Instream Investigations in the Beaver Creek

Watershed in West Tennessee,

1991-95

Compiled by TOM D. BYL and K.A. CARNEY

U.S. GEOLOGICAL SURVEY 

Water-Resources Investigations Report 96-4186

Nashville, Tennessee 

1996
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

Gordon P. Eaton, Director

The use of firm, trade, and brand names in this report is for identification purposes 

only and does not constitute endorsement by the U.S. Geological Survey.

For addtional information write to:

District Chief 

U.S. Geological Survey 

810 Broadway, Suite 500 

Nashville, Tennessee 37203

Copies of this report can be purchased 

from:

U.S. Geological Survey 

Branch of Information Services 

Box 25286 

Denver, CO 80225-0286
FOREWORD

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

Department of Agriculture, began a long-term scientific investigation in 1989 to 

evaluate the effect of agricultural activities on water quality and the effectiveness 

of agricultural best management practices in the Beaver Creek watershed, West 

Tennessee. In 1 993 as a part of this study, the USGS, in cooperation with the Natural Resources Conservation Service, Shelby County Soil and Water Conservation District, and the Tennessee Soybean Promotion Board, began an evaluation 

of the physical, chemical, biological, and hydrological factors that affect water 

quality in streams and wetlands, and instream resource-management systems to 

treat agricultural nonpoint-source runoff and improve water quality. The purpose 

of this report is to present the results of three studies of stream and wetland investigations and a study on the transport of aldicarb from an agricultural field in the 

Beaver Creek watershed.

A natural bottomland hardwood wetland and an artificially constructed wetland were evaluated as instream resource-management systems. These two studies 

showed that wetlands are an effective way to improve the quality of agricultural 

nonpoint-source runoff. The wetlands reduced concentrations and loads of suspended sediments, nutrients, and pesticides in the streams.

A third paper documents the influence of riparian vegetation on the biological structure and water quality of a small stream draining an agricultural field. A 

comparison of the upper reach lined with herbaceous plants and the lower reach 

with mature woody vegetation showed a more stable biological community structure and water-quality characteristics in the woody reach than in the herbaceous 

reach. The water-quality characteristics monitored were pH, temperature, dissolved oxygen, and specific conductance. The herbaceous reach had a greater 

diversity and abundance of organisms during spring and early summer, but the 

abundance dropped by approximately 85 percent during late summer.

A fourth study describes the transport of aldicarb and its metabolites aldicarb sulfoxide and aldicarb sulfone in runoff at a small stream draining a cotton 

field. During 1991 to 1995, aldicarb and its metabolites were detected in runoff 

events. The highest concentrations occurred when aldicarb was applied to the field 

just hours before a rain storm. Aldicarb was not detectable in runoff a few weeks 

after application. The metabolites of aldicarb were detectable for 76 days after 

application.

These studies demonstrate that streambank vegetation and wetlands have a 

significant influence on stream water quality. The importance of weather conditions to herbicide application and runoff also is evident. This information can be 

used by resource managers to sustain and improve our Nation's streams for future 

generations.

W Harry Doyle 

Supervisory Hydrologist

Foreword ill

CONTENTS

Nutrient and sediment loads in a channelized stream and a nonchannelized wetland 

stream in the Beaver Creek watershed, West Tennessee

Herbert H. Cochrane and Shannon D. Williams............................................................................... 3

Evaluation of a constructed wetland to control agricultural row-crop nonpoint-source pollution

John A. Smink and Tom D. Byl........................................................................................................ 11

Influence of riparian vegetation on the biological structure and processing function of a 

channelized stream in West Tennessee

Tom D. Byl, Yun Jiao, Susan S. Hutson ........................................................................................... 21

Transport of aldicarb and aldicarb metabolites in runoff from agricultural fields 

in the Beaver Creek watershed, West Tennessee

Shannon D.Williams........................................................................................................................ 29

Contents
CONVERSION FACTORS

Multiply By To obtain

inch (in.) 16.39 centimeters

foot (ft) 0.3048 meter

mile 1.609 kilometer

cubic foot (ft3) 0.02832 cubic meter

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

acre 0.4047 hectare

acre-feet 1,233 cubic meter

acre-feet 0.001233 cubic hectometer

pound, avoirdupois 0.4536 kilogram

pounds per acre 1.1204 kilograms per hectare

ton, short 0.9072 megagram

vi Instream Investigations in the Beaver Creek Watershed in 

West Tennessee, 1991-95
Nutrient and Sediment Loads in a Channelized Stream and a 

Nonchannelized Wetland Stream in the Beaver Creek 

Watershed, West Tennessee

By HERBERT H. CQCHRANE and SHANNON D. WILLIAMS________

U.S. GEOLOGICAL SURVEY

Prepared in cooperation with the

Shelby County Soil and Water Conservation District and the

U.S. Department of Agriculture,

Natural Resources Conservation Service

Nutrient and Sediment Loads in a Channelized Stream 

and a Nonchannelized Wetland Stream in the Beaver 

Creek Watershed, West Tennessee

By Herbert H. Cochrane and Shannon D. Williams

Abstract

In 1991, the U.S. Geological Survey began 

a research program to assess the effect of agriculture on water quality and the effectiveness of best 

management practices in the Beaver Creek watershed, West Tennessee. This report presents a comparison of nutrient and sediment concentrations 

and loads in a channelized stream and a nonchannelized stream that flows through a 600-acre bottomland hardwood wetland. Both streams receive 

agricultural runoff from drainage basins of similar size (about 8,000 acres), land use, and 

topography.

Water samples were collected during three 

storm events in 1995; one prior to the planting of 

row crops and two during the growing season 

(April to September). Major differences in concentrations and loads of suspended sediment and 

nutrients were observed between the two streams. 

The channelized stream generally had higher concentrations and loads of suspended sediment and 

nutrients, even when it received less rainfall and 

had less storm runoff than the nonchannelized 

stream. Suspended-sediment loads ranged from 

3.1 to 32 times greater at the channelized stream 

than at the nonchannelized/wetland stream during 

the three storms examined. Ammonia, nitrite and 

nitrate, and phosphorus loads ranged from 1.4 to 

23 times greater at the channelized stream.

INTRODUCTION

Modifications of drainage networks by channelization are common in many agricultural watersheds 

(Hook, 1993; Reedy and Gale, 1994). Channelization

has altered the hydrologic regime of many streams and 

wetland systems, potentially affecting the biological 

and nonbiological functions that are normally associated with these systems (Phillips, 1989; Gilliam, 1994; 

Lowrance and others, 1995). The nature and extent of 

the effects of channel modifications on streams in agricultural settings need to be understood to allow for the 

development and implementation of instream 

resource-management practices.

In 1991, the U.S. Geological Survey (USGS) 

began a research program to assess the effect of agriculture on water quality and the effectiveness of best 

management practices in the Beaver Creek watershed, 

West Tennessee. This report presents a comparison of 

nutrient and sediment concentrations and loads in a 

nonchannelized stream that flows through a 600-acre 

bottomland hardwood wetland and a channelized 

stream. Both streams receive agricultural runoff from 

row crops. The study was conducted in cooperation 

with the Shelby County Soil and Water Conservation 

District and the U.S. Department of Agriculture, 

Natural Resources Conservation Service.

STUDY AREA

The drainage basins of the two streams compared 

in this study are contiguous basins of similar size, land 

use, and topography. The upper Middle Beaver Creek 

Canal basin (7,600 acres) represents a typical example 

of a channelized basin in the Beaver Creek watershed 

(fig. 1). The Baxter Bottom basin (8,000 acres) contains the only nonchannelized bottomland within the 

Beaver Creek watershed. A 600-acre hardwood wetland encompasses the main stem of this drainage network (fig.l). The forested wetland is believed to 

resemble prechannelized drainage conditions for 

bottomlands in the Beaver Creek watershed 

(Ashley, 1910).

Nutrient and Sediment Loads in a Channelized Stream and 3 

a Nonchannelized Wetland Stream
89*40'

(D W W ?II» ta

-" 8. U> 21.<£ QS w

01 - 35*31'

35*27'

89" 32'

TENNESSEE

\Study Area

/ \

EXPLANATION

Basin boundary

A A 

k * /

f. *

Streanvgaging station 0.5 1 MILE

0 0.5 1 KILOMETER

Base from U.S. Geological Survey Mason, 1:24,000, photorevised 1973, Brighton, 1:24,000, photorevised 1973, Covington, 1:24,000, photorevised 1983, Gift, 1:24,000, photorevised 1973

Figure 1. Location of the Middle Beaver Creek and Baxter Bottom basins, West Tennessee.
Land use in both basins is dominated by row 

crops; about 70 percent of the land is under cultivation. Crop distribution and fertilizer application rates 

are similar in the two basins; major crops grown are 

cotton, soybeans, corn, and winter wheat. Soils in the 

drainage basins consist of well to poorly drained silt 

loams, and slopes range from less than 1 percent in the 

bottomlands to 25 percent in the uplands (U.S. Department of Agriculture, Soil Conservation Service, 1993).

DATA COLLECTION

Discharge data were collected at USGS streamgaging stations located at the basin outlets. Rainfall 

data were collected at the Baxter Bottom gaging station; however, rainfall data for Middle Beaver Creek 

had to be estimated using data from surrounding sites 

because of a malfunctioning rain gage at this site.

Water samples were collected during three 

storm events; one prior to planting of row crops and 

two during the summer growing season. Samples were 

collected using two automatic samplers at each station one for the collection of suspended-sediment 

samples and one for nutrient samples. Samplers were 

programmed to collect samples at 10-minute intervals 

at Middle Beaver Creek and at 30-minute intervals at 

Baxter Bottom during storm events. These intervals 

were selected after examining hydrographs for previous storm events at each site. Nutrient samples were 

analyzed at the UGSG Water-Quality Laboratory in 

Ocala, Fla., and sediment samples were analyzed at 

the USGS Sediment Laboratory in Tuscaloosa, Ala.

Discharge was calculated with stage-discharge 

rating curves developed by using methods described 

by Kennedy (1983). Event-mean concentrations for 

storms were calculated by dividing suspendedsediment and nutrient loads by storm-runoff volumes. 

Loads (L) were calculated using the sum of individual 

interval loads:

(1)

i= 1

where

c, is the ith interval of sampled concentration, 

qi is the instantaneous discharge at the time the

sample was collected,

ti is the time interval associated with the sample, 

K is a unit conversion factor, and 

n is the number of samples.

