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category3

10/9/2008 0950 COT 98 4.20 0.08 Base flow

11/6/2008 0930 COT 68 4.20 .07 Base flow

12/11/2008 1005 COT 54 4.10 .07 Base flow

1/8/2009 1010 COT 73 4.30 .07 Runoff

2/11/2009 1215 USGS 471 4.45 .24 Runoff

2/12/2009 0945 COT 809 4.99 .09 Runoff

3/5/2009 0910 COT 88 4.40 .06 Base flow

3/30/2009 1245 USGS 382 3.90 .06 Runoff

4/16/2009 0940 COT 366 4.10 .06 Runoff

5/4/2009 1045 USGS 1,250 4.13 .08 Runoff

5/8/2009 1620 USGS 1,300 4.97 .19 Runoff

5/14/2009 0940 COT 570 4.30 .28 Runoff

6/11/2009 0940 COT 233 4.20 .07 Runoff

7/9/2009 0930 COT 75 3.90 .06 Base flow

8/13/2009 0950 COT 108 3.60 .07 Runoff

9/10/2009 0930 COT 181 3.12 .24 Runoff

9/10/2009 1515 USGS 125 2.70 .10 Runoff

9/22/2009 1045 USGS 509 3.73 .18 Runoff

10/8/2009 0830 COT 55 3.90 .08 Runoff

10/9/2009 1630 USGS 5,760 5.29 .83 Runoff

11/5/2009 0930 COT 268 4.85 .08 Runoff

12/9/2009 0950 COT 96 4.30 .07 Base flow

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 were substituted in the total nitrogen calculation for this sample.
58 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

Appendix 5. Streamflows, and total nitrogen and total phosphorus concentrations for Beaty Creek near Jay, Oklahoma, 2002–09.—

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

Streamflow1

(ft3

/s)

Total nitrogen 

concentration 

(mg/L as N)2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category3

1/15/2002 0940 COT 10 3.20 0.04 Base flow

2/1/2002 1911 USGS 99 2.60 .05 Runoff

2/12/2002 0755 COT 25 3.20 .03 Runoff

3/12/2002 0750 COT 33 2.70 .03 Runoff

4/8/2002 1837 USGS 189 3.60 .15 Runoff

4/18/2002 0752 COT 29 2.90 .04 Runoff

5/17/2002 1220 USGS 231 3.98 .17 Runoff

5/23/2002 0805 COT 54 2.80 .05 Runoff

5/28/2002 1542 USGS 519 4.68 .81 Runoff

6/13/2002 0735 COT 58 2.57 .05 Runoff

7/18/2002 0742 COT 7.2 2.27 .03 Base flow

8/13/2002 0820 COT 1.8 1.45 .05 Base flow

9/19/2002 0755 COT 0 1.15 .05 Base flow

10/16/2002 0800 COT .1 1.24 .04 Base flow

11/12/2002 0920 COT 2.8 1.34 .03 Base flow

12/12/2002 0755 COT 4.4 1.34 .03 Base flow

1/7/2003 0750 COT 7.2 1.79 .04 Base flow

2/6/2003 0755 COT 3.9 1.53 .02 Base flow

3/5/2003 0735 COT 39 2.93 .02 Runoff

4/9/2003 0720 COT 17 2.16 .03 Base flow

5/8/2003 0725 COT 12 1.53 .04 Base flow

5/14/2003 0850 COT 26 2.01 .04 Runoff

5/16/2003 1048 COT 127 1.41 .08 Runoff

5/16/2003 1741 USGS 414 3.27 .15 Runoff

5/20/2003 1929 USGS 263 3.60 .28 Runoff

5/21/2003 1743 USGS 135 3.01 .07 Runoff

6/2/2003 1755 USGS 118 3.78 .06 Runoff

6/3/2003 0730 COT 108 2.30 .04 Runoff

6/11/2003 1000 COT 22 2.27 .04 Runoff

6/26/2003 1044 USGS 12 1.87 .04 Runoff

7/10/2003 0750 COT 7.5 1.85 .03 Base flow

8/5/2003 0730 COT .4 1.62 .04 Base flow

9/2/2003 1549 USGS 15 1.13 .04 Runoff

9/11/2003 0727 COT 3.0 .87 .03 Base flow

10/9/2003 0705 COT 4.0 .93 .03 Base flow

11/6/2003 0730 COT 6.4 1.00 .04 Base flow

11/19/2003 1722 USGS 15 1.51 .03 Runoff

12/10/2003 0750 COT 6.7 2.26 .03 Base flow

1/6/2004 0735 COT 26 2.58 .03 Runoff

1/18/2004 1205 USGS 212 3.45 .11 Runoff

2/5/2004 0725 COT 25 4.02 .03 Base flow

3/4/2004 0744 COT 1,350 4.93 .96 Runoff

3/4/2004 1345 USGS 916 4.13 .26 Runoff

3/29/2004 1720 USGS 346 3.39 .09 Runoff

Appendix 5. Streamflows, and total nitrogen and total phosphorus concentrations for Beaty Creek near Jay, Oklahoma, 2002–09.

