science for a changing world Water Quality in the San ... · and 1995 from the water-quality assessment of the San Joaquin–Tulare Basins Study Unit and to relate these findings

Water Quality in theSan Joaquin-Tulare Basins

California, 1992–95

U.S. Department of the InteriorU.S. Geological Survey Circular 1159

science for a changing world

A COORDINATED EFFORT

k the
Coordination among agencies and organizations is an integral part of the NAWQA Program. We thanfollowing agencies and organizations who directly participated in the San Joaquin–Tulare Basins program.
Front cover:Yosemite National Park.(Photograph by Sylvia V. Stork, U.S. Geological Survey)

Back cover:Ground-water sampling in vineyards in eastern Fresno County, and Ecological survey at a site on the San Joaquin River.

(Photographs by Neil M. Dubrovsky, U.S. Geological Survey)

Aquatic Habitat InstituteBureau of Reclamation, Mid Pacific RegionCalifornia Department of Fish and GameCalifornia Department of Food and Agriculture, Agriculture

Resources BoardCalifornia Department of Health Services, Office of Drinking

WaterCalifornia Department of Pesticide Regulation,

Environmental Monitoring BranchCalifornia Department of Water ResourcesCalifornia Regional Water Quality Control Board, Central

Valley RegionCalifornia State Water Resources Control BoardCalifornia State University, Fresno, School of EngineeringCalifornia Waterfowl AssociationEnvironmental Defense FundKenneth D. Schmidt and Associates, Groundwater Quality

ConsultantsKern County Water AgencyKings River Conservation DistrictLarry Walker Associates, Inc., Environmental Engineering

and ManagementMerced County Association of Governments

Merced County Department of AgricultureMerced Irrigation DistrictMetropolitan Water District of Southern CaliforniaModesto Irrigation DistrictNational Park ServiceSan Joaquin River Flood Control AssociationSan Luis and Delta-Mendota Water AuthorityStanford University, Department of Geological and

Environmental SciencesTurlock Irrigation DistrictUnited Anglers of CaliforniaU.S. Army Corps of EngineersU.S. Department of Agriculture, Water Management

Research LaboratoryU.S. Environmental Protection AgencyU.S. Fish and Wildlife ServiceU.S. Natural Resources Conservation ServiceUniversity of California, Farm and Home Advisors OfficeUniversity of California, Davis, Department of Land, Air, and

Water ResourcesWater Resources CenterWestlands Water District

Chief, NAWQA ProgramU.S. Geological Survey

Water Resources Division12201 Sunrise Valley Drive, M.S. 413

Reston, VA 20192

FOR ADDITIONAL INFORMATION ON THENATIONAL WATER-QUALITY ASSESSMENT (NAWQA) PROGRAM :

San Joaquin–Tulare Basins Study Unit, contact:

District ChiefU.S. Geological Survey

Water Resources DivisionPlacer Hall

6000 J StreetSacramento, CA 95819-6129

Information on the NAWQA Program is also available on the Internet via the World Wide Web. You mayconnect to the NAWQA Home Page using the Universal Resources Locator (URL):

http://wwwrvares.er.usgs.gov/nawqa/nawqa_home.html

The San Joaquin–Tulare Basins Study Unit’s Home Page is at URL:http://water.wr.usgs.gov/sanj_nawqa/

U.S. GEOLOGICAL SURVEY CIRCULAR

Water Quality in the San Joaquin–TulareBasins, California, 1992–95

1159

By Neil M. Dubrovsky, Charles R. Kratzer, Larry R. Brown,JoAnn M. Gronberg, and Karen R. Burow

CONTENTS

National Water-Quality AssessmentProgram ........................................................ 1

Summary of major issues andfindings ......................................................... 2

Environmental setting and hydrologicconditions ..................................................... 4

Major issues and findings .............................. 6

Water-quality conditions in a nationalcontext ........................................................... 20

Study design and data collection .................. 24

Summary of compound detections and concentrations ............................................. 26

References......................................................... 32

Glossary ............................................................ 34

The use of firm, trade, and brand names in this report is for identification purposes only anddoes not constitute endorsement by the U.S. Government

Free on application to the

U.S. Geological SurveyInformation Services

Box 25286 Federal CenterDenver, CO 80225

U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY

Thomas J. Casadevall, Acting Director

1998

Dubrovsky, Neil M. Water Quality in the San Joaquin–Tulare Basins, California, 1992–95

/ by Neil M. Dubrovsky, Charles R. Kratzer, Larry R. Brown, Jo AnnM. Gronberg, Karen R. Burow .

p. cm. — (U.S. Geological Survey Circular : 1159) Includes bibliographical references (p. ). ISBN 0-607-89190-4 1. Water quality—California—San Joaquin River Watershed. 2. Water quality—California—Tulare Lake Watershed. I. Dubrovsky, N. M. II. Series.

