U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2010–5120

In cooperation with the City of Dallas Water Utilities Division

Bromide, Chloride, and Sulfate Concentrations and Loads 

at U.S. Geological Survey Streamflow-Gaging Stations 

07331600 Red River at Denison Dam, 07335500 Red River 

at Arthur City, and 07336820 Red River near DeKalb, 

Texas, 2007–09
Cover: Red River downstream from Denison Dam on Lake Texoma in Texas, February 2008.
Bromide, Chloride, and Sulfate 

Concentrations and Loads at U.S. 

Geological Survey Streamflow-Gaging 

Stations 07331600 Red River at Denison 

Dam, 07335500 Red River at Arthur City, 

and 07336820 Red River near DeKalb, 

Texas, 2007–09

By Stanley Baldys III, Christopher J. Churchill, Craig A. Mobley, and David K. 

Coffman

In cooperation with the City of Dallas Water Utilities Division

Scientific Investigations Report 2010–5120

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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Suggested citation:

Baldys, Stanley, III, Churchill, C.J., Mobley, C.A., and Coffman, D.K., 2010, Bromide, chloride, and sulfate 

concentrations and loads at U.S. Geological Survey streamflow-gaging stations 07331600 Red River at Denison Dam, 

07335500 Red River at Arthur City, and 07336820 Red River near DeKalb, Texas, 2007–09: U.S. Geological Survey 

Scientific Investigations Report 2010–5120, 30 p.
iii

Contents

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

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

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

Description of Study Area ..................................................................................................................3

Data-Collection and Regression Methods ...............................................................................................4

Streamflow ............................................................................................................................................5

Continuous Water Quality ...................................................................................................................7

Sampling ................................................................................................................................................7

Sample Analysis ...................................................................................................................................8

Quality Assurance ................................................................................................................................8

Development of Regression Equations to Estimate Constituent Concentrations .....................8

Bromide, Chloride, and Sulfate Concentrations and Specific Conductance ......................................9

Bromide .................................................................................................................................................9

Chloride ................................................................................................................................................10

Sulfate ..................................................................................................................................................11

Specific Conductance .......................................................................................................................12

Daily Mean Bromide, Chloride, and Sulfate Concentrations ...............................................................13

Bromide, Chloride, and Sulfate Loads .....................................................................................................19

Summary .......................................................................................................................................................23

References ...................................................................................................................................................24

Appendix 1. Instantaneous streamflow measured at the time water-quality samples were 

collected and bromide, chloride, and sulfate concentrations and specific 

conductance measured in discrete water-quality samples collected from 

U.S. Geological Survey streamflow-gaging stations 07331600 Red River at 

Denison Dam near Denison, Texas, 07335500 Red River at Arthur City, Texas, 

and 07336820 Red River near DeKalb, Texas, 2007–09 ...............................................29

Figures 

1. Map showing contributing area for reach of the Red River from Denison Dam to 

DeKalb, Texas, and location of U.S. Geological Survey streamflow-gaging stations 

07331600 Red River at Denison Dam near Denison, Texas, 07335500 Red River at 

Arthur City, Texas, and 07336820 Red River near DeKalb, Texas .........................................2

2–4. Hydrographs showing streamflow at U.S. Geological Survey streamflow-gaging 

station: 

2. 07331600 Red River at Denison Dam near Denison, Texas, 2007–09 ..........................6

3. 07335500 Red River at Arthur City, Texas, 2007–09 ........................................................6

4. 07336820 Red River near DeKalb, Texas, 2007–09 .........................................................7

5–8. Boxplots showing distribution of: 

5. Bromide concentrations at U.S. Geological Survey streamflow-gaging 

stations 07331600 Red River at Denison Dam near Denison, Texas, 07335500 

Red River at Arthur City, Texas, and 07336820 Red River near DeKalb, Texas, 

2007–09 .................................................................................................................................9
iv

6. Chloride concentrations at U.S. Geological Survey streamflow-gaging 

stations 07331600 Red River at Denison Dam near Denison, Texas, 07335500 

Red River at Arthur City, Texas, and 07336820 Red River near DeKalb, Texas, 

2007–09 ...............................................................................................................................11

7. Sulfate concentrations at U.S. Geological Survey streamflow-gaging stations 

07331600 Red River at Denison Dam near Denison, Texas, 07335500 Red River 

at Arthur City, Texas, and 07336820 Red River near DeKalb, Texas, 2007–09 .........12

8. Specific conductance at U.S. Geological Survey streamflow-gaging stations 

07331600 Red River at Denison Dam near Denison, Texas, 07335500 Red River 

at Arthur City, Texas, and 07336820 Red River near DeKalb, Texas, 2007–09 ..........13

9–21. Graphs showing: 

9. Specific conductance at U.S. Geological Survey streamflow-gaging stations 

07331600 Red River at Denison Dam near Denison, Texas, 07335500 Red River 

at Arthur City, Texas, and 07336820 Red River near DeKalb, Texas, 2007–09 .........14

10. Bromide concentration relative to specific conductance measured in 25 

water-quality samples and best-fit regression line, U.S. Geological Survey 

streamflow-gaging station 07331600 Red River at Denison Dam near Denison, 

Texas, 2007–09 ...................................................................................................................14

11. Chloride concentration relative to specific conductance measured in 25 

water-quality samples and best-fit regression line, U.S. Geological Survey 

streamflow-gaging station 07331600 Red River at Denison Dam near Denison, 

Texas, 2007–09 ...................................................................................................................15

12. Sulfate concentration relative to specific conductance measured in 25 

water-quality samples and best-fit regression line, U.S. Geological Survey 

streamflow-gaging station 07331600 Red River at Denison Dam near Denison, 

Texas, 2007–09 ...................................................................................................................15

13. Bromide concentration relative to specific conductance measured in 25 

water-quality samples and best-fit regression line, U.S. Geological Survey 

streamflow-gaging station 07335500 Red River at Arthur City, Texas, 2007–09 ......16

14. Chloride concentration relative to specific conductance measured in 25 

water-quality samples and best-fit regression line, U.S. Geological Survey 

streamflow-gaging station 07335500 Red River at Arthur City, Texas, 2007–09 ......16

15. Sulfate concentration relative to specific conductance measured in 25 

water-quality samples and best-fit regression line, U.S. Geological Survey 

streamflow-gaging station 07335500 Red River at Arthur City, Texas, 2007–09 ......17

16. Bromide concentration relative to specific conductance measured in 25 

water-quality samples and best-fit regression line, U.S. Geological Survey 

streamflow-gaging station Red River near DeKalb, Texas, 2007–09 ........................17

17. Chloride concentration relative to specific conductance measured in 25 

water-quality samples and best-fit regression line, U.S. Geological Survey 

streamflow-gaging station 07336820 Red River near DeKalb, Texas, 2007–09 .......18

18. Sulfate concentration relative to specific conductance measured in 25 

water-quality samples and best-fit regression line, at U.S. Geological Survey 

streamflow-gaging station 07336820 Red River near DeKalb, Texas, 2007–09 .......18

19. Monthly dissolved bromide loads at U.S. Geological Survey streamflow-gaging 

stations 07331600 Red River at Denison Dam near Denison, Texas, 07335500 

Red River near Arthur City, Texas, and 07336820 Red River near DeKalb, Texas, 

2007–09 ...............................................................................................................................20
v

20. Monthly dissolved chloride loads at U.S. Geological Survey streamflowgaging stations 07331600 Red River at Denison Dam near Denison, Texas, 

07335500 Red River near Arthur City, Texas, and 07336820 Red River near 

DeKalb, Texas, 2007–09 ....................................................................................................21

21. Monthly dissolved sulfate loads at U.S. Geological Survey streamflowgaging stations 07331600 Red River at Denison Dam near Denison, Texas, 

07335500 Red River near Arthur City, Texas, and 07336820 Red River near 

DeKalb, Texas, 2007–09 ....................................................................................................21

Tables

1. Selected statistics for bromide, chloride, and sulfate concentrations and specific 

conductance at U.S. Geological Survey streamflow-gaging stations 07331600 Red 

River at Denison Dam near Denison, Texas, 07335500 Red River at Arthur City, 

Texas, and 07336820 Red River near DeKalb, Texas, 2007–09 ............................................10

2. Regression equation coefficients, adjusted R-squared values, and F-statistic 

results for bromide, chloride, and sulfate at U.S. Geological Survey streamflowgaging stations 07331600 Red River at Denison Dam near Denison, Texas, 

07335500 Red River at Arthur City, Texas, and 07336820 Red River near DeKalb, 

Texas, 2007–09 ............................................................................................................................19

3. Monthly dissolved bromide, chloride, and sulfate loads at U.S. Geological Survey 

streamflow-gaging stations 07331600 Red River at Denison Dam near Denison, 

Texas, 07335500 Red River at Arthur City, Texas, and 07336820 Red River near 

DeKalb, Texas, 2007–09 .............................................................................................................22

Conversion Factors, Datum, and Water-Quality Units

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2) 2.590 square kilometer (km2) 

Volume

acre-foot (acre-ft) 0.001233 cubic hectometer (hm3)

Flow rate

foot per second (ft/s) 0.3048 meter per second (m/s)

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

Mass

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

ton per day (ton/d) 0.9072 metric ton per day
vi

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

 °F=(1.8×°C)+32

Datum

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

Water-Quality Units

Concentrations are reported in metric units. Chemical concentrations are reported in milligrams 

per liter (mg/L). Milligrams per liter is a unit expressing the concentration of chemical 

constituents in solution as weight of solute (milligrams) per unit volume (liter) of water. For 

concentrations less than 7,000 mg/L, the numerical value of milligrams per liter is equivalent to 

the concentration in parts per million. 

Specific conductance is reported in microsiemens per centimeter at 25 degrees Celsius 

(μS/cm).
Abstract

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

of Dallas Water Utilities Division, did a study to characterize bromide, chloride, and sulfate concentrations and loads 

at three U.S. Geological Survey streamflow-gaging stations 

on the reach of the Red River from Denison Dam, which 

impounds Lake Texoma, to the U.S. Highway 259 bridge near 

DeKalb, Texas. Bromide, chloride, and sulfate concentrations 

and loads were computed for streamflow-gaging stations on 

the study reach of the Red River. Continuous streamflow and 

specific conductance data and discrete samples for bromide, 

chloride, sulfate, and specific conductance were collected 

at three main-stem streamflow-gaging stations on the Red 

River: 07331600 Red River at Denison Dam near Denison, 

Texas (Denison Dam gage), 07335500 Red River at Arthur 

City, Texas (Arthur City gage), and 07336820 Red River near 

DeKalb, Texas (DeKalb gage). At each of these streamflowgaging stations, discrete water-quality data were collected 

during January 2007–February 2009; continuous water-quality 

data were collected during March 2007–February 2009. Two 

periods of high flow resulted from floods during the study; 

floods during June–July 2007 resulted in elevated flow during 

June–September 2007 and smaller floods during March–April 

2008 resulted in elevated flow during March–April 2008. 

Bromide, chloride, and sulfate concentrations in samples 

collected at the three gages decreased downstream. Median 

bromide concentrations ranged from 0.32 milligram per liter 

at the Denison Dam gage to 0.19 milligram per liter at the 

DeKalb gage. Median chloride concentrations ranged from 

176 milligrams per liter at the Denison Dam gage to 108 milligrams per liter at the DeKalb gage, less than the 300-

milligrams per liter secondary maximum contaminant level 

established by the Texas Commission on Environmental Quality. Median sulfate concentrations ranged from 213 milligrams 

per liter at the Denison Dam gage to 117 milligrams per liter 

at the DeKalb gage, also less than the 300-milligrams per liter 

secondary maximum contaminant level. Kruskal-Wallis analyses indicated statistically significant differences among bromide, chloride, and sulfate concentrations at the three gages.