This method assumes that the sampled concentration 

and the corresponding discharge value are representative of the time interval f,-, that is equal to half the time 

from the preceding sample to the current sample plus 

half the time from the current sample to the following 

sample.

NUTRIENT AND SEDIMENT LOADS

The hydrologic responses of Middle Beaver 

Creek and Baxter Bottom to storm events were different and can account for observed variances in nutrient 

and suspended-sediment concentrations and loads. 

Peak discharges at Middle Beaver Creek were higher 

and occurred sooner than at Baxter Bottom during 

similar rainfall events (fig. 2). The differences in the 

hydrologic responses can be attributed to differences 

in the physical features of the drainage basins. The 

Middle Beaver Creek basin has straighter channels 

because of channelization, and it also has a longer and 

narrower drainage area than the Baxter Bottom basin. 

Because of the faster response of the channelized 

stream, the storm-runoff duration was normally much 

shorter than for the nonchannelized stream.

The event-mean concentrations for suspended 

sediment and nutrients were generally greater at Middle Beaver Creek (table 1). The only exception was on 

March 26, 1995, when the mean organic nitrogen concentrations at the two streams were similar. During 

early spring, much of the organic nitrogen is from 

weathered plant material from the previous growing 

season, and little nitrification is taking place.

During the March 26,1995 and May 18,1995 

events, greater storm-runoff volumes and greater sediment and nutrient loads occurred at Middle Beaver 

Creek (table 2). During the June 6, 1995 event, the 

storm-runoff volume at Baxter Bottom was 2.6 times 

greater than at Middle Beaver Creek. Despite the 

greater discharge on June 6 at Baxter Bottom, the total 

loads for various constituents at Middle Beaver Creek 

still ranged from 1.4 to 3.1 times greater than loads at 

Baxter Bottom.

Middle Beaver Creek usually had much higher 

loads of suspended sediment and nutrients than did 

Baxter Bottom (fig. 3). The exception was the organic 

nitrogen loads during the first storm (March 26,1995). 

Suspended-sediment loads ranged from 3.1 to 32 

times greater at Middle Beaver Creek than at Baxter 

Bottom. Although organic nitrogen loads for the two 

sites were similar during the March 26 event, they 

were 1.9 and 21 times greater at Middle Beaver Creek

Nutrient and Sediment Loads in a Channelized Stream and 

a Nonchannelized Wetland Stream
10 tS 20 25 30 35 40 45

Hours from beginning of event

May 18, 1995 

Middle Beaver Creak

5 10 15 20 25

Hours from beginning of event

I 

i

u

2

June 6,1995

Middle Beaver

j ~ ^ Baxter Bottom

0 5 10 15 20 25 30 35 40 45 50 55

Hours from beginning of event

Figure 2. Hydrographs for selected storm-runoff events at Middle Beaver Creek and Baxter Bottom, West Tennessee.

O 3.000

Efoltrtu « Nltita 

£3.Vimcni« 

Etargmlc nUrogm

MARCH 26 MAY IB 

1995

JUNE 06

form of 

phoiphorut

MARCH 26 MAY IB 

1995

JUNE 06

1,200 

t.OOO

0Su«p«nded lediment

MARCH 26 MAY 16 

1995

JUNE 06

Figure 3. Nutrient and sediment loads during selected storm events at Middle Beaver Creek and Baxter Bottom, West 

Tennessee.

6 Instream Investigations in the Beaver Creek Watershed in 

West Tennessee, 1991-95
Table 1. Event-mean concentrations and maximum concentrations of nutrients and suspended sediments for selected 

storms at Middle Beaver Creek and Baxter Bottom, West Tennessee, 1995

[Max., maximum; mg/L, milligrams per liter]

Nitrogen, 

organic

Storm

03/26/95

05/18/95

06/06/95

Station ,Mea" (mg/L)

Middle Beaver 5.7

Baxter Bottom 7.5

Middle Beaver 10.9

Baxter Bottom 3.9

Middle Beaver 6.6

Baxter Bottom 1 .4

Max. 

(mg/L)

6.9

13.0

19.0

6.9

21.0

8.5

Nitrogen, 

ammonia

Mean 

(mg/L)

0.5

0.3

1.1

0.7

1.0

0.1

Max. 

(mg/L)

0.8

1.0

2.2

1.2

2.1

1.5

Nitrogen, 

nitrite and 

nitrate

Mean 

(mg/L)

0.8

0.3

6.0

2.1

6.2

1.1

Max. 

(mg/L)

l.l

1.5

17.0

2.9

9.3

9.3

Phosphorus, 

total

Mean 

(mg/L)

1.5

0.5

3.5

1.1

1.0

0.3

Max. 

(mg/L)

3.1

1.2

7.4

1.4

1.5

1.3

Phosphorus, 

orthophosphate

Mean 

(mg/L)

0.9

0.3

1.1

0.5

0.9

0.2

Max. 

(mg/L)

l.l

0.8

2.0

0.8

1.4

1.3

Suspended 

Sediment

Mean 

(mg/L)

3,233

213

4,621

1,087

2,890

360

Max. 

(mg/L)

7,193

2,767

14,755

1,365

9,877

6,676

Table 2. Rainfall and discharge, and sediment and nutrient loads for selected storms at Middle Beaver Creek and Baxter 

Bottom, West Tennessee, 1995

[ft3/s, cubic feet per second; ft3 , cubic feet; Ibs, pounds; *, estimated values]

Storm Loads

Storm

Storm

Peak runoff 

Rainfall discharge volume 

Station (inches) (ft3/s) (ft3)

Nitrogen, Phosnitrite Phos- phorus,

Nitrogen, Nitrogen, and phorus, ortho- Suspended

Organic ammonia nitrate total phosphate sediment

(Ibs) (Ibs) (Ibs) (Ibs) (Ibs) (short tons)

03/26/95 

05/18/95 

06/06/95

Middle Beaver 

Baxter Bottom

Middle Beaver 

Baxter Bottom

Middle Beaver 

Baxter Bottom

 1.0 

0.7

*0.8 

0.8

*0.7 

1.0

659 

122

200 

10

53

47

10,000,000 

8,210,000

3,290,000 

445,000

1,350,000 

3,560,000

3,590 

3,690

2,260 

108

562 

302

362 

132

220 

20

88 

29

478 

159

1,240 

57

527 

236

950 

243

728 

31

88 

62

562 

141

231 

15

77

53

1,010 

55

475 

15

122

40

Nutrient and Sediment Loads in a Channelized Stream and 7 

a Nonchannellzed Wetland Stream
during the other two events (May 18,1995 and June 6, 

1995). Ammonia, nitrite and nitrate, and phosphorus 

loads ranged from 1.4 to 23 times greater at Middle 

Beaver Creek during the three events examined.

The quick hydrologic response and fast runoff at 

the Middle Beaver Creek may reduce the ability of this 

system to assimilate nutrients. The fast flowing water 

may allow for little settling of sediments and may 

enhance stream bed and bank erosion, contributing to 

additional sediment load. The longer retention time of 

water in the nonchannelized/wetland stream as compared to the channelized stream and the biogeochemical processes associated with wetlands in the nonchannelized stream may allow this system to function as a 

sink for nutrients and suspended sediments.

These findings further document the ability of 

natural streams and wetland areas to reduce waterquality degradation. These findings indicate that preserving the biological and hydrological functions of 

natural wetlands in agricultural areas may be an integral part of instream and watershed management practices used to reduce nonpoint-source pollution.

higher concentrations and loads of suspended sediment and nutrients, even when it received less rainfall 

and had less storm runoff than Baxter Bottom.

During the June 6,1995 storm event, the stormrunoff volume at Baxter Bottom was 2.6 times greater 

than at Middle Beaver Creek. Despite the greater discharge on June 6 at Baxter Bottom, the total loads for 

various constituents at Middle Beaver Creek still 

ranged from 1.4 to 3.1 times greater than loads at Baxter Bottom. Suspended-sediment loads ranged from 

3.1 to 32 times greater at the channelized stream (Middle Beaver Creek) than at the nonchannelized/wetland 

stream (Baxter Bottom). Ammonia, nitrite and nitrate, 

and phosphorus loads ranged from 1.4 to 32 times 

greater at the channelized stream than the nonchannelized stream.

The results indicate that natural streams and 

wetland areas may lessen water-quality degradation. 

Results also indicate that preserving wetlands in agricultural areas may be an integral part of instream 

resource-management practices available for use in 

reducing nonpoint-source pollution.

SUMMARY

Modifications of drainage networks by channelization has altered the hydrologic regime of many 

streams and wetland systems, potentially affecting the 

biological and nonbiological functions that are normally associated with these systems. In 1995, the U.S. 

Geological Survey completed a study comparing the 

drainage basins of two streams that are similar in size, 

land use, and topography. The primary difference 

between the two basins is the drainage networks; the 

upper Middle Beaver Creek Canal basin (7,600 acres) 

has been channelized, but the Baxter Bottom basin 

(8,000 acres) contains the only nonchannelized bottomland within the Beaver Creek watershed and flows 

through a 600-acre bottomland hardwood wetland. 

About 70 percent of the land in both basins is under 

cultivation.

Water samples were collected at 10- and 30- 

minute intervals during three storm events: one prior 

to the planting of row crops and two during the summer growing season (April to September). Peak discharges at Middle Beaver Creek were higher and 

occurred sooner than at Baxter Bottom during similar 

rainfall events. The data from the storms of March 26, 

May 18, and June 6, 1995, indicate that significant differences in concentrations and loads of nutrients and 

sediment are evident in the two streams. Because of 

the faster response of Middle Beaver Creek, the stormrunoff duration was normally much shorter than for 

Baxter Bottom. Middle Beaver Creek generally had

SELECTED REFERENCES

Ashley, G.H., 1910, Drainage problems in Tennessee: Tennessee State Geological Survey Bulletin, 3-A, p. 1-15.

Gilliam, J.W., 1994, Riparian wetlands and water quality: 

Journal of Environmental Quality, v. 23, p. 896-900.

Hook, D.D., 1993, Wetlands: History, current status, and 

future: Environmental Toxicology and Chemistry, 

v.l 2, p. 2157-2166.

Kennedy, E.G., 1983, Computation of continuous records of 

streamflow: U.S. Geological Survey Techniques of 

Water Resources Investigations, Book 3, chapter A13, 

53 p.

Lowrance, R, Vellidis, G., and Hubbard, R.K., 1995, Wetland and aquatic processes: Denitrification in a 

restored riparian forest wetland: Journal of Environmental Quality, v. 24, p. 808-815.