TD224.C3W369 1998363.739’42’09794—dc21 98-12058

CIP

NATIONAL WATER-QUALITY ASSESSMENT PROGRAM

Began in 1991

Began in 1994

Began in 1997

Not scheduled yet

EXPLANATION

“The scientific andtechnical informationcontained in this reportprovides valuableassistance inCalifornia’s efforts tobetter understand andimplement programsto address waterresource issues—notonly in the SanJoaquin–TulareBasins, but throughoutthe state.”

Walt Pettit,Executive Director,California State WaterResources ControlBoard

auseosts

, andical

ramtentd anality

0 ofely,es ofsiveEachater-ol-nsis-ulta-

ionsake

s that

992Studycon-er-sed byengi-andn

qual-

Knowledge of the quality of the Nation's streams and aquifers is important becof the implications to human and aquatic health and because of the significant cassociated with decisions involving land and water management, conservationregulation. In 1991, the U.S. Congress appropriated funds for the U.S. GeologSurvey (USGS) to begin the National Water-Quality Assessment (NAWQA) Progto help meet the continuing need for sound, scientific information on the areal exof the water-quality problems, how these problems are changing with time, anunderstanding of the effects of human actions and natural factors on water quconditions.

The NAWQA Program is assessing the water-quality conditions of more than 5the Nation's largest river basins and aquifers, known as Study Units. Collectivthese Study Units cover about one-half of the United States and include sourcdrinking water used by about 70 percent of the U.S. population. Comprehenassessments of about one-third of the Study Units are ongoing at a given time.Study Unit is scheduled to be revisited every decade to evaluate changes in wquality conditions. NAWQA assessments rely heavily on existing information clected by the USGS and many other agencies as well as the use of nationally cotent study designs and methods of sampling and analysis. Such consistency simneously provides information about the status and trends in water-quality conditin a particular stream or aquifer and, more importantly, provides the basis to mcomparisons among watersheds and improve our understanding of the factoraffect water-quality conditions regionally and nationally.

This report is intended to summarize major findings that emerged between 1and 1995 from the water-quality assessment of the San Joaquin–Tulare BasinsUnit and to relate these findings to water-quality issues of regional and nationalcern. The information is primarily intended for those who are involved in watresource management. Indeed, this report addresses many of the concerns rairegulators, water-utility managers, industry representatives, and other scientists,neers, public officials, and members of stakeholder groups who provided adviceinput to the USGS during this NAWQA Study-Unit investigation. Yet, the informatiocontained here may also interest those who simply wish to know more about theity of water in the rivers and aquifers in the area where they live.

Robert M. Hirsch, Chief Hydrologist

U.S. Geological Survey Circular 1159

SUMMARY OF MAJOR ISSUES AND FINDINGS

This report summarizes the major findings of the National Water-Quality Assessment(NAWQA) for the San Joaquin–Tulare Basins, California. The brief statements of themajor findings that follow are expanded on later in this report (p. 6–19). Comparisons ofdata within this Study Unit with data from all 20 Study Units nationwide are given indescriptive (p. 20–23) and tabular (p. 26–31) formats. Additional information on themethods, approaches, and findings of all the investigations of the San Joaquin–TulareBasins NAWQA studies is available in the technical reports listed on pages 32–33.Though this report is an integral part of a national study, it also is intended to serve as astand-alone resource for anyone interested in water quality in California.

,

ples.ions

tions

ty of

off- inn be

CALIF

The California Water ResourcesControl Board has set a goal ofzero toxicity in surface water in theSan Joaquin River system. Thisgoal is based on concerns formaintenance of anadromous fish,endangered fish in theSacramento–San Joaquin Delta,and human health. Toxicity mayresult from several causes, butgenerally has been attributed topesticides from agriculturalnonpoint sources. High concen-trations of organophosphateinsecticides, resulting from appli-cation to some orchards during thewinter, are of particular concern.(p. 6–9)

Toxicity to Aqua

2 Water Quality in the San Joaquin–Tular

Potential for Adverse E

Nutrient Concentrations in

Designated beneficial uses forthe San Joaquin River includedrinking water and the aquaticecosystem. Nitrate andammonia criteria have been set

A wide variety of pesticides occur in the San Joaquin River and its tributariessome at concentrations high enough to adversely impact aquatic life.