[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]

Appendix 5
Appendix 5 59

Appendix 5. Streamflows, and total nitrogen and total phosphorus concentrations for Beaty Creek near Jay, Oklahoma, 2002–09.—

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

Streamflow1

(ft3

/s)

Total nitrogen 

concentration 

(mg/L as N)2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category3

4/7/2004 0729 COT 29 3.42 0.04 Base flow

4/23/2004 1115 USGS 162 2.66 .08 Runoff

4/24/2004 1030 USGS 1,080 3.28 .46 Runoff

5/6/2004 0724 COT 186 3.32 .05 Runoff

6/10/2004 0720 COT 20 2.66 .05 Base flow

7/3/2004 1635 USGS 953 2.67 .49 Runoff

7/8/2004 0720 COT 104 3.16 .07 Runoff

8/5/2004 0729 COT 18 2.57 .09 Base flow

9/9/2004 0718 COT 7.1 2.20 .05 Base flow

10/7/2004 0720 COT 4.0 1.84 .05 Base flow

11/1/2004 1120 USGS 2,050 4.24 1.0 Runoff

11/3/2004 0738 COT 181 3.05 .10 Runoff

12/9/2004 0740 COT 144 3.67 .08 Runoff

1/6/2005 0720 COT 603 4.11 .27 Runoff

1/13/2005 1325 USGS 486 3.50 .23 Runoff

2/10/2005 0730 COT 48 3.78 .04 Base flow

3/10/2005 0730 COT 25 3.13 .04 Base flow

4/7/2005 0735 COT 142 3.28 .07 Runoff

5/12/2005 0625 COT 15 2.58 .06 Base flow

6/9/2005 0755 COT 10 2.07 .05 Base flow

6/14/2005 1030 USGS 85 1.89 .07 Runoff

7/14/2005 0725 COT 4.0 1.47 .06 Base flow

8/11/2005 0735 COT .6 .89 .04 Base flow

9/15/2005 0755 COT .1 .88 .07 Base flow

10/6/2005 0745 COT 0 .99 .05 Base flow

11/16/2005 0734 COT 2.8 1.16 .04 Base flow

12/15/2005 0750 COT 1.7 1.18 .03 Base flow

1/12/2006 0740 COT 2.1 1.37 .10 Base flow

2/9/2006 0905 COT 1.7 1.21 .03 Base flow

3/9/2006 0806 COT 2.6 1.45 .03 Base flow

4/12/2006 0738 COT 2.1 1.04 -- Base flow

4/29/2006 1210 USGS 26 1.16 .04 Runoff

5/2/2006 1125 USGS 35 1.57 .03 Runoff

5/10/2006 0810 COT 535 2.70 .23 Runoff

5/10/2006 1030 USGS 519 3.11 .21 Runoff

6/8/2006 0745 COT 7.5 --4 .04 Base flow

7/13/2006 0735 COT 0 --4 .06 Base flow

8/29/2006 1125 USGS 19 1.77 .05 Runoff

9/14/2006 0745 COT 2.8 .67 -- Base flow

11/16/2006 0835 COT .7 .91 -- Base flow

12/6/2006 0745 COT 32 3.47 -- Runoff

1/11/2007 0800 COT 16 4.07 .05 Base flow

1/23/2007 1130 USGS 159 4.02 .10 Runoff

2/8/2007 0750 COT 10 4.29 .04 Runoff
60 Nutrient Concentrations, Loads, and Yields in the Eucha-Spavinaw Basin, Arkansas and Oklahoma, 2002–09

Appendix 5. Streamflows, and total nitrogen and total phosphorus concentrations for Beaty Creek near Jay, Oklahoma, 2002–09.—

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

Streamflow1

(ft3

/s)

