Cover photos: Top photo is aerial view of the Flint River flood plain near Owens Crossroads, Alabama; 

photograph taken by Tennessee Valley Press, Inc., Decatur, Ala. Bottom photo is the Flint River at 

Highway 72, Alabama, courtesy of Susan Weber, Flint River Conservation Association.
Water Quality of the Flint River Basin, Alabama and 

Tennessee, 1999-2000

By ANNE B. HOOS, JERRY W. GARRETT, and RODNEY R. KNIGHT

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 01-4185

Nashville, Tennessee

2002
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

Any use of trade, product, or firm name in this report is for identification

purposes only and does not constitute endorsement by the

U.S. Geological Survey.

For additional information write to: Copies of this report may be purchased from:

District Chief U.S. Geological Survey

U.S. Geological Survey Branch of Information Services

640 Grassmere Park, Suite 100 Box 25286

Nashville, Tennessee 37211 Denver, Colorado 80225-0286

Information regarding the National Water-Quality Assessment (NAWQA) Program is available 

on the Internet via the World Wide Web. You may connect to the NAWQA home page at:

http://water.usgs.gov/nawqa/nawqa_home.html
The U.S. Geological Survey (USGS) is committed to serve the Nation with accurate and timely scientific information that helps enhance and protect the 

overall quality of life, and facilitates effective management of water, biological, energy, and mineral 

resources. Information on the quality of the Nation’s 

water resources is of critical interest to the USGS 

because it is so integrally linked to the long-term 

availability of water that is clean and safe for drinking 

and recreation and that is suitable for industry, irrigation, and habitat for fish and wildlife. Escalating population growth and increasing demands for the multiple 

water uses make water availability, now measured in 

terms of quantity and quality, even more critical to the 

long-term sustainability of our communities and ecosystems.

The USGS implemented the National WaterQuality Assessment (NAWQA) Program to support 

national, regional, and local information needs and 

decisions related to water-quality management and 

policy. Shaped by and coordinated with ongoing 

efforts of other Federal, State, and local agencies, the 

NAWQA Program is designed to answer: What is the 

condition of our Nation’s streams and ground water? 

How are the conditions changing over time? How do 

natural features and human activities affect the quality 

of streams and ground water, and where are those 

effects most pronounced? By combining information 

on water chemistry, physical characteristics, stream 

habitat, and aquatic life, the NAWQA Program aims to 

provide science-based insights for current and emerging water issues and priorities. NAWQA results can 

contribute to informed decisions that result in practical 

and effective water-resource management and strategies that protect and restore water quality.

Since 1991, the NAWQA Program has implemented interdisciplinary assessments in more than 50 

of the Nation’s most important river basins and aquifers, referred to as Study Units. Collectively, these 

Study Units account for more than 60 percent of the 

overall water use and population served by public 

water supply, and are representative of the Nation’s 

major hydrologic landscapes, priority ecological 

resources, and agricultural, urban, and natural sources 

of contamination. 

Each assessment is guided by a nationally consistent study design and methods of sampling and 

analysis. The assessments thereby build local knowledge about water-quality issues and trends in a particular stream or aquifer while providing an 

understanding of how and why water quality varies 

regionally and nationally. The consistent, multi-scale 

approach helps to determine if certain types of waterquality issues are isolated or pervasive, and allows 

direct comparisons of how human activities and natural processes affect water quality and ecological health 

in the Nation’s diverse geographic and environmental 

settings. Comprehensive assessments on pesticides, 

nutrients, volatile organic compounds, trace metals, 

and aquatic ecology are developed at the national 

scale through comparative analysis of the Study-Unit 

findings. 

The USGS places high value on the communication and dissemination of credible, timely, and relevant science so that the most recent and available 

knowledge about water resources can be applied in 

management and policy decisions. We hope this 

NAWQA publication will provide you the needed 

insights and information to meet your needs, and 

thereby foster increased awareness and involvement in 

the protection and restoration of our Nation’s waters. 

The NAWQA Program recognizes that a 

national assessment by a single program cannot 

address all water-resource issues of interest. External 

coordination at all levels is critical for a fully integrated understanding of watersheds and for costeffective management, regulation, and conservation of 

our Nation’s water resources. The Program, therefore, 

depends extensively on the advice, cooperation, and 

information from other Federal, State, interstate, 

Tribal, and local agencies, non-government organizations, industry, academia, and other stakeholder 

groups. The assistance and suggestions of all are 

greatly appreciated.

Robert M. Hirsch

Associate Director for Water

FOREWORD

Foreword iii
Contents v

CONTENTS

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

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

Purpose and Scope .......................................................................................................................................................... 2

Acknowledgments .......................................................................................................................................................... 5

Study Objectives and Approach ............................................................................................................................................ 5

Design of Monitoring Program....................................................................................................................................... 5

Watershed Inputs............................................................................................................................................................. 7

Hydrologic Conditions .......................................................................................................................................................... 7

Water Quality of the Flint River Basin .................................................................................................................................. 7

Pesticides ....................................................................................................................................................................... 7

Comparison of Watershed Inputs to Detection Frequency, Instream Concentrations, and Yields............................. 9

Variation of Concentrations with Season and Streamflow......................................................................................... 9

Comparison of Concentrations with Criteria to Protect Aquatic Life ....................................................................... 14

Spatial Variation of Concentrations During Base Flow ............................................................................................. 15

Fecal-Indicator Bacteria.................................................................................................................................................. 15

Variation of Concentrations with Streamflow and Turbidity..................................................................................... 19

Spatial Variation of Concentrations During Base Flow ............................................................................................. 20

Nutrients ......................................................................................................................................................................... 23

Variation of Concentrations with Season and Streamflow......................................................................................... 23

Spatial Variation of Concentrations During Base Flow ............................................................................................. 25

Relation of Storm Transport of Selected Pesticides in the Flint River Basin to Concentrations 

in the Source for Drinking Water for the City of Huntsville, Alabama................................................................... 25

Summary ............................................................................................................................................................................... 30

References Cited.................................................................................................................................................................... 31

Appendix A. Methods for Estimating Watershed Input and Instream Yield of Pesticides, Nitrogen, 

and Phosphorus for the Flint River Basin, Alabama and Tennessee....................................................................... 35

Watershed Input .............................................................................................................................................................. 35

Instream Yield................................................................................................................................................................. 35

Appendix B. Input and Export Estimates and Detection Frequency of Selected Pesticides for the 

Flint River and Hester Creek, 1998-2000................................................................................................................ 36

Appendix C. Input and Export Estimates of Nitrogen and Phosphorus for the 

Flint River and Hester Creek, 1998-99.................................................................................................................... 37
vi Water Quality of the Flint River Basin, Alabama and Tennessee, 1999-2000

FIGURES

1. Map showing land use, land cover, and location of sampling sites in the Flint River Basin and 

adjacent section of the Tennessee River..................................................................................................................... 3 

2. Map showing physiographic sections and impaired waters (1998) in the 

Flint River Basin, Alabama and Tennessee................................................................................................................ 4 

3. Hydrograph showing that daily mean streamflows in the Flint River during the fall of 1998

and 1999, and during the winter of 2000, were near or below the 25th percentile of daily 

mean streamflow for the period of record (1930-94) ................................................................................................ 8

4. Bar chart showing detection frequency of pesticides for the Flint River and 

Hester Creek, 1999-2000, and for a national data set ................................................................................................ 10 

5. Bar chart showing pesticide use and instream yield for the Flint River and Hester Creek, 1999.............................. 11 

6. Time series plots showing streamflow and concentration of atrazine and metabolites and 

cyanazine for the Flint River and Hester Creek, 1999-2000...................................................................................... 12 

7. Photograph showing that many pesticides are transported to nearby streams 

by surface runoff from cropland................................................................................................................................. 14 

8. Bar chart showing maximum concentrations of pesticides and aquatic-life criteria 

for the Flint River and Hester Creek, 1999-2000....................................................................................................... 16 

9. Time series plot showing relation of exceedances of aquatic-life criteria to season and streamflow 

for selected pesticides for the Flint River and Hester Creek, 1999-2000 .................................................................. 17 

10. Maps showing land use and land cover, and spatial variation of concentrations of atrazine, 

aldicarb sulfoxide, and malathion in the Flint River Basin during base flow, May 1999.......................................... 18

11. Photograph showing that the Flint River, designated as a canoe trail by the Madison County 

Commission in Alabama, is a popular water recreation resource used for canoeing and tubing .............................. 19 

12. Boxplot showing that concentrations of E. coli in the Flint River and Hester Creek during storm flows 

frequently exceed U.S. Environmental Protection Agency criteria for recreation .................................................... 20 

13. Scatterplot and photographs showing E. coli concentration and turbidity for the 

Flint River and Hester Creek...................................................................................................................................... 21 

14. Maps showing land use and land cover, and spatial variation of concentrations of E. coli, 

total nitrogen, and total phosphorus in the Flint River Basin during base flow, 1999 .............................................. 22 

15. Time series plot showing streamflow and concentration of total nitrogen and dissolved 

nitrite plus nitrate for Flint River and Hester Creek, 1999-2000 .............................................................................. 24 

16. Boxplot showing flow-weighted mean concentrations of total nitrogen and total 

phosphorus for the Flint River and Hester Creek, 1999, as compared to 

undeveloped and agricultural basins in the southeastern region of the United States ............................................... 26

17. Time series plot showing relation between turbidity of intake water for the 

City of Huntsville water-treatment plant (South Parkway Plant) and 

streamflow in the Flint River near Brownsboro, Ala., 1999-2000 ............................................................................ 27 

18. Map and time-series plots showing streamflow and atrazine concentrations in the Flint River, 

the Tennessee River, and at the intake to the City of Huntsville’s 

water-treatment plant, April 2-7, 2000....................................................................................................................... 28 

TABLES

1. Description of stream monitoring networks in the Flint River Basin and Tennessee River, 1999-2000 ............... 5 

2. Watershed characteristics of stream sampling sites in the Flint River Basin and Tennessee River ....................... 6 
Contents vii

CONVERSION FACTORS, VERTICAL DATUM, AND ABBREVIATIONS

Sea level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929)—a geodetic 

datum derived from a general adjustment of the first-order level nets of the United States and Canada, formerly called Sea 

Level Datum of 1929.

