Prepared in cooperation with the Central Valley Regional Water Quality Control Board 

Detections of Current-Use Pesticides at 12 Surface Water 

Sites in California During a 2-Year Period Beginning in 2015 

Data Series 1088

U.S. Department of the Interior

U.S. Geological Survey
A

B

C

E

D

Cover photographs:

A, SNAKE R A NUESTRO RD NR SUTTER CA. Photo taken August 22, 2016, by Jim Orlando, 

USGS.

B, ALISAL C A LA GUARDIA ST NR SALINAS CA, view looking upstream. Photo taken 

April 28, 2016, by Jim Orlando, USGS.

C, INGRAM C A RIVER RD NR PATTERSON CA, looking downstream during storm runoff. 

Photo taken January 19, 2016, by Jim Orlando, USGS.

D, KINGS R A EMPIRE WEIR 2 A STRATFORD CA. Photo taken April 14, 2015, by Central 

Valley Regional Water Quality Control Board personnel.

E, UNNAMED TRIB TO ALDER C A IRON POINT RD NR FOLSOM CA, sampling storm 

runoff by USGS personnel. Photo taken November 2, 2015, by Jim Orlando, USGS.

See figure 1 for locations. 
Detections of Current-Use Pesticides 

at 12 Surface Water Sites in California 

During a 2-Year Period Beginning in 2015 

By Corey J. Sanders, James L. Orlando, and Michelle L. Hladik 

Prepared in cooperation with the Central Valley Regional Water Quality 

Control Board 

Data Series 1088 

U.S. Department of the Interior 

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

RYAN K. ZINKE, Secretary 

U.S. Geological Survey 

James F. Reilly II, Director 

U.S. Geological Survey, Reston, Virginia: 2018 

For more information on the USGS—the Federal source for science about the Earth, its natural and living 

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U.S. Government.

Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Sanders, C.J., Orlando, J.L., and Hladik, M.L., 2018, Detections of current-use pesticides at 12 surface water sites in 

California during a 2-year period beginning in 2015: U.S. Geological Survey Data Series 1088, 40 p., 

https://doi.org/10.3133/ds1088. 

ISSN 2327-638X (online)
iii

Acknowledgments 

The authors would like to thank Melissa Dekar formerly of the Central Valley Regional Water 

Quality Control Board for her work during the design phase of this project and for organizing the 

in-kind support of several water-quality monitoring groups.

The authors would also like to thank the Central Valley Regional Water Quality Control Board; 

San Francisco Bay Regional Water Quality Control Board; Central Coast Regional Water Quality Control Board; San Diego Regional Water Quality Control Board; California Department of 

Pesticide Regulation; Irrigated Lands Regulatory Program; and the University of California, Davis, 

for providing samples and in-kind support during this project. 
iv

Contents

Acknowledgments........................................................................................................................................iii

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

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

Purpose and Scope .............................................................................................................................1

Study Design .........................................................................................................................................1

Site Descriptions ..................................................................................................................................3

Agricultural Watersheds ...........................................................................................................3

Alisal Creek at La Guardia Street near Salinas, CA .....................................................3

French Camp Slough at Airport Way near Stockton, CA .............................................3

Ingram Creek at River Road near Patterson, CA ..........................................................5

Kings River at Empire Weir 2 at Stratford, CA ...............................................................5

Rainbow Creek at Huffstatler Street at Rainbow, CA ...................................................6

Snake River at Nuestro Road near Sutter, CA ...............................................................6

Urban Watersheds.......................................................................................................................6

Pleasant Grove Creek at Crocker Ranch Road near Roseville, CA............................6

Salt Creek at Niguel Road at Laguna Niguel, CA ..........................................................6

San Luis Obispo Creek at Los Osos Valley Road near San Luis Obispo, CA ............9

Stevens Creek at Barranca Drive at Monta Vista, CA .................................................9

Sweetwater River at Willow Street at Chula Vista, CA ................................................9

Unnamed Tributary to Alder Creek at Iron Point Road near Folsom, CA ..................9

Pesticide Use ......................................................................................................................................14

Hydrologic Conditions .......................................................................................................................14

Procedures and Methods ..........................................................................................................................14

Sample Collection ..............................................................................................................................14

Sample Processing and Analytical Methods ................................................................................14

High Performance Liquid Chromatography/Tandem Mass Spectrometry Analysis ......14

Gas Chromatography/Mass Spectrometry Analysis ...........................................................15

Quality-Control Methods and Results For Water and Suspended Sediment Samples ...................18

Results From Water Samples ....................................................................................................................20

Results from Suspended Sediment Samples .........................................................................................27

References Cited .........................................................................................................................................39

Figures

1. Map showing Twelve agricultural and urban surface water sites sampled

during 2015–17 in California ..........................................................................................................2

2. Photograph showing Alisal Creek at La Guardia Street near Salinas, CA, 

sampling site location ....................................................................................................................3

3. Photograph showing French Camp Slough at Airport Way near Stockton, CA,

sampling site location ....................................................................................................................3

4. Photograph showing Ingram Creek at River Road near Patterson, CA,

sampling site location ....................................................................................................................5

5. Photograph showing the Kings River at Empire Weir 2 at Stratford, CA,

sampling site location ....................................................................................................................5
v

6. Photograph showing the Rainbow Creek at Huffstatler Street at Rainbow, CA,

sampling site location ....................................................................................................................6

7. Photograph showing the Snake River at Nuestro Road near Sutter, CA,

sampling site location ....................................................................................................................6

8. Map and photograph showing the vView of Pleasant Grove Creek at Crocker

Ranch Road near Roseville, CA, watershed and sampling site location...............................7

9. Map and photograph showing the view of Salt Creek at Niguel Road at Laguna

Niguel, CA, watershed and sampling site location ...................................................................8

10. Map and photograph showing the view of San Luis Obispo Creek at Los Osos

Valley Road near San Luis Obispo, CA, watershed and sampling site location.................10

11. Map and photograph showing the view of Stevens Creek at Barranca Drive at

Monta Vista, CA, watershed and sampling site location .......................................................11

12. Map and photograph showing the view of Sweetwater River at Willow Street

at Chula Vista, CA, watershed and sampling site location ....................................................12

13. Map and photograph showing the view of Unnamed Tributary to Alder Creek at

Iron Point Road near Folsom, CA, watershed and sampling site location ..........................13

14. Graph showing number of pesticide detections in surface water samples from

agricultural sites over a U.S. Environmental Protection Agency aquatic life

benchmark value...........................................................................................................................23

15. Graph showing number of pesticide detections in surface water samples from

urban sites over a U.S. Environmental Protection Agency aquatic life

benchmark value...........................................................................................................................23

16. Graph showing dissolved concentrations of fipronil in urban sites, and

U.S. Environmental Protection Agency aquatic life benchmarks.........................................24

17. Graph showing dissolved concentrations of bifenthrin in agricultural sites, and

U.S. Environmental Protection Agency aquatic life benchmarks.........................................24

18. Graph showing dissolved concentrations of bifenthrin in urban sites, and

U.S. Environmental Protection Agency aquatic life benchmarks.........................................25

19. Graph showing dissolved concentrations of imidacloprid in agricultural sites,

and U.S. Environmental Protection Agency aquatic life benchmarks .................................25

20. Graph showing dissolved concentrations of imidacloprid in the agricultural site

Alisal Creek at La Guardia Street near Salinas, CA.,and U.S. Environmental

Protection Agency aquatic life benchmarks............................................................................26

21. Graph showing dissolved concentrations of imidacloprid in urban sites, and

U.S. Environmental Protection Agency aquatic life benchmarks.........................................26

Tables

1. Sampling site and watershed characteristics data ......................................................................4

2. Method detection limits for gas chromatography/mass spectrometry (GC/MS) and 

liquid chromatography/tandem mass spectrometry (LC/MS/MS) methods ......................16

3. Matrix-spike recoveries ..................................................................................................................18

4. Pesticide results in water samples from agricultural sites .......................................................20

5. Pesticide results in water samples from urban sites .................................................................20

6. Total number of detections in water samples from agricultural and urban sites ..................21

7. Pesticide results in suspended-sediment samples from agricultural sites ............................28

8. Pesticide results in suspended-sediment samples from urban sites ......................................35

9. Total number of detections in suspended-sediment samples from agricultural 

and urban sites .............................................................................................................................38
vi

Conversion Factors, Datums, and Water-Quality Units 

International System of Units to U.S. customery units

Multiply By To obtain

Length

millimeter (mm) 0.3937 inch (in.)

micrometer (μm) 3.937e−5 inch (in.)

meter (m) 3.281 foot (ft)

kilometer (km) 0.6214 mile (mi)

Area

square kilometer (km2) 0.3861 square mile (mi2)

Volume

microliter (μL) 3.3814e−5 ounce, fluid (fl. oz)

milliliter (mL) 0.033814 ounce, fluid (fl. oz)

liter (L) 33.814 ounce, fluid (fl. oz)

Flow rate

cubic meter per second (m3/s) 35.31 cubic foot per second (ft3/s)

milliliter per minute (mL/min) 3.53147e−5 cubic foot per minute (ft3/min)

Mass

kilogram (kg) 2.20462 pounds (lbs)

gram (g) 0.03527 ounce avoirdupois (oz)

milligram (mg) 3.527e−5 ounce avoirdupois (oz)

nanogram (ng) 3.527e−11 ounce avoirdupois (oz)

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

°F = (1.8 × °C) + 32. 

Supplemental Information 

Concentrations of chemical constituents in water and suspended sediment are given in 

nanograms per liter (ng/L). Suspended sediment samples are reported using the volume of 

water they are filtered from. (Each water sample is associated with a suspended sediment 

sample, and that volume of water is used to report both values.
vii

Abbreviations 

CDPR California Department of Pesticide Regulation

DCM dichloromethane

EPA U.S. Environmental Protection Agency

EtOAc ethyl acetate

GC/MS gas chromatography/mass spectrometry

LC/MS/MS liquid chromatography/tandem mass spectrometry

PFRG Pesticide Fate Research Group

QAPP Quality Assurance Project Plan

SPE solid phase extraction

USGS U.S. Geological Survey 
viii
Detections of Current-Use Pesticides at 12 Surface Water 

Sites in California During a 2-Year Period Beginning in 2015 

By Corey J. Sanders, James L. Orlando, and Michelle L. Hladik 

designations have prompted many studies of surface waters 

in California, and these studies have often shown an even 

greater need for further study in the region. A previous study 

by the California Department of Pesticide Regulation examined surface-water-quality monitoring data collected between 

1991 and 2010 for pesticides and compared these data to U.S. 

Environmental Protection Agency (EPA) aquatic life benchmarks. Numerous pesticides were detected in both agricultural 

and urban sites at concentrations above EPA benchmarks, 

including diazinon, chlorpyrifos, bifenthrin, and fipronil 

(Starner and Zhang, 2011). A more recent study, conducted 

over 2 years starting in 2012 by the U.S. Geological Survey 

(USGS) Pesticide Fate Research Group (PFRG), detected over 

30 pesticides in water samples from just two sites in California (Orlando and others, 2014). Studies such as these have 

shown the need for a project of larger scope, incorporating 

more sites and samples across a wider area of California (with 

equal representation of urban and agriculturally dominated 

watersheds) with analysis of more current-use pesticides. To 

address the identified needs, the USGS began the current study 

in cooperation with the Central Valley Regional Water Quality 

Control Board; San Francisco Bay Regional Water Quality 

Control Board; Central Coast Regional Water Quality Control 

Board; San Diego Regional Water Quality Control Board; 

California Department of Pesticide Regulation; Irrigated 

Lands Regulatory Program; and the University of California, 

Davis. This study sampled surface water from both urban and 

agricultural streams over a 2-year period starting in April of 

2015, and these water samples were analyzed for 157 pesticides and degradates by the USGS PFRG. 

Purpose and Scope 

This report details the study design, field and laboratory 

methods, and describes pesticide concentrations in surface 

water from both urban and agricultural sites across California 

during wet and dry seasons over a 2-year study period.

Study Design 

Surface water samples were collected from 12 sites 

throughout California. Sampling sites were chosen to be 

representative of either urban or agricultural land use (six sites 

Abstract 

Surface water samples were collected by the U.S. 

Geological Survey and multiple cooperators during base 

flow/irrigation runoff and storm runoff conditions from 

12 sites throughout California, over 2 consecutive years 

beginning in April 2015, from both urban and agriculturally 

dominated watersheds. Water samples were analyzed 

by gas chromatography/mass spectrometry and liquid 

chromatrography/tandem mass spectrometry for a suite 

of 157 pesticides and degradates. Suspended sediments 

associated with these water samples were analyzed by 

gas chromatography/mass spectrometry for a suite of 

131 pesticides and degradates. Overall, 85 pesticides and 

degradates were detected in the water: 32 fungicides, 

25 herbicides, 27 insecticides, and 1 synergist. In the 

suspended sediment, 29 pesticides were detected: 9 fungicides, 

10 herbicides, and 10 insecticides. Sixteen pesticides 

(bifenthrin, carbendazim, chlorpyrifos, clothianidin, diazinon, 

diuron, fenpyroximate, fipronil, fipronil sulfone, fluopicolide, 

imidacloprid, metolachlor, novaluron, oxyflurofen, permethrin, 

and simazine) were detected in the water at concentrations 

that were above at least one aquatic life benchmark value as 

defined by the U.S Environmental Protection Agency.

Introduction 

This study was designed to characterize the mixtures of a 

large suite of current-use pesticides and pesticide degradates 

in surface water and associated suspended sediments present 

in both agricultural and urban sites throughout California. 

Pesticides are used in California in both urban and agricultural 

settings and are routinely detected in surface water. In 2014, 

nearly 190 million pounds of pesticide active ingredients were 

reported as used in California (California Department of Pesticide Regulation, 2017). 

The California State Water Resources Control Board 

and Regional Water Quality Control Board have placed 

1,162 streams and rivers within California on the 303(d) list, 

indicating “impaired waters,” as designated under the Federal 

Clean Water Act. Of these, 290 are listed as impaired due to 

pesticides (State Water Resources Control Board, 2012). These 
2 Detections of Current-Use Pesticides at 12 Surface Water Sites in California During a 2-Year Period Beginning in 2015

Figure 1. Twelve agricultural and urban surface water sites sampled during 2015–17 in California.

Pacific Ocean

ALAMEDA

ALPINE

AMADOR

BUTTE

CALAVERAS

COLUSA

CONTRA

COSTA

DEL

NORTE

EL DORADO

FRESNO

GLENN

HUMBOLDT

IMPERIAL

INYO

KERN

KINGS

LAKE

LASSEN

LOS ANGELES

MADERA

MARIN

MARIPOSA

MENDOCINO

MERCED

MODOC

MONO

MONTEREY

NAPA

NEVADA

ORANGE

PLACER

PLUMAS

RIVERSIDE

SACRAMENTO

SAN

BENITO

SAN BERNARDINO

SAN DIEGO

SAN

JOAQUIN

SAN

LUIS

OBISPO

SAN

MATEO

SANTA

BARBARA

SANTA

CLARA

SANTA

CRUZ

SHASTA

SIERRA

SOLANO

SONOMA

STANISLAUS

SUTTER

TEHAMA

TRINITY

TULARE

TUOLUMNE

VENTURA

YOLO

YUBA

SISKIYOU

Central Valley

Central Valley

San Francisco Bay

Sacramento

River

San

Joaquin

River

River

American

Sacramento–

San Joaquin Delta

Sutter

Bypass

Salinas

Cupertino

Sutter

Stockton

French Camp San Francisco

Sacramento

San Luis Obispo

Chula Vista

San Diego

Folsom

Rainbow

120°

40°

115°

35°

0 25 75 150 MILES

0 25 50 75 100 125 150 KILOMETERS

50 100 125

Snake River at Nuestro Rd

near Sutter, CA

Pleasant Grove Creek at Crocker 

Ranch Rd near Roseville, CA

Unnamed Tributary to Alder Creek at 

Iron Point Rd near Folsom, CA

French Camp Slough at Airport Way near Stockton, CA

Stevens Creek at

 Barranca Dr at 

Monta Vista, CA

Ingram Creek at River Rd near Patterson, CA

Kings River at Empire Weir 2 at Stratford, CA

Alisal Creek at

 La Guardia St near 

Salinas, CA

San Luis Obispo Creek at Los Osos 

Valley Rd near San Luis Obispo, CA

Salt Creek at Niguel Rd at Laguna Niguel, CA Rainbow Creek at 

Huffstatler St at Rainbow, CA

Sweetwater River at Willow St at Chula Vista, CA NEVADA

CALIFORNIA

ARIZONA

MEXICO

OREGON

CA, California; Dr, Drive; Rd, Road; St, Street

EXPLANATION

Sampling site type

Agriculture

Urban

Albers Equal-Area Conic projection, North American Datum of 1983
Introduction 3

each; fig. 1). Initially, several State agencies that conduct 

water-quality monitoring were contacted (Department of Pesticide Regulation, Surface Water Ambient Monitoring Program, 

and various State Water Resources Control Board regional 

offices) to provide lists of sampling sites that were to be monitored for pesticides and toxicity in 2015 and 2016. These lists 

were then compiled and the final list of 12 sites selected based 

on the following criteria: (1) amount of urban or agricultural 

land use within the upstream watershed; (2) historical data, 

which indicated pesticide toxicity at the site; (3) 303(d) or 

other regulatory listings for the waterbody; and (4) recent 

pesticide usage data (table 1).

Just as the sites were chosen to be representative of both 

agricultural and urban sites, the sampling dates were chosen to 

be representative of both wet and dry seasons. Exact sample 

timing was at the discretion of the cooperating entity and coincided with either the collection of samples for other studies or 

long-term monitoring projects. The USGS PFRG provided all 

needed supplies to the cooperators. At several sites, toxicity 

samples were also collected in conjunction with the pesticide 

samples; however, these results are not the focus of this report 

and are therefore not included in this dataset.

Site Descriptions 

Sampling sites representative of either primarily 

agricultural or urban land uses (six sites each) were located 

throughout California (fig. 1). Agricultural sites were chosen 

to represent the wide variety of crops grown in California, 

whereas specific urban sites were chosen to represent varying 

degrees of age and density of urban development. In general, 

sampling sites were on small agricultural drainage channels 

or urban streams (channel capacities estimated to be less than 

250 cubic feet per second).