Regression equations to estimate bromide, chloride, and 

sulfate loads were developed for each of the three gages. The 

largest loads were estimated for a period of relatively large 

streamflow, June–September 2007, when about 50 percent of 

the load for the study period occurred at each gage. Adjusted 

R-squared values were largest for regression equations for the 

DeKalb gage, ranging from .957 for sulfate to .976 for chloride. Adjusted R-squared values for all regression equations 

developed to estimate loads of bromide, chloride, and sulfate 

at the three gages were .899 or larger.

Introduction 

Regional planning groups in Texas have proposed 

increasing the transfer of water from the Red River to meet 

municipal water-supply needs for the rapidly growing Dallas metropolitan area and other cities in north Texas. These 

supplies could be withdrawn from points in a reach of the Red 

River from Lake Texoma, impounded by Denison Dam, to 

several miles downstream at a point on the Red River north 

of DeKalb, Tex., at the U.S. Highway 259 bridge crossing 

(fig. 1). Municipal water suppliers, such as the City of Dallas 

Water Utilities Division, are increasingly concerned about 

the possibility of bromate concentrations in finished water 

supplies because of bromide in the raw water. When the raw 

water contains bromide, bromate (a known carcinogen) can 

form during disinfection processes that oxidize the water to 

kill pathogens (Singer, 2006; Agus and others, 2009). The 

oxidation of bromide to bromate during ozonation is influenced by factors such as the concentration of bromide, pH 

of the source water, and reaction time of the ozone used to 

disinfect the water (State of New York, Department of Health, 

2006). Bromate concentrations in finished drinking water are 

Bromide, Chloride, and Sulfate Concentrations and 

Loads at U.S. Geological Survey Streamflow-Gaging 

Stations 07331600 Red River at Denison Dam, 07335500 

Red River at Arthur City, and 07336820 Red River near 

DeKalb, Texas, 2007–09

By Stanley Baldys III, Christopher J. Churchill, Craig A. Mobley, and David K. Coffman 
2 Bromide, Chloride, and Sulfate Concentrations and Loads at USGS Streamflow-Gaging Stations, Texas

Figure 1. Contributing area for reach of the Red River from Denison Dam to DeKalb, Texas, and location of U.S. Geological Survey 

streamflow-gaging stations 07331600 Red River at Denison Dam near Denison, Texas, 07335500 Red River at Arthur City, Texas, and 

07336820 Red River near DeKalb, Texas. 

Pat 

Mayse 

Lake

Randell 

Lake

Lake

Texoma

Lake

Bonham

Hugo

Lake

McGee

Creek

Reservoir

Atoka

Reservoir

Red

River

Lake 

Crook

Sardis 

Lake

Washita River

Blue

Muddy

Boggy

Creek

Kiamichi

Bois D'Arc Creek

McGeeCreek

River

River

07331600

07335500

07336820

07331600

TEXAS

OKLAHOMA

ARKANSAS

Arthur 

City

Denison 

Dam

Bonham DeKalb

Denison

Dallas

97° 96° 95° 94°

35°

34°

33°

EXPLANATION

Contributing area boundary 

from 07331600 to 07336820

U.S. Geological Survey 

streamflow-gaging station 

and number

Study 

area

Dallas-Fort 

Worth

metroplex

LOCATION MAP

Red River 

Basin

NEW 

MEXICO Red River

Washita River

Wichita 

Falls

LOUISIANA

ARKANSAS

OKLAHOMA

TEXAS

Texas Statewide Mapping System

Projection: Albers Equal Area

Linear Unit: Meter

Datum: North American Datum of 1983

Base from:

U.S. Geological Survey digital data—Rivers,

lakes, and reservoirs

North American Atlas—Roads

Texas Natural Resources Information System—Cities

The National Atlas of the United States—

States, inset hydrography

0 30 60 MILES

0 30 60 KILOMETERS
Introduction 3

regulated by the Texas Commission on Environmental Quality 

at a maximum contaminant level of 0.01 milligram per liter 

(mg/L) (Texas Administrative Code, 2009). The U.S. Environmental Protection Agency (2006a) has developed a Stage 

2 disinfectants and disinfection byproducts (DBP) rule to 

improve drinking-water quality and provide additional protection from DBP.

Concentrations of bromide and other salinity-related 

constituents and physical properties in Lake Texoma were 

characterized by the U.S. Geological Survey (USGS) in a 

previous report (Baldys, 2009). Median bromide concentrations ranged from 0.28 mg/L in the Washita arm of Lake 

Texoma to 0.60 mg/L in the Red River arm of the lake. 

Median concentrations of chloride ranged from 122 mg/L 

in the Washita arm of Lake Texoma to 431 mg/L in the Red 

River arm of the lake. Because elevated concentrations of 

salinity-related constituents, including chloride and sulfate, 

have been measured in Lake Texoma (Atkinson and others, 

1999; Baldys, 2009), there is a concern that chloride and sulfate concentrations in the reach of the Red River downstream 

from Lake Texoma to DeKalb, Tex., might at times exceed 

applicable secondary maximum contaminant levels (SMCLs) 

of the “Texas Surface Water Quality Standards” for drinking 

water (Texas Commission on Environmental Quality, 2003).

As a companion to the study summarized in Baldys 

(2009), the USGS, in cooperation with the City of Dallas 

Water Utilities Division, did a study to characterize bromide, 

chloride, and sulfate concentrations and loads at three USGS 

streamflow-gaging stations on the reach of the Red River 

from Denison Dam, which impounds Lake Texoma, to the 

U.S. Highway 259 bridge near DeKalb, Tex. Discrete waterquality data collected during January 2007–February 2009 

and continuous water-quality data collected during March 

2007–February 2009 were evaluated at USGS streamflowgaging stations 07331600 Red River at Denison Dam near 

Denison, Tex.; 07335500 Red River at Arthur City, Tex.; and 

07336820 Red River near DeKalb, Tex. Little information is 

available regarding bromide, chloride, and sulfate concentrations and loads in that reach of the Red River. Specific conductance measured in 25 discrete water-quality samples and 

measured continuously at the three gages were used in load 

calculations. In addition to water released from Lake Texoma 

through Denison Dam, tributaries contribute a large part of the 

flow in the reach of the Red River from Denison Dam to near 

DeKalb. Because of tributary inflows, the water quality of the 

Red River in this reach might differ from the water quality of 

Lake Texoma. In addition to Lake Texoma, there are numerous reservoirs in the contributing area for the reach. Bromide, 

chloride, and sulfate concentrations and loads also could 

vary in the reach because of reservoir releases and changes in 

hydrologic conditions. 

Purpose and Scope

This report describes bromide, chloride, and sulfate 

concentrations and loads and specific conductance at three 

USGS streamflow-gaging stations on the main stem of the 

Red River between Denison Dam at Lake Texoma in Texas 

and Oklahoma and the U.S. Highway 259 bridge near DeKalb, 

Tex.: USGS streamflow-gaging stations 07331600 Red River 

at Denison Dam near Denison, Tex. (hereinafter Denison Dam 

gage); 07335500 Red River at Arthur City, Tex. (hereinafter 

Arthur City gage); and 07336820 Red River near DeKalb, 

Tex. (hereinafter DeKalb gage). At each gage, discrete waterquality data collected during January 2007–February 2009 and 

continuous water-quality data collected during March 2007–

February 2009 were evaluated. The 25 discrete environmental 

samples collected at each gage were analyzed for selected 

dissolved constituents (bromide, calcium, magnesium, potassium, sodium, carbonate, bicarbonate, chloride, and sulfate) 

and physical properties (specific conductance, pH, temperature, dissolved oxygen, and alkalinity). Bromide, the primary 

constituent of concern, and chloride, sulfate, and specific 

conductance, of secondary concern, are evaluated in light of 

the amount of streamflow associated with each sample. This 

report also documents the techniques used to collect and analyze the discrete water-quality samples collected every 2 to 6 

weeks during January 2007–February 2009 at the three gages. 

The spatial and temporal variability of bromide, chloride, 

sulfate, and specific conductance is described using summary statistics and boxplots. A Kruskal-Wallis test was used 

to determine if there were statistically significant differences 

among the bromide, chloride, and sulfate concentrations measured at each gage. Results for chloride and sulfate are compared with applicable SMCLs. Estimates of bromide, chloride, 

and sulfate loads were developed for March 2007–February 

2009 using continuously measured streamflow and waterquality properties (specific conductance, water temperature) as 

well as discrete water-quality samples analyzed for bromide, 

chloride, sulfate, and specific conductance. 

Description of Study Area

The study area is the reach of the Red River from 

Denison Dam, which impounds Lake Texoma on the TexasOklahoma border, to the U.S. Highway 259 bridge on the Red 

River near DeKalb (hereinafter the Denison Dam-DeKalb 

reach) and the contributing area to this reach (fig. 1). During 

January 2007–February 2009, releases from Lake Texoma 

accounted for 44 percent of the streamflow measured at the 

DeKalb gage. During periods of drought, most of the flow 

in the Denison Dam-DeKalb reach measured at the three 

streamflow-gaging stations (see table below) along this reach 

consists of releases from Lake Texoma (U.S. Army Corps of 

Engineers, 2009; U.S. Geological Survey, 2009). During wet 

periods, releases from Lake Texoma can vary greatly depending on reservoir management needs; the U.S. Army Corps 

of Engineers releases water from Lake Texoma to generate 

power and manage inflows. The hydrology and climatology 

of the drainage basin upstream from Lake Texoma, which has 

a major effect on the quantity and quality of flows released 

through Denison Dam, are described in Baldys (2009). 
4 Bromide, Chloride, and Sulfate Concentrations and Loads at USGS Streamflow-Gaging Stations, Texas

Description of U.S. Geological Survey streamflow-gaging stations 

on Denison Dam-DeKalb reach of Red River.

Station 

number 

(fig. 1)

Station name

Latitude 

(degrees, 

minutes, 

seconds)

Longitude 

(degrees, 

minutes, 

seconds)

07331600 Red River at Denison Dam 

near Denison, Tex.

33°49'08" 96°33'47"

07335500 Red River at Arthur City, Tex. 33°52'30" 95°30'06"

07336820 Red River near DeKalb, Tex. 33°41'02" 94°41'39"

In addition to outflows from Lake Texoma, streamflow 

in the Denison Dam-DeKalb reach of the Red River is mostly 

from tributaries in Oklahoma. Tributaries in a small part of 

Texas also confluence with the Red River and provide inflows 

to the Denison Dam-DeKalb reach (fig. 1). Annual rainfall 

increases from about 38 inches (in.) at Denison to about 46 in. 

at DeKalb (National Weather Service Weather Forecast Office, 

Dallas/Fort Worth, 2009).

Measured in miles upstream from the mouth of the Red 

River where it empties into marshlands surrounding the Mississippi and Atchafalaya Rivers, the Denison Dam gage is at 

river mile 725.5 and the DeKalb gage is at river mile 556.9; 

the Denison Dam-DeKalb reach is 168.6 river miles (U.S. 

Geological Survey, 1987). Perennial tributaries to the Red 

River in this reach include the Blue River, Muddy Boggy 

Creek, and Kiamichi River from Oklahoma. The ephemeral 

Bois D’Arc Creek is the largest tributary in Texas that contributes flow (fig. 1).