Total nitrogen 

concentration 

(mg/L as N)2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category3

3/7/2007 0755 COT 8.3 3.28 0.04 Base flow

4/19/2007 0754 COT 10 2.06 .04 Runoff

5/7/2007 1217 USGS 22 1.57 .04 Runoff

5/7/2007 1635 USGS 258 2.66 .21 Runoff

5/8/2007 0745 COT 406 3.58 .12 Runoff

5/8/2007 1500 USGS 355 2.88 .18 Runoff

5/29/2007 1330 USGS 21 2.70 .04 Runoff

6/7/2007 0800 COT 6.5 2.41 .04 Base flow

6/12/2007 1645 USGS 950 5.12 .89 Runoff

6/13/2007 1120 USGS 390 2.54 .13 Runoff

6/18/2007 1215 USGS 76 2.53 .06 Runoff

7/12/2007 0750 COT 12 1.81 .05 Runoff

7/24/2007 1130 USGS 9.1 1.54 .04 Base flow

8/2/2007 1530 USGS 27 1.70 .05 Runoff

8/9/2007 0800 COT 3.5 1.62 .05 Base flow

9/12/2007 1200 USGS 18 1.26 .05 Runoff

9/13/2007 0735 COT 12 1.30 .06 Runoff

10/2/2007 1325 USGS 37 1.70 .06 Runoff

10/3/2007 1020 USGS 738 3.50 .44 Runoff

10/11/2007 0742 COT 66 3.10 .05 Runoff

11/8/2007 0740 COT 37 3.40 .05 Base flow

12/11/2007 1210 USGS 429 3.50 .18 Runoff

12/18/2007 1015 COT 239 4.60 .06 Runoff

1/8/2008 1645 USGS 1,045 4.69 .58 Runoff

1/17/2008 0755 COT 197 5.00 .06 Runoff

2/14/2008 0735 COT 263 3.75 .06 Runoff

2/17/2008 1100 COT 675 3.78 .44 Runoff

3/3/2008 1230 USGS 811 3.70 .38 Runoff

3/12/2008 0730 COT 112 4.10 .05 Base flow

4/16/2008 0720 COT 139 3.40 .07 Base flow

5/7/2008 0722 COT 64 3.10 .05 Runoff

6/10/2008 1200 USGS 685 2.12 .20 Runoff

6/12/2008 0735 COT 263 2.80 .10 Runoff

7/16/2008 0730 COT 38 2.50 .06 Runoff

8/14/2008 0741 COT 60 2.80 .07 Runoff

9/5/2008 1037 USGS 51 2.60 .07 Runoff

9/11/2008 0728 COT 18 2.60 .06 Base flow

9/14/2008 1030 USGS 1,710 3.25 .52 Runoff

10/9/2008 0748 COT 22 3.00 .06 Base flow

11/6/2008 0725 COT 21 2.70 .05 Base flow

12/11/2008 0940 COT 19 2.50 .06 Runoff

1/8/2009 0803 COT 14 3.34 .05 Runoff

2/11/2009 1045 USGS 464 4.22 .27 Runoff

2/12/2009 0740 COT 333 3.70 .14 Runoff
Appendix 5 61

Appendix 5. Streamflows, and total nitrogen and total phosphorus concentrations for Beaty Creek near Jay, Oklahoma, 2002–09.—

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

Streamflow1

(ft3

/s)

Total nitrogen 

concentration 

(mg/L as N)2

Total phosphorus 

concentration 

(mg/L as P)

Flow 

category3

3/5/2009 0710 COT 15 3.00 0.05 Base flow

3/30/2009 1100 USGS 117 2.40 .06 Runoff

4/16/2009 0735 COT 86 2.70 .06 Runoff

5/4/2009 0930 USGS 344 2.50 .10 Runoff

5/8/2009 1445 USGS 758 7.27 1.10 Runoff

5/14/2009 0733 COT 113 3.50 .11 Runoff

6/11/2009 0723 COT 55 3.00 .09 Runoff

7/9/2009 0710 COT 13 2.80 .05 Base flow

8/13/2009 0730 COT 21 2.30 .07 Runoff

9/10/2009 0720 COT 386 2.77 .26 Runoff

9/10/2009 1350 USGS 216 2.51 .16 Runoff

9/22/2009 1040 USGS 662 2.83 .50 Runoff

10/8/2009 0704 COT 22 2.90 .13 Runoff

10/9/2009 1400 USGS 3,040 2.99 .86 Runoff

11/5/2009 0715 COT 92 3.46 .07 Runoff

12/9/2009 0710 COT 26 3.00 .06 Base flow

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 were substituted in the total nitrogen calculation for this sample.

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