ABBREVIATIONS AND ACRONYMS

NAWQA National Water Quality Assessment

U.S. EPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey

WATER-QUALITY ABBREVIATIONS

col./100 mL Colonies per 100 milliliters

NTU Nephelometric turbidity units

mg/L Milligrams per liter

Multiply By To obtain

inch (in.) 2.54 centimeter

foot (ft) 0.3048 meter

mile (mi) 1.609 kilometer

cubic feet per second (ft3/s) 0.02832 cubic meter per second

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

ton per square mile per year [(ton/mi2)/yr] 0.003503 metric ton per hectare per year

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

pound per square mile per year [(lb/mi2)/yr] 0.001751 kilogram per hectare per year
viii Water Quality of the Flint River Basin, Alabama and Tennessee, 1999-2000

GLOSSARY

Aquatic-life criteria. The level of a pollutant or condition necessary to protect fish and 

other aquatic life in a stream or lake. Aquatic-life criteria for pesticides specify a 

maximum concentration that should not be exceeded at any time, or that should not 

be exceeded beyond specified exposure periods.

Detection frequency. Calculated, for a set of samples, as the proportion of samples in 

which the concentration of a constituent is greater than or equal to a specified level, 

such as the detection limit for the analytical method, or a selected threshold of concentration.

Eutrophication. The adverse effects of excess nutrient input to a stream, including overgrowth of plant life and decline of the biological community.

Export. Equivalent to instream load, and used in place of that term in comparisons with 

input to a watershed. Unit-area export is equivalent to yield.

Flow-weighted mean concentration. The ratio of instream load of a constituent to the 

mean discharge during the period of transport (dimensions of mass per volume); and 

equivalent computationally to the flow-weighted mean of the model estimates of 

daily concentration. Expressed in units of concentration (mg/L). This quantity is 

used, in place of load or yield, for evaluating average water-quality conditions at the 

site, and to compare water-quality among sites with differing discharge characteristics.

Input. The mass of a constituent entering a watershed either by deposition on the land surface (land-phase input) or by discharge directly to the stream channel (such as wastewater discharges). Only a portion of the land-phase input reaches the stream channel 

by overland or subsurface transport processes. Unit-area input is the ratio of input to 

area of the watershed (dimensions of mass per time per area).

Instream load. The mass of a constituent moving past a specified point in a channel (for 

example, the mouth of a river basin) during a specified period of time. The instream 

load can be estimated by monitoring the concentration of the constituent periodically, 

and streamflow continuously, at the specified point. 

Synergistic. Having a combined effect greater than the sum of individual effects.

Yield. The ratio of instream load of a constituent to the area of the watershed (dimensions 

of mass per time per area). This area-normalized load is used, in place of load, to 

compare instream loads among watersheds with differing drainage areas, and to compare with inputs to the watershed. 
Abstract 1

Water Quality of the Flint River Basin, Alabama and 

Tennessee, 1999-2000

By Anne B. Hoos, Jerry W. Garrett, and Rodney R. Knight

ABSTRACT

The U.S. Geological Survey monitored 

eight stream sites in the Flint River Basin during 

the period January 1999 through May 2000, to 

characterize patterns in the occurrence of pesticides, fecal-indicator bacteria, and nutrients in 

relation to season and streamflow conditions and 

to land-use patterns. This study is part of the 

National Water-Quality Assessment Program, 

which was designed to assess water quality as it 

relates to various land uses.

Every water sample collected from the Flint 

River Basin had detectable levels of at least two 

pesticides; 64 percent of the samples contained 

mixtures of at least five pesticides. In general, 

pesticides detected most frequently and at highest 

concentrations in streams corresponded to the 

pesticides with the highest rates of use in the 

watersheds. Detections of fluometuron, norflurazon, and atrazine were more frequent (by a margin of 15 percent or more) in samples from the 

Flint River when compared with the frequencies 

of pesticide detections at 62 agricultural stream 

sites across the Nation. Detections of fluometuron 

in the Flint River were more frequent even when 

compared with a cotton-cultivation subset of the 

62 sites. For most pesticides, maximum concentrations did not exceed criteria to protect aquatic 

life; however, maximum concentrations of atrazine, cyanazine, and malathion exceeded aquaticlife criteria in at least one sample. Concentrations 

near or exceeding the aquatic-life criteria 

occurred only during the spring and summer 

(April-July), and generally occurred during storm 

flows.

Less than 5 percent of the estimated mass 

of pesticides applied annually to agricultural areas 

in the Flint River Basin was transported to the 

stream at the monitoring points on the Flint River 

near Brownsboro, Alabama, and on Hester Creek 

near Plevna, Alabama. The pesticides with the 

highest ratios (greater than 3 percent) of the 

amount transported instream to the amount 

applied—atrazine, metolachlor, fluometuron, and 

norflurazon—are preemergent herbicides applied 

to the soil before the crops have emerged, which 

increases the probability of transport in surface 

runoff. 

Concentrations of the fecal-bacteria indicator Escherichia coli (E. coli) in the Flint River and 

Hester Creek exceeded the U.S. Environmental 

Protection Agency criterion for recreation in 

almost all storm samples, and in many samples 

collected up to 6 days following a storm. Concentrations in the Flint River were strongly correlated 

with sample turbidity, suggesting that turbidity 

might be useful as a surrogate for estimating 

E. coli concentrations. Concentrations of the 

nutrients nitrogen and phosphorus in samples 

from the Flint River generally exceeded thresholds indicating eutrophic potential, whereas concentrations in samples from Hester Creek were 

generally below the thresholds. When compared 

with nutrient data from a set of 24 agricultural 

basins across the southeastern region of the 

United States, concentrations in the Flint River 

and Hester Creek were slightly above the regional 

median.

Base-flow concentrations of certain pesticides, nutrients, and E. coli were compared to 

land-use information for eight sites in the Flint 
2 Water Quality of the Flint River Basin, Alabama and Tennessee, 1999-2000

River Basin. The highest base-flow concentrations of aldicarb sulfoxide, fluometuron, and 

phosphorus were found in the tributaries with the 

greatest density of cotton acreage in the watershed. Similarly, high base-flow concentrations of 

total nitrogen were correlated with a high percentage of cultivated land in the watershed. Lack of 

information about distribution of stream access by 

livestock weakened the analysis of correlation 

between livestock and base-flow concentrations 

of E. coli and nutrients.

Input of dissolved and suspended chemicals 

from the Flint River during storms influences 

water quality in the reach of the Tennessee River 

from which the City of Huntsville, Alabama, 

withdraws about 40 percent of its drinking water. 

During the storm of April 2-5, 2000, concentrations of several pesticides were at least a factor 

five times greater in Huntsville’s intake water 

when compared with concentrations in the Tennessee River upstream from the Flint River, 

although concentrations of all pesticides were 

below the U.S. Environmental Protection Agency 

drinking-water standards at all sites on the Tennessee River and in Huntsville’s intake water.

INTRODUCTION

The Flint River, a tributary to the Tennessee 

River, drains 568 square miles (mi2

) of primarily agricultural land in northern Alabama and south-central 

Tennessee (fig. 1). Urban and residential land represent a small (less than 1 percent), but growing part of 

land use in the watershed, as residential growth from 

the City of Huntsville, Alabama, spreads northward 

and eastward into the watershed. The Flint River is an 

important recreational and scenic resource; a 34-mile 

(mi) section of the river (fig. 2) is a popular canoe and 

tubing area and was designated a canoe trail by the 

Madison County Commission in 1993. Local agencies 

are conducting riparian restoration projects to protect 

and enhance habitat for the diverse aquatic life along 

the Flint River. Among the several threatened species 

of fish and aquatic invertebrates found in the Basin are 

the slackwater darter, Tuscumbia darter, and southern 

cave fish.

Most of the Flint River Basin lies within the 

eastern part of the Highland Rim Physiographic 

section (fig. 2), an area of well drained soils and gently 

rolling terrain that contains productive farmland (predominantly cotton, corn, and soybeans). The eastern 

and southwestern edges lie on the escarpment of the 

Cumberland Plateau (fig. 2), which is characterized by 

steeply sloping forested land with pasture and cultivated land restricted to the narrow valley floors. 

Stream channels throughout the Flint River Basin are 

characterized by gravel and bedrock bottoms with 

numerous springs and spring-associated fish fauna. 

The U.S. Geological Survey (USGS) National 

Water-Quality Assessment (NAWQA) Program is currently investigating water quality in the lower Tennessee River Basin (fig. 1, map inset), with several 

monitoring activities targeted in the Flint River Basin. 

The purpose of this investigation is to assess surfacewater quality related to various land uses. The target 

issues of this assessment program—nutrients, fecalindicator bacteria, and pesticides—coincide with 

assessments conducted by State water-quality regulatory agencies on causes of water-quality impairment in 

the Flint River Basin (Tennessee Department of Environment and Conservation, 2000; Alabama Department of Environmental Management, 2000, 

table 6-17), and with concerns of the local watershed 

group, the Flint River Conservation Association. The 

water-quality assessments of water (designated as 

impaired water, 1998, in fig. 2) in the Flint River Basin 

by State regulatory agencies are presented in this 

report to add perspective to the interpretations of 

water-quality data collected for this study; however, 

this study was not designed to address sources or 

causes of impairment in specific stream reaches.

Purpose and Scope

The purposes of this report are to characterize 

surface-water quality in the Flint River Basin across a 

range of seasonal and streamflow conditions, and to 

assess variation of base-flow water quality in relation 

to land use in the Basin. The water-quality constituents 

included in the characterization are pesticides, fecalindicator bacteria, and nutrients. The effect of the Flint 

River Basin on water quality in the main stem of the 

Tennessee River at a drinking-water intake for the City 

of Huntsville, Alabama, also is described. This report 

is based on data collected from January 1999 through 

May 2000 from eight stream sites in the Flint River 

Basin and from three sites on the main stem of the 

Tennessee River.
Introduction 3

10 15 MILES

10 15 20 KILOMETERS
4 Water Quality of the Flint River Basin, Alabama and Tennessee, 1999-2000
Study Objectives and Approach 5

Acknowledgments

The authors thank several individuals who gave 

special assistance in compiling data: Joseph Berry and 

William Abbott, Natural Resources Conservation Service; Mark Hall, Alabama Cooperative Extension Service; David Qualls, Tennessee Agricultural Extension 

Service; Victor Payne, Alabama Soil and Water Conservation Committee; and Pat Morgan, City of Huntsville. Susan F. Weber, Flint River Conservation 

Association, and James Kingsbury and Gregory Clark, 

USGS, provided excellent technical guidance and 

review. Thanks to Reavis Mitchell, USGS, for assisting with the design of illustrations. Assistance from 

Wayne Miller, City of Huntsville, during a special 

storm sampling effort, is appreciated.

