Occurrence, Distribution, and Transport of Pesticides in 

Agricultural Irrigation-Return Flow from Four Drainage 

Basins in the Columbia Basin Project, Washington, 

2002-04, and Comparison with Historical Data

Scientific Investigations Report 2006–5005

Prepared in cooperation with the Bureau of Reclamation

U.S. Department of the Interior

U.S. Geological Survey
Cover: Photograph of Lind Coulee near Warden, Washington, about 1 mile west of 

State Route 17, looking downstream, July 2004. 

(Photograph taken by Richard Wagner, U.S. Geological Survey.)
Occurrence, Distribution, and Transport of 

Pesticides in Agricultural Irrigation-Return 

Flow from Four Drainage Basins in the 

Columbia Basin Project, Washington, 

2002-04, and Comparison with Historical 

Data

By Richard J. Wagner, Lonna M. Frans, and Raegan L. Huffman

Prepared in cooperation with the 

Bureau of Reclamation

Scientific Investigations Report 2006-5005

U.S. Department of the Interior

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

Gale A. Norton, Secretary

U.S. Geological Survey

P. Patrick Leahy, Acting Director

U.S. Geological Survey, Reston, Virginia: 2006

For sale by U.S. Geological Survey, Information Services

Box 25286, Denver Federal Center

Denver, CO 80225

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Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Wagner, R.J., Frans, L.M., and Huffman, R.L., 2006, Occurrence, distribution, and transport of pesticides in agricultural 

irrigation-return flow from four drainage basins in the Columbia Basin Project, Washington, 2002-04, and comparison 

with historical data: U.S. Geological Survey Scientific Investigations Report 2006-5005, 54 p. 
iii

Contents

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

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

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

Environmental Setting .............................................................................. 2

Acknowledgments ................................................................................. 6

Methods ................................................................................................... 6

Field Methods ....................................................................................... 6

Laboratory Methods .............................................................................. 7

Quality Assurance/Quality Control ............................................................... 11

Occurrence, Distribution, and Transport of Pesticides ............................................. 12

Field Measurements and Inorganic Constituents ............................................. 12

Occurrence and Distribution of Pesticides ...................................................... 18

Relation of Pesticide Use and Pesticides Detected .......................................... 29

Pesticide-Use Data ........................................................................... 29

Pesticides Applied and Detected in Surface-Water Samples ........................... 30

Transport of Pesticides ........................................................................... 35

Comparison of Pesticide Detections with Historical Data .............................. 35

Comparison with 1970s Data ............................................................... 35

Comparison with 1990s Data ............................................................... 35

Comparison of Pesticide Detections with National NAWQA Data ..................... 40

Summary ................................................................................................... 45

References Cited.......................................................................................... 46
iv

Tables

Table 1. Physical and land-use characteristics of the four irrigation return-flow

drainage basins sampled for pesticides, Columbia Basin Project,

Washington, July 2002 to October 2004................................................... 4

Table 2. Crop acreage estimates in the four irrigation return-flow drainage basins,

Columbia Basin Project, Washington, 2003 ............................................. 5

Table 3. Inorganic and organic analytes and schedules, analytical methods, and 

references.................................................................................... 7

Table 4. Pesticide target analytes, laboratory reporting levels, drinking water

standards or guidelines, and aquatic-life benchmarks ................................. 8

Table 5. Summary of field measurements and concentrations of inorganic

constituents in surface-water samples collected from the four irrigation

return-flow drainage basins, Columbia Basin Project, July 2002 through

October 2004 ................................................................................. 12

Figures

Figure 1. Map showing locations of the four irrigation return-flow drainage basins

and surface-water sampling sites, Columbia Basin Project, Washington............ 3

Figure 2. Graph showing concentrations of dissolved solids in the four irrigation

return-flow drainage basins, Columbia Basin Project, Washington, July 2002

to October 2004 .............................................................................. 15

Figure 3. Piper diagram showing percentage of major ions in surface water from the

Columbia River and from the four irrigation return-flow drainage basins,

Columbia Basin Project, Washington ................................................... 16

Figure 4. Graphs showing pesticide concentrations in four irrigation return-flow

drainage basins, Columbia Basin Project, Washington, July 2002 to 

October 2004 ................................................................................. 28

Figure 5. Graphs showing pesticide-application rates and percentage of

surface-water samples with pesticide detections in the four irrigation

return-flow drainage basins, Columbia Basin Project, Washington, July 2002

to October 2004 .............................................................................. 31

Figure 6 Boxplots showing comparison of historical and current pesticide

concentrations in the Crab Creek and Sand Hollow irrigation return-flow

drainage basins, Columbia Basin Project, Washington................................. 38

Figure 7. Graphs showing concentrations of simazine and terbacil in the Lind Coulee

irrigation return-flow drainage basin, Columbia Basin Project, Washington,

1994 to 2004 ................................................................................. 39

Figure 8. Graphs showing comparison of selected pesticide concentrations in the

Columbia Basin Project, Washington, July 2002 to October 2004 with

national NAWQA concentrations ......................................................... 41

Figure 9. Graphs showing concentrations of nitrate plus nitrite and atrazine in

samples from streamflow-gaging stations in the four irrigation return-flow

drainage basins, Columbia Basin Project, Washington, July 2002 to 

October 2004 ................................................................................. 42
Table 6. Summary of calculated major ion ratios in surface-water samples collected

from the four irrigation return-flow drainage basins, Columbia Basin Project,

and the Columbia River, Washington, July 2002 to October 2004 ..................... 17

Table 7. Maximum concentrations and number of pesticide detections in the four

irrigation return-flow drainage basins, Columbia Basin Project, Washington,

July 2002 to October 2004 .................................................................. 19

Table 8. Summary of pesticide concentrations in the four irrigation return-flow

drainage basins, Columbia Basin Project, Washington, July 2002 to 

October 2004 ................................................................................. 20

Table 9. Summary of pesticide toxicity values for freshwater fish in the Columbia

Basin Project, Washington ............................................................... 24

Table 10. Herbicides applied to irrigation canals, roads, and rights of way along

irrigation canals, drains, and return flows in the four irrigation return-flow

drainage basins, Columbia Basin Project, 2003.......................................... 29

Table 11. Estimated application for residential use of non-agricultural pesticides

detected in water samples from the four irrigation return-flow drainage

basins, Columbia Basin Project, Washington, July 2002 to October 2004 ............ 30

Table 12. Pesticides with no reported residential or major agricultural use detected in

water samples from the four irrigation return-flow drainage basins,

Columbia Basin Project, Washington, July 2002 to October 2004 ..................... 30

Table 13. Detection rates of pesticides analyzed during the 1970s and from July 2002

to October 2004 in Crab Creek and Lind Coulee irrigation return-flow

drainage basins, Columbia Basin Project, Washington................................. 35

Table 14. Detection rates of pesticides analyzed for during the 1990s and from July

2002 to October 2004 in the Crab Creek, Lind Coulee, and Sand Hollow

irrigation return-flow drainage basins, Columbia Basin Project, Washington ...... 36

Table 15. Physical and chemical properties of pesticides frequently detected in four

irrigation-return flow drainage basins in the Columbia Basin Project,

Washington, July 2002 to October 2004................................................... 44

Table 16. Concentrations and precision data for pesticide replicate samples,

Columbia Basin Project, Washington, July 2002 to October 2004 ..................... 49

Table 17. Percentage of mean recoveries from field-matrix-pesticide analyses,

Columbia Basin Project, Washington, July 2002 to October 2004 ..................... 49

Table 18. Pesticide concentrations analyzed by gas chromatography/mass

spectrometry and high-performance liquid chromatography/mass

spectrometry, Columbia Basin Project, Washington, July 2002 to 

October 2004 ................................................................................. 51

Table 19. Registration status of pesticides analyzed, Columbia Basin Project,

Washington, July 2002 to October 2004................................................... 53

Table 20. Summary of pesticides not detected, Columbia Basin Project, Washington,

July 2002 to October 2004 .................................................................. 54

Tables—Continued
vi

Conversion Factors and Datums

Conversion Factors

Multiply By To obtain

acre 4,047 square meter

acre 0.001562 square mile

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

foot (ft) 0.3048 meter

inch (in.) 2.54 centimeter 

liter (L) 33.82 ounce, fluid

mile (mi) 1.609 kilometer

pound, avoirdupois (lb) 0.4536 kilogram

square mile (mi2) 2.590 square kilometer

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

 °F=(1.8×°C)+32.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 

25 °C).

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) 

or micrograms per liter (μg/L).

Datum

Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD27) 

and North American Datum of 1983 (NAD83).
Abstract

Water-quality samples were collected from sites in 

four irrigation return-flow drainage basins in the Columbia 

Basin Project from July 2002 through October 2004. Ten 

samples were collected throughout the irrigation season 

(generally April through October) and two samples were 

collected during the non-irrigation season. Samples were 

analyzed for temperature, pH, specific conductance, dissolved 

oxygen, major ions, trace elements, nutrients, and a suite 

of 107 pesticides and pesticide metabolites (pesticide 

transformation products) and to document the occurrence, 

distribution, and pesticides transport and pesticide metabolites.

The four drainage basins vary in size from 19 to 

710 square miles. Percentage of agricultural cropland ranges 

from about 35 percent in Crab Creek drainage basin to a 

maximum of 75 percent in Lind Coulee drainage basin. More 

than 95 percent of cropland in Red Rock Coulee, Crab Creek, 

and Sand Hollow drainage basins is irrigated, whereas only 30 

percent of cropland in Lind Coulee is irrigated. 

Forty-two pesticides and five metabolites were detected 

in samples from the four irrigation return-flow drainage 

basins. The most compounds detected were in samples from 

Sand Hollow with 37, followed by Lind Coulee with 33, Red 

Rock Coulee with 30, and Crab Creek with 28. Herbicides 

were the most frequently detected pesticides, followed by 

insecticides, metabolites, and fungicides. Atrazine, bentazon, 

diuron, and 2,4-D were the most frequently detected 

herbicides and chlorpyrifos and azinphos-methyl were the 

most frequently detected insecticides. 

A statistical comparison of pesticide concentrations in 

surface-water samples collected in the mid-1990s at Crab 

Creek and Sand Hollow with those collected in this study 

showed a statistically significant increase in concentrations for 

diuron and a statistically significant decrease for ethoprophos 

and atrazine in Crab Creek. Statistically significant increases 

were in concentrations of bromacil, diuron, and pendimethalin 

at Sand Hollow and statistically significant decreases were in 

concentrations of 2,6-diethylanaline, alachlor, atrazine, DCPA, 

and EPTC. A seasonal Kendall trend test on data from Lind 

Coulee indicated no statistically significant trends for any 

pesticide for 1994 through 2004. 

A comparison of pesticide concentrations detected in 

this study with those detected in previous U.S. Geological 

Survey National Water-Quality Assessment studies of the 

Central Columbia Plateau, Yakima River basin, and national 

agricultural studies indicated that concentrations in this study 

generally were in the middle to lower end of the concentration 

spectrum for the most frequently detected herbicides and 

insecticides, but that the overall rate of detection was near the 

high end.

Thirty-one of the 42 herbicides, insecticides, and 

fungicides detected in surface-water samples were applied 

to the major agricultural crops in the drainage basins, and 11 

of the detected pesticides are sold for residential application. 

Eight of the pesticides detected in surface-water samples 

were not reported as having any agricultural or residential 

use. The overall pattern of pesticide use depends on which 

crops are grown in each drainage basin. Drainage basins 

with predominantly more orchards have higher amounts of 

insecticides applied, whereas basins with larger percentages 

of field crops tend to have more herbicides applied. Pesticide 

usage was most similar in Crab Creek and Sand Hollow, 

where the largest total amounts applied were the insecticides 

azinphos-methyl, carbaryl, and chlorpyrifos and the herbicide 

EPTC. In Red Rock Coulee basin, DCPA was the most heavily 

applied herbicide, followed by the fungicide chlorothalonil, 

the herbicide EPTC, and the insecticides chlorpyrifos 

and azinphos-methyl. In Lind Coulee, which has a large 

percentage of dryland agricultural area, the herbicides 2,4-D 

and EPTC were applied in the largest amount, followed by 

the fungicide chlorothalonil. The total amount of pesticides 

applied by residential homeowners and irrigation districts was 

negligible compared to total amounts applied to agricultural 

crops. 

Occurrence, Distribution, and Transport of Pesticides in 

Agricultural Irrigation-Return Flow from Four Drainage 

Basins in the Columbia Basin Project, Washington, 

2002-04, and Comparison with Historical Data

By Richard J. Wagner, Lonna M. Frans, and Raegan L. Huffman
The State of Washington criterion of measuring water 

temperature by the 7-day average of the daily maximum 

temperatures was beyond the scope of this study, so water 

temperatures are only an indication of instantaneous 

temperatures at the time of sampling. Water temperature in 

18 samples was greater than the State criterion of 16 degrees 

Celsius for salmon and trout spawning, core rearing, and 

migration: 7 in Red Rock Coulee, 5 in Crab Creek, 4 in Lind 

Coulee, and 2 in Sand Hollow. In 11 of these 18 samples, 

water temperature also was greater than the criterion of 

17.5 degrees Celsius for salmon and trout spawning, non-core 

rearing, and migration. The State of Washington aquatic-life 

dissolved-oxygen criterion of 9.5 milligrams per liter for 

salmon and trout spawning, core rearing, and migration was 

exceeded eight times from June to early October: two times 

at Sand Hollow, three times at Red Rock Coulee, and three 

times at Crab Creek. The State of Washington aquatic-life 

pH criterion of 8.5 for fresh water was exceeded 12 times, 6 

at Red Rock Coulee, 3 at Sand Hollow, 2 at Lind Coulee and 

1 at Crab Creek. Concentrations of nitrate plus nitrite in two 

samples collected from Sand Hollow during the non-irrigation 

season exceeded the U.S. Environmental Protection Agency 

Maximum Contaminant Level for drinking water.

Concentrations of three insecticides and one herbicide 

exceeded U.S. Environmental Protection Agency or Canadian 

benchmark for the protection of freshwater aquatic life. 

Concentrations of the insecticide azinphos-methyl exceeded 

the aquatic-life benchmark at least once at each of the 

four sites. Concentrations in samples from Sand Hollow 

also exceeded the aquatic-life benchmark for chlorpyrifos, 

lindane, and dinoseb (0.041, 0.01, and 0.05 micrograms 

per liter, respectively). Water-quality benchmarks generally 

were exceeded in June and July, during the middle of the 

irrigation season, except the benchmark for dinoseb, which 

was exceeded in one sample during the non-irrigation season 

in February 2003.

Introduction

The National Marine Fisheries Service’s (NMFS) 

2000 Biological Opinion on the operation of the Federal 

Columbia River Power System (National Marine Fisheries 

Service, 2000) includes a recommendation to the Bureau 

of Reclamation to monitor water-quality characteristics of 

surface-water irrigation return flows to the Columbia River at 

various points in the Columbia Basin Project (CBP) in central 

Washington State. The presence of selected pesticides in 

these return flows at levels that may harm or adversely affect 

salmon and steelhead species listed for protection under the 

Endangered Species Act was of specific interest to NMFS.

In cooperation with the Bureau of Reclamation, the U.S. 

Geological Survey (USGS) included the sampling of surface 

water in four irrigation return-flow drainage basins in the 

CBP as an ancillary project to the second phase of the Central 

Columbia Plateau-Yakima (CCYK) National Water-Quality 

Assessment (NAWQA) Program. The NAWQA program uses 

procedures for sampling and analyzing pesticides and other 

analytes of interest in surface water that assures high-quality, 

representative data for many commonly used pesticides, 

and using these same methods for additional CBP sites is 

beneficial to assure data comparability.

Water-quality samples collected from streamflowgaging station sites in the Crab Creek, Sand Hollow, Red 

Rock Coulee, and Lind Coulee drainage basins from July 

2002 through October 2004 were analyzed for a suite of 107 

pesticides and pesticide metabolites (pesticide transformation 

products), as well as concentrations of major ions, trace 

elements, and nutrients. The data were used to describe 

the occurrence, distribution, and transport of pesticides in 

agricultural irrigation return-flow water in the four irrigationreturn flow drainage basins. Pesticide concentrations were 

compared with drinking-water standards and aquatic-life 

benchmarks, and pesticide detections in samples from the 

irrigation-return flows was compared with historical data 

and related to current pesticide use, land use, and other 

environmental factors. 

Purpose and Scope

The purposes of this report are to (1) describe the 

occurrence, distribution, and transport of pesticides and 

pesticide metabolites in agricultural irrigation return-flow 

water in four drainage basins in the CBP; (2) describe the 

relation between pesticides detected in irrigation-return 

flows and current and historical pesticide use, land use, 

other environmental factors, and chemical properties of the 

pesticides; (3) discuss how measured pesticide concentrations 

compare with drinking-water standards and aquatic-life 

benchmarks; and (4) compare the results of this study with 

those from historical studies in the 1970s, 1990s, and the 

national NAWQA database. Four irrigation-return flow sites 

were sampled for pesticides 12 times from July 2002 through 

October 2004. Ten samples were collected throughout the 

irrigation season (generally April through October) and two 

samples were collected during the non-irrigation season.

Environmental Setting

The CBP is a multi-purpose project providing irrigation 

water to agricultural land in the Columbia River basin 

in central Washington (fig. 1). The CBP drainage area is 

more than 4,000 mi2 and is bounded on the west by the 

Columbia River and on the south by the Snake River, and 

it extends east and north to include all lands considered 

   Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
Figure 1. Locations of the four irrigation return-flow drainage basins and surface-water sampling sites, 

Columbia Basin Project, Washington.

waAE700_01.fig01

0 10 20 30 40 KILOMETERS 

0 10 20 30 40 MILES

FERRY STEVENS

KITTITAS

LIND COULEE

CRAB CREEK

SAND HOLLOW

RED ROCK COULEE

12464607

12464606

12472520

12471400

12472600

BENTON

YAKIMA

FRANKLIN

ADAMS

OKANOGAN

GRANT

DOUGLAS

CHELAN

WALLA WALLA

LINCOLN

Columbia

River Snake

River

Crab Creek

Sand Hollow

Crab Creek

Lateral

Royal Lake

Priest Rapids

 Lake

Lake

Roosevelt

Banks

Lake

Potholes

Reservoir

Red Rock

Lake

W A S H I N G T O N

FIGURE

LOCATION

EXPLANATION

12471400

USGS SURFACE-WATER 

 SAMPLING SITE AND NO.

COLUMBIA BASIN PROJECT 

 BOUNDARY

DRAINAGE-BASIN BOUNDARY

MIXED AGRICULTURE,

 PASTURE, AND FALLOW

ORCHARDS AND VINEYARDS

RANGELAND

URBAN

Vantage

Beverly

Richland Pasco

Moses Lake Quincy

Ephrata

Othello

Lind

Ritzville

120° 119°

48°

47°

O’Sullivan

Dam

Priest Rapids 

Dam

Base from U.S. Geological Survey, 1:100,000 quadrangle, 1995

Universal Transverse Mercator projection, Zone 10, NAD27

National Landcover Data, 1992

Base from U.S. Geological Survey 30-meter resolution

Albers Conic Equal Area projection, NAD83

economically irrigable from the project canal system (Bureau 

of Reclamation, 1982). Main geohydrologic units in the CBP 

are the Columbia Plateau River Basalt Group, extrusions 

of basalt lava that formed the Columbia Plateau between 6 

and 16.5 million years ago, and the overlying deposits of 

unconsolidated sediment (Drost and others, 1990). Columbia 

Plateau River Basalt Group flows are estimated to be more 

than 14,000 ft thick near Pasco, Washington. Parts of the 

CBP also contain loess, a wind-deposited silt, and sand dunes 

typified by those at Potholes Reservoir.

Introduction 
Major land use and economy in the CBP is agriculture, 

followed by livestock production and food processing. 

The land is primarily rural, but five towns in the CBP area 

have populations greater than 5,000: Pasco, Othello, Moses 

Lake, Ephrata, and Quincy. Pasco is the largest town, with 

a population of about 32,000 (U.S. Census Bureau, 2004). 

Climate in the CBP is semiarid, with about 6 to 10 in. of 

annual precipitation, and air temperatures range from below 

freezing in winter to more than 38°C at times during summer.

The CBP has few natural perennial streams, and 

streamflow in the project area is augmented and indirectly 

regulated by seasonal delivery of irrigation water (generally 

April to October) to the area. Irrigation water is pumped 

from Lake Roosevelt, stored in Banks Lake, and distributed 

throughout the CBP by a network of re-regulation reservoirs 

and conveyance canals to irrigated lands. Surface-water 

drainages from irrigated lands lead to wasteway returns that 

create irrigation-return flows to major streams and rivers. The 

large quantities of irrigation water delivered to farm units in 

the CBP indirectly control the irrigation-return flow in the four 

drainage basins studied in the project area during the irrigation 

season (table 1). Water samples were collected at USGS 

streamflow-gaging stations in the study basins, and continuous 

streamflow data were available only for Crab Creek and Lind 

Coulee.

Crab Creek irrigation-return drainage basin covers 

296 mi2, and water samples were collected at gaging station 

12472600, near Beverly (fig. 1). Before water was diverted 

from Lake Roosevelt for irrigation, Crab Creek was one of 

the few perennial streams in the CBP and flowed from the 

northeastern Columbia Plateau, about 3 mi east of Reardan, 

southwest to where it empties into the Columbia River near 

Beverly, Washington. Drifting sand dunes impounded Crab 

Creek and created Moses Lake, the largest natural lake in the 

CBP (Walters and Grolier, 1960). Construction of O’Sullivan 

Dam formed Potholes Reservoir, creating a central point in 

the CBP for storage of excess canal water, natural runoff, and 

irrigation-return flow and redistribution of water for irrigation 

reuse in the southern part of the CBP. The entire length of 

Crab Creek drains 4,840 mi2, but Moses Lake and Potholes 

Reservoir hydrologically separate the stream into Upper Crab 

Creek, the stretch from the headwaters to Moses Lake, and 

Lower Crab Creek, the stretch from O’Sullivan Dam to the 

mouth that includes the Crab Creek study basin. Potholes 

Reservoir has no perennial outlet to Lower Crab Creek, and 

most water in Lower Crab Creek comes from Goose Lake 

Wasteway. Hansen and others (1994) calculated average 

ground-water discharge to Lower Crab Creek as 76.3 ft3/s 

prior to irrigation development and 145.1 ft3/s for 1983–85. 

Therefore, water at the Crab Creek site near Beverly is directly 

affected by ground-water seepage from Potholes Reservoir and 

from tributary inflow downstream of O’Sullivan Dam. 

Sand Hollow drains the western flanks of Royal Slope 

and flows west, emptying into the Columbia River across from 

Vantage, Washington. Sand Hollow irrigation-return drainage 

basin covers 60 mi2 and represents a drainage basin of varied 

agricultural land uses that is irrigated primarily by surface 

water. The first water sample from Sand Hollow during this 

study was collected at S Road SW at gaging station 12464606 

(fig. 1). Historical data were collected at this site by NAWQA 

during the 1990s. The drainage area at this site is 43 mi2. All 

subsequent samples for this study were collected at the mouth 

at gaging station 12464607 (fig. 1), where one water sample 

was collected by the USGS in 1991 and sediment samples 

were collected in 1992. Although a minor tributary flows into 

Sand Hollow in the 3 mi between S Road SW and the mouth, 

land use is the same for the entire basin and data from both 

sampling sites are treated as one for data analysis in this study.

Table 1. Physical and land-use characteristics of the four irrigation return-flow drainage basins sampled for pesticides, Columbia Basin Project, 

Washington, July 2002 to October 2004.