Agricultural Watersheds 

Alisal Creek at La Guardia Street near Salinas, CA 

Samples were collected from a manmade drainage channel 

in an area of intense agricultural land use (fig. 2). The site 

is on the eastern edge of the town of Salinas, California, 

upstream of any major urban land use (fig. 1), but does receive 

runoff from industrial farm produce-processing operations. 

The contributing watershed upstream of this site is just under 

40 square miles (mi2), and land use is approximately 30 

percent agricultural (National Land Cover Database, 2011; 

table 1). The primary crops grown in this watershed are 

strawberries and vegetables (U.S. Department of Agriculture, 

2016). Runoff passing this site eventually enters the Pacific 

Ocean through Elkhorn Slough at the Elkhorn Slough National 

Estuarine Research Reserve (not shown on fig. 1).

French Camp Slough at Airport Way near Stockton, CA 

Samples were collected from a leveed channel near the 

town of French Camp, Calif. (fig. 3). The contributing watershed upstream of this site is approximately 385 mi2

 and drains 

primarily agricultural lands in the eastern parts of San Joaquin 

and Stanislaus Counties (fig. 1). Land use in the watershed is 

approximately 41 percent agricultural (National Land Cover 

Database, 2011; table 1). The primary crops grown in this 

watershed are almonds, walnuts, grapes, and alfalfa (U.S. 

Department of Agriculture, 2016). Approximately 5 miles (mi) 

downstream of the sampling site, French Camp Slough (not 

shown on fig. 1) drains into the San Joaquin River and the 

Sacramento–San Joaquin Delta.

Figure 2. Alisal Creek at La Guardia Street near Salinas, CA, 

sampling site location.

Photograph by Jim Orlando, U.S. Geological Survey, April 28, 2016

Figure 3. French Camp Slough at Airport Way near Stockton, CA, 

sampling site location.

Photograph by Jim Orlando, U.S. Geological Survey, July 12, 2016
4 Detections of Current-Use Pesticides at 12 Surface Water Sites in California During a 2-Year Period Beginning in 2015 Table 1. Sampling site and watershed characteristics data. [Data from U.S. Census Bureau, 2008, 2011. Horizontal datum is North American Datum of 1983. Abbreviations: CA, California; Dr, Drive; lbs, pounds; mi2, square mile; Rd, Road; St, Street; USGS, U.S. Geological Survey] USGS station number USGS station name Latitude Longitude Watershed area (mi2

)

Site 

type

Urban area 

(mi2

)

Agricultural area 

(mi2

)

Other area 

(mi2

)

363925121364701 Alisal Creek at La Guardia St near Salinas, CA 36.65694 –121.61306 37.7 Agricultural 4.0 11.1 22.5375252121145401 French Camp Slough at Airport Way near Stockton, CA 37.88104 –121.24939 385.1 Agricultural 17.7 156.8 210.6373747121125200 Ingram Creek at River Rd near Patterson, CA 37.60049 –121.22466 30.6 Agricultural 1.1 9.8 19.7361044119500101 Kings River at Empire Weir 2 at Stratford, CA 36.17889 –119.83361 1,989.8 Agricultural 35.4 201.5 1,752.8332455117090701 Rainbow Creek at Huffstatler St at Rainbow, CA 33.41528 –117.15194 6.8 Agricultural 1.3 0.2 5.3391107121421201 Snake River at Nuestro Rd near Sutter, CA 39.18528 –121.70333 48.5 Agricultural 2.2 36.3 10.0384755121205201 Pleasant Grove Creek at Crocker Ranch Rd near Roseville, CA 38.79861 –121.34778 16.6 Urban 12.9 0.6 3.1333018117423301 Salt Creek at Niguel Rd at Laguna Niguel, CA 33.50500 –117.70917 2.2 Urban 1.7 0.0 0.5351436120405201 San Luis Obispo Creek at Los Osos Valley Rd near San Luis Obispo, CA 35.24333 –120.68111 41.4 Urban 9.3 1.6 30.5372004122035201 Stevens Creek at Barranca Dr at Monta Vista, CA 37.33444 –122.06444 19.7 Urban 2.6 0.0 17.2323932117023201 Sweetwater River at Willow St at Chula Vista, CA 32.65861 –117.04222 206.2 Urban 50.3 0.4 155.5383844121084001 Unnamed Tributary to Alder Creek at Iron Point Rd near Folsom, CA 38.64556 –121.14444 0.4 Urban 0.4 0.0 0.0

USGS 

station number USGS station name

Urban 

area 

(percent)

Agricultural 

area

(percent)

Other 

area

(percent)

Population 2000 Population 2010 Population density 2010 (persons per mi2

)

Pesticide 

application 2014 

(lbs)

363925121364701 Alisal Creek at La Guardia St near Salinas, CA 10.7 29.6 59.7 1,054 947 25 133,927375252121145401 French Camp Slough at Airport Way near Stockton, CA 4.6 40.7 54.7 18,481 20,056 52 415,405373747121125200 Ingram Creek at River Rd near Patterson, CA 3.7 31.9 64.4 124 128 4 30,685361044119500101 Kings River at Empire Weir 2 at Stratford, CA 1.8 10.1 88.1 76,693 89,556 45 881,707332455117090701 Rainbow Creek at Huffstatler St at Rainbow, CA 19.3 2.7 78.0 593 699 103 2,027391107121421201 Snake River at Nuestro Rd near Sutter, CA 4.6 74.9 20.5 2,143 2,555 53 88,362384755121205201 Pleasant Grove Creek at Crocker Ranch Rd near Roseville, CA 77.7 3.9 18.4 20,580 50,993 3,075 6,238333018117423301 Salt Creek at Niguel Rd at Laguna Niguel, CA 77.8 0.0 22.3 10,965 10,711 4,913 684351436120405201 San Luis Obispo Creek at Los Osos Valley Rd near San Luis Obispo, CA 22.5 3.9 73.6 37,845 41,557 1,003 2,246372004122035201 Stevens Creek at Barranca Dr at Monta Vista, CA 12.9 0.0 87.0 6,334 6,725 341 1,176323932117023201 Sweetwater River at Willow St at Chula Vista, CA 24.4 0.2 75.4 159,977 168,081 815 17,957383844121084001 Unnamed Tributary to Alder Creek at Iron Point Rd near Folsom, CA 98.5 0.0 1.1 1,146 2,063 5,546 210
Introduction 5

Ingram Creek at River Road near Patterson, CA 

At this site, samples were collected from a small agricultural drainage ditch in western Stanislaus County (figs. 1, 4). 

The watershed for this site is approximately 31 mi2 and is 32 

percent agricultural (table 1). However, streamflow originating 

in the western uplands part of the watershed reaches the sampling site only during extremely high storm runoff conditions, 

which did not occur during the sampling period. Streamflow at 

the sampling site during the study period consisted primarily 

of surface runoff and subsurface tile drainage from adjacent 

agricultural lands. The effective watershed for this site is 

almost entirely agricultural, and the primary crops grown in 

this watershed are almonds, walnuts, beans, and tomatoes 

(U.S. Department of Agriculture, 2016. Approximately 2 mi 

downstream of the sampling site, Ingram Creek drains into the 

San Joaquin River, which then flows north to the Sacramento–

San Joaquin Delta.

Kings River at Empire Weir 2 at Stratford, CA 

Samples were collected at this site from a large manmade 

channel immediately upstream of an irrigation control structure (Empire Weir 2) on the Kings River in the southern part of 

California’s Central Valley (figs. 1, 5). The natural hydrology 

of this region has been extensively modified to provide water 

for irrigation and flood control (ECORP Consulting, 2007). 

As a result, inputs and diversions influencing streamflow at 

this sampling site vary throughout the year, which makes it 

difficult to determine sources of potential contaminants. Given 

those uncertainties, the potentially contributing watershed 

upstream of the sampling site is just under 2,000 mi2 (table 1). 

Despite the fact that this watershed is just over 10 percent 

agricultural, the regions immediately upstream of the sampling 

site are predominantly agricultural, which is why this site is 

categorized as such. The primary crops grown in this watershed are grapes, almonds, alfalfa, walnuts, oranges, pistachios, 

and cotton (U.S. Department of Agriculture, 2016).

Figure 4. Ingram Creek at River Road near Patterson, CA, 

sampling site location.

Photograph by Jim Orlando, U.S. Geological Survey, July 12, 2016

Figure 5. Kings River at Empire Weir 2 at Stratford, CA, sampling 

site location.

Photograph by Central Valley Regional Water Quality Control Board personnel, April 13, 2015
6 Detections of Current-Use Pesticides at 12 Surface Water Sites in California During a 2-Year Period Beginning in 2015

Rainbow Creek at Huffstatler Street at Rainbow, CA 

This site was specifically selected because it receives 

runoff from a large number of plant nursery operations (indoor 

and outdoor). Samples were collected at this site from a small 

concrete-lined channel near Rainbow, Calif. (fig. 6). The 

upstream watershed for this site is just under 7 mi2 (table 1). 

Land use in the watershed is classified as mostly urban; 

however, most of this built-up area consists of plant nursery 

facilities.

Figure 6. Rainbow Creek at Huffstatler Street at Rainbow, CA, 

sampling site location.

Photograph taken by Jim Orlando, U.S. Geological Survey, August 7, 2016

walnuts, and prunes (U.S. Department of Agriculture, 2016). 

Water passing this site eventually makes its way into the 

Sacramento–San Joaquin Delta via the Sacramento River and 

Sutter Bypass.

Figure 7. Snake River at Nuestro Road near Sutter, CA, sampling 

site location.

Photograph by Jim Orlando, U.S. Geological Survey, August 22, 2016

Urban Watersheds 

Pleasant Grove Creek at Crocker Ranch Road near 

Roseville, CA 

This sampling site is in a greenbelt area immediately 

downstream of a large residential area (fig. 8). The 

contributing watershed area is just over 16 mi2 and is nearly 

78 percent urban (table 1). Urbanization within this watershed 

is relatively recent with the population increasing by nearly 

150 percent from 2000 to 2010 (U.S. Census Bureau, 2008, 

2011; table 1). Population density based on the 2010 census 

data for this watershed is just over 3,000 persons per mi2. 

Water passing this site eventually makes its way into the 

Sacramento–San Joaquin Delta via the Sacramento River.

Salt Creek at Niguel Road at Laguna Niguel, CA 

This sampling site is in a greenbelt area immediately 

downstream of a large residential area in Orange County, 

Calif. (figs. 1, 9) The contributing watershed area is just under 

2 mi2 and is nearly 78 percent urban (table 1). Urbanization 

within this watershed occurred prior to 2000, and the population was nearly unchanged from 2000 to 2010 (U.S. Census 

Bureau, 2008, 2011; table 1). Population density based on the 

2010 census data for this watershed is nearly 5,000 persons 

per mi2. Water passing this site enters the Pacific Ocean 

approximately 2 mi downstream of the sampling site.

Snake River at Nuestro Road near Sutter, CA 

At this site, water samples were collected from an approximately 40-foot-wide agricultural drainage ditch near Sutter, 

Calif. (figs. 1, 7). The watershed for this site is just over 48 mi2

and consists primarily of agricultural lands (table 1). Streamflow at this site consists entirely of agricultural drainage water. 

The primary crops grown in this watershed are rice, almonds, 
Introduction 7

Figure 8. View of Pleasant Grove Creek at Crocker Ranch Road near Roseville, CA, watershed and sampling site location.

121°21' 121°18' 121°15'

38°48'

38°45'

38°42'

Pleasant Grove Creek

384755121205201

EXPLANATION

Urban sampling site

Watershed boundary

0 1 1.5

1.5

0.5 2 MILES 

0 0.5 1 2 KILOMETERS

Aerial imagery source is U.S. Department of Agriculture, 2016b

PhotoGraph by Jim Orlando, U.S. Geological Survey, April 6, 2016
8 Detections of Current-Use Pesticides at 12 Surface Water Sites in California During a 2-Year Period Beginning in 2015

117°43' 117°42' 117°41'

33°31'

33°30'

Unamed creek

Salt Creek

EXPLANATION

Urban sampling site

Watershed boundary

0 0.25 0.5 MILE

0 0.25 0.5 KILOMETER

Photograph by Jim Orlando, U.S. Geological Survey, August 7, 2016

333018117423301

Aerial imagery source is U.S. Department of Agriculture, 2016b

Figure 9. View of Salt Creek at Niguel Road at Laguna Niguel, CA, watershed and sampling site location.
Introduction 9

San Luis Obispo Creek at Los Osos Valley Road near San 

Luis Obispo, CA 

This sampling site is immediately downstream of the 

town of San Luis Obispo, Calif., and receives treated effluent 

from the city’s wastewater treatment facility (figs. 1, 10). The 

watershed upstream of this site is just over 41 mi2 and is about 

22 percent urban (table 1). Urbanization within this watershed 

occurred prior to 2000, and the population increased about 10 

percent from 2000 to 2010 (U.S. Census Bureau, 2008, 2011; 

table 1). Population density based on the 2010 census data for 

this watershed is 1,003 persons per mi2. Water passing this site 

enters the Pacific Ocean approximately 6.5 mi downstream of 

the sampling site.

Stevens Creek at Barranca Drive at Monta Vista, CA 

This sampling site is in the Monta Vista area in the city of 

Cupertino, Calif., at the southern end of San Francisco Bay 

(figs. 1, 11). The watershed upstream of this site is just under 

20 mi2 and is roughly 13 percent urban (table 1). Urbanization 

within this watershed occurred prior to 2000, and the population increased by slightly over 6 percent from 2000 to 2010 

(U.S. Census Bureau, 2008, 2011; table 1). Population density 

based on the 2010 census data for this watershed is 341 persons per mi2

. Streamflow at this site is regulated by discharge 

from Stevens Creek Reservoir, which is 3 mi upstream. This 

reservoir provides flood control and maintains minimum summertime flows in Stevens Creek. Approximately 7 mi downstream of the sampling site, water from Stevens Creek enters 

San Francisco Bay.

Sweetwater River at Willow Street at Chula Vista, CA 

This sampling site is immediately downstream of a 

municipal golf course within the city of Chula Vista, Calif., 

in southern California (figs. 1, 12). The potential watershed 

upstream of this site is just over 200 mi2 and is about 24 

percent urban (table 1). Urbanization within this watershed 

occurred prior to 2000, and the population increased by 5.1 

percent from 2000 to 2010 (U.S. Census Bureau, 2008, 2011; 

table 1). Population density based on the 2010 census data for 

this watershed is 815 persons per mi2. Streamflow at this site is 

regulated by Sweetwater Reservoir, which is 3.3 mi upstream. 

Water impounded in Sweetwater Reservoir is treated and 

used for public supply, and water has not been released to the 

Sweetwater River downstream of the dam since 1998. The 

Sweetwater Authority also operates an urban water-diversion 

system in the area, which is designed to capture urban 

(storm and low-flow) runoff and route it around Sweetwater 

Reservoir and into the river channel below the dam 

(Sweetwater Authority, 2017). Water passing the sampling 

site was therefore likely made up entirely of urban runoff, and 

the effective watershed during the study period likely was 

much smaller and more heavily urbanized than reported in 

table 1. Water passing this sampling site enters San Diego Bay 

approximately 5 mi downstream.

Unnamed Tributary to Alder Creek at Iron Point Road near 

Folsom, CA 

This sampling site is immediately downstream of a large 

residential area in the city of Folsom, Calif. (fig. 13). The 

contributing watershed is less than 0.5 mi2 and is over 98 

percent urban (table 1). Urbanization within this watershed 

is relatively recent with the population increasing by 80 

percent from 2000 to 2010 (U.S. Census Bureau, 2008, 2011; 

table 1). Population density based on the 2010 census data for 

this watershed is just over 2,000 persons per mi2. An urban 

runoff retention pond is less than half a mile upstream of the 

sampling site. During the study period, streamflow at this site 

was affected by mandated urban-water-use cutbacks, and in 

general, this site only had flowing water following rainfall 

events. Water passing this site eventually makes its way into 

the Sacramento–San Joaquin Delta via the American River 

followed by the Sacramento River.
10 Detections of Current-Use Pesticides at 12 Surface Water Sites in California During a 2-Year Period Beginning in 2015

Figure 10. View of San Luis Obispo Creek at Los Osos Valley Road near San Luis Obispo, CA, watershed and sampling site location.

120°45' 120°42' 120°39' 120°36'

35°21'

35°18'

35°15'

35°12'

San Luis Obispo Creek

351436120405201

San Luis Obispo Bay

San Luis Obispo

EXPLANATION

Urban sampling site

Watershed boundary

0 1 2 3 MILES

0 1 2 3 KILOMETERS

Photograph by Mary Hamilton, Central Coast Regional Water Quality Control Board, January 29, 2015

Aerial imagery source is U.S. Department of Agriculture, 2016b
Introduction 11

Figure 11. View of Stevens Creek at Barranca Drive at Monta Vista, CA, watershed and sampling site location.

37°21'

37°18'

37°15'

122°09' 122°06' 122°03'

Stevens Creek

372004122035201

Photograph by Kristina Yoshida, State Water Resources Control Board, March 24, 2016

Stevens Creek

Reservoir

EXPLANATION

Urban sampling site

Watershed boundary

0 1 1.5

1.5

0.5 2 MILES

0 0.5 1 2 KILOMETERS

Aerial imagery source is U.S. Department of Agriculture, 2016b
12 Detections of Current-Use Pesticides at 12 Surface Water Sites in California During a 2-Year Period Beginning in 2015

Figure 12. View of Sweetwater River at Willow Street at Chula Vista, CA, watershed and sampling site location.

117°00' 116°50' 116°40' 116°30'

33°10'

33°00'

32°50'

32°40' 323932117023201

San Diego Bay

Sweetwater Reservoir

Sweetwater River

EXPLANATION

Urban sampling site

Watershed boundary

0 2 4 6 8 10 MILES

0 2 4 6 8 10 KILOMETERS

Photograph by Helen Yu, State Water Resources Control Board, August 24, 2015

Aerial imagery source is U.S. Department of Agriculture, 2016b
Introduction 13

Figure 13. View of Unnamed Tributary to Alder Creek at Iron Point Road near Folsom, CA, watershed and sampling site location. 