Petersen, L.B.M., and Petersen, R.C., 1991, Short term 

retention properties of channelized and natural 

streams: Internationale Vereinigugn fuer Theoretische und Angewandte Limnologie, v. 24, no. 3, 

p. 1756-1759.

Phillips, J.D., 1989, Fluvial sediment storage in wetlands: 

Water Resources Bulletin, v. 25, n. 4, p. 867-873.

Reddy, K.R., and Gale, P.M., 1994, Wetland processes and 

water quality: A symposium overview: Journal of 

Environmental Quality, v. 23, p. 875-877.

U.S. Department of Agriculture, Soil Conservation Service, 

1993, Soil survey of Tipton County, Tennessee: Washington, D.C., U.S. Government Printing Office, 102 p.

Instream Investigations in the Beaver Creek Watershed in 

West Tennessee, 1991-95
Evaluation of a Constructed Wetland to Control 

Agricultural Row-Crop Nonpoint-Source Pollution

By JOHN A. SMINK and TOM D. BYL 

U.S. GEOLOGICAL SURVEY

Prepared in cooperation with the

Shelby County Soil and Water Conservation District,

Tennessee Soybean Promotion Board, and the

U.S. Department of Agriculture,

Natural Resources Conservation Service

Evaluation of a Constructed Wetland to Control 

Agricultural Row-Crop Nonpoint-Source Pollution

By John A. Smink and Tom D. Byl

Abstract

As water flows through wetlands, water 

quality is modified because of physical, chemical, 

and biological processes. Humans have taken 

advantage of this attribute to treat wastewater, 

acid mine drainage, and industrial point-source 

discharge. Recently, constructed wetlands have 

been used to treat agricultural runoff from feedlots and animal facilities. A constructed wetland 

was evaluated to determine the feasibility of using 

wetlands to improve the quality of storm-water 

runoff from soybean fields in West Tennessee. 

The 1.5-year-old constructed wetland discussed in 

this study was effective in reducing nitrogen loads 

by 46 percent, phosphorous loads by 41 percent, 

suspended-sediment loads by 67 percent, metolachlor loads by 51 percent, and acifluorfen loads 

by 90 percent during the five storms sampled. 

These results demonstrate that constructed wetlands are capable of reducing row-crop runoff and 

improving water quality.

INTRODUCTION

Nonpoint-source (NFS) pollution has been identified as a major cause of surface-water impairment in 

the United States (U.S. Environmental Protection 

Agency, 1989). Created, restored, and natural wetlands can contribute significantly to improving water 

quality (Olson, 1993). Extensive research has been 

conducted using wetlands to treat wastewater from 

industrial, agricultural, and municipal sources (Kadlec 

and Kadlec, 1979). The results indicate wetlands can 

effectively remove heavy metals, nutrients, and total 

suspended solids from point sources (Suurballe, 

1991). Because wetlands have an intrinsic ability to

reduce pollution from point sources, they show great 

potential as a method for reducing nonpoint-source 

pollution. The Des Plaines River Wetlands Demonstration Project effectively reduced sediment, phosphorus, and atrazine loads from pumped river water in 

an agricultural and urban watershed (Kadlec and Bastiens, 1992). Wetlands also have been effective in 

reducing chemical oxygen demand and buffering acids 

from acid mine drainage, as well as in sequestering 

metals from metal mine drainage (Eger, 1994). 

Because of these successes, the use of constructed 

wetlands has gained popularity for controlling 

nonpoint-source pollution from urban areas, silviculture activities, construction, and mining activities.

Recently, wetlands have been constructed to 

improve the quality of water in agricultural runoff 

from feedlots and animal-production facilities (MacDonald, 1994). These constructed wetlands are low 

maintenance processors which reduce animal-waste 

pollution by chemical, physical, and biological reactions. In spite of the successful use of constructed wetlands for these purposes, little research has been 

directed toward using constructed wetlands to control 

agricultural NFS pollution from row crops. Wetlands 

have the potential to improve water quality by assimilating nutrients and pesticides, thereby reducing the 

load carried into the streams by storm runoff. Wetlands act as sediment traps and reduce sediment transport into larger bodies of water. Wetlands have been 

shown to reduce the erosive powers of floods by moderating peak discharges and releasing storm water 

slowly (Novitzki, 1979). Wetlands provide these benefits at low cost.

Efforts have been made by the agricultural 

community to reduce agricultural NFS pollution by 

implementing best management practices (BMP's). 

However, these efforts have not always had the 

desired effect. This lack of success may be due to

Evaluation of a Constructed Wetland to Control Agricultural 

Row-Crop Nonpoint-Source Pollution

11
overwhelming weather conditions or the selection 

of an inappropriate BMP for the Beaver Creek 

region. Therefore, modified and new BMP's have 

been encouraged and evaluated in the Beaver Creek 

Hydrologic Unit Area to optimize their effectiveness. Constructed wetlands are one type of BMP 

that has potential to control or reduce NPS pollution 

in the agricultural rich Mississippi embayment.

This report discusses the results of a project that 

evaluated the effectiveness of a constructed wetland to 

improve water quality from agricultural row-crop runoff. The experimental design was an upstreamdownstream approach. Runoff was sampled as the 

water entered and exited the wetland. An intensive 

sampling program was designed to collect water samples through the entire runoff period of individual 

storms. The samples were analyzed for suspended sediment and selected pesticides and nutrients. The 

results of these activities were used to evaluate the 

ability of a constructed wetland to reduce NPS pollution from storm runoff. This project was conducted 

from March to August 1995 by the U.S. Geological 

Survey, in cooperation with Shelby County Soil and 

Water Conservation District, Tennessee Soybean Promotion Board, and the U.S. Department of Agriculture, Natural Resources Conservation Service.

ACKNOWLEGDMENTS

Thanks to John Charles Wilson for allowing the 

authors to conduct these studies on his property.

DATA COLLECTION

In fall 1993, a constructed wetland cell, planted 

with cattails and bulrushes, was built in the Beaver 

Creek watershed in West Tennessee (fig. 1), which is 

in the Mississippi embayment. The constructed wetland cell is rectangular in shape and is approximately 

0.88 acre. Maximum storage capacity of the cell is 

about 76,700 cubic feet, and it can hold as much as 

2 feet of water before outflow begins to discharge 

through an outlet flume. The wetland receives runoff 

from two row-crop fields. These fields are relatively 

flat, and the elevated rows have been oriented to move 

stormwater into a drainage ditch and subsequently into 

the wetland cell. The drainage ditch enters the constructed wetland at the north end; water spreads out 

and flows the length of the wetland cell and exits the 

south end into a larger ditch.

Both fields that drain into the constructed wetland were planted exclusively in soybeans in 1995 

using conventional planting methods. The size of the 

field farthest from the constructed wetland is 20 acres 

and that of the closer field is 27 acres. The soil in the 

smaller field is a combination of Waverly and Falaya 

loess silty loam, and the larger field is predominately 

Waverly loess silty loam. Both fields have less than a 

5-percent grade. The fields are classified as "bottom 

land" by the Shelby County Soil and Water Conservation District and are part of the West Beaver Creek 

flood plain.

U.S. Geological Survey (USGS) gaging stations 

were constructed at the inlet and the outlet of the wetland cell. Each station was equipped with stage 

recording instruments and two automatic samplers. 

One automatic sampler at each station collected water 

samples for nutrient and pesticide analyses, and the 

second sampler collected samples for suspendedsediment analyses. A tipping-bucket rain gage 

recorded rainfall at the wetland cell. Liquid-level actuators were used to automatically initiate the sampling 

program at the beginning of a runoff event. Samples 

used for nutrient and herbicide (metolachlor and acifluorfen) analyses were immediately placed on ice and 

shipped to contract analytical laboratories. Total suspended-sediment samples were labeled and analyzed 

within a few weeks after collection.

The samples used for nutrient and herbicide 

analyses were kept on ice, labeled, and shipped for 

rapid delivery to the analytical laboratories. Samples 

for suspended-sediment analyses were analyzed by the 

USGS Sediment Laboratory in Tuscaloosa, Alabama. 

Samples for nutrient and metolachlor analyses were 

analyzed by the USGS Laboratory in Ocala, Florida. 

Acifluorfen analyses were performed by a contract 

laboratory (Quanterra) in Arvada, Colorado.

Metolachlor and acifluorfen were the two herbicides selected for analyses because they were 

applied to both fields. Metolachlor is a pre-emergent 

herbicide, which is applied just prior to planting or in 

conjunction with planting. Acifluorfen is a postemergent herbicide, which is applied several weeks 

after plant germination. Metolachlor was applied to 

the smaller field on June 17, 1995. Acifluorfen was 

applied to the larger field on June 17, 1995. Stormrunoff samples were collected on March 27 prior to 

planting or herbicide application to establish preplanting concentrations of nutrients, suspended 

sediments, and herbicides. Intensive storm runoff

12 Instream Investigations in the Beaver Creek Watershed in 

West Tennessee, 1991 -95
TENNESSEE

eaver Creek watershed

STUDY AREA

Constructed 

wetland cell 

Storm sampling site (not to scale)

Herbacious ripar/an Woody riparian 

stream reach

Figure 1. Location of the constructed wetland in the Beaver Creek watershed, West Tennessee.

Evaluation of a Constructed Wetland to Control Agricultural 13 

Row-Crop Nonpoint-Source Pollution
sampling was re-initiated after the fields were simultaneously tilled, planted, and sprayed in early June. 

The storm sampling continued through August. Four 

storm runoff events occurred from June to midAugust 1995. Water samples for nutrient, suspended 

sediment, and metolachlor analyses were collected 

during each of the four runoff events. The only water 

samples for acifluorfen analyses were collected during the initial screening and the fourth storm because 

this herbicide was not applied until after the third 

storm.

The number of samples per storm was dictated 

by the length of the storm and runoff hydrograph. Not 

having advance knowledge of intensity, size, or length 

of any storm, runoff samples were collected at 10- to 

15-minute intervals for the duration of each storm 

event. After all samples were collected and returned to 

the processing lab, a subset of samples was selected to 

represent the storm-runoff event. More samples were 

analyzed corresponding to the beginning of storm 

events because the stage rose fairly quickly compared 

to the relatively slow descent at the end of the storm. 

This sampling strategy was designed to provide 

greater sensitivity during the first flush of the event.