[USGS, U.S. Geological Survey; ft3/s, cubic feet per second; mi2, square mile; S, south; Rd, Road; SW, Southwest; SR, State Route; >, greater than]

Irrigation 

return-flow 

basin

Sampling site

Short

name

Number of 

samples

Streamflow at time of 

sampling (ft3/s) Drainage 

area 

(mi2)

Harvested

cropland 

area

(mi2)

Percentage 

of harvested 

cropland

Percentage 

of irrigated 

USGS gaging station No. and name Median Minimum Maximum cropland

Crab Creek 12472600 Crab Creek near Beverly Crab Creek 12 214 129 331 1296 103 35 >95

Lind Coulee 12471400 Lind Coulee Wasteway at 

SR 17, near Warden

Lind Coulee 12 255 58 355 710 533 75 30

Red Rock 

Coulee

12472520 Red Rock Coulee near 

Smyrna

Red Rock 

Coulee

12 71.5 43 114 19 9 47 >95

Sand Hollow 12464606 Sand Hollow at S Rd SW, 

near Vantage

Sand Hollow 

at S Rd

1 79 79 79 43 36 70 >95

12464607 Sand Hollow at mouth, 

near Vantage

Sand Hollow 11 94 23 141 60 42 84 >95

1Drainage area is for Lower Crab Creek; the entire Crab Creek drainage area is 4,840 mi2.

   Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
Red Rock Coulee drains about 19 mi2 of irrigated 

agricultural land, beginning near the eastern boundary of Grant 

County, just north of Royal Lake, and flowing west to Red 

Rock Lake (fig. 1). Red Rock Coulee flows out of Red Rock 

Lake, passes through a culvert beneath county road E SW, 

flows south about 2.5 mi before crossing beneath county road 

E SW again, and continues another mile before emptying into 

Crab Creek. During this study, samples were collected from 

Red Rock Coulee downstream of the second culvert at gaging 

station 12472520, but during the NAWQA program, in 1994, 

one sample was collected about 1 mi upstream.

The headwaters of Lind Coulee combine with the flow 

of several smaller coulees south of Ritzville, and the main 

branch flows east through the town of Lind before joining 

with Weber Coulee and flowing another 5 mi to empty into 

Potholes Reservoir. Weber Coulee combines the flow from 

Bauer Coulee and Farrier Coulee, and the entire Lind Coulee 

basin drains about 710 mi2. Samples from Lind Coulee were 

collected at gaging station 12471400, about 1 mi downstream 

of the State Highway 17 crossing.

Agriculture crop acreage in the four irrigation-return flow 

drainage basins varies from year to year. Orchards usually are 

a long-term crop, but many field crops are rotated frequently. 

One primary rotation in the CBP is between alfalfa, corn, and 

potatoes. Estimates of agricultural acreage for 2003 in the 

four irrigation-return flow basins were used to describe the 

agricultural land use during this study (table 2; Patricia Daly, 

Franklin County Conservation District, written commun., 

2004). Percentage of agricultural harvested cropland varies 

from year to year, but ranged from 35 percent in Crab Creek 

basin to a maximum of 75 percent in Lind Coulee basin during 

this study. Harvested cropland was 47 percent in Red Rock 

Coulee basin and 70 percent in Sand Hollow basin during the 

current study. Most agricultural cropland in Red Rock Coulee, 

Sand Hollow, and Crab Creek drainage basins is irrigated, but 

only 30 percent of the crop acreage in Lind Coulee is irrigated 

(table 1). Alfalfa is the largest percentage of crop acreage in 

Crab Creek drainage basin, followed by orchards and irrigated 

wheat. Peas, corn, and potatoes are nearly 20 percent of crop 

acreage in the Crab Creek drainage basin (table 2). Nearly 

one-third of the crop acreage in Lind Coulee is in dryland 

wheat, and more than one-third of the acreage is fallow land. 

Minor percentages of the acreage in Lind Coulee drainage 

basin are in alfalfa, potatoes, and peas. The largest percentage 

of crop acreage in Red Rock Coulee drainage basin is alfalfa, 

followed by onions and orchards. Peas and irrigated wheat 

make up about 15 percent of the total agricultural acreage. 

The largest percentage of crop acreage in Sand Hollow also is 

alfalfa, followed by orchards. Peas and irrigated wheat make 

up about 30 percent of the total agricultural acreage, followed 

by minor percentages of grass, potatoes, and mint. 

Crop Acres Percentage of

crop acreage

Crab Creek

Alfalfa 24,292 37

Orchard 13,999 21

Wheat (irrigated) 6,662 10

Pea 5,172 8

Corn 3,666 6

Potato 3,600 5

Unclassified 2,598 4

Grass 1,814 3

Onion 1,603 2

Wheat (dryland) 1,189 2

Mint 983 1

Timothy 162 <1

Fallow 98 <1

Lind Coulee

Fallow 119,929 35

Wheat (dryland) 116,713 34

Wheat (irrigated) 33,835 10

Alfalfa 17,899 5

Potato 15,238 4

Unclassified 13,646 4

Corn 9,667 3

Pea 8,074 2

Orchard 4,206 1

Onion 1,183 <1

Grass 686 <1

Red Rock Coulee

Alfalfa 3,345 57

Onion 682 12

Orchard 536 9

Wheat (irrigated) 449 8

Pea 428 7

Potato 129 2

Corn 122 2

Unclassified 116 2

Grass 105 2

Sand Hollow 

Alfalfa 7,610 28

Orchard 4,746 18

Pea 4,091 15

Wheat (irrigated) 4,001 15

Grass 2,378 9

Potato 1,216 5

Mint 1,070 4

Corn 602 2

Unclassified 601 2

Fallow 181 1

Wheat (dryland) 164 1

Onion 125 <1

Table 2. Crop acreage estimates in the four irrigation return-flow 

drainage basins, Columbia Basin Project, Washington, 2003. 

[Data for crop-acreage estimates provided by Franklin County Conservation 

District (Patricia Daly, written commun., 2004). Percentage of crop acreage:

may not add to 100 percent due to rounding. <, less than]

Introduction 
Acknowledgments

The authors are grateful for the technical reviews 

by Frank Rinella (USGS, Portland, Oreg.), Angela Crain 

(USGS, Louisville, Ky.), and Bryan Horsburgh (Bureau of 

Reclamation, Boise, Idaho). We are grateful for the technical 

advice on aquatic toxicity from Patrick Moran (USGS, 

Tacoma, Wash.), Lisa Nowell (USGS, Sacramento, Calif.), and 

Mark Schneider (National Oceanographic and Atmospheric 

Administration Fisheries, Portland, Oreg.); for the agricultural 

crop acreages data provided by Patricia Daly (Franklin 

County Conservation District); and to Gina Hoff (Bureau 

of Reclamation, Ephrata, Wash.), Elizabeth Jordan (Quincy 

Basin Irrigation District, Quincy, Wash.), and Elaine Fuller 

(East Columbia Basin Irrigation District, Othello, Wash.), 

for non-agricultural aquatic herbicide application data. The 

contribution by Theresa Olsen (USGS, Tacoma, Wash.) to 

GIS illustrations and to analysis of crop pesticide-application 

data was invaluable. We are grateful to Dwight Copeland 

and Douglas Call (USGS, Pasco, Wash.), Brett Smith and 

Galen Schuster (USGS, Spokane, Wash.), and Richard Cornet 

(Bureau of Reclamation, Ephrata, Wash.) for their assistance 

in collecting samples for this study.

Methods 

Surface-water samples were collected from four irrigation 

return-flow drainage basins and analyzed for pesticides and 

pesticide metabolites, major ions, trace elements, and nutrients 

(table 3). The pesticides were selected by the NAWQA 

program (Gilliom and others, 1995) from a list of about 400 

pesticides most commonly used in the United States (Gianessi 

and Puffer, 1991, 1992a, 1992b). Each pesticide was selected 

on the basis of the following factors: a national use of more 

than 8,000 lb of active ingredient annually; inclusion in the 

analytical schedules of other Federal monitoring or survey 

programs; toxicity; leachability; and its ability to be trapped 

and extracted from the appropriate solid-phase-concentrating 

matrix. Samples for analysis of pesticides and major ions were 

collected and submitted to the USGS National Water Quality 

Laboratory (NWQL) in Lakewood, Colo., the samples for 

pesticides were analyzed using either gas-chromatography/

mass spectrometry (GC/MS) or high-performance liquid 

chromatography/mass spectrometry (HPLC/MS), depending 

on the physical characteristics of the target analytes. Samples 

for nutrient analysis were sent to the Bureau of Reclamation 

laboratory in Boise, Idaho.

Field Methods

The sampling site in each drainage basin was visited 

10 times during the irritation season and 2 times during the 

non-irrigation season from July 2002 to October 2004. During 

each visit, water temperature, pH, dissolved oxygen (DO) 

concentrations, and specific conductance were measured and 

water samples were collected for analysis of pesticides, major 

ions, trace elements, and nutrients. The first sample from 

Sand Hollow drainage basin was collected from the bridge at 

S Road SW and all subsequent samples were collected from 

the mouth of Sand Hollow before it empties into the Columbia 

River. One DO measurement was removed from the data set 

because of a faulty sensor. Samples representative of flow in 

the stream cross section were obtained by collecting depthintegrated subsamples at equally spaced verticals across the 

stream using a US DH-81 sampler as described by Edwards 

and Glysson (1999) and Wilde and others (1999a). The 

sampler holds a 1- or 3-L Teflon® bottle, and all parts of the 

sampler coming in contact with the water sample are made 

of Teflon®. Subsamples were composited and split using a 

Teflon® churn splitter (Wilde and others, 2004). From June 

through August 2002, the Teflon® churn was not available, 

so a polyethylene churn splitter was used. Subsamples for 

analysis of inorganic analytes were collected and split out 

using the churn. Samples for pesticides were collected 

directly into a 3-L Teflon® bottle from each section of the 

stream and were not composited into the polyethylene churn. 

Water samples for pesticides were drawn from the Teflon®

churn splitter (after August 2002) and filtered through a 

0.7-μm baked glass-fiber filter into 1-L baked glass bottles, 

stored at less than 4°C, and shipped to the NWQL within 

24 hours. Samples for major ions and nutrients were drawn 

from the churn splitter and filtered or preserved, if necessary. 

Subsamples for analysis of filtered nutrients were pumped 

through a disposable 0.45-μm filter cartridge into opaque 

polyethylene bottles and chilled to less than 4°C. Samples for 

analysis of unfiltered nutrients were collected in translucent 

polyethylene bottles and preserved with sulfuric acid to a 

pH less than 2. Samples for analysis of major ions also were 

filtered through a 0.45-μm filter cartridge, and samples for 

analysis of cations, iron, and manganese were acidified with 

nitric acid to a pH less than 2. Samples were shipped on ice to 

the NWQL for pesticide and major ions analysis, and samples 

were shipped to the Bureau of Reclamation Boise laboratory 

for nutrients analysis. All equipment used to collect and 

process samples was cleaned with a 0.2-percent non-phosphate 

detergent, soaked in a 5-percent hydrochloric acid solution, 

and rinsed with deionized water, as described in Wilde (2004). 

Equipment used to filter the pesticide samples was additionally 

rinsed with pesticide-grade methanol and pesticide-free 

reagent water. All cleaned equipment was placed in doubled 

plastic bags and stored in a dust-free environment prior to 

sample collection. 

 Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
Laboratory Methods

Samples for a broad spectrum of pesticides were 

analyzed at the NWQL using either gas chromatography/

mass spectrometry (GC/MS) or high-performance liquid 

chromatography/mass spectrometry (HPLC/MS) techniques 

(table 4). Compounds that were sufficiently volatile and 

thermally stable for gas chromatography were analyzed by 

GC/MS, as described by Zaugg and others (1995), Lindley and 

others (1996), and Madsen and others (2003); the remaining 

pesticides were analyzed by HPLC/MS, as described by 

Furlong and others (2001).

Analyte or schedule CAS registry No. Analytical method Analytical method reference

Inorganic compounds

Calcium 7440-70-2 ICP Fishman, 1993

Chloride 16887-00-6 IC Fishman and Friedman, 1989

Fluoride1 16984-48-8 ASF ISE Fishman and Friedman, 1989

Iron 7439-89-6 ICP Fishman, 1993 

Magnesium 7439-95-4 ICP Fishman, 1993 

Manganese 7439-96-5 ICP Fishman, 1993

Potassium2 7440-09-7 ICP American Public Health Association and others, 1998

Residue, 180°C Gravimetric Fishman and Friedman, 1989

Silica 7631-86-9 Colorimetry, ASF, molybdate blue Fishman and Friedman, 1989

Sodium 7440-23-5 ICP Fishman, 1993

Sulfate 14808-79-8 IC Fishman and Friedman, 1989

Ammonia as N ISE, USEPA Method 350.3 U.S. Environmental Protection Agency, 1979

Ammonia plus organic 

nitrogen as N

7727-37-9 Total Kjeldahl Nitrogen, 

(colorimetric, semi-automatic), 

USEPA Method 351.2

U.S. Environmental Protetection Agency, 1993

Nitrite plus nitrate as N Nitrate-Nitrite Nitrogen by 

colorimetry, USEPA 

Method 353.2

U.S. Environmental Protetection Agency, 1993

Orthophosphorus as P Phosphorus, all forms 

(colorimetric, automatic, 

ascorbic), USEPA 

Method 365.1

U.S. Environmental Protetection Agency, 1993

Phosphorus as P Phosphorus, all forms 

(colorimetric, automatic, 

ascorbic), USEPA 

Method 365.1

U.S. Environmental Protetection Agency, 1993

Organic compounds

Schedule 2001 Various (see table 4) SPE technology and GC/MS Zaugg and others, 1995; Lindley and others (1996); and 

Madsen and others (2003)

Schedule 2060 Various (see table 4) SPE technology and HPLC/MS Furlong and others (2001)

1

Analyzed by manual ISE method (Fishman and Friedman, 1989) from July 2002 through April 2003.

2

Analyzed by flame atomic absorption (Faires, 1993) prior to May 2003.

Table 3. Inorganic and organic analytes and schedules, analytical methods, and references.

[Abbreviations: °C, degrees Celsius; CAS, Chemical Abstract Services; IC, ion-chromatography; ASF, automated-segment flow; ISE, ion-selective 

electrode; ICP, inductively coupled plasma; SPE, solid-phase extraction; GC/MS, gas-chromatography/mass spectrometry; HPLC/MS, high-performance liquid 

chromatography/mass spectrometry; USEPA, U.S. Environmental Protection Agency]

The USGS NWQL collects water-quality control data 

on a continuing basis for method evaluation and to determine 

long-term method detection levels (LT-MDLs) and laboratory 

reporting levels (LRLs). Concentrations are reported as 

less than the LRL for samples in which the analyte was not 

detected or failed to meet necessary identification criteria. 

Analytes detected at concentrations lower than the lowest 

calibration standard or between the LT-MDL and the LRL 

and that pass identification criteria are reported with a remark 

code of “E”. In addition, some analytes generally have low 

or variable recovery and routinely are reported with an “E” 

remark code.

Methods    
Table 4. Pesticide target analytes, laboratory reporting levels, drinking water standards or guidelines, and aquatic-life benchmarks.

[If laboratory reporting level changed during the study, the most frequently used level is indicated. Pesticide target analyte: CIAT, 2-chloro-4-isopropylamino6-amino-s-triazine; CAAT, chlorodiamino-s-triazine; OIET, 2-hydroxy-4-isopropylamino-6-ethylamino-s-triazine; CEAT, 2-chloro-6-ethylamino-4-aminos-triazine; GC/MS, gas chromatography/mass spectrometry; HPLC/MS, high-performance liquid chromatography/mass spectrometry. Type of pesticide: F, 

fungicide; H, herbicide; I, insecticide; S, stimulant; T, transformation product. Drinking-water standards and guidelines: Maximum contaminant levels for 

drinking water from U.S. Environmental Protection Agency (2004a). Freshwater aquatic-life benchmark: From U.S. Environmental Protection Agency 

(2004b), unless otherwise footnoted. Abbreviations: CAS, Chemical Abstracts Service; μg/L, microgram per liter; –, no data or not available; *, interim values 

(Canadian Council of Resource and Environment Ministers, 1997)]

Pesticide target analyte Trade or common name(s) Type of 

pesticide CAS registry No.

Laboratory 

reporting level 

(μg/L)

Drinking-water 

standard or 

guideline 

(μg/L)

Freshwater 

aquatic-life 

benchmark

(μg/L)

Gas Chromatography/Mass Spectrometry analytical data

Acetochlor Acenit, Sacenid H 34256-82-1 0.006 – –

Alachlor Lasso H 15972-60-8 .005 2 –

Atrazine1 Aatrexx H 1912-24-9 .007 3 31.8

Azinphos-methyl2 Guthion I 86-50-0 .05 – .01

Benfluralin Balan, Benefin H 1861-40-1 .010 – –

Butylate Sutran +, Genate Plus H 2008-41-5 .004 4400 –

Carbaryl1,2 Sevin, Savit I 63-25-2 .041 4700 3.20

Carbofuran1,2 Furadan I 1563-66-2 .02 40 31.8

CIAT1,2 none T 6190-65-4 .006 – –

Chlorpyrifos Lorsban I 2921-88-2 .005 420 .041

Cyanazine Bladex H 21725-46-2 .018 41 32.0

DCPA Dacthal H 1861-32-1 .003 470 –

4,4’-DDE none T 72-55-9 .003 1 .001

Desulfinlylfipronil none T – .012 – –

Desulfinlylfipronil amide none T – .029 – –

Diazinon several I 333-41-5 .005 4.6 5.08

Dieldrin Panoram D-31 I 60-57-1 .009 6.02 .056

2,6-Diethylanaline none T 579-66-8 .006 – –

Disulfoton Di-Syston I 298-04-4 .021 4.3 –

EPTC Eptam, Eradicane H 759-94-4 .004 – –

Ethalfluralin Sonalan, Curbit EC H 55283-68-6 .009 – –

Ethoprophos Mocap I 13194-48-4 .005 – –

Fipronil Regent I 120068-37-3 .016 – –

Fipronil sulfide none T 120067-83-6 .013 – –

Fipronil sulfone none T 120068-36-2 .024 – –

Fonofos Dyfonate I 944-22-9 .003 410 –

alpha-HCH none I 319-84-6 .005 7.06 –

gamma-HCH Lindane I 58-89-9 .004 .2 3.01

Linuron1 Lorox, Linex H 330-55-2 .035 – 37*

Malathion several I 121-75-5 .027 4100 0.1

Methyl parathion Penncap-M I 298-00-0 .015 32 –

Metolachlor3 Dual, Pennant H 51218-45-2 .013 4100 37.8*

Metribuzin Lexone, Sencor H 21087-64-9 .006 4200 31*

Molinate Ordram H 2212-67-1 .003 – –

Napropamide Devrinol H 15299-99-7 .007 – –

Parathion several I 56-38-2 .010 – .013

Pebulate Tillam H 1114-71-2 .004 – –

Pendimethalin Prowl, Stomp H 40487-42-1 .022 – –

cis-Permethrin ambush, Pounce I 54774-45-7 .006 – –

Phorate Thimet, Rampart I 298-02-2 .011 – –

Prometon Pramitol H 1610-18-0 .015 4100 –

Propyzamide Kerb H 23950-58-5 .004 – –

Propachlor4 Ramrod H 1918-16-7 .010 490 –

Propanil Stampede H 709-98-8 .011 – –

Propargite Comite, Omite I 2312-35-8 .023 – –

 Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
Pesticide target analyte Trade or common name(s) Type of 

pesticide CAS registry No.

Laboratory 

reporting level 

(μg/L)

Drinking-water 

standard or 

guideline 

(μg/L)

Freshwater 

aquatic-life 

benchmark

(μg/L)

Gas Chromatography/Mass Spectrometry analytical data—Continued

Simazine Aquazine, Princep H 122-34-9 0.005 4 –

Tebuthiuron1 Spike H 34014-18-1 .016 3,500 –

Terbacil1,2 Sinbar H 5902-51-2 .034 390 –

Terbufos Counter I 13071-79-9 .017 30.9 –

Thiobencarb Bolero H 28249-77-6 .010 – –

Triallate5 Far-Go H 2303-17-5 .002 – –

Trifluralin Treflan, Trilin H 1582-09-8 .009 35 –

High-Performance Liquid Chromatography/Mass Spectrometry analytical data 

2,4-D Weedon-2,4,-DP H 94-75-7 0.038 70 34.0

2,4-D methyl ester many H 1928-38-7 .016 – 34.0

2,4-DB2 none H 94-82-6 .020 – 34.0

OIET2 none T 2163-68-0 .032 – –

3(4-Chlorophenyl)-1-

methyl urea 

none T 5352-88-5 .036 – –

3-Ketocarbofuran2 none T 16709-30-1 .02 – –

Acifluorfen Blazer, Tackle H 50594-66-6 .028 610 –

Aldicarb2 Temik I 116-06-3 .04 3 31

Aldicarb sulfone2 none T 1646-88-4 .018 2 31

Aldicarb sulfoxide2 none T 1646-87-3 .022 4 31

Atrazine1 Aatrexx, Atratol H 1912-24-9 .008 3 1.8

Bendiocarb Ficam I 22781-23-3 .020 – –

Benomyl2 Benlate F 17804-35-2 .022 – –

Bensulfuron-methyl2 Londax H 83055-99-6 .018 – –

Bentazon2 Adagio, Galaxy, Storm H 25057-89-0 .012 3,200 –

Bromacil2 Hyvar, Uragon H 314-40-9 .018 90 35.0

Bromoxynil Buctril, Bromanil, Torch H 1689-84-5 .028 – 35.0

Caffeine None S 58-08-2 .018 –

Carbaryl1 Sevin H 63-25-2 .018 4700 3.20

Carbofuran1 Furadan, Crisfuran H 1563-66-2 .016 40 21.8

3-Hydroxycarbofuran None T 16655-82-6 .008 – –

Chloramben, methyl ester2 Amiben H 7286-84-2 .024 – –

Chlorimuron-ethyl2 Classic H 90982-32-4 .032 – –

Chlorothalonil2 Bravo, Forturf F 1897-45-6 .035 55 3.18

Clopyralid Stinger, Lontrel H 1702-17-6 .024 – –

Cycloate2 Ro-Neet, Marathon H 1134-23-2 .014 – –

Dacthal monoacid None T 887-54-7 .028 – –

CIAT1,2 None T 6190-65-4 .028 – –

CAAT2,6 None T 3397-62-4 .022 – –

CEAT2 None T 1007-28-9 .08 – –

Dicamba Banvel, Marksman, Clarity H 1918-00-9 .036 4200 310*

Dichlorprop 2,4-DP, Weedon DP H 120-36-5 .028 – –

Dinoseb2 DNBP, Caldon, Dynamite H 88-85-7 .038 7 3.05*

Diphenamid Rideon, Dymid, Enide H 957-51-7 .010 4200 –

Diuron DCMU, Direx, Aguron H 330-54-1 .015 410 –

Table 4. Pesticide target analytes, laboratory reporting levels, drinking water standards or guidelines, and aquatic-life benchmarks—Continued

[If laboratory reporting level changed during the study, the most frequently used level is indicated. Pesticide target analyte: CIAT, 2-chloro-4-isopropylamino6-amino-s-triazine; CAAT, chlorodiamino-s-triazine; OIET, 2-hydroxy-4-isopropylamino-6-ethylamino-s-triazine; CEAT, 2-chloro-6-ethylamino-4-aminos-triazine; GC/MS, gas chromatography/mass spectrometry; HPLC/MS, high-performance liquid chromatography/mass spectrometry. Type of pesticide: F, 

fungicide; H, herbicide; I, insecticide; S, stimulant; T, transformation product. Drinking-water standards and guidelines: Maximum contaminant levels for 

drinking water from U.S. Environmental Protection Agency (2004a). Freshwater aquatic-life benchmark: From U.S. Environmental Protection Agency 

(2004b), unless otherwise footnoted. Abbreviations: CAS, Chemical Abstracts Service; μg/L, microgram per liter; –, no data or not available; *, interim values 

(Canadian Council of Resource and Environment Ministers, 1997)]

Methods 
Pesticide target analyte Trade or common name(s) Type of 

pesticide CAS registry No.