121°09' 121°08'30" 121°08'

38°39'30"

38°39'

38°38'30"

38°38'

Unnamed tributary to Alder Creek

383844121084001Photograph by Matt De Parsia, U.S. Geological Survey, November 2, 2015

EXPLANATION

0 0.1 0.2 0.3 0.4 MILES

0 0.1 0.2 0.3 0.4 0.5 KILOMETERS

Urban sampling site

Watershed boundary

Aerial imagery source is U.S. Department of Agriculture, 2016b
14 Detections of Current-Use Pesticides at 12 Surface Water Sites in California During a 2-Year Period Beginning in 2015

Pesticide Use 

Since 1990, the California Department of Pesticide 

Regulation (CDPR) has had a full-use reporting system that 

requires pesticide applicators to provide detailed information 

on pesticide use. The CDPR system is the most comprehensive 

pesticide reporting system in the Nation, and these data are 

valuable in assessing trends in pesticide use, changes in application patterns, and potential for environmental contamination. The CDPR reporting system, however, does not contain 

information on pesticide applications made by homeowners 

using products purchased at retail stores, and this leads to an 

underestimation of pesticide use in urban areas. Synthetic 

organic pesticide application totals for 2015 (the latest year for 

which data are available) for the watersheds upstream of the 

sampling sites are reported in table 1 (California Department 

of Pesticide Regulation, 2017).

Hydrologic Conditions 

Pesticide transport is strongly affected by the spatial and 

temporal application of pesticides as well as by rainfall and 

streamflow. From April 2015 to January 2017, nearly all of 

California experienced some degree of drought conditions 

(average of 97.4 percent by area), with over one-third of the 

State on average (33.9 percent) experiencing exceptional 

drought conditions (National Integrated Drought Information 

System, 2017). These drought conditions led to mandated 

urban-water-use cutbacks throughout the State as well as 

major reductions in agricultural water supplies from State 

and Federal water projects. As a result, streamflow was likely 

affected at all sampling sites. Unfortunately, none of the sites 

had streamflow gages associated with them; thus, no quantitative comparisons can be made to characterize departures from 

long-term streamflow trends.

Procedures and Methods 

The USGS PFRG oversaw and coordinated the collection 

of the samples by the cooperators to ensure proper sampling 

methods and techniques. All sample processing and analysis 

was done by the USGS PFRG.

Sample Collection 

Samples were collected three times from each sampling 

location per year over a period of 2 years beginning April 

2015. At each sample-collection event, a minimum of 2 liters 

(L) of water was collected in two pre-cleaned and baked 1-L 

amber glass bottles. Additional bottles were collected for quality-control samples on a schedule determined by the USGS 

PFRG. A representative from each cooperating agency filled 

the provided 1-L bottles using a grab technique following 

(QAPP) Surface Water Ambient Monitoring Program protocols and the project-specific Quality Assurance Project Plan; 

State Water Resources Control Board, 2014). Samples were 

shipped overnight to the USGS Organic Chemistry Research 

Laboratory (OCRL) in chilled coolers (4 degrees Celsius [°C]) 

and were processed immediately upon receipt.

Sample Processing and Analytical Methods 

Prior to pesticide analysis, all water samples were filtered 

through pre-weighed, pre-combusted 0.7-micrometer (μm) 

nominal pore-size glass-fiber filters (Grade GF/F, Whatman, 

Piscataway, New Jersey) to remove suspended material. Filter 

papers containing suspended sediments were dried at room 

temperature overnight (in the dark), then stored in a freezer at 

−20 °C until extraction.

High Performance Liquid Chromatography/

Tandem Mass Spectrometry Analysis 

The extraction procedure and instrumental analysis method 

by liquid chromatography/tandem mass spectrometry (LC/

MS/MS) have been previously described in Hladik and 

Calhoun (2012). Filtered water samples were spiked with 

recovery surrogate standards, monuron (Chem Service, West 

Chester, Pennsylvania) and imidacloprid-d4 (Cambridge 

Isotope Laboratories, Andover, Massachusetts). Samples were 

loaded onto an Oasis hydrophilic-lipophilic balance (HLB) 

solid phase extraction (SPE) cartridge (6 milliliters, mL; 

500 milligrams, mg; Waters, Milford, Massachusetts) that had 

been cleaned with one column-volume of dichloromethane 

(DCM) followed by one column-volume of acetone and 

two column-volumes of deionized water prior to use. Water 

samples were pumped through the SPE cartridge at a flow 

rate of 10 milliliters per minute (mL/min); the SPE cartridge 

was dried under nitrogen until the SPE sorbent was dry. 

Analytes were eluted with 10 mL of 50:50 DCM:acetone. 

The eluent was evaporated to less than 0.5 mL using a gentle 

stream of dry nitrogen, solvent-exchanged into acetonitrile 

(ACN), and further evaporated to 0.2 mL. An internal standard 

(13C3-caffeine, Cambridge Isotope Laboratories) was then 

added (20 microliters [μL] of a 5-nanograms-per-microliter 

[ng/μL] solution). Sample extracts were stored in a freezer at 

−20 °C until analysis (up to 30 days).

Water extracts were analyzed on an Agilent (Palo Alto, 

Calif.) 1100 high performance liquid chromatography 

(HPLC) system coupled to a 6430 tandem mass spectrometry 

(MS) system with a Zorbax Eclipse XDB-C18 column 

(2.1 millimeters [mm] × 150 mm × 3.5 mm; Agilent). 

The column flow rate was 0.6 mL/min, and the column 

temperature was 30 °C. Data were collected in the multiplereaction-monitoring (MRM) mode. Additional instrument 

method details can be found in Hladik and Calhoun (2012).
Procedures and Methods 15

Gas Chromatography/Mass Spectrometry 

Analysis 

The extraction procedure and instrumental analysis method 

by gas chromatography mass spectrometry (GC/MS) have 

been previously described in Hladik and others (2008, 2009) 

and Hladik and McWayne (2012), respectively. Briefly, filtered 

water samples were spiked with a recovery surrogate standard 

consisting of 13C3-atrazine, d-triflurlalin, and 13C-fipronil 

(Cambridge Isotopes, Andover, Massachusetts). Samples were 

loaded onto an Oasis HLB SPE cartridge (6 mL, 500 mg; 

Waters, Milford, Massachusetts) that had been cleaned with 

two column-volumes of ethyl acetate (EtOAc) followed by 

two column-volumes of methanol (MeOH) and two columnvolumes of deionized water prior to use. Water samples 

were pumped through the SPE cartridge at a flow rate of 

10 mL/min; the SPE cartridges were dried under nitrogen until 

the SPE sorbent was dry. Following extraction, sodium sulfate 

was added to the sample bottle to remove any residual water, 

and the bottle was rinsed in triplicate with approximately 2 mL 

of DCM into a collection tube. The bottle rinse was concentrated to 1 mL under a gentle stream of nitrogen gas. The SPE 

cartridges were dried under nitrogen until the SPE sorbent was 

dry, and then analytes were eluted with 12 mL of EtOAc into 

the concentrator tube containing its bottle rinse. The combined bottle rinse and eluent mixture was evaporated to less 

than 0.2 mL using a gentle stream of dry nitrogen; 20 μL of 

a 10 ng/μL internal standard (deuterated polycyclic aromatic 

hydrocarbon compounds acenaphthene-d10, phenanthrene 

d-10, and pyrene-d10) was then added to the sample. Sample 

extracts were stored in a freezer at −20 °C until analysis (up to 

30 days).

Filter papers were cut up and placed in an Erlenmeyer flask 

and extracted twice with 50 mL of dichloromethane in a sonicator (Branson 5200; Danbury, Connecticut) for 15 minutes. 

The extract was filtered through sodium sulfate, reduced using 

a Zymark Turbovap II (Hopinkton, Maryland) to 0.5 mL, then 

solvent exchanged into EtOAc, and further evaporated to less 

than 0.2 mL using a gentle stream of dry nitrogen. Following the evaporation, 20 μL of a 10 ng/μL internal standard 

(deuterated polycyclic aromatic hydrocarbon compounds 

acenaphthene-d10, phenanthrene d-10, and pyrene-d10) was 

then added to the sample. Sample extracts were stored in a 

freezer at −20 °C until analysis (up to 30 days). 

Water and filter extracts were analyzed on an Agilent 

7890A GC chromatograph with an Agilent 5975C Inert XL 

EI mass-selective detector (MSD) system using a DB-5MS 

analytical column (30 meter [m] by 0.25 mm by 0.25 μm; 

Agilent, Palo Alto, Calif.) for separation using helium as the 

carrier gas. Data were collected in the selected-ion-monitoring 

mode. Additional details of the GC/MS method can be found 

in Hladik and others (2008, 2009).

Method detection limits for pesticide concentrations in 

water were validated in previous work (Hladik and others, 

2008; Hladik and Calhoun, 2012). Method detection limits for 

pesticide in the suspended sediment phase were validated in 

previous studies by Hladik and Kuivila (2009). Method detection limits are shown in table 2.
16 Detections of Current-Use Pesticides at 12 Surface Water Sites in California During a 2-Year Period Beginning in 2015

Pesticide NWIS 

parameter code

MDL 

(ng/L)

3,4-Dichloroaniline* 66584 3.2

3,4-Dichloroaniline 66584 8.3

3,5-Dichloroaniline 67536 7.6

Acetamiprid 68302 3.3

Acibenzolar-S-methyl 51849 3.0

Alachlor 65064 1.7

Allethrin 66586 1.0

Atrazine 65065 2.3

Azinphos-methyl 65066 9.4

Azinphos-methyl oxon 68211 9.4

Azoxystrobin 66589 3.1

Benefin (benfluralin) 51643 2.0

Bifenthrin 65067 0.7

Boscalid 67550 2.8

Bromoconazole 68315 3.2

Butralin 68545 2.6

Butylate 65068 1.8

Captan 68322 10.2

Carbaryl 65069 6.5

Carbendazim 68548 4.2

Carbofuran 65070 3.1

Chlorantraniliprole 51856 4.0

Chlorothalonil 65071 4.1

Chlorpyrifos 65072 2.1

Chlorpyrifos oxon 68216 5.0

Clomazone 67562 2.5

Clothianidin 68221 3.9

Coumaphos 51836 3.1

Cyantraniliprole 51862 4.2

Cyazofamid 51853 4.1

Cycloate 65073 1.1

Cyfluthrin 65074 1.0

Cyhalofop-butyl 68360 1.9

Cyhalothrin (all isomers) 68354 0.5

Cymoxanil 51861 3.9

Cypermethrin 65075 1.0

Cyproconazole 66593 4.7

Cyprodinil 67574 7.4

DCPA 65076 2.0

DCPMU 68231 3.5

DCPU 68226 3.4

Deltamethrin 65077 0.6

Table 2. Method detection limits for gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/tandem mass 

spectrometry (LC/MS/MS) methods.

[MDL, method detection limit; ng/L, nanogram per liter; NWIS, National Water Information System]

Pesticide NWIS 

parameter code

MDL 

(ng/L)

Desthio-prothioconazole 51865 3.0

Desulfinylfipronil 66607 1.6

Desulfinylfipronil amide 68570 3.2

Diazinon 65078 0.9

Diazoxon 68236 5.0

Difenoconazole 67582 10.5

Dimethomorph 68373 6.0

Dinotefuran 68379 4.5

Dithiopyr 51837 1.6

Diuron 66598 3.2

EPTC 65080 1.5

Esfenvalerate 65081 0.5

Ethaboxam 51855 3.8

Ethalfluralin 65082 3.0

Etofenprox 67604 2.2

Famoxadone 67609 2.5

Fenamidone 51848 5.1

Fenarimol 67613 6.5

Fenbuconazole 67618 5.2

Fenhexamid 67622 7.6

Fenpropathrin 65083 0.6

Fenpyroximate 51838 5.2

Fenthion 51839 5.5

Fipronil 66604 2.9

Fipronil sulfide 66610 1.8

Fipronil sulfone 66613 3.5

Flonicamid 51858 3.4

Fluazinam 67636 4.4

Fludioxonil 67640 7.3

Flufenacet 51840 4.7

Flumetralin 51841 5.8

Fluopicolide 51852 3.9

Fluopyram 52761 3.8

Flupyradifurone 52764 3.0

Fluoxastrobin 67645 9.5

Fluridone 51864 3.7

Flusilazole 67649 4.5

Flutolanil 51842 4.4

Flutriafol 67653 4.2

Fluxapyroxad 51851 4.8

Hexazinone 65085 8.4

Imazalil 67662 10.5
Procedures and Methods 17

Pesticide NWIS 

parameter code

MDL 

(ng/L)

Imidacloprid 68426 3.8

Indoxacarb 68627 4.9

Ipconazole 52762 7.8

Iprodione 66617 4.4

Kresoxim-methyl 67670 4.0

Malaoxon 68240 5.0

Malathion 65087 3.7

Mandipropamid 51854 3.3

Metalaxyl 68437 5.1

Metconazole 66620 5.2

Methidathion 65088 7.2

Methoprene 66623 6.4

Methoxyfenozide 68647 2.7

Methyl parathion 65089 3.4

Metolachlor 65090 1.5

Molinate 65091 3.2

Myclobutanil 66632 6.0

Napropamide 65092 8.2

Novaluron 68655 2.9

Oryzalin 68663 5.0

Oxadiazon 51843 2.1

Oxyfluorfen 65093 3.1

p,p’-DDD 65094 4.1

p,p’-DDE 65095 3.6

p,p’-DDT 65096 4.0

Paclobutrazol 51846 6.2

Pebulate 65097 2.3

Pendimethalin 65098 2.3

Penoxsulam 51863 3.5

Pentachloroanisole 66637 4.7

Pentachloronitrobenzene 66639 3.1

Penthiopyrad 52769 3.2

Permethrin 65099 0.6

Phenothrin 65100 1.0

Phosmet 65101 4.4

Picoxystrobin 51850 4.2

Piperonyl butoxide 65102 2.3

Table 2. Method detection limits for gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/tandem mass 

spectrometry (LC/MS/MS) methods.—Continued 

[MDL, method detection limit; ng/L, nanogram per liter; NWIS, National Water Information System]

Pesticide NWIS 

parameter code

MDL 

(ng/L)

Prodiamine 51844 5.2

Prometon 67702 2.5

Prometryn 65103 1.8

Propanil 66641 10.1

Propargite 68677 6.1

Propiconazole 66643 5.0

Propyzamide 67706 5.0

Pyraclostrobin 66646 2.9

Pyridaben 68682 5.4

Pyrimethanil 67717 4.1

Quinoxyfen 51847 3.3

Resmethrin 65104 1.0

Sedaxane 52648 5.2

Simazine 65105 5.0

Tau-fluvalinate 65106 0.7

Tebuconazole 66649 3.7

Tebupirimfos 68693 1.9

Tebupirimfos oxon 68694 2.8

Tefluthrin 67731 0.6

Tetraconazole 66654 5.6

Tetradifon 51651 3.8

Tetramethrin 66657 0.5

Thiabendazole 67161 3.6

Thiacloprid 68485 3.2

Thiamethoxam 68245 3.4

Thiazopyr 51845 4.1

Thiobencarb 65107 1.9

Tolfenpyrad 51866 2.9

Triadimefon 67741 8.9

Triadimenol 67746 8.0

Triallate 68710 2.4

Tribufos 68711 3.1

Trifloxystrobin 66660 4.7

Triflumizole 67753 6.1

Trifluralin 65108 2.1

Triticonazole 67758 6.9

Zoxamide 67768 3.5

*

Denotes MDL for compound in LC/MS/MS method.
18 Detections of Current-Use Pesticides at 12 Surface Water Sites in California During a 2-Year Period Beginning in 2015

Quality-Control Methods and Results 

for Water and Suspended Sediment 

Samples 

A QAPP was developed for this project, which dictated the 

quantity and types of quality-control samples collected. These 

samples consisted of trip blanks, environmental and field 

replicate pairs, and laboratory matrix spikes and matrix-spike 

replicate pairs, all of which were used to validate pesticide 

concentrations measured in water samples using GC/MS and 

LC/MS/MS and in the suspended sediment using GC/MS. 

Recovery of surrogates was also used to monitor the efficiency 

of each extraction, and all samples were within the control 

limit of 70–130 percent. 

Seven trip blanks (four analyzed by GC/MS and three 

analyzed by LC/MS/MS) were collected to verify the cleanliness of processing protocols and the absence of atmospheric 

contamination. Filters from the four trip blanks collected for 

GC/MS were also saved and analyzed as suspended sediment 

trip blanks. No pesticides were detected in any of the trip 

blanks.

Seven environmental and field-replicate sample pairs (four 

analyzed by GC/MS and three analyzed by LC/MS/MS) were 

collected to verify the accuracy of the method. Filters from 

the four replicate samples collected for GC/MS analysis were 

also saved and analyzed as suspended sediment replicates. All 

results from the environmental and field replicate sample pairs 

were within the 25 percent relative standard deviation dataquality objective. All compounds detected in the environmental samples were also detected in the field replicates.

Eight matrix-spike and matrix-spike-replicate pairs (four 

analyzed by GC/MS and four analyzed by LC/MS/MS) were 

collected to verify the recovery of the target analytes as well as 

the accuracy of the method. Filters from the four matrix-spike 

and matrix-spike-replicate pairs collected for GC/MS analysis 

were also saved and analyzed as suspended sediment matrix 

spikes and matrix-spike replicates. All compounds in each 

matrix-spike and matrix-spike-replicate pair were recovered 

within the control limit of 70–130 percent, and all results from 

each pair were within the 25 percent relative standard deviation data-quality objective (table 3).