• Forty-nine pesticides were detected in the San Joaquin River and threesubbasins, 22 of which were detected in more than 20 percent of the samAvailable drinking-water standards were not exceeded, but the concentratof seven pesticides exceeded the criteria for the protection of aquatic life.

• Pesticide occurrence is related to the timing and spatial distribution ofpesticide application; the most frequent occurrence and highest concentragenerally coincide with the time of heaviest agricultural application.

• Crop type and basin characteristics affect spatial and seasonal variabilipesticide occurrence.

• The main source of organophosphate insecticides is the application todormant orchards. Concentrations of organophosphate insecticides in runare high, and highly variable, during winter storms. Peak diazinon concentrations in Orestimba Creek, in the Merced and the Tuolumne Rivers, andthe main stem of the San Joaquin River frequently exceeded levels that caacutely toxic to some aquatic life.

• Diazinon and other pesticides were also found to be transported to theTuolumne River in stormwater runoff from the Modesto urban area.

tic Organisms in Streams Attributed to Pesticides

ms of

and

70s

sue

tic

ffects on Biota from Pesticides in Bed Sediment and Biota
Long-banned organochlorineinsecticides, such as DDT, arebound to soil particles in areas ofpast application. The soils andassociated bound pesticides aretransported to streams by soilerosion during natural or irrigation-related runoff. Once in the stream,organochlorine insecticides aretaken up by organisms and bio-accumulated through the foodchain. These compounds havebeen shown to be harmful to wild-life and humans that consumethem. (p. 10–11)
n if

Long-banned organochlorine insecticides continue to be transported to streaby soil erosion of contaminated agricultural fields, resulting in contaminationsuspended sediment, bed sediment, and aquatic organisms.

• Concentrations of organochlorine insecticides, such as DDT, toxaphene,chlordane, in tissues of clams and fish from the San Joaquin River and itswestern tributaries, were high relative to national values obtained in the 19and 1980s.

• Concentrations of DDT compounds in fine-grained bed sediments and tissamples are correlated, suggesting that bioaccumulation is taking place.

• Most whole-water concentrations ofp,p -DDT, chlordane, dieldrin, andtoxaphene exceeded chronic criteria for the protection of freshwater aqualife.

• Runoff from winter storms will continue to deliver a substantial load ofsediment-bound organochlorine insecticides to the San Joaquin River, eveirrigation-induced soil erosion is reduced.

e Basins, California, 1992–95

the San Joaquin River Generally Support the Beneficial Uses

Some nitrate and ammonia concentrations exceed criteria in some smalltributaries, but generally do not limit beneficial uses in the main stem of the SanJoaquin River.

• Mud and Salt Sloughs account for only about 10 percent of the streamflowbut contribute nearly half the nitrate load in the San Joaquin River.

SUMMARY OF MAJOR ISSUES AND FINDINGS

onse

quins

ned thedand

cies

of

Habitat Disruption and Wate

by USEPA to protect these bene-ficial uses. The San Joaquin RiverBasin has many sources of nitrateand ammonia: fertilizer andmanure, subsurface agriculturaldrains, dairies, and wastewater-treatment plants. (p. 12–13)

• Nitrate concentrations in the San Joaquin River have been increasing overthe last 40 years, but concentrations are still well below the drinking-waterstandard.

• Ammonia criteria were frequently exceeded in Turlock Irrigation Districtlateral 5, and occasionally in Orestimba Creek and Spanish Grant Drain. Noneof the samples collected in the main stem of the San Joaquin River exceededcriteria during 1993–95.

Development of water resources inthe San Joaquin River drainage,including the Sacramento-SanJoaquin Delta, has been accom-panied by large-scale changes inthe aquatic ecosystems, includingfish populations. Anadromoussalmon have declined, along withother migratory and resident nativefish species. Though there arelikely multiple reasons for declinesin native fish species, the roles ofwater chemistry and habitat degra-dation have never been addressedon a basinwide basis. (p. 14–15)

Fish communities in the San Joaquin River and its tributaries change in respto water chemistry and habitat quality in a pattern suggesting that humanactivities, including agriculture, are important factors in controlling the distri-bution and abundance of fish species. Fish communities in the lower San JoaRiver were highly degraded compared with other NAWQA Study Units, as wastream habitat at some sites.