Laboratory 

reporting level 

(μg/L)

Drinking-water 

standard or 

guideline 

(μg/L)

Freshwater 

aquatic-life 

benchmark

(μg/L)

High-Performance Liquid Chromatography/Mass Spectrometry analytical data—Continued

Fenuron2 Beet-Kleen H 101-42-8 0.032 – –

Flumetsulam2 DE498, XRD 498 H 98967-40-9 .040 – –

Fluometuron Cotoran, Lanex, Cottonex H 2164-17-2 .016 490 –

Imazaquin2 Skepter 1.5L, Image 1.5LC H 81335-37-7 .036 – –

Imazethapyr2 Pursuit, Pursuit DG H 81335-77-5 .038 – –

Imidacloprid Admire, Gaucho, Merit I 138261-41-3 .020 – –

Linuron1 Lorox, Linex, Afalon H 330-55-2 .014 – –

MCPA Metaxon, Border Master H 94-74-6 .030 34 32.6*

MCPB2 Troptox, Can-Trol H 94-81-5 .010 – –

Metalaxyl Apron, Subdue, Ridomil F 57837-19-1 .012 – –

Methiocarb Draza, Mesurol I 2032-65-7 .010 – –

Methomyl2 Lannate,Nudrin, Lanox I 16752-77-5 .020 4200 –

Metsulfuron methyl2 Escort, Gropper, Ally H 74223-64-6 .025 – –

Neburon Granurex, Herbalt, Kloben H 555-37-3 .012 – –

Nicosulfuron2 Accent, Accent DF H 111991-09-4 .04 – –

Norflurazon2 Zorial, Evital, Solicam H 27314-13-2 .020 – –

Oryzalin2 Ryzelan, Surflan, Dirimal H 19044-88-3 .012 – –

Oxamyl2 Vydate: Thioxamyl I 23135-22-0 .030 200 –

Picloram7 Tordon, Amdon, Grazon H 1918-02-1 .020 500 329*

Propham Chem-Hoe, IPC, Premalox H 122-42-9 .030 4100 –

Propiconazole Tilt, Orbit, Wocosin F 60207-90-1 .010 – –

Propoxur Baygon, PHC, Suncide I 114-26-1 .008 43 –

Siduron Tupersan, Trey H 1982-49-6 .020 – –

Sulfometuron-methyl Oust, DPX-T5648 H 74222-97-2 .038 – –

Tebuthiuron1 Graslan, Spike, Perflan H 34014-18-1 .032 4500 –

Terbacil1,2 Sinbar, DPX-D732, Geonter H 5902-51-2 .016 490 –

Tribenuron methyl2,8 Express, DPX-L5300 H 101200-48-0 .0088 – –

Triclopyr Garlon, Curtail, Redeem H 55335-06-3 .026 – –

1Analyzed by GC/MS and HPLC/MS.

2Because recovery or variation in recovery was outside the acceptable range, compound is qualified with an E-code (estimated).

3Canadian water-quality guidelines for the protection of freshwater aquatic life (Canadian Council of Ministers of the Environment, 2003).

4U.S. Environmental Protection Agency lifetime-health advisory for a 70-kilogram adult (U.S. Environmental Protection Agency, 2004a).

5Great Lakes water-quality objective for protection of aquatic life, from the International Joint Commission (IJC) Canada and United States, 1978.

6U.S. Environmental Protection Agency risk-specific dose health advisory associated with a cancer risk of 10-5 (1 in 100,000) was calculated from riskspecific dose of 10-4 (RSD4) (U.S. Environmental Protection Agency, 2004a). 7U.S. Environmental Protection Agency risk-specific dose health advisory associated with a cancer risk of 10-5 (1 in 100,000), from USEPA Integrated Risk 

Information System (IRIS) data base (U.S. Environmental Protection Agency, 2005b). 8Tibenuron methyl was routinely reported by the laboratory as a null result because of problems with stability of calibration standards. The analyte was 

removed from the analytical method September 30, 2004. 

Table 4. Pesticide target analytes, laboratory reporting levels, drinking water standards or guidelines, and aquatic-life benchmarks—Continued

[If laboratory reporting level changed during the study, the most frequently used level is indicated. Pesticide target analyte: CIAT, 2-chloro-4-isopropylamino6-amino-s-triazine; CAAT, chlorodiamino-s-triazine; OIET, 2-hydroxy-4-isopropylamino-6-ethylamino-s-triazine; CEAT, 2-chloro-6-ethylamino-4-aminos-triazine; GC/MS, gas chromatography/mass spectrometry; HPLC/MS, high-performance liquid chromatography/mass spectrometry. Type of pesticide: F, 

fungicide; H, herbicide; I, insecticide; S, stimulant; T, transformation product. Drinking-water standards and guidelines: Maximum contaminant levels for 

drinking water from U.S. Environmental Protection Agency (2004a). Freshwater aquatic-life benchmark: From U.S. Environmental Protection Agency 

(2004b), unless otherwise footnoted. Abbreviations: CAS, Chemical Abstracts Service; μg/L, microgram per liter; –, no data or not available; *, interim values 

(Canadian Council of Resource and Environment Ministers, 1997)]

10 Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
Quality Assurance/Quality Control

About 15 percent of all samples submitted to the 

laboratories were quality-control samples, which included 

field blanks and equipment blanks to measure possible 

contamination and bias; replicate samples to measure 

variability; and field-matrix spike samples to measure recovery 

of analytes. All samples for pesticide analysis were spiked 

with surrogate analytes prior to extraction, to monitor accuracy 

and precision of the analytical procedures. Wilde and others 

(1999b) define these quality-control samples. Additionally, 

laboratory quality-control samples were routinely analyzed 

as part of the laboratory quality-assurance plan described by 

Maloney (2005).

Field- and equipment-blank samples for pesticide 

analysis were free of contamination, except for detection of 

EPTC in one field blank at a concentration of 0.043 μg/L 

and detection of caffeine in one field blank at an estimated 

concentration of 0.00043 μg/L. No adjustments were made in 

the data set or data analysis on the basis of these results. 

Precision data were obtained for two sets of replicate 

pesticide samples (table 16, at back of report). Differences in 

concentration between replicates ranged from 0 to 71 percent, 

as measured by relative percentage of difference (94 percent 

of the differences were ≤5 percent). Percentage of relative 

differences for atrazine ranged from 5.1 to 71 percent. The 

relative percentage of difference was 5.1 for one set of 

replicates using the GS/MS techniques; the relative percentage 

of difference was 62 and 71 for two other sets of replicates 

analyzed using the HPLC/MS method. The GC/MS technique 

is the preferred method of analysis and is the value used for 

all data analysis. No modifications were made to the data set 

based on these results. Mean recovery percentages of GC/MS 

target analytes in field-matrix spike samples ranged from 

33 to 213 percent, with a median recovery of 97.5 percent 

(table 17, at back of report). Mean recovery percentages of 

HPLC/MS target analytes in field-matrix spike samples ranged 

from 34 to 150 percent (table 17), with a median recovery 

of 86.5 percent. Although recoveries of HPLC/MS target 

analytes generally were lower than recoveries of GC/MS target 

analytes, recoveries generally are large enough and consistent 

enough that the data are acceptable and useful for analysis. 

However, because of lower recoveries and greater variability, 

the probability of false negatives is greater for HPLC/MS 

target analytes than for GC/MS and the effective detection 

level generally is larger. No modifications were made to the 

environmental data set, but recovery percentages for these 

analytes need to be considered when interpreting the data. 

Seven pesticides were analyzed by GC/MS and 

HPLC/MS methods. Three pesticides (atrazine, CIAT, and 

tebuthiuron) were reported only by the “preferred” method 

(GC/MS). The remaining four pesticides (carbaryl, carbofuran, 

linuron, and terbacil) were reported with both methods. 

The NWQL uses a hierarchical procedure in selecting the 

“preferred” method for these compounds (Mark Sandstrom, 

USGS National Water Quality Laboratory, written commun., 

2004). For the current study, all pesticides were included in 

the analysis of quality-control samples to determine intralaboratory method precision and accuracy. Precision between 

analytical methods is summarized in table 18 (at back of 

report). Generally, precision between the two analytical 

methods is good. Comparison between the two methods can 

be summarized into four categories: (1) both methods reported 

no detections, (2) both methods reported a detection, (3) one 

method reported no detection and the other method reported 

a detection that was either near or less than the reporting 

level of the other method, and (4) one method reported no 

detection and the other method reported a detection that 

was larger than the reporting level of the other method. For 

example, case 3 is illustrated by a detection of CIAT E0.008 

by GC/MS and the HPLC/MS method reporting of CIAT as 

less than 0.028. Case 4 only occurred with analysis of terbacil, 

and an example is the detection by GC/MS of E0.026 and the 

HPLC/MS method reporting of less than 0.010. One method 

reported a detection and the other did not a total of 13 percent 

of the time, 11 percent of the time as a case 3 difference 

and 2 percent of the time as a case 4 difference. This likely 

indicates the preference for the GC/MS method for the 

analysis of terbacil.

Methods 11
Occurrence, Distribution, and 

Transport of Pesticides

All samples were analyzed for concentrations of 

pesticides, major ions, iron, manganese, and nutrients. 

Summaries of results for inorganic constituents and pesticides 

are presented. Estimates of pesticide use are discussed and 

compared in relation to detected and non-detected pesticides, 

and a comparison is made between pesticides detected in this 

study and pesticides detected in earlier studies. 

Field Measurements and Inorganic Constituents

Water temperature, pH, DO concentrations, specific 

conductance and concentrations of major ions, trace elements, 

and nutrients data were measured at all sampling sites where 

pesticide data were collected (table 5). Water-temperature 

measurements are subject to the water-temperature criteria for 

core and non-core designated use by fish in the Washington 

2003 water-quality standards (State of Washington, 2003). 

(The term “non-core” to refers to “salmon and trout spawning, 

non-core rearing, and migration” designated use and “core” 

refers to the “salmon and trout spawning, core rearing, and 

migration” designated use.) The criteria specify that water 

temperature be measured by the 7-day average of daily 

maximum temperatures (7DADMax; State of Washington, 

2003), but extended deployment of temperature sensors and 

calculation of a 7-day average of maximum temperatures were 

beyond the scope of this study. Water temperatures measured 

during this study are only an indication of instantaneous 

temperatures at time of sampling and indicate that the 

temperature criterion may have been exceeded. 

Measured water temperature was greater than the State 

of Washington criterion of 16oC for core rearing, salmon 

and trout spawning, and migration in 18 instances. These 

exceedances occurred 7 times at Red Rock Coulee, 5 times 

at Crab Creek, 4 times at Lind Coulee, and 2 times at Sand 

Hollow. In 11 of these 18 instances, measured temperature 

also was greater than the criterion of 17.5oC for non-core 

rearing, salmon and trout spawning, migration, and salmon 

and trout rearing and migration only. 

The State of Washington aquatic-life criteria for DO 

are listed as 1-day minimum. The criterion of 9.5 mg/L for 

salmon and trout spawning, core rearing, and migration was 

exceeded eight times at three sites during this study from 

June to early October: two times at Sand Hollow, three times 

at Red Rock Coulee, and three times at Crab Creek. State of 

Washington aquatic-life criterion for pH of 8.5 for fresh water 

was exceeded 12 times: 6 times at Red Rock Coulee, 3 times 

at Sand Hollow, 2 times at Lind Coulee, and 1 time at Crab 

Creek.

Table 5. Summary of field measurements and concentrations of inorganic constituents in surface-water samples collected 

from the four irrigation return-flow drainage basins, Columbia Basin Project, July 2002 through October 2004.

[Dissolved solids, residue on evaporation, dried at 180 degrees Celsius. Abbreviations: ft3/s, cubic foot per second; oC; degrees 

Celsius; mS/cm, microsiemens per centimeter; mg/L, milligram per liter; CaCO3, calcium carbonate; mg/L, microgram per liter; E, estimated (below laboratory reporting level); <, less than]

Constituent or property Number of 

samples

Value

Minimum Maximum Median

Crab Creek

Field measurements 

 Streamflow (ft3/s) 12 129 331 214.5

 Temperature (oC) 12 4.9 22.4 15.05

 pH (standard units) 12 8.1 8.6 8.4

 Specific conductance (μS/cm) 12 492 885 540

 Dissolved oxygen (mg/L) 12 8.6 12.6 10.45

Major ions 

 Calcium (mg/L) 12 33.1 52.6 37.95

 Magnesium (mg/L) 12 20.4 32.6 21.45

 Sodium, (mg/L) 12 38.2 84.9 46.4

 Potassium, (mg/L) 12 5.97 12.1 7.22

 Chloride (mg/L) 12 12.8 29.6 14.9

 Sulfate (mg/L) 12 46.8 100 51.95

 Fluoride (mg/L) 12 .48 .83 .50

 Silica (mg/L) 12 15.6 35.0 22.55

 Alkalinity (mg/L as CaCO3) 8 182 307 209

 Dissolved solids (mg/L) 12 305 560 333.5

12 Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
Table 5. Summary of field measurements and concentrations of inorganic constituents in surface-water samples collected 

from the four irrigation return-flow drainage basins, Columbia Basin Project, July 2002 through October 2004.—Continued

[Dissolved solids, residue on evaporation, dried at 180 degrees Celsius. Abbreviations: ft3/s, cubic foot per second; oC; degrees 

Celsius; mS/cm, microsiemens per centimeter; mg/L, milligram per liter; CaCO3, calcium carbonate; mg/L, microgram per liter; E, estimated (below laboratory reporting level); <, less than]

Constituent or property Number of 

samples

Value

Minimum Maximum Median

Crab Creek—Continued

Trace elements 

 Iron (μg/L) 12 5.0 27 8.5

 Manganese (μg/L) 12 2.3 8.3 3.6

Nutrients 

 Ammonia (mg/L as N) 12 <.010 .03 .010

 Ammonia plus organic nitrogen 

(mg/L as N) 

12 .04 .88 .355

 Nitrite plus nitrate (mg/L as N) 12 1.05 2.5 1.56

 Phosphorus (mg/L as P) 12 .024 .099 .034

 Orthophosphate (mg/L as P) 12 <.003 .071 .016

Lind Coulee

Field measurements 

 Streamflow (ft3/s) 12 58 355 255

 Temperature (oC) 12 8.1 19.8 14.85

 pH (standard units) 12 8.1 8.8 8.4

 Specific conductance (μS/cm) 12 203 573 292

 Dissolved oxygen (mg/L) 11 10.6 14.5 11.4

Major ions 

 Calcium (mg/L) 12 22.5 46.9 28.45

 Magnesium (mg/L) 12 6.56 19.6 9.69

 Sodium, (mg/L) 12 9.36 51.8 16.4

 Potassium, (mg/L) 12 1.62 6.18 2.575

 Chloride (mg/L) 12 2.95 15.7 5.4

 Sulfate (mg/L) 12 15.0 65.9 22.25

 Fluoride (mg/L) 12 <.2 .7 .29

 Silica (mg/L) 12 9.49 42.6 13.4

 Alkalinity (mg/L as CaCO3) 8 81 204 105.5

 Dissolved solids (mg/L) 12 124 391 186

Trace elements 

Iron (μg/L) 12 <10 16 9.0

Manganese (μg/L) 12 5.90 21.5 14.2

Nutrients 

Ammonia (mg/L as N) 12 <.01 .02 .02

Ammonia plus organic (mg/L as N) 12 .15 .28 .205

Nitrite plus nitrate (mg/L as N) 12 .56 5.02 1.735

Phosphorus (mg/L as P) 12 .027 .079 .050

Orthophosphate (mg/L as P) 12 .017 .057 .030

Red Rock Coulee

Field measurements 

Streamflow (ft3/s) 12 43 114 71.5

Temperature (oC) 12 4.6 23.1 16.55

pH (standard units) 12 8.2 8.9 8.55

Specific conductance (μS/cm) 12 374 660 420

Dissolved oxygen (mg/L) 12 8.3 12.7 9.85

Occurrence, Distribution, and Transport of Pesticides 13
Table 5. Summary of field measurements and concentrations of inorganic constituents in surface-water samples collected 

from the four irrigation return-flow drainage basins, Columbia Basin Project, July 2002 through October 2004.—Continued

[Dissolved solids, residue on evaporation, dried at 180 degrees Celsius. Abbreviations: ft3/s, cubic foot per second; oC; degrees 

Celsius; mS/cm, microsiemens per centimeter; mg/L, milligram per liter; CaCO3, calcium carbonate; mg/L, microgram per liter; E, estimated (below laboratory reporting level); <, less than]

Constituent or property Number of 

samples

Value

Minimum Maximum Median

Red Rock Coulee—Continued

Major ions

Calcium (mg/L) 12 21.3 53.8 37.05

Magnesium (mg/L) 12 16.6 29.8 18.45

Sodium, (mg/L) 12 17.8 38.6 22.1

Potassium, (mg/L) 12 2.02 3.55 2.705

Chloride (mg/L) 12 9.03 19.3 11.0

Sulfate (mg/L) 12 31.5 63.9 36.4

Fluoride (mg/L) 12 .3 .6 .4

Silica (mg/L) 12 19.3 40.8 23.5

Alkalinity (mg/L as CaCO3) 8 137 224 155.5

Dissolved solids (mg/L) 12 230 411 266

Trace elements

Iron (μg/L) 12 <6.0 6.0 5.0

Manganese (μg/L) 12 <2.0 3.4 1.8

Nutrients

Ammonia (mg/L as N) 12 <.01 .05 .02

Ammonia plus organic (mg/L as N) 12 .20 .36 .285

Nitrite plus nitrate (mg/L as N) 12 1.72 5.5 2.195

Phosphorus (mg/L as P) 12 .019 .036 .023

Orthophosphate (mg/L as P) 12 <.003 .016 .006

Sand Hollow

Field measurements 

Streamflow (ft3/s) 12 23 141 92

Temperature (oC) 12 8.1 22.0 13.7

pH (standard units) 12 8.1 8.6 8.45

Specific conductance (μS/cm) 12 141 719 336.5

Dissolved oxygen (mg/L) 12 8.4 12.0 10.55

Major ions

Calcium (mg/L) 12 27.6 76.3 35.8

Magnesium (mg/L) 12 9.79 36.1 14.1

Sodium, (mg/L) 12 9.0 29.1 12.65

Potassium, (mg/L) 12 1.18 2.51 1.57

Chloride (mg/L) 12 5.04 27.9 9.32

Sulfate (mg/L) 12 16.9 66.1 25.05

Fluoride (mg/L) 12 .17 .50 .23

Silica (mg/L) 12 9.8 43.9 17.35

Alkalinity (mg/L as CaCO3) 8 89 106 124.5

Dissolved solids (mg/L) 12 167 491 213.5

Trace elements

Iron (μg/L) 12 E4 <10 <6

Manganese (μg/L) 12 E.70 E2.5 1.15

Nutrients

Ammonia (mg/L as N) 12 <.01 .07 .02

Ammonia plus organic (mg/L as N) 12 .06 .45 .235

Nitrite plus nitrate (mg/L as N) 12 2.46 17.9 4.515

Phosphorus (mg/L as P) 12 <.010 .052 .023

Orthophosphate (mg/L as P) 12 <.003 .027 .006

14 Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
Dissolved-solids concentrations varied spatially and 

seasonally. Dissolved-solids concentrations increased 

during the non-irrigation season and concentrations between 

sites generally increased as water moved through the CBP, 

from Lind Coulee down to Crab Creek (fig. 2). Average 

concentration of dissolved solids at Lind Coulee during this 

study was 211 mg/L, increasing to an average of 379 mg/L 

in samples from Crab Creek. Average concentrations from 

intermediate sites at Sand Hollow and Red Rock Coulee 

were 250 and 296 mg/L, respectively. Dissolved-solids 

concentrations increased during the non-irrigation season, 

reflecting a larger ground-water contribution to base flow. 

Average dissolved-solids concentration at all sites was 

249 mg/L during irrigation season and 454 mg/L during 

non-irrigation season. 

The predominant major ions from all sites generally 

were from calcium, magnesium, and bicarbonate (fig. 3). 

Although some overlap was present between the majorion characteristics of the four sites, each site generally 

was grouped differently on a major-ion diagram and all 

were uniquely different from the irrigation source water, 

represented by the Columbia River. Additionally, samples 

from Sand Hollow and Lind Coulee during the nonirrigation season were clearly differentiated from samples 

0

50

100

150

200

250

300

350

400

450

500

550

600

2002 2003

SAMPLE DATE

2004

J A S O N D J F M A M J J A S O N D J F M A M J J A S O

DISSOLVED-SOLIDS CONCENTRATION, IN MILLIGRAMS PER LITER

12464606 SAND HOLLOW AT S RD

12464607 SAND HOLLOW

12471400 LIND COULEE

12472520 RED ROCK COULEE

12472600 CRAB CREEK

Figure 2. Concentrations of dissolved solids in the four irrigation return-flow drainage basins, Columbia Basin 

Project, Washington, July 2002 to October 2004.

Site 12464606 was sampled only once in July 2002, and all other samples for Sand Hollow drainage basin were from 

site 12464607.

Occurrence, Distribution, and Transport of Pesticides 15
Figure 3. Percentage of major ions in surface water from the Columbia River and from the four irrigation return-flow drainage basins, 

Columbia Basin Project, Washington.

waAE700_01.fig03

EXPLANATION

CRAB CREEK

LIND COULEE

RED ROCK COULEE

SAND HOLLOW AT S RD

SAND HOLLOW 

COLUMBIA RIVER AT NORTHPORT

COLUMBIA RIVER AT VERNITA BRIDGE

Calcium (Ca) Chloride (Cl), Fluoride (F), Nitrate plus Nitrite (NO3 plus NO2)

PERCENTAGE OF TOTAL MILLIEQUIVALENTS PER LITER

80 60 40 20 20 40 60 80

Sulfate (SO4) plus Chloride (Cl)

Calcium (Ca) plus Magnesium (Mg)

Sodium (Na) plus Potasium (K)

Sulfate (SO4)

Carbonate (CO3) plus Bicarbonate (HCO3)

Magnesium (Mg)

80 60 40 20

80 60 40 20

20 40 60 80

20 40 60 80

20 40 60 80

20 40 60 80

80 60 40 20

80 60 40 20

Na plus K HCO3 plus CO3 Ca

CATIONS ANIONS

16  Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
collected during the irrigation season. Anions for all samples 

were predominantly from bicarbonate and cations were 

predominantly from calcium. During the irrigation season, 

calcium was the predominant cation for both sites. However, 

during the non-irrigation, concentrations of chloride and 

nitrate increased in samples from Sand Hollow and reflect a 

shift in the percentage of chloride, fluoride, and nitrite plus 

nitrate. Similarly, the percentage of sulfate plus chloride for 

Sand Hollow also increased during the non-irrigation season. 

Samples from Lind Coulee during the non-irrigation season 

also are readily differentiated from irrigation season samples 

because of an increase in sodium plus potassium during the 

non-irrigation season. However, the percentage of nitrite plus 

nitrate for samples from Sand Hollow nearly doubled during 

the non-irrigation season and the percentages of sulfate and 

chloride increased. Similarly, samples from Lind Coulee 

during the non-irrigation season were clearly differentiated 

from samples collected during the irrigation season because of 

a shift in the cation percentages, with less calcium and more 

sodium. 

Generally, the ratio of dissolved solids divided by 

specific conductance is a well-defined relation (Hem, 1985) 

for many rivers and streams. Because no long-term data for 

irrigation source water (from Lake Roosevelt or Banks Lake) 

are publicly available, historical information for the Columbia 

River above Lake Roosevelt (at Northport, Wash.) and 

downstream of Lake Roosevelt (near Priest Rapids Dam) can 

be used to approximate the quality of irrigation source water. 

The median ratio of dissolved solids to specific conductance 

ranges from 0.58 to 0.64 for the sites in the four irrigation 

return-flow basins and the Columbia River sites (table 6). 

However, the relation between silica and calcium provides 

an even better “signature” of major ions in the irrigation 

return flow (table 17). The long-term median silica-calcium 

ratios for the sites at Columbia River at Northport and Priest 

Rapids Dam are 0.23 and 0.26, respectively. As the irrigation 

water flows through the CBP, the ratio in samples increases, 

reflected by the higher ratios. Although ranges of the ratio 

overlap, each individual sample ratio was uniquely different 

from the others during that sampling period. Major-ion, 

trace-element, and nutrient concentrations generally were 

within State and Federal criteria. Concentrations of nitrite plus 

nitrate in two samples collected from Sand Hollow during 

the non-irrigation season exceeded the U.S. Environmental 

Protection Agency (USEPA) Maximum Contaminant Level 

(MCL) for drinking water of 10 mg/L.