STUDY OBJECTIVES AND APPROACH

The study objectives were to characterize water 

quality in the Flint River Basin across a range of seasonal and streamflow conditions, to assess spatial 

variation of base-flow water quality in the Flint River 

Basin, and to relate water quality in the Flint River to 

water quality in a drinking-water source for the City of 

Huntsville.

Design of Monitoring Program

The monitoring program included three separate 

networks of stream sites and sampling schedules 

designed to match the different study objectives 

(tables 1 and 2). The intensive monitoring network, 

consisting of two sites (Hester Creek and Flint River 

sites, fig. 1), was used to characterize water quality in 

the Flint River Basin across a range of seasonal and 

streamflow conditions. The spatial monitoring network, consisting of the two intensive sites and six 

additional sites (S1-S6, fig. 1), was used to assess spatial variation of base-flow water quality in the Basin 

and to compare variation in water quality to variation 

in land use. The main stem Tennessee River monitoring network, consisting of three sites on the Tennessee 

River (M1-M3, fig. 1) and the Flint River site (fig. 1), 

1

 Historic streamflow record available from a nearby USGS streamflow gaging station, Flint River near Chase, Ala. (03575000), for the period 1930-94. 2 Hourly streamflow record during the sampling period (April 2-5, 2000) was estimated for graphs in figure 18 by interpolating from continuous streamflow record from Tennessee River at Whitesburg, Ala. (03575500) and measurements of instantaneous streamflow at sites M1 - M3.

Table 1. Description of stream monitoring networks in the Flint River Basin and Tennessee River, 1999-2000

[mi2, square mile]

Study component (number of sites) 

and objective Sampling sites Sampling schedule Streamflow-data collection

Intensive monitoring network (2 sites)

Characterize water quality in the Flint 

River Basin across a range of seasonal and streamflow conditions.

The Hester Creek site (fig. 1 and 

table 2), on a tributary to Flint 

River, and the Flint River site 

(fig. 1 and table 2), on the Flint 

River downstream from Hester 

Creek.

 Fixed-frequency schedule 

(weekly or biweekly 

during spring and summer; monthly during 

fall and winter).

Plus 18 storm events.

Continuous 

record, 1999-

current year. 1

Spatial monitoring network (8 sites)

Characterize spatial variation of baseflow water quality in the Flint River 

Basin, and evaluate the representativeness of the intensive monitoring 

sites.

Six additional tributary sites (S1-S6, 

fig. 1 and table 2), along with the 

two intensive sites. The eight sites 

together drain a total watershed 

area of 440 mi2, almost 80 percent 

of the Flint River Basin.

Two separate base-flow 

periods: May 12, 1999 

(following a 5-day dry 

period) and September 

7-9, 1999 (following a 

40-day dry period). 

Measurement of 

instantaneous 

streamflow at 

time of sampling.

Main stem Tennessee River monitoring network (4 sites)

Relate Flint River water quality to a 

drinking-water source.

Three sites along the main stem Tennessee River (sites M1 - M3, fig. 1 

and table 2), and one site on the 

Flint River (Flint River, fig. 1).

A single storm event 

(April 2-5, 2000).

Measurement of 

instantaneous 

streamflow at 

time of sampling. 2
6 Water Quality of the Flint River Basin, Alabama and Tennessee, 1999-2000

a Streamflow in the Tennessee River at river mile 334 is divided by Hobbs Island into right and left channel, sites M2 and M3.

Table 2. Watershed characteristics of stream sampling sites in the Flint River Basin and Tennessee River[mi2, square miles; land-cover estimates from satellite imagery from period 1989-92 (provided by Frank Sagona, Tennessee Valley Authority, written commun., 1998); density of acreage of cotton, corn, and soybeans calculated based on estimates from 1998 from Joseph Berry (U.S. Natural Resource Conservation Service, written commun., 2000) and William Abbott (U.S. Natural Resource Conservation Service, written 

commun., 2000) and reported in percentage; density of failing septic systems and livestock calculated based on census estimates from 1998 for the Alabama part of the watersheds (Victor Payne, Alabama Soil and Water Conservation Committee, written commun., 1999) and reported in number per square mile, density estimates are subject to error because the areas for which census estimates were available do not correspond exactly with the watersheds for the sampling sites; site identification denotes monitoring network; <, less than; S denotes spatial network; M denotes main stem Tennessee River monitoring network; --, not estimated]

Site 

identification 

(fig. 1)

Surface-water station/Site location

Drainage 

area (mi2)

Major land use, in percent

Cotton Corn Soy- beans

Failing septic 

systems

Cattle 

and 

dairy 

cows 

Chicken 

and 

hogs Number Name River mile For- est Pas- ture Culti- vated Ur- ban Other

Hester Creek

0357479650 Hester Creek at Buddy Williamson Road near Plevna, 

Ala.

4.6 29.3 27 50 15 < 1 8 9 7 13 11 150 570

Flint River

03575100 Flint River near Brownsboro, Ala. 27.6 374 25 45 20 < 1 10 8 4 11 9 70 150

S1 03574702 Flint River at Lincoln, Tenn. 56.5 52.1 19 59 11 < 1 11 3 6 11 25 30 0S2 03574750 West Fork Flint River near 

Hazel Green, Ala.

1.3 39.6 18 52 17 1 12 3 6 11 25 30 0

S3 03574794 Mountain Fork Creek at 

New Market, Ala.

4.0 37.5 70 15 14 < 1 1 1 3 6 12 54 8

S4 03574823 Brier Fork near Hazel 

Green, Ala.

5.8 40.8 14 56 14 < 1 16 11 1 8 8 7 40

S5 03574870 Beaverdam Creek near 

Meridianville, Ala.

2.8 37.2 19 39 30 < 1 12 21 1 16 7 20 0

S6 03575200 Hurricane Creek near Gurley, Ala. 2.4 63.8 63 30 6 < 1 < 1 1 3 6 12 54 8

M1 03574680 Tennessee River near Morgan City, Ala. 340 24,960 -- -- -- -- -- -- -- --M2 03575480 Tennessee River at State 

Docks, Ala. (also referred to as “right channel at Hobbs Island”)

334a

25,610

-- -- -- -- -- -- -- --

M3 03575490 Tennessee River downstream from Hobbs 

Island, Ala. (also referred to as “left channel at Hobbs Island”)

334a -- -- -- -- -- -- -- --
Hydrologic Conditions 7

was used to assess the effect of the Flint River on 

water quality in the Tennessee River at a drinkingwater intake for the City of Huntsville, Alabama.

Water-quality constituents analyzed included 

113 current-use pesticides (dissolved-phase only), the 

fecal-indicator bacteria Escherichia coli (E. coli), and 

dissolved and suspended phases of nitrogen and phosphorus. Procedures for sample collection and processing followed guidelines for the NAWQA program and 

are described in Shelton (1994), Gilliom and others 

(1995), and Mueller and others (1997). Qualityassurance results for the NAWQA program are 

described in Martin and others (1999).

Watershed Inputs

Inputs of pesticides and nutrients were estimated for the watersheds of two monitoring sites in the 

Flint River Basin: the Flint River and one of its tributaries, Hester Creek. The methods used to estimate 

inputs are described in Appendix A; the estimates are 

presented in Appendixes B and C. Estimates of pesticide inputs represent crop pesticide use only. Herbicides applied in the greatest amounts to crops were 

glyphosate (cotton and soybeans) and atrazine (corn); 

insecticides applied in the greatest amounts to crops 

were aldicarb and dicrotophos (cotton). Density of cultivated land and, therefore, unit-area input estimates of 

pesticides were larger for the watershed of the tributary site, Hester Creek, than for the larger watershed of 

the Flint River site.

Inputs of nitrogen and phosphorus to the watersheds were estimated from crop fertilizer, crop 

nitrogen-fixation, livestock waste, failing septic systems, atmospheric deposition, and wastewater. Input 

estimates from agricultural activities (crop fertilizer 

application, crop nitrogen-fixation, and livestock 

waste) are much larger than estimates from other 

sources; however, these inputs are distributed across 

the land surface throughout the watershed, and the percentage transported to streams is unknown. Summed 

unit-area input estimates were larger (almost double) 

for the Hester Creek watershed because of the greater 

density of livestock in the watershed.

HYDROLOGIC CONDITIONS

Precipitation in the Flint River Basin during the 

period October 1998 through May 2000 was almost 

20 percent below normal. Total precipitation for the 

20-month period in Huntsville, Ala., was 79.6 in., 

compared to 97.8 in., the 30-year normal precipitation 

for the same length of time. The below-normal rainfall 

resulted in below-normal streamflow during much of 

this time period, as demonstrated in figure 3 which 

shows streamflow at the Flint River near Brownsboro, 

Ala., fell below the 25th percentile of daily mean 

streamflow (based on 1930-94 historical record) during this time. Despite periods of below-normal streamflow, the mean streamflow yield for 1999 (1.6 cubic 

feet per second per square mile [(ft3/s)/mi2]) equaled 

the mean annual streamflow yield for 1930-94 

[1.7 (ft3/s)/mi2

]; this is explained by the above-normal 

precipitation and runoff in January 1999 offsetting the 

below-normal precipitation and runoff during other 

parts of the year.

Water-quality conditions in the Flint River Basin 

during water years 1999-2000 also may have deviated 

from normal: transport of water-quality constituents, 

including pesticides, bacteria, and nutrients, to the 

streams through storm runoff was probably lower than 

normal during many months. The below-normal rainfall and recharge during most months also may have 

resulted in below-normal ground-water flow and transport of constituents to streams.

WATER QUALITY OF THE FLINT RIVER 

BASIN

Water quality in the Flint River Basin is affected 

by diverse land-use and natural factors. This section of 

the report is organized by water-quality issues (pesticides, fecal-indicator bacteria, and nutrients); waterquality conditions are described in relation to these 

factors. In each category, variation in water quality 

with season and streamflow is described using data 

from the intensive monitoring network, then water 

quality during base flow in the contributing watersheds is evaluated using data from the spatial network.

Pesticides

Physical properties and use restrictions of many 

pesticides currently in use result in minimum residue 

available for transport to the aquatic environment. 

Many pesticides are toxic at low concentrations; therefore, some concern exists about the risk to aquatic life 

posed by their use. Water samples collected from eight 

sites in the Flint River Basin were analyzed for 

113 pesticides commonly used throughout the United 
8 Water Quality of the Flint River Basin, Alabama and Tennessee, 1999-2000
Water Quality of the Flint River Basin 9

States. The reader should note, however, that not all of 

these pesticides are used in the Flint River Basin. Further, several pesticides used in the Flint River Basin 

were not included in the analysis; for example, dicrotophos and PCNB (pentachloronitrobenzene). 