• Introduced fish species outnumber native fish species by almost 2 to 1.

• In the lower San Joaquin River drainage, four groups of sites can be defion the basis of fish communities. Native species were most common nearfoothill dams and were gradually replaced by different groups of introducespecies in downstream areas where land use is dominated by agriculture other human activities.

• The Stanislaus River appeared to provide the best habitat for native speof the three major tributaries studied, possibly because of the way flow ismanaged in the Stanislaus River compared with that of the Tuolumne andMerced Rivers.

• Fish communities provide a useful assessment of overall stream healthSan Joaquin Valley streams. Though the analysis cannot separate theindividual effects of water chemistry (including toxicity) and habitat quality,both appear to be important.

r Chemistry Have Adversely Affected Native Fish Populations

rP).yter

ingl-

er.

romsed

es

om

the

use

Ground Water Have Been Degraded by Fertilizers and Pesticides
Ground water is the primarysource of drinking water for themajority of the population in theeastern San Joaquin Valley.Millions of pounds of pesticidesand fertilizer have been used onagricultural land in the valley. Priordata have shown ground-watercontamination by agriculturalnonpoint sources. (p. 16–19)
Drinking-Water Supplies From
Nitrate concentrations in ground water frequently exceeded drinking waterstandards; however, pesticide concentrations rarely exceeded drinking-watestandards, with the notable exception of 1,2,-dibromo-3-chloropropane (DBC
• Nitrate concentrations in ground water in the eastern San Joaquin Valleexceeded the U.S. Environmental Protection Agency (USEPA) drinking-wastandard in about one fourth of the domestic water-supply wells sampled.

• Nitrate concentrations in shallow ground water were related to the overlyagricultural land-use setting; concentrations varied among different agricutural land-use settings and were linked to fertilizer application, physicalcharacteristics of the sediment, and biochemical processes in ground wat

• Nitrate concentrations in ground water have increased since the 1950s. F1950 to 1980, the largest source of nitrate—nitrogen fertilizer—also increafrom 114 to 745 million pounds per year.

• Pesticides were detected in about two-thirds of the ground-water samplcollected from domestic water supply wells, but concentrations of mostpesticides were low—less than 0.1 microgram per liter (µg/L).

• DBCP concentrations exceed the USEPA drinking-water standard of0.2µg/L in 20 percent of the domestic water supply wells sampled. Data frmonitoring wells show that DBCP concentrations generally decrease withdepth and are highly variable near the water table.

• Pesticide concentrations in ground water generally have not increased inlast decade on the basis of a small number of wells sampled (19) during1986–87 and again in 1995. Direct comparison of the data is difficult becaof changes in detection limits.

U.S. Geological Survey Circular 1159 3

ENVIRONMENTAL SETTING AND HYDROLOGIC CONDITIONS

nt 0

5,000

10,000

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, IN

SQ

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ES10

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20

30

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PE

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AN

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TOTAL LAND AREA = 31,200 square miles

t

ishis of

The San Joaquin–Tulare Basins NAWQA Study Unit islocated in central California and includes the San JoaquinValley, the eastern slope of the Coast Ranges, and thewestern slope of the Sierra Nevada.

The Sierra Nevada are predominantly forested land, anthe Coast Ranges and the foothills of the Sierra Nevada arangeland. Almost the entire valley floor is used foragricultural land. In 1987, about 10.5 million acres in theSan Joaquin Valley was farmland (San Joaquin ValleyDrainage Program, 1990, p. 50). Abundant water, combinwith the long growing season, results in an exceptionallyproductive agricultural economy in the San Joaquin ValleyIn 1987, approximately 10.2 percent of the total value ofagricultural production in the United States came fromCalifornia, 49 percent of which, or $6.82 billion, was fromthe San Joaquin Valley.

Thirty-eight percent of the surface water is imported fromthe Sacramento–San Joaquin Delta through the Delta-Mendota Canal and California Aqueduct (U.S. Bureau ofReclamation, 1990; California Department of WaterResources, 1991). Most of the rest of the surface water isfrom the Sierra Nevada. Surface water from the SierraNevada is of very high quality, but major changes in waterquality occur when surface water enters the San JoaquinValley. These changes are primarily due to the large amou

4 Water Quality in the San Joaquin–Tulare Basins, California, 199

EXPLANATION

LAND USE

UrbanAgricultureRangelandForestTundraOther

Cosumnes River

Calaveras River

Stanislaus River

Merced River

ChowchillaRiver

Tuolumne River

Fresno River

Fresno SloughKings Riv

er

Kaw eah

River

Mokelumne River

LosGatos C reek

Tule River

KernRiver

S an Joaquin

River

Delta

- M

endota CanalLosBanosCreek

Madera Canal

California

Aqueduct

Friant-K

ernC

anal

35

36

37

38

121 120

CO

AS

TR

ANG

ESSIER

RA

NEVA

DA

SANJOAQUIN

BASIN

TULAREBASIN

dre

ed

.