Table 6. Summary of calculated major ion ratios in surface-water samples collected from the four irrigation return-flow drainage basins, Columbia Basin 

Project, and the Columbia River, Washington, July 2002 to October 2004.

[Columbia River data are from 1960–2000. The Sand Hollow sites were combined for analysis. Abbreviations: SiO2/Ca: ratio of silica and calcium; Dissolved 

solids/SC, ratio of dissolved solids and specific conductance in microsiemens per centimeter at 25 degrees Celsius]

Sampling site

SiO2/Ca Dissolved solids/SC

Minimum Maximum Median Minimum Maximum Median

Crab Creek 0.44 0.69 0.59 0.60 0.66 0.62

Lind Coulee .40 .91 .70 .59 .77 .64

Red Rock Coulee .53 .76 .64 .57 .68 .62

Sand Hollow .36 .58 .49 .57 .70 .62

Columbia River at Northport .15 .67 .23 .33 .89 .58

Columbia River at Vernita Bridge, near Priest 

Rapids Dam

.19 .57 .26 .46 .80 .58

Occurrence, Distribution, and Transport of Pesticides 17
Occurrence and Distribution of Pesticides

Forty-two pesticides and five metabolites were detected 

in samples from the four irrigation return-flow drainage 

basins in the CBP from July 2002 to October 2004 (table 7). 

The greatest number of compounds, 37, was detected at Sand 

Hollow, followed by 33 at Lind Coulee, 30 at Red Rock 

Coulee, and 28 at Crab Creek. Herbicides were the most 

frequently detected pesticides, followed by insecticides, 

metabolites, and fungicides. Atrazine, bentazon, diuron, and 

2,4-D were the most frequently detected herbicides, and 

chlorpyrifos and azinphos-methyl were the most frequently 

detected insecticides. Of the five metabolites detected, four 

were degradation products of triazine herbicides and one was 

the degradation product of DCPA (dacthal monoacid). CIAT 

(commonly referred to as deethylatrazine), CEAT, CAAT, and 

OIET were the most frequently detected metabolites. 

Pesticide concentrations in samples from the CBP 

did not exceed any drinking-water standards or guidelines, 

but concentrations of three insecticides and one herbicide 

did exceed USEPA or Canadian freshwater aquatic-life 

benchmarks (table 8). Concentrations of the insecticide 

azinphos-methyl exceeded USEPA recommended chronic 

water-quality criterion for the protection of freshwater 

aquatic life of 0.01 μg/L at least once at each of the four sites. 

Concentrations in samples from Sand Hollow also exceeded 

USEPA recommended freshwater chronic criterion for the 

protection of freshwater aquatic life for chlorpyrifos (0.041), 

and Canadian guidelines for the protection of freshwater 

aquatic life for lindane and dinoseb (0.01, and 0.05 μg/L, 

respectively). Water-quality aquatic-life benchmarks generally 

were exceeded in June and July, during the middle of the 

irrigation season, except the criterion for dinoseb, which 

was exceeded in one sample during non-irrigation season in 

February 2003, at a concentration of 0.14 μg/L.

Pesticides can be toxic to aquatic life in streams, and the 

ECOTOX (ECOTOXicology) database (U.S. Environmental 

Protection Agency, 2005a) provides single-chemical toxicity 

information for aquatic freshwater life (table 9). Data retrieved 

from ECOTOX contained a substantial number of apparent 

duplicate entries (Munn and Gilliom, 2001, and Patrick 

Moran, U.S. Geological Survey, oral commun., November 

2005), and these were removed. Because of the complex 

mixtures and seasonal patterns of pesticides, it is difficult to 

link chemical conditions in streams to effects on aquatic biota 

(Munn and Gilliom, 2001). The endpoint concentration for 

comparison of aquatic toxicity to fish used in this study is 

median lethal concentrations (LC50), which is a statistically 

estimated concentration that is expected to be lethal to 50 

percent of a group of organisms tested. LC50 for all pesticides 

analyzed during this study are far greater than concentrations 

detected in samples collected from irrigation-return flows 

during this study. However, data are not available for all 

pesticides, and additive or possible synergistic effects of 

multiple chemicals are not accounted for by this measure of 

aquatic toxicity. The most toxic insecticides analyzed during 

this study are azinphos-methyl, chlorpyrifos, lindane, and 

malathion, with LC50 values that range from 1.3 to 2.4 μg/L. 

Concentrations of pesticides analyzed during this study are far 

less than these LC50 concentrations. The most toxic herbicides 

were trifluralin, pendimethalin, ethalfluvalin, and diacamba, 

with LC50 values that range from 8.4 to 138 μg/L. LC50

values for specific pesticides are a factor of 110 greater than 

maximum concentrations of pesticides detected in samples 

from the four drainage basins during this study. Munn and 

Gilliom (2001) suggest use of a pesticide toxicity index (PTI), 

which is the sum of toxicity quotients for each compound 

measured in a stream. This approach may be useful in relating 

pesticide toxicity between drainage basins and over time, but it 

is beyond the scope of this study.

Total number of pesticide detections and total 

concentrations of those detections show a distinct seasonal 

pattern at the four sites, with the highest number of detections 

and total concentrations during the middle of the irrigation 

season, April to October (fig. 4). Samples from Sand Hollow 

basin generally had the greatest number of pesticides per 

sample, ranging from about 8 pesticides detected in a 

sample during the end of irrigation season to more than 20 

pesticides detected in samples collected during the middle of 

irrigation season. Samples from Lind Coulee basin had the 

fewest number of pesticides per sample, ranging from 4 to 18 

pesticides with the highest number also occurring during the 

middle of irrigation season. 

The pattern for total pesticides concentrations for Sand 

Hollow basin was slightly different than those for the other 

three basins, with a substantially higher total concentration in 

the sample collected during the 2003 non-irrigation season. 

This may be an aberration that occurred only in 2003, but 

it likely is due to the increase in concentrations of atrazine, 

CIAT, bentazon, and bromacil during base-flow conditions in 

the non-irrigation season. Total pesticide concentrations in the 

sample collected during the 2004 non-irrigation season were 

higher than those in late-irrigation season samples, but it is not 

clear why the 2003 non-irrigation sample was substantially 

higher. The increase in concentration of these compounds 

during base flow indicates that ground water contributes a 

substantial part of the pesticide load for these compounds. 

Further study of pesticides in the irrigation return-flow 

drainage basins during the non-irrigation season would be 

helpful.

18  Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
Table 7. Maximum concentrations and number of pesticide detections in the four irrigation return-flow drainage basins, Columbia Basin Project, 

Washington, July 2002 to October 2004.

[All concentrations are in micrograms per liter. Concentrations in bold represent values that exceed freshwater aquatic-life benchmarks (see table 4). Pesticide:

CIAT, 2-chloro-4-isopropylamino-6-amino-s-triazine; CEAT, 2-chloro-6-ethylamino-4-amino-s-tirazine; CAAT, chlorodiamino-s-triazine; OIET, 2-hydroxy4-isopropylamino-t-ethylamino-s-triazine. Type of pesticide: F, fungicide; H, herbicide; I, insecticide; S, stimulant; T, transformation product. Number of 

detections: All, sum of all detections at all surface-water sites. Abbreviations: LRL, laboratory reporting level; SH, Sand Hollow; LCWA, Lind Coulee; 

CRCR, Crab Creek; RRCU, Red Rock Coulee; M, presence of material verified but not quantified; E, because recovery or variation in recovery was outside the 

acceptable range, compound is qualified with an E-code (estimated) or concentration reported is less than laboratory reporting level and is qualified as estimated; 

–, not detected]

Pesticide Type of 

pesticide LRL

Maximum concentration Number of detections

All

SH LCWA CRCR RRCU SH LCWA CRCR RRCU

Atrazine1 H 0.007 0.029 0.012 0.026 0.032 11 10 12 12 45

CIAT1 T .006 E.036 E.009 E.019 E.015 11 9 12 12 44

Bentazon H .012 E.25 E.01 E.04 E.07 12 6 12 11 41

Diuron H .014 E.22 .26 .10 .11 10 10 10 10 40

2,4-D H .038 .23 .44 .36 .77 10 8 11 10 39

Simazine H .005 .213 .024 .017 .022 7 1 9 10 27

Terbacil1 H .034 E1.01 – E.061 E.075 12 0 6 7 25

DCPA H .003 .011 .044 .05 .169 4 7 6 7 24

EPTC H .004 .085 .12 .075 .1 4 4 7 8 23

Bromacil H .018 E.12 E.13 E.01 E.03 8 5 2 5 20

Metolachlor H .006 E.008 .134 E.010 E.011 4 7 4 5 20

Terbacil2 H .016 E1.35 – E.031 E.090 10 0 3 5 18

Metribuzin H .006 .052 .016 E.005 .008 7 4 1 4 16

Alachlor H .005 .012 – .017 .013 6 0 3 4 13

2,4-D methyl ester H .016 .013 .017 .041 E.080 2 1 4 4 13

Chlorpyrifos I .005 .053 .006 .011 .027 5 2 3 3 13

Pendimethalin H .022 .388 .033 – – 7 5 0 0 12

Azinphos-methyl I .05 E.034 E.026 E.019 E.018 4 3 2 2 11

Dicamba H .036 E.03 E.19 E.06 E.13 2 3 3 3 11

Dinoseb H .038 .14 – – – 10 0 0 0 10

CEAT T .08 M – E.01 E.01 1 0 2 4 7

CAAT T .040 E.01 E.01 E.01 E.01 3 2 1 1 7

OIET T .032 E.007 E.006 E.007 E.006 2 2 2 1 7

Carbaryl1 I .041 E.070 – E.009 – 4 0 2 0 6

Linuron1 H .035 E.007 E.013 E.013 E.014 1 2 1 1 5

Benomyl F .022 – .082 E.006 E.017 0 1 1 2 4

Caffeine S .018 .0331 E.0052 – E.0089 2 1 0 1 4

Diazinon I .005 .007 – .008 .03 1 0 1 2 4

Diphenamid H .010 E.02 – E.01 E.03 1 0 1 2 4

Carbaryl2 I .018 E.01 – – – 3 0 0 0 3

Bromoxynil H .028 E.01 M – – 2 1 0 0 3

Malathion I .027 E.015 E.017 – .03 1 1 0 1 3

Metalaxyl F .012 E.01 .04 – – 1 2 0 0 3

Methomyl I .020 E.016 E.011 – – 1 2 0 0 3

Norflurazon H .020 E.01 – – M 1 0 0 2 3

Trifluralin H .009 – E.004 – – 0 2 0 0 3

Linuron2 H .014 E.01 – – E.01 1 0 0 1 2

2,4-DB H .020 – E.06 – – 0 2 0 0 2

Dacthal monoacid T .028 – – .02 .02 0 0 1 1 2

Ethalfluralin H .009 – E.009 – – 0 2 0 0 2

Ethoprophos I .005 .016 – – .009 1 0 0 1 2

MCPA H .030 E.03 M – – 1 1 0 0 2

Prometon H .010 M – – E.01 1 0 0 1 2

Chlorothalonil F 0.035 – E0.06 – – 0 1 0 0 1

Occurrence, Distribution, and Transport of Pesticides 19
Table 7. Maximum concentrations and number of pesticide detections in the four irrigation return-flow drainage basins, Columbia Basin Project, 

Washington, July 2002 to October 2004.—Continued

[All concentrations are in micrograms per liter. Concentrations in bold represent values that exceed freshwater aquatic-life benchmarks (see table 4). Pesticide:

CIAT, 2-chloro-4-isopropylamino-6-amino-s-triazine; CEAT, 2-chloro-6-ethylamino-4-amino-s-tirazine; CAAT, chlorodiamino-s-triazine; OIET, 2-hydroxy4-isopropylamino-t-ethylamino-s-triazine. Type of pesticide: F, fungicide; H, herbicide; I, insecticide; S, stimulant; T, transformation product. Number of 

detections: All, sum of all detections at all surface-water sites. Abbreviations: LRL, laboratory reporting level; SH, Sand Hollow; LCWA, Lind Coulee; 

CRCR, Crab Creek; RRCU, Red Rock Coulee; M, presence of material verified but not quantified; E, because recovery or variation in recovery was outside the 

acceptable range, compound is qualified with an E-code (estimated) or concentration reported is less than laboratory reporting level and is qualified as estimated; 

–, not detected]

Pesticide Type of 

pesticide LRL

Maximum concentration Number of detections

All

SH LCWA CRCR RRCU SH LCWA CRCR RRCU

Clopyralid H .024 – – E0.01 – 0 0 1 0 1

Lindane I .004 0.018 – – – 1 0 0 0 1

Nicosulfuron H .04 – – E.01 – 0 0 1 0 1

Oxamyl I .030 – .03 – – 0 1 0 0 1

Propiconazole F .010 – E.01 – – 0 1 0 0 1

Triallate H .006 – .004 – – 0 1 0 0 1

Triclopyr I .026 E.01 – – – 1 0 0 0 1

Number of samples analyzed 12 12 12 12 48

1Analysis by gas chromatography/mass spectrometry (GC/MS).

2Analysis by high-performance liquid chromatography/mass spectrometry (HPLC/MS).

Table 8. Summary of pesticide concentrations in the four irrigation return-flow drainage basins, Columbia Basin Project, Washington, July 2002 to 

October 2004.

[All concentrations are in micrograms per liter. Concentrations of pesticides in bold represent values that exceed freshwater aquatic-life benchmarks (see 

table 4). Pesticide: CIAT, 2-chloro-4-isopropylamino-6-amino-s-triazine; CAAT, chlorodiamino-s-triazine; OIET, 2-hydroxy-4-isoprobylamino-6-ethylamino-striazine; CEAT, 2-chloro-6-ethylamino-4-amino-s-triazine. Type of pesticide: F, fungicide; H, herbicide; I, insecticide; S, stimulant; T, transformation product. 

Drinking-water standards: Maximum contaminant levels for drinking water from U.S. Environmental Protection Agency (2004a). Freshwater aquatic-life 

benchmarks: Standards from U.S. Environmental Protection Agency (2004b), unless otherwise footnoted. Abbreviations: LRL, laboratory reporting limit; M, 

presence of material verified, but not quantified; n, number of samples; E, because recovery or variation in recovery was outside the acceptable range, compound 

is qualified with an E-code (estimated) or concentration reported is less than laboratory reporting level and is qualified as estimated; <, less than; –, no data or 

not available; *, interim values (Canadian Council of Resources and Environment Ministers, 1997)]

Pesticide Type of 

pesticide LRL Median Maximum

Percentage 

of 

detections

(n=12)

Number of 

detections 

that exceed 

aquatic-life 

benchmarks

Number of 

detections 

that exceed 

drinking 

water 

standards

Crab Creek

CIAT T 0.006 E0.011 E0.019 100 – –

Atrazine H .007 .018 .026 100 0 0

Bentazon H .012 E.02 E.04 100 – –

2,4-D H .038 .06 .36 92 0 –

Diuron H .014 .02 .1 83 – –

Simazine H .005 .007 .017 75 – 0

EPTC H .004 E.002 .075 58 – –

DCPA H .003 <.003 .05 50 – 0

Terbacil1 H .034 <.025 E.061 50 – 0

2,4-D methyl ester H .016 <.009 .041 50 0 –

Metolachlor H .006 <.013 E.010 50 0 0

Alachlor H .006 <.004 .017 25 – 0

Chlorpyrifos I .005 <.005 .011 25 0 0

Dicamba H .036 <.01 E.06 25 0 0

Terbacil2 H .016 <.010 E.031 25 – 0

20 Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
Pesticide Type of 

pesticide LRL Median Maximum

Percentage 

of 

detections

(n=12)

Number of 

detections 

that exceed 

aquatic-life 

benchmarks

Number of 

detections 

that exceed 

drinking 

water 

standards

Crab Creek—Continued

CEAT1 T 0.08 <0.04 E0.01 17 – –

OIET T .032 <.008 E.007 17 – –

Azinphos-methyl I .05 <.050 E.019 17 1 –

Bromacil H .018 <.03 E.01 17 0 –

Carbaryl1 I .041 <.041 E.009 17 0 –

Benomyl H .022 <.004 E.006 8 – –

Chlorodiamino-s-triazine T .040 <.01 E.01 8 – –

Clopyralid H .024 <.01 E.01 8 – –

Dacthal monoacid T .028 <.01 .02 8 – –

Diazinon I .005 <.005 .008 8 0 0

Diphenamid H .010 <.03 E.01 8 – –

Linuron1 H .035 <.035 E.013 8 – –

Metribuzin H .006 <.006 E.005 8 0 0

Nicosulfuron H .04 <.01 E.01 8 – –

Lind Coulee

Atrazine H 0.007 0.010 0.012 83 0 0

Diuron H .014 .02 .26 83 – 0

CIAT T .006 E.004 E.009 75 – –

2,4-D H .038 E.02 .44 67 0 0

DCPA H .003 .004 .044 58 – 0

Metolachlor H .006 E.005 .134 58 0 0

Bentazon H .012 <.01 E.01 50 – 0

Bromacil H .018 <.03 E.13 42 0 0

Pendimethalin H .022 <.022 .033 42 – –

EPTC H .004 <.004 .12 33 – –

Metribuzin H .006 <.006 .016 33 0 0

Azinphos-methyl I .05 <.050 E.026 25 2 –

Dicamba H .036 <.01 E.19 25 0 0

2,4-DB H .020 <.02 E.06 17 0 –

OIET T .032 <.008 E.006 17 – –

Chlorodiamino-s-triazine T .040 <.01 E.01 17 – –

Chlorpyrifos I .005 <.005 .006 17 0 0

Ethalfluralin H .009 <.009 E.009 17 – –

Linuron1 H .035 <.035 E.013 17 0 –

Metalaxyl F .012 <.02 .04 17 – –

Methomyl I .020 <.004 E.011 17 – 0

Trifluralin H .009 <.009 E.004 17 – 0

2,4-D methyl ester H .016 <.009 .017 8 0 –

Benomyl H .022 <.004 .082 8 – –

Bromoxynil H <.02 M 8 0 –

Caffeine S .018 <.0096 E.0052 8 – –

Table 8. Summary of pesticide concentrations in the four irrigation return-flow drainage basins, Columbia Basin Project, Washington, July 2002 to 

October 2004.—Continued

[All concentrations are in micrograms per liter. Concentrations of pesticides in bold represent values that exceed freshwater aquatic-life benchmarks (see 

table 4). Pesticide: CIAT, 2-chloro-4-isopropylamino-6-amino-s-triazine; CAAT, chlorodiamino-s-triazine; OIET, 2-hydroxy-4-isoprobylamino-6-ethylamino-striazine; CEAT, 2-chloro-6-ethylamino-4-amino-s-triazine. Type of pesticide: F, fungicide; H, herbicide; I, insecticide; S, stimulant; T, transformation product. 

Drinking-water standards: Maximum contaminant levels for drinking water from U.S. Environmental Protection Agency (2004a). Freshwater aquatic-life 

benchmarks: Standards from U.S. Environmental Protection Agency (2004b), unless otherwise footnoted. Abbreviations: LRL, laboratory reporting limit; M, 

presence of material verified, but not quantified; n, number of samples; E, because recovery or variation in recovery was outside the acceptable range, compound 

is qualified with an E-code (estimated) or concentration reported is less than laboratory reporting level and is qualified as estimated; <, less than; –, no data or 

not available; *, interim values (Canadian Council of Resources and Environment Ministers, 1997)]

Occurrence, Distribution, and Transport of Pesticides 21
Table 8. Summary of pesticide concentrations in the four irrigation return-flow drainage basins, Columbia Basin Project, Washington, July 2002 to 

October 2004.—Continued

[All concentrations are in micrograms per liter. Concentrations of pesticides in bold represent values that exceed freshwater aquatic-life benchmarks (see 

table 4). Pesticide: CIAT, 2-chloro-4-isopropylamino-6-amino-s-triazine; CAAT, chlorodiamino-s-triazine; OIET, 2-hydroxy-4-isoprobylamino-6-ethylamino-striazine; CEAT, 2-chloro-6-ethylamino-4-amino-s-triazine. Type of pesticide: F, fungicide; H, herbicide; I, insecticide; S, stimulant; T, transformation product. 

Drinking-water standards: Maximum contaminant levels for drinking water from U.S. Environmental Protection Agency (2004a). Freshwater aquatic-life 

benchmarks: Standards from U.S. Environmental Protection Agency (2004b), unless otherwise footnoted. Abbreviations: LRL, laboratory reporting limit; M, 

presence of material verified, but not quantified; n, number of samples; E, because recovery or variation in recovery was outside the acceptable range, compound 

is qualified with an E-code (estimated) or concentration reported is less than laboratory reporting level and is qualified as estimated; <, less than; –, no data or 

not available; *, interim values (Canadian Council of Resources and Environment Ministers, 1997)]

Pesticide Type of 

pesticide LRL Median Maximum

Percentage 

of 

detections

(n=12)

Number of 

detections 

that exceed 

aquatic-life 

benchmarks

Number of 

detections 

that exceed 

drinking 

water 

standards

Lind Coulee—Continued

Chlorothalonil F 0.035 <0.04 E0.06 8 0 0

Malathion I .027 <.027 E.017 8 0 0

MCPA H .030 <.02 M 8 0 0

Oxamyl I .030 <.01 .03 8 – –

Propiconazole F .010 <.02 E.01 8 – –

Simazine H .005 <.005 .024 8 – 0

Triallate H .002 <.002 .004 8 – –

Red Rock Coulee

CIAT T 0.006 E0.011 E0.015 100 – –

Atrazine H .007 .019 .032 100 0 0

Bentazon H .012 E.04 E.07 92 – 0

2,4-D H .038 .09 .77 83 0 0

Diuron H .014 .02 .11 83 – 0

Simazine H .005 .011 .022 83 – 0

EPTC H .004 E.003 .1 67 – –

DCPA H .003 E.003 .169 58 – –

Terbacil1 H .034 E.012 E.075 58 – 0

2,4-D methyl ester H .016 .014 E.080 50 0 –

Bromacil H .018 <.03 E.03 42 0 –

Metolachlor H .006 <.013 E.011 42 0 0

Terbacil2 H .016 <.027 E.090 42 – 0

CEAT T .08 <.04 E.01 33 – –

Alachlor H .006 <.005 .013 33 – –

Metribuzin H .006 <.006 .008 33 0 0

Chlorpyrifos I .005 <.005 .027 25 0 0

Dicamba H .036 <.01 E.13 25 0 0

Azinphos-methyl I .05 <.050 E.018 17 1 –

Benomyl H .022 <.004 E.017 17 – –

Diazinon I .005 <.005 .03 17 0 0

Diphenamid H .010 <.03 E.03 17 – 0

Norflurazon H .020 <.02 M 17 – –

OIET T .032 <.008 E.006 8 – –

Caffeine S .018 <.0096 E.0089 8 – –

Chlorodiamino-s-triazine T .040 <.01 E.01 8 – –

Dacthal monoacid T 0.028 <0.01 0.02 8 – –

Ethoprophos I .005 <.005 .009 8 – –

Linuron2 H .014 <.01 E.01 8 0 –

Linuron1 H .035 <.035 E.014 8 0 –

Malathion I .027 <.027 .03 8 0 0

Prometon H .010 <.01 E.01 8 – 0

22 Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
Table 8. Summary of pesticide concentrations in the four irrigation return-flow drainage basins, Columbia Basin Project, Washington, July 2002 to 

October 2004.—Continued

[All concentrations are in micrograms per liter. Concentrations of pesticides in bold represent values that exceed freshwater aquatic-life benchmarks (see 

table 4). Pesticide: CIAT, 2-chloro-4-isopropylamino-6-amino-s-triazine; CAAT, chlorodiamino-s-triazine; OIET, 2-hydroxy-4-isoprobylamino-6-ethylamino-striazine; CEAT, 2-chloro-6-ethylamino-4-amino-s-triazine. Type of pesticide: F, fungicide; H, herbicide; I, insecticide; S, stimulant; T, transformation product. 