Pesticide Minimum 

recovery

Maximum 

recovery

Median 

recovery

Relative 

standard

deviation

(percent)

3,4-Dichloroaniline 71.1 105.0 80.4 15

3,4-Dichloroaniline** 84.3 105.2 93.5 8

3,5-Dichloroaniline 73.3 108.9 86.8 15

Acetamiprid** 71.3 95.5 83.9 11

Acibenzolar-S-methyl 86.0 113.4 98.3 9

Alachlor 91.1 118.1 99.3 9

Allethrin 86.3 111.4 97.6 11

Atrazine 73.8 111.4 101.3 15

Azinphos methyl 87.6 112.9 99.4 9

Azinphos methyl oxon 68.2 107.8 86.5 16

Azoxystrobin 76.9 110.1 92.1 12

Benfluralin 71.4 104.9 85.5 12

Bifenthrin 81.0 93.2 89.5 5

Boscalid 85.3 110.2 97.2 10

Bromoconazole 88.8 127.1 95.7 14

Butralin 74.9 119.7 88.7 18

Butylate 74.8 103.0 84.0 13

Captan 75.2 105.7 97.9 12

Carbaryl 89.7 107.0 99.2 6

Carbendazim** 86.8 101.7 96.0 5

Carbofuran 87.9 127.9 101.7 13

Chlorantraniliprole** 86.8 107.8 97.5 7

Chlorothalonil 78.6 128.6 107.6 16

Pesticide Minimum 

recovery

Maximum 

recovery

Median 

recovery

Relative 

standard

deviation

(percent)

Chlorpyrifos 89.3 111.9 99.2 7

Chlorpyrifos oxon 71.6 113.7 103.2 18

Clomazone 74.8 118.2 108.4 16

Clothianidin** 82.0 100.4 92.3 7

Coumaphos 88.1 117.0 99.5 11

Cyantraniliprole** 94.3 116.6 103.9 7

Cyazofamid** 75.1 105.7 94.0 14

Cycloate 80.5 117.2 96.4 14

Cyfluthrin 101.6 118.4 107.8 5

Cyhalofop-butyl 84.4 108.9 94.9 8

Cyhalothrin 73.7 124.5 97.1 18

Cymoxanil** 70.4 105.0 83.1 14

Cypermethrin 79.5 110.7 105.8 13

Cyproconazole 90.6 114.8 99.0 8

Cyprodinil 82.5 115.4 97.2 12

DCPA 89.9 114.8 107.3 9

DCPMU 78.0 111.9 88.1 14 

DCPU 79.2 93.9 89.0 6 

Deltamethrin 92.4 112.9 102.9 6 

Desthio-prothioconazole** 89.3 121.6 94.2 13 

Desulfinylfipronil 78.6 108.5 96.4 11 

Desulfinylfipronil amide 81.4 98.5 90.5 7 

Diazinon 71.3 110.9 87.6 16 

Table 3. Matrix-spike recoveries.

[GC/MS, gas chromatography/mass spectrometry; LC/MS/MS, liquid chromatography/tandem mass spectrometry; ** denotes compounds in LC/MS/MS method, all other compounds 

in GC/MS method]
Quality-Control Methods and Results for Water and Suspended Sediment Samples 19

Pesticide Minimum 

recovery

Maximum 

recovery

Median 

recovery

Relative 

standard

deviation

(percent)

Diazoxon 77.8 107.4 86.8 12 

Difenconazole 77.2 122.0 103.5 19 

Dimethomorph 91.8 114.1 99.1 8 

Dinotefuran** 73.5 105.7 92.9 12 

Dithiopyr 97.9 119.4 106.4 7 

Diuron** 85.0 108.4 102.0 8 

EPTC 86.0 102.1 97.7 7 

Esfenvalerate 90.5 118.0 95.9 10 

Ethaboxam** 76.6 106.6 100.4 12 

Ethalfluralin 74.6 96.9 85.1 11 

Etofenprox 78.9 118.6 86.2 17 

Famoxadone 89.8 108.3 98.4 7 

Fenamidone 91.3 118.8 102.4 10 

Fenarimol 75.8 106.8 102.5 13 

Fenbuconazole 75.1 104.2 95.8 12 

Fenhexamide 82.5 102.8 88.7 9 

Fenpropathrin 75.8 96.7 91.4 8 

Fenpyroximate 76.5 92.9 86.6 7 

Fenthion 91.8 118.2 101.1 9 

Fipronil 82.5 102.2 90.9 9 

Fipronil sulfide 75.8 114.5 101.7 15 

Fipronil sulfone 78.2 116.7 96.3 14 

Flonicamid** 85.2 107.0 96.9 9 

Fluazinam 101.7 118.7 110.3 6 

Fludioxinil 86.0 97.9 91.7 4 

Flufenacet 92.7 126.6 102.9 11 

Flumetralin 76.2 121.1 81.3 19 

Fluopicolide 81.8 114.1 102.0 13 

Fluopyram 82.4 105.6 92.2 10 

Fluoxastrobin 72.7 116.0 95.1 16 

Flupyradifurone** 79.6 104.8 94.9 10 

Fluridone** 88.0 104.8 99.4 6 

Flusilazole 84.2 107.0 95.1 8 

Flutolanil 78.7 120.2 91.8 17 

Flutriafol 71.7 91.4 78.6 8 

Fluxapyroxad 90.2 121.3 102.0 11 

Hexazinone 96.1 110.7 102.2 5 

Imazalil 76.7 117.0 98.8 17 

Imidacloprid** 84.7 104.0 97.3 6 

Indoxacarb 85.0 102.7 91.4 6 

Ipconazole 78.2 104.7 95.6 10 

Iprodione 85.1 102.1 95.9 6 

Kresoxim-methyl 80.4 110.5 101.2 11 

Table 3. Matrix-spike recoveries—Continued 

[GC/MS, gas chromatography/mass spectrometry; LC/MS/MS, liquid chromatography/tandem mass spectrometry; ** denotes compounds in LC/MS/MS method, all other compounds 

in GC/MS method]

Pesticide Minimum 

recovery

Maximum 

recovery

Median 

recovery

Relative 

standard

deviation

(percent)

Malaoxon 89.0 115.4 100.0 9 

Malathion 90.4 105.5 101.4 5 

Mandipropamid** 92.1 102.9 98.7 3 

Metalaxyl 87.7 115.1 98.3 10 

Metconazole 96.8 117.3 108.9 7 

Methidathion 70.7 120.0 84.1 21 

Methoprene 80.2 110.4 95.3 12 

Methoxyfenozide** 91.2 110.2 98.1 7 

Methyl parathion 71.2 121.1 90.9 21 

Metolachlor 91.7 109.3 99.1 6 

Molinate 83.0 106.5 94.4 10 

Myclobutanil 82.8 110.8 89.8 9 

Napropamide 83.2 108.4 101.7 10 

Novaluron 70.7 79.2 75.5 4 

Oryzalin** 71.6 103.6 88.7 13 

Oxydiazon 80.4 108.9 95.4 13 

Oxyfluorfen 75.4 97.3 92.2 8 

p,p’-DDD 71.4 101.8 93.1 13 

p,p’-DDE 70.0 101.3 90.3 15 

p,p’-DDT 97.1 106.2 102.6 3 

Paclobutrazol 74.8 109.8 93.3 13 

Pebulate 88.6 104.4 97.2 6 

Pendimethalin 84.4 119.1 94.6 13 

Penoxsulam** 85.5 98.0 91.8 4 

Pentachloroanisole 72.1 90.6 76.4 9 

Pentachloronitro-benzene 91.9 120.8 105.2 11 

Penthiopyrad** 72.4 111.5 105.8 15 

Permethrin 84.0 110.0 94.4 10 

Phenothrin 89.5 101.4 98.8 4 

Phosmet 78.7 111.5 91.9 14 

Picoxystrobin 84.0 111.2 95.2 11 

Piperonyl butoxide 77.7 118.8 94.2 15 

Prodiamine 77.4 107.6 99.6 12 

Prometon 72.6 119.7 86.2 20 

Prometryn 71.2 113.2 80.6 19 

Propanil 70.2 104.6 97.4 15 

Propargite 88.1 99.9 93.9 4 

Propiconazole 78.5 95.4 90.2 7 

Propyzamide 77.7 105.2 93.4 11 

Pyraclostrobin 78.0 96.7 87.1 8 

Pyridaben 83.4 116.7 97.0 11 

Pyrimethanil 80.6 123.0 97.9 15 

Quinoxyfen 88.3 114.0 105.8 8 
20 Detections of Current-Use Pesticides at 12 Surface Water Sites in California During a 2-Year Period Beginning in 2015

Pesticide Minimum 

recovery

Maximum 

recovery

Median 

recovery

Relative 

standard

deviation

(percent)

Resmethrin 92.7 117.9 100.9 8 

Sedaxane 80.1 110.6 92.1 12 

Simazine 84.4 109.8 103.2 10 

tau-Fluvalinate 83.9 117.5 102.3 11 

Tebuconazole 74.1 125.4 114.5 19 

Tebupirimfos 77.9 113.6 100.2 15 

Tebupirimfos oxon 84.6 112.2 102.1 11 

Tefluthrin 85.7 117.9 94.6 13 

Tetraconazole 78.3 111.2 97.0 13 

Tetradifon 87.8 107.9 99.1 6 

Tetramethrin 77.3 107.0 97.7 11 

Thiabendazole** 83.0 92.4 87.5 3 

Thiacloprid** 73.1 88.0 82.0 6 

Pesticide Minimum 

recovery

Maximum 

recovery

Median 

recovery

Relative 

standard

deviation

(percent)

Thiamethoxam** 75.2 106.6 87.0 13 

Thiazopyr 91.2 112.5 102.9 8 

Thiobencarb 90.5 111.1 95.4 8 

Tolfenpyrad** 80.2 104.4 93.8 11 

Triadimefon 79.9 103.3 90.2 9 

Triadimenol 76.4 111.4 80.6 16 

Triallate 77.3 115.7 101.2 15 

Tribufos 87.6 101.4 95.8 5 

Trifloxystrobin 86.2 108.9 104.1 9 

Triflumizole 89.4 106.3 97.6 6 

Trifluralin 73.8 108.8 88.1 13 

Triticonazole 73.8 110.2 92.2 16 

Zoxamide 91.4 107.5 103.0 6 

Table 3. Matrix-spike recoveries—Continued 

[GC/MS, gas chromatography/mass spectrometry; LC/MS/MS, liquid chromatography/tandem mass spectrometry; ** denotes compounds in LC/MS/MS method, all other compounds 

in GC/MS method]

Results From Water Samples 

Over the duration of the study, 85 pesticides and 

degradates were detected in the water (dissolved phase): 

32 fungicides, 25 herbicides, 27 insecticides, and 1 synergist 

(tables 4, 5). All but two samples contained mixtures of 

multiple pesticides, and the greatest number of pesticides 

detected in a single sample was 45 (Alisal Creek at La Guardia 

Street near Salinas, CA, collected December 15, 2015). The 

most frequently detected pesticides overall were diuron (75 

percent, herbicide), boscalid (75 percent, fungicide), and 

imidacloprid (69 percent, neonicotinoid insecticide; table 6).

Table 4. Pesticide results in water samples from agricultural 

sites.

This table is distributed as part of this report in Microsoft 

Excel 2010 format and is available for download at

https://doi.org/10.3133/ds1088.

Table 5. Pesticide results in water samples from urban sites.

This table is distributed as part of this report in Microsoft 

Excel 2010 format and is available for download at

https://doi.org/10.3133/ds1088.

Out of 36 water samples from agricultural sites, all samples 

contained between 3 and 45 pesticides, with an average of 

20 pesticides detected per sample (table 4). Out of 752 total 

detections in samples from agricultural sites, 36 percent were 

fungicides, 38 percent were herbicides/herbicide degradates, 

and 26 percent were insecticides/insecticide degradates 

(table 6).

Out of 36 water samples from urban sites, 35 had between 

1 and 25 pesticides detected, with an average of 12 pesticides 

detected per sample (table 5). One sample had no pesticide 

detections (Stevens Creek at Barranca Drive at Monta Vista, 

CA, collected January 3, 2017). Out of 426 total pesticide 

detections in samples from urban sites, 20 percent were fungicides, 34 percent were herbicides/herbicide degradates, and 46 

percent were insecticides/insecticide degradates (table 6).

In addition, 16 pesticides (bifenthrin, carbendazim, 

chlorpyrifos, clothianidin, diazinon, diuron, fenpyroximate, 

fipronil, fipronil sulfone, fluopicolide, imidacloprid, metolachlor, novaluron, oxyflurofen, permethrin, and simazine) were 

detected in the water at concentrations that were above at least 

one aquatic life benchmark value (figs. 14, 15) as defined by 

the EPA (U.S. Environmental Protection Agency, 2017). These 

concentrations were detected most frequently in urban-dominated watersheds, with at least 1 detection over an aquatic life 

benchmark in 23 out of the 36 urban samples. In the agriculturally dominated watersheds, 19 out of the 36 samples were 

found to have at least 1 detection over an aquatic life benchmark; however, these detections consisted of a larger variety 

of pesticides than those found in the urban samples. Of the 16 

pesticides detected at concentrations above aquatic life benchmarks, 12 of them (carbendazim, chlorpyrifos, clothianidin, 

diazinon, diuron, fenpyroximate, fluopicolide, metolachlor, 

novaluron, oxyflurofen, permethrin, and simazine) were found 

to exceed benchmarks primarily in the agricultural samples. 

Fipronil and fipronil sulfone were detected above aquatic life 

benchmark concentrations exclusively in urban sites, and 

bifenthrin and imidacloprid were detected in both urban and 

agricultural sites at concentrations above an aquatic life benchmark (figs. 16–21).
Results From Water Samples 21

Table 6. Total number of detections in water samples from agricultural and urban sites.

[*, fungicide; **, insecticide degradate; ***, herbicide degradate;  , synergist]

Pesticide

Agricultural sites Urban sites Total

Detections Detection frequency

(percent) Detections Detection frequency(percent) Detections Detection frequency(percent)

3,4-Dichloroaniline** * 25 69 14 39 39 54

3,5-Dichloroaniline*** 6 17 1 3 7 10

Acetamiprid** 9 25 0 0 9 13

Atrazine*** 1 3 0 0 1 1

Azoxystrobin* 28 78 6 17 34 47

Bifenthrin** 5 14 9 25 14 19

Boscalid* 32 89 22 61 54 75

Carbaryl** 6 17 3 8 9 13

Carbendazim* 20 56 21 58 41 57

Chlorantraniliprole** 26 72 13 36 39 54

Chlorothalonil* 3 8 4 11 7 10

Chlorpyrifos** 3 8 0 0 3 4

Clomazone*** 5 14 0 0 5 7

Clothianidin** 20 56 7 19 27 38

Cyantraniliprole** 6 17 0 0 6 8

Cyazofamid* 1 3 0 0 1 1

Cyprodinil* 15 42 3 8 18 25

DCPA*** 8 22 2 6 10 14

DCPMU*** 27 75 18 50 45 63

DCPU*** 11 31 13 36 24 33

Desulfinylfipronil** 1 3 23 64 24 33

Desulfinylfipronilamide ** 0 0 16 44 16 22

Diazinon** 4 11 1 3 5 7

Difenconazole* 5 14 0 0 5 7

Dimethomorph* 9 25 1 3 10 14

Dinotefuran** 13 36 15 42 28 39

Dithiopyr*** 16 44 21 58 37 51

Diuron*** 27 75 27 75 54 75

Fenamidone* 6 17 0 0 6 8

Fenhexamid* 3 8 2 6 5 7

Fenpyroximate** 2 6 1 3 3 4

Fipronil** 1 3 19 53 20 28

Fipronil sulfide** 1 3 23 64 24 33

Fipronil sulfone** 1 3 21 58 22 31

Flonicamid** 8 22 0 0 8 11

Fluazinam* 1 3 0 0 1 1

Fludioxonil* 6 17 0 0 6 8

Fluopicolide* 6 17 0 0 6 8

Fluopyram* 9 25 0 0 9 13

Flupyradifurone** 5 14 0 0 5 7

Fluridone*** 5 14 3 8 8 11

Flutolanil* 0 0 2 6 2 3

Fluxapyroxad* 20 56 1 3 21 29

Hexazinone*** 16 44 0 0 16 22
22 Detections of Current-Use Pesticides at 12 Surface Water Sites in California During a 2-Year Period Beginning in 2015

Pesticide

Agricultural sites Urban sites Total

Detections Detection frequency

(percent) Detections Detection frequency(percent) Detections Detection frequency(percent)

Imidacloprid** 24 67 26 72 50 69

Iprodione* 6 17 4 11 10 14

Mandipropamid* 9 25 0 0 9 13

Metalaxyl* 13 36 0 0 13 18

Metconazole* 1 3 0 0 1 1

Methoprene** 0 0 3 8 3 4

Methoxyfenozide** 26 72 10 28 36 50

Metolachlor*** 15 42 4 11 19 26

Myclobutanil* 16 44 0 0 16 22

Napropamide*** 6 17 0 0 6 8

Novaluron** 1 3 0 0 1 1

Oryzalin*** 17 47 4 11 21 29

Oxydiazon*** 10 28 16 44 26 36

Oxyfluorfen*** 23 64 1 3 24 33

p,p’-DDD** 3 8 0 0 3 4

p,p’-DDE** 6 17 0 0 6 8

p,p’-DDT** 1 3 0 0 1 1

Paclobutrazol* 1 3 0 0 1 1

Pendimethalin*** 13 36 6 17 19 26

Penoxsulam*** 6 17 2 6 8 11

Penthiopyrad* 6 17 0 0 6 8

Permethrin** 2 6 0 0 2 3

Piperonyl butoxide  7 19 1 3 8 11

Prodiamine** * 6 17 5 14 11 15

Prometryn*** 7 19 0 0 7 10

Propanil*** 2 6 0 0 2 3

Propargite** 2 6 0 0 2 3

Propiconazole* 26 72 8 22 34 47

Propyzamide*** 6 17 0 0 6 8

Pyrimethanil* 8 22 2 6 10 14

Quinoxyfen* 1 3 0 0 1 1

Simazine*** 21 58 6 17 27 38

Tebuconazole* 3 8 3 8 6 8

Tetraconazole* 5 14 1 3 6 8

Thiabendazole* 0 0 6 17 6 8

Thiamethoxam** 16 44 6 17 22 31

Thiobencarb*** 3 8 0 0 3 4

Triadimefon* 3 8 0 0 3 4

Triadimenol* 4 11 0 0 4 6

Trifloxystrobin* 4 11 0 0 4 6

Trifluralin*** 1 3 0 0 1 1

Table 6. Total number of detections in water samples from agricultural and urban sites.—Continued 

[*, fungicide; **, insecticide; ***, herbicide; ****, synergist]
Results From Water Samples 23

Figure 14. Number of pesticide detections in surface water samples from agricultural sites over a U.S. Environmental Protection 

Agency aquatic life benchmark value. Number of detections

0

4

8

12

16

20

2

6

10

14

18

Bifenthrin

Carbendazim 

Chlorpyrifos

Clothianidin 

Diazinon 

Diuron

Fenpyroximate

Fluopicolide

Imidacloprid 

Metolachlor 

Novaluron

Oxyfluorfen 

Permethrin 

Simazine

Fungicides

Insecticides

Herbicides

Figure 15. Number of pesticide detections in surface water samples from urban sites over a U.S. Environmental Protection Agency 

aquatic life benchmark value.