Of the 113 pesticides analyzed in 75 stream 

samples from the Flint River and Hester Creek, 55 pesticides were detected at concentrations greater than 

0.01 microgram per liter (μg/L). Of these 55 pesticides, 47 were detected in samples from the Flint 

River, and 35 were detected in samples from Hester 

Creek. Pesticides that are applied primarily to cotton 

fields accounted for 17 of the pesticides detected 

(more than for corn or soybeans). Twenty-one pesticides were detected at concentrations greater than 

0.01 μg/L in 10 percent or more of the samples 

(Appendix B and fig. 4).

Pesticide-detection frequencies for the Flint 

River and Hester Creek sites were compared with a 

data set of 62 sites across the Nation that drained predominantly agricultural land (U.S. Geological Survey, 

2001) (fig. 4). Fluometuron, norflurazon (both applied 

to cotton), and atrazine (applied to corn) were detected 

more frequently (by a margin of 15 percent or greater) 

in samples from the Flint River and Hester Creek 

when compared with the national data set. The higher 

detection frequency of norflurazon in the Flint River 

Basin may result from a greater density of cotton acreage and thus greater use of fluometuron in the Flint 

River Basin as compared with use in the agricultural 

basins represented in the national data set. This statement is supported by a comparison with a subset (15 

sites) of the national data set representing cotton cultivation; detection frequencies of norflurazon were 

about the same for the subset compared with detection 

frequencies in the Flint River Basin. In contrast, the 

detection frequency of fluometuron in the Flint River 

was higher (by a margin of 35 percent) than detection 

frequencies in the other cotton cultivation basins, suggesting that some factor in addition to cotton acreage 

contributes to the high detection frequency in the Flint 

River Basin.

Comparison of Watershed Inputs to Detection 

Frequency, Instream Concentrations, and Yields

In general, the most heavily applied pesticides 

were detected most frequently, with the highest concentrations and the highest annual instream yields. For 

example, atrazine was detected in 100 and 93 percent 

of the samples from the Flint River and Hester Creek, 

respectively (Appendix B), and was transported 

instream from the Flint River and Hester Creek 

watersheds at the highest rate (an estimated 2.0 and 

1.5 pounds per square mile per year [(lb/mi2

)/yr], 

respectively) (fig. 5 and Appendix B). The instream 

occurrence of a pesticide is related not only to its 

application rate, but also to physical and chemical 

properties controlling the pesticide’s mobility in the 

environment. For example, the most heavily applied 

pesticide, glyphosate, was detected in only 17 percent 

of samples from Hester Creek; glyphosate is known to 

strongly adsorb to soil and, therefore, has a low potential for leaching to runoff or ground water. 

Almost two-thirds of the pesticides were 

detected more frequently in samples from the Flint 

River than in samples from Hester Creek, although 

estimated inputs (amounts applied to crops) were 

higher, on a unit-area basis, for the Hester Creek 

watershed (fig. 5). Instream yields (unit-area exports) 

also generally were higher for the Flint River site; the 

most notable exception was metolachlor, a herbicide 

applied primarily to manage corn and soybean pests—

the yield in Hester Creek was 3.5 (lb/mi2)/yr compared 

to the Flint River where the yield was 1.4 (lb/mi2)/yr. 

A comparison of concentration distributions during 

base flow between the two sites, however, showed the 

opposite pattern: maximum base-flow concentrations 

were higher in Hester Creek for almost two-thirds of 

the pesticides detected.

Export ratios were calculated for 10 pesticides 

as the ratio of watershed export (amount transported 

instream) to watershed input (amount applied to crops) 

(fig. 5 and Appendix B). Export ratios ranged from 

0.06 percent (trifluralin) to 4.7 percent (norflurazon), 

and generally, except for metolachlor, were higher for 

the Flint River than for Hester Creek. The pesticides 

for which the highest export ratios (greater than 3 percent) were observed—atrazine, metolachlor, fluometuron, and norflurazon—are preemergent herbicides 

applied to the soil before crops have emerged, thus 

increasing the likelihood of transport in surface runoff. 

Metolachlor is commonly applied to the soil surface 

without incorporation into the soil, further increasing 

its potential for transport in runoff.

Variation of Concentrations with Season and 

Streamflow

Variation of pesticide concentrations in the Flint 

River and Hester Creek generally coincided with the 

pesticide application period. Instream concentrations 

of the preemergent herbicide atrazine, applied March 

through May to corn fields, peaked in late April and 

May at the two stream sites (fig. 6a). Atrazine was 

detected in stream samples throughout the year, but at 
10 Water Quality of the Flint River Basin, Alabama and Tennessee, 1999-2000
Water Quality of the Flint River Basin 11
12 Water Quality of the Flint River Basin, Alabama and Tennessee, 1999-2000
Water Quality of the Flint River Basin 13
14 Water Quality of the Flint River Basin, Alabama and Tennessee, 1999-2000

much lower concentrations (as low as 

0.001 μg/L) when compared with April and 

May samples. Concentrations of the atrazine metabolite, hydroxyatrazine, persisted 

at higher levels (about 0.1 μg/L) throughout the year. Instream concentrations of 

cyanazine, which is applied as both a preand postemergent herbicide to cotton and 

corn fields, peaked in the spring and summer months (fig. 6b) corresponding to 

these different application periods. The 

lower concentrations of cyanazine 

observed during spring of 2000 compared 

with spring 1999 (fig. 6b) may be a result 

of the change in regulated use of cyanazine. 

Manufacture of cyanazine ceased at the end 

of 1999; use of remaining product is 

allowed during the period from 2000 to 

2002, but use has been declining gradually 

since 1999 (U.S. Environmental Protection 

Agency, 1999a).

Concentrations of pesticides varied 

with streamflow as well as with season. 

Samples were categorized as either base 

flow or storm flow on the basis of 

hydrograph analysis and sample turbidity. 

Peak concentrations of almost all pesticides 

occurred during storm flows, indicating 

that the pesticides generally are transported 

by surface runoff (fig. 7). Concentrations 

do not increase during every storm, however, because a major factor affecting concentrations of pesticides in storm flow is 

the period of time between pesticide application and the occurrence of a storm.

For some pesticides, such as atrazine 

(fig. 6a), concentrations in base-flow samples were 

almost as high as concentrations in some of the storm 

samples during the same season, indicating that concentrations in ground water also were elevated. For 

pesticides such as cyanazine (fig. 6b), concentrations 

in base-flow samples were low (less than 0.008 μg/L), 

but increased to detectable levels during a few storms. 

This pattern indicates that almost all of the mass of 

cyanazine is transported to the stream during runoff, 

with negligible amounts transported in ground water. 

The different base-flow transport patterns of atrazine 

and cyanazine can be explained by their different 

physical and chemical properties: residual cyanazine 

in the soil after application degrades more quickly to 

its metabolites than does atrazine, and thus, not as 

much of the parent compound is available for transport 

to streams in subsequent runoff or to the ground water. 

Transport of cyanazine metabolites in base flow was 

not examined because water samples were not analyzed for these metabolites.

Comparison of Concentrations with Criteria to 

Protect Aquatic Life

The environmental significance of the observed 

concentrations can be evaluated by comparing concentrations with water-quality criteria that were established to protect aquatic life. Aquatic-life criteria have 

been established for 23 of the 55 pesticides detected in 

samples from the Flint River and Hester Creek. 

Maximum concentrations of pesticides were generally 

Figure 7. Many pesticides are transported to nearby streams by surface runoff from 

cropland (cotton field in the Hester Creek watershed, April 3, 2000).
Water Quality of the Flint River Basin 15

less than the aquatic-life criteria; however, concentrations of atrazine, cyanazine, and malathion exceeded 

aquatic-life criteria in at least one sample each (fig. 8). 

Concentrations near or exceeding the aquatic-life criteria occurred from April through July, generally during storm flow (fig. 9). The pattern of concentrations 

for the insecticide malathion differed from other pesticides: concentrations in the Flint River exceeded the 

aquatic-life criterion in only one sample, during spring 

base flow rather than spring runoff, but remained 

within an order of magnitude of the peak concentration throughout the summer and fall. Concentrations 

of aldicarb sulfoxide, a metabolite of the insecticide 

aldicarb, were near, but below, the aquatic-life criterion. Aldicarb was detected in only one sample, suggesting that aldicarb degrades to its metabolite (which 

is equally toxic) either prior to transport to the stream 

or rapidly in stream. 

Comparison of aquatic-life criteria with maximum (rather than median) concentrations is appropriate because the criteria specify maximum 

concentrations (acute toxicity) that should not be 

exceeded at any time (Environment Canada, 1999; 

International Joint Commission, 1989). The exceptions are the criteria for chlorpyrifos and malathion, 

which specify the maximum concentration for a 4-day 

exposure period once every 3 years (U.S. Environmental Protection Agency, 1999b). Pesticide criteria 

generally are based on the results of single-chemical 

toxicity tests, and do not consider the synergistic 

effects of exposure to low-level pesticide mixtures, 

such as the mixtures detected in samples from the Flint 

River and Hester Creek. For example, every stream 

sample had detectable levels of at least two pesticides; 

64 percent of the samples contained mixtures of at 

least five pesticides.

Spatial Variation of Concentrations During 

Base Flow

Of the 113 pesticides analyzed, 34 were detected 

at concentrations greater than 0.01 μg/L in at least one 

of the base-flow samples from the eight stream sites in 

the Flint River Basin. Variation in concentrations of 

pesticides during base flow (May 12, 1999) is shown 

in figure 10. Concentrations during May 1999 did not 

exceed aquatic-life criteria for any pesticide except for 

malathion, which exceeded the criterion of 0.1 μg/L at 

two sites: Mountain Fork Creek (site S3) and the Flint 

River at Brownsboro, Ala. Base-flow concentrations 

during May 1999 were close to (within 20 percent of) 

the criteria for atrazine (at Brier Fork, site S4, fig. 10) 

and the insecticide methyl azinphos (also at Brier 

Fork; U.S. Geological Survey, unpub. data, 2001). 

Base-flow concentrations of pesticides at the eight 

sites during September 1999 (not shown on fig. 10; 

U.S. Geological Survey, unpub. data, 2001) were generally less than the method detection limit (MDL) or, 

for atrazine, were less than 0.03 μg/L.