Drinking-water standards: Maximum contaminant levels for drinking water from U.S. Environmental Protection Agency (2004a). Freshwater aquatic-life 

benchmarks: Standards from U.S. Environmental Protection Agency (2004b), unless otherwise footnoted. Abbreviations: LRL, laboratory reporting limit; M, 

presence of material verified, but not quantified; n, number of samples; E, because recovery or variation in recovery was outside the acceptable range, compound 

is qualified with an E-code (estimated) or concentration reported is less than laboratory reporting level and is qualified as estimated; <, less than; –, no data or 

not available; *, interim values (Canadian Council of Resources and Environment Ministers, 1997)]

Pesticide Type of 

pesticide LRL Median Maximum

Percentage 

of 

detections

(n=12)

Number of 

detections 

that exceed 

aquatic-life 

benchmarks

Number of 

detections 

that exceed 

drinking 

water 

standards

Sand Hollow

Bentazon H 0.012 E0.10 E0.25 100 – –

Terbacil1 H .034 E.082 E1.01 100 – 0

CIAT T .006 E.008 E.036 92 – –

Atrazine1 H .007 .012 .029 92 0 0

2,4-D H .038 .04 .23 83 0 0

Dinoseb H .038 E.01 .14 83 31 0

Diuron H .014 .02 E.22 83 – 0

Terbacil2 H .016 E.056 E1.35 83 – 0

Bromacil H .018 E.01 E .12 67 0 0

Metribuzin H .006 E.0055 .052 58 0 0

Pendimethalin H .022 E.006 .388 58 – –

Simazine H .005 E.004 .213 58 – 0

Alachlor H .005 <.005 .012 50 – 0

Chloropyrifos I .005 <.005 .053 42 1 0

Azinphos-methyl I .05 <.050 E.034 33 4 –

Carbaryl1 I .041 <.041 E.070 33 0 0

DCPA H .003 <.003 .011 33 – 0

EPTC H .004 <.004 .085 33 – –

Metolachlor H .006 <.013 E.008 33 0 0

Carbaryl2 I .018 <.03 E.01 25 0 0

CAAT T .040 <.03 E.01 25 – –

2,4-D methyl ester H .016 <.009 .013 17 0 –

OIET T .032 <.0018 E.007 17 – –

Bromoxynil H .028 <.02 E.01 17 0 –

Caffeine S .018 <.0096 .0331 17 – –

Dicamba H .036 <.01 E.03 17 0 0

CEAT T .08 <.04 M 8 – –

Diazinon I .005 <.005 .007 8 – 0

Diphenamid H .010 <.03 E.02 8 – 0

Ethoprophos I .005 <.005 .016 8 – –

Lindane I .004 <.004 .018 8 31 0

Linuron2 H .014 <.01 E.01 8 0 –

Linuron1 H .035 <.035 E.007 8 0 –

Malathion I .027 <.027 E.015 8 0 0

MCPA H .030 <.02 E.03 8 0 0

Metalaxyl F .012 <.02 E.01 8 – –

Methomyl I .020 <.004 E.016 8 – 0

Norflurazon H .020 <.02 E.01 8 – –

Prometon H .010 <.01 M 8 – 0

Triclopyr I .026 <.02 E.01 8 – –

1Analysis by gas chromatography/mass spectrometry (GC/MS).

2Analysis by high-performance liquid chromatography/mass spectrometry (HPLC/MS).

3Canadian water-quality guidelines for the protection of freshwater aquatic life (Canadian Council of Ministers of the Environment, 2003).

Occurrence, Distribution, and Transport of Pesticides 23
Table 9. Summary of pesticide toxicity values for freshwater fish in the Columbia Basin Project, Washington.

[All concentrations are lethal concentrations for 50 percent of the target species (LC50) at 96 hours, in micrograms per liter. All data are compiled from the U.S. 

Environmental Protection Agency ECOTOX database (U.S. Environmental Protection Agency, 2005a). Abbreviations: N, number of references for specific 

studies; CAS, Chemical Abstract Services; –. not available]

Compound CAS registry 

No. Name Species N Minimum Median Maximum

2,4-D 94-75-7 Carp Cyprinus carpio 9 5,100 21,450 270,000

Pumpkinseed Lepomis gibbosus 1 – 94,600 –

Bluegill Lepomis macrochirus 4 7,400 221,500 263,000

Smallmouth bass Micropterus dolomieui 1 – 3,100 –

Cutthroat trout Oncorhynchus clarki 2 24,500 44,250 64,000

Rainbow trout Oncorhynchus mykiss 8 1,400 27,300 358,000

Chinook salmon Oncorhynchus tshawytscha 1 – 4800 –

Lake trout Salvelinus namaycush 2 44,500 44,750 45,000

2,4-DB 94-82-6 Bluegill Lepomis macrochirus 3 7,500 7,500 16,800

Rainbow trout Oncorhynchus mykiss 4 2,000 3,700 14,300

Acrolein 107-02-8 Bluegill Lepomis macrochirus 5 22 70 100

Largemouth bass Micropterus salmoides 1 – 160 –

Coho salmon, silver salmon Oncorhynchus kisutch 1 – 68 –

Rainbow trout, Donaldson trout Oncorhynchus mykiss 7 16 74 187

Alachlor 15972-60-8 Carp Cyprinus carpio 1 – 4,600 –

Channel catfish Ictalurus punctatus 1 – 6,500 –

Bluegill Lepomis macrochirus 10 2,800 4,950 12,400

Rainbow trout Oncorhynchus mykiss 10 240 2,100 4,200

Atrazine 1912-24-9 Black bullhead Ameiurus melas 1 – 35,000 –

Whitefish Coregonus lavaretus 2 11,200 18,750 26,300

Carp Cyprinus carpio 1 – 18,800 –

Bluegill Lepomis macrochirus 7 6,700 42,000 69,000

Rainbow trout Oncorhynchus mykiss 6 4,500 11,750 24,000

Yellow perch Perca flavescens 1 – 50,000 –

Brook trout Salvelinus fontinalis 3 4,900 4,900 6,300

Azinphos-methyl 86-50-0 Black bullhead Ameiurus melas 3 3,500 3,500 3,500

Carp Cyprinus carpio 3 695 695 695

Threespine stickleback Gasterosteus aculeatus 2 4.8 8.45 12.1

Channel catfish Ictalurus punctatus 4 3,220 3,290 3,290

Bluegill Lepomis macrochirus 17 4.1 7.4 120

Largemouth bass Micropterus salmoides 3 4.8 4.8 5

Coho salmon Oncorhynchus kisutch 4 4.2 6.1 17

Rainbow trout Oncorhynchus mykiss 10 3.2 6.95 28

Chinook salmon Oncorhynchus tshawytscha 1 – 4.3 –

Yellow perch Perca flavescens 5 2.4 13 40

Black crappie Pomoxis nigromaculatus 2 3 3 3

Brown trout Salmo trutta 3 3.5 4 4.6

Brook trout Salvelinus fontinalis 1 – 1.2 –

Bentazon 25057-89-0 Carp Cyprinus carpio 1 – 978,000 –

Bromacil 314-40-9 Bluegill Lepomis macrochirus 1 – 127,000 –

Rainbow trout Oncorhynchus mykiss 2 36,000 50,500 65,000

Bromoxynil 1689-84-5 Bluegill Lepomis macrochirus 2 4,000 13,500 23,000

Rainbow trout Oncorhynchus mykiss 2 2,090 10,045 18,000

Carbaryl 63-25-2 Black bullhead Ameiurus melas 3 20,000 20,000 20,000

Red shiner Cyprinella lutrensis 1 – 9,200 –

Carp Cyprinus carpio 11 1,190 3,300 5,280

Threespine stickleback Gasterosteus aculeatus 2 399 2,194.5 3,990

Channel catfish Ictalurus punctatus 8 140 10,095 15,800

Bluegill Lepomis macrochirus 26 760 6,760 290,000

Largemouth bass Micropterus salmoides 3 6,400 6,400 6,400

Cutthroat trout Oncorhynchus clarki 9 970 3,950 7,100

Coho salmon Oncorhynchus kisutch 5 764 1,300 4,340

Rainbow trout Oncorhynchus mykiss 25 800 1,470 5,400

Chinook salmon Oncorhynchus tshawytscha 2 2,400 2,400 2,400

24 Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
Table 9. Summary of pesticide toxicity values for freshwater fish in the Columbia Basin Project, Washington.—Continued

[All concentrations are lethal concentrations for 50 percent of the target species (LC50) at 96 hours, in micrograms per liter. All data are compiled from the U.S. 

Environmental Protection Agency ECOTOX database (U.S. Environmental Protection Agency, 2005a). Abbreviations: N, number of references for specific 

studies; CAS, Chemical Abstract Services]

Compound CAS registry 

No. Name Species N Minimum Median Maximum

 Carbaryl–Continued 63-25-2 Yellow perch Perca flavescens 3 350 745 5,100

Black crappie Pomoxis nigromaculatus 2 2,600 2,600 2,600

Brown trout Salmo trutta 4 700 4,125 6,300

Brook trout Salvelinus fontinalis 13 900 2,500 5,400

Lake trout Salvelinus namaycush 2 690 690 690

Chlorothalonil 1897-45-6 Threespine stickleback Gasterosteus aculeatus 1 – 69 –

Channel catfish Ictalurus punctatus 3 43 52 430

Bluegill Lepomis macrochirus 5 26.3 62 386

Rainbow trout Oncorhynchus mykiss 14 7.6 17.55 250

Chlorpyrifos 2921-88-2 Threespine stickleback Gasterosteus aculeatus 1 – 8.54 –

Channel catfish Ictalurus punctatus 3 280 280 806

Bluegill Lepomis macrochirus 10 1.3 6.52 108

Cutthroat trout Oncorhynchus clarki 2 5.4 11.7 18

Rainbow trout Oncorhynchus mykiss 9 7.1 8 51

Lake trout Salvelinus namaycush 2 73 85.5 98

DCPA (Dacthal) 1861-32-1 Rainbow trout Oncorhynchus mykiss 2 6,600 18,300 30,000

Diazinon 333-41-5 Black bullhead Ameiurus melas 1 – 8,000 –

Carp Cyprinus carpio 2 3,430 4,200 4,970

Bluegill Lepomis macrochirus 21 22 170 530

Cutthroat trout Oncorhynchus clarki 4 1,700 2,230 3,850

Rainbow trout Oncorhynchus mykiss 11 90 400 3,200

Brown trout Salmo trutta 1 – 602 –

Trout family Salmonidae 1 – 8,000 –

Brook trout Salvelinus fontinalis 4 450 785 1,050

 Lake trout Salvelinus namaycush 2 600 601 602

Dicamba 1918-00-9 Bluegill Lepomis macrochirus 2 135,300 157,650 180,000

Rainbow trout Oncorhynchus mykiss 5 28,000 130,000 153,000

Channel catfish Ictalurus punctatus 6 28 53.5 118

Cutthroat trout Oncorhynchus clarki 13 41 87 1,350

Fathead minnow Pimephales promelas 12 88 155 700

Lake trout Salvelinus namaycush 11 32 79 1,400

Diphenamid 957-51-7 Bluegill Lepomis macrochirus 3 32,000 65,000 75,000

Rainbow trout, Donaldson trout Oncorhynchus mykiss 2 97,000 97,000 97,000

Diuron 330-54-1 Carp Cyprinus carpio 1 – 2,900 –

Bluegill Lepomis macrochirus 8 2,800 6,750 84,000

Cutthroat trout Oncorhynchus clarki 3 710 1,400 1,400

Rainbow trout Oncorhynchus mykiss 6 1,950 16,000 23,800

Trout family Salmonidae 1 – 1,100 –

Lake trout Salvelinus namaycush 3 1,200 2,700 2,700

Tench Tinca tinca 1 – 15,500 –

EPTC 759-94-4 Bluegill Lepomis macrochirus 3 22,400 24,800 – 

Cutthroat trout Oncorhynchus clarki 3 12,500 17,000 –

Rainbow trout Oncorhynchus mykiss 3 19,960 20,720 26,700

Lake trout Salvelinus namaycush 2 11,500 13,850 23,300

Ethalfluralin 55283-68-6 Bluegill Lepomis macrochirus 2 32 67 102

Rainbow trout Oncorhynchus mykiss 2 37 86.5 136

Ethoprophos 13194-48-4 Carp Cyprinus carpio 1 – 640 –

Bluegill Lepomis macrochirus 3 300 2,070 8,900

Rainbow trout Oncorhynchus mykiss 5 1,100 7,800 13,800

Glyphosate 1071-83-6 Carp Cyprinus carpio 2 11,000 315,500 620,000

Channel catfish Ictalurus punctatus 6 3,300 8,700 130,000

Bluegill Lepomis macrochirus 17 1,800 5,600 220,000

Chum salmon Oncorhynchus keta 4 10,000 60,500 148,000

Coho salmon, silver salmon Oncorhynchus kisutch 5 27,000 111,000 174,000

Occurrence, Distribution, and Transport of Pesticides 25
Compound CAS registry 

No. Name Species N Minimum Median Maximum

 Glyphosate–Continued 1071-83-6 Rainbow trout, Donaldson trout Oncorhynchus mykiss 26 1,300 8,650 7,815,670

Sockeye salmon Oncorhynchus nerka 1 – 26,700 –

Chinook salmon Oncorhynchus tshawytscha 5 19,000 102,000 211,000

Brown trout Salmo trutta 1 – 5,400 –

Imazypyr 81334-34-1 Channel catfish Ictalurus punctatus 1 – 100,000 –

Bluegill Lepomis macrochirus 1 – 100,000 –

Rainbow trout, Donaldson trout Oncorhynchus mykiss 1 – 100,000 –

Lindane (gamma-HCH) 58-89-9 Black bullhead Ameiurus melas 3 64 64 64

Carp Cyprinus carpio 6 90 145 13,000

Threespine stickleback Gasterosteus aculeatus 2 44 47 50

Channel catfish Ictalurus punctatus 4 44 44 450

Bluegill Lepomis macrochirus 22 25 66.5 810

Largemouth bass Micropterus salmoides 3 32 32 32

Coho salmon Oncorhynchus kisutch 4 23 32 50

Rainbow trout Oncorhynchus mykiss 11 18 30 120

Chinook salmon Oncorhynchus tshawytscha 1 – 42 –

Yellow perch Perca flavescens 4 23 68 68

Brown trout Salmo trutta 4 1.7 1.85 22

Brook trout Salvelinus fontinalis 1 – 44.3 –

Lake trout Salvelinus namaycush 3 24 32 32

Linuron 330-55-2 Channel catfish Ictalurus punctatus 2 1,800 2,350 2,900

Bluegill Lepomis macrochirus 3 9,200 9,600 16,200

Rainbow trout Oncorhynchus mykiss 2 3,000 9,700 16,400

Malathion 121-75-5 Black bullhead Ameiurus melas 3 11,700 12,900 12,900

Red shiner Cyprinella lutrensis 1 – 25 –

Carp Cyprinus carpio 14 2 6,590 13,800

Threespine stickleback Gasterosteus aculeatus 2 76.9 85.45 94

Channel catfish Ictalurus punctatus 5 7,620 8,970 52,200

Pumpkinseed Lepomis gibbosus 1 – 480 –

Bluegill Lepomis macrochirus 13 20 103 1,200

Largemouth bass Micropterus salmoides 4 250 267.5 285

Cutthroat trout Oncorhynchus clarki 4 150 240.5 1,740

Coho salmon Oncorhynchus kisutch 4 101 170 265

Rainbow trout Oncorhynchus mykiss 17 2.8 122 234

Chinook salmon Oncorhynchus tshawytscha 2 23 71.5 120

Yellow perch Perca flavescens 3 263 263 263

Brown trout Salmo trutta 3 101 101 200

Brook trout Salvelinus fontinalis 2 120 125 130

Lake trout Salvelinus namaycush 2 76 76 76

Walleye Stizostedion vitreum v. 2 64 64 64

MCPA 94-74-6 Carp Cyprinus carpio 1 – 59,000 –

Bluegill Lepomis macrochirus 1 – 97,000 –

Rainbow trout Oncorhynchus mykiss 2 91,000 91,000 91,000

Trout family Salmonidae 1 – 25,000 –

Tench Tinca tinca 1 – 45,000 –

Metalaxyl 57837-19-1 Black bullhead Ameiurus melas 1 – 100,000 –

Carp Cyprinus carpio 1 – 100,000 –

Bluegill Lepomis macrochirus 3 27,000 139,000 150,000

Rainbow trout, Donaldson trout Oncorhynchus mykiss 3 18,400 130,000 132,000

Channel catfish Ictalurus punctatus 9 300 320 1,800

Bluegill Lepomis macrochirus 18 370 850 7,700

Largemouth bass Micropterus salmoides 4 760 1,005 1,250

Cutthroat trout Oncorhynchus clarki 2 4,050 5,425 6,800

Rainbow trout Oncorhynchus mykiss 19 860 1,600 32,000

Brook trout Salvelinus fontinalis 5 1,200 1,500 2,200

Table 9. Summary of pesticide toxicity values for freshwater fish in the Columbia Basin Project, Washington.—Continued

[All concentrations are lethal concentrations for 50 percent of the target species (LC50) at 96 hours, in micrograms per liter. All data are compiled from the U.S. 

Environmental Protection Agency ECOTOX database (U.S. Environmental Protection Agency, 2005a). Abbreviations: N, number of references for specific 

studies; CAS, Chemical Abstract Services]

26  Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
Table 9. Summary of pesticide toxicity values for freshwater fish in the Columbia Basin Project, Washington.—Continued

[All concentrations are lethal concentrations for 50 percent of the target species (LC50) at 96 hours, in micrograms per liter. All data are compiled from the U.S. 

Environmental Protection Agency ECOTOX database (U.S. Environmental Protection Agency, 2005a). Abbreviations: N, number of references for specific 

studies; CAS, Chemical Abstract Services]

Compound CAS registry 

No. Name Species N Minimum Median Maximum

Metolachlor 51218-45-2 Channel catfish Ictalurus punctatus 1 – 4,900 –

Bluegill Lepomis macrochirus 1 – 10,000 –

Rainbow trout Oncorhynchus mykiss 1 – 3,900 –

Metribuzin 21087-64-9 Channel catfish Ictalurus punctatus 1 – 3,400 –

Bluegill Lepomis macrochirus 3 75,960 92,000 131,300

Rainbow trout Oncorhynchus mykiss 5 42,000 76,770 147,000

Metsulfuron methyl 74223-64-6 Bluegill Lepomis macrochirus 1 – 150,000 –

Rainbow trout, Donaldson trout Oncorhynchus mykiss 1 – 150,000 –

Norflurazon 27314-13-2 Bluegill Lepomis macrochirus 1 – 16,300 –

Rainbow trout Oncorhynchus mykiss 1 – 8,100 –

Oxamyl 23135-22-0 Channel catfish Ictalurus punctatus 2 13,500 15,500 17,500

Bluegill Lepomis macrochirus 4 5,600 6,415 10,000

Rainbow trout Oncorhynchus mykiss 4 3,700 4,450 12,400

Pendimethalin 40487-42-1 Channel catfish Ictalurus punctatus 2 418 1,159 1,900

Bluegill Lepomis macrochirus 4 199 980 90,400

Rainbow trout Oncorhynchus mykiss 4 138 760 86,600

Prometon 1610-18-0 Black bullhead Ameiurus melas 1 – 20,000 –

Bullhead catfish Ameiurus sp. 1 – 20,000 –

Bluegill Lepomis macrochirus 3 15,500 40,000 41,500

Rainbow trout Oncorhynchus mykiss 5 12,000 16,000 20,000

Propiconazole 60207-90-1 Carp Cyprinus carpio 5 5,700 21,000 46,000

Channel catfish Ictalurus punctatus 3 4,870 4,870 12,000

Bluegill Lepomis macrochirus 5 1,300 5,500 9,800

Rainbow trout, Donaldson trout Oncorhynchus mykiss 11 830 5,200 506,000

Brown trout Salmo trutta 3 1,200 3,390 3,390

Simazine 122-34-9 Black bullhead Ameiurus melas 1 – 65,000 –

Sunfish family Centrarchidae 5 14,300 56,000 695,000

Channel catfish Ictalurus punctatus 1 – 85,000 –

Pumpkinseed Lepomis gibbosus 1 – 27,000 –

Bluegill Lepomis macrochirus 6 16,000 95,000 118,000

Largemouth bass Micropterus salmoides 1 – 46,000 –

Rainbow trout Oncorhynchus mykiss 5 40,500 56,000 70,500

Yellow perch Perca flavescens 1 – 90 –

Terbacil 5902-51-2 Bluegill Lepomis macrochirus 2 102,900 107,450 112,000

Rainbow trout Oncorhynchus mykiss 3 46,200 54,000 79,000

Triallate 2303-17-5 Bluegill Lepomis macrochirus 3 1,300 1,330 2,400

Rainbow trout Oncorhynchus mykiss 2 1,200 1,350 1,500

Triclopyr 55335-06-3 Chum salmon Oncorhynchus keta 2 300 3,900 7,500

Coho salmon Oncorhynchus kisutch 6 260 1,150 9,600

Rainbow trout Oncorhynchus mykiss 3 1,100 2,200 7,500

Sockeye salmon Oncorhynchus nerka 4 400 1,300 7,500

Chinook salmon Oncorhynchus tshawytscha 2 1,100 5,400 9,700

Trifluralin 1582-09-8 Carp Cyprinus carpio 1 – 660 –

Channel catfish Ictalurus punctatus 3 210 417 2,200

Bluegill Lepomis macrochirus 7 8.4 58 190

Largemouth bass Micropterus salmoides 2 75 75 75

Rainbow trout Oncorhynchus mykiss 8 10 41.5 210

Xylene 68920-06-9 Bluegill Lepomis macrochirus 16 8,600 14,700 24,500

Rainbow trout, Donaldson trout Oncorhynchus mykiss 4 3,300 10,850 17,300

Occurrence, Distribution, and Transport of Pesticides 27
Figure 4. Pesticide concentrations in four irrigation return-flow drainage basins, Columbia Basin Project, Washington, July 2002 

to October 2004.

waae700_01.fig04

0

5

10

15

20

25

2002 2003 2004

TOTAL NUMBER OF PESTICIDES DETECTED

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2.0

TOTAL CONCENTRATION OF ALL DETECTED PESTICIDES,

IN MICROGRAMS PER LITER

J A S O N D J F M A M J J A S O N D J F M A M J J A S O

SAND HOLLOW

LIND COULEE

RED ROCK COULEE

CRAB CREEK

28  Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
Relation of Pesticide Use and Pesticides 

Detected 

The frequency of pesticide detections is related to 

chemical and physical properties of the specific pesticide, 

environmental conditions, and amount of pesticide used. 

Frequency of pesticide detection typically is low in areas of 

low use and high where pesticide use is high. Seventy to 80 

percent of total annual pesticide use in the United States is 

in agriculture (Aspelin, 1997). Non-agricultural uses may be 

significant in some areas, however, and include residential pest 

control, aquatic pest control, rights-of-way applications for 

pest control, ornamental and turf pest control, and pest control 

in commercial, industrial, and institutional settings (Larson 

and others, 1997).

Pesticide-Use Data

For each pesticide detected in the drainage basins, 

the total quantity of each pesticide applied to agricultural 

fields in 2003 was estimated as the sum of annual pesticide 

applications to each crop type in the drainage basin. For each 

pesticide applied to a specific crop in a given drainage basin, 

the total quantity used annually was computed as the product 

of the rate of pesticide application to that crop in pounds of 

active ingredient per acre per year, the total acreage of the crop 

in the drainage basin, and the percentage of that total acreage 

estimated to be treated with the pesticide. Pesticide application 

rates and treatment percentages were obtained from the 

National Agriculture Statistics Service (NASS) where possible 

(U.S. Department of Agriculture, 2005) and from a 1995 

survey conducted in the study area by the National Center for 

Food and Agricultural Policy (Anderson and Gianessi, 1995) 

for those crops that are not included in the NASS statistics. 