Four reservoirs on tributaries in Oklahoma to the Denison Dam-DeKalb reach have conservation pool capacities of 

more than 100,000 acre-feet (acre-ft) (U.S. Geological Survey, 

2009): (1) Atoka Reservoir (conservation pool capacity 

123,500 acre-ft); (2) McGee Creek Reservoir (conservation 

pool capacity 108,004 acre-ft); (3) Hugo Lake (conservation 

pool capacity 109,560 acre-ft); and (4) Sardis Lake (conservation pool capacity 274,333 acre-ft) (fig. 1). Atoka Reservoir, 

constructed in 1959, and McGee Creek Reservoir, constructed 

in 1978 (U.S. Geological Survey, 2009), are on the upper 

reaches of the Muddy Boggy Creek tributary. The Blue River 

and Muddy Boggy Creek enter the Red River upstream from 

the Arthur City gage (fig. 1). Although the water quality of 

Muddy Boggy Creek has not been assessed for public watersupply use by the State of Oklahoma or U.S. Environmental 

Protection Agency (2006b), historically the chemical quality of the surface water of Muddy Boggy Creek Basin was 

deemed sufficient for domestic, irrigation, and most industrial 

purposes; concentrations of dissolved solids were 100 to 

500 mg/L (Westfall and Cummings, 1963). The U.S. Environmental Protection Agency (2006b) also has not assessed 

the water quality of McGee Creek for municipal water-supply 

uses; historically the surface waters of McGee Creek contained concentrations of dissolved solids less than 100 mg/L 

(Westfall and Cummings, 1963). The drainage area for the 

Arthur City gage is 44,531 square miles (mi2), of which 5,936 

mi2 are probably noncontributing (U.S. Geological Survey, 

2009). 

Hugo Lake, located on the Kiamichi River, was constructed in 1974 and has a drainage area of 1,709 mi2

 (U.S. 

Geological Survey, 2009). Sardis Lake, located on a tributary to the Kiamichi River upstream from Hugo Lake, was 

constructed in 1982 and has a drainage area of 275 mi2. The 

Kiamichi River confluences with the Red River downstream 

from the Arthur City gage and upstream from the DeKalb 

gage (fig. 1). According to Laine and Cummings (1963), the 

water of the Kiamichi River Basin is of excellent quality for 

municipal, agricultural, and most industrial uses. On the basis 

of data collected from the Kiamichi River during December 

1998–September 2001, the Oklahoma Water Resources Board 

(2010) assigned a supported rating for water used for the 

designated beneficial use for public and private water supply. 

The drainage area at the DeKalb gage is 47,348 mi2, of which 

5,936 mi2 are probably noncontributing (U.S. Geological 

Survey, 2009). 

In addition to a relatively large reservoir near Arthur 

City (Pat Mayse Lake, capacity 122,000 acre-ft [Texas Water 

Development Board, 2009]), several relatively small reservoirs 

are in the contributing area to the Denison Dam-DeKalb reach 

on the Texas side of the Red River, including Randell Lake 

(conservation pool capacity 5,400 acre-ft [Handbook of Texas 

Online, 2009]), Lake Bonham (conservation pool capacity 

12,022 acre-ft [Texas Water Development Board, 2009]), and 

Lake Crook (conservation pool capacity 9,106 acre-ft [Texas 

Water Development Board, 2009]). Compared with releases 

from Lake Texoma and releases from reservoirs with conservation pool capacities of more than 100,000 acre-ft in the 

contributing area to the Denison Dam-DeKalb reach, releases 

from the smaller reservoirs likely have little effect on the water 

quality of the Red River in the Denison Dam-DeKalb reach 

(fig. 1). 

A summary report by the Red River Authority of Texas 

(2009) states “water resources within the Red River Basin are 

generally good and support a hearty and robust aquatic life 

with respect to stream standards. However, only 12 of the 30 

classified stream segments have been designated as useable for 

public water supply [because of] naturally occurring [large] 

concentrations of salt.” Analyses by the Red River Authority 

of Texas (2009) also indicated chloride, chlorophyll a, sulfate, 

and pH levels were increasing over time, however, only values 

for chlorophyll a exceeded State standards (Texas Commission 

on Environmental Quality, 2003).

Data-Collection and Regression 

Methods

During March 1, 2007–February 28, 2009, the USGS 

continuously monitored selected water-quality properties, 
Data-Collection and Regression Methods 5

including specific conductance, at the three streamflow-gaging 

stations on the main stem of the Red River, the Denison Dam, 

Arthur City, and DeKalb gages (fig. 1). During January 31, 

2007–February 19, 2009, discrete water-quality samples also 

were collected every 2 to 6 weeks at these gages and analyzed 

for selected dissolved constituents, including bromide, chloride, and sulfate concentrations, and for specific conductance. 

The Denison Dam gage is 1,800 feet (ft) downstream from 

the Denison Dam powerhouse. The Arthur City gage is located 

on U.S. Highway 271 bridge in Arthur City and the DeKalb 

gage is located on U.S. Highway 259 bridge, 13 miles (mi) 

north of DeKalb. Continuous water-quality data included 

hourly measurements of water temperature and specific conductance. All data from the discrete environmental samples, 

including results for quality-control samples, were published 

in the USGS National Water Information System (NWIS) 

(U.S. Geological Survey, 2009). Samples were collected at 

the Denison Dam gage by wading when possible, or from 

the cableway or at the U.S. Highway 69/75 bridge 1 mi downstream from the gage when the flow was too deep to wade. 

Samples were collected at the Arthur City and DeKalb gages 

from the U.S. Highway 271 and 259 bridges, respectively. 

All samples at the DeKalb gage were collected from the 

U.S. Highway 259 bridge; some samples at the Arthur City 

gage were collected by wading the stream. Bromide, chloride, 

and sulfate concentrations and specific conductance measured in discrete environmental samples and quality-control 

samples are listed in appendix 1. Instantaneous streamflow 

measured at the time water-quality samples were collected is 

also listed in appendix 1. All dissolved constituent and physical property data are stored in NWIS (U.S. Geological Survey, 

2009). 

Streamflow

“Streamflow” is the discharge that occurs in a natural 

channel (U.S. Geological Survey, 2008). Methods used to 

measure streamflow (discharge) amounts are described in 

detail by Rantz and others (1982) and summarized by Olson 

and Norris (2005). Streamflow measurements were made 

about every 2 months during the study at each streamflowgaging station. Stage, or gage height, is measured every 60 

minutes at the three gaging stations using a pressure transducer 

or radar equipment. The gage height represents the elevation 

of the water surface referenced to an arbitrary elevation datum. 

The gage height data are transmitted through a satellite system 

to a downlink site and then to the USGS Oklahoma Water 

Science Center, Oklahoma City, Okla., where the gage height 

information is used to determine streamflow from an established stage-discharge relation called a rating curve (Rantz and 

others, 1982). Rating curves are developed and updated for 

each station using gage height and discharge volume measurements made periodically at each gage. The gage height and 

streamflow information are stored in NWIS (U.S. Geological 

Survey, 2009).

Streamflow measured at the Denison Dam gage was

 characterized by two flow regimes. During cycles of normal 

daily electrical power generation at Denison Dam, streamflow 

varied from small base flows (periods of no power generation) 

of about 60 cubic feet per second (ft3/s), with average depths 

less than 1.0 ft and velocities less than 1 foot per second (ft/s), 

to large flows (periods of power generation) of 15,000 to 

33,000 ft3/s, with average depths 8 to 12 ft and velocities 

more than 6 ft/s. The transition between the two flow regimes 

was usually abrupt. Two periods of high flow in the Denison 

Dam-DeKalb reach (figs. 2–4) resulted from floods during 

the study. Floods during June–July 2007 resulted in elevated 

flow during June–September 2007; smaller floods during 

March–April 2008 resulted in elevated flow during March–

April 2008. Water flowed over the spillway at Denision Dam 

in July 2007 for only the third time since Denison Dam was 

constructed. The maximum daily mean streamflows measured 

at the Denison Dam gage during the 2007 and 2008 floods 

were 38,400 ft3/s on July 16, 2007, and 21,300 ft3/s on April 

20, 2008 (U.S. Geological Survey, 2009). Twelve of the 25 

discrete samples at the Denison Dam gage were collected 

when mean instantaneous streamflow ranged from 77 ft3/s 

(November 4, 2008) to 480 ft3/s (February 26, 2008) (appendix 

1). Four samples were collected during the elevated streamflow associated with the 2007 floods; mean instantaneous 

streamflow for the four samples ranged from about 30,000 to 

34,000 ft3/s.

Streamflow patterns at the Arthur City gage during the 

study were generally similar to streamflow patterns at the 

Denison Dam gage. The lowest base flows sampled varied 

from about 300 to about 700 ft3/s; these periods of low flow 

occurred in March 2007 and again during October 2008–

January 2009 (fig. 3). The maximum daily mean streamflows 

at the Arthur City gage during the 2007 and 2008 floods were 

80,800 ft3/s on July 12, 2007, and 70,000 ft3/s on March 20, 

2008 (U.S. Geological Survey, 2009). The large increases in 

streamflow in the Red River from the Denison Dam gage to 

the Arthur City gage during the 2007 and 2008 floods largely 

resulted from reservoir releases on tributaries downstream 

from Denison Dam. 

Samples collected at the DeKalb gage in November 

and December 2008 were collected when some of the lowest 

daily mean streamflows were measured during the entire 

sample collection period (fig. 4). In contrast to the relatively 

small instantaneous streamflows of 5,110 ft3/s or less measured for 12 discrete samples, mean instantaneous streamflow for four samples collected during the elevated streamflow associated with the 2007 and 2008 floods ranged 

from about 40,000 to 69,000 ft3/s (appendix 1). Maximum 

daily mean streamflow measured at the DeKalb gage during the 2007 and 2008 floods were 83,500 ft3

/s on July 14, 

2007, and 97,800 ft3/s on March 21, 2008 (U.S. Geological 

Survey, 2009). The large range of streamflow in the Denison Dam-DeKalb reach during the study made it possible 

to collect samples representing a wide range of hydrologic 

conditions.
6 Bromide, Chloride, and Sulfate Concentrations and Loads at USGS Streamflow-Gaging Stations, Texas

Figure 2. Hydrograph showing streamflow at U.S. Geological Survey streamflow-gaging station 07331600 Red River at Denison Dam 

near Denison, Texas, 2007–09. 

Figure 3. Hydrograph showing streamflow at U.S. Geological Survey streamflow-gaging station 07335500 Red River at Arthur City, 

Texas, 2007–09. 

Water-quality sample collected

JAN

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MAR

2007 2008 2009

0

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10,000

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DAILY MEAN STREAMFLOW, IN CUBIC FEET PER SECOND

Water-quality sample collected

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MAR

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SEPT

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2007 2008 2009

DAILY MEAN STREAMFLOW, IN CUBIC FEET PER SECOND

0

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Data-Collection and Regression Methods 7

Continuous Water Quality

Water temperature and specific conductance data were 

collected hourly at the three streamflow-gaging stations using 

multiprobe sondes encased in flow-through wells (Wagner and 

others, 2006) suspended in the stream. The flow-through well 

at the Denison Dam gage was mounted on the south bank, 

whereas the flow-through wells at the Arthur City and DeKalb 

gages were suspended in the main thalweg of the stream from 

the bridge on which each of these gages is installed. Field procedures, calibration of the continuous water-quality monitors, 

and record computation and review methods followed Wagner 

and others (2006).

Sampling

Water-quality samples were collected at each gage following guidelines documented in the USGS “National Field 

Manual for the Collection of Water-Quality Data” (U.S. 

Geological Survey, variously dated). Samples were collected 

every 2 to 6 weeks using isokinetic depth-integrated sampling 

and non-isokinetic sampling methods (Lane and others, 2003). 

Discrete samples were generally collected within a span of 24 

hours at all three gages. Three types of samplers were used for 

the study—an isokinetic depth-integrator sampler (US D–95) 

for streamflow velocities exceeding 1.7 ft/s, a hand-held 

weighted-bottle sampler for streamflow velocities less than 1.7 

ft/s and depths too deep to wade, and an open-mouth bottle for 

depths too shallow to use either the isokinetic or the hand-held 

weighted-bottle sampler. Teflon bottles were used with the 

three types of samplers. For the isokinetic sampling, aliquots 

(small volumes of water; for this study, about 1 liter) were 

collected from stream verticals selected by dividing the stream 

into equal segments known as equal-width increments (EWI). 