The spatial pattern of concentrations of selected 

pesticides during May 1999 base flow was compared 

to the pattern of various watershed characteristics 

including percentage of cultivated land in the watershed and acreage of cotton, corn, and soybeans 

(table 2). The highest base-flow concentrations of aldicarb sulfoxide (fig. 10) and fluometuron were detected 

in the watersheds with the greatest density of cotton 

acreage in the watershed. This relation coincides with 

pesticide use; aldicarb and fluometuron are both 

applied to cotton fields at planting time in April. 

Base-flow concentrations of pesticides (other 

than malathion) in Hester Creek and the Flint River 

were similar to those at the tributary sites (S1-S6, 

fig. 10) during the May and September 1999 monitoring periods, suggesting that base-flow concentrations 

documented through intensive monitoring at Hester 

Creek and Flint River are typical of base-flow conditions throughout the Flint River Basin. Base-flow concentrations of malathion, however, ranged much more 

widely between sites; the base-flow concentration in 

Mountain Fork Creek (site S3) during May 1999 was 

almost 1,000 times higher than its concentration in 

other tributaries. The elevated concentration of 

malathion in Mountain Fork Creek probably contributed to the malathion detected in the Flint River on the 

same day, and also may account for detectable concentrations of malathion in base flow in the Flint River 

throughout the year (fig. 9).

Fecal-Indicator Bacteria

Fecal pollution impairs the quality of streams 

and rivers for recreational use and adversely affects 

fish and aquatic life. The following discussion 

addresses impairment of recreational uses only. Consumption of fecal-contaminated water can cause digestive tract infections, and immersion alone can result in 

infections of the eyes, ears, nose, and throat. Fecalindicator bacteria such as Escherichia coli (E. coli) 

typically are not disease-causing (pathogenic) bacteria 

but can be correlated to the presence of human enteric 
16 Water Quality of the Flint River Basin, Alabama and Tennessee, 1999-2000
Water Quality of the Flint River Basin 17

pathogens, and can consequently be used as a measure 

of whether water is safe for recreational contact. The 

recommended criterion for E. coli concentrations indicating risk to human health in swimming waters is 

126 colonies per 100 milliliters (col./100 mL), which 

applies to the geometric mean of samples collected 

over a 30-day period. Epidemiological studies at freshwater beaches have indicated that exposure to this 

level of E. coli concentrations causes 8 illnesses per 

1,000 swimmers (U.S. Environmental Protection 

Agency, 1986, table 4). The E. coli criterion for a 

single sample collected from a water body with light 

to moderate recreational use is 406 col./100 mL.

Concentrations of E. coli exceeded the U.S. EPA 

criterion of 126 col./100 mL for human health during 

certain summer months in the Flint River and Hester 

Creek. Monthly mean concentrations of E. coli for the 

Flint River, in the reach used for recreational boating 

(figs. 2 and 11), were less than the criterion in June 

(111 col./100 mL) and August (45 col./100 mL) and 

exceeded the criterion during July (255 col./100 mL). 

Monthly mean concentrations of E. coli in Hester 

Creek exceeded the criterion in June 

(760 col./100 mL), July (640 col./100 mL), and 

August (380 col./100 mL). The monthly mean concentrations were calculated as the geometric mean of 
18 Water Quality of the Flint River Basin, Alabama and Tennessee, 1999-2000
Water Quality of the Flint River Basin 19

three samples (Flint River) or four samples (Hester 

Creek) collected over a 30-day period.

Variation of Concentrations with Streamflow and 

Turbidity

Concentrations of E. coli in the Flint River and 

Hester Creek are significantly different (p < 0.001, 

Wilcoxon rank-sum test) between base flow and storm 

flow (fig. 12). Concentrations of E. coli in the 11 baseflow samples from the Flint River, in the reach used 

for recreational boating, generally did not exceed the 

single-sample criterion, whereas E. coli concentrations 

in 12 out of the 13 storm samples exceeded the 

single-sample criterion. The median value for all baseflow samples from the Flint River was 50 col./100 mL, 

less than both the single-sample and geometric-mean 

criteria. However, the median value for samples collected 3 to 6 days after a storm was higher, almost 

equal to the geometric mean criterion, suggesting that 

the bacteriological risk remains elevated at least 6 

days after a storm. Concentrations of E. coli were 

higher in Hester Creek when compared with the Flint 

River concentrations; concentrations 

in 3 of 14 base-flow 

samples from Hester 

Creek exceeded the 

single-sample criterion, and E. coli concentrations in 14 of 

16 storm samples, 

and concentrations in 

7 of 9 samples collected 3 to 6 days 

after a storm, 

exceeded the singlesample criterion 

(fig. 12).

Concentrations of E. coli did 

not vary as greatly 

with season 

(p > 0.40; Wilcoxon 

rank sum test) as 

with streamflow. 

Mass loading of 

E. coli was much 

greater in winter, 

however, because of 

more frequent occurrences of storms. Based on 

instream load calculations, 84 percent of the estimated 

annual instream load of E. coli in the Flint River was 

calculated for the 3-month period of December 

through February, whereas only 2 percent was calculated for the 3-month period of June through August; 

for Hester Creek, 54 percent of the estimated annual 

load was calculated for the period of December 

through February, and 2 percent for the period of June 

through August.

Concentrations of E. coli were strongly correlated with turbidity for the Flint River throughout the 

range of concentration values (r > 0.9, p < 0.001 for 

log-transformed data); correlation was not as strong 

for Hester Creek, especially for E. coli concentrations 

less than 1,000 col./100 mL (fig. 13). Turbidity, therefore, may be useful as a surrogate for estimating concentrations of E. coli in the Flint River. For example, a 

turbidity value of 22 nephelometric turbidity units 

(NTU) was estimated from a linear regression of the 

data (fig. 13) for the Flint River to be the value at 

which the E. coli concentration would be expected to 

exceed the single-sample criterion (406 col./100 mL).
20 Water Quality of the Flint River Basin, Alabama and Tennessee, 1999-2000

Spatial Variation of Concentrations During Base 

Flow

E. coli-concentration data were collected from 

the network of eight stream sites in the Flint River 

Basin during base flow in May and September 1999 

(fig. 14). Concentrations exceeded the single-sample 

criterion for recreation (406 col./100 mL) at two sites: 

Hester Creek and West Fork Flint River, site S2. The 

spatial pattern of E. coli concentrations was compared 

to the pattern for various watershed characteristics 

including percentage of pastureland and percentage of 

cultivated land, density of livestock population, and 

failing septic systems (table 2). The reader should note 

that input from livestock is not necessarily represented 

by density of population; stream access may also be an 

important factor, but one that was not considered in 

this analysis. Correlation was significant (r > 0.9, 

p < 0.006) between E. coli concentration during May 

1999 and density of livestock population (highest for 

Hester Creek). A weaker correlation (r = 0.7, p = 0.10) 

was observed between E. coli concentrations during 

September 1999 and density of failing septic systems 

(highest for West Fork Flint River, site S2). These correlations suggest that, of the four variables considered, 

livestock populations were the most likely source of 

fecal material to streams during base flow in May 

1999; whereas failing septic systems were the most 

likely source during base flow in September 1999, 

when sampling followed a prolonged 40-day dry 

period. Correlations should be interpreted with caution, however, because of the small number of observations (n = 8).

The E. coli-concentration data from the spatial 

network can be used to identify which tributaries in the 

Flint River Basin contribute the largest amount of fecal 

material to the Flint River during base flow. During 

May 1999, Hester Creek contributed the largest 

amount (41 percent) of the tributary load to the Flint 

River, and Beaverdam Creek (site S5) contributed the 

second largest amount (26 percent). Bacterial loading 

differed during September 1999 after a prolonged dry 

period, when West Fork Flint River (site S2) contributed the largest amount (56 percent).
Water Quality of the Flint River Basin 21
22 Water Quality of the Flint River Basin, Alabama and Tennessee, 1999-2000
Water Quality of the Flint River Basin 23

Nutrients

Nutrient overenrichment of streams can promote 

excess growth of aquatic plants, resulting in recreational impairment and adverse effects on aquatic life. 

In the Flint River Basin, Hester Creek and its tributaries and the upper part of the Flint River (from the 

Alabama/Tennessee State line to headwaters) and its 

tributaries were assessed as impaired by nutrients in 

1998 (fig. 2) (Tennessee Department of Environment 

and Conservation, 2000). 

Variation of Concentrations with Season and 

Streamflow

Concentrations of the nutrients nitrogen and 

phosphorus in samples from the Flint River generally 

exceeded thresholds indicating eutrophic potential, 

whereas concentrations in samples from Hester Creek 

generally were below the thresholds (fig. 15). The 

threshold indicating eutrophic potential should be 

compared with conditions during the summer period 

of aquatic-plant growth (Dodds and others, 1998). The 

median total nitrogen concentrations for the Flint 

River and Hester Creek during the summer growth 

period were 2.0 and 1.2 milligrams per liter (mg/L), 

respectively, compared with a threshold value of 

1.5 mg/L for temperate streams. The median total 

phosphorus concentrations for the Flint River and Hester Creek during the summer growth period were 0.12 

and 0.05 mg/L, compared with a threshold value of 

0.075 mg/L for temperate streams. 

Comparisons of the thresholds indicating 

eutrophic potential with the Flint River Basin data during 1999 should be made with caution for the following reasons. 

1. Nutrient concentrations above the threshold do not 

necessarily cause eutrophication because other 

factors, such as turbidity and stream shading, 

influence the relation between nutrient concentrations and aquatic-plant productivity.

2. Conversely, eutrophication may occur even where 

observed nutrient concentrations are well below 

the threshold.

3. Comparison of nutrient concentrations in 1999 with 

thresholds may be of limited use for evaluating 

long-term conditions in the Flint River Basin 

because of the below-normal rainfall and streamflow during the sampling period. 

The seasonal pattern of nitrogen (specifically 

nitrate) and phosphorus concentrations differed 

between the Flint River and Hester Creek sites. Baseflow concentrations of nitrate (fig. 15) and dissolved 

phosphorus in Hester Creek were significantly lower 

(p < 0.05, Wilcoxon rank sum test) during the period 

August through November 1999 when compared with 

the rest of the study period; this pattern partly is attributed to nutrient uptake by aquatic plants. In contrast, 

base-flow concentrations of these constituents in the 

Flint River during the summer equaled or exceeded 

base-flow concentrations during other seasons. The 

higher base-flow concentrations of nitrate and phosphorus during the summer accounted for the higher 

median concentration in the Flint River when compared with concentrations in Hester Creek and also 

when compared with threshold values indicating 

eutrophic potential. Base-flow concentrations of nitrogen and phosphorus also were elevated in the tributary 

Mountain Fork Creek during May and September (discussed in the following section).