Discharge was calculated with stage-discharge 

rating curves developed by using methods described 

by Kennedy (1983). Loads (L) were calculated by 

using the sum of individual interval loads:

L = (i)

where

GI is the ith interval of sampled concentration,

<?i is the instantaneous discharge at the time the 

sample was collected,

ti is the time interval associated with the sample,

K is a unit conversion factor, and

n is the number of samples.

This method assumes that the sampled concentration 

and the corresponding discharge value are representative of the time interval t ,-, that is equal to half the time 

from the preceding sample to the current sample plus 

half the time from the current sample to the following 

sample.

EVALUATION OF CONSTRUCTED 

WETLAND

A range of storm intensities and runoff conditions occurred during the test period (table 1). Observations were made that runoff in the inflow ditch was 

of short duration, stopping soon after the rain ceased. 

The wetland had no outflow during the July 20 storm 

because the water surface in it did not rise to the level 

of the discharge flume. The first and last storms had 

relatively equal volumes of water flowing in and out. 

The storm of March 27,1995, had a total inflow volume of 38,600 cubic feet (ft3) and a total outflow volume of 38,500 ft3 . The storm of August 4,1995, had 

inflow of 313,000 ft3 and outflow of 313,000 ft3.

The effectiveness of the constructed wetland 

was measured by its ability to reduce total loads and 

peak concentrations (data not shown) of nutrients, 

suspended sediment, and herbicides. The analysis was 

made by comparing water quality at the inlet and outlet of the constructed wetland. Average concentrations 

for nutrients ranged from 0.3 to 6.6 milligrams per 

liter (mg/L) for inflow, and from 0.2 to 5.7 mg/L for 

outflow; suspended sediment ranged from 97 to 

456 mg/L for inflow and from 22 to 79 mg/L for outflow; herbicides ranged from 0.25 to 16.0 micrograms 

per liter (jig/L) for inflow and from 0.11 to 1.67 jig/L 

for outflow. In general, average concentrations of 

nutrients, suspended sediment, and herbicides were 

higher at the inlet station than at the outlet station 

(table 2).

Total loads for nutrients, suspended sediment, 

and herbicides generally were higher at the inlet sample station compared to the downstream outlet sample 

station (table 3). Average loads for nutrients ranged 

from 0.4 to 102.3 pounds for inflow and from 0.4 to 

43.2 pounds for outflow; suspended-sediment loads 

ranged from 765 to 1,877 pounds for inflow and from 

115 to 1,012 pounds for outflow; herbicide loads 

ranged from 0.01 to 5.0 ounces for inflow and from 

less than 0.01 to 0.52 ounces for outflow. For the July 22 

storm, however, nitrogen load was slightly higher for 

outflow (13.2 pounds) than for inflow (13.0 pounds). 

This result was probably because the storm event 

2 days earlier brought in nutrients and sediment, but 

the wetland did not discharge any water on that date. 

Inflow from the storm on July 22 was sufficient to 

raise the water level and push some of the enriched 

water out by displacement.

The five-storm load for total nitrogen was 

140 pounds at the inlet and 76 pounds at the outlet (table 3). These total loads were used to calculate the reduction in NFS contaminants as 

percentages (table 4). The wetland cell reduced 

the total-nitrogen export by approximately

14 Instream Investigations in the Beaver Creek Watershed in 

West Tennessee, 1991-95
46 percent during the study period. The fivestorm load for total phosphorous was 16.7 pounds 

at the inlet and 9.8 pounds at the outlet; a reduction of 41 percent. The five-storm suspendedsediment load was reduced from 5,812 pounds at 

the inlet to 1,942 pounds at the outlet, a reduction 

of 67 percent. Metolachlor loads were reduced 

from 0.41 ounces at the inlet to 0.20 ounces at the 

outlet. Thus, the wetland cell reduced 51 percent 

of the metolachlor load during the study period. 

The final storm was the only one with measurable 

concentrations of acifluorfen in runoff. This herbicide was reduced by 90 percent at the outflow.

SUMMARY AND DISCUSSION

Nonpoint-source pollution has been identified as 

a major source of surface-water impairment in the 

United States. The purpose of this study was to evaluate the effectiveness of a wetland constructed in fall 

1993 in improving water quality. Two bottom land 

fields (20 and 27 acres) that drain into the constructed 

wetland were planted exclusively in soybean using 

conventional planting methods. The constructed wetland intercepts runoff water from these fields before 

the water enters the Beaver Creek drainage network.

Gaging stations were constructed at the inlet and 

the outlet of the wetland cell. Each station was 

equipped with a stage recording instrument and two 

automatic samplers. Storm runoff was sampled as it 

entered and exited the wetland to determine the effect 

of the wetland on reducing row-crop runoff and on 

improving the quality of water from runoff.

Storm-runoff samples were collected on 

March 27,1995, prior to planting or herbicide application to establish pre-planting concentrations of nitrogen, phosphorus, suspended sediment, metolachlor, 

and acifluorfen. Metolachlor, a pre-emergent herbicide, was applied to the 20-acre field on June 17,1995; 

and acifluorfen, a post-emergent herbicide, was 

applied to the 27-acre field also on June 17. Storm runoff from four storms was sampled from mid-June 

through August.

The wetland had no outflow during the July 

20 storm, but the first and last storms each had 

about the same amount of inflow (38,600 and 

313,000 ft3) as they did outflow (38,500 and 

313,000 ft3). In general, average concentrations of 

nutrients, suspended sediment, and herbicides 

were higher at the inlet station than at the outlet

Table 1 . Storm duration, rainfall, runoff depth, total volume of runoff into and out of the wetland cell

[-- = no data; in. = inches; ft3 = cubic feet]

Storm

date

03/27/95

07/05/95

07/20/95

07/22/95

08/04/95

Duration of

stormflow

_

42 hours

22 hours

66 hours

71 hours

Rainfall

(in.)

0.5

2.0

1.1

3.2

4.1

Runoff

depth (in.)

0.22

0.51

0.02

1.29

1.83

Total volume

Inflow (ft3)

38,600

87,500

2,700

220,200

313,000

Outflow (ft3)

38,500

76,100

0

208,400

313,000

Table 2. Average concentration of total nitrogen, phosphorous, suspended sediment, metolachlor, and acifluorfen for five storm 

events at the wetland cell

[mg/L = milligrams per liter; Ug/L = micrograms per liter; = no data, prior to application; # = no discharge]

Storm 

date

Nitrogen, 

total 

(mg/L)

Inflow Outflow

03/27/95

07/05/95

07/20/95

07/22/95

08/04/95

6.6

1.6

2.5

1.0

5.2

5.7

1.3

#

1.0

2.2

Phosphorous, 

total 

(mg/L)

inflow

0.6

0.7

1.4

0.3

0.3

OUtflOW

0.2

0.4

#

0.3

0.2

Suspended 

sediment 

(mg/L)

Inflow

329

171

456

104

97

outflow

47

79

#

78

22

Metolachlor Acifluorfen 

fag/L) (ng/L)

inflow

0.25

1.83

0.50

0.46

-

Outflow inflow

0.11

1.31

#

0.44

16.0

outflow

-

1.67

Evaluation of a Constructed Wetland to Control Agricultural 

Row-Crop Nonpoint-Source Pollution

15
Table 3. Total storm loads of nitrogen, phosphorous, suspended sediment, metolachlor, and acifluorfen in the wetland 

inflow and outflow

[# = no discharge; = no data; < = less than]

Storm 

date

03/27/95

07/05/95

07/20/95

07/22/95

08/04/95

Total

Nitrogen, 

total

(pounds)

Inflow Outflow

15.9 13.9

8.6 5.9

0.4 #

13.0 13.2

102.3 43.2

140.2 76.2

Phosphorous, 

total

(pounds)

Inflow Outflow

1.5 0.4

3.5 2.2

2.4 #

4.2 3.7

5.1 3.5

16.7 9.8

Suspended 

sediment

(pounds)

Inflow Outflow

796 115

942 384

765 #

1,422 1,012

1,887 432

5,812 1,942

Metolachlor

(ounces)

Inflow Outflow

0.01 <0.01

0.16 0.10

0.14 #

0.10 0.09

._

0.41 0.20

Acifluorfen

(ounces)

Inflow Outflow

..

_.

__

__

5.0 0.52

5.0 0.52

Table 4. Percentage reduction in storm loads of nitrogen, phosphorous, metolachlor, and acifluorfen at wetland outflow for 

five storm events

[Storm 7/20/95 was combined with 7/22/95 to calculate the percentage of reduction because there was no discharge during 7/20/95; e = estimated; = no data]

Storm 

date

03/27/95

07/05/95

07/20+22/95

08/04/95

Total

Nitrogen 

total

(percent)

13

31

2

58

46

Phosphorous 

total

(percent)

73

37

44

31

41

Suspended 

sediment

(percent)

86

59

54

77

67

Metolachlor

(percent)

60 e

36 e

62

~

51

Acifluorfen

(percent)

_

90

90

station. Average concentrations of herbicides 

ranged from 0.25 to 16.0 (ig/L for inflow and 

0.11 to 1.67 iig/L for outflow. Total loads for nutrients, suspended sediment, and herbicides generally 

were higher at the upstream inlet station than at the 

downstream outlet station. For the July 22 storm, 

however, the nitrogen load was slightly higher for 

outflow (13.2 pounds) than for inflow (13.0 pounds). 

This increase in nitrogen was probably due to the 

input from the July 20 storm. Combining these two 

storms, nitrogen was decreased at the outlet by 

2 percent. The five-storm load for total nitrogen 

was reduced by 46 percent. Total phosphorous 

load was reduced by 41 percent. Total suspendedsediment load was reduced by 67 percent. Metolachlor loads were reduced by 51 percent. The 

final storm was the only one with measurable concentrations of acifluorfen in runoff. This herbicide 

was reduced by 90 percent at the outflow. These 

data demonstrate the ability of the constructed 

wetland to reduce NFS pollution and to help preserve the aquatic ecosystem.

Constructed wetlands can be built at low cost, 

require low-maintenance management, and have the 

potential to become an effective part of agricultural 

BMP programs. Further study would determine if 

plant community maturation or design modifications 

could improve the effectiveness of the constructed 

wetland to reduce NFS pollution.

REFERENCES CITED

Eger, P., 1994, Wetland treatment for trace metals removal 

from mine drainage: The importance of aerobic and 

anaerobic processes: Water Science Technology, no 29, 

p. 249-256.

Kadlec, R.H., and Bastiens, W.V., 1992, The use of residence time distributions (RTDs) in wetland systems; 

The Des Plaines River Wetlands Demonstration 

Project: Chicago, 111., Wetlands Research, Inc., 101 p.