Non-isokinetic sampling with a weighted-bottle sampler also 

was used to collect sample aliquots from stream segments 

determined by EWI. Using the EWI selection process, the 

width of the stream typically was divided into a minimum 

of 10 equal increments. Field measurements were made in 

each increment, and a water sample was withdrawn from the 

increment and placed in a polyethylene churn for compositing 

with waters withdrawn from the other sections. Once water 

from all sections was placed in the churn, the water was mixed 

(composited) and aliquots were withdrawn for analysis by the 

USGS National Water Quality Laboratory (NWQL), Denver, 

Colo. The EWI method for isokinetic and non-isokinetic sampling methods allowed a representative sample to be collected 

at each of the three gaging stations and accounted for tributary 

inflows which were not 100-percent mixed with the upstream 

flow of the Red River.

Figure 4. Hydrograph showing streamflow at U.S. Geological Survey streamflow-gaging station 07336820 Red River near DeKalb, 

Texas, 2007–09. 

Water-quality sample collected

JAN

MAR

MAY

JULY

SEPT

NOV

JAN

MAR

MAY

JULY

SEPT

NOV

JAN

MAR

2007 2008 2009

DAILY MEAN STREAMFLOW, IN CUBIC FEET PER SECOND

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

100,000

110,000
8 Bromide, Chloride, and Sulfate Concentrations and Loads at USGS Streamflow-Gaging Stations, Texas

Sample Analysis

Water samples were sent to the NWQL for analyses 

to determine concentrations of common ions including 

dissolved bromide, chloride, and sulfate. The analytical 

method used for these constituents was ion chromatography 

(Fishman and Friedman, 1989; Fishman, 1993). Preparation and pretreatment of the samples by the NWQL followed 

guidelines documented in Fishman and Friedman (1989). 

Bromide, chloride, and sulfate analyses were done on filtered 

water samples that were not acidified. 

Quality Assurance

Quality-assurance procedures outlined in Wagner 

and others (2006) were followed in the collecting and 

processing of continuous water-quality data for temperature 

and specific conductance. The temperature probe on each 

sonde was checked by comparing its temperature readings 

to those from a National Institute of Standards and Technology (NIST) certified thermometer. Specific conductance 

probes were calibrated with standards traceable to NIST 

electrolytic conductivity standard reference solutions. Data 

from cross-sectional surveys made at the time of sample 

collection indicated that the monitor sondes were placed 

at locations representative of flows in the stream cross 

section.

Quality-assurance procedures outlined in the “National 

Field Manual for the Collection of Water-Quality Data” 

(U.S. Geological Survey, variously dated) were followed 

for collecting and processing water-quality samples. Qualitycontrol samples were collected to evaluate potential bias 

and variability or contamination introduced during sample 

collection, processing, or laboratory analysis. Three samples 

of deionized (DI) water used to clean sampling equipment 

(DI samples) were submitted to the NWQL and analyzed 

for dissolved bromide and selected constituents. DI samples 

were submitted for associated environmental samples collected on December 4, 2007, June 19, 2008, and January 23, 

2009. Dissolved bromide concentrations measured in the 

three DI samples were less than the laboratory reporting level 

of 0.02 mg/L. Major ion data were evaluated to ensure the 

cation-anion balances were consistently within 5 percent. 

On May 8, 2007, a field-equipment blank was collected 

with the environmental sample at the Arthur City gage; 

bromide, chloride, and sulfate concentrations measured in 

the field-equipment blank were less than their applicable 

laboratory reporting levels (appendix 1). Bromide, chloride, 

and sulfate concentrations in field-replicate samples were 

similar to concentrations in environmental samples; percent 

differences of less than 5 percent were measured for fieldreplicate samples collected on February 26 and July 24, 2008, 

at the Denison Dam gage, on May 8, 2007, at the Arthur 

City gage, and on January 21, 2009, at the DeKalb gage 

(appendix 1). 

Development of Regression Equations to 

Estimate Constituent Concentrations

Using hourly streamflow and specific conductance 

measurements and discrete water-quality data collected every 

2 to 6 weeks and analyzed for bromide, chloride, and sulfate 

concentrations and for specific conductance, regression equations were derived to estimate daily mean bromide, chloride, 

and sulfate concentrations. The daily mean concentrations 

in turn were used to compute daily loads of bromide, chloride, and sulfate. Keller and others (1988) describes specific 

conductance as “a measure of the ability of a water to conduct 

an electrical current and thus it is related to the types and concentrations of major ions in solution . . . consequently, specific 

conductance can be used for approximating the concentrations of dissolved solids and major ions dissolved in water.” 

Keller and others (1988) computed loads for chloride, sulfate, 

and dissolved solids for October 1970–April 1988 at selected 

streamflow-gaging stations in the Red River Basin upstream 

from Lake Texoma for the Red River Chloride Control Project, 

using the same multi-variable regression equations used in this 

study. The same methods also were used to compute loads for 

chloride, sulfate, and dissolved solids for many sites published 

in the USGS Texas Water Science Center annual water-data 

reports (U.S. Geological Survey, 1987–2002). The Texas 

Water Science Center developed a load computation program 

(F.L. Andrews, U.S. Geological Survey, written commun., 

2000) to automate the computation procedure used for sites in 

Texas. 

Daily mean values of streamflow and estimated instantaneous (hourly) constituent concentrations derived from the 

relation of instantaneous (hourly) specific conductance values 

to concentrations of bromide, chloride, and sulfate measured 

in discrete samples were used to compute monthly loads of 

bromide, chloride, and sulfate.

Whereas daily mean streamflow data were available from 

continuous streamflow records, periodic (rather than daily) 

constituent concentration data were available from the discrete 

samples collected every 2 to 6 weeks. Because bromide, chloride, and sulfate concentrations were highly correlated with 

specific conductance and continuous specific conductance 

data were generally available for the three streamflow-gaging 

stations, it was possible to develop regression equations that 

relate constituent concentrations to specific conductance to 

obtain estimates of daily mean constituent concentrations.

Using methods described in Keller and others (1988), linear regression equations derived for each gage are of the form:

Ci = B0 + B1(SCi) + B2(SCi)

2

, (1)

where

Ci = instantaneous constituent concentration, in 

milligrams per liter;

SCi = instantaneous specific conductance, in 

microsiemens per centimeter at 25 degrees 

Celsius; and
Bromide, Chloride, and Sulfate Concentrations and Specific Conductance 9

B0, B1, B2 = regression coefficients computed from data 

collected at the three gaging stations during 

March 2007–February 2009.

In a linear regression analysis, the R-squared (R2), 

adjusted R2, and standard error of regression are useful statistics for evaluating the goodness of fit, that is, how well the 

regression equation fits the data. The R2 value is the coefficient 

of determination, and it is used to describe the proportion of 

the total sample variability in the response explained by the 

regression model. The adjusted R2 statistic compensates for 

this by assessing a “penalty” for the number of explanatory 

variables in the model; adding additional explanatory variables 

increases the value of the adjusted R2 only when the predictive 

capability of the model increases. The standard error of regression is an estimate of the predictive accuracy of the regression 

equation; choosing a model with the highest adjusted R2 value 

is equivalent to choosing a model with the lowest mean standard error (Helsel and Hirsch, 2002; Iman and Conover, 1983). 

Bromide, Chloride, and Sulfate 

Concentrations and Specific 

Conductance

Discrete water-quality samples were collected every 2 to 

6 weeks at the Denison Dam, Arthur City, and DeKalb gages 

and analyzed for bromide, chloride, and sulfate concentrations and for specific conductance. The results for the 25 

discrete samples collected at each gage, including streamflow 

measured at the time the samples were collected, are listed in 

appendix 1.

Bromide

The distribution of bromide data collected at each gage 

is summarized by boxplots (fig. 5). Boxplots provide visual 

summaries of the center of the data (median), the variation 

or spread (interquartile range), the skewness (relative size 

of box halves), and presence or absence of extreme values 

(Helsel and Hirsch, 2002). The median bromide concentration for the 25 samples collected at each gage in the Denison 

Dam-DeKalb reach decreased from upstream to downstream. 

Median bromide concentrations at the Denison Dam, Arthur 

City, and DeKalb gages were 0.32, 0.26, and 0.19 mg/L, 

respectively (table 1). Not only did the median bromide concentration measured at each gage decrease in the downstream 

direction, but the overall spread of bromide concentrations at 

each gage decreased as well (fig. 5). The Kruskal-Wallis test is 

a nonparametric test that can be used to determine the general 

equivalence of groups of data (Helsel and Hirsch, 2002). A 

Kruskal-Wallis test was used to determine if there were statistically significant differences among the bromide concentrations measured at the Denison Dam, Arthur City, and DeKalb 

gages. The null hypothesis of no statistically significant 

Figure 5. Distribution of bromide concentrations at U.S. Geological Survey streamflow-gaging stations 07331600 Red River at Denison 

Dam near Denison, Texas, 07335500 Red River at Arthur City, Texas, and 07336820 Red River near DeKalb, Texas, 2007–09. BROMIDE CONCENTRATION, IN MILLIGRAMS PER LITER

0.6

0.5

0.4

0.3

0.2

0.1

0

STATION NUMBER

07331600 07335500 07336820

(25)

(25)

(25)

EXPLANATION 

Number of data points

Data value 1.5 to 3.0 times the interquartile range outside the box

Largest data value within 1.5 times the interquartile range above the box

75th percentile)

Median (50th percentile)

25th percentile)

Smallest data value within 1.5 times the interquartile range below the box

(25)

Interquartile

range
10 Bromide, Chloride, and Sulfate Concentrations and Loads at USGS Streamflow-Gaging Stations, Texas

difference among the bromide concentrations measured at the 

three gages was rejected; the difference among the bromide 

concentrations from each of the three gages was statistically 

significant (p <.01). 

The maximum bromide concentration of 0.52 mg/L 

(table 1) was in the January 31, 2007, sample at the Denison 

Dam gage, the first sample collected for the study; instantaneous streamflow was 4,500 ft3

/s (appendix 1). The minimum 

bromide concentration for a discrete sample was 0.03 mg/L, 

first measured in a sample collected at the DeKalb gage on 

February 1, 2007, when instantaneous streamflow was 20,800 

ft3/s. A bromide concentration of 0.03 mg/L was measured 

again in the March 26, 2008, sample at the DeKalb gage, 

when instantaneous streamflow was 36,900 ft3/s. The largest 

instantaneous streamflows measured at the time the discrete 

water-quality samples were collected all occurred during the 

June–July 2007 floods. At the Denison Dam gage, the bromide 

concentration was 0.36 mg/L in the sample collected on June 

14, 2007, when instantaneous streamflow was 33,600 ft3/s. 

At the Arthur City gage, the bromide concentration was 0.15 

mg/L in the sample collected on July 11, 2007, when instantaneous streamflow was 72,400 ft3

/s. At the DeKalb gage, the 

bromide concentration was 0.14 mg/L in the sample collected 

on July 11, 2007, when instantaneous streamflow was 69,100 

ft3/s. Changes in bromide concentrations in the Denison DamDeKalb reach were evident (appendix 1) after the June–July 

2007 floods, which resulted in large releases from Denison 

Dam. The daily mean streamflow on the day when a sample 

was collected at each gage in July 2007 was 32,500 ft3/s at 

Denison Dam gage (fig. 2), 70,800 ft3/s at the Arthur City gage 

(fig. 3), and 68,600 ft3/s at the DeKalb gage (fig. 4). Prior to 

July 2007, the most recent daily mean streamflow greater than 

30,000 ft3/s was recorded at the Denison Dam gage on March 

10, 2001 (32,400 ft3/s). Daily mean streamflows of 70,000 

ft3/s or more were recorded on 4 days (July 11–14) in July 

2007 at the Arthur City gage. Prior to July 2007, daily mean 

streamflow most recently approached 70,000 ft3/s at the Arthur 

City gage on January 4, 2005 (65,400 ft3/s). Prior to July 2007, 

the most recent large streamflow recorded at the Arthur City 

gage was 42,400 ft3/s on January 15, 2007.