15,000 48

of irrigated agriculture, which affects the quality of bothsurface and ground water in the valley.

Irrigation return water may reach surface water as direcrunoff (tailwater), as water from subsurface drainagesystems installed to control the water table, or as groundwater discharged through riverbeds. The result can beincreased concentrations of dissolved solids, nutrients,pesticides, and, in some areas, trace elements. Irrigation the largest source of recharge to the regional aquifer, and tground-water recharge can contain higher concentrationsdissolved solids than natural recharge in the past. Thisrecharge also may contain elevated concentrations ofnutrients, pesticide residues, and trace elements.

2–95

TO

TA

L

PU

BLI

C S

UP

PLY

2,30

4,00

0 P

OP

ULA

TIO

NS

ER

VE

D

DO

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ST

IC S

UP

PLY

704,

000

PO

PU

LAT

ION

SE

RV

ED

CO

MM

ER

CIA

L

IND

US

TR

IAL

AN

D M

ININ

G

IRR

IGA

TIO

NA

ND

LIV

ES

TO

CK

TH

ER

MO

ELE

CT

RIC

16,000

12,000

14,000

0

2,000

4,000

6,000

8,000

10,000

WA

TE

R W

ITH

DR

AW

ALS

,IN

MIL

LIO

NS

OF

GA

LLO

NS

PE

R D

AY

100

110

90

80

7060

50

40

30

20

10

0

SURFACE WATER

GROUND WATER93%

100%

5% <1% <1% <1% 0%

PE

RC

EN

TA

GE

OF

TO

TA

LW

AT

ER

WIT

HD

RA

WA

LS

Irrigation of agricultural land on the valley floor is theprimary use of water in the San Joaquin–TulareBasins.

UR

BA

NB

UIL

T-U

P L

AG

RIC

ULT

U L

RA

NG

EL

FO

RE

ST

L

WA

WE

TL

BA

RR

EN

L

TU

N

ENVIRONMENTAL SETTING AND HYDROLOGIC CONDITIONS

is

ow

ae,

,

t inof

The distribution of precipitation, and consequently runoff,in the San Joaquin–Tulare Basins is highly influenced bytopography. Mean annual precipitation on the valley floorranges from less than 5 inches in the south to 15 inches in thenorth. Precipitation in the Coast Ranges varies from less than10 inches (at Panoche 2 W) to more than 20 inches. Averageannual precipitation in the Sierra Nevada, mostly in the formof snow, ranges from about 20 inches in the lower foothills tomore than 80 inches at some higher elevation sites(Calaveras Big Trees).

Hydrologic conditions during the intensive data collectionphase (1992–95 water years [WYs]) of the San Joaquin–Tulare Basins NAWQA were variable. Precipitation in WYs1993 and 1995 was above the 1961–90 average of19.4 inches (42 and 70 percent, respectively). The 1992 and1994 WYs were slightly below average (16 and 26 percent,respectively). Approximately 80 percent of the annualprecipitation normally occurs from November to March. The

temporal distribution of precipitation during the intensivedata collection phase followed this pattern, with slightlygreater departure from average during drier years.

Total streamflows at the San Joaquin River near Vernalsite, during WYs 1992–94, were 48 to 78 percent belowaverage, whereas streamflow during WY 1995 was 91percent above average. Eighty-five percent of the streamflnormally occurs from November to March in the CoastRanges, reflecting the pattern of precipitation. In the SierrNevada, and in the San Joaquin–Tulare Basins as a wholonly 40 to 50 percent of the streamflow occurs fromNovember to March; the greater proportion of thestreamflow comes from snowmelt stored in the reservoirswhich is not released until later in the spring. During theintensive data-collection period there was little departure(less than 10 percent) from these temporal patterns, excep1995 at the San Joaquin River near Vernalis where more the streamflow occurred during the spring.