Kadlec, R.H., and Kadlec, J.A., 1979, Wetlands and water 

quality, in Greeson, P.E., Clark, J.R., and Clark. J.E., 

eds., Wetland functions and values: The state of our 

understanding: American Water Resources Association, TSP79-2, Minneapolis, Minn., p. 436-456.

16 Instream Investigations in the Beaver Creek Watershed in 

West Tennessee, 1991-95
Kennedy, E.G., 1983, Computation of continuous records of 

streamflow: U.S. Geological Survey Techniques of 

Water Resources Investigations, Book 3, chapter A13, 

53 p.

MacDonald, L., 1994, Pollution solution: Build a marsh: 

American Forests, July, p. 26-29.

Novitzki, R.P., 1979, Hydrologic characteristics of Wisconsin's wetlands and their influence on floods, stream 

flow and sediment, in Greeson, P.E., Clark, J.R., and 

Clark, I.E., eds., Wetland functions and values: The 

state of our understanding: American Water Resources 

Association, TSP 79-2, Minneapolis, Minn., 

p. 377-388.

Olson, R.K., 1993, Evaluating the role of created and natural wetlands in controlling nonpoint source pollution,

Created and natural wetlands for controlling nonpoint 

source pollution: U.S. Environmental Protection 

Agency Office of Research and Development and 

Office of Wetlands, Oceans, and Watersheds: Smoley, 

Conn., CRC Press, Inc., 69 p.

Suurballe, N., 1991, Effects of a wetland on quality of Natty 

Pond Brook, Massachusetts, 1985-86: U.S. Geological 

Survey Water-Resources Investigations Report 

91-4144, 52 p.

U.S. Environmental Protection Agency, 1989, Focus on 

nonpoint source pollution: The Information Broker, 

U.S. Environmental Protection Agency, Washington, 

D.C. Office of Water Regulations and Standards, Nonpoint Sources Control Branch, 168 p.

Evaluation of a Constructed Wetland to Control Agricultural 17 

Row-Crop Nonpoint-Source Pollution

Influence of Riparian Vegetation on the Biological 

Structure and Processing Function of a Channelized 

Stream in West Tennessee

By TOM D. BYL, YUN JIAO, and SUSAN S. HUTSON_____ 

U.S. GEOLOGICAL SURVEY

Prepared in cooperation with the

U.S. Department of Agriculture,

Natural Resources Conservation Service,

Shelby County Soil and Water Conservation District, and the 

University of Memphis Geography Department

Influence of Riparian Vegetation on the Biological 

Structure and Processing Function of a Channelized 

Stream in West Tennessee

By Tom D. Byl, Yun Jiao*, and Susan S. Hutson 

Abstract

The influence of riparian vegetation on the 

biological structure and processing function of a 

first-order stream was investigated. This study 

was conducted by the U.S. Geological Survey, in 

cooperation with the U.S. Department of Agriculture, Natural Resources Conservation Service; 

Shelby County Soil and Water Conservation District; and the University of Memphis Geography 

Department to compare the biologic structure and 

processing of a herbaceous and a woody reach of 

stream in the Beaver Creek watershed, West Tennessee. The study stream is located in an agricultural basin planted in row crops and had been 

channelized for drainage. Herbaceous plants lined 

the upper reach of the stream, and mature woody 

vegetation lined the lower reach. Biological and 

chemical monitoring was done during the 1995 

growing season (May-September); the rate of leaf 

decomposition was measured using leaf packs. 

Also, qualitative visual observations were made 

concerning habitat stability. The biological structure and processing function of the herbaceous 

and woody reaches were compared. The herbaceous reach had a greater diversity and abundance 

of organisms during spring and early summer than 

the mature woody reaches. However, the abundance dropped approximately 85 percent during 

late summer. The woody reach was more stable 

with regard to pH (6.7, ± 0.3 compared to 6.6 ± 

1.0), dissolved oxygen (5.3 milligrams per liter ±

* Graduate Student, Univ. Memphis, Dept. of Geography, Memphis, TN 38152

3.2 compared to 6.5 milligrams per liter ± 7.3), 

and specific conductance (472 microsiemens per 

centimeter, ±438 compared to 302 microsiemens 

per liter ±712). The biological community structure was also more constant in the woody reach. 

The leaves in the leaf packs decomposed approximately 45 percent faster in the herbaceous reach 

than in the woody reach. The enhanced decomposition could be an effect of the elevated temperatures in the herbaceous reach. The processing 

function of both reaches was within the ranges 

reported in the literature.

INTRODUCTION

Regulatory biomonitoring used to assess stream 

water quality focuses primarily on structural attributes 

of the stream biota (Plafkin and others, 1989; Klemm 

and others, 1990). Examples of structural attributes are 

abundance and diversity of organisms that live in the 

stream (Cairns and others, 1992). Studies have shown 

that the structure of the biological community in the 

stream reflects the quality of the aquatic environment 

(Rosenberg and Resh, 1992). The amount of interpretation that can be made from a structural analysis, 

however, is limited (Byl and Smith, 1994).

More recent monitoring initiatives have called 

for assessing functional attributes of the stream as well 

(Cairns and others, 1992; Cairns and McCormick, 

1992). One functional attribute of a healthy stream is 

the ability to process organic material temporally and 

spatially (for example, leaf decomposition and nutrient cycling). This processing function must occur in a 

successional manner over the length of a watershed to 

maintain the health of the aquatic ecosystem (Petersen 

and Petersen, 1991). For example, plant leaf material 

needs to be broken down into smaller fragments as it

Influence of Riparian Vegetation on a Channelized Stream 21
moves progressively from low-order to high-order 

streams. This allows the successive biological communities to take advantage of the food source (Cummins, 1973). Modifying the stream may interrupt the 

processing continuum and, ultimately, the biological 

continuum. Thus, stream function needs to be understood and incorporated when attempting to enhance 

water quality.

Assessment of processing functions, in addition 

to structural evaluations, is advantageous because 

(1) it is closely associated with structure; (2) functional attributes provide insight into the results of 

structure analysis; and (3) a stream may have good 

structural attributes, but may lack adequate functional 

attributes that could generate problems downstream. 

The disadvantage of assessing the function of a stream 

is the lack of standardized and quantifiable endpoints.

This study was conducted by the U.S. Geological Survey, in cooperation with the U.S. Department of 

Agriculture-Natural Resources Conservation Service, 

Shelby County Soil and Water Conservation District, 

and the University of Memphis Geography Department. The purpose of this study was to evaluate the 

biological structure and processing function of a small 

channelized, agricultural stream and to determine if 

riparian vegetation had any influence on those parameters.

SELECTING THE SAMPLE SITES

The stream used in this study is a channelized 

first-order stream in the Beaver Creek watershed in 

West Tennessee (fig. 1). The stream is approximately 

2.5 miles long. The herbaceous and woody reaches 

used in this study were each approximately 0.6 mile 

long. During baseflow, the stream is a series of pools 

and small riffles ranging in depth from 3.28 feet to 

0.2 inch, respectively. During high stormflow, the 

stream becomes a fast flowing channel with depths up 

to 10 feet. The stream drains an agricultural basin 

(approximately 500 acres) used to raise row crops. 

The most common crops were cotton, soybeans, winter wheat, and corn. Some acreage also was used for 

forestry and grass filter strips. Five pool sites were 

selected to be sampled and monitored in each of the 

herbaceous and the woody vegetated reaches. An 11th 

site was selected in the transition zone between the 

herbaceous and woody reaches. Pools were chosen for 

the study because the riffles were vulnerable to 

drought and physical alterations during stormflow 

(Byl and Roman, 1994). The streambanks of the herbaceous and woody reaches were visually examined 

for active erosion during the study because erosion 

indicates streambank and habitat instability.

MEASURING THE BIOLOGICAL 

STRUCTURE AND PROCESSING 

FUNCTION

Leaf packs and benthic grab samples were collected three times over the study period to characterize 

the biological structure of the stream. Benthic macroinvertebrates (organisms retained by a 600-micrometer 

mesh sieve) were collected, identified to family, and 

counted as a measure of biological structure. Rate of 

leaf decomposition in the leaf pack was used as a simple measure of processing function. This technique 

has been used in previous studies (Elder and Cairns, 

1982; Byl and Roman, 1994). Water chemistry was 

also monitored to gain more insight into the processing attributes of the two stream reaches.

An initial reconnaissance was done during site 

selection to assure that organisms inhabited each site. 

Leaf packs consisted of 20.0 grams of oven dried, 

whole red oak leaves placed in nylon mesh bags (mesh 

size = 0.25 inch). Three bags were placed at each site 

for a total of 15 bags per vegetative reach. The packs 

were secured at the sites witn wooden stakes. Five leaf 

packs from each reach were retrieved 36, 66, and 116 

days after they were placed in the stream. Benthic grab 

samples also were collected at this time following U.S. 

Environmental Protection Agency procedures (Klemm 

and others, 1990).

The leaf material was placed in a dish tub and 

rinsed with water to remove sediment and macroinvertebrates. The macroinvertebrates were collected and 

preserved with 70 percent isopropyl alcohol for identification and counting. The rinsed leaves were dried in 

a drying oven and weighed to determine loss of dry 

weight from the initial weight.

The pH, dissolved oxygen, temperature, turbidity, and specific conductance were measured with a 

Hydrolab DataSonde-3. Alkalinity was measured 

using the acid titration method. Each of these constituents was measured at the 11 sites weekly for 11 consecutive weeks. Additionally, daily measurements 

were made after a rain event to determine how the two 

systems responded after being flushed. A statistical 

comparison of the herbaceous and woody riparian 

reaches was done using the Mann-Whitney rank test.

22 Instream Investigations in the Beaver Creek Watershed in 

West Tennessee, 1991-95
TENNESSEE

Figure 1. Location of the study area in the Beaver Creek watershed, West Tennessee.

Influence of Riparian Vegetation on a Channelized Stream 23
THE INFLUENCE OF RIPARIAN 

VEGETATION ON STREAMBANKS

The streambanks in the herbaceous reach are 

generally more shallow and broader than those in the 

woody reach. Where the banks were steep along the 

herbaceous reach, active erosion and mass wasting 

was evident. The woody reach had isolated areas 

where some bank undercutting below the tree roots 

had occurred. The banks in the woody reach appeared 

generally more stable than those in the herbaceous 

reach. However, more down cutting was observed in 

the woody reach than the herbaceous reach. These 

observations tend to support the research findings of 

Shields, Bowie, and Cooper (1995) and Shields, 

Knight, and Cooper (1995a,b) that trees help to stabilize streambanks. However, trees do not necessarily 

stabilize the stream bottom.