Releases from Lake Texoma and other reservoirs in the 

study area for management of floodwaters from the two large 

streamflow events had pronounced effects on bromide concentrations during the study period. Bromide concentrations 

measured at the Denison Dam gage were 0.47 to 0.52 mg/L 

for samples collected during January 31–May 9, 2007, before 

the June–July 2007 floods. After the sample collected on May 

9, 2007, bromide concentrations of 0.40 mg/L or greater were 

not measured again until one of the last samples for this study 

was collected on January 22, 2009. During July–August 2007, 

bromide concentrations at the Denison Dam gage ranged from 

0.10 to 0.25 mg/L. Although the March–April 2008 floods had 

little effect on bromide concentrations measured in releases 

from Denison Dam, the lowest bromide concentrations in 

samples collected at the Arthur City and DeKalb gages were 

measured during the March–April 2008 floods (appendix 1). 

The March–April 2008 floods had a relatively greater effect on 

reservoir releases and hydrologic conditions in the contributing area to the Denison-DeKalb reach downstream from Lake 

Texoma than on reservoir releases from Lake Texoma, resulting in measurable changes in bromide concentrations at the 

Arthur City and DeKalb gages compared with concentrations 

at the Denison Dam gage. Bromide concentrations in samples 

collected at the three streamflow-gaging stations do not appear 

to vary seasonally.

Chloride

The distribution of chloride data collected at each gage 

is summarized by boxplots (fig. 6). The median chloride 

concentration for the 25 samples collected at each gage 

Table 1. Selected statistics for bromide, chloride, and sulfate concentrations and specific conductance at U.S. Geological Survey 

streamflow-gaging stations 07331600 Red River at Denison Dam near Denison, Texas, 07335500 Red River at Arthur City, Texas, and 

07336820 Red River near DeKalb, Texas, 2007–09.

[Bromide, chloride, and sulfate concentrations in milligrams per liter; specific conductance in microsiemens per centimeter at 25 degrees Celsius]

Constituent or 

physical property1

07331600 07335500 07336820

MaximumMinimum

Mean Median Maximum

Minimum

Mean Median Maximum

Minimum

Mean Median

Bromide 0.52 0.10 0.33 0.32 0.49 0.05 0.26 0.26 0.45 0.03 0.20 0.19

Chloride 464 103 230 176 431 9.80 165 137 400 5.37 120 108

Sulfate 293 95.1 213 213 268 20.7 154 155 250 11.7 119 117

Specific conductance 2,190 780 1,370 1,250 2,030 230 1,090 1,020 1,940 145 847 814

1

 For all values, n = 25. 
Bromide, Chloride, and Sulfate Concentrations and Specific Conductance 11

decreased from upstream to downstream, from 176 mg/L at 

the Denison Dam gage, to 137 mg/L at the Arthur City gage, 

to 108 mg/L at the DeKalb gage (table 1) and were less than 

the SMCL of 300 mg/L (Texas Commission on Environmental 

Quality, 2003). Similar to the medians, the spread of chloride 

concentrations measured at each gage decreased downstream 

(fig. 6). A Kruskal-Wallis test of chloride concentrations indicated a statistically significant (p <.01) difference among the 

chloride concentrations measured at each of the three gages. 

The maximum chloride concentration of 464 mg/L 

(table 1) was in the March 13, 2007, sample at the Denison 

Dam gage; instantaneous streamflow was 168 ft3/s (appendix 1). The minimum chloride concentration was 5.37 mg/L 

at the DeKalb gage on March 26, 2008; instantaneous streamflow was 36,900 ft3

/s. The chloride concentration associated with the largest instantaneous streamflow measurement 

(72,400 ft3/s) was 126 mg/L in the July 11, 2007, sample at the 

Arthur City gage. 

Chloride concentrations for the first four samples collected at the Denison Dam gage before the June–July 2007 

floods were more than 440 mg/L, exceeding the SMCL of 

300 mg/L for chloride (Texas Commission on Environmental Quality, 2003). After the June–July 2007 floods, chloride 

concentrations ranged from 103 to 138 mg/L in samples collected at the Denison Dam gage during August 2007–January 

2008. Despite steadily increasing during the last 11 months 

of data collection (April 2008–February 2009), chloride 

concentrations at each gage were still less than 300 mg/L at 

the end of the data-collection period. During the March–April 

2008 floods, chloride concentrations decreased at the Arthur 

City and DeKalb gages, then steadily increased until the end 

of the data-collection period. Chloride concentrations at the 

Denison Dam gage after the March–April 2008 floods did not 

decrease as much as concentrations at the two downstream 

gages. Chloride concentrations in the Denison Dam-DeKalb 

reach varied as a result of reservoir releases and changing 

hydrologic conditions; seasonal variations in chloride concentrations were not apparent.

Sulfate

Similar to bromide and chloride concentrations, the 

median sulfate concentration at each gage decreased downstream, from 213 mg/L at the Denison Dam gage, to 155 

mg/L at the Arthur City gage, to 117 mg/L at the DeKalb 

gage (table 1) and were less than the SMCL of 300 mg/L 

(Texas Commission on Environmental Quality, 2003). Not 

only did the median sulfate concentration measured at 

each gage decrease downstream, the spread of sulfate concentrations at each gage also decreased downstream (fig. 7). 

A Kruskal-Wallis test of sulfate concentrations indicated a 

statistically significant (p <.01) difference among the sulfate 

concentrations measured at each of the three gages. 

Figure 6. Distribution of chloride concentrations at U.S. Geological Survey streamflow-gaging stations 07331600 Red River at Denison 

Dam near Denison, Texas, 07335500 Red River at Arthur City, Texas, and 07336820 Red River near DeKalb, Texas, 2007–09. 

*

*

*

*

CHLORIDE CONCENTRATION, IN MILLIGRAMS PER LITER

600

500

400

300

200

100

0

STATION NUMBER 

07331600 07335500 07336820

(25) (25) (25)

EXPLANATION 

*

Number of data points

Data value greater than 3.0 times

the interquartile range outside the box

Data value 1.5 to 3.0 times the interquartile range outside the box

Largest data value within 1.5 times the interquartile range above the box

75th percentile

Median (50th percentile

25th percentile

Smallest data value within 1.5 times the interquartile range below the box

(25)

Interquartile

range
12 Bromide, Chloride, and Sulfate Concentrations and Loads at USGS Streamflow-Gaging Stations, Texas

The maximum sulfate concentration was 293 mg/L 

(table 1), less than the SMCL of 300 mg/L for sulfate (Texas 

Commission on Environmental Quality, 2003). The sulfate 

concentration of 293 mg/L was measured in the March 13, 

2007, sample at the Denison Dam gage; instantaneous streamflow was 168 ft3

/s (appendix 1). The minimum sulfate concentration was 11.7 mg/L in the March 26, 2008, sample at 

the DeKalb gage; instantaneous streamflow was 36,900 ft3/s. 

The sulfate concentration associated with the largest instantaneous streamflow measurement (72,400 ft3

/s) was 94.2 

mg/L in the July 11, 2007, sample at the Arthur City gage 

(appendix 1).

The effect of the June–July 2007 and March–April 2008 

floods on sulfate concentrations in the Denison Dam-DeKalb 

reach was similar to the effect of these floods on bromide and 

chloride concentrations. The June–July 2007 floods resulted in 

smaller sulfate concentrations in samples at the Denison Dam 

gage; concentrations decreased by more than 50 percent, from 

235 to 293 mg/L measured during January–June 2007 prior to 

the floods, to 95.1 mg/L measured on August 30, 2007, after 

the floods. Decreases in sulfate concentrations after the June–

July 2007 floods also were observed in samples collected at 

the Arthur City and DeKalb gages. The March–April 2008 

floods affected sulfate concentrations measured in samples 

collected at the Arthur City and DeKalb gages more than the 

floods affected the sulfate concentrations measured in samples 

collected at the Denison Dam gage. Changes in streamflow, 

including large floods and subsequent releases from the reservoirs, likely caused most of the variability in sulfate concentrations; sulfate concentrations did not appear to vary seasonally 

during the study period. 

Specific Conductance

Median specific conductance in the Denison DamDeKalb reach decreased from upstream to downstream, 

from 1,250 microsiemens per centimeter at 25 degrees Celsius 

(μS/cm) at the Denison Dam gage, to 1,020 μS/cm at the 

Arthur City gage, to 814 μS/cm at the DeKalb gage (table 1). 

The spread of specific conductance values measured at each 

gage also decreased downstream (fig. 8). A Kruskal-Wallis 

test of specific conductance values indicated a statistically 

significant (p <.01) difference among the specific conductance 

values measured at each of the three gages. 

The maximum specific conductance was 2,190 μS/cm 

(table 1) at the Denison Dam gage on January 31, 2007; 

instantaneous streamflow was 4,500 ft3/s (appendix 1). The 

minimum specific conductance was 145 μS/cm at the DeKalb 

gage on March 26, 2008; instantaneous streamflow was 

36,900 ft3/s. The specific conductance associated with the 

largest instantaneous streamflow measurement (72,400 ft3/s) 

was 775 μS/cm in the July 11, 2007, sample at the Arthur City 

gage. Similar to bromide, chloride, and sulfate concentrations, 

Figure 7. Distribution of sulfate concentrations at U.S. Geological Survey streamflow-gaging stations 07331600 Red River at Denison 

Dam near Denison, Texas, 07335500 Red River at Arthur City, Texas, and 07336820 Red River near DeKalb, Texas, 2007–09. SULFATE CONCENTRTION, IN MILLIGRAMS PER LITER

350

300

250

200

150

100

50

0

STATION NUMBER

07331600 07335500 07336820

(25)

(25)

(25)

EXPLANATION 

Number of data points

Largest data value within 1.5 times the interquartile range above the box

75th percentile

Median (50th percentile

25th percentile

Smallest data value within 1.5 times the interquartile range below the box

(25)

Interquartile

range
Daily Mean Bromide, Chloride, and Sulfate Concentrations 13

specific conductance values were affected by reservoir 

releases. Some of the smallest specific conductance values 

were measured during April–September 2007 when large reservoir releases occurred. Specific conductance values did not 

appear to vary on a seasonal basis (fig. 9).

Daily Mean Bromide, Chloride, and 

Sulfate Concentrations

Regression equations that relate constituent concentrations to specific conductance were used to obtain estimates 

of daily mean constituent concentrations. Data collected at 

the three gaging stations during March 2007–February 2009 

were used in equation 1 to develop the regression equations 

(table 2). The regression equations derived from discrete 

(every 2 to 6 weeks) and continuous (hourly) measurements 

of specific conductance and discrete measurements of constituents of concern (bromide, chloride, and sulfate) were 

used to estimate daily mean bromide, chloride, and sulfate 

concentrations. The daily mean bromide, chloride, and sulfate 

concentrations then were used to develop regression equations 

to compute estimated bromide, chloride, and sulfate loads for 

each of the three gages.

Bromide, chloride, or sulfate concentration relative to 

specific conductance and the adjusted R2 value (Helsel and 

Hirsch, 2002, p. 313) for the best-fit regression equation for 

each constituent at each gage are shown in figures 10–18. 

Adjusted R2 values were largest for regression equations 

for the DeKalb gage, ranging from .957 for sulfate to .976 

for chloride (table 2). Adjusted R2 values for all regression 

equations were .899 or larger, indicating that the equations 

explained 89.9 percent or more of the variance in the data for 

each constituent at each gage, one indicator of the goodnessof-fit of the best-fit regression equation. The F-test, used to 

determine whether all independent variables together significantly contribute to the prediction of the dependent variable, 

yielded statistically significant F-statistics for each constituent 

at each gage for the best-fit models (table 2) (Kleinbaum and 

Kupper, 1978). A large adjusted R2 or significant F-statistic 

does not guarantee that the data have been fitted well (Helsel 

and Hirsch, 2002). Residual plots (Weisberg, 2005) used to 

graphically depict goodness-of-fit and additional diagnostics 

(not shown) were used to confirm the goodness-of-fit of the 

regression equations. Although all regression equations fit the 

data well, the adjusted R2 and F-statistic (table 2) indicate that 

the equations for data collected at the DeKalb gage describe 

the data slightly better compared with the equations for data 

collected at the Denison Dam and Arthur City gages. 