Estimates of unit-area inputs of nitrogen and 

phosphorus to the watersheds for the Hester Creek and 

Flint River sites are similar, except for inputs from 

livestock waste, which are higher (almost double) for 

Hester Creek when compared with the Flint River 

(Appendix C). In contrast to unit-area inputs, annual 

instream yields for nitrogen and phosphorus were 

higher for the Flint River when compared with Hester 

Creek: 3.0 and 2.1 tons per square mile per year 

[(tons/mi2)/yr], respectively, for total nitrogen, and 

0.34 and 0.20 (tons/mi2

)/yr, respectively, for total 

phosphorus (Appendix C). Consequently, the ratios of 

unit-area export (instream yield) to unit-area input for 

nitrogen and phosphorus are about three times greater 

for the Flint River when compared with Hester Creek 

(Appendix C). This disparity in the ratio may be due to 

differences in the processes by which the inputs from 

the two watersheds are transported from the land surface to the stream channel, or to inaccurate or 

inappropriate estimates of input, or to other important 

sources of nutrients not quantified in this analysis.

Despite differences between the two sites in 

seasonal- and streamflow-related patterns of concentrations and differences in median concentrations and 

instream yield, estimates of flow-weighted mean concentrations of nutrients compare closely (Appendix C; 

flow-weighted mean concentration is calculated as the 

ratio of annual instream load to annual mean streamflow). The flow-weighted mean concentrations for 

water year 1999 for both sites were 1.8 and 0.2 mg/L 

for total nitrogen and total phosphorus, respectively. 
24 Water Quality of the Flint River Basin, Alabama and Tennessee, 1999-2000
Relation of Storm Transport of Selected Pesticides...City of Huntsville, Alabama 25

These values can be placed in a regional context by 

comparing with the statistical distribution of estimated 

values of annual flow-weighted mean concentrations 

from two different USGS nutrient data sets from the 

southeastern region of the United States. The first data 

set is from 16 streams draining undeveloped basins, 

monitored during 1990-95 (Clark and others, 2000). 

The second data set is from 24 streams draining 

mainly agricultural basins (agricultural land use in the 

watershed exceeds 50 percent) that were monitored 

during 1993-97 (J. Stoner, U.S. Geological Survey, 

written commun., 2000). The values for total nitrogen 

and total phosphorus at Flint River and Hester Creek 

are well above the 90th percentile values of their 

respective distributions for undeveloped basins in the 

southeastern region of the United States (fig. 16), indicating that these sites are nutrient enriched compared 

with background levels. When compared with concentrations from the set of 24 agricultural basins in the 

southeastern region, the concentrations from the Flint 

River and Hester Creek were slightly above the 

regional median.

Spatial Variation of Concentrations During Base 

Flow

Nutrient-concentration data were collected from 

the network of eight stream sites in the Flint River 

Basin during base flow in May and September 1999 

(fig. 14). The spatial pattern of nutrient concentrations 

was compared with the pattern for various watershed 

characteristics including percentage of pastureland and 

percentage of cultivated land; acreage of cotton, corn, 

and soybeans; and density of livestock and failing septic systems (table 2). Base-flow nitrogen concentrations did not correlate with any of these watershed 

characteristics; concentrations were highest for Mountain Fork Creek (site S3), but watershed characteristics 

that would indicate high nutrient input were not in the 

high ends of their respective ranges for the Mountain 

Fork Creek watershed (table 2). When this site was 

removed from the data set (n = 7 for the trimmed set), 

correlation was significant (p = 0.01) between percent 

of watershed in cultivated land and total nitrogen concentration, and was stronger for total nitrogen concentration during September (r = 0.9) when compared 

with the concentration during May (r = 0.7). Correlation also was significant (r = 0.8, p = 0.02) between 

cotton acreage and total phosphorus concentration 

(May only). Correlations were not significant between 

density of livestock or failing septic systems and 

base-flow nutrient concentrations; however, this 

analysis may not accurately evaluate the contribution 

from livestock, as stream access by livestock was not 

considered.

The elevated concentrations of nitrogen and 

phosphorus at Mountain Fork Creek (site S3) may be 

caused by input from a nutrient source not included in 

this analysis. During a separate base-flow sampling 

project of the Mountain Fork Creek watershed on 

May 15, 2000, concentrations of dissolved nitrate 

were elevated (greater than 2 mg/L) in samples from 

three sites near the downstream end of Mountain Fork 

Creek, but concentrations were at trace levels 

(0.1 mg/L) in samples from two upstream sites (U.S. 

Geological Survey, unpub. data, 2001). The Mountain 

Fork Creek tributary made the largest contribution of 

nutrients to the Flint River during base flow; 42 and 

74 percent of the summed tributary load of total nitrogen during May and September 1999 sampling, 

respectively, and 85 and 98 percent of the summed 

tributary load of total phosphorus during May and 

September 1999 sampling, respectively. The elevated 

concentrations of nitrogen and phosphorus in Mountain Fork Creek may have contributed to the elevated 

base-flow concentrations of nitrate and phosphorus 

observed in the Flint River as compared to Hester 

Creek (discussed in the previous section).

RELATION OF STORM TRANSPORT OF 

SELECTED PESTICIDES IN THE FLINT 

RIVER BASIN TO CONCENTRATIONS IN 

THE SOURCE FOR DRINKING WATER 

FOR THE CITY OF HUNTSVILLE, 

ALABAMA

About 40 percent of the public water supply for 

the City of Huntsville, Ala., is withdrawn from the 

right bank of the Tennessee River at mile 334 (South 

Parkway Water Treatment Plant), about 5 mi. downstream of the confluence with the Flint River (also on 

the right bank, at river mile 339). The watershed and 

presumed source area for the Tennessee River at the 

Huntsville intake encompasses a 25,000-mi2 area that 

is predominantly (about 60 percent) forested land. 

Numerous impoundments along the Tennessee River 

upstream from the Huntsville intake regulate streamflow and dampen short-term fluctuations in streamflow and water quality caused by runoff. During 

storms, however, the quality of water at the intake is 

greatly affected by the smaller (570 mi2), 
26 Water Quality of the Flint River Basin, Alabama and Tennessee, 1999-2000

predominantly agricultural Flint River Basin as a 

result of two factors: larger percentages of flow from 

the Flint River to the regulated Tennessee River during 

storms (as high as 30 percent, compared with the 

drainage-area ratio of 2 percent), and incomplete mixing at the confluence of the Flint and Tennessee Rivers. Comparison of turbidity measured in samples 

from the Huntsville intake water with runoff events in 

the Flint River (fig. 17) demonstrates the influence of 

inputs of streamflow from the Flint River on suspended material in the Tennessee River and at the 

intake. 

One of the objectives of this study was to determine whether the observed incomplete mixing in the 

Tennessee River also affects transport of dissolved 

constituents; that is, constituents that may not be 

removed during treatment (filtration) of the intake 

water supply. Other studies have shown that several 

pesticides commonly transported in the dissolved 

phase (for example, atrazine, cyanazine, and metolachlor, which were detected frequently at sites 

throughout the Flint River Basin) are not completely 

removed during conventional water treatment (Miltner 

and others, 1989). A special storm sampling project 

was conducted April 2-5, 2000, with the assistance of 

staff of the South Parkway Water Treatment Plant, in 

order to test the hypothesis that during high flow 

events in the Flint River Basin, the quality of water 

(both suspended and dissolved material) withdrawn 

from the right bank of the Tennessee River at the 

South Parkway intake is more similar to water quality 

of the Flint River than to water quality of the main 

channel of the Tennessee River. Rainfall amounts during April 2-5 were greater in the Flint River Basin 

(about 5 in.) than in the rest of the Tennessee Valley 

(about 1 in.); consequently, the Flint River contributed 

almost 15 percent of the total streamflow in the Tennessee River at mile 334 (TRM 334) during this 
Relation of Storm Transport of Selected Pesticides...City of Huntsville, Alabama 27

 

period. The sampling sites for the Tennessee River are 

described in tables 1 and 2. Streamflow and atrazine 

concentrations in the Flint and Tennessee Rivers during the storm are shown in figure 18. 

In water samples collected at the South Parkway 

intake, peak concentrations of all target pesticides for 

which drinking-water standards have been established 

were below those standards. Comparison of concentrations among the four sites supports the hypothesis that 

the chemical load from the Flint River (entering at 

TRM 339) strongly influenced water quality at TRM 

334 near the intake during this storm. Concentrations 

of atrazine (fig. 18), acetochlor, carbofuran, diazinon, 

and metolachlor were at least a factor of five times 

greater in the intake water compared to the Tennessee 

River upstream from the Flint River. In addition, the 

higher concentrations in the intake and right channel 

of the Tennessee River main stem compared with the 

lower concentrations in the left channel of the main 

stem near Hobbs Island (all at TRM 334) indicate that 

the mass of dissolved chemicals contributed by the 

Flint River is not completely mixed with the Tennessee 

River between TRM 339 and TRM 334, influencing 

water quality more strongly than would be expected 

from mass balance considerations. For example, the 

expected peak concentration of atrazine in the intake 

water (based on mass balance calculations using data 

from the Flint River and TRM 340) is 0.62 μg/L, the 
28 Water Quality of the Flint River Basin, Alabama and Tennessee, 1999-2000

 
Relation of Storm Transport of Selected Pesticides...City of Huntsville, Alabama 29

Figure 18. Streamflow and atrazine concentrations in the Flint River, the Tennessee River, and at the intake 

to the City of Huntsville’s water-treatment plant, April 2-7, 2000—Continued.
30 Water Quality of the Flint River Basin, Alabama and Tennessee, 1999-2000

observed peak concentration was 2.1 μg/L (compare 

with the drinking-water standard of 3 μg/L). The discussion of Flint River water quality in previous sections of this report, therefore, has implications for 

drinking-water quality for the City of Huntsville.

SUMMARY

Eight stream sites in the Flint River Basin, Alabama and Tennessee, were monitored during January 

1999 through May 2000 to characterize patterns in the 

occurrence of pesticides, fecal-indicator bacteria, and 

nutrients in relation to season and streamflow conditions and to land-use patterns. In addition, three sites 

on the Tennessee River near the confluence with the 

Flint River were monitored to relate water quality in 

the Flint River to water quality in a drinking-water 

source for the City of Huntsville. Water-quality conditions in the Flint River Basin during the monitoring 

period may have deviated from normal as a result of 

below-normal rainfall and streamflow. Transport of 

water-quality constituents, including pesticides, bacteria, and nutrients, in storm runoff to the streams was 

probably lower than normal during many months.