THE INFLUENCE OF RIPARIAN 

VEGETATION ON BIOLOGICAL 

STRUCTURE AND PROCESSING 

FUNCTION

Biological samples were collected using sediment grab samples and leaf packs (table 1). The total 

number of macroinvertebrates was greater in the herbaceous reach than in the woody reach during June 

and July; however, the population declined 85 percent 

in the herbaceous reach when sampled in September. 

The macroinvertebrate abundance and diversity were 

more constant in the wooded reach. This consistency 

was probably due to the more stable chemical, hydrologic, and physical environment associated with the 

woody riparian vegetation.

A reduction in leaf weight was noted in the herbaceous and the woody reaches from May to September. A 60-percent reduction in weight of the leaf 

material was recorded from the herbaceous reach, and 

a 35-percent reduction in leaf weight was recorded in 

the woody reach (table 1). Thus, the rate of leaf 

decomposition was approximately 45 percent greater 

in the herbaceous reach compared to the woody reach. 

This enhanced rate could be due to higher temperatures stimulating faster rates of catabolism as well as a 

greater number of macroinvertebrates in the herbaceous reach. Both reaches, however, had equal or 

higher rates of leaf decomposition as compared to a 

previous study in the same stream (Byl and Roman, 

1994) and similar studies in the southeastern United 

States (Elder and Cairns, 1982; Byl and Roman, 1994; 

Kittle and others, 1995). Thus the rate of decomposition, which is a measure of stream function, was equal

Table 1 . Biomonitoring results in the herbaceous and woody reaches

[Leaf pack counts and weight are reported per average leafpack; <, less than; *n = 1 for the September herbaceous leaf pack sampling, 

n = 3 at other sites and times]

Number of 

families

Organisms

per benthic

grab

Organisms 

per leaf pack

Leaf pack dry

weight loss

(grams)

Density, number of

organisms per gram of

dry leaf

June

Herbaceous 

Woody

10

9

482

310

687

147

6.9 

4.5

17

3

July

Herbaceous 

Woody

108

197

1,038

354

8.4 

7.1

15

4

September

Herbaceous

Woody

11

4

3

67

21*

279

11.7

6.9

<1

4

24 Instream Investigations in the Beaver Creek Watershed in 

West Tennessee, 1991-95
to or greater than rates in comparable streams in the 

southeastern United States.

Temperature, dissolved oxygen, pH, alkalinity, 

specific conductance, and turbidity were measured 

weekly (table 2). The herbaceous reach had greater 

variability and range in each of these chemical measurements than the woody reach, except for alkalinity 

(15-268 milliequi velents per liter) and turbidity [203- 

401 nephelometric units (NTU)]. Despite its wider 

range of turbidity (113-389 NTU), the woody reach's 

median turbidity value (251 NTU) was less than the 

herbaceous reach's (291 NTU). Thus, the wooded 

reach had less turbid waters on average than the herbaceous reach. The weekly water temperature in the herbaceous reach was significantly higher than the 

temperature in the woody reach. This elevated temperature was probably due to the lack of shade in the herbaceous reach. The median water temperature for the 

herbaceous reach was 25 °C, and for the wooded 

reach, 22 °C. This temperature increase is enough to 

enhance the metabolic rate of bacteria, algae, and 

other organisms (Stevens and others, 1975). This 

enhanced metabolic rate would explain why the values 

were higher for pH and dissolved oxygen, which are 

affected by respiration and photosynthesis.

SUMMARY AND DISCUSSION

Regulatory biomonitoring used to assess stream 

water quality focuses primarily on structural attributes 

of the stream biota; more recent monitoring initiatives 

have called for assessing functional attributes of the

stream as well. A study was done to compare the biological structure and processing function of a herbaceous and a woody reach of a first-order stream in the 

Beaver Creek watershed in West Tennessee. The 

stream drains a 500-acre agricultural basin planted in 

row crops. Eleven sites were evaluated for streambank 

stability, biological community, rate of leaf decomposition, and water chemistry.

Streambank stability is important to aquatic 

organisms for habitat stability. Visual observations 

were made of streambank stability during weekly sampling visits. The herbaceous reach had more streambank erosion than the wooded reach. However, 

downcutting of the streambed was a problem in the 

woody reach. Thus, the trees appear to be protecting 

the streambank, but not the stream bottom. Quantitative assessment could help to verify these qualitative 

observations.

Biological structure was evaluated in the herbaceous and woody reaches by sampling leaf packs and 

benthic grab samples from the stream. Leaf packs 

20.0 grams of oven dried, whole red oak leaves in 

nylon mesh bags and benthic grab samples were collected at 36,66, and 116 days after the leaf packs were 

placed in the stream to evaluate the abundance of 

organisms over time. The woody reach had less abundance of macroinvertebrates than the herbaceous 

reach, but a more stable population over the duration 

of the study. The biological stability in the woody 

reach was possibly due to chemical and physical stability an important feature for sustaining a healthy 

biological community provided by the woody riparian vegetation.

Table 2. Range of values and medians for physical and chemical properties

[uS/cm, microsiemens per centimeter; mg/L, milligrams per liter; meq/L, milliequi velents per liter; NTU, nephelometric units]

Stream

Herbaceous

Woody

Temperature

19.7 - 30.7

12.7-26.5

Dissolved 

oxygen (mg/L)

3.9-13.8

2.1 - 8.5

Alkalinity 

(meq/L)

Range

6.2 - 7.6

6.4 - 7.0

pH

15 - 268

22 - 282

Specific 

conductance 

(uS/cm)

89-1,013

158- 910

Turbidity 

(NTU)

203 - 401

113-389

Median

Herbaceous 

Woody

24.7 

21.5

6.5 

5.3

6.6

6.7

100

124

302 

472

291 

251

Influence of Riparian Vegetation on a Channelized Stream 25
Leaf weight loss was measured as an indicator 

of a stream processing function. The leaf weight from 

the herbaceous reach decreased by 60 percent; and in 

the woody reach, by 35 percent. The leaves decreased 

in dry weight by an average of 48 percent over a 3-month 

period. This rate of weight loss from the packaged 

leaves was comparable to similar studies in the southeastern United States. This weight loss demonstrates 

that the stream-processing functions operated acceptably when the material was retained by the mesh bags. 

Natural leaf-retention time in a stream is an important 

issue when considering stream function (Petersen and 

Petersen, 1991). This issue was not in the scope of this 

study, but could be a subject for future studies.

The herbaceous reach has more variability in 

water chemistry, possibly due to more intense solar 

radiation. The herbaceous reach had a greater variability and range in each of the measurements than the 

woody reach, except for alkalinity (15-268 milliequivelents per liter) and turbidity (203-401 NTU). Despite 

its wider range of turbidity (113-389 NTU), the woody 

reach's median turbidity value (251 NTU) was less 

than that of the herbaceous reach (291 NTU).

Well-functioning first-order streams help to 

maintain more vigorous aquatic ecosystems downstream. Evaluating the processing function of a 

stream, in addition to the biological structure, provides 

a better understanding of the stream's health. This 

study demonstrates that riparian vegetation had an 

influence on the stability of the streambank. Likewise, 

riparian vegetation influenced the biological community structure and the processing functions of this 

stream. In general, the woody reach was more stable 

with regard to habitat stability, biologic community 

structure, and water chemistry.

REFERENCES CITED

Byl, T.D., and Roman, A.J., 1994, Evaluation of biomonitoring techniques used in assessing agricultural nonpoint source pollution, in Pederson, G.L., ed., 

Symposium on Water Quality, Chicago, 1994, Proceedings: American Water Resource Association, 

Herndon,VA,p21-30.

Byl, T.D., and Smith, G.E, 1994, Biomonitoring our

streams - what's it all about?: U.S. Geological Survey 

Open-File Report 94-378, p. 2.

Cairns, J., Jr., and McCormick, P.V., 1992, Developing an 

ecosystem-based capability for ecological risk assessments: The Environmental Professional, 14, 

p. 186-196.

Cairns, J., Jr., Niederlehner, B.R. and Smith, E.P., 1992, The 

emergence of functional attributes as endpoints in 

ecotoxicology, in Burton, G.A., Jr., ed., Sediment Toxicity Assessment, Chelsea, Mich., Lewis Publishers, 

Inc.

Cummins, K.W., 1973, Trophic relations of aquatic insects, 

Annual Review of Entomology, v. 18, p. 183-206.

Elder, J.F., and Cairns, D.J., 1982, Production and decomposition of forest litter fall on the Apalachicola River 

flood plain, Florida: U.S. Geological Survey WaterSupply Paper 2196-B, p. B1-42.

Kittle, D.L., McGraw, J.B., and Garbutt, K., 1995, Plant litter decomposition in wetlands receiving acid mine 

drainage: Journal of Environmental Quality, v. 24, 

p. 301-306.

Klemm, D.J., Lewis, P.A., Fulk, F., and Lazorchak, J.M., 

1990, Macroinvertebrate field and laboratory methods 

for evaluating the biological integrity of surface 

waters: U.S. Environmental Protection Agency EPA/ 

600/4-90/030, Cincinnati, Ohio, 205 p.

Petersen, L.B.M., and Petersen, R.C., Jr., 1991, Short-term 

retention properties of channelized and natural 

streams: Verh. Internationale Vereinigugn fuer Theoratische and angewandte Liminologie, v. 24, no. 3, 

p. 867-873.

Plafkin, J.L., Barbour, M.T., Porter, K.D., Gross, S.K., 

Hughes, R.M., 1989, Rapid Bioassessment protocols 

for use in streams and rivers: Benthic macroinvertebrates and fish: U.S. Environmental Protection 

Agency, EPA/444/4-89/001, Cincinnati, Ohio, 165 p.

Rosenberg, D.M., and Resh, V.H., 1992, Introduction to 

freshwater biomonitoring and benthic macroinvertebrates, in Rosenberg, D.M., and Resh, V.H., eds., 

Freshwater Biomonitoring and Benthic Macroinvertebrates: New York, Chapman & Hall, p. 1-33.

Shields, F.D., Jr., Bowie, A.J., and Cooper, C.M., 1995, 

Control of streambank erosion due to bed degradation 

with vegetation and structure: Water Resources Bulletin, v. 31, p. 475-489.