Much of the variability in the Denison Dam gage data for 

bromide, chloride, and sulfate resulted from samples collected 

during June–August 2007, which coincided with some of the 

largest discharge releases from Denison Dam during the study 

Figure 8. Distribution of specific conductance at U.S. Geological Survey streamflow-gaging stations 07331600 Red River at Denison 

Dam near Denison, Texas, 07335500 Red River at Arthur City, Texas, and 07336820 Red River near DeKalb, Texas, 2007–09. 

STATION NUMBER

07331600 07335500 07336820

2,500

2,000

1,500

1,000

500

0

SPECIFIC CONDUCTANCE, IN MICROSIEMENS PER 

(25)

(25)

(25)

 CENTIMETER AT 25 DEGREES CELSIUS

EXPLANATION 

Number of data points

Data value 1.5 to 3.0 times the interquartile range outside the box

Largest data value within 1.5 times the interquartile range above the box

75th percentile

Median (50th percentile

25th percentile

Smallest data value within 1.5 times the interquartile range below the box

(25)

Interquartile

range
14 Bromide, Chloride, and Sulfate Concentrations and Loads at USGS Streamflow-Gaging Stations, Texas

Figure 9. Specific conductance at U.S. Geological Survey streamflow-gaging stations 07331600 Red River at Denison Dam near 

Denison, Texas, 07335500 Red River at Arthur City, Texas, and 07336820 Red River near DeKalb, Texas, 2007–09. 

Figure 10. Bromide concentration relative to specific conductance measured in 25 water-quality samples and best-fit regression line, 

U.S. Geological Survey streamflow-gaging station 07331600 Red River at Denison Dam near Denison, Texas, 2007–09. 

0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

Jan 2007

Mar 2007

May 2007

July 2007

Sept 2007

Nov 2007

Jan 2008

Mar 2008

May 2008

July 2008

Sept 2008

Nov 2008

Jan 2009

Mar 2009

SPECIFIC CONDUCTANCE, IN MICROSIEMENS PER CENTIMETER

AT 25 DEGREES CELSIUS

DATE

Staon 07331600

Staon 07335500

Staon 07336820

2,200

 y = -0.0000001x2 + 0.0005424x - 0.20538

R2 = .928

0

0.1

0.2

0.3

0.4

0.5

0.6

0 500 1,000 1,500 2,000 2,500

BROMIDE CONCENTRATION, IN MILLIGRAMS PER LITER

SPECIFIC CONDUCTANCE, IN MICROSEIMENS PER CENTIMETER AT 25 DEGREES CELSIUS
Daily Mean Bromide, Chloride, and Sulfate Concentrations 15

Figure 11. Chloride concentration relative to specific conductance measured in 25 water-quality samples and best-fit regression line, 

U.S. Geological Survey streamflow-gaging station 07331600 Red River at Denison Dam near Denison, Texas, 2007–09. 

Figure 12. Sulfate concentration relative to specific conductance measured in 25 water-quality samples and best-fit regression 

line, U.S. Geological Survey streamflow-gaging station 07331600 Red River at Denison Dam near Denison, Texas, 2007–09. 

0

50

100

150

200

250

300

350

0 500 1,000 1,500 2,000 2,500

SULFATE CONCENTRATION, IN MILLIGRAMS PER LITER

SPECIFIC CONDUCTANCE, IN MICROSEIMENS PER CENTIMETER AT 25 DEGREES CELSIUS

 y = -0.0001106x2 + 0.45551x - 186

R2 = .929

 y = 0.000062x2 + 0.0878x - 17.4

R2 = .948

0

50

100

150

200

250

300

350

400

450

500

0 500 1,000 1,500 2,000 2,500

CHLORIDE CONCENTRATION, IN MILLIGRAMS PER LITER

SPECIFIC CONDUCTANCE, IN MICROSEIMENS PER CENTIMETER AT 25 DEGREES CELSIUS
16 Bromide, Chloride, and Sulfate Concentrations and Loads at USGS Streamflow-Gaging Stations, Texas

Figure 13. Bromide concentration relative to specific conductance measured in 25 water-quality samples and best-fit regression line, 

U.S. Geological Survey streamflow-gaging station 07335500 Red River at Arthur City, Texas, 2007–09. 

Figure 14. Chloride concentration relative to specific conductance measured in 25 water-quality samples and best-fit regression line, 

U.S. Geological Survey streamflow-gaging station 07335500 Red River at Arthur City, Texas, 2007–09. 

0

0.1

0.2

0.3

0.4

0.5

0.6

0 500 1,000 1,500 2,000 2,500

BROMIDE CONCENTRATION, IN MILLIGRAPMS PER LITER

SPECIFIC CONDUCTANCE, IN MICROSEIMENS PER CENTIMETER AT 25 DEGREES CELSIUS

 y = -0.00000003x2 + 0.0002876x - 0.0206

R2 = .938

0

50

100

150

200

250

300

350

400

450

500

0 500 1,000 1,500 2,000 2,500

CHLORIDE CONCENTRATION, IN MILLIGRAMS PER LITER

SPECIFIC CONDUCTANCE, IN MICROSEIMENS PER CENTIMETER AT 25 DEGREES CELSIUS

 y = 0.00007612x2 + 0.05483x + 4.9

R2 = .958
Daily Mean Bromide, Chloride, and Sulfate Concentrations 17

Figure 15. Sulfate concentration relative to specific conductance measured in 25 water-quality samples and best-fit regression line, 

U.S. Geological Survey streamflow-gaging station 07335500 Red River at Arthur City, Texas, 2007–09. 

Figure 16. Bromide concentration relative to specific conductance measured in 25 water-quality samples and best-fit regression line, 

U.S. Geological Survey streamflow-gaging station Red River near DeKalb, Texas, 2007–09. 

0

50

100

150

200

250

300

0 500 1,000 1,500 2,000 2,500

SULFATE CONCENTRATION, IN MILLIGRAMS PER LITER

SPECIFIC CONDUCTANCE, IN MICROSEIMENS PER CENTIMETER AT 25 DEGREES CELSIUS

 y = -0.00003878x2 + 0.22861x - 43.39

R2 = .908

0

0.1

0.2

0.3

0.4

0.5

0 500 1,000 1,500 2,000 2,500

BROMIDE CONCENTRATION, IN MILLIGRAMS PER LITER

SPECIFIC CONDUCTANCE, IN MICROSEIMENS PER CENTIMETER AT 25 DEGREES CELSIUS

 y = -0.00000001x2 + 0.0002527x - 0.00638

R2 = .975
18 Bromide, Chloride, and Sulfate Concentrations and Loads at USGS Streamflow-Gaging Stations, Texas

Figure 17. Chloride concentration relative to specific conductance measured in 25 water-quality samples and best-fit regression line, 

U.S. Geological Survey streamflow-gaging station 07336820 Red River near DeKalb, Texas, 2007–09. 

Figure 18. Sulfate concentration relative to specific conductance measured in 25 water-quality samples and best-fit regression line, at 

U.S. Geological Survey streamflow-gaging station 07336820 Red River near DeKalb, Texas, 2007–09. 

0

50

100

150

200

250

300

350

400

450

0 500 1,000 1,500 2,000 2,500

CHLORIDE CONCENTRATION, IN MILLIGRAMS PER LITER

SPECIFIC CONDUCTANCE, IN MICROSEIMENS PER CENTIMETER AT 25 DEGREES CELSIUS

 y = 0.00008236x2 + 0.04232x + 9.98

R2 = .978

0

50

100

150

200

250

300

0 500 1,000 1,500 2,000 2,500

SULFATE CONCENTRATION, IN MILLIGRAMS PER LITER

SPECIFIC CONDUCTANCE, IN MICROSEIMENS PER CENTIMETER AT 25

 y = -0.00002983x2 + 0.19709x - 21.388

R2 = .961
Bromide, Chloride, and Sulfate Loads 19

period (figs. 2–4). The amount of variability in the data at the 

Arthur City and DeKalb gages downstream was less than the 

amount of variability in the data collected at Denison Dam 

gage. Cation-anion balances for the samples collected at the 

Denison Dam gage during the June–August 2007 period of 

elevated streamflow are within 3 percent, indicating that 

chloride and sulfate concentrations for these samples are 

acceptable for inclusion in the regression analysis. Bromide 

concentrations measured in samples collected at the Denison 

Dam gage during this time included several low concentrations, including the lowest concentration (0.10 mg/L in the 

August 9, 2007, sample). These low concentrations do not 

warrant exclusion from regression analyses as outliers; there 

is nothing to indicate they resulted from errors introduced 

during sample collection or analysis. On the contrary, the 

low concentrations are consistent with dilution resulting 

from a large influx of runoff to Lake Texoma. Baldys (2009) 

documented decreases in bromide concentrations throughout 

Lake Texoma after the large inflows that began in late June 

2007. Constituent concentrations from samples collected 

during the period of elevated streamflow resulting from the 

March–April 2008 floods were similar compared with concentrations measured in samples collected during the months 

before and after the flooding occurred. The March–April 

2008 floods resulted in less inflow to Lake Texoma compared 

with the June–July 2007 floods. During the June–July 2007 

floods, inflows to Lake Texoma measured at gaging stations 

07316000 Red River near Gainesville, Tex. (725,040 ft3/s) and 

07331000 Washita River near Dickson, Okla. (532,920 ft3/s) 

totaled 1,257,960 ft3/s; inflows resulting from the March–April 

2008 floods measured at stations 07316000 (68,101 ft3/s) and 

07331000 (144,375 ft3/s) totaled 212,476 ft3/s (U.S. Geological Survey, 2009).

Bromide, Chloride, and Sulfate Loads

Daily mean bromide, chloride, and sulfate concentrations were used with streamflow in daily load computations. 

Dissolved bromide, chloride, and sulfate loads during March 

1, 2007–February 28, 2009, were computed for the Denison 

Dam, Arthur City, and DeKalb gages in a two-step process. 

Using equation 2 (Keller and others, 1988), daily loads for 

the constituents of interest were computed from daily mean 

streamflow, instantaneous concentration for constituent of 

Table 2. Regression equation1 coefficients, adjusted R-squared values, and F-statistic results for bromide, chloride, and sulfate at U.S. 

Geological Survey streamflow-gaging stations 07331600 Red River at Denison Dam near Denison, Texas, 07335500 Red River at Arthur 

City, Texas, and 07336820 Red River near DeKalb, Texas, 2007–09.

[<, less than]

Station

number

(fig. 1)

Constituent B0 B1 B2 R-squared Adjusted 

R-squared 

Standard 

error of 

regression

F-statistic

F-statistic 

attained 

significance 

(p-value)2

07331600 Bromide -0.20538 0.0005424 -0.0000001 0.928 0.921 0.029 141.35 <.01

Chloride -17.4 .0878 .000062 .948 .943 27.972 200.27 <.01

Sulfate -186 .45551 -.0001106 .929 .923 14.895 144.79 <.01

07335500 Bromide -.0206 .0002876 -.00000003 .938 .932 .023 165.72 <.01

Chloride 4.9 .05483 .00007612 .958 .954 19.217 251.12 <.01

Sulfate -43.39 .22861 -.00003878 .908 .899 17.178 108.07 <.01

07336820 Bromide -.00638 .0002527 -.00000001 .975 .972 .017 425.12 <.01

Chloride 9.98 .04232 .00008236 .978 .976 14.856 482.76 <.01

Sulfate -21.388 .19709 -.00002983 .961 .957 12.691 268.8 <.01

1 Ci

 = B0 + B1(SCi) + B2(SCi)

2

, 

where

Ci = instantaneous constituent concentration, in milligrams per liter;

SC i = instantaneous specific conductance, in microsiemens per centimeter at 25 degrees Celsius; and

B0, B1,B2 = regression coefficients.