Occurrence of pesticides in the Flint River and 

its tributary Hester Creek was compared to information about agricultural pesticide use in the watershed. 

In general, pesticides detected most frequently and at 

the highest concentrations in streams corresponded to 

the pesticides with the highest rates of use in the 

watersheds and with the highest potential (based on 

the pesticide’s chemical and physical properties) for 

transport in runoff or ground water. For example, atrazine, which is the second most heavily applied pesticide, or one of its metabolites was detected in 100 and 

93 percent of the samples from the Flint River and 

Hester Creek, respectively. In contrast, glyphosate, the 

most heavily applied pesticide, was detected in only 

17 percent of samples from Hester Creek; this contrast 

between rate of use and instream occurrence may be 

caused by glyphosate’s strong affinity to soil particles 

and its resulting low potential for leaching to runoff or 

ground water. Detections of fluometuron, norflurazon, 

and atrazine were more frequent (by a margin of 

15 percent or greater) in samples from the Flint River 

as compared to pesticide detection frequencies at 62 

agricultural stream sites across the Nation. Detections 

of fluometuron in the Flint River were more frequent 

even when compared to a cotton-cultivation subset of 

the 62 sites.

Less than 5 percent of the estimated mass of 

pesticides applied annually to agricultural areas in the 

Flint River Basin was transported to the stream at the 

monitoring points on the Flint River near Brownsboro, 

Ala., and on Hester Creek near Plevna, Ala. The 

amount transported instream ranged from 0.06 percent 

(for trifluralin) to 4.7 percent (for norflurazon) of the 

amount applied. The pesticides for which the highest 

ratios (> 3 percent) were observed—atrazine, metolachlor, fluometuron, and norflurazon—are preemergent herbicides applied to the soil before the crops 

have emerged, which increases the likelihood of their 

transport in surface runoff.

The environmental significance of the observed 

pesticide concentrations was evaluated by comparing 

these concentrations with water-quality criteria to protect aquatic life. For most pesticides, maximum concentrations did not exceed aquatic-life criteria; 

however, maximum concentrations of atrazine, cyanazine, and malathion exceeded aquatic-life criteria in at 

least one sample each. Concentrations near or exceeding the aquatic-life criteria occurred only during the 

spring and summer months (April through July), and 

generally occurred during storm flows. The aquaticlife criteria generally are based on the results of singlechemical toxicity tests and do not consider the synergistic effects of exposure to low-level pesticide mixtures, such as the mixtures detected in samples from 

the Flint River and Hester Creek sites. For example, 

every stream sample had detectable levels of at least 

two pesticides; 64 percent of the samples contained a 

mixture of at least five pesticides.

E. coli concentrations in the Flint River and 

Hester Creek exceeded the U.S. Environmental Protection Agency single-sample criterion of 

406 col./100 mL for recreation in almost all storm 

samples, and in samples collected up to 6 days following a storm. Concentrations in the Flint River were 

strongly correlated with sample turbidity. Exceedance 

of the single-sample E. coli criterion for recreation can 

be estimated empirically from turbidity measurements 

using linear regression. For the Flint River site, a sample with turbidity equal to 22 NTU has an expected 

E. coli concentration equal to the criterion for 

recreation.

When compared with nutrient data from a set of 

24 agricultural basins across the southeastern region of 

the United States, concentrations of nitrogen and phosphorus in the Flint River and Hester Creek were 

slightly above the regional median. Nutrient 
References Cited 31

concentrations in the Flint River generally exceeded 

thresholds indicating eutrophic potential, whereas 

nutrient concentrations in samples from Hester Creek 

were generally below the thresholds. Seasonal variation of nutrient concentrations in the Flint River, 

marked by increased base-flow concentrations of 

nitrate and phosphorus during the period May through 

October, differed from the pattern expected based on 

nutrient dynamics. The seasonal increase in base-flow 

concentrations accounted for the higher median concentration in the Flint River compared with the threshold values indicating eutrophic potential. Nutrient 

input from the Mountain Fork Creek tributary may 

have contributed to this pattern. During two base-flow 

periods in May and September 1999, Mountain Fork 

Creek contributed more than 40 percent of the 

summed tributary load of total nitrogen, and more than 

80 percent of the summed tributary load of total phosphorus.

The base-flow concentrations of certain pesticides, E. coli, and nutrients at eight sites in the Flint 

River Basin were compared with land-use information. 

The highest base-flow concentrations of aldicarb sulfoxide, fluometuron, and phosphorus occurred in the 

tributaries with the greatest density of cotton acreage 

in the watershed. Similarly, base-flow concentrations 

of total nitrogen were correlated with the percentage 

of cultivated land in the watershed. Base-flow concentrations of E. coli during May were correlated most 

strongly with watershed density of livestock population, whereas concentrations of E. coli during September, after a prolonged dry period, were correlated most 

strongly with the estimated density of failing septic 

systems in the watershed. Lack of information about 

distribution of stream access by livestock, however, 

weakened the analysis of correlation between livestock and base-flow concentrations of E. coli and 

nutrients.

Input of dissolved and suspended chemicals 

from the Flint River during storms influences water 

quality in the reach of the Tennessee River from which 

the City of Huntsville, Alabama, withdraws about 

40 percent of its drinking water. The increased influence during storms is a result of two factors: larger 

percentages of flow from the Flint River to the flowregulated Tennessee River during storms, and incomplete mixing at the confluence of the Flint and Tennessee Rivers. During the storm of April 2-5, 2000, 

concentrations of several pesticides were at least a factor of five times greater in Huntsville’s intake water 

compared with concentrations in the Tennessee River 

upstream from the Flint River, although concentrations 

of all pesticides were below the U.S. EPA drinkingwater standards at all sites on the Tennessee River and 

in Huntsville’s intake water.

REFERENCES CITED

Adams, J.F., Mitchell, C.C., and Bryant, H.H., 1994, Soil 

test fertilizer recommendations for Alabama crops: 

Alabama Agricultural Experiment Station, Auburn 

University, Agronomy and Soils Department Series 

No. 178, 68 p.

Alabama Department of Environmental Management, 2000, 

Alabama’s 2000 water quality report to Congress 

(Clean Water Act 305(b) Report): Alabama Department of Environmental Management, Montgomery, 

Alabama, variously paginated.

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

concentrations and yields in undeveloped stream 

basins of the United States: Journal of American Water 

Resources Association, v. 36, no. 4, p. 849-860.

Crawford, C.G., 1996, Estimating mean constituent loads in 

rivers by the rating-curve and flow-duration, ratingcurve methods: Bloomington, Indiana, Indiana University, Ph.D. dissertation, 245 p.

Dodds, W.K., Jones, J.R., and Welch, E.B., 1998, Suggested 

classification of stream trophic state: distributions of 

temperate stream types by chlorophyll, total nitrogen, 

and phosphorus: Water Research, v. 32, no. 5, 

p. 1455-1462.

Dolan, D.M., Yui, A.K., and Geist, R.D., 1981, Evaluation 

of river load estimation methods for total phosphorus: 

Journal of Great Lakes Research, v. 7, p. 207-214.

Environment Canada, 1999, Canadian water quality guidelines for the protection of aquatic life, Summary tables: 

accessed December 18, 2000 at URL 

http://www.ec.gc.ca/ceqg-rcqe.

Gilliom, R.J., Alley, W.M., and Gurtz, M.E., 1995, Design 

of the National Water-Quality Assessment Program: 

occurrence and distribution of water-quality conditions: U.S. Geological Survey Circular 1112, 33 p.

Griffith, G.E., Omernik, J.M., and Azevedo, S.H., 1997, 

Ecoregions of Tennessee: U.S. Environmental Protection Agency National Health and Environmental 

Effects Research Laboratory EPA/600/R-97/022, 51 p.

Hoos, A.B., Robinson, J.A., Aycock, R.A., Knight, R.R., 

and Woodside, M.D., 2000, Sources, instream transport, and trends of nitrogen, phosphorus, and sediment 

in the lower Tennessee River Basin, 1980-96: U.S. 

Geological Survey Water-Resources Investigations 

Report 99-4139, 96 p.

International Joint Commission, 1989, Article 5.-Standards, 

other regulatory requirements, and research, in Revised 
32 Water Quality of the Flint River Basin, Alabama and Tennessee, 1999-2000

Great Lakes water quality objectives of 1978, volume 

2, an IJC report to the governments of the United 

States and Canada: Windsor, Ontario, Canada, International Joint Commission, accessed December 18, 2000 

at URL http://www.ijc.org/agree/quality.html#art5

Kingsbury, J.A., Hoos, A.B., and Woodside, M.D., 1999, 

Environmental setting and water-quality issues in the 

lower Tennessee River Basin: U.S. Geological Survey 

Water-Resources Investigations Report 99-4080, 44 p.

Martin, J.D., Gilliom, R.J., and Schertz, T.L., 1999, Summary and evaluation of pesticides in field blanks collected for the National Water-Quality Assessment 

Program, 1992-1995: U.S. Geological Survey OpenFile Report 98-412, 102 p. 

Miltner, R.J., Baker, D.B., Speth, T.F., and Fronk, C.A., 

1989, Treatment of seasonal pesticides in surface 

waters: Journal of the American Water Works Association, v. 81, no. 1, p. 43-52.

Mueller, D.K., Martin, J.D., and Lopes, T.J., 1997, Qualitycontrol design for surface-water sampling in the 

National Water-Quality Assessment Program: U.S. 

Geological Survey Open-File Report 97-223, 17 p.

Shelton, L.R., 1994, Field guide for collecting and processing stream-water samples for the National WaterQuality Assessment Program: U.S. Geological Survey 

Open-File Report 94-455, 42 p.

Tennessee Department of Environment and Conservation, 

2000, The 1998 303(d) list: Division of Water Pollution Control, accessed December 15, 2000 at URL 

http://www.state.tn.us/environment/water.htm

U.S. Environmental Protection Agency, 1986, Ambient 

water quality criteria for bacteria, 1986: Cincinnati, 

Ohio, U.S. Environmental Protection Agency, 

EPA 440/5-84-002, 18 p.

———1996, Drinking water regulations and health advisories: Washington, D.C., U.S. Environmental Protection 

Agency, Office of Water, EPA 822-B-96-002, variously 

paginated.