Bifenthrin Fipronil Fipronil sulfone

Number of detections

0

5

10

15

20

25

Imidacloprid
24 Detections of Current-Use Pesticides at 12 Surface Water Sites in California During a 2-Year Period Beginning in 2015

Figure 17. Dissolved concentrations of bifenthrin in agricultural sites, and U.S. Environmental Protection Agency aquatic life 

benchmarks.

Unnamed tributary to 

Alder Creek at Iron Point Rd 

near Folsom, CA

Pleasant Grove Creek at 

Crocker Ranch Rd 

near Roseville, CA

Salt Creek at Niguel Rd 

at Laguna Niguel, CA

San Luis Obispo Creek at 

Los Osos Valley Rd near 

San Luis Obispo, CA

Stevens Creek at 

Barranca Dr at

Monta Vista, CA

Sweetwater River at 

Willow St at

Chula Vista, CA

April 2015–December 2016 June 2015–October 2016 May 2015–November 2016 May 2015–August 2016 August 2015–January 2017 August 2015–December 2016

Acute toxicity for invertebrates (110 ng/L)

Chronic toxicity for invertebrates (11 ng/L)

0

20

40

60

80

100

120

140

Fipronil concentrations, in nanograms per liter (ng/L)

Storm events

Dry events

CA, California; Dr, Drive; 

Rd, Road; St, Street

Kings River at

Empire Weir 2 at

Stratford, CA

French Camp Slough at

Airport Way

near Stockton, CA

Ingram Creek at River Rd

near Patterson, CA

Snake River at Nuestro Rd

near Sutter, CA

Rainbow Creek at

Huffstatler St at

Rainbow, CA

Alisal Creek at 

La Guardia St near

Salinas, CA

April 2015–November 2016 April 2015–September 2016 June 2015–January 2016 May 2015–November 2016 August 2015–December 2017 April 2015–January 2016

Chronic toxicity for invertebrates (1.3 ng/L)

Bifenthrin concentrations, in nanograms per liter (ng/L)

0

2

4

6

8

10

12

14

16

18

Storm events

Dry events

CA, California; Dr, Drive; 

Rd, Road; St, Street

Figure 16. Dissolved concentrations of fipronil in urban sites, and U.S. Environmental Protection Agency aquatic life benchmarks. 
Results From Water Samples 25

Figure 18. Dissolved concentrations of bifenthrin in urban sites, and U.S. Environmental Protection Agency aquatic life benchmarks.

Unnamed tributary to 

Alder Creek at Iron Point Rd 

near Folsom, CA

Pleasant Grove Creek at 

Crocker Ranch Rd 

near Roseville, CA

Salt Creek at Niguel Rd 

at Laguna Niguel, CA

San Luis Obispo Creek at 

Los Osos Valley Rd near 

San Luis Obispo, CA

Stevens Creek at 

Barranca Dr at

Monta Vista, CA

Sweetwater River at 

Willow St at

Chula Vista, CA

April 2015–December 2016 June 2015–October 2016 May 2015–November 2016 May 2015–August 2016 August 2015–January 2017 August 2015–December 2016

0

10

20

30

40

50

60

70

80

Bifenthrin concentrations, in nanograms per liter (ng/L)

Acute toxicity for fish (75 ng/L)

Chronic toxicity for fish (40 ng/L)

Chronic toxicity for invertebrates (1.3 ng/L)

Storm events

Dry events

CA, California; Dr, Drive; 

Rd, Road; St, Street

Figure 19. Dissolved concentrations of imidacloprid in agricultural sites, and U.S. Environmental Protection Agency aquatic life 

benchmarks.

0

50

100

150

200

250

Imidacloprid concentrations, in nanograms per liter (ng/L)

Chronic toxicity for invertebrates (10 ng/L)

Kings River at

Empire Weir 2 at

Stratford, CA

French Camp Slough at

Airport Way

near Stockton, CA

Ingram Creek at River Rd near Patterson, CASnake River at Nuestro Rd near Sutter, CARainbow Creek at

Huffstatler St at

Rainbow, CA

April 2015–November 2016 April 2015–September 2016 June 2015–January 2016 May 2015–November 2016 August 2015–December 2017

Storm events

Dry events

CA, California; Dr, Drive; 

Rd, Road; St, Street
26 Detections of Current-Use Pesticides at 12 Surface Water Sites in California During a 2-Year Period Beginning in 2015

Imidacloprid concentrations, in nanograms per liter (ng/L)

Chronic toxicity for

invertebrates (10 ng/L)

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

Acute toxicity for invertebrates (385 ng/L)

Alisal Creek at La Guardia St nr Salinas, CA

 April 2015–January 2017

Storm events

Dry events

CA, California; nr, near; 

St, Street

Figure 21. Dissolved concentrations of imidacloprid in urban sites, and U.S. Environmental Protection Agency aquatic life benchmarks.

Figure 20. Dissolved concentrations of imidacloprid in the agricultural site Alisal Creek at La Guardia Street near Salinas, CA.,and U.S. 

Environmental Protection Agency aquatic life benchmarks.

0

20

40

100

60

80

120

Imidacloprid concentrations, in nanograms per liter (ng/L)

Chronic toxicity for

invertebrates (10 ng/L)

Unnamed tributary to 

Alder Creek at Iron Point Rd 

near Folsom, CA

Pleasant Grove Creek at 

Crocker Ranch Rd 

near Roseville, CA

Salt Creek at Niguel Rd 

at Laguna Niguel, CA

San Luis Obispo Creek at 

Los Osos Valley Rd near 

San Luis Obispo, CA

Stevens Creek at 

Barranca Dr at

Monta Vista, CA

Sweetwater River at 

Willow St at

Chula Vista, CA

April 2015–December 2016 June 2015–October 2016 May 2015–November 2016 May 2015–August 2016 August 2015–January 2017 August 2015–December 2016

Storm events

Dry events

CA, California; Dr, Drive; 

Rd, Road; St, Street
Results From Suspended Sediment Samples 27

Results From Suspended Sediment 

Samples 

Over the duration of the study, 29 pesticides were detected 

in suspended sediment: 9 fungicides, 10 herbicides, and 

10 insecticides (tables 7, 8). The most frequently detected 

pesticides overall were bifenthrin (51 percent, insecticide), 

oxyfluorofen (28 percent, herbicide), and p-p’-DDE (19 

percent, insecticide degradate).

Concentrations of pesticide compounds in suspendedsediments are provided in ng/L in tables 7 and 8 to facilitate 

the approximation of a whole-water pesticide concentration 

by summing the dissolved and suspended-sediment concentrations of pesticide compounds.

Out of 36 suspended sediment samples from agricultural 

sites, 27 had between 1 and 15 pesticides detected, with an 

average of 4 pesticides detected per sample (table 7). Nine 

samples had no pesticide detections. Out of 134 total pesticide 

detections in samples from agricultural sites, 17 percent were 

fungicides, 37 percent were herbicides, and 46 percent were 

insecticides (table 9).

Out of 36 suspended sediment samples from urban sites, 

16 had between 1 and 5 pesticides detected, with an average 

of 1 compound detected per sample (table 8). Twenty samples 
28 Detections of Current-Use Pesticides at 12 Surface Water Sites in California During a 2-Year Period Beginning in 2015 [All results in nanogram per liter (ng/L). Compounds analyzed for but not detected: 3,4-dichloroaniline, 3,5-dichloroaniline, acetamiprid, acibenzolar-S-methyl, alachlor, allethrin, atrazine, azinphos-methyl, azinphos-methyl oxon, benefin (benfluralin), bromoconazole, butralin, butylate, captan, carbaryl, carbendazim, carbofuran, chlorantraniliprole, chlorpyrifos, chlorpyrifos oxon, clothianidin, coumaphos, cyantraniliprole, cyazofamid, cycloate, cyfluthrin, cyhalofop-butyl, cymoxanil, cyproconazole, cyprodinil, DCPMU, DCPU, deltamethrin, desthio-prothioconazole, desulfinylfipronil, desulfinylfipronil amide, diazinon, diazoxon, difenoconazole, dimethomorph, dinotefuran, diuron, EPTC, esfenvaler- ate, ethaboxam, ethalfluralin, etofenprox, famoxadone, fenamidone, fenarimol, fenbuconazole, fenhexamid, fenpropathrin, fenpyroximate, fenthion, fipronil, fipronil sulfide, fipronil sulfone, flonicamid, fluazinam, flufenacet, flumetralin, fluopyram, flupyradifurone, fluoxastrobin, fluridone, flusilazole, flutolanil, flutriafol, hexazinone, imazalil, imidacloprid, indoxacarb, ipconazole, iprodione, kresoxim-methyl, malaoxon, malathion, mandipropamid, metconazole, methida- thion, methoprene, methoxyfenozide, methyl parathion, molinate, napropamide, novaluron, oryzalin, paclobutrazol, pebulate, penoxsulam, pentachloroanisole, pentachloronitrobenzene, penthiopyrad, phenothrin, phosmet, picoxystrobin, piperonyl butoxide, prometon, prometryn, propanil, propiconazole, pyraclostrobin, pyrimethanil, quinoxyfen, resmethrin, sedaxane, tebupirimfos, tebupirimfos oxon, tefluthrin, tetraconazole, tetradifon, tetramethrin, thiabendazole, thiaclo- prid, thiamethoxam, thiazopyr, thiobencarb, tolfenpyrad, triadimefon, triadimenol, triallate, tribufos, trifloxystrobin, triflumizole, trifluralin, triticonazole, zoxamide. Abbreviations: CA, California; g, gram; hh:mm, hour:minute; mm/dd/ yyyy, month/day/year; Rd, Road; St, Street; USGS, U.S. Geological Survey; —, nondetect] USGS site name USGS site number Date (mm/dd/yyyy) Time (hh:mm) Event Mass (g) Azoxys- trobin Bifenthrin Boscalid Chlorotha- lonil Clomazone Cyhalothrin Kings River at Empire Weir 2 at Stratford, CA 361044119500101 04/14/2015 09:25 Dry 0.065

—

—

—

—

—

—

Kings River at Empire Weir 2 at Stratford, CA 361044119500101 06/30/2015 11:41 Dry 0.036

—

—

—

—

—

—

Kings River at Empire Weir 2 at Stratford, CA 361044119500101 11/03/2015 11:41 Storm 0.102

— 61.6

—

—

—

—

Kings River at Empire Weir 2 at Stratford, CA 361044119500101 03/07/2016 10:40 Storm 0.071

— 2.2

—

—

—

—

Kings River at Empire Weir 2 at Stratford, CA 361044119500101 09/26/2016 11:05 Dry 0.065

— 4.0

—

—

—

—

Kings River at Empire Weir 2 at Stratford, CA 361044119500101 11/30/2016 10:45 Dry 0.088

—

—

—

—

—

—

French Camp Slough at Airport Way near Stockton, CA 375252121145401 04/21/2015 11:50 Dry 0.055

— 10.2

—

—

—

—

French Camp Slough at Airport Way near Stockton, CA 375252121145401 07/21/2015 12:40 Dry 0.028

— 5.0

—

—

—

—

French Camp Slough at Airport Way near Stockton, CA 375252121145401 01/06/2016 09:40 Storm 0.0117

—

—

—

—

—

—

French Camp Slough at Airport Way near Stockton, CA 375252121145401 03/07/2016 11:40 Storm 0.068

— 4.0

—

—

—

—

French Camp Slough at Airport Way near Stockton, CA 375252121145401 07/19/2016 12:20 Dry 0.012

—

—

—

—

—

—

French Camp Slough at Airport Way near Stockton, CA 375252121145401 09/20/2016 11:40 Dry 0.022

—

—

—

—

—

—

Ingram Creek at River Rd near Patterson, CA 373747121125200 06/09/2015 08:45 Dry 0.386

— 5.4

—

—

—

—

Ingram Creek at River Rd near Patterson, CA 373747121125200 09/15/2015 10:00 Dry 0.024

— 8.2

— 5.1

—

—

Ingram Creek at River Rd near Patterson, CA2 373747121125200 01/19/2016 13:20 Storm 0.616

— 133

— 38.0

—

—

Ingram Creek at River Rd near Patterson, CA 373747121125200 04/28/2016 16:05 Dry 0.235

— 6.0

—

—

—

—

Ingram Creek at River Rd near Patterson, CA 373747121125200 07/12/2016 13:30 Dry 0.423

— 18.3

—

—

—

—

Ingram Creek at River Rd near Patterson, CA 373747121125200 01/09/2017 12:40 Storm 0.083

— 24.0 50.3

—

—

—

Snake River at Nuestro Rd near Sutter, CA 391107121421201 05/20/2015 09:15 Dry 0.019

—

—

—

— 8.8

—

Snake River at Nuestro Rd near Sutter, CA 391107121421201 07/21/2015 14:00 Dry 0.031

—

—

—

—

—

—

Snake River at Nuestro Rd near Sutter, CA 391107121421201 03/08/2016 08:45 Storm 0.082

—

—

— 11.4

—

—

Snake River at Nuestro Rd near Sutter, CA 391107121421201 07/19/2016 11:15 Dry 0.037

—

—

—

—

—

—

Snake River at Nuestro Rd near Sutter, CA 391107121421201 08/16/2016 19:20 Dry 0.024

—

—

—

—

—

—

Snake River at Nuestro Rd near Sutter, CA 391107121421201 11/16/2016 16:10 Storm 0.428

—

—

—

—

—

—

Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 08/26/2015 10:30 Dry 0.219

— 60.9 15.5

—

—

—

Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 02/01/2016 12:35 Storm 0.010

— 1.2

—

—

—

—

Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 06/08/2016 12:00 Dry 0.048

—

—

—

—

—

—

Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 08/07/2016 11:00 Dry 0.018

—

—

—

—

—

—

Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 10/18/2016 11:30 Dry 0.041

— 7.5

—

—

—

—

Table 7. Pesticide results in suspended-sediment samples from agricultural sites. 
Results From Suspended Sediment Samples 29

[All results in nanogram per liter (ng/L). Compounds analyzed for but not detected: 3,4-dichloroaniline, 3,5-dichloroaniline, acetamiprid, acibenzolar-S-methyl, alachlor, allethrin, atrazine, azinphos-methyl, azinphos-methyl oxon, benefin (benfluralin), bromoconazole, butralin, butylate, captan, carbaryl, carbendazim, carbofuran, chlorantraniliprole, chlorpyrifos, chlorpyrifos oxon, clothianidin, coumaphos, cyantraniliprole, cyazofamid, cycloate, cyfluthrin, cyhalofop-butyl, cymoxanil, cyproconazole, cyprodinil, DCPMU, DCPU, deltamethrin, desthio-prothioconazole, desulfinylfipronil, desulfinylfipronil amide, diazinon, diazoxon, difenoconazole, dimethomorph, dinotefuran, diuron, EPTC, esfenvalerate, ethaboxam, ethalfluralin, etofenprox, famoxadone, fenamidone, fenarimol, fenbuconazole, fenhexamid, fenpropathrin, fenpyroximate, fenthion, fipronil, fipronil sulfide, fipronil sulfone, flonicamid, fluazinam, flufenacet, flumetralin, fluopyram, flupyradifurone, fluoxastrobin, fluridone, flusilazole, flutolanil, flutriafol, hexazinone, imazalil, imidacloprid, indoxacarb, ipconazole, iprodione, kresoxim-methyl, malaoxon, malathion, mandipropamid, metconazole, methidathion, methoprene, methoxyfenozide, methyl parathion, molinate, napropamide, novaluron, oryzalin, paclobutrazol, pebulate, penoxsulam, pentachloroanisole, pentachloronitrobenzene, penthiopyrad, phenothrin, phosmet, picoxystrobin, piperonyl butoxide, prometon, prometryn, propanil, propiconazole, pyraclostrobin, pyrimethanil, quinoxyfen, resmethrin, sedaxane, tebupirimfos, tebupirimfos oxon, tefluthrin, tetraconazole, tetradifon, tetramethrin, thiabendazole, thiacloprid, thiamethoxam, thiazopyr, thiobencarb, tolfenpyrad, triadimefon, triadimenol, triallate, tribufos, trifloxystrobin, triflumizole, trifluralin, triticonazole, zoxamide. Abbreviations: CA, California; g, gram; hh:mm, hour:minute; mm/dd/yyyy, month/day/year; Rd, Road; St, Street; USGS, U.S. Geological Survey; —, nondetect] 

USGS site name USGS site number Date (mm/dd/yyyy) Time (hh:mm) Event Mass (g) Azoxys- trobin Bifenthrin Boscalid Chlorotha- lonil Clomazone Cyhalothrin 

Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 12/19/2016 12:10 Storm 0.020 — 7.6 — — — —Alisal Creek at La Guardia St near Salinas, CA 363925121364701 04/29/2015 11:05 Dry 0.050 8.7 19.4 157 — — —Alisal Creek at La Guardia St near Salinas, CA 363925121364701 08/25/2015 13:00 Dry 0.150 19.8 5.9 158 — — —Alisal Creek at La Guardia St near Salinas, CA3 363925121364701 12/15/2015 12:30 Storm 0.173 — 62.4 59.2 — — —Alisal Creek at La Guardia St near Salinas, CA 363925121364701 04/28/2016 12:26 Dry 0.180 — 28.3 157 — — 110Alisal Creek at La Guardia St near Salinas, CA 363925121364701 09/28/2016 12:25 Dry 0.064 — 4.1 6.0 — — —Alisal Creek at La Guardia St near Salinas, CA4 363925121364701 01/12/2017 09:45 Storm 0.451 — 59.4 59.2 — — 41.5

USGS site name USGS site number Date (mm/dd/yyyy) Time (hh:mm) Event Cyperme- thrin DCPA Dithiopyr Fludioxinil Fluopicolide Fluxapy- roxad Metalaxyl 