2 p-values less than or equal to .05 are considered statistically significant.
20 Bromide, Chloride, and Sulfate Concentrations and Loads at USGS Streamflow-Gaging Stations, Texas

interest as the estimated daily mean concentration (from equation 1), and a conversion factor: 

Li = Qi x Ci x K, (2)

where

Li = daily constituent load, in tons per day;

Qi = daily mean streamflow, in cubic feet per second;

Ci = instantaneous concentration, in milligrams per liter, 

computed from equation 1 (assumption is made that 

instantaneous concentration is satisfactory estimate of 

daily mean concentration); and

K = 0.0027, a units conversion factor, in tons per day per 

cubic foot per second-milligrams per liter.

Monthly bromide, chloride, and sulfate loads for each 

site (table 3) were computed by summing the individual daily 

loads computed from equations 1 and 2. Bromide loads were 

larger at the Arthur City gage compared with those measured 

at either the upstream Denison Dam gage or the downstream 

DeKalb gage. During March 2007–February 2009, the total 

bromide loads computed at the Denison Dam, Arthur City, and 

DeKalb gages were 4,186, 5,044, and 4,963 tons, respectively. 

The smaller total bromide load computed at the DeKalb gage 

compared with the total bromide load computed at the Arthur 

City gage was a result of lower bromide concentrations at the 

DeKalb gage compared with concentrations at the Arthur City 

gage, despite larger streamflow at the DeKalb gage compared 

with streamflow at the Arthur City gage. The computed loads 

were largest (fig. 19) for those periods when streamflow in the 

Red River was relatively large (figs. 2–4). At the Denison Dam 

and Arthur City gages, 53 percent of the total bromide load 

during March 2007–February 2009 was recorded during just 4 

months, June–September 2007, compared with 50 percent at 

the DeKalb gage.

Chloride and sulfate loads at the three streamflow gages 

followed the same pattern observed for bromide loads, with 

the largest loads at the Arthur City gage (figs. 20–21). During March 2007–February 2009, total chloride loads computed at the Denison Dam, Arthur City, and DeKalb gages 

were 2,912,000, 3,213,000, and 2,830,000 tons, respectively 

(table 3). The total sulfate loads computed for the Denison 

Dam, Arthur City, and DeKalb gages during March 2007–

February 2009 were 2,639,000, 3,023,000, and 2,954,000 tons, 

respectively (table 3). Similar to the computed bromide loads, 

computed chloride and sulfate loads were largest for those 

time periods when streamflow in the Red River was relatively 

large. About 50 percent of the total chloride and sulfate loads 

computed at each of the gages during March 2007–February 

2009 occurred during June–September 2007.

Figure 19. Monthly dissolved bromide loads at U.S. Geological Survey streamflow-gaging stations 07331600 Red River at Denison Dam 

near Denison, Texas, 07335500 Red River near Arthur City, Texas, and 07336820 Red River near DeKalb, Texas, 2007–09. 

0

100

200

300

400

500

600

700

800

900

1,000

Mar 2007

Apr 2007

May 2007

June 2007

July 2007

Aug 2007

Sept 2007

Oct 2007

Nov 2007

Dec 2007

Jan 2008

Feb 2008

Mar 2008

Apr 2008

May 2008

June 2008

July 2008

Aug 2008

Sept 2008

Oct 2008

Nov 2008

Dec 2008

Jan 2009

Feb 2009

MONTHLY BROMIDE LOAD, IN TONS

DATE

Staon 07331600

Staon 07335500

Staon 07336820
Bromide, Chloride, and Sulfate Loads 21

Figure 20. Monthly dissolved chloride loads at U.S. Geological Survey streamflow-gaging stations 07331600 Red River at Denison Dam 

near Denison, Texas, 07335500 Red River near Arthur City, Texas, and 07336820 Red River near DeKalb, Texas, 2007–09. 

Figure 21. Monthly dissolved sulfate loads at U.S. Geological Survey streamflow-gaging stations 07331600 Red River at Denison Dam 

near Denison, Texas, 07335500 Red River near Arthur City, Texas, and 07336820 Red River near DeKalb, Texas, 2007–09. 

0

100,000

200,000

300,000

400,000

500,000

600,000

700,000

Mar 2007

Apr 2007

May 2007

June 2007

July 2007

Aug 2007

Sept 2007

Oct 2007

Nov 2007

Dec 2007

Jan 2008

Feb 2008

Mar 2008

Apr 2008

May 2008

June 2008

July 2008

Aug 2008

Sept 2008

Oct 2008

Nov 2008

Dec 2008

Jan 2009

Feb 2009

MONTHLY CHLORIDE LOAD, IN TONS

DATE

Staon 07331600

Staon 07335500

Staon 07336820

0

100,000

200,000

300,000

400,000

500,000

600,000

700,000

Mar 2007

Apr 2007

May 2007

June 2007

July 2007

Aug 2007

Sept 2007

Oct 2007

Nov 2007

Dec 2007

Jan 2008

Feb 2008

Mar 2008

Apr 2008

May 2008

June 2008

July 2008

Aug 2008

Sept 2008

Oct 2008

Nov 2008

Dec 2008

Jan 2009

Feb 2009

MONTHLY SULFATE LOAD, IN TONS

DATE

Staon 07331600

Staon 07335500

Staon 07336820
22 Bromide, Chloride, and Sulfate Concentrations and Loads at USGS Streamflow-Gaging Stations, Texas

Table 3. Monthly dissolved bromide, chloride, and sulfate loads at U.S. Geological Survey streamflow-gaging stations 07331600 

Red River at Denison Dam near Denison, Texas, 07335500 Red River at Arthur City, Texas, and 07336820 Red River near DeKalb, Texas, 

2007–09.

[cubic foot per second-days, volume of water represented by flow of 1 cubic foot per second for 24 hours times number of days in each month (1 cubic foot per 

second-day is 86,000 cubic feet; average flow in cubic feet per second for each month is volume of flow in cubic foot per second-days)]

Month Year

Streamflow 

(cubic 

foot per 

seconddays)

Dissolved 

bromide 

load 

(tons)

Dissolved 

chloride 

load 

(tons)

Dissolved 

sulfate 

load 

(tons)

Month Year

Streamflow 

(cubic 

foot per 

seconddays)

Dissolved 

bromide 

load 

(tons)

Dissolved 

chloride 

load 

(tons)

Dissolved 

sulfate 

load 

(tons)

07331600 Red River at Denison Dam near Denison, Texas 

(Denison Dam gage)

07335500 Red River near Arthur City, Texas 

(Arthur City gage)

Mar. 2007 42,253 58 55,409 31,867 Mar. 2007 54,097 56 49,004 33,943

Apr. 2007 278,363 375 345,316 211,448 Apr. 2007 443,376 417 364,529 249,119

May 2007 376,108 495 434,535 286,824 May 2007 715,716 630 493,567 383,474

June 2007 640,177 783 616,211 476,367 June 2007 1,186,351 896 652,648 542,584

July 2007 985,514 803 491,170 529,581 July 2007 1,721,345 950 515,562 575,935

Aug. 2007 951,880 453 253,973 297,304 Aug. 2007 1,134,315 570 291,081 342,147

Sept. 2007 407,881 167 95,456 108,181 Sept. 2007 482,308 237 119,409 141,933

Oct. 2007 88,939 42 23,447 27,522 Oct. 2007 134,666 71 37,108 43,008

Nov. 2007 71,722 38 21,066 25,121 Nov. 2007 86,059 53 30,138 32,937

Dec. 2007 72,322 39 21,416 25,599 Dec. 2007 104,095 58 31,260 35,256

Jan. 2008 83,461 46 25,797 30,930 Jan. 2008 87,328 56 32,313 34,697

Feb. 2008 78,395 47 26,397 31,677 Feb. 2008 175,289 71 37,259 40,034

Mar. 2008 110,003 54 32,568 34,746 Mar. 2008 587,963 120 58,994 48,066

Apr. 2008 355,900 261 149,307 174,538 Apr. 2008 685,560 324 173,602 190,315

May 2008 153,621 109 62,035 73,125 May 2008 235,459 145 82,631 89,261

June 2008 88,775 67 38,354 44,596 June 2008 147,117 80 42,514 48,393

July 2008 106,377 82 47,757 54,917 July 2008 106,272 76 46,542 46,936

Aug. 2008 64,060 52 30,862 34,857 Aug. 2008 85,352 58 34,696 35,630

Sept. 2008 85,112 76 46,487 50,342 Sept. 2008 71,478 55 35,921 34,225

Oct. 2008 17,518 17 10,897 11,177 Oct. 2008 25,661 21 14,657 13,198

Nov. 2008 7,644 8 5,171 5,085 Nov. 2008 13,520 10 6,236 6,160

Dec. 2008 11,045 12 7,761 7,481 Dec. 2008 14,129 11 6,658 6,536

Jan. 2009 42,601 46 31,562 29,511 Jan. 2009 31,928 28 20,305 17,434

Feb. 2009 50,762 56 39,298 35,770 Feb. 2009 57,704 51 36,702 31,489

TOTAL 5,170,431 4,186 2,912,252 2,638,567 TOTAL 8,387,087 5,044 3,213,336 3,022,709
Summary 23

Month Year

Streamflow 

(cubic foot 

per seconddays)

Dissolved 

bromide 

load 

(tons)

Dissolved 

chloride 

load 

(tons)

Dissolved 

sulfate 

load 

(tons)

7336820 Red River near DeKalb, Texas 

(DeKalb gage)

Mar. 2007 69,497 70 56,160 40,349

Apr. 2007 433,530 363 287,434 208,106

May 2007 812,951 513 333,196 305,783

June 2007 1,343,790 895 590,054 533,336

July 2007 1,924,771 836 408,116 511,801

Aug. 2007 1,386,607 495 225,264 297,791

Sept. 2007 596,495 256 121,997 156,768

Oct. 2007 170,769 89 45,951 54,709

Nov. 2007 92,567 62 36,620 38,095

Dec. 2007 145,955 66 33,427 40,308

Jan. 2008 124,572 62 31,866 37,862

Feb. 2008 300,702 79 38,067 44,248

Mar. 2008 1,033,014 147 70,013 65,278

Apr. 2008 1,111,569 307 139,859 175,810

May 2008 369,877 185 94,912 113,768

June 2008 195,345 125 77,468 75,651

July 2008 119,423 81 48,397 49,956

Aug. 2008 98,121 61 35,092 37,583

Sept. 2008 127,857 88 52,289 53,750

Oct. 2008 74,659 44 24,047 26,970

Nov. 2008 29,157 18 10,211 11,200

Dec. 2008 30,444 18 10,458 11,320

Jan. 2009 69,821 41 23,025 25,462

Feb. 2009 99,608 62 35,853 37,709

TOTAL 10,761,099 4,963 2,829,778 2,953,614

Table 3. Monthly dissolved bromide, chloride, and sulfate loads 

at U.S. Geological Survey streamflow-gaging stations 07331600 

Red River at Denison Dam near Denison, Texas, 07335500 Red 

River at Arthur City, Texas, and 07336820 Red River near DeKalb, 

Texas, 2007–09—Continued.

Summary

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

with the City of Dallas Water Utilities Division, did a study to 

characterize bromide, chloride, and sulfate concentrations and 

loads at three USGS streamflow-gaging stations on the reach 

of the Red River from Denison Dam, which impounds Lake 

Texoma, to the U.S. Highway 259 bridge near DeKalb, Texas. 