———1999a, International notice: cyanazine pesticide voluntarily cancelled and uses phased out: Office of Pesticide Programs, accessed June 22, 2001 at URL 

http://www.epa.gov/oppfead1/17b/cyanazin.htm

———1999b, Compilation of national recommended 

water-quality criteria and EPA’s process for deriving 

new and revised criteria: Office of Water, accessed 

December 18, 2000 at URL 

http://www.epa.gov/OST/standards/wqcriteria.html

U.S. Geological Survey, 2001, Pesticides in streams; summary statistics; results of the National Water Quality 

Assessment Program (NAWQA), 1992-1998: U.S. 

Geological Survey data available on the World Wide 

Web, accessed December 5, 2001 at URL 

http://water.wr.usgs.gov/pnsp/pestsw
APPENDIXES

Appendix A 35

APPENDIX A. METHODS FOR 

ESTIMATING WATERSHED INPUT AND 

INSTREAM YIELD OF PESTICIDES, 

NITROGEN, AND PHOSPHORUS FOR THE 

FLINT RIVER BASIN, ALABAMA AND 

TENNESSEE

Watershed Input

The estimated agricultural inputs of pesticides 

presented in Appendix B were summed from estimates 

of application to three major crops (corn, cotton, and 

soybeans), which were calculated from crop acreage 

and pesticide application rates. Estimates in 

Appendix B are for unit-area input, or the ratio of 

mass of pesticide to the total area of the watershed. 

Information about pesticide application rates was provided by Joseph Berry (U.S. Natural Resource Conservation Service, Ala., written commun., 2000), William 

Abbott (U.S. Natural Resource Conservation Service, 

Tenn., written commun., 2000), Mark Hall (Agricultural Extension Service, Madison County, Ala., oral 

commun., 2000), and David Qualls (Agricultural 

Extension Service, Lincoln County, Tenn., written 

commun., 2000). Crop-acreage estimates for 1999-

2000 were provided by Joseph Berry and William 

Abbott (U.S. Natural Resource Conservation Service, 

written commun., 2000). Although nonagricultural 

inputs of certain pesticides (home and garden use and 

roadway maintenance) account for part of the pesticide 

input to the watershed, these were not estimated for 

this study.

Inputs of nitrogen and phosphorus from various 

agricultural and nonagricultural sources in a watershed 

were estimated for the Flint River and Hester Creek 

using local information, along with methods and coefficients described in Hoos and others (2000). Inputs 

from fertilizer were estimated using application recommendations from Adams and others (1994) for the 

three major crops. Wastewater inputs of nitrogen and 

phosphorus were calculated based on 1999 to 2000 

effluent monitoring data provided by Pat Morgan (City 

of Huntsville, Ala., written commun., 2000). Inputs of 

nitrogen and phosphorus from failing septic systems 

and livestock waste were calculated based on census 

estimates from Victor Payne (Alabama Soil and Water 

Conservation Committee, written commun., 1999); 

these estimates were extrapolated from the Alabama 

part of the watershed to the entire watershed on a perunit-area basis.

Instream Yield

Instream loads of selected pesticides and nutrients were estimated for the Flint River and Hester 

Creek by either the rating-curve or ratio-estimator 

method, using the program LOADEST2 (Crawford, 

1996). For most pesticides, instream loads were estimated using the rating-curve method with a seasonal 

covariate function to account for the spring pulse in 

pesticide loads. This approach effectively creates two 

rating-curve models for each pesticide data set: one 

model for the pesticide-application season and another 

for the rest of the year (C.G. Crawford, written commun., 1999). The ratio-estimator method (Dolan and 

others, 1981) was used in place of the rating-curve 

method to estimate instream loads for five pesticides 

(cyanazine, carbaryl, carbofuran, trifluralin, and pendimethalin) for which 85 percent or more of the samples had concentrations less than the method detection 

limit. The estimates from the ratio-estimator method 

are less reliable than those from the rating-curve 

method because they do not account for seasonal- and 

streamflow-related variability. 

Estimates of annual instream yield 

(Appendixes B and C) were calculated by dividing 

instream load by watershed area. These estimates are 

considered interim results (instream yields may be 

recalculated after additional years of planned data collection) and should be interpreted with caution as the 

calibration data set is limited to 17 months of data, and 

includes fewer than 40 samples for most constituents.
36 Water Quality of the Flint River Basin, Alabama and Tennessee, 1999-2000

Appendix B. Input and export estimates and detection frequency of selected pesticides for the Flint River and Hester Creek, 

1998-2000

[Unit-area input reported in pounds of active ingredient per square mile of total watershed area per year; input estimates are for use on crops during 1998; 

unit-area export reported in pounds per square mile per year; export estimates are for water year 1999; export ratio reported in percent and calculated as 

(export/input)*100; frequency of detection reported in percent and calculated for the period January 1999 - May 2000; >, greater than; μg/L, micrograms per 

liter; I, insecticide; H, herbicide; F, fungicide; NRU, not estimated because no reported use for crop pest management in the Flint River Basin; ND, no data 

(not targeted for analysis); --, data not sufficient for estimating export because most observations were below the method detection limit]

a Export estimates and detection frequency include estimated mass and detection frequency of metabolites.

b Estimates of export and export ratio are subject to error because concentrations were reported with the “E” data qualifier, signifying that although the 

pesticide was qualitatively identified as present, the reported concentration has greater uncertainty than other values.

c

 Reported value for detection frequency is a minimum estimate because some observations were reported as less than a value that was larger than the 

0.01 μg/L threshold.

Watershed for Flint River near Brownsboro, 

Ala.

Watershed for Hester Creek at Buddy 

Williamson Road near Plevna, Ala.

Chemical 

(trade name) Type

Unitarea 

input

Unitarea 

export

Export 

ratio, in 

percent

Frequency 

of 

detection 

> 0.01 μg/L

Unitarea 

input

Unitarea 

export

Export 

ratio, in 

percent

Frequency 

of 

detection 

> 0.01 μg/L

Pesticides reported as used for crop pest management in the Flint River Basin

Aldicarb (Temik) a, b I 19 0.071 0.37 48 20 0.011 0.06 21

Atrazine (Aatrex) a H 48 2.0 4.1 100 83 1.5 1.8 93

Carbaryl (Sevin) b I 3.6 0.050 1.4 14 6.2 0.062 1.0 10

Carbofuran (Furadan) b I 1.1 0.028 2.7 17 1.8 -- -- 0

Chlorpyrifos (Lorsban) I 6.4 -- -- 0 9.3 -- -- 0

Cyanazine (Bladex) H 12 0.18 1.5 10 18 0.055 0.30 13

Dicrotophos (Bidrin) I 6.6 ND ND ND 6.9 ND ND ND

Fluometuron (Cotoran) H 18 0.59 3.2 87 19 0.19 1.0 76

Glyphosate (Roundup) H 140 -- -- c

 0 183 -- -- c 17

Metalaxyl (Ridomil) F 2.9 -- -- 14 3.0 -- -- 31

Metolachlor (Dual) H 16 0.22 1.4 48 22 0.78 3.5 59

Methomyl (Lannate) a I 1.1 -- -- 0 1.8 -- -- c

 7

Norflurazon (Zorial) b H 2.1 0.10 4.7 87 2.2 -- -- 7

Pendimethalin (Prowl) H 4.8 0.094 1.9 14 8.3 0.10 1.2 13

PCNB (Terraclor) I 29 ND ND ND 30 ND ND ND

Prometryn (Cotton Pro) H 3.2 -- -- c

 32 3.3 -- -- c 0

Trifluralin (Treflan) b H 21 0.013 0.061 3 25 -- -- 0

Pesticides for which input was not estimated (not reported as used for crop pest management in the Flint River Basin), but which were detected at 

concentrations > 0.01 μg/L in 10 percent or more of samples

2,4-dichlorophenoxyacetic 

acid (2,4-D) H NRU -- -- c

 22 NRU -- -- c 34

Acetochlor (Surpass) H NRU -- -- 10 NRU -- -- 0

Bentazon (Basagran) H NRU -- -- 9 NRU -- -- 10

Diazinon (Spectracide) I NRU -- -- 14 NRU -- -- 5

Diuron (Karmex or Direx) H NRU -- -- c

 13 NRU -- -- c 0

Malathion (Cythion) I NRU -- -- 10 NRU -- -- 5

Simazine (Princep) H NRU 0.075 -- 48 NRU 0.022 -- 8

Sulfometuron-methyl (Oust) H NRU -- -- c 17 NRU -- -- c

 14

Tebuthiuron (Spike) H NRU -- -- 10 NRU -- -- 13
Appendix C 37

Appendix C. Input and export estimates of nitrogen and phosphorus for the Flint River and Hester Creek, 1998-99

[Unit-area inputs reported in tons of element per square mile per year; input estimates are for 1998, with some exceptions (noted in the table); unit-area 

export reported in tons per square mile per year; estimates of export and flow-weighted mean concentration are for water year 1999; export ratio reported in 

percent and calculated as (export/input)*100; flow-weighted mean concentration reported in milligrams per liter and calculated as the ratio of export to mean 

streamflow, with appropriate unit conversions; -, negative number because crop harvest represents a nutrient sink; balance of input to agricultural lands 

calculated as sum of inputs from fertilizer application, livestock waste, and (for nitrogen) crop fixation, minus removal as crop harvest]

Watershed for Flint River near 

Brownsboro, Ala.

Watershed for Hester Creek at Buddy 

Williamson Road near Plevna, Ala.

Export, 1999 data Export, 1999 data

Source and nutrient

Unitarea 

input

Unitarea 

export

Export 

ratio

Flowweighted 

mean 

concentration

Unitarea 

input

Unitarea 

export

Export 

ratio

Flowweighted 

mean 

concentration

Agricultural activities

Cropland fertilizer

Nitrogen 5.0 5.8

Phosphorus 0.99 1.2

Crop fixation

Nitrogen 3.5 4.3

Livestock waste

Nitrogen 3.4 7.7

Phosphorus 1.1 2.5

Harvest

Nitrogen -7.7 -10

Phosphorus -0.83 -1.1

Balance of input to 

agricultural lands

Nitrogen 4.2 7.4

Phosphorus 1.3 2.7

Wastewater (1999)

Nitrogen 0.035 0

Phosphorus 0.010 0

Atmospheric deposition (1999)

Nitrogen 0.14 0.13

Failing septic systems 

Nitrogen 0.085 0.10

Phosphorus 0.025 0.029

Sum of all inputs

Nitrogen 4.4 7.6

Phosphorus 1.3 2.7

Nitrogen 3.0 67 1.8 2.1 27 1.8

Phosphorus 0.34 26 0.20 0.20 7.6 0.18