Kings River at Empire Weir 2 at Stratford, CA 361044119500101 04/14/2015 09:25 Dry — — — — — — —Kings River at Empire Weir 2 at Stratford, CA 361044119500101 06/30/2015 11:41 Dry — — — — — — —Kings River at Empire Weir 2 at Stratford, CA 361044119500101 11/03/2015 11:41 Storm — — — — — — —Kings River at Empire Weir 2 at Stratford, CA 361044119500101 03/07/2016 10:40 Storm — — — — — — —Kings River at Empire Weir 2 at Stratford, CA 361044119500101 09/26/2016 11:05 Dry — — — — — — —Kings River at Empire Weir 2 at Stratford, CA 361044119500101 11/30/2016 10:45 Dry — — — — — — —French Camp Slough at Airport Way near Stockton, CA 375252121145401 04/21/2015 11:50 Dry — — — — — — —French Camp Slough at Airport Way near Stockton, CA 375252121145401 07/21/2015 12:40 Dry — — — — — — —French Camp Slough at Airport Way near Stockton, CA 375252121145401 01/06/2016 09:40 Storm — — — — — — —French Camp Slough at Airport Way near Stockton, CA 375252121145401 03/07/2016 11:40 Storm — — 2.8 — — — —French Camp Slough at Airport Way near Stockton, CA 375252121145401 07/19/2016 12:20 Dry — — — — — — —French Camp Slough at Airport Way near Stockton, CA 375252121145401 09/20/2016 11:40 Dry — — — — — — —Ingram Creek at River Rd near Patterson, CA 373747121125200 06/09/2015 08:45 Dry — — — — — — —Ingram Creek at River Rd near Patterson, CA 373747121125200 09/15/2015 10:00 Dry — — — — — — —Ingram Creek at River Rd near Patterson, CA2 373747121125200 01/19/2016 13:20 Storm — — — — — — —Ingram Creek at River Rd near Patterson, CA 373747121125200 04/28/2016 16:05 Dry — — — — — — —Ingram Creek at River Rd near Patterson, CA 373747121125200 07/12/2016 13:30 Dry — — — — — — —Ingram Creek at River Rd near Patterson, CA 373747121125200 01/09/2017 12:40 Storm — — — — — — —Snake River at Nuestro Rd near Sutter, CA 391107121421201 05/20/2015 09:15 Dry — — — — — — —Snake River at Nuestro Rd near Sutter, CA 391107121421201 07/21/2015 14:00 Dry — — — — — — —

Table 7. Pesticide results in suspended-sediment samples from agricultural sites.—Continued 
30 Detections of Current-Use Pesticides at 12 Surface Water Sites in California During a 2-Year Period Beginning in 2015 Table 7. Pesticide results in suspended-sediment samples from agricultural sites.—Continued [All results in nanogram per liter (ng/L). Compounds analyzed for but not detected: 3,4-dichloroaniline, 3,5-dichloroaniline, acetamiprid, acibenzolar-S-methyl, alachlor, allethrin, atrazine, azinphos-methyl, azinphos-methyl oxon, benefin (benfluralin), bromoconazole, butralin, butylate, captan, carbaryl, carbendazim, carbofuran, chlorantraniliprole, chlorpyrifos, chlorpyrifos oxon, clothianidin, coumaphos, cyantraniliprole, cyazofamid, cycloate, cyfluthrin, cyhalofop-butyl, cymoxanil, cyproconazole, cyprodinil, DCPMU, DCPU, deltamethrin, desthio-prothioconazole, desulfinylfipronil, desulfinylfipronil amide, diazinon, diazoxon, difenoconazole, dimethomorph, dinotefuran, diuron, EPTC, esfenvalerate, ethaboxam, ethalfluralin, etofenprox, famoxadone, fenamidone, fenarimol, fenbuconazole, fenhexamid, fenpropathrin, fenpyroximate, fenthion, fipronil, fipronil sulfide, fipronil sulfone, flonicamid, fluazinam, flufenacet, flumetralin, fluopyram, flupyradifurone, fluoxastrobin, fluridone, flusilazole, flutolanil, flutriafol, hexazinone, imazalil, imidacloprid, indoxacarb, ipconazole, iprodione, kresoxim-methyl, malaoxon, malathion, mandipropamid, metconazole, methidathion, methoprene, methoxyfenozide, methyl parathion, molinate, napropamide, novaluron, oryzalin, paclobutrazol, pebulate, penoxsulam, pentachloroanisole, pentachloronitrobenzene, penthiopyrad, phenothrin, phosmet, picoxystrobin, piperonyl butoxide, prometon, prometryn, propanil, propiconazole, pyraclostrobin, pyrimethanil, quinoxyfen, resmethrin, sedaxane, tebupirimfos, tebupirimfos oxon, tefluthrin, tetraconazole, tetradifon, tetramethrin, thiabendazole, thiacloprid, thiamethoxam, thiazopyr, thiobencarb, tolfenpyrad, triadimefon, triadimenol, triallate, tribufos, trifloxystrobin, triflumizole, trifluralin, triticonazole, zoxamide. Abbreviations: CA, California; g, gram; hh:mm, hour:minute; mm/dd/yyyy, month/day/year; Rd, Road; St, Street; USGS, U.S. Geological Survey; —, nondetect] USGS site name USGS site number Date (mm/dd/yyyy) Time (hh:mm) Event Cyperme- thrin DCPA Dithiopyr Fludioxinil Fluopicolide Fluxapy- roxad Metalaxyl Snake River at Nuestro Rd near Sutter, CA 391107121421201 03/08/2016 08:45 Storm

—

—

—

—

—

—

—

Snake River at Nuestro Rd near Sutter, CA 391107121421201 07/19/2016 11:15 Dry

—

—

—

—

—

—

—

Snake River at Nuestro Rd near Sutter, CA 391107121421201 08/16/2016 19:20 Dry

—

—

—

—

—

—

—

Snake River at Nuestro Rd near Sutter, CA 391107121421201 11/16/2016 16:10 Storm

—

—

—

—

—

—

—

Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 08/26/2015 10:30 Dry

—

—

—

—

—

—

—

Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 02/01/2016 12:35 Storm

—

—

—

—

—

—

—

Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 06/08/2016 12:00 Dry

—

—

—

—

—

—

—

Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 08/07/2016 11:00 Dry

—

—

—

—

—

—

—

Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 10/18/2016 11:30 Dry

—

—

—

—

—

—

—

Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 12/19/2016 12:10 Storm

—

—

—

—

—

—

—

Alisal Creek at La Guardia St near Salinas, CA 363925121364701 04/29/2015 11:05 Dry

—

—

—

—

— 13.5

—

Alisal Creek at La Guardia St near Salinas, CA 363925121364701 08/25/2015 13:00 Dry

— 50.0

— 41.3 30.8

— 12.2

Alisal Creek at La Guardia St near Salinas, CA3 363925121364701 12/15/2015 12:30 Storm

— 264

—

—

—

—

—

Alisal Creek at La Guardia St near Salinas, CA 363925121364701 04/28/2016 12:26 Dry 61.9 68.4

—

—

—

—

—

Alisal Creek at La Guardia St near Salinas, CA 363925121364701 09/28/2016 12:25 Dry

—

—

—

—

—

—

—

Alisal Creek at La Guardia St near Salinas, CA4 363925121364701 01/12/2017 09:45 Storm

— 106

—

—

—

—

—

USGS site name USGS site number Date (mm/dd/yyyy) Time (hh:mm) Event Metolachlor Myclobutanil Oxydiazon Oxyfluorfen p,p’-DDD p,p’-DDE p,p’-DDT 

Kings River at Empire Weir 2 at Stratford, CA 361044119500101 04/14/2015 09:25 Dry

—

—

—

—

—

—

—

Kings River at Empire Weir 2 at Stratford, CA 361044119500101 06/30/2015 11:41 Dry

—

—

—

—

—

—

—

Kings River at Empire Weir 2 at Stratford, CA 361044119500101 11/03/2015 11:41 Storm

—

—

—

—

—

—

—

Kings River at Empire Weir 2 at Stratford, CA 361044119500101 03/07/2016 10:40 Storm

—

—

— 2.8

—

—

—

Kings River at Empire Weir 2 at Stratford, CA 361044119500101 09/26/2016 11:05 Dry

—

—

—

—

—

—

—

Kings River at Empire Weir 2 at Stratford, CA 361044119500101 11/30/2016 10:45 Dry

—

—

—

—

—

—

—

French Camp Slough at Airport Way near Stockton, CA 375252121145401 04/21/2015 11:50 Dry

—

—

— 2.3

— 3.2

—

French Camp Slough at Airport Way near Stockton, CA 375252121145401 07/21/2015 12:40 Dry

—

—

—

—

—

—

—

French Camp Slough at Airport Way near Stockton, CA 375252121145401 01/06/2016 09:40 Storm

—

—

—

—

—

—

—

French Camp Slough at Airport Way near Stockton, CA 375252121145401 03/07/2016 11:40 Storm

—

— 32.7 22.1

—

—

—

French Camp Slough at Airport Way near Stockton, CA 375252121145401 07/19/2016 12:20 Dry

—

—

—

—

—

—

—

French Camp Slough at Airport Way near Stockton, CA 375252121145401 09/20/2016 11:40 Dry

—

—

—

—

—

—

—
Results From Suspended Sediment Samples 31

USGS site name USGS site number Date (mm/dd/yyyy) Time (hh:mm) Event Metolachlor Myclobutanil Oxydiazon Oxyfluorfen p,p’-DDD p,p’-DDE p,p’-DDT 

Ingram Creek at River Rd near Patterson, CA 373747121125200 06/09/2015 08:45 Dry — — — 46.0 6.1 40.5 14.0Ingram Creek at River Rd near Patterson, CA 373747121125200 09/15/2015 10:00 Dry — — — 9.8 — 3.0 —Ingram Creek at River Rd near Patterson, CA2 373747121125200 01/19/2016 13:20 Storm 26.7 96.1 — 783 31.3 139 84.1Ingram Creek at River Rd near Patterson, CA 373747121125200 04/28/2016 16:05 Dry — — — 10.2 — 14.6 —Ingram Creek at River Rd near Patterson, CA 373747121125200 07/12/2016 13:30 Dry 6.3 — — 62.7 9.0 44.3 7.1Ingram Creek at River Rd near Patterson, CA 373747121125200 01/09/2017 12:40 Storm — 160 — 684 — 9.7 —Snake River at Nuestro Rd near Sutter, CA 391107121421201 05/20/2015 09:15 Dry — — — — — — —Snake River at Nuestro Rd near Sutter, CA 391107121421201 07/21/2015 14:00 Dry — — — 52.9 — — —Snake River at Nuestro Rd near Sutter, CA 391107121421201 03/08/2016 08:45 Storm — — — 21.5 — — —Snake River at Nuestro Rd near Sutter, CA 391107121421201 07/19/2016 11:15 Dry — — — — — — —Snake River at Nuestro Rd near Sutter, CA 391107121421201 08/16/2016 19:20 Dry — — — — — — —Snake River at Nuestro Rd near Sutter, CA 391107121421201 11/16/2016 16:10 Storm — — — — — — —Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 08/26/2015 10:30 Dry — 7.8 51.2 49.5 — — —Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 02/01/2016 12:35 Storm — — 6.0 3.5 — — —Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 06/08/2016 12:00 Dry — — 3.1 2.3 — — —Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 08/07/2016 11:00 Dry — — 5.8 — — — —Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 10/18/2016 11:30 Dry — — 19.2 — — — —Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 12/19/2016 12:10 Storm — — 9.2 — — — —Alisal Creek at La Guardia St near Salinas, CA 363925121364701 04/29/2015 11:05 Dry — — — 11.3 8.3 23.7 20.4Alisal Creek at La Guardia St near Salinas, CA 363925121364701 08/25/2015 13:00 Dry — 19.9 — 17.7 6.1 14.6 10.4Alisal Creek at La Guardia St near Salinas, CA3 363925121364701 12/15/2015 12:30 Storm — — — 37.3 14.4 56.4 37.5Alisal Creek at La Guardia St near Salinas, CA 363925121364701 04/28/2016 12:26 Dry — — — 56.8 9.5 26.5 28.7Alisal Creek at La Guardia St near Salinas, CA 363925121364701 09/28/2016 12:25 Dry — — — 2.4 2.2 11.5 —Alisal Creek at La Guardia St near Salinas, CA4 363925121364701 01/12/2017 09:45 Storm — — — 198 57.0 198 118

Table 7. Pesticide results in suspended-sediment samples from agricultural sites.—Continued[All results in nanogram per liter (ng/L). Compounds analyzed for but not detected: 3,4-dichloroaniline, 3,5-dichloroaniline, acetamiprid, acibenzolar-S-methyl, alachlor, allethrin, atrazine, azinphos-methyl, azinphos-methyl oxon, benefin (benfluralin), bromoconazole, butralin, butylate, captan, carbaryl, carbendazim, carbofuran, chlorantraniliprole, chlorpyrifos, chlorpyrifos oxon, clothianidin, coumaphos, cyantraniliprole, cyazofamid, cycloate, cyfluthrin, cyhalofop-butyl, cymoxanil, cyproconazole, cyprodinil, DCPMU, DCPU, deltamethrin, desthio-prothioconazole, desulfinylfipronil, desulfinylfipronil amide, diazinon, diazoxon, difenoconazole, dimethomorph, dinotefuran, diuron, EPTC, esfenvalerate, ethaboxam, ethalfluralin, etofenprox, famoxadone, fenamidone, fenarimol, fenbuconazole, fenhexamid, fenpropathrin, fenpyroximate, fenthion, fipronil, fipronil sulfide, fipronil sulfone, flonicamid, fluazinam, flufenacet, flumetralin, fluopyram, flupyradifurone, fluoxastrobin, fluridone, flusilazole, flutolanil, flutriafol, hexazinone, imazalil, imidacloprid, indoxacarb, ipconazole, iprodione, kresoxim-methyl, malaoxon, malathion, mandipropamid, metconazole, methidathion, methoprene, methoxyfenozide, methyl parathion, molinate, napropamide, novaluron, oryzalin, paclobutrazol, pebulate, penoxsulam, pentachloroanisole, pentachloronitrobenzene, penthiopyrad, phenothrin, phosmet, picoxystrobin, piperonyl butoxide, prometon, prometryn, propanil, propiconazole, pyraclostrobin, pyrimethanil, quinoxyfen, resmethrin, sedaxane, tebupirimfos, tebupirimfos oxon, tefluthrin, tetraconazole, tetradifon, tetramethrin, thiabendazole, thiacloprid, thiamethoxam, thiazopyr, thiobencarb, tolfenpyrad, triadimefon, triadimenol, triallate, tribufos, trifloxystrobin, triflumizole, trifluralin, triticonazole, zoxamide. Abbreviations: CA, California; g, gram; hh:mm, hour:minute; mm/dd/yyyy, month/day/year; Rd, Road; St, Street; USGS, U.S. Geological Survey; —, nondetect]
32 Detections of Current-Use Pesticides at 12 Surface Water Sites in California During a 2-Year Period Beginning in 2015 USGS site name USGS site number Date (mm/dd/yyyy) Time (hh:mm) Event Pendi methalin Permethrin Prodiamine Propargite Propyzamide Pyridaben Simazine Kings River at Empire Weir 2 at Stratford, CA 361044119500101 04/14/2015 09:25 Dry

—

—

—

—

—

—

—

Kings River at Empire Weir 2 at Stratford, CA 361044119500101 06/30/2015 11:41 Dry

—

—

—

—

—

—

—

Kings River at Empire Weir 2 at Stratford, CA 361044119500101 11/03/2015 11:41 Storm

—

—

—

—

—

—

—

Kings River at Empire Weir 2 at Stratford, CA 361044119500101 03/07/2016 10:40 Storm 34.5

—

—

—

—

—

—

Kings River at Empire Weir 2 at Stratford, CA 361044119500101 09/26/2016 11:05 Dry

—

—

—

—

—

—

—

Kings River at Empire Weir 2 at Stratford, CA 361044119500101 11/30/2016 10:45 Dry

—

—

—

—

—

—

—

French Camp Slough at Airport Way near Stockton, CA 375252121145401 04/21/2015 11:50 Dry

—

— 10.5

—

—

—

—

French Camp Slough at Airport Way near Stockton, CA 375252121145401 07/21/2015 12:40 Dry

—

—

—

—

—

—

—

French Camp Slough at Airport Way near Stockton, CA 375252121145401 01/06/2016 09:40 Storm

—

—

—

—

—

—

—

French Camp Slough at Airport Way near Stockton, CA 375252121145401 03/07/2016 11:40 Storm 54.7

—

—

—

—

— 16.2

French Camp Slough at Airport Way near Stockton, CA 375252121145401 07/19/2016 12:20 Dry

—

—

—

—

—

—

—

French Camp Slough at Airport Way near Stockton, CA 375252121145401 09/20/2016 11:40 Dry

—

—

—

—

—

—

—

Ingram Creek at River Rd near Patterson, CA 373747121125200 06/09/2015 08:45 Dry 470

—

—

—

—

—

—

Ingram Creek at River Rd near Patterson, CA 373747121125200 09/15/2015 10:00 Dry

—

—

—

—

—

—

—

Ingram Creek at River Rd near Patterson, CA2 373747121125200 01/19/2016 13:20 Storm 185

—

—

—

—

—

—

Ingram Creek at River Rd near Patterson, CA 373747121125200 04/28/2016 16:05 Dry

—

—

—

—

—

—

—

Ingram Creek at River Rd near Patterson, CA 373747121125200 07/12/2016 13:30 Dry

—

—

—

—

—

—

—

Ingram Creek at River Rd near Patterson, CA 373747121125200 01/09/2017 12:40 Storm 29.1

—

— 19.3

—

—

—

Snake River at Nuestro Rd near Sutter, CA 391107121421201 05/20/2015 09:15 Dry

—

—

—

—

—

—

—

Snake River at Nuestro Rd near Sutter, CA 391107121421201 07/21/2015 14:00 Dry

—

—

—

—

—

—

—

Snake River at Nuestro Rd near Sutter, CA 391107121421201 03/08/2016 08:45 Storm 15.9