Shields, F.D., Jr., Knight, S.S., and Cooper, C.M., 1995a, 

Streambank protection and habitat restoration, in Proceedings of the 1st International Conference Water 

Resources Engineering Division/American Society of 

Civil Engineers, San Antonio, Tex., p. 721-725.

 1995b, Rehabilitation of watersheds with incising 

channels: Water Resources Bulletin, v. 31, p. 971-982.

Stevens, H.H., Jr., Ficke, J.F., and Smoot, G.F., 1975, Water 

temperature-influenced factors, field measurements, 

and data presentation: Techniques of Water-Resources 

Investigations of the United States Geological Survey, 

Book 1, Chapter D 1,65 p.

26 Instream Investigations in the Beaver Creek Watershed in 

West Tennessee, 1991-95
Transport of Aldicarb and Aldicarb Metabolites in Runoff 

from Agricultural Fields in the Beaver Creek Watershed, 

West Tennessee

By SHANNON D. WILLIAMS___________________

U.S. GEOLOGICAL SURVEY

Prepared in cooperation with the 

Tennessee Department of Agriculture

Transport of Aldicarb and Aldicarb Metabolites in Runoff 

from Agricultural Fields in the Beaver Creek Watershed, 

West Tennessee

By Shannon D. Williams 

Abstract

Aldicarb and its metabolites were detected 

in runoff during several rainfall events monitored 

from 1991 to 1995. The maximum concentrations 

detected were 410, 68, and 14 micrograms per 

liter for aldicarb, aldicarb sulfoxide, and aldicarb 

sulfone, respectively. These concentrations were 

detected during rain events occurring shortly after 

the application of aldicarb to fields. Aldicarb concentrations detected in runoff samples were below 

analytical detection limits within a few weeks of 

aldicarb application. Aldicarb sulfoxide and aldicarb sulfone were more persistent, with concentrations of about 1 microgram per liter detected as 

late as 76 days after aldicarb application. The data 

indicated that a potential exists for significant 

transport of aldicarb and its metabolites if severe 

rain events occur shortly after the application of 

aldicarb.

INTRODUCTION

Pesticides transported in runoff from cropland 

may have detrimental effects on water quality and 

aquatic biological communities in receiving streams. 

In 1989, the U.S. Geological Survey (USGS) entered 

into a cooperative agreement with the Tennessee 

Department of Agriculture to assess the effect of agricultural activities on water quality in the Beaver Creek 

watershed in West Tennessee (fig. 1). One objective of 

the project was to quantify the transport of pesticides 

from agricultural fields.

About 70 percent of the 95,000 acres in the Beaver Creek watershed is under row-crop cultivation 

with cotton, soybeans, corn, and winter wheat being 

the major crops. Aldicarb is a carbamate pesticide,

which is widely used as an insecticide and nematicide 

for cotton crops in the Beaver Creek watershed and 

other areas of West Tennessee. This report describes 

the transport of aldicarb and its metabolites, aldicarb 

sulfoxide and aldicarb sulfone, in storm runoff in a 

first order stream draining 422 acres in the Beaver 

Creek watershed.

The stream is located in a bottomland area with 

land slopes ranging from 2 to 12 percent. Soils in the 

drainage area are classified as silt loams, with the principal soil series being the Falaya series. Falaya silt 

loam is a somewhat poorly drained, very silty, nearly 

level soil (U.S. Department of Agriculture, Soil Conservation Service, 1989). Approximately 90 percent of 

the 422 acres in the drainage area is under cultivation 

of cotton, corn, soybeans, and winter wheat. The number of acres of cotton grown was 59 in 1991, 93 in 

1992, 102 in 1993, and 113 in 1995. The application 

rate for aldicarb was 0.67 pound per acre of the active 

ingredient.

ALDICARB PROPERTIES

Aldicarb is relatively toxic by oral, dermal, and 

inhalation routes of exposure. LC50 (median lethal 

concentration) values for bluegill sunfish and rainbow 

trout are reported as 50 and 560 micrograms per liter 

(ug/L), respectively (U.S. Environmental Protection 

Agency, 1988). Although aldicarb is considered toxic, 

organisms tend to exhibit a more rapid and spontaneous recovery from poisoning by carbamates than from 

poisoning by other types of pesticides, such as organophosphorus compounds (Fukuto, 1987).

Aldicarb is applied to cropland in a granular 

form and is typically incorporated into the soil during 

planting. Degradation of aldicarb begins immediately 

after application. Aldicarb rapidly degrades to aldicarb 

sulfoxide through oxidation, followed by slower

Transport of Aldicarb and Aldicarb Metabolites 29
TENNESSEE

eaver Creek watershed

STUDY AREA

Stream-gaging station and 

storm sampling site Constructed 

wetland cell ; 

(not to scale)

Woody riparian 

stream reach

Herbacious ripar/an

Figure 1 . Location of the study area at the Beaver Creek watershed, West Tennessee.

30 Instream Investigations in the Beaver Creek Watershed in 

West Tennessee, 1991-95
oxidation to aldicarb sulfone (Hanson and Spiegel, 

1983; Lightfoot and others, 1987). Aldicarb and its 

metabolites also hydrolyze to form noncarbamate 

oximes and nitriles, which have relatively low toxicities and which continue to degrade to even less toxic 

compounds (Fukuto, 1987; Lightfoot and others, 

1987). Half-lives for aldicarb, aldicarb sulfoxide, and 

aldicarb sulfone in surface soils have been reported to 

range from 0.5 to 3 months, depending upon environmental conditions, such as pH and temperature (Lightfoot and others, 1987; Olsen and others, 1994).

Aldicarb is generally considered to be highly 

water soluble. Normally characterized as having high 

leaching and low surface runoff potential, aldicarb is 

not expected to move horizontally from a bare, sloping 

field (U.S. Environmental Protection Agency, 1988). 

Because of these properties, most studies that have 

examined the fate and transport of aldicarb focused on 

the vertical transport of aldicarb through the soil profile and were mainly concerned with the leaching of 

aldicarb and its metabolites into ground water.

Previous studies conducted by the USGS in 

West Tennessee indicate that little aldicarb and its 

metabolites are leaching into ground water in the Beaver Creek area (Olsen and others, 1994). A study 

examining the transport and degradation of aldicarb in 

the soil profile in the Beaver Creek watershed indicated minima] vertical transport of aldicarb and its 

metabolites was occurring (Olsen and others, 1994). 

These findings are supported by the results of a 

ground-water quality study for the shallow aquifers in 

the watershed and surrounding areas. Aldicarb was not 

detected in water samples collected from almost 

400 domestic wells in Shelby, Tipton, Fayette, and 

Hay wood Counties (Fielder and others, 1994). The 

apparent lack of vertical movement of aldicarb in the 

soil profile indicates that in West Tennessee more 

potential exits for transport of aldicarb in surface runoff than normally would be expected.

Water samples collected from 1991 to 1993 

were sent to The Institute of Wildlife and Environmental Toxicology (TIWET) at Clemson University for 

analysis of aldicarb, aldicarb sulfoxide, and aldicarb 

sulfone. Extraction of samples was performed using 

TIWET standard operational procedure 401-53-01. 

Extracted samples were analyzed using reverse-phase 

high pressure liquid chromatography (HPLC). Analytical detection limits for aldicarb and its metabolites 

were 0.33 ^ig/L in 1991 and 0.67 ng/L thereafter. 

Water samples collected during 1995 were sent to the 

USGS Water-Quality Laboratory in Ocala, Florida, for 

analysis of aldicarb. These samples were analyzed 

using enzyme linked immunosorbent assay (ELISA) 

methods, which have an estimated detection limit of 

0.25 ng/L for aldicarb (Olsen and others, 1994).

Hydrographs and chemographs for each rainfall 

event were prepared to examine discharge and concentration patterns. Discharge was calculated with stagedischarge rating curves developed by using methods 

described by Kennedy (1983). Loads (L) for individual runoff events were calculated using the sum of 

individual interval loads:

(i)

where

Ci is the ith interval of sampled concentration, 

qt is the instantaneous discharge at the time the

sample was collected,

?,- is the time interval associated with the sample, 

K is a unit conversion factor, and 

n is the number of samples.

This method assumes that the sampled concentration 

and the corresponding discharge value are representative of the time interval tj, that is equal to half the time 

from the preceding sample to the current sample plus 

half the time from the current sample to the following 

sample.

DATA COLLECTION AND ANALYSIS

Water samples for the determination of aldicarb 

and its metabolites were collected at a USGS streamgaging station using automatic samplers (fig. 1). Water 

samples were collected during selected rainfall/runoff 

events from 1991 through 1995, normally at 5- to 

15-minute intervals. Upon collection, samples were 

chilled in ice and sent to laboratories for analyses.

TRANSPORT OF ALDICARB

During a storm occuring 7 days after aldicarb 

application in 1991, concentrations of aldicarb and its 

metabolites increased rapidly as stormflow began, 

peaked shortly before the peak discharge, and then 

declined rapidly (fig. 2). Hydrographs and chemographs for other storm events typically exhibited the 

same patterns. These results indicate that aldicarb and

Transport of Aldicarb and Aldicarb Metabolites 31
 Discharge

 Aldicarb

* Aldicarb Sulfoxide

 Aldicarb Sulfona

6 8 10 12 

Hours from beginning of event

14

160

-140

120 =

-100 1

-0

Figure 2. Hydrograph and chemograph for a rainfall/runoff event on May 25, 1991.

its metabolites are transported in solution from surface 

and near surface soils.

Concentrations

Aldicarb and its metabolites were detected in 

runoff during several storms (table 1). The maximum 

concentrations of aldicarb, aldicarb sulfoxide, and 

aldicarb sulfone detected were 410, 68, and 14 |ig/L, 

respectively. The highest concentrations of aldicarb 

and aldicarb sulfoxide were detected during rainfall/ 

runoff events occurring a few hours to a few day after 

aldicarb application. Maximum aldicarb sulfone concentrations appear to occur in rainfall/runoff events 

occurring several days to a few weeks after aldicarb 

application, which is consistent with the aldicarb degradation process to aldicarb sulfoxide which then 

degrades to aldicarb sulfone.

Many of the aldicarb, aldicarb sulfoxide, and 

aldicarb sulfone concentrations detected are at levels 

that could possibly be detrimental to aquatic organisms based on reported toxicity data (Landau and 

Tucker, 1984; Foran and others, 1985; U.S. Environmental Protection Agency, 1988; Fisher, 1991). Most 

of the reported toxicity data, however, are based on 

exposure times of 48 to 96 hours. Concentrations of 

aldicarb and its metabolites at the study site tended to

peak within a few hours after the beginning of a rainfall event, and they tended to return to relatively low 

levels sooner than 48 hours. Therefore, the toxic 

effects of aldicarb and its metabolites on organisms at 

the study site may not be as great as those reported in 

the literature.