Data for total crop acreages were obtained from a geographic 

information system database of cultivated fields (Patricia Daly, 

Franklin County Conservation District, written commun., 

2004). The crop-acreage database includes only acreages for 

alfalfa, corn, onions, potatoes, pasture, peas, mint, wheat, and 

orchards and does not include acreages for minor crops such 

as carrots; therefore, some pesticides that may be used in the 

basin were not included in the calculation if they are used 

specifically on only a few crops not in the database. 

In addition to pesticides applied to agricultural lands for 

control of weeds and pests, herbicides are applied to roads 

and rights-of-way along irrigation canals, drains, and return 

flows by local irrigation districts to control terrestrial weed 

growth (table 10). Herbicide application for non-agricultural 

weed control ranged from 470 to 10,300 lb during 2003. 

Concentrations of only three of the eight herbicides (2,4-D, 

dicamba, and diuron were analyzed in samples of irrigationreturn flow during this study. Diuron and 2,4-D were among 

the five most frequently detected pesticides and dicamba was 

detected in nearly 25 percent of samples collected during this 

study (table 7).

Pesticide-use data for residential and other nonagricultural uses are more limited than data for agricultural 

pesticide use (Barbash and Resek, 1996). No studies of 

non-agricultural pesticide use in the study area are known 

to exist. However, an estimate of residential use in the study 

area was computed on the basis of residential sales data 

collected in King County, Wash. (Phillip Dickey, Washington 

Toxics Coalition, written commun., 2004). A per-household 

sales rate was computed on the basis of total housing units in 

King County (U.S. Census Bureau, 2004), and this rate was 

multiplied by total housing units in each drainage basin. This 

method for computing the amount of residential pesticide 

use assumes that all pesticides purchased in a given year 

are used that year and that residential usage patterns in the 

study area are the same as those in King County. Pesticide 

registration data for the State of Washington are available 

from Washington State Pest Management (http://wsprs.wsu.

edu/Pesticides.html), and the registration status of pesticides 

analyzed in this study is listed in table 19 (at back of report).

Herbicide Trade or 

common name

Amount applied

(pounds)

2,4-D1 Weedestroy AM-40 10,300

Acrolein Magnacide H UH

Copper sulfate – UH

Dicamba Banvel, Vanquish 510

Diuron Diuron 4L1VM, Direx 8,560

Glyphosate2 AquaNeat 3,350

Imazypyr Arsenal UH

Metsulfuron methyl Escort x P 470

Xylene – None

1 Dimethylamine salt of 2,4-Dichlorophenoxyacetic acid was applied.

2 Isopropylamine salt of glyphosate was applied.

Table 10. Herbicides applied to irrigation canals, roads, and rights of 

way along irrigation canals, drains, and return flows in the four irrigation 

return-flow drainage basins, Columbia Basin Project, 2003.

[Abbreviations: CAS, Chemical Abstract Services; None, none applied in 

2003; UH, used historically; –, not available]

Occurrence, Distribution, and Transport of Pesticides 29
Pesticides Applied and Detected in SurfaceWater Samples

Of the 107 pesticides analyzed for in surface-water 

samples from the four drainage basins, 42 herbicides, 

insecticides, and fungicides were detected, and 31 of 

those detected were reported as being applied to the major 

agricultural crops in the basins (fig. 5). Pesticides that were 

analyzed for but not detected are listed in table 20 (at back of 

report).

The general pesticide-usage pattern in each basin varies 

depending on the acreage of crops grown in that basin. In 

drainage basins where orchards predominate, the largest 

applications are insecticides, whereas in basins with larger 

percentages of field crops the largest application is herbicides. 

Usage patterns in Crab Creek and Sand Hollow basins are 

similar: the largest total amounts applied are the insecticides 

azinphos-methyl, carbaryl, and chlorpyrifos and the herbicide 

EPTC (fig. 5). In Red Rock Coulee basin, DCPA was the 

most heavily applied pesticide, followed by the fungicide 

chlorothalonil, the herbicide EPTC, and the insecticides 

chlorpyrifos and azinphos-methyl. In Lind Coulee basin, 

which has a large percentage of dryland agricultural area, 

the herbicides 2,4-D and EPTC were applied in the largest 

amount, followed by the fungicide chlorothalonil. 

The total amount of pesticides applied in a basin does 

not correspond directly with the percentage of samples with 

detections. Some pesticides, such as atrazine, bentazon, and 

diuron, are applied in small amounts but were detected in a 

large percentage of samples; others, such as chlorothalonil, 

are applied in large amounts but were not frequently detected. 

Other pesticides, such as carbofuran, methyl parathion, and 

oryzalin, are known to be used on agricultural crops in the 

study area but were not detected in any of the surface-water 

samples. 

Eleven pesticides that were detected in the drainage 

basins are available for purchase and use for residential 

applications (table 11). A nationwide study in the early 1990s 

showed that total amounts of pesticides sold for agricultural 

use exceeded those used for non-agricultural use by a factor of 

three (Aspelin and others, 1992). However, in this study area, 

the total amount of non-agricultural pesticides applied in these 

basins was significantly less than amounts applied to major 

agricultural crops. For example, the highest total non-cropland 

usage of 2,4-D was 35 pounds applied in Crab Creek and Lind 

Coulee, whereas agricultural use amounted to greater than 

29,000 lb in that basin. Prometon and triclopyr were the only 

residential or commercially applied pesticides not used on 

major agricultural crops; however, they have many commercial 

uses, such as on landscaping, highway, or power line rights-ofway, so detections can not be linked directly to residential use. 

Eight pesticides were detected in the drainage basins, 

but were not reported as having any major agricultural or 

residential use (table 12). Most of these were detected only 

once or twice, except for bromacil and dinoseb. Bromacil is an 

herbicide detected in samples from all drainage basins and is 

registered for use along highway right-of-ways, parking lots, 

and commercial landscaping. The USEPA banned dinoseb use 

in 1986. However, according to the Washington Agricultural 

Statistics Service (2005), dinoseb was reported as being used 

on apples as late as 2001. Possibly, the detection of dinoseb in 

the Sand Hollow basin indicates current use.

Table 11. Estimated application for residential use of non-agricultural 

pesticides detected in water samples from the four irrigation return-flow 

drainage basins, Columbia Basin Project, Washington, July 2002 to October 

2004.

[All application values are in pounds per year. <, less than]

Pesticide

Estimated application of non-agricultural pesticides 

in irrigation-return flow drainages

Crab 

Creek

Lind 

Coulee

Red Rock 

Coulee

Sand 

Hollow

2,4-D 35 35 1.4 3.4

Carbaryl 14 14 .5 1.3

Chlorothalonil 1 1.0 .04 .1

Chlorpyrifos .1 .1 <.01 .01

Diazinon 7.8 7.9 .3 .8

Dicamba 2.4 2.5 .1 .2

Malathion 5.5 5.6 .2 .5

Pendimethalin 1.7 1.7 .06 .2

Prometon 3.0 3.0 .1 .3

Triclopyr 2.1 2.1 .08 .2

Trifuluralin 4.1 4.1 .2 .4

Table 12. Pesticides with no reported residential or major agricultural 

use detected in water samples from the four irrigation return-flow drainage 

basins, Columbia Basin Project, Washington, July 2002 to October 2004.

Pesticide Possible sources

Benomyl Minor agricultural use

Bromacil Rights-of-way, parking lots, commercial landscaping

Clopyralid Minor agricultural use

Dinoseb Historical use, banned in 1986

Diphenamid Unknown, not registered for use in Washington

Ethalfluralin Minor agricultural use

gamma-HCH 

(Lindane) Seed treatment, head-lice and animal shampoos

Linuron Minor agricultural use

30 Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
waAE700_01.fig05A

A. Crab Creek

2-4-D

2,4-DB

Alachlor

Atrazine

Bentazon

Bromoxynil

DCPA

Dicamba

Diuron

EPTC

MCPA

Metolachlor

Metribuzin

Nicosulfuron

Norflurazon

Pendimethalin

Simazine

Terbacil

Triallate

Trifluralin

Azinphos-methyl

Carbaryl

Chlorpyrifos

Diazinon

Ethoprop

Malathion

Methomyl

Oxamyl

Chlorothalonil

Metalaxyl

Propiconazole

TOTAL PESTICIDES APPLIED, IN POUNDS PER YEAR PERCENTAGE OF SAMPLES WITH DETECTIONS

HERBICIDES INSECTICIDES FUNGICIDES

0

5,000

10,000

15,000

20,000

30,000

25,000

0

20

40

60

80

100

No detections

Figure 5. Pesticide-application rates and percentage of surface-water samples with pesticide detections in the four irrigation returnflow drainage basins, Columbia Basin Project, Washington, July 2002 to October 2004.

Occurrence, Distribution, and Transport of Pesticides  31
waAE700_01.fig05B

B. Lind Coulee

TOTAL PESTICIDES APPLIED, IN POUNDS PER YEAR PERCENTAGE OF SAMPLES WITH DETECTIONS

HERBICIDES INSECTICIDES FUNGICIDES

0

5,000

10,000

15,000

20,000

30,000

25,000

0

20

40

60

80

100

2-4-D

2,4-DB

Alachlor

Atrazine

Bentazon

Bromoxynil

DCPA

Dicamba

Diuron

EPTC

MCPA

Metolachlor

Metribuzin

Nicosulfuron

Norflurazon

Pendimethalin

Simazine

Terbacil

Triallate

Trifluralin

Azinphos-methyl

Carbaryl

Chlorpyrifos

Diazinon

Ethoprop

Malathion

Methomyl

Oxamyl

Chlorothalonil

Metalaxyl

Propiconazole

Figure 5. Continued.

32 Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
Figure 5. Continued.

waAE700_01.fig05C

C. Red Rock Coulee

TOTAL PESTICIDES APPLIED, IN POUNDS PER YEAR PERCENTAGE OF SAMPLES WITH DETECTIONS

HERBICIDES INSECTICIDES FUNGICIDES

0

5,000

10,000

15,000

20,000

30,000

25,000

0

20

40

60

80

100

2-4-D

2,4-DB

Alachlor

Atrazine

Bentazon

Bromoxynil

DCPA

Dicamba

Diuron

EPTC

MCPA

Metolachlor

Metribuzin

Nicosulfuron

Norflurazon

Pendimethalin

Simazine

Terbacil

Triallate

Trifluralin

Azinphos-methyl

Carbaryl

Chlorpyrifos

Diazinon

Ethoprop

Malathion

Methomyl

Oxamyl

Chlorothalonil

Metalaxyl

Propiconazole

No detections

Occurrence, Distribution, and Transport of Pesticides  33
Figure 5. Continued.

waAE700_01.fig05D

D. Sand Hollow

2-4-D

2,4-DB

Alachlor

Atrazine

Bentazon

Bromoxynil

DCPA

Dicamba

Diuron

EPTC

MCPA

Metolachlor

Metribuzin

Nicosulfuron

Norflurazon

Pendimethalin

Simazine

Terbacil

Triallate

Trifluralin

Azinphos-methyl

Carbaryl

Chlorpyrifos

Diazinon

Ethoprop

Malathion

Methomyl

Oxamyl

Chlorothalonil

Metalaxyl

Propiconazole

TOTAL PESTICIDES APPLIED, IN POUNDS PER YEAR PERCENTAGE OF SAMPLES WITH DETECTIONS

HERBICIDES INSECTICIDES FUNGICIDES

0

10,000

5,000

0

20

40

60

80

100

34 Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
Transport of Pesticides

Comparison of Pesticide Detections with 

Historical Data

Most historical pesticide data for sites in this study were 

collected during the 1990s by the USGS NAWQA program. 

Samples also were collected in the mid-1970s in Crab Creek 

and Lind Coulee basins by the Bureau of Reclamation, 

and some samples were collected by the Washington State 

Department of Ecology. Only one previous sample exists for 

Red Rock Coulee basin, so no comparison was made for that 

basin. 

Comparison with 1970s Data

Thirteen of the pesticides analyzed for in the 1970s in 

samples from Crab Creek and Lind Coulee basins also were 

analyzed for in this study (table 13). Of these pesticides, 

4,4’-DDE, dieldrin, and lindane were detected in the 1970s 

(Greene and others, 1994) and diazinon, EPTC, malathion, 

and trifluralin were detected during this study. However, 

given the much lower reporting limits in the current study, 

the detections of diazinon, EPTC, malathion, and trifluralin 

do not necessarily represent an increase in detection rate 

for those compounds. If the detections in the current study 

were censored to the historical reporting limits, all of them 

would be reported as “less than” values. However, the lack of 

detections of 4,4’-DDE, dieldrin, and lindane in the current 

study represents a decrease in the detection rate of these 

compounds. Use of dieldrin and DDT (the parent compound 

of 4,4’-DDE) were banned in 1985 and 1972, respectively, 

which likely is a cause for the decrease in detection rates since 

the 1970s. Decreased detection rates can be a combination of 

a decrease in usage, the smaller number of samples collected 

during this study, and changes from furrow to sprinkler 

irrigation methods (Gruber and Munn, 1996; Ebbert and Kim, 

1998). Crab Creek Lateral, a small drainage basin in the CBP 

north of Red Rock Coulee, was sampled 38 times from 1993 

to 1997 during the NAWQA program; 8 of the 38 samples 

contained dieldrin and 5 of the 38 samples contained trace 

amounts of 4,4-DDE. Because dieldrin and DDT bind strongly 

to soil particles, the detection of these banned chemicals 

in water samples is attributed to erosion from agricultural 

fields (Gruber and Munn, 1996; Ebbert and Kim, 1998). 

Degradation of the original pesticides into metabolites that 

were not analyzed during the current study also may be a 

factor that makes comparison of older data difficult. Analysis 

of additional pesticide metabolites should be considered for 

future studies.

Comparison with 1990s Data

A better comparison than in the 1970s can be made 

between data collected during this study and data collected 

previously by the NAWQA program at Crab Creek, Lind 

Coulee, and Sand Hollow during the 1990s, because similar 

methods were used in both studies. All pesticides detected in 

the 1990s also were analyzed for in this study; however, some 

pesticides detected in the current study were not analyzed for 

in the 1990s, so those were excluded from further analysis. 

Thirty-six of the pesticide compounds analyzed for in 

both studies were detected during the 1990s, and 36 were 

detected during the current study (table 14). Most compounds 

detected frequently in one study were detected frequently in 

Table 13. Detection rates of pesticides analyzed during the 1970s and 

from July 2002 to October 2004 in Crab Creek and Lind Coulee irrigation 

return-flow drainage basins, Columbia Basin Project, Washington.

[Detection rates are number of detections/number of samples analyzed]

Pesticide

Detection rate

1970s Current study (July 2002 to 

October 2004)

Crab 

Creek

Lind 

Coulee

Crab 

Creek

Lind 

Coulee

4,4’-DDE 2/37 2/38 0/12 0/12

Diazinon 0/37 0/38 1/12 0/12

Dieldrin 3/42 13/38 0/12 0/12

Disulfoton 0/37 0/38 0/12 0/12

EPTC 0/37 0/38 7/12 4/12

alpha-HCH 0/5 0/0 0/12 0/12

gamma-HCH 

(Lindane)

4/42 0/38 0/12 0/12

Malathion 0/37 0/38 0/12 1/12

Methyl parathion 0/37 0/38 0/12 0/12

Parathion 0/37 0/38 0/12 0/12

Trifluralin 0/37 0/38 0/12 2/12

Aldicarb 0/37 0/38 0/12 0/12

Cycloate 0/37 0/38 0/12 0/12

Occurrence, Distribution, and Transport of Pesticides  35
Table 14. Detection rates of pesticides analyzed for during the 1990s and from July 2002 to October 2004 in the Crab Creek, Lind Coulee, and Sand 

Hollow irrigation return-flow drainage basins, Columbia Basin Project, Washington.

[Period of record for historical samples: Crab Creek, 1994–95; Lind Coulee, 1994–2000; Sand Hollow, 1994–97. Pesticide: CIAT, 2-Chloro-4-

isopropylamino-6-amino-s-triazine]

Pesticide

Percentage of samples with 

detections during the 1990s

Percentage of samples with 

detections during the current study 

(July 2002 to October 2004)

Crab Creek Lind Coulee Sand Hollow Crab Creek Lind Coulee Sand Hollow

2,4-D 17 29 40 92 67 83

2,4-DB 0 0 0 0 17 0

2,6-Diethylaniline 0 0 43 0 0 0

Acetochlor 0 4 0 0 0 0

Alachlor 17 40 100 25 0 50

Atrazine 100 78 100 100 83 92

Azinphos-methyl 0 5 0 17 25 33

Benfluralin 0 2 0 0 0 0

Bentazon 50 0 80 100 50 100

Bromacil 0 0 0 17 42 67

Bromoxynil 0 0 0 0 8 17

Butylate 0 2 0 0 0 0

Carbaryl 0 24 14 17 0 33

Carbofuran 0 9 0 0 0 0

Chlorothalonil 0 0 0 0 8 0

Chlorpyrifos 17 29 29 25 17 42

CIAT 67 67 86 100 75 92

Clopyralid 0 0 0 8 0 0

Cyanazine 17 42 0 0 0 0

DCPA 67 65 86 50 58 33

Diazinon 0 16 0 8 0 8

Dicamba 0 0 0 25 25 17

Dieldrin 0 4 0 0 0 0

Dinoseb 0 0 20 0 0 83

Disulfoton 0 2 0 0 0 0

Diuron 17 43 0 83 83 83

EPTC 83 55 86 58 33 33

Ethalfluralin 0 16 0 0 17 0

Ethoprophos 50 13 29 0 0 8

Fonofos 0 2 0 0 0 0

Lindane 0 0 0 0 0 8

Linuron 0 5 0 8 17 8

Malathion 0 2 14 0 8 8

MCPA 0 0 0 0 8 8

Metolachlor 50 56 71 33 58 33

Metribuzin 17 22 71 8 33 58

Napropamide 0 2 0 0 0 0

Norflurazon 0 0 0 0 0 8

Oxamyl 0 0 0 0 8 0

4,4’-DDE 0 2 0 0 0 0

Pendimethalin 0 33 0 0 42 58

Prometon 0 0 0 0 0 8

Propyzamide 17 0 0 0 0 0

Simazine 83 20 71 75 8 58

Terbacil 83 22 86 50 0 100

Triallate 0 9 0 0 8 0

Triclopyr 0 0 0 0 0 8

Trifluralin 0 35 0 0 17 0

No. of samples 

collected 6 55 7 12 12 12

36  Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
the other, with a few exceptions. For example, cyanazine was 

detected in more than 40 percent of samples collected from 

Lind Coulee in the 1990s, but was not detected at all in the 

current study, and bromacil was not detected at any of the sites 

in the 1990s but was detected in samples from all three sites 

in the current study. These differences in detections may be 

due to changes in land use, changes in crop rotations, or just a 

strategic change of pesticide applications.

Two methods were used to compare historical data with 

data from the current study to determine if any change in 

concentrations occurred over time: (1) the Wilcoxon ranksum test for sites with a small number of samples and a large 

gap between sampling periods, and (2) the seasonal Kendall 

test for sites with a larger, more continuous sampling record 

(Helsel and Hirsch, 2002). 

The Wilcoxon rank-sum test (Helsel and Hirsch, 

2002) was used to compare historical and current pesticide 

concentrations at Crab Creek and Sand Hollow. A small 

number of samples (six to seven) were collected from Crab 

Creek and Sand Hollow during 1994–95 and 1994–97, 

respectively. One sample from Sand Hollow in 1992 was 

analyzed for a limited number of pesticides. This sample 

was not included in the historical comparison because it was 

unfiltered water rather than filtered water, as were the other 

samples. 

The rank-sum test is a nonparametric test that uses 

relative ranks of data points to determine if one data set has 

higher values than another data set. For these tests, if the 

earlier data set included all lower ranks and the later data set 

included all higher ranks, the trend would be decreasing. If no 

trend was present, then the sums of the ranks would be about 

equal. A trend was considered to be statistically significant if 

the p-value from the rank-sum test was ≤0.05. Figure 6 shows 

statistically significant differences in pesticide concentrations 

between the two study periods. 

Statistically significant increases in diuron concentrations 

(p-value = 0.048) were observed in samples from Crab 

Creek. Statistically significant decreases were observed in 

ethoprophos and atrazine concentrations (p-value = 0.012 and 

0.038, respectively), and all other pesticides detected at Crab 

Creek showed no statistically significant trend. Statistically 

significant increases in bromacil, diuron, and pendimethalin 

concentrations were observed in samples from Sand 

Hollow (p-values of 0.026, 0.007, and 0.019, respectively) 

and statistically significant decreases in concentration of 

2,6-diethylanaline, alachlor, atrazine, DCPA, and EPTC were 

observed (p-values of 0.02, 0.0005, 0.001, 0.023, and 0.023, 

respectively). Changes in concentration or detection frequency 

may be due to reductions in pesticide application, changes in 

agricultural land use, changes in pesticide use and application 

techniques, changes in managerial practices, environmental 

changes that may affect pesticide degradation, differences 

in times of sample collections, differences in sampling 

techniques, or any combination of these factors. Additional 

sampling would be needed to determine if these differences 

are an actual trend over time. Results from the mid-1990s 

focused mostly on the non-irrigation and early irrigation 

seasons, whereas the current study was weighted towards 

collecting samples throughout the irrigation season.

A larger data set exists for Lind Coulee, because samples 

were collected from 1994 to 2000 for the previous study and 

from 2002 to 2004 for the current study. Seasonal Kendall 

trend analysis was used to determine trends over time using 

the ESTREND program (Schertz and others, 1991). The 

seasonal Kendall test is a nonparametric test that compares 

relative ranks of data rather than actual concentration values. 

Because the data show changes depending on whether it 

is irrigation season or not, the seasons were defined to be 

November through March (non-irrigation season) and April 

through October (irrigation season) and irrigation season data 

are compared only with irrigation season data and similarly for 

non-irrigation season data. 

No statistically significant trends were determined at Lind 

Coulee at p=0.05. However, simazine and terbacil showed 

marginally significant decreasing trends with p-values of 0.07 

and 0.10, respectively. Almost all detections occurred prior to 

1999 (fig. 7). 

Occurrence, Distribution, and Transport of Pesticides  37
Figure 6 Comparison of historical and current pesticide concentrations in the Crab Creek and Sand Hollow irrigation return-flow 

drainage basins, Columbia Basin Project, Washington.

waae700_01-fig06

-0.02

0

0.02

0.04

0.06

0.08

0.10

0.12

ATRAZINE DIURON ETHOPROPHOS

STUDY PERIOD

PESTICIDE CONCENTRATION, IN MICROGRAMS PER LITER

(7)

(12)

(6)

(12)

(6)

(12)

A. Crab Creek

-0.2

0

0.2

0.4

0.6

0.8

1.0

(7)

(12) (5)

(12)

(12) (5)

(12)

(7)

(12)

(7)

(12)

(7) (12) (7) (12)

PESTICIDE CONCENTRATION, IN MICROGRAMS PER LITER

STUDY PERIOD

2,6-DIETHYLANILINE ALACHLOR ATRAZINE BROMACIL DCPA DIURON EPTC PENDIMETHALIN

(7)

B. Sand Hollow

1.2

(12)

EXPLANATION

 SCHEMATIC BOXPLOT

NUMBER OF DATA POINTS 

 USED IN CONSTRUCTION OF 

 SCHEMATIC PLOT

VERTICAL LINES —Lines from

rectangle extend to the limit of

the data

75th PERCENTILE

MEDIAN

25th PERCENTILE

SEMIQUARTILE

RANGE

HISTORICAL CURRENT

38  Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
Figure 7. Concentrations of simazine and terbacil in the Lind Coulee irrigation return-flow drainage basin, Columbia Basin Project, 

Washington, 1994 to 2004.

waAE700_01.fig07

A. Simazine

YEAR

NON-DETECTION

DETECTION

B. Terbacil

1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

0

0.005

0.010

0.015

0.020

0.025

0

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040

0.045

0.050

0.055

0.060

TERBACIL CONCENTRATION, IN MICROGRAMS PER LITER

SIMAZINE CONCENTRATION,

IN MICROGRAMS PER LITER

Occurrence, Distribution, and Transport of Pesticides  39
Comparison of Pesticide Detections with 

National NAWQA Data

Pesticide concentrations detected in this study for the 

seven most frequently detected herbicides (table 8), as well as 

dinoseb and the three most frequently detected insecticides, 

were compared with pesticide concentrations in previous 

surface-water samples collected throughout the Central 

Columbia Plateau (Williamson and others, 1998), Yakima 

River basin (Fuhrer and others, 2004), and national NAWQA 

study units (fig. 8). 