—

—

—

—

—

—

Snake River at Nuestro Rd near Sutter, CA 391107121421201 07/19/2016 11:15 Dry

—

—

—

—

—

—

—

Snake River at Nuestro Rd near Sutter, CA 391107121421201 08/16/2016 19:20 Dry

—

—

—

—

—

—

—

Snake River at Nuestro Rd near Sutter, CA 391107121421201 11/16/2016 16:10 Storm

—

—

—

—

—

—

—

Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 08/26/2015 10:30 Dry

— 33.5 130

—

— 9.4

—

Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 02/01/2016 12:35 Storm

—

— 6.6

—

—

—

—

Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 06/08/2016 12:00 Dry

—

—

—

—

—

—

—

Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 08/07/2016 11:00 Dry

—

—

—

—

—

—

—

Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 10/18/2016 11:30 Dry

—

— 4.5

—

—

—

—

Table 7. Pesticide results in suspended-sediment samples from agricultural sites.—Continued[All results in nanogram per liter (ng/L). Compounds analyzed for but not detected: 3,4-dichloroaniline, 3,5-dichloroaniline, acetamiprid, acibenzolar-S-methyl, alachlor, allethrin, atrazine, azinphos-methyl, azinphos-methyl oxon, benefin (benfluralin), bromoconazole, butralin, butylate, captan, carbaryl, carbendazim, carbofuran, chlorantraniliprole, chlorpyrifos, chlorpyrifos oxon, clothianidin, coumaphos, cyantraniliprole, cyazofamid, cycloate, cyfluthrin, cyhalofop-butyl, cymoxanil, cyproconazole, cyprodinil, DCPMU, DCPU, deltamethrin, desthio-prothioconazole, desulfinylfipronil, desulfinylfipronil amide, diazinon, diazoxon, difenoconazole, dimethomorph, dinotefuran, diuron, EPTC, esfenvalerate, ethaboxam, ethalfluralin, etofenprox, famoxadone, fenamidone, fenarimol, fenbuconazole, fenhexamid, fenpropathrin, fenpyroximate, fenthion, fipronil, fipronil sulfide, fipronil sulfone, flonicamid, fluazinam, flufenacet, flumetralin, fluopyram, flupyradifurone, fluoxastrobin, fluridone, flusilazole, flutolanil, flutriafol, hexazinone, imazalil, imidacloprid, indoxacarb, ipconazole, iprodione, kresoxim-methyl, malaoxon, malathion, mandipropamid, metconazole, methidathion, methoprene, methoxyfenozide, methyl parathion, molinate, napropamide, novaluron, oryzalin, paclobutrazol, pebulate, penoxsulam, pentachloroanisole, pentachloronitrobenzene, penthiopyrad, phenothrin, phosmet, picoxystrobin, piperonyl butoxide, prometon, prometryn, propanil, propiconazole, pyraclostrobin, pyrimethanil, quinoxyfen, resmethrin, sedaxane, tebupirimfos, tebupirimfos oxon, tefluthrin, tetraconazole, tetradifon, tetramethrin, thiabendazole, thiacloprid, thiamethoxam, thiazopyr, thiobencarb, tolfenpyrad, triadimefon, triadimenol, triallate, tribufos, trifloxystrobin, triflumizole, trifluralin, triticonazole, zoxamide. Abbreviations: CA, California; g, gram; hh:mm, hour:minute; mm/dd/yyyy, month/day/year; Rd, Road; St, Street; USGS, U.S. Geological Survey; —, nondetect]
Results From Suspended Sediment Samples 33

Table 7. Pesticide results in suspended-sediment samples from agricultural sites.—Continued[All results in nanogram per liter (ng/L). Compounds analyzed for but not detected: 3,4-dichloroaniline, 3,5-dichloroaniline, acetamiprid, acibenzolar-S-methyl, alachlor, allethrin, atrazine, azinphos-methyl, azinphos-methyl oxon, benefin (benfluralin), bromoconazole, butralin, butylate, captan, carbaryl, carbendazim, carbofuran, chlorantraniliprole, chlorpyrifos, chlorpyrifos oxon, clothianidin, coumaphos, cyantraniliprole, cyazofamid, cycloate, cyfluthrin, cyhalofop-butyl, cymoxanil, cyproconazole, cyprodinil, DCPMU, DCPU, deltamethrin, desthio-prothioconazole, desulfinylfipronil, desulfinylfipronil amide, diazinon, diazoxon, difenoconazole, dimethomorph, dinotefuran, diuron, EPTC, esfenvalerate, ethaboxam, ethalfluralin, etofenprox, famoxadone, fenamidone, fenarimol, fenbuconazole, fenhexamid, fenpropathrin, fenpyroximate, fenthion, fipronil, fipronil sulfide, fipronil sulfone, flonicamid, fluazinam, flufenacet, flumetralin, fluopyram, flupyradifurone, fluoxastrobin, fluridone, flusilazole, flutolanil, flutriafol, hexazinone, imazalil, imidacloprid, indoxacarb, ipconazole, iprodione, kresoxim-methyl, malaoxon, malathion, mandipropamid, metconazole, methidathion, methoprene, methoxyfenozide, methyl parathion, molinate, napropamide, novaluron, oryzalin, paclobutrazol, pebulate, penoxsulam, pentachloroanisole, pentachloronitrobenzene, penthiopyrad, phenothrin, phosmet, picoxystrobin, piperonyl butoxide, prometon, prometryn, propanil, propiconazole, pyraclostrobin, pyrimethanil, quinoxyfen, resmethrin, sedaxane, tebupirimfos, tebupirimfos oxon, tefluthrin, tetraconazole, tetradifon, tetramethrin, thiabendazole, thiacloprid, thiamethoxam, thiazopyr, thiobencarb, tolfenpyrad, triadimefon, triadimenol, triallate, tribufos, trifloxystrobin, triflumizole, trifluralin, triticonazole, zoxamide. Abbreviations: CA, California; g, gram; hh:mm, hour:minute; mm/dd/yyyy, month/day/year; Rd, Road; St, Street; USGS, U.S. Geological Survey; —, nondetect]

USGS site name USGS site number Date (mm/dd/yyyy) Time (hh:mm) Event Pendi methalin Permethrin Prodiamine Propargite Propyzamide Pyridaben Simazine 

Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 12/19/2016 12:10 Storm — — — — — — —Alisal Creek at La Guardia St near Salinas, CA 363925121364701 04/29/2015 11:05 Dry — — — — — — —Alisal Creek at La Guardia St near Salinas, CA 363925121364701 08/25/2015 13:00 Dry — 33.3 — — 12.5 — —Alisal Creek at La Guardia St near Salinas, CA3 363925121364701 12/15/2015 12:30 Storm 53.7 105 — — — — —Alisal Creek at La Guardia St near Salinas, CA 363925121364701 04/28/2016 12:26 Dry — 26.0 — — 2.7 — —Alisal Creek at La Guardia St near Salinas, CA 363925121364701 09/28/2016 12:25 Dry — — — — — — —Alisal Creek at La Guardia St near Salinas, CA4 363925121364701 01/12/2017 09:45 Storm 92.3 — — — — — —

USGS site name USGS site number Date (mm/dd/yyyy) Time (hh:mm) Event tau-Fluvalinate Tebuconazole 

Kings River at Empire Weir 2 at Stratford, CA 361044119500101 04/14/2015 09:25 Dry — —Kings River at Empire Weir 2 at Stratford, CA 361044119500101 06/30/2015 11:41 Dry — —Kings River at Empire Weir 2 at Stratford, CA 361044119500101 11/03/2015 11:41 Storm — —Kings River at Empire Weir 2 at Stratford, CA 361044119500101 03/07/2016 10:40 Storm — —Kings River at Empire Weir 2 at Stratford, CA 361044119500101 09/26/2016 11:05 Dry — —Kings River at Empire Weir 2 at Stratford, CA 361044119500101 11/30/2016 10:45 Dry — —French Camp Slough at Airport Way near Stockton, CA 375252121145401 04/21/2015 11:50 Dry — —French Camp Slough at Airport Way near Stockton, CA 375252121145401 07/21/2015 12:40 Dry — —French Camp Slough at Airport Way near Stockton, CA 375252121145401 01/06/2016 09:40 Storm — —French Camp Slough at Airport Way near Stockton, CA 375252121145401 03/07/2016 11:40 Storm — —French Camp Slough at Airport Way near Stockton, CA 375252121145401 07/19/2016 12:20 Dry — —French Camp Slough at Airport Way near Stockton, CA 375252121145401 09/20/2016 11:40 Dry — —Ingram Creek at River Rd near Patterson, CA 373747121125200 06/09/2015 08:45 Dry — —Ingram Creek at River Rd near Patterson, CA 373747121125200 09/15/2015 10:00 Dry — —Ingram Creek at River Rd near Patterson, CA2 373747121125200 01/19/2016 13:20 Storm — —Ingram Creek at River Rd near Patterson, CA 373747121125200 04/28/2016 16:05 Dry — —Ingram Creek at River Rd near Patterson, CA 373747121125200 07/12/2016 13:30 Dry — —Ingram Creek at River Rd near Patterson, CA 373747121125200 01/09/2017 12:40 Storm — —Snake River at Nuestro Rd near Sutter, CA 391107121421201 05/20/2015 09:15 Dry — —Snake River at Nuestro Rd near Sutter, CA 391107121421201 07/21/2015 14:00 Dry — —
34 Detections of Current-Use Pesticides at 12 Surface Water Sites in California During a 2-Year Period Beginning in 2015 USGS site name USGS site number Date (mm/dd/yyyy) Time (hh:mm) Event tau-Fluvalinate Tebuconazole Snake River at Nuestro Rd near Sutter, CA 391107121421201 03/08/2016 08:45 Storm

—

—

Snake River at Nuestro Rd near Sutter, CA 391107121421201 07/19/2016 11:15 Dry

—

—

Snake River at Nuestro Rd near Sutter, CA 391107121421201 08/16/2016 19:20 Dry

—

—

Snake River at Nuestro Rd near Sutter, CA 391107121421201 11/16/2016 16:10 Storm

—

—

Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 08/26/2015 10:30 Dry 59.6

—

Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 02/01/2016 12:35 Storm

—

—

Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 06/08/2016 12:00 Dry

—

—

Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 08/07/2016 11:00 Dry

—

—

Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 10/18/2016 11:30 Dry

—

—

Rainbow Creek at Huffstatler St at Rainbow, CA 332455117090701 12/19/2016 12:10 Storm

—

—

Alisal Creek at La Guardia St near Salinas, CA 363925121364701 04/29/2015 11:05 Dry

—

—

Alisal Creek at La Guardia St near Salinas, CA 363925121364701 08/25/2015 13:00 Dry

— 77.3

Alisal Creek at La Guardia St near Salinas, CA3 363925121364701 12/15/2015 12:30 Storm

—

—

Alisal Creek at La Guardia St near Salinas, CA 363925121364701 04/28/2016 12:26 Dry

—

—

Alisal Creek at La Guardia St near Salinas, CA 363925121364701 09/28/2016 12:25 Dry

—

—

Alisal Creek at La Guardia St near Salinas, CA4 363925121364701 01/12/2017 09:45 Storm

—

—

1Value detected below minimum detection limit.2Sample was obtained from a filtered volume differing from its associated water sample. The volume associated with this sample is 0.515 liters.3Sample was obtained from a filtered volume differing from its associated water sample. The volume associated with this sample is 0.340 liters.4Sample was obtained from a filtered volume differing from its associated water sample. The volume associated with this sample is 0.300 liters.

Table 7. Pesticide results in suspended-sediment samples from agricultural sites.—Continued[All results in nanogram per liter (ng/L). Compounds analyzed for but not detected: 3,4-dichloroaniline, 3,5-dichloroaniline, acetamiprid, acibenzolar-S-methyl, alachlor, allethrin, atrazine, azinphos-methyl, azinphos-methyl oxon, benefin (benfluralin), bromoconazole, butralin, butylate, captan, carbaryl, carbendazim, carbofuran, chlorantraniliprole, chlorpyrifos, chlorpyrifos oxon, clothianidin, coumaphos, cyantraniliprole, cyazofamid, cycloate, cyfluthrin, cyhalofop-butyl, cymoxanil, cyproconazole, cyprodinil, DCPMU, DCPU, deltamethrin, desthio-prothioconazole, desulfinylfipronil, desulfinylfipronil amide, diazinon, diazoxon, difenoconazole, dimethomorph, dinotefuran, diuron, EPTC, esfenvalerate, ethaboxam, ethalfluralin, etofenprox, famoxadone, fenamidone, fenarimol, fenbuconazole, fenhexamid, fenpropathrin, fenpyroximate, fenthion, fipronil, fipronil sulfide, fipronil sulfone, flonicamid, fluazinam, flufenacet, flumetralin, fluopyram, flupyradifurone, fluoxastrobin, fluridone, flusilazole, flutolanil, flutriafol, hexazinone, imazalil, imidacloprid, indoxacarb, ipconazole, iprodione, kresoxim-methyl, malaoxon, malathion, mandipropamid, metconazole, methidathion, methoprene, methoxyfenozide, methyl parathion, molinate, napropamide, novaluron, oryzalin, paclobutrazol, pebulate, penoxsulam, pentachloroanisole, pentachloronitrobenzene, penthiopyrad, phenothrin, phosmet, picoxystrobin, piperonyl butoxide, prometon, prometryn, propanil, propiconazole, pyraclostrobin, pyrimethanil, quinoxyfen, resmethrin, sedaxane, tebupirimfos, tebupirimfos oxon, tefluthrin, tetraconazole, tetradifon, tetramethrin, thiabendazole, thiacloprid, thiamethoxam, thiazopyr, thiobencarb, tolfenpyrad, triadimefon, triadimenol, triallate, tribufos, trifloxystrobin, triflumizole, trifluralin, triticonazole, zoxamide. Abbreviations: CA, California; g, gram; hh:mm, hour:minute; mm/dd/yyyy, month/day/year; Rd, Road; St, Street; USGS, U.S. Geological Survey; —, nondetect]
Results From Suspended Sediment Samples 35

Table 8. Pesticide results in suspended-sediment samples from urban sites. [All results in nanograms per liter (ng/L). Compounds analyzed for but not detected: 3,4-dichloroaniline, 3,5-dichloroaniline, acetamiprid, acibenzolar-S-methyl, alachlor, allethrin, atrazine, azinphos-methyl, azinphos-methyl oxon, azoxystrobin, benefin (benfluralin), bromoconazole, butralin, butylate, captan, carbaryl, carbendazim, carbofuran, chlorantraniliprole, chlorpyrifos, chlorpyrifos oxon, clomazone, clothianidin, coumaphos, cyantraniliprole, cyazofamid, cycloate, cyfluthrin, cyhalofop-butyl, cyhalothrin (all isomers), cymoxanil, cypermethrin, cyproconazole, cyprodinil, DCPA, DCPMU, DCPU, deltamethrin, desthio-prothioconazole, desulfinylfipronil, desulfinylfipronil amide, diazinon, diazoxon, difenoconazole, dimethomorph, dinotefuran, diuron, EPTC, esfenvalerate, ethaboxam, ethalfluralin, etofenprox, famoxadone, fenamidone, fenarimol, fenbuconazole, fenhexamid, fenpropathrin, fenpyroximate, fenthion, fipronil, fipronil sulfide, fipronil sulfone, flonicamid, fluazinam, fludioxonil, flufenacet, flumetralin, fluopicolide, fluopyram, flupyradifurone, fluoxastrobin, fluridone, flusilazole, flutolanil, flutriafol, fluxapyroxad, hexazinone, imazalil, imidacloprid, indoxacarb, ipconazole, iprodione, kresoxim-methyl, malaoxon, malathion, mandipropamid, metalaxyl, metconazole, methidathion, methoprene, methoxyfenozide, methyl parathion, metolachlor, molinate, myclobutanil, napropamide, novaluron, oryzalin, oxadiazon, oxyfluorfen, p,p’-DDT, paclobutrazol, pebulate, penoxsulam, pentachloroanisole, pentachloronitrobenzene, penthiopyrad, phenothrin, phosmet, picoxystrobin, piperonyl butoxide, prometon, prometryn, propanil, propargite, propiconazole, propyzamide, pyraclostrobin, pyridaben, pyrimethanil, quinoxyfen, resmethrin, sedaxane, simazine, tau-fluvalinate, tebuconazole, tebupirimfos, tebupirimfos oxon, tefluthrin, tetraconazole, tetradifon, tetramethrin, thiabendazole, thiacloprid, thiamethoxam, thiazopyr, thiobencarb, tolfenpyrad, triadimefon, triadimenol, triallate, tribufos, trifloxystrobin, triflumizole, trifluralin, triticonazole, zoxamide. Abbreviations: CA, California; Dr, Drive; g, gram; hh:mm, hour:minute; L, liter; mm/dd/yyyy, month/day/year; Rd, Road; St, Street; USGS, U.S. Geological Survey; —, nondetect]

USGS site name USGS site number Date (mm/dd/yyyy) Time (hh:mm) Event Volume (L) Mass (g) Bifenthrin Boscalid Chlorothalonil Dithiopyr 