Aldicarb concentrations in the runoff samples 

collected were below detection limits within a few 

weeks after aldicarb application. However, the aldicarb metabolites were detectable at low concentrations 

in runoff for a longer period of time. Concentrations of 

about 1.0 |ig/L for both metabolites were detected in 

samples collected during a rainfall/runoff event occurring 76 days after application in 1993.

The results for samples collected during 1995 

were determined using enzyme-linked immunosorbent 

assay kits for aldicarb that cannot distinguish between 

aldicarb and its metabolites. The detected concentrations likely consisted mostly of aldicarb sulfoxide and 

aldicarb sulfone instead of aldicarb itself. The concentrations detected were consistent with the combined 

concentrations of aldicarb and its metabolites detected 

during previous years at similar times after aldicarb 

application.

32 Instream Investigations in the Beaver Creek Watershed in 

West Tennessee, 1991-95
Loads

For the storm events examined, the largest transport of aldicarb and its metabolites in storm runoff 

occurred on May 25,1991 (table 1). The highest maximum load values of aldicarb, aldicarb sulfoxide, and 

aldicarb sulfone were all recorded after the storm on 

May 5, 1991. The values detected were 1,100, 420, 

and 41 grams, respectively. Approximately 9 percent 

of the aldicarb applied in 1991 was transported from 

the drainage area during this event. Almost 2 inches of 

rain was deposited on the drainage area during this 

storm, which occurred 7 days after aldicarb was 

applied to fields. The total percentage of aldicarb 

transported from fields in runoff each year could not 

be estimated since data were collected only during a 

few rainfall/runoff events.

Maximum concentrations detected in storm runoff on May 18, 1993 were much higher than those 

detected on May 25, 1991; however, smaller loads of 

aldicarb and its metabolites occurred during the

May 18,1993 storm. The concentrations were higher 

because this storm occurred within a few hours of aldicarb application. The storm loads were lower even 

though concentrations were higher because the rainfall/runoff event was relatively small. Only 0.2 inch of 

rainfall occurred during this storm, and the peak discharge was 93 percent lower than the peak discharge 

on May 25, 1991.

SUMMARY

In 1989, the U.S. Geological Survey entered 

into a cooperative agreement with the Tennessee 

Department of Agriculture to assess the impact of 

agricultural activities on water quality in the Beaver 

Creek watershed in West Tennessee. Aldicarb is a carbamate pesticide, which is widely used as an insecticide and nematicide for cotton crops in the 

95,000-acre Beaver Creek watershed, 70 percent of

Table 1 . Summary of aldicarb, aldicarb sulfoxide, aldicarb sulfone concentrations and loads measured during selected 

rainfall/runoff events from 1991 to 1995

[ft3/s, cubic feet per second, Hg/L, micrograms per liter, , data not available; <, less than; *, results determined using enzyme-linked immunosorbent 

assay methods that detect aldicarb and its sulfoxide and sulfone metabolites]

Maximum concentrations Loads

Storm 

date

05/25/91

06/11/91

06/12/91

07/03/91

07/24/91

08/09/91

10/30/91

11/01/91

Days 

after 

aldicarb 

application

7

24

25

46

67

83

165

167

Total 

rainfall 

(inches)

1.98

0.8

0.2

--

--

-

--

_.

Peak 

discharge 

(ft3/s)

100

27

18

33

19

59

3

19

Aldicarb 

(M9/1-)

140

20

2.4

<0.33

<0.33

<0.33

<0.33

<0.33

Aldicarb 

sulfoxide 

(M9/L)

68

14

9.5

0.41

<0.33

<0.33

<0.33

<0.33

Aldicarb 

sulfone 

(M9/L)

9.5

14

11

3.6

<0.33

<0.33

<0.33

<0.33

Aldicarb 

(grams)

1,100

15

0.2

0.0

0.0

0.0

0.0

0.0

Aldicarb 

sulfoxide 

(grams)

420

9.7

1.1

0.03

0.0

0.0

0.0

0.0

Aldicarb 

sulfone 

(grams)

41

12

3.8

5.2

0.0

0.0

0.0

0.0

06/26/92 47 2.0 47 <0.67 3.4 4.2 0.0 11 14

05/18/93

08/02/93

06/06/95

06/11/95

06/21/95

06/25/95

0

76

14

19

29

33

0.2

1.9

0.9

--

0.1

0.7

8

90

21

--

3

14

410 42 2.1 520 81

<0.67 1.0 1.4 0.0 13

*28

*34

*36

*19

0.31

21

~

--

--

-

Transport of Aldicarb and Aldicarb Metabolites 33
which is under row-crop cultivation with cotton, soybeans, corn, and winter wheat.

Soils in the drainage area are classified as silt 

loams, with the principal soil series being the Falaya 

series a somewhat poorly drained, very silty, nearly 

level soil. Previous studies indicate that these soils and 

physical characteristics of the drainage area may limit 

the vertical movement of aldicarb and its metabolites 

through the soil profile, keeping them in surface and 

near-surface soils. Therefore, aldicarb and its metabolites may be more susceptible to be transported in surface runoff than normally would be expected.

Water samples for the determination of aldicarb 

and its metabolites were collected during selected 

rainfall/runoff events from 1991 to 1995, normally at 

5- to 15-minute intervals. Analytical detection limits 

for aldicarb and its metabolites were 0.33 |ig/L in 

1991 and 0.67 |ig/L thereafter. Hydrographs and 

chemographs for each rainfall event were prepared to 

examine discharge and concentration patterns. Concentrations of aldicarb and its metabolites increased 

rapidly as stormflow began, peaked shortly before the 

peak discharge, and then declined rapidly. These 

results also indicate that aldicarb and its metabolites 

are transported in solution from surface and nearsurface soils.

The highest concentrations of aldicarb and its 

metabolites in rainfall/runoff events occurred shortly 

after aldicarb application, before adequate time had 

elapsed for these substances to be degraded. The highest concentrations detected were 410, 68, and 14 |ig/L 

for aldicarb, aldicarb sulfoxide, and aldicarb sulfone, 

respectively. Aldicarb appeared to degrade relatively 

fast, with little aldicarb (<0.67 |ig/L) detected in storm 

runoff occurring a few weeks after aldicarb application. However, the aldicarb metabolites (1.0 |ig/L) 

were detected in storm runoff occurring as long as 

76 days after application.

Several of the aldicarb, aldicarb sulfoxide, and 

aldicarb sulfone concentrations exceeded values 

reported in toxicity data for various aquatic organisms. 

However, the exposure times to high concentrations of 

aldicarb and its metabolites at the study site are significantly shorter than the exposure times used to develop 

the toxicity data, making the toxic effects of aldicarb 

and its metabolites at the study site difficult to determine.

After the storm on May 25, 1991, the highest 

maximum load values of aldicarb, aldicarb sulfoxide, 

and aldicarb sulfone were all recorded at 1,100,420, 

and 41 grams, respectively. Approximately 9 percent 

of the aldicarb applied in 1991 was transported from

the drainage area during the May 25,1991 storm. Data 

from the May 25,1991 and the May 18,1993 storms 

indicate that the potential exists for significant losses 

of aldicarb and its metabolites if severe rain events 

occur soon after pesticide application.

SELECTED REFERENCES

Fielder, A.M., Roman-Mas, Angel, and Bennett, M.W., 

1994, Reconnaissance of ground-water quality at 

selected wells in the Beaver Creek watershed, Shelby, 

Fayette, Tipton, and Haywood Counties, West Tennessee, July and August 1992: U.S. Geological Survey 

Open-File Report 93-366, 28 p.

Fisher, S.W., 1991, Changes in the toxicity of three pesticides as a function of environmental pH and temperature: Bulletin of Environmental Contamination and 

Toxicology, v. 46, no. 2, p. 197-202.

Foran, J.A., Germuska, P.J., and Delfino, J.J., 1985, Acute 

toxicity of aldicarb, aldicarb sulfoxide, and aldicarb 

sulfone to daphnia laevis: Bulletin of Environmental 

Contamination and Toxicology v. 35, no. 4, p. 546-550.

Fukuto, T.R., 1987, Organophosphorus and carbamate

esters: The anticholinesterase insecticides: Fate of Pesticides in the Environment, Proceedings of a Technical 

Seminar, p. 5-18. Oakland, Ca., Division of Agriculture and Natural Resources, University of Ca., 158 p.

Hansen, J.L., and Spiegel, M.H., 1983, Hydrolysis studies 

of aldicarb, aldicarb sulfoxide and aldicarb sulfone: 

Environmental Toxicology and Chemistry, v. 2, 

p. 147-153.

Kennedy, E.G., 1983, Computation of continuous records of 

streamflow: U.S. Geological Survey Techniques of 

Water Resources Investigations, Book 3, chapter A13, 

53 p.

Landau, M., and Tucker, J.W., Jr., 1984, Acute toxicity of 

EDB and aldicarb to young of two estuarine fish species: Bulletin of Environmental Contamination and 

Toxicology, v. 33, no. 2, p. 127-132.

Lightfoot, E.N., Thorne, PS., Jones, R.L., Hansen, J.L., and 

Romine, R.R., 1987, Laboratory studies on mechanisms for the degradation of aldicarb, aldicarb sulfoxide and aldicarb sulfone: Environmental Toxicology 

and Chemistry, v. 6, p. 377-394.

Olsen, L.D., Roman-Mas, A., Weisskopf, C.P, and Klaine, 

S.J., 1994, Transport and degradation of aldicarb in the 

soil profile: A comparison of conventional tillage and 

non-tillage: Proceedings of the American Water 

Resources Association National Symposium on Water 

Quality, p. 31-42. Herndon, Va.: American Water 

Resources Association, 321 p.

U.S. Department of Agriculture, Soil Conservation Service, 

1989, Soil survey of Shelby County, Tennessee: Washington, D.C., U.S. Government Printing Office, 56 p. 

and 90 maps.

U.S. Environmental Protection Agency, 1988, Pesticide fact 

sheet: Aldicarb: Washington, D.C., Office of Pesticide 

Programs, 7 p.

34 Instream Investigations in the Beaver Creek Watershed in 

West Tennessee, 1991-95