During March 1, 2007–February 28, 2009, the USGS 

continuously monitored selected water-quality properties, 

including specific conductance, at three USGS streamflowgaging stations on the main stem of the Red River: 07331600 

Red River at Denison Dam near Denison, Texas (Denison 

Dam gage), 07335500 Red River at Arthur City, Texas (Arthur 

City gage), and 07336820 Red River near DeKalb, Texas 

(DeKalb gage). During January 31, 2007–February 19, 2009, 

discrete water-quality samples also were collected every 2 to 

6 weeks at these gages and analyzed for selected dissolved 

constituents, including bromide, chloride, and sulfate concentrations, and for specific conductance. Two periods of 

high flow resulted from floods during the study; floods 

during June–July 2007 resulted in elevated flow during June–

September 2007 and smaller floods during March–April 2008 

resulted in elevated flow during March–April 2008. 

Bromide, chloride, and sulfate concentrations in samples 

collected at the three gages decreased downstream. Median 

bromide concentrations ranged from 0.32 mg/L at the Denison 

Dam gage to 0.19 mg/L at the DeKalb gage. Median chloride 

concentrations ranged from 176 mg/L at the Denison Dam 

gage to 108 mg/L at the DeKalb gage and were less than the 

300-mg/L secondary maximum contaminant level established 

by the Texas Commission on Environmental Quality. Median 

sulfate concentrations ranged from 213 mg/L at the Denison 

Dam gage to 117 mg/L at the DeKalb gage; these values also 

were less than the 300-mg/L secondary maximum contaminant 

level. Kruskal-Wallis analyses indicated statistically significant differences among the bromide, chloride, and sulfate 

concentrations measured at each gage.

During the study, bromide, chloride, and sulfate concentrations and loads and specific conductance values were 

affected by high flow during June–September 2007 and 

March–April 2008. Changes in bromide, chloride, and sulfate 

concentrations in the Denison Dam-DeKalb reach of the Red 

River were evident after the June–July 2007 floods, which 

resulted in large releases from Denison Dam. Bromide concentrations measured at the Denison Dam gage during January 

31–May 9, 2007, were 0.47 to 0.52 mg/L. After the May 9, 

2007 sample, bromide concentrations 0.40 mg/L or greater 

were not measured again until one of the last samples for this 

study was collected on January 22, 2009. During July–August 

2007, bromide concentrations at the Denison Dam gage 

ranged from 0.10 to 0.25 mg/L. 

Regression equations to compute bromide, chloride, 

and sulfate loads were developed for each of the three gages. 

The regression equations were developed using the same 

methods used by the Red River Chloride Control Project 
24 Bromide, Chloride, and Sulfate Concentrations and Loads at USGS Streamflow-Gaging Stations, Texas

and the USGS Texas Water Science Center to analyze data 

for previous reports. To aid in the evaluation of each regression equation, adjusted R-squared (R2

) and F-statistic values 

were computed. The regression equations for the DeKalb 

gage had the largest adjusted R2 values for each regression 

equation, ranging from .957 for sulfate to .976 for chloride. Although all regression equations fit the data well, the 

adjusted R2 and F-statistic values indicate that equations for 

data collected at the DeKalb gage describe the data slightly 

better compared with equations for data collected at the 

Denison Dam and Arthur City gages. Adjusted R2 values for 

all regression equations developed to estimate loads were .899 

or larger, indicating that the equations explained 89.9 percent 

or more of the variance in the data for each constituent at each 

gage.

Bromide loads were larger at the Arthur City gage 

compared with those measured at either the upstream Denison 

Dam gage or the downstream DeKalb gage. During March 

2007–February 2009, the total bromide loads computed at the 

Denison Dam, Arthur City, and DeKalb gages were 4,186, 

5,044, and 4,963 tons, respectively. The computed loads were 

largest for those periods when streamflow in the Red River 

was relatively large. At the Denison Dam and Arthur City 

gages, 53 percent of the total bromide load during March 

2007–February 2009 was recorded during 4 months, June–

September 2007, compared with 50 percent at the DeKalb 

gage. Chloride and sulfate loads at the three gages followed 

the same pattern observed for bromide loads, with the largest 

loads at the Arthur City gage. During March 2007–February 2009, total chloride loads computed at the Denison Dam, 

Arthur City, and DeKalb gages were 2,912,000, 3,213,000, 

and 2,830,000 tons, respectively, and total sulfate loads were 

2,639,000, 3,023,000, and 2,954,000 tons, respectively.

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Appendix 1

Appendix 1
Blank Page
Appendix 1 29

Appendix 1. Instantaneous streamflow measured at the time water-quality samples were collected and bromide, chloride, and 

sulfate concentrations and specific conductance measured in discrete water-quality samples collected from U.S. Geological Survey 

streamflow-gaging stations 07331600 Red River at Denison Dam near Denison, Texas, 07335500 Red River at Arthur City, Texas, and 

07336820 Red River near DeKalb, Texas, 2007–09—Continued.

Station Sample 

collection date

Mean instantaneous discharge 

(ft3/s)

Bromide 

(mg/L)

Chloride 

(mg/L)

Sulfate 

(mg/L)

Specific 

conductance 

(μS/cm) 

Sample 

type

07331600 1/31/2007 4,500 0.52 460 283 2,190 E

07331600 3/13/2007 168 .50 464 293 2,160 E

07331600 4/11/2007 11,500 .51 445 277 2,120 E

07331600 5/9/2007 310 .47 450 274 2,120 E

07331600 6/14/2007 33,600 .36 384 235 1,550 E

07331600 7/12/2007 32,800 .25 226 166 1,290 E

07331600 8/9/2007 30,400 .10 117 107 847 E

07331600 8/30/2007 32,100 .18 103 95.1 780 E

07331600 10/24/2007 2,780 .22 112 136 898 E

07331600 11/26/2007 340 .25 126 166 986 E

07331600 12/17/2007 150 .25 129 164 1,000 E

07331600 1/9/2008 450 .26 138 177 1,050 E

07331600 2/26/2008 480 .29 153 194 1,130 E

07331600 2/26/2008 480 .30 153 194 -- REP

07331600 3/27/2008 10,800 .32 172 210 1,220 E

07331600 4/23/2008 16,000 .32 164 219 1,220 E

07331600 5/21/2008 10,400 .31 167 213 1,210 E

07331600 6/11/2008 190 .30 160 210 1,170 E

07331600 7/24/2008 10,400 .32 176 210 1,220 E

07331600 7/24/2008 10,400 .31 176 211 -- REP

07331600 8/28/2008 260 .33 173 191 1,250 E

07331600 9/17/2008 170 .35 193 223 1,310 E

07331600 10/8/2008 120 .37 225 231 1,400 E

07331600 11/4/2008 77 .38 235 251 1,460 E

07331600 12/10/2008 124 .39 248 256 1,500 E

07331600 1/22/2009 1,300 .41 262 266 1,580 E

07331600 2/19/2009 10,700 .40 259 267 1,620 E

07335500 1/31/2007 6,700 .29 228 154 1,230 E

07335500 3/13/2007 1,060 .33 269 187 1,520 E

07335500 4/11/2007 11,900 .49 431 268 2,030 E

07335500 5/8/2007 12,700 .21 168 116 900 E

07335500 5/8/2007 12,700 .22 167 116 -- REP

07335500 5/8/2007 12,700 <.02 <.12 <.18 -- FBLK

07335500 6/13/2007 36,900 .37 367 228 1,810 E

07335500 7/11/2007 72,400 .15 126 92.2 775 E

07335500 8/8/2007 35,000 .17 134 106 894 E

07335500 8/30/2007 34,000 .17 96.3 94.4 759 E

07335500 10/23/2007 5,030 .21 107 122 876 E

07335500 11/27/2007 6,070 .24 118 155 950 E

07335500 12/18/2007 5,000 .18 83.1 106 752 E

07335500 1/9/2008 2,040 .23 118 147 964 E

07335500 2/27/2008 3,170 .23 99.4 128 878 E

Appendix 1. Instantaneous streamflow measured at the time water-quality samples were collected and bromide, chloride, and 

sulfate concentrations and specific conductance measured in discrete water-quality samples collected from U.S. Geological Survey 

streamflow-gaging stations 07331600 Red River at Denison Dam near Denison, Texas, 07335500 Red River at Arthur City, Texas, and 

07336820 Red River near DeKalb, Texas, 2007–09.

[ft3/s, cubic feet per second; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; --, not measured; <, not detected at laboratory 

reporting level. Sample type: E, environmental; REP, field replicate; FBLK, field equipment blank]
30 Bromide, Chloride, and Sulfate Concentrations and Loads at USGS Streamflow-Gaging Stations, Texas

Appendix 1. Instantaneous streamflow measured at the time water-quality samples were collected and bromide, chloride, and 

sulfate concentrations and specific conductance measured in discrete water-quality samples collected from U.S. Geological Survey 

streamflow-gaging stations 07331600 Red River at Denison Dam near Denison, Texas, 07335500 Red River at Arthur City, Texas, and 

07336820 Red River near DeKalb, Texas, 2007–09—Continued.

Station Sample 

collection date

Mean instantaneous discharge 

(ft3/s)

Bromide 

(mg/L)

Chloride 

(mg/L)

Sulfate 

(mg/L)

Specific 

conductance 

(μS/cm) 

Sample 

type

07335500 3/26/2008 16,700 0.05 9.79 20.7 230 E

07335500 4/23/2008 26,400 .27 137 183 1,050 E

07335500 5/21/2008 4,090 .26 124 157 995 E

07335500 6/11/2008 2,840 .20 80.1 94.2 766 E

07335500 7/24/2008 2,970 .31 165 198 1,180 E

07335500 8/28/2008 2,250 .27 149 175 1,070 E

07335500 9/17/2008 997 .25 127 142 1,020 E

07335500 10/8/2008 663 .31 196 182 1,310 E

07335500 11/4/2008 360 .33 187 191 1,240 E

07335500 12/10/2008 415 .29 179 181 1,230 E

07335500 1/21/2009 1,100 .32 210 215 1,400 E

07335500 2/18/2009 2,240 .34 211 219 1,390 E

07336820 2/1/2007 20,800 .03 19.3 20.9 190 E

07336820 3/12/2007 2,700 .42 357 240 1,810 E

07336820 4/10/2007 15,900 .45 400 250 1,940 E

07336820 5/8/2007 20,000 .06 27.9 24.6 267 E

07336820 6/13/2007 35,000 .32 293 196 1,550 E

07336820 7/11/2007 69,100 .14 119 85.7 772 E

07336820 8/8/2007 44,000 .14 104 81.6 716 E

07336820 8/31/2007 41,800 .14 74.2 72.6 610 E

07336820 10/23/2007 5,110 .19 96.8 111 821 E

07336820 11/27/2007 6,100 .23 113 151 952 E

07336820 12/18/2007 7,750 .13 52.5 72.5 537 E

07336820 1/9/2008 3,550 .18 92.8 123 802 E

07336820 2/27/2008 13,000 .09 33.1 45.5 334 E

07336820 3/26/2008 36,900 .03 5.37 11.7 145 E

07336820 4/24/2008 39,500 .18 86.7 117 718 E

07336820 5/21/2008 6,690 .15 66.2 85.6 600 E

07336820 6/11/2008 3,530 .22 113 154 952 E

07336820 7/24/2008 3,700 .26 136 173 1,040 E

07336820 8/28/2008 4,940 .23 119 147 932 E

07336820 9/18/2008 2,610 .23 113 136 892 E

07336820 10/8/2008 3,180 .20 109 115 814 E

07336820 11/4/2008 1,340 .22 99.2 134 986 E

07336820 12/10/2008 1,030 .25 113 143 1,040 E

07336820 1/21/2009 2,000 .25 148 162 1,020 E

07336820 1/21/2009 2,000 .25 147 161 -- REP

07336820 2/18/2009 4,300 .19 108 115 736 E

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