Overall, pesticide data in this study generally agree with 

those of the Central Columbia Plateau NAWQA study, which 

included some of the same sites. Pesticides detected during 

this study tend to decrease on the middle to lower end of the 

concentration range compared to all streams of the Central 

Columbia Plateau study area. This difference is partially 

explained by the NAWQA program goal to sample during all 

flow stages, including storm samples that likely transport a 

greater load of pesticides. Maximum concentrations detected 

in the Central Columbia Plateau study all were higher than 

those in this study except for terbacil and dinoseb. Although 

concentrations in this study tended to be lower, the detection 

rates were higher for all pesticides except simazine. Dinoseb 

was detected only twice in Central Columbia Plateau streams, 

one of which was Sand Hollow, where all 10 detections of 

dinoseb occurred during this study. 

In the Yakima River basin, pesticide concentrations in 

agricultural streams also were similar to those detected in 

this study (Fuhrer and others, 2004). Pesticide concentration 

ranges generally overlapped in the mid to lower range for 

atrazine, simazine, azinphos-methyl, and carbaryl; terbacil and 

chlorpyrifos concentrations generally were higher in samples 

collected during this study. Detection rates also were slightly 

lower in this study than from streams in the Yakima River 

basin for all pesticides except chloropyrifos. 2,4-D, diuron, 

dinoseb, and bentazon were not analyzed for in the Yakima 

River basin, so no comparison was made for those compounds.

In comparing pesticide concentrations from this 

study with NAWQA data collected nationally, pesticide 

concentrations in this study generally were in the mid to lower 

one-half of the range of concentrations, except for terbacil 

detections during this study, which are in the upper end of 

the national range (fig. 8). The detection rate was similar for 

atrazine, CIAT, simazine, carbaryl, and chlorpyrifos, but was 

substantially higher in this study for terbacil, 2,4-D, bentazon, 

diuron, azinphos-methyl, and dinoseb. Dinoseb, in particular, 

stands out, because it was detected in less than 1 percent of all 

samples nationally but in 15 percent of samples in this study 

and about 60 percent of samples in the Sand Hollow drainage 

basin. 

Pesticides are applied to agricultural crops and residential 

lawns and gardens for control of weeds, insects, fungus, and 

other undesirable factors. Once applied, pesticides are subject 

to three types of processes, as described by Larsen and others 

(1997), that control the behavior and fate of pesticides in the 

environment: (1) transformation processes that change the 

chemical structure, (2) phase-transfer processes that control 

pesticide movement between water, biota, sediment, and the 

atmosphere; and (3) transport processes that move pesticides 

from the initial point of application to the environment. Major 

pathways of pesticide transport in this study were irrigationreturn flows, and major transport processes are by direct 

surface-water runoff from agricultural fields and by groundwater discharge that contains pesticides that have leached into 

ground water (Jones and Roberts, 1998). Pesticide runoff from 

right-of-way, commercial, and residential application also is a 

potential source of pesticide transport.

Streams interact with ground water in all landscapes 

(Winter and others, 1998). Streams lose water to ground water 

through the streambed and gain water from inflow of ground 

water through the streambed. Cessation of irrigation delivery 

water during non-irrigation seasons changes the relative 

difference between the altitude of the water table near the 

streams and the altitude of the surface-water surface, leading 

to ground-water flow to streams. Williamson and others 

(1998) showed that many irrigation wasteways and drains in 

the CBP receive large contributions of ground-water discharge. 

In the four drainage basins in this study, irrigation water is 

not delivered from November to March, and in the absence of 

natural runoff from rainfall, ground water is the predominant 

source of nitrate in surface-water irrigation-return flow 

(fig. 9). Fuhrer and others (2004) have shown that groundwater discharges are a major source of surface-water nitrate in 

irrigated areas of the western United States. Williamson and 

others (1998) note that, like nitrate, soluble pesticides such 

as atrazine can leach into ground water of the CBP and later 

be transported to agricultural irrigation-return flow drainages. 

Concentrations of atrazine in the study basins do not decrease 

during the non-irrigation season and actually increase in 

samples collected from Sand Hollow during the non-irrigation 

season (fig. 9).

Pesticides that are readily soluble in water, such as 

herbicides atrazine, bentazon, and diuron (table 15), also 

can be transported to irrigation-return flows by runoff from 

agricultural fields, highway or power line rights-of-way, 

and commercial or residential properties. Pesticide presence 

usually is related to the timing of pesticide application, 

pesticide properties, agricultural irrigation practices, and 

environmental conditions at the time of application (Wagner 

and others, 1996; Ebbert and Kim, 1998). Transport of 

pesticides also is dependent on the rate of application, the 

rate at which pesticides break down in soil and water, and the 

physical properties of the pesticide that allow it to dissolve and 

be transported by water (Williamson and others, 1998).

40 Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
Figure 8. Comparison of selected pesticide concentrations in the Columbia Basin Project, Washington, July 2002 to October 2004 

with national NAWQA concentrations.

waAE700_01.fig08

| |

| |

Azinphos-methyl (Guthion, Gusathion M) * 

23 3 48

 -- <1 0

-- 2 0

Carbaryl (Carbamine, Denapon, Sevin) 

13 13 48

 -- 47 0

– 20 0

Chlorpyrifos (Brodan, Dursban, Lorsban) 

27 16 | 48

 -- 27 | 0

-- 23 | 0

Lowest

25

percent

Middle

50

percent

Highest

25

percent

81 18 

 -- 16 

-- 12 

100 92 

 -- 78 

-- 90 

85 22 

 -- <1 

-- 6

92 82

92 82

 -- 59 

-- 78 

Herbicides–In Water

Insecticides–In Water

48

0

0

48

0

0

48

0

0

48

0

0

21 <1

0

-- <1

83 16 

 -- 25

-- 15 

56 62 

 -- 67

-- 74 

52 5

 -- 1

-- 4

2,4-D (Aqua-Kleen, Lawn-Keep, Weed-B-Gone) Dinoseb (Dinosebe) 

48

0

0

48

48

0

0

48

0

0

48

0

0

Atrazine (AAtrex, Atrex, Atred) 

Bentazon (Basagran, Betazone, Bendioxide) 

CIAT - Deethylatrazine (Atrazine metabolite, desethylatrazine) * **

Diuron (Crisuron, Karmex, Direx, Diurex) 

Simazine (Princep, Caliber 90, Gesatop, Simazat) 

Terbacil (Sinbar) 

 0.0001 0.001 0.01 0.1 1 10 100 1,000

National NAWQA frequency of detection, in percent Project sample size Project sample size

Project frequency of detection, in percent

National NAWQA frequency of detection, in percent

Project frequency of detection, in percent

CHEMICALS IN WATER

Concentrations and detection frequencies, Columbia Basin Project 2002−04

 Detected concentrations in project

 Frequencies of detection, in percent. Detection frequencies

 were not censored at any common reporting limit. The

 left-hand column is the study-unit frequency and the

 right-hand column is the national frequency.

 Less than

 Not measured or sample size less than two

 Project sample size

National ranges of detected concentrations, by land use, in 

51 NAWQA Study Units, 1991−2001—Ranges include only samples

in which a chemical was detected

 Streams in agricultural areas

 Streams in urban areas

 Streams and rivers draining mixed land uses

National water-quality benchmarks

National benchmarks include standards and guidelines related to

drinking-water quality, criteria for protecting the health of aquatic life. 

Sources include the U.S. Environmental Protection Agency and the 

Canadian Council of Ministers of the Environment

 Drinking-water quality (applies to ground water and surface water)

 Protection of aquatic life (applies to surface water only)

 No benchmark for drinking-water quality

 No benchmark for protection of aquatic life

 0.0001 0.001 0.01 0.1 1 10 100 1,000

 --

EXPLANATION

**

*

--

<

Occurrence, Distribution, and Transport of Pesticides 41
waAE700_01.fig09A

0

2

4

6

8

10

12

14

16

18

20

NITRATE (NO3) PLUS NITRITE (NO2) CONCENTRATION, IN MILLIGRAMS PER LITER

A. Nitrate plus Nitrite

SAMPLE DATE

2002 2003 2004

J A S O N D J F M A M J J A S O N D J F M A M J J A S O

12464606 SAND HOLLOW AT S RD

12464607 SAND HOLLOW

12471400 LIND COULEE

12472520 RED ROCK COULEE

12472600 CRAB CREEK

Figure 9. Concentrations of nitrate plus nitrite and atrazine in samples from streamflow-gaging stations in the four 

irrigation return-flow drainage basins, Columbia Basin Project, Washington, July 2002 to October 2004.

Site 12464606 was sampled only once, in July 2002, and all other samples for Sand Hollow basin were from site 

12464607.

42 Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
waAE700_01.fig09B

12464606 SAND HOLLOW AT S RD

12464607 SAND HOLLOW

12471400 LIND COULEE

12472520 RED ROCK COULEE

12472600 CRAB CREEK

0.0350

0.0325

0.0275

0.0300

0.0250

0.0225

0.0200

0.0175

0.0150

0.0125

0.0075

0.0100

0.0050

0.0025

0

ATRAZINE CONCENTRATION, IN MICROGRAMS PER LITER

B. Atrazine

SAMPLE DATE

2002 2003 2004

J A S O N D J F M A M J J A S O N D J F M A M J J A S O

Figure 9. Continued.

Occurrence, Distribution, and Transport of Pesticides 43
Table 15. Physical and chemical properties of pesticides frequently detected in four irrigation-return flow drainage basins in the Columbia Basin Project, 

Washington, July 2002 to October 2004.

[Solubility and partition coefficient values are from Mackay and others (1997) unless otherwise indicated. Solubility: is at 25 degrees Celsius. Partition 

coefficients: Kow, octanol-water partition coefficient; Koc, adsorption partition coefficient. Type of pesticide: F, fungicide; H, herbicide; I, insecticide. 

Abbreviations: mg/L, milligram per liter, <, less than; –, no data]

Pesticide Type of 

pesticide

Solubility

(mg/L)

Partition coefficient

log Kow log Koc

Atrazine1 H 30 2.75 2.00

Bentazon2 H 500 – –

Diuron H 40 2.78 2.6

2,4-D H 400 2.81 1.68-2.73

2,4-D methyl ester H 100 – 2.0

Simazine H 5 2.8 2.11

Terbacil1 H 710 1.89 1.74

DCPA3 H .5 – –

EPTC H 370 3.2 2.3

Bromacil H 815 2.11 1.86

Metolachlor H 430 3.13 2.26

Metribuzin2 H 1,050 1.60 1.79

Alachlor H 240 2.8 2.23

Chlorpyrifos I .73 4.92 3.78

Pendimethalin2 H .3 5.18 3.70

Azinphos-methyl I 30 2.7 2.61

Dicamba H 4,500 2.21 .34, -.4

Dinoseb H 50 3.56 2.85

Carbaryl1 I 120 2.36 2.36

Linuron1 H 75 3.0 2.91

Benomyl F 42.0 2.3 3.28

1Analyzed by gas chromatography/mass spectrometry (GC/MS) and by high-performance liquid chromatography/mass spectrometry (HPLC/MS).

2Solubility and partition coefficients are from the Extension Toxicology Network (EXTOXNET), accessed August 22, 2005, at http://extoxnet.orst.edu/. 3Solubility and partition coefficients are from the Pesticides Action Network (PAN) pesticides database, accessed August 22, 2005, at http://www.

pesticideinfo.org/Index.html. 4Reported values vary considerably. Selected value represents best judgment by Mackay and others (1997) and may be subject to a large error.

Pesticide Type of 

pesticide

Solubility

(mg/L)

Partition coefficient

log Kow log Koc

Diazinon I 60 3.3 2.76

Diphenamid H 260 1.92 2.31

Bromoxynil H 130 <2.0 –

Malathion I 145 2.8 3.26

Metalaxyl F 8,400 1.75 1.7

Methomyl I 58,000 .60 –

Norflurazon3 H 34 2.79

Trifluralin H 4.5 5.34 4.14

2,4-DB H 46 3.53 2.64

Ethalfluralin – – 31.69

Ethoprophos I 750 3.59 1.85

MCPA H 1,605 42.69 2.03-2.07

Prometon H 750 2.99 2.54

Chlorothalonil F .6 2.64 3.2

Clopyralid H – – 3.67

Lindane I 7.3 3.7 3.0

Nicosulfuron3 H 18,486 1.56 –

Oxamyl H 282,000 -.47 1.4

Propiconazole F 110 3.72 2.82

Triallate H 4 4.29 3.38

Triclopyr H 440 .42 1.30-2.89

The herbicides atrazine, bentazon, diuron, and 2,4-D 

were detected in more than one-half of samples collected at all 

four sites. Water solubility of these herbicides ranges from 30 

to 500 mg/L, and the adsorption coefficients (log Koc), which 

indicate a chemical’s affinity to partition to soil particles, is 

relatively low. These physical and chemical characteristics 

lead to a low affinity for adhering to sediment and to a high 

potential for the compounds to dissolve and be transported in 

water. 

The insecticides chlorpyrifos and azinphos-methyl each 

were detected in about one-fourth of samples collected during 

this study and were detected in all four irrigation returnflow basins, although most detections were in Sand Hollow 

drainage basin. The insecticide carbaryl was detected in 6 of 

48 samples, primarily in samples from Sand Hollow drainage 

basin. Both azinphos-methyl and carbaryl are readily soluble 

in water, with 30 and 120 mg/L solubility, respectively. 

The relatively low adsorption coefficient means that these 

insecticides are likely to dissolve and be transported in 

water. Conversely, chlorpyrifos has a low solubility in water 

(0.73 mg/L) and a relatively large adsorption coefficient, so 

is more likely to bind to soil particles. Therefore, transport 

of chlorpyrifos is by means of soil erosion into the irrigationreturn flows. Because chlorpyrifos recently was listed by 

USEPA as a Restricted Use Product (U.S. Environmental 

Protection Agency, 2003), expectations are that detections of 

this pesticide should decrease over time.

44 Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
Summary

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

Bureau of Reclamation, analyzed water-quality samples from 

sites in four irrigation-return flow drainage basins in the 

Columbia Basin Project (CBP) from July 2002 to October 

2004 to determine the occurrence, distribution, and transport 

of pesticides, in response to a recommendation by the 

National Marine Fisheries Service to monitor water quality 

in surface-water return flows in the CBP. Ten samples were 

collected in the Crab Creek, Sand Hollow, Red Rock Coulee, 

and Lind Coulee drainage basins throughout the irrigation 

season (generally April through October) and two samples 

were collected during the non-irrigation season. Samples were 

analyzed for water temperature, pH, specific conductance, 

dissolved oxygen, trace elements, major ions, and nutrients, 

and a suite of 107 pesticides and pesticide metabolites 

(pesticide transformation products). Measured pesticide 

concentrations were compared with drinking-water standards 

and aquatic-life benchmarks, and the presence of pesticides in 

samples from the irrigation-return flows was compared with 

historical data and related to current pesticide use, land use, 

and other environmental factors. 

The four drainage basins vary in size from 19 to 710 

square miles and the percentage of agricultural cropland 

ranges from about 35 percent in Crab Creek basin to 75 

percent in Lind Coulee basin. More than 95 percent of the 

cropland in Red Rock Coulee, Crab Creek, and Sand Hollow 

basins is irrigated, whereas only 30 percent of the cropland in 

Lind Coulee is irrigated. Estimates of agricultural crop acreage 

from 2003 were used to describe agricultural land use during 

the current study. The largest percentage of agricultural crop 

acreage in Red Rock Coulee, Sand Hollow, and Crab Creek 

basins was alfalfa. The second largest percentage of cropland 

in Crab Creek and Sand Hollow basins and third largest in Red 

Rock Coulee basin was orchards. During 2003, onions were 

the second largest percentage of crop acreage in Red Rock 

Coulee basin. Lind Coulee basin has the smallest percentage 

of irrigated cropland, and about one-third of the crop acreage 

in dryland wheat and another one-third in fallow cropland. 

Nearly one-third of the remaining acreage was planted in 

irrigated wheat, alfalfa, potatoes, corn, and peas. 

Although State of Washington water-temperature 

standards specify that water-temperature criteria be measured 

by the 7-day average of daily maximum temperatures, this 

was beyond the scope of this study, so temperatures measured 

during this study are only an indication of instantaneous 

temperatures at the time of sampling. Water temperature in 

18 samples was greater than the State of Washington criterion 

of 16 degrees Celsius for salmon and trout spawning, core 

rearing, and migration: 7 from Red Rock Coulee, 5 from 

Crab Creek, 4 from Lind Coulee, and 2 from Sand Hollow. 

In 11 of these 18 instances, temperature also was greater 

than the criterion of 17.5 degrees Celsius for salmon and 

trout spawning, non-core rearing, and migration. State of 

Washington aquatic-life dissolved-oxygen criteria are listed as 

1-day minimum, and the criterion of 9.5 milligrams per liter 

for salmon and trout spawning, core rearing, and migration 

was exceeded eight times from June to early October during 

this study at three sites: two times at Sand Hollow, three times 

at Red Rock Coulee, and three times at Crab Creek. State of 

Washington aquatic-life criterion for pH of 8.5 for fresh water 

was exceeded 12 times: 6 at Red Rock Coulee, 3 at Sand 

Hollow, 2 at Lind Coulee and 1 at Crab Creek. Concentrations 

of nitrate plus nitrite in two samples collected from Sand 

Hollow during the non-irrigation season exceeded U.S. 

Environmental Protection Agency Maximum Contaminant 

Level for drinking water.

Forty-two pesticides and five metabolites were detected 

in samples from the four irrigation-return flow drainage 

basins: 37 in Sand Hollow, 33 in Lind Coulee, 30 in Red 

Rock Coulee, and 28 in Crab Creek. Herbicides were the 

most frequently detected pesticides, followed by insecticides, 

metabolites, and fungicides. Atrazine, bentazon, diuron, 

and 2,4-D were the most frequently detected herbicides and 

chlorpyrifos and azinphos-methyl were the most frequently 

detected insecticides. 

Concentrations of three insecticides and one herbicide 

exceeded U.S. Environmental Protection Agency or Canadian 

freshwater aquatic-life benchmarks. Concentrations of 

the insecticide azinphos-methyl exceeded the aquaticlife benchmark at least once at each of the four sites. 

Concentrations in samples from Sand Hollow also exceeded 

the aquatic-life benchmark for chlorpyrifos, lindane, and 

dinoseb. Water-quality aquatic-life benchmarks generally were 

exceeded in June and July, during the middle of the irrigation 

season, except the criterion for dinoseb, which was exceeded 

in one sample during the non-irrigation season in February 

2003.

Pesticide application rates and treatment percentages 

from the National Agriculture Statistics Service and from 

a 1995 survey conducted in the study unit by the National 

Center for Food and Agricultural Policy and total crop acreage 

in the drainage basins were used to estimate the total quantity 

of each pesticide applied to agricultural fields in 2003. Thirtyone of the 42 herbicides, insecticides, and fungicides detected 

in surface-water samples were applied to the major agricultural 

crops in the drainage basins, and 11 of the detected pesticides 

are sold for residential application. Eight pesticides that 

were not reported as used for agricultural or residential 

purposes were detected in the surface-water samples. The 

overall pattern of pesticide use depends on which crops are 

grown in each basin. In drainage basins with predominantly 

more orchards, greater amounts of insecticides are applied, 

whereas in basins with larger percentages of field crops, more 

herbicides are applied. Similar usage patterns were in Crab 

Creek and Sand Hollow basins: the most heavily applied 

insecticides were azinphos-methyl, carbaryl, and chlorpyrifos 

and the most heavily applied herbicide was EPTC. DCPA was 

the most heavily applied herbicide in Red Rock Coulee basin, 

Summary 45
followed by the fungicide chlorothalonil, the herbicide EPTC, 

and the insecticides chlorpyrifos and azinphos-methyl. In Lind 

Coulee, which has a large percentage of dryland agricultural 

area, the most heavily applied pesticides were the herbicides 

2,4-D and EPTC, followed by the fungicide chlorothalonil. 

The total amount of non-agricultural pesticides applied by 

residential homeowners and irrigation districts was negligible 

compared to total amounts applied to agricultural crops. 

A statistical comparison of pesticide concentrations 

from this study with those in surface-water samples collected 

in the mid-1990s at Crab Creek and Sand Hollow showed a 

statistically significant increase in concentrations of diuron 

and a statistically significant decrease in concentrations of 

ethoprophos and atrazine in Crab Creek. At Sand Hollow, 

there were statistically significant increases in concentrations 

of bromacil, diuron, and pendimethalin and statistically 

significant decreases in concentrations of 2,6-diethylanaline, 

alachlor, atrazine, DCPA, and EPTC. A seasonal Kendall 

trend test on data from Lind Coulee showed no statistically 

significant trends for any pesticide for 1994 through 2004. 

A comparison of pesticide concentrations detected in this 

study with those detected in previous U.S. Geological Survey 

National Water-Quality Assessment studies of the Central 

Columbia Plateau, the Yakima River basin, and national 

agricultural studies indicated that concentrations in this study 

generally were in the middle to lower end of the concentration 

spectrum for the most frequently detected herbicides and 

insecticides, but that the overall detection rate was at the high 

end.

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46  Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
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48  Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
Table 16. Concentrations and precision data for pesticide replicate samples, Columbia Basin Project, Washington, July 2002 to October 2004.

[Pesticide target analyte: CIAT, 2-chloro-4-isopropylamino-6-amino-s-triazine; OIET, 2-hydroxy-4-isopropylamino-6-ethylamino-s-triazine.

Abbreviations: μg/L, microgram per liter; M, presence of material verified, but not quantified; E, because recovery or variation in recovery was outside the 

acceptable range, compound is qualified with an E-code (estimated) or concentration reported is less than laboratory reporting level and is qualified as estimated; 

<, less than; –, no data]

Pesticide target analyte

Concentration in 

replicates

(mg/L) 

Percentage 

of relative 

difference

2,4-D methyl ester 0.017 19

 .014 

 .037 10

 .041 

2,4-D .29 .0

 .29 

 .3 3.4

 .29 

CIAT <.03 –

 E.011 

 E.01 .0

 E.01 

 E.01 9.5

 E.011 

OIET E.009 25

 E.007 

Alachlor E.004 –

 <.005 

Atrazine .011 71

 .023 

 .02 5.1

 .019 

 .01 62

 .019 

Azinphos-methyl E.018 5.4

 E.019 

Bentazon E.05 .0

 E.05 

 E.02 .0

 E.02 

Pesticide target analyte

Concentration in 

replicates

(mg/L) 

Percentage 

of relative 

difference

Chlorpyrifos E0.004 0.0

 E.004 

DCPA .008 .0

 .008 

Dicamba E.19 38

E.13 

 .02 67

 .01 

Diphenamid M .0

 M 

Diuron .02 .0

 .02 

 E.01 .0

 E.01 

EPTC .033 3.1

 .032 

Linuron E.014 7.4

 E.013 

Metolachlor E.01 .0

 E.01 

Metribuzin E.005 .0

 E.005 

Nicosulfuron E.01 .0

 E.01 

Simazine .01 .0

 .01 

Terbacil E.022 4.7

 E.021 

Table 17. Percentage of mean recoveries from field-matrix-pesticide analyses, Columbia Basin Project, Washington, July 2002 to October 2004.