Unnamed Tributary to Alder Creek at Iron Point Rd near Folsom, CA 383844121084001 04/07/2015 11:10 Storm 1.010 0.007 30.7 — 5.5 —Unnamed Tributary to Alder Creek at Iron Point Rd near Folsom, CA 383844121084001 11/02/2015 10:50 Storm 0.975 0.001 15.3 — — —Unnamed Tributary to Alder Creek at Iron Point Rd near Folsom, CA 383844121084001 02/18/2016 10:05 Storm 1.06 0.004 — — — —Unnamed Tributary to Alder Creek at Iron Point Rd near Folsom, CA 383844121084001 04/07/2016 12:00 Dry 1.040 0.014 5.1 — — —Unnamed Tributary to Alder Creek at Iron Point Rd near Folsom, CA 383844121084001 10/14/2016 16:52 Storm 1.015 0.013 6.8 — — —Unnamed Tributary to Alder Creek at Iron Point Rd near Folsom, CA 383844121084001 12/06/2016 11:30 Dry 0.920 0.002 — — — —Pleasant Grove Creek at Crocker Ranch Rd near Roseville, CA 384755121205201 06/08/2015 11:00 Dry 1.025 0.044 1.2 — — —Pleasant Grove Creek at Crocker Ranch Rd near Roseville, CA 384755121205201 11/02/2015 1:20 Storm 1.020 0.012 37.2 — — —Pleasant Grove Creek at Crocker Ranch Rd near Roseville, CA 384755121205201 02/17/2016 22:37 Storm 1.03 0.023 22.4 — — 7.6Pleasant Grove Creek at Crocker Ranch Rd near Roseville, CA 384755121205201 06/14/2016 10:15 Dry 1.040 0.009 — — — —Pleasant Grove Creek at Crocker Ranch Rd near Roseville, CA 384755121205201 08/01/2016 10:05 Dry 1.040 0.038 2.1 — — —Pleasant Grove Creek at Crocker Ranch Rd near Roseville, CA 384755121205201 10/14/2016 13:45 Storm 1.025 0.023 17.8 — — —Salt Creek at Niguel Rd at Laguna Niguel, CA 333018117423301 05/04/2015 17:40 Dry 0.980 0.049 10.6 — — —Salt Creek at Niguel Rd at Laguna Niguel, CA 333018117423301 02/04/2016 11:12 Dry 1.000 0.102 9.5 — — —Salt Creek at Niguel Rd at Laguna Niguel, CA 333018117423301 05/19/2016 12:20 Dry 1.020 0.0385 3.0 — — —Salt Creek at Niguel Rd at Laguna Niguel, CA 333018117423301 08/07/2016 12:50 Dry 1.020 0.038 — — — —Salt Creek at Niguel Rd at Laguna Niguel, CA 333018117423301 08/18/2016 7:30 Dry 1.040 0.042 — — — —Salt Creek at Niguel Rd at Laguna Niguel, CA 333018117423301 11/03/2016 7:45 Dry 1.050 0.025 — — — —San Luis Obispo Creek at Los Osos Valley Rd near San Luis Obispo, CA 351436120405201 05/20/2015 8:15 Dry 1.025 0.014 — — — —San Luis Obispo Creek at Los Osos Valley Rd near San Luis Obispo, CA 351436120405201 09/09/2015 12:00 Dry 1.040 0.012 4.2 — — —San Luis Obispo Creek at Los Osos Valley Rd near San Luis Obispo, CA 351436120405201 11/16/2015 12:00 Storm 1.000 0.0115 — 16.2 — —San Luis Obispo Creek at Los Osos Valley Rd near San Luis Obispo, CA 351436120405201 04/06/2016 14:15 Dry 1.000 0.003 — — — —San Luis Obispo Creek at Los Osos Valley Rd near San Luis Obispo, CA 351436120405201 07/13/2016 10:55 Dry 1.030 0.010 13.3 — — —San Luis Obispo Creek at Los Osos Valley Rd near San Luis Obispo, CA 351436120405201 08/30/2016 11:44 Dry 1.030 0.013 — — — —Stevens Creek at Barranca Dr a Monta Vista, CA 372004122035201 08/05/2015 12:08 Dry 0.920 0.008 — — — —Stevens Creek at Barranca Dr a Monta Vista, CA 372004122035201 02/01/2016 10:35 Dry 1.020 0.010 — — — —Stevens Creek at Barranca Dr a Monta Vista, CA 372004122035201 03/24/2016 11:14 Dry 1.030 0.046 — — — —Stevens Creek at Barranca Dr a Monta Vista, CA 372004122035201 06/08/2016 13:00 Dry 1.050 0.016 — — — —
36 Detections of Current-Use Pesticides at 12 Surface Water Sites in California During a 2-Year Period Beginning in 2015 USGS site name USGS site number Date (mm/dd/yyyy) Time (hh:mm) Event Volume (L) Mass (g) Bifenthrin Boscalid Chlorothalonil Dithiopyr Stevens Creek at Barranca Dr a Monta Vista, CA 372004122035201 01/03/2017 13:00 Storm 1.010 0.012

—

—

—

—

Stevens Creek at Barranca Dr a Monta Vista, CA 372004122035201 01/10/2017 11:50 Storm 1.020 0.103

—

—

—

—

Sweetwater River at Willow St at Chula Vista, CA 323932117023201 08/24/2015 10:30 Dry 0.925 0.108

—

—

—

—

Sweetwater River at Willow St at Chula Vista, CA 323932117023201 02/01/2016 10:45 Storm 0.950 0.026 4.3

—

—

—

Sweetwater River at Willow St at Chula Vista, CA 323932117023201 06/08/2016 10:30 Dry 0.990 0.043

—

—

—

—

Sweetwater River at Willow St at Chula Vista, CA 323932117023201 08/03/2016 14:50 Dry 1.030 0.047

—

—

—

—

Sweetwater River at Willow St at Chula Vista, CA 323932117023201 10/18/2016 10:00 Dry 0.970 0.040

—

—

—

—

Sweetwater River at Willow St at Chula Vista, CA 323932117023201 12/19/2016 10:30 Storm 0.995 0.019

—

—

—

—

USGS site name USGS site number Date (mm/dd/yyyy) Time Event p,p’-DDD p,p’-DDE Pendimethalin Permethrin Prodiamine 

Unnamed Tributary to Alder Creek at Iron Point Rd near Folsom, CA 383844121084001 04/07/2015 11:10 Storm

—

—

—

—

—

Unnamed Tributary to Alder Creek at Iron Point Rd near Folsom, CA 383844121084001 11/02/2015 10:50 Storm

—

—

—

—

—

Unnamed Tributary to Alder Creek at Iron Point Rd near Folsom, CA 383844121084001 02/18/2016 10:05 Storm

—

—

—

—

—

Unnamed Tributary to Alder Creek at Iron Point Rd near Folsom, CA 383844121084001 04/07/2016 12:00 Dry

—

—

— 12.0

—

Unnamed Tributary to Alder Creek at Iron Point Rd near Folsom, CA 383844121084001 10/14/2016 16:52 Storm

—

—

—

—

—

Unnamed Tributary to Alder Creek at Iron Point Rd near Folsom, CA 383844121084001 12/06/2016 11:30 Dry

—

—

—

—

—

Pleasant Grove Creek at Crocker Ranch Rd near Roseville, CA 384755121205201 06/08/2015 11:00 Dry

—

—

—

—

—

Pleasant Grove Creek at Crocker Ranch Rd near Roseville, CA 384755121205201 11/02/2015 1:20 Storm

—

—

—

—

—

Pleasant Grove Creek at Crocker Ranch Rd near Roseville, CA 384755121205201 02/17/2016 22:37 Storm

—

— 140 29.1 5.3

Pleasant Grove Creek at Crocker Ranch Rd near Roseville, CA 384755121205201 06/14/2016 10:15 Dry

—

—

—

—

—

Pleasant Grove Creek at Crocker Ranch Rd near Roseville, CA 384755121205201 08/01/2016 10:05 Dry

—

—

—

—

—

Pleasant Grove Creek at Crocker Ranch Rd near Roseville, CA 384755121205201 10/14/2016 13:45 Storm

—

— 33.6

—

—

Salt Creek at Niguel Rd at Laguna Niguel, CA 333018117423301 05/04/2015 17:40 Dry

—

—

—

—

—

Salt Creek at Niguel Rd at Laguna Niguel, CA 333018117423301 02/04/2016 11:12 Dry

—

—

— 44.2

—

Salt Creek at Niguel Rd at Laguna Niguel, CA 333018117423301 05/19/2016 12:20 Dry

—

—

— 5.6

—

Salt Creek at Niguel Rd at Laguna Niguel, CA 333018117423301 08/07/2016 12:50 Dry

—

—

—

—

—

Salt Creek at Niguel Rd at Laguna Niguel, CA 333018117423301 08/18/2016 7:30 Dry

—

—

—

—

—

Salt Creek at Niguel Rd at Laguna Niguel, CA 333018117423301 11/03/2016 7:45 Dry

—

—

—

—

—

Table 8. Pesticide results in suspended-sediment samples from urban sites.—Continued[All results in nanograms per liter (ng/L). Compounds analyzed for but not detected: 3,4-dichloroaniline, 3,5-dichloroaniline, acetamiprid, acibenzolar-S-methyl, alachlor, allethrin, atrazine, azinphos-methyl, azinphos-methyl oxon, azoxystrobin, benefin (benfluralin), bromoconazole, butralin, butylate, captan, carbaryl, carbendazim, carbofuran, chlorantraniliprole, chlorpyrifos, chlorpyrifos oxon, clomazone, clothianidin, coumaphos, cyantraniliprole, cyazofamid, cycloate, cyfluthrin, cyhalofop-butyl, cyhalothrin (all isomers), cymoxanil, cypermethrin, cyproconazole, cyprodinil, DCPA, DCPMU, DCPU, deltamethrin, desthio-prothioconazole, desulfinylfipronil, desulfinylfipronil amide, diazinon, diazoxon, difenoconazole, dimethomorph, dinotefuran, diuron, EPTC, esfenvalerate, ethaboxam, ethalfluralin, etofenprox, famoxadone, fenamidone, fenarimol, fenbuconazole, fenhexamid, fenpropathrin, fenpyroximate, fenthion, fipronil, fipronil sulfide, fipronil sulfone, flonicamid, fluazinam, fludioxonil, flufenacet, flumetralin, fluopicolide, fluopyram, flupyradifurone, fluoxastrobin, fluridone, flusilazole, flutolanil, flutriafol, fluxapyroxad, hexazinone, imazalil, imidacloprid, indoxacarb, ipconazole, iprodione, kresoxim-methyl, malaoxon, malathion, mandipropamid, metalaxyl, metconazole, methidathion, methoprene, methoxyfenozide, methyl parathion, metolachlor, molinate, myclobutanil, napropamide, novaluron, oryzalin, oxadiazon, oxyfluorfen, p,p’-DDT, paclobutrazol, pebulate, penoxsulam, pentachloroanisole, pentachloronitrobenzene, penthiopyrad, phenothrin, phosmet, picoxystrobin, piperonyl butoxide, prometon, prometryn, propanil, propargite, propiconazole, propyzamide, pyraclostrobin, pyridaben, pyrimethanil, quinoxyfen, resmethrin, sedaxane, simazine, tau-fluvalinate, tebuconazole, tebupirimfos, tebupirimfos oxon, tefluthrin, tetraconazole, tetradifon, tetramethrin, thiabendazole, thiacloprid, thiamethoxam, thiazopyr, thiobencarb, tolfenpyrad, triadimefon, triadimenol, triallate, tribufos, trifloxystrobin, triflumizole, trifluralin, triticonazole, zoxamide. Abbreviations: CA, California; Dr, Drive; g, gram; hh:mm, hour:minute; L, liter; mm/dd/yyyy, month/day/year; Rd, Road; St, Street; USGS, U.S. Geological Survey; —, nondetect]
Results From Suspended Sediment Samples 37

USGS site name USGS site number Date (mm/dd/yyyy) Time Event p,p’-DDD p,p’-DDE Pendimethalin Permethrin Prodiamine 

San Luis Obispo Creek at Los Osos Valley Rd near San Luis Obispo, CA 351436120405201 05/20/2015 8:15 Dry — — — — —San Luis Obispo Creek at Los Osos Valley Rd near San Luis Obispo, CA 351436120405201 09/09/2015 12:00 Dry 214 — — 18.1 —San Luis Obispo Creek at Los Osos Valley Rd near San Luis Obispo, CA 351436120405201 11/16/2015 12:00 Storm — — — — —San Luis Obispo Creek at Los Osos Valley Rd near San Luis Obispo, CA 351436120405201 04/06/2016 14:15 Dry — — — — —San Luis Obispo Creek at Los Osos Valley Rd near San Luis Obispo, CA 351436120405201 07/13/2016 10:55 Dry — — — — —San Luis Obispo Creek at Los Osos Valley Rd near San Luis Obispo, CA 351436120405201 08/30/2016 11:44 Dry — — — — —Stevens Creek at Barranca Dr a Monta Vista, CA 372004122035201 08/05/2015 12:08 Dry — — — — —Stevens Creek at Barranca Dr a Monta Vista, CA 372004122035201 02/01/2016 10:35 Dry — — — — —Stevens Creek at Barranca Dr a Monta Vista, CA 372004122035201 03/24/2016 11:14 Dry — — — — —Stevens Creek at Barranca Dr a Monta Vista, CA 372004122035201 06/08/2016 13:00 Dry — — — — —Stevens Creek at Barranca Dr a Monta Vista, CA 372004122035201 01/03/2017 13:00 Storm — — — — —Stevens Creek at Barranca Dr a Monta Vista, CA 372004122035201 01/10/2017 11:50 Storm — — — — —Sweetwater River at Willow St at Chula Vista, CA 323932117023201 08/24/2015 10:30 Dry — — — — —Sweetwater River at Willow St at Chula Vista, CA 323932117023201 02/01/2016 10:45 Storm — 3.9 — 17.2 —Sweetwater River at Willow St at Chula Vista, CA 323932117023201 06/08/2016 10:30 Dry — — — — —Sweetwater River at Willow St at Chula Vista, CA 323932117023201 08/03/2016 14:50 Dry — — — — —Sweetwater River at Willow St at Chula Vista, CA 323932117023201 10/18/2016 10:00 Dry — — — — —Sweetwater River at Willow St at Chula Vista, CA 323932117023201 12/19/2016 10:30 Storm — — — — —

1Value detected below minimum detection limit.

Table 8. Pesticide results in suspended-sediment samples from urban sites.—Continued[All results in nanograms per liter (ng/L). Compounds analyzed for but not detected: 3,4-dichloroaniline, 3,5-dichloroaniline, acetamiprid, acibenzolar-S-methyl, alachlor, allethrin, atrazine, azinphos-methyl, azinphos-methyl oxon, azoxystrobin, benefin (benfluralin), bromoconazole, butralin, butylate, captan, carbaryl, carbendazim, carbofuran, chlorantraniliprole, chlorpyrifos, chlorpyrifos oxon, clomazone, clothianidin, coumaphos, cyantraniliprole, cyazofamid, cycloate, cyfluthrin, cyhalofop-butyl, cyhalothrin (all isomers), cymoxanil, cypermethrin, cyproconazole, cyprodinil, DCPA, DCPMU, DCPU, deltamethrin, desthio-prothioconazole, desulfinylfipronil, desulfinylfipronil amide, diazinon, diazoxon, difenoconazole, dimethomorph, dinotefuran, diuron, EPTC, esfenvalerate, ethaboxam, ethalfluralin, etofenprox, famoxadone, fenamidone, fenarimol, fenbuconazole, fenhexamid, fenpropathrin, fenpyroximate, fenthion, fipronil, fipronil sulfide, fipronil sulfone, flonicamid, fluazinam, fludioxonil, flufenacet, flumetralin, fluopicolide, fluopyram, flupyradifurone, fluoxastrobin, fluridone, flusilazole, flutolanil, flutriafol, fluxapyroxad, hexazinone, imazalil, imidacloprid, indoxacarb, ipconazole, iprodione, kresoxim-methyl, malaoxon, malathion, mandipropamid, metalaxyl, metconazole, methidathion, methoprene, methoxyfenozide, methyl parathion, metolachlor, molinate, myclobutanil, napropamide, novaluron, oryzalin, oxadiazon, oxyfluorfen, p,p’-DDT, paclobutrazol, pebulate, penoxsulam, pentachloroanisole, pentachloronitrobenzene, penthiopyrad, phenothrin, phosmet, picoxystrobin, piperonyl butoxide, prometon, prometryn, propanil, propargite, propiconazole, propyzamide, pyraclostrobin, pyridaben, pyrimethanil, quinoxyfen, resmethrin, sedaxane, simazine, tau-fluvalinate, tebuconazole, tebupirimfos, tebupirimfos oxon, tefluthrin, tetraconazole, tetradifon, tetramethrin, thiabendazole, thiacloprid, thiamethoxam, thiazopyr, thiobencarb, tolfenpyrad, triadimefon, triadimenol, triallate, tribufos, trifloxystrobin, triflumizole, trifluralin, triticonazole, zoxamide. Abbreviations: CA, California; Dr, Drive; g, gram; hh:mm, hour:minute; L, liter; mm/dd/yyyy, month/day/year; Rd, Road; St, Street; USGS, U.S. Geological Survey; —, nondetect]
38 Detections of Current-Use Pesticides at 12 Surface Water Sites in California During a 2-Year Period Beginning in 2015

Table 9. Total number of detections in suspended-sediment samples from agricultural and urban sites.

[*, fungicide;**, insecticide; ***, herbicide]

Pesticide

Agricultural sites Urban sites Total

Detections Detection frequency

(percent) Detections Detection frequency(percent) Detections Detection frequency(percent)

Azoxystrobin* 2 6 0 0 2 3

Bifenthrin** 22 61 15 42 37 51

Boscalid* 8 22 1 3 9 13

Chlorothalonil* 3 8 1 3 4 6

Clomazone*** 1 3 0 0 1 1

Cyhalothrin** 2 6 0 0 2 3

Cypermethrin** 1 3 0 0 1 1

DCPA*** 4 11 0 0 4 6

Dithiopyr*** 1 3 1 3 2 3

Fludioxinil* 1 3 0 0 1 1

Fluopicolide* 1 3 0 0 1 1

Fluxapyroxad* 1 3 0 0 1 1

Metalaxyl* 1 3 0 0 1 1

Metolachlor*** 2 6 0 0 2 3

Myclobutanil* 4 11 0 0 4 6

Oxydiazon*** 7 19 0 0 7 10

Oxyfluorfen*** 20 56 0 0 20 28

p,p’-DDD** 9 25 1 3 10 14

p,p’-DDE** 13 36 1 3 14 19

p,p’-DDT** 8 22 0 0 8 11

Pendimethalin*** 8 22 2 6 10 14

Permethrin** 4 11 6 17 10 14

Prodiamine*** 4 11 1 3 5 7

Propargite* 1 3 0 0 1 1

Propyzamide*** 2 6 0 0 2 3

Pyridaben* 1 3 0 0 1 1

Simazine*** 1 3 0 0 1 1

tau-Fluvalinate* 1 3 0 0 1 1

Tebuconazole* 1 3 0 0 1 1
References Cited 39

had no pesticide detections. Out of 29 total pesticide detections in samples from urban sites, 7 percent were fungicides, 

14 percent were herbicides, and 79 percent were insecticides 

(table 9).

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40 Detections of Current-Use Pesticides at 12 Surface Water Sites in California During a 2-Year Period Beginning in 2015

Publishing support provided by the U.S. Geological Survey

Science Publishing Network, Sacramento Publishing Service Center 

For more information concerning the research in this report, contact the

Director, California Water Science Center

U.S. Geological Survey

6000 J Street, Placer Hall

Sacramento, California 95819

https://ca.water.usgs.gov

Sanders and others—Detections of Current-Use Pesticides at 12 Surface Water Sites in California During a 2-Year Period Beginning in 2015—Data Series 1088

ISSN 2327-638X (online)

https://doi.org/10.3133/ds1088