[Abbreviations: M, presence of material verified, but not quantified; –, no data] 

Pesticide target analyte Percentage of 

mean recovery

Number of 

samples

Gas Chromatography/Mass Spectrometry 

analytical data

Acetochlor 110 1

Alachlor 112 1

Atrazine 125 1

Azinphos-methyl 44 1

Benfluralin 105 1

Butylate 98 1

Carbyl 36 1

Carbofuran 145 1

Chlorpyrifos 99 1

Cyanazine 133 1

Pesticide target analyte Percentage of 

mean recovery

Number of 

samples

Gas Chromatography/Mass Spectrometry 

analytical data—Continued

CIAT 33 1

DCPA 101 1

4,4’-DDE 53 1

Diazinon 92 1

Dieldrin 86 1

2,6-Diethylanaline 70 1

Disulfoton 53 1

EPTC 92 1

Ethalfluralin 121 1

Ethoprop 91 1

References Cited 49
Pesticide target analyte Percentage of 

mean recovery

Number of 

samples

Gas Chromatography/Mass Spectrometry 

analytical data—Continued

Fipronil 166 1

Fipronil sulfide 121 1

Fipronil sulfone 108 1

Fonos 94 1

alpha-HCH 92 1

gamma-HCH 92 1

Linuron 97 1

Malathion 113 1

Methyl parathion 164 1

Metolachlor 114 1

Metribuzin 78 1

Molinate 88 1

Napropamide 90 1

Parathion 171 1

Pebulate 93 1

Pendimethalin 116 1

cis-Permethrin 55 1

Phorate 77 1

Prometon 116 1

Propyzamide 95 1

Propachlor 112 1

Propanil 121 1

Propargite 213 1

Simazine 99 1

Tebuthiuron 151 1

Terbacil 79 1

Terbufos 80 1

Thiobencarb 93 1

Triallate 92 1

Trifluralin 108 1

High-Performance Liquid Chromatography/Mass Spectrometry 

analytical data

2,4-D 37 1

2,4-D methyl ester 50 1

2,4-DB – 0

OIET – 0

3(4-Chlorophenyl)-1-methyl urea 71 1

3-Ketocarbofuran 0/M 1

Acifluorfen – 0

Aldicarb 60 1

Aldicarb sulfone 34 1

Aldicarb sulfoxide 62 1

Chloramben, methyl ester 45 1

Atrazine 78 (39,362) 1

Bendiocarb 60 1

Benomyl 85 1

Bensulfuron-methyl 150 1

Pesticide target analyte Percentage of 

mean recovery

Number of 

samples

High-Performance Liquid Chromatography/Mass Spectrometry 

analytical data—Continued

Bentazon – 0

Bromacil 60 1

Bromoxynil – 0

Caffeine 81 1

Carbaryl 82 1

Carbofuran 91 1

3-Hydroxycarbofuran 85 1

Chlorimuron-ethyl 96 1

Chlorothalonil – 0

Clopyralid – 0

Cycloate 86 1

Dacthal monoacid – 0

CIAT 52 1

Chlordiamino-s-triazine – 0

CEAT 124 1

Dicamba – 0

Dichlorprop – 0

Dinoseb – 0

Diphenamid 97 1

Diuron 109 1

Fenuron 79 1

Flumetsulam 120 1

Fluometuron 97 1

Imazaquin 86 1

Imazethapyr 105 1

Imidacloprid 128 1

Linuron 97 1

MCPA – 0

MCPB – 0

Metalaxyl 101 1

Methiocarb 89 1

Methomyl 91 1

Metsulfuron methyl 79 1

Neburon 101 1

Nicosulfuron 127 1

Norflurazon 101 1

Oryzalin 86 1

Oxamyl 67 1

Picloram – 0

Propham 74 1

Propiconazole 97 1

Propoxur 91 1

Siduron 105 1

Sulfometuron-methyl 121 1

Tebuthiuron 87 1

Terbacil 64 1

Tribenuron-methyl 87 1

Triclopyr – 0

Table 17. Percentage of mean recoveries from field-matrix-pesticide analyses, Columbia Basin Project, Washington, July 2002 to October 2004—

Continued.

[Abbreviations: M, presence of material verified, but not quantified; –, no data] 

50 Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
Table 18. Pesticide concentrations analyzed by gas chromatography/mass spectrometry and high-performance liquid 

chromatography/mass spectrometry, Columbia Basin Project, Washington, July 2002 to October 2004.

[GC/MS, analysis by gas chromatography/mass spectrometry; HPLC/MS, analysis by high-performance liquid chromatography/mass 

spectrometry. Abbreviations: E, because recovery or variation in recovery was outside the acceptable range, compound is qualified with 

an E-code (estimated) or concentration reported is less than laboratory reporting level and is qualified as estimated; <, less than]

Sampling site Date Time

Atrazine CIAT Tebuthiuron

GC/MS HPLC/MS GC/MS HPLC/MS GC/MS HPLC/MS

39632 39632 4040 4040 82670 82670

Crab Creek

 12472600 07-30-02 1020 0.021 E0.013 E0.019 E0.012 <0.02 <0.032

 12472600 09-24-02 1100 .014 E.008 E.013 E.009 <.02 <.032

 12472600 02-05-03 1120 .016 .01 E.014 E.008 <.02 <.032

 12472600 04-09-03 0930 .015 E.006 E.009 E.007 <.02 <.032

 12472600 05-07-03 0940 .023 .015 E.007 E.007 <.02 <.032

 12472600 07-01-03 1400 .019 E.009 E.011 E.006 <.02 <.032

 12472600 10-06-03 1350 .014 E.009 E.004 E.009 <.02 <.032

 12472600 02-03-04 1330 .017 E.005 E.014 <.028 <.02 <.032

 12472600 04-06-04 1310 .016 E.008 E.011 E.007 <.02 <.032

 12472600 06-08-04 1250 .019 .01 E.010 <.028 <.02 <.032

 12472600 07-07-04 1320 .026 .013 E.012 E.008 <.02 <.032

 12472600 10-05-04 1310 .018 E.006 E.010 E.005 <.02 E.004

Lind Coulee

 12471400 07-30-02 1345 0.008 E0.004 E0.005 <0.028 <0.02 <0.032

 12471400 09-24-02 1400 .009 E.004 E.006 E.004 <.02 <.032

 12471400 02-05-03 1440 .011 E.006 E.008 E.005 <.02 <.032

 12471400 04-09-03 1520 <.007 <.009 <.006 <.028 <.02 <.032

 12471400 06-07-03 1320 <.007 <.009 <.006 <.028 <.02 <.032

 12471400 07-02-03 1430 .009 E.005 E.004 <.028 <.02 <.032

 12471400 10-07-03 1440 .009 E.004 E.003 E.003 <.02 <.032

 12471400 02-04-04 1350 .01 <.009 E.009 <.028 <.02 <.032

 12471400 04-07-04 1410 .011 E.004 <.006 <.028 <.02 <.032

 12471400 06-09-04 1310 .01 E.003 E.005 <.028 <.02 <.032

 12471400 07-08-04 1240 .011 E.004 E.005 <.028 <.02 <.032

 12471400 10-06-04 1410 .012 <.008 E.004 <.028 <.02 <.032

Red Rock Coulee

 12472520 07-29-02 1450 0.018 E0.011 E0.011 E0.008 <0.02 <0.032

 12472520 09-23-02 1310 .017 E.006 E.011 E.005 <.02 <.032

 12472520 02-04-03 1350 .019 .012 E.015 E.009 <.02 <.032

 12472520 04-09-03 1150 .021 E.008 E.015 E.007 <.02 <.032

 12472520 05-06-03 1310 .032 E.030 E.008 E.012 <.02 <.032

 12472520 07-02-03 1020 .019 .012 E.009 E.006 <.02 <.032

 12472520 02-04-04 0910 .018 E.006 E.013 <.028 <.02 <.032

 12472520 04-07-04 0910 .019 .011 E.011 <.028 <.02 <.032

 12472520 06-09-04 0810 .023 .011 E.011 <.028 <.02 <.032

 12472520 07-08-04 0830 .029 .017 E.010 E.007 <.02 <.032

 12472520 10-06-04 0930 .018 E.006 E.009 E.004 <.02 <.032

Sand Hollow

 12464606 07-29-02 1150 0.009 E0.005 E0.008 <0.005 <0.02 <0.032

 12464607 09-23-02 1100 .013 E.004 E.013 E.005 <.02 <.032

 12464607 02-04-03 1050 .029 .021 E.036 E.021 <.02 <.032

 12464607 04-07-03 1050 .008 <.009 E.005 E.004 <.02 <.032

 12464607 05-06-03 1010 <.007 E.005 <.006 E.006 <.02 <.032

 12464607 07-01-03 1020 .014 E.007 E.012 E.007 <.02 <.032

 12464607 10-06-03 1010 .01 E.005 E.005 E.006 <.02 <.032

 12464607 02-03-04 0920 .026 E.007 E.029 E.005 <.02 <.032

 12464607 04-06-04 0920 .013 E.004 E.009 E.005 <.02 <.032

 12464607 06-08-04 0840 .011 E.005 E.008 <.028 <.02 <.032

 12464607 07-07-04 0930 .01 E.005 E.008 <.028 <.02 <.032

 12464607 10-05-04 0930 .015 E.004 E.009 E.004 <.02 <.032

 Total sample 47 47 47

 Total < 2 3 46

 Total hits 41 29 0

 Negligent hit/miss 4 15 1

 Significant hits/miss 0 0 0

 Median percentage difference of hits 79 79

References Cited  51
Sampling site Date Time

Carbaryl Carbofuran Linuron Terbacil

GC/MS HPLC/MS GC/MS HPLC/MS GC/MS HPLC/MS GC/MS HPLC/MS

P82680 P49310 P82674 P49309 P82666 P38478 P82665 P04032

Crab Creek

 12472600 07-30-02 1020 E.005 <.03 <.020 <.006 <.035 <.01 <.034 <.010

 12472600 09-24-02 1100 <.041 <.03 <.020 <.006 <.035 <.01 <.034 <.010

 12472600 02-05-03 1120 <.041 <.03 <.020 <.006 <.035 <.01 <.034 <.010

 12472600 04-09-03 0930 <.041 <.03 <.020 <.006 <.035 <.01 E.061 E.031

 12472600 05-07-03 0940 <.041 <.03 <.020 <.006 <.035 <.01 E.033 E.025

 12472600 07-01-03 1400 <.041 <.03 <.020 <.006 <.035 <.01 E.026 <.010

 12472600 10-06-03 1350 <.041 <.03 <.020 <.006 <.035 <.01 <.034 E.006

 12472600 02-03-04 1330 <.041 <.03 <.020 <.006 <.035 <.01 <.034 <.010

 12472600 04-06-04 1310 <.041 <.03 <.020 <.006 <.035 <.01 E.016 <.010

 12472600 06-08-04 1250 <.041 <.03 <.020 <.006 E.013 <.01 E.021 <.010

 12472600 07-07-04 1320 E.009 <.03 <.020 <.006 <.035 <.01 E.021 <.010

 12472600 10-05-04 1310 <.041 <.02 <.020 <.016 <.035 <.01 <.034 <.016

Lind Coulee

 12471400 07-30-02 1345 <.041 <.03 <.020 <.006 <.035 <.01 <.034 <.010

 12471400 09-24-02 1400 <.041 <.03 <.020 <.006 E.006 <.01 <.034 <.010

 12471400 02-05-03 1440 <.041 <.03 <.020 <.006 <.035 <.01 <.034 <.010

 12471400 04-09-03 1520 <.041 <.03 <.020 <.006 <.035 <.01 <.034 <.010

 12471400 06-07-03 1320 <.041 <.03 <.020 <.006 <.035 <.01 <.034 <.010

 12471400 07-02-03 1430 <.041 <.03 <.020 <.006 <.035 <.01 <.034 <.010

 12471400 10-07-03 1440 <.041 <.03 <.020 <.006 <.035 <.01 <.034 <.010

 12471400 02-04-04 1350 <.041 <.03 <.020 <.006 <.035 <.01 <.034 <.010

 12471400 04-07-04 1410 <.041 <.03 <.020 <.006 <.035 <.01 <.034 <.010

 12471400 06-09-04 1310 <.041 <.03 <.020 <.006 E.013 <.01 <.034 <.010

 12471400 07-08-04 1240 <.041 <.03 <.020 <.006 <.035 <.01 <.034 <.010

 12471400 10-06-04 1410 <.041 <.02 <.020 <.016 <.035 <.01 <.034 <.016

Red Rock Coulee

 12472520 07-29-02 1450 <.041 <.03 <.020 <.006 <.035 <.01 <.034 <.010

 12472520 09-23-02 1310 <.041 <.03 <.020 <.006 <.035 <.01 E.014 <.010

 12472520 02-04-03 1350 <.041 <.03 <.020 <.006 <.035 E.01 <.034 E.005

 12472520 04-09-03 1150 <.041 <.03 <.020 <.006 <.035 <.01 E.044 E.020

 12472520 05-06-03 1310 <.041 <.03 <.020 <.006 <.035 <.01 E.075 E.090

 12472520 07-02-03 1020 <.041 <.03 <.020 <.006 <.035 <.01 E.020 E.010

 12472520 02-04-04 0910 <.041 <.03 <.020 <.006 <.035 <.01 <.034 E.006

 12472520 04-07-04 0910 <.041 <.03 <.020 <.006 <.035 <.01 E.040 <.027

 12472520 06-09-04 0810 <.041 <.03 <.020 <.006 E.014 <.01 E.050 <.010

 12472520 07-08-04 0830 <.041 <.03 <.020 <.006 <.035 <.01 E.011 <.010

 12472520 10-06-04 0930 <.041 <.02 <.020 <.016 <.035 <.01 <.034 <.016

Sand Hollow

 12464606 07-29-02 1150 E0.005 <0.03 <0.020 <0.006 <0.035 <0.01 E0.071 E0.042

 12464607 09-23-02 1100 <.041 <.03 <.020 <.006 <.035 <.01 E.106 .051

 12464607 02-04-03 1050 <.041 <.03 <.020 <.006 <.035 <.01 E.157 E.085

 12464607 04-07-03 1050 <.041 <.03 <.020 <.006 <.035 <.01 E1.01 E1.35

 12464607 05-06-03 1010 E.009 E.01 <.020 <.006 <.035 <.01 E.070 E.069

 12464607 07-01-03 1020 <.041 <.03 <.020 <.006 <.035 <.01 E.237 E.176

 12464607 10-06-03 1010 <.041 <.03 <.020 <.006 <.035 E.01 E.047 E.044

 12464607 02-03-04 0920 <.041 <.03 <.020 <.006 <.035 <.01 E.259 E.123

 12464607 04-06-04 0920 <.041 <.03 <.020 <.006 <.035 <.01 E.053 <.019

 12464607 06-08-04 0840 E.070 E.01 <.020 <.006 E.007 <.01 E.088 E.030

 12464607 07-07-04 0930 E.031 E.01 <.020 <.006 <.035 <.01 E.075 <.032

 12464607 10-05-04 0930 <.041 <.02 <.020 <.016 <.035 <.01 E.051 E.033

 Total sample 47 47 47 47

 Total < 41 47 40 19

 Total hits 3 0 0 15

 Negligent hit/miss 3 0 7 5

 Significant hits/miss 0 0 0 8

 Median percentage difference of hits 56 39

Table 18. Pesticide concentrations analyzed by gas chromatography/mass spectrometry and high-performance liquid chromatography/

mass spectrometry, Columbia Basin Project, Washington, July 2002 to October 2004.—Continued

[GC/MS, analysis by gas chromatography/mass spectrometry; HPLC/MS, analysis by high-performance liquid chromatography/mass 

spectrometry. Abbreviations: E, because recovery or variation in recovery was outside the acceptable range, compound is qualified with an E-code 

(estimated) or concentration reported is less than laboratory reporting level and is qualified as estimated; <, less than]

52 Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
Table 19. Registration status of pesticides analyzed, Columbia Basin Project, Washington, July 2002 to October 2004.

[Type of pesticide: F, fungicide; H, herbicide; I, insecticide; S, stimulant. Registered use: Home and (or) commercial]

Pesticide target 

analyte

Trade or common 

name(s)

Type of 

pesticide Registered use

2,4-D Weedon-2,4,-DP H Both

2,4-D methyl ester none H Both

2,4-DB none H Commercial

Acetochlor Acenit, Sacenid H Commercial

Acifluorfen Blazer, Tackle H Home

Alachlor Lasso H Commercial

Aldicarb Temik I Commercial

alpha-HCH none I Neither

Atrazine Aatrexx, Atratol H Both

Azinphos-methyl Guthion I Commercial

Bendiocarb Ficam I Both

Benfluralin Balan, Benefin H Both

Benomyl Benlate F Both

Bensulfuron-methyl Londax H Neither

Bentazon Adagio, Galaxy, Storm H Both

Bromacil Hyvar, Uragon H Both

Bromoxynil Buctril, Bromanil, Torch H Commercial

Butylate Sutran +, Genate Plus H Commercial

Caffeine none S Neither

Carbaryl Sevin, Savit I Both

Carbofuran Furadan I Commercial

Chloramben, methyl 

ester 

Amiben H Neither

Chlorimuron-ethyl Classic H Neither

Chlorothalonil Bravo, Forturf F Both

Chlorpyrifos Lorsban I Both

cis-Permethrin Ambush, Pounce I Both

Clopyralid Stinger, Lontrel H Both

Cyanazine Bladex H Commercial

Cycloate Ro-Neet, Marathon H Commercial

DCPA Dacthal H Commercial

Diazinon several I Both

Dicamba Banvel, Marksman, 

Clarity

H Both

Dichlorprop 2,4-DP, Weedon DP H Both

Dieldrin Panoram D-31 I Neither

Dinoseb DNBP, Caldon, 

Dynamite

H Neither

Diphenamid Rideon, Dymid, Enide H Neither

Disulfoton Di-Syston I Both

Diuron DCMU, Direx, Aguron H Both

EPTC Eptam, Eradicane H Both

Ethalfluralin Sonalan, Curbit EC H Commercial

Ethoprop Mocap I Commercial

Fenuron Beet-Kleen H Neither

Fipronil Regent I Both

Flumetsulam DE498, XRD 498 H Commercial

Fluometuron Cotoran, Lanex, 

Cottonex

H Neither

Fonos Dyfonate I Neither

gamma-HCH Lindane I Both

Pesticide target 

analyte

Trade or common 

name(s)

Type of 

pesticide Registered use

Imazaquin Skepter 1.5L, Image 

1.5LC

H Commercial

Imazethapyr Pursuit, Pursuit DG H Commercial

Imidacloprid Admire, Gaucho, Merit I Both

Linuron Lorox, Linex, Afalon H Commercial

Malathion several I Both

MCPA Metaxon, Border Master H Both

MCPB Troptox, Can-Trol H Commercial

Metalaxyl Apron, Subdue, Ridomil F Both

Methiocarb Draza, Mesurol I Commercial

Methomyl Lannate, Nudrin, Lanox I Both

Methyl parathion Penncap-M I Commercial

Metolachlor Dual, Pennant H Commercial

Metribuzin Lexone, Sencor H Commercial

Metsulfuron methyl Escort, Gropper, Ally H Commercial

Molinate Ordram H Neither

Napropamide Devrinol H Both

Neburon Granurex, Herbalt, 

Kloben

H Neither

Nicosulfuron Accent, Accent DF H Commercial

Norflurazon Zorial, Evital, Solicam H Commercial

Oryzalin Ryzelan, Surflan, 

Dirimal

H Both

Oxamyl Vydate: Thioxamyl I Commercial

Parathion several I Commercial

Pebulate Tillam H Commercial

Pendimethalin Prowl, Stomp H Both

Phorate Thimet, Rampart I Commercial

Picloram Tordon, Amdon, Grazon H Commercial

Prometon Pramitol H Both

Propachlor Ramrod H Commercial

Propanil Stampede H Neither

Propargite Comite, Omite I Commercial

Propham Chem-Hoe, IPC, 

Premalox

H Neither

Propiconazole Tilt, Orbit, Wocosin F Both

Propoxur Baygon, PHC, Suncide I Both

Propyzamide Kerb H Neither

Siduron Tupersan, Trey H Both

Simazine Aquazine, Princep H Both

Sulfometuron-methyl Oust, DPX-T5648 H Commercial

Tebuthiuron Graslan, Spike, Perflan H Commercial

Terbacil Sinbar, DPX-D732, 

Geonter

H Commercial

Terbufos Counter I Commercial

Thiobencarb Bolero H Neither

Triallate Far-Go H Commercial

Tribenuron-methyl Express, DPX-L5300 H Commercial

Triclopyr Garlon, Curtail, Redeem H Both

Trifluralin Treflan, Trilin H Both

References Cited  53
Table 20. Summary of pesticides not detected, Columbia Basin Project, Washington, July 2002 to October 2004.

[Type of pesticide: H, herbicide; I, insecticide; T, transformation product]

Pesticide target analyte Trade or common name(s) Type of 

pesticide

2,6-Diethylanaline none T

3(4-Chlorophenyl)-1-methyl 

urea 

none T

3-Hydroxycarbofuran none T

3-Ketocarbofuran none T

4,4’-DDE none T

Acetochlor Acenit, Sacenid H

Acifluorfen Blazer, Tackle H

Aldicarb Temik I

Aldicarb sulfone none T

Aldicarb sulfoxide none T

alpha-HCH none I

Bendiocarb Ficam I

Benfluralin Balan, Benefin H

Bensulfuron-methyl Londax H

Butylate Sutran +, Genate Plus H

Carbofuran Furadan I

Chloramben, methyl ester Amiben H

Chlorimuron-ethyl Classic H

cis-Permethrin Ambush, Pounce I

Cyanazine Bladex H

Cycloate Ro-Neet, Marathon H

Desulfinylfipronil none T

Desulfinylfipronil amide none T

Dichlorprop 2,4-DP, Weedon DP H

Dieldrin Panoram D-31 I

Disulfoton Di-Syston I

Fenuron Beet-Kleen H

Fipronil Regent I

Fipronil sulfide none T

Fipronil sulfone none T

Pesticide target analyte Trade or common name(s) Type of 

pesticide

Flumetsulam DE498, XRD 498 H

Fluometuron Cotoran, Lanex, Cottonex H

Fonos Dyfonate I

gamma-HCH Lindane I

Imazaquin Skepter 1.5L, Image 1.5LC H

Imazethapyr Pursuit, Pursuit DG H

Imidacloprid Admire, Gaucho, Merit I

MCPB Troptox, Can-Trol H

Methiocarb Draza, Mesurol I

Methyl parathion Penncap-M I

Metsulfuron methyl Escort, Gropper, Ally H

Molinate Ordram H

Napropamide Devrinol H

Neburon Granurex, Herbalt, Kloben H

Oryzalin Ryzelan, Surflan, Dirimal H

Parathion several I

Pebulate Tillam H

Phorate Thimet, Rampart I

Picloram Tordon, Amdon, Grazon H

Propachlor Ramrod H

Propanil Stampede H

Propargite Comite, Omite I

Propham Chem-Hoe, IPC, Premalox H

Propoxur Baygon, PHC, Suncide I

Propyzamide Kerb H

Siduron Tupersan, Trey H

Sulfometuron-methyl Oust, DPX-T5648 H

Tebuthiuron Spike H

Terbacil Sinbar H

Terbufos Counter I

Thiobencarb Bolero H

54 Pesticides in Agricultural Irrigation-Return Flow, Columbia Basin Project, Washington, 2002-04
Manuscript approved for publication, January 6, 2006

Prepared by the U.S. Geological Survey Publishing staff, 

Tacoma Publishing Services Center, 

Bill Gibbs 

Debra Grillo

Judy Wayenberg

Bobbie Jo Richey

For more information concerning the research in this report, contact the 

Director, Washington Water Science Center 

U.S. Geological Survey, 1201 Pacific Avenue – Suite 600 

Tacoma, Washington, 98402

http://wa.water.usgs.gov
SIR 2006 – 5005 Wagner and others

Printed on recycled paper

Occurrence, Distribution, and Transport of Pesticides in Agricultural Irrigation-Return Flow from Four 

Drainage Basins in the Columbia Basin Project, Washington, 2002-04, and Comparison with Historical Data