EXPLANATION

RANGE OF HISTORICAL DATA, WATER YEARS (WY) 1961-1990

MEDIANWY 1992WY 1993WY 1994WY 1995

PRECIPITATION SITE

DISCHARGE SITE

0

60

0

20

40

MO

NT

HLY

ME

AN

DIS

CH

AR

GE

, IN

TH

OU

SA

ND

CU

BIC

FE

ET

PE

R S

EC

ON

D San Joaquin Rivernear Vernalis

0

15

0

5

10

PR

EC

IPIT

AT

ION

, IN

INC

HE

S

San Joaquin-Tulare Basins

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

Representative of the entire study area

0

40

0

20

PR

EC

IPIT

AT

ION

, IN

INC

HE

S

0

8

0

2

4

6

MO

NT

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ME

AN

DIS

CH

AR

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, IN

TH

OU

SA

ND

CU

BIC

FE

ET

PE

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EC

ON

DCalaverasBig Trees

Mokelumne River near Mokelumne Hill

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

Representative of the Sierra Nevada area

0

10

0

5

PR

EC

IPIT

AT

ION

, IN

INC

HE

S

0

3

0

1

2

MO

NT

HLY

ME

AN

DIS

CH

AR

GE

, IN

HU

ND

RE

DC

UB

IC F

EE

T P

ER

SE

CO

ND Los Gatos Creek

above NunezCanyon

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

Panoche 2 W

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

No Data for March 1993

MONTHMONTH

Representative of the Coast Ranges area

CalaverasBig Trees

Mokelumne Rivernear Mokelumne Hill

San JoaquinRiver near

Vernalis

Panoche 2 W

Los GatosCreek above

Nunez Canyon

Hydrologic conditions during the intensive data-collection phase were highly variable.

MAJOR ISSUES AND FINDINGS—Pesticides in the San Joaquin River Basin

3001000 200

APPLICATION, IN THOUSAND POUNDS ACTIVE INGREDIENT

Simazine

Diazinon

EPTC

Dacthal

Metolachlor

Chlorpyrifos

Cyanazine

Diuron

Carbaryl

Trifluralin

Pebulate

Alachlor

Propargite

Molinate

Fonofos

Malathion

Napropamide

Methomyl

Pronamide

PE

ST

ICID

E

TRUCK CROPSBEANSALFALFACOTTONRICE

ALMONDSVINEYARDSCORNOTHER

i

e

0

Selected subbasins sampled in theSan Joaquin River Basin.

The diversity of crops and pesticides applied is large in the San Joaquin River Basin(California Department of Pesticide Regulation, 1994).

OrestimbaCreekBasin

SaltSloughBasin

MercedRiverBasin

Pesticide criteria for theprotection of aquatic life werefrequently exceeded

Although USEPA drinking-waterstandards were not exceeded, criteriafor the protection of freshwater aquaticlife were exceeded in 37 percent of thestream samples (Panshin and others,press). Concentrations of seven pest-icides exceeded criteria for aquaticlife; these are the herbicides diuronand trifluralin; and the insecticidesazinphos-methyl, carbaryl, chlor-pyrifos, diazinon, and malathion. Fortypercent of these exceedances areattributed solely to diazinon.

The exceedance of a water-qualitycriteria indicates a strong probabilitythat aquatic species are beingadversely affected. Aquatic life criteriaare determined by exposing testorganisms to water containing onlyone pesticide at a time. Most of thesamples tested in this study containedmixtures of more than 7, and as manyas 22, different pesticides. The toxicityof combinations of pesticides is largelyunknown, but there is some potentialfor additive or interactive effects.

Pesticides were detected in all butone of the 143 surface-water samplescollected during calendar year 1993from four sites—Orestimba Creek,Salt Slough, Merced River, and SanJoaquin River near Vernalis. Thesesites were selected to evaluate how thconcentrations of dissolved pesticidesvary in contrasting parts of the basinand during different seasons (Panshinand others, in press).

6 Water Quality in the San Joaquin–Tulare

n

Forty-nine of the 83 pesticidesanalyzed for were detected. The mostcommonly occurring ones were theherbicides simazine, dacthal, metol-achlor, and EPTC, and the insecticidesdiazinon and chlorpyrifos. Concentra-tions of the detected pesticides usuallywere low, but highly variable: medianconcentrations of the six most fre-quently detected pesticides rangedfrom 0.004µg/L for dacthal to 0.050µg/L for simazine, and 10 pesticideshad maximum concentrations greaterthan 1µg/L. Over half of the pesticidesdetected have no established aquatic-life criteria, and the potential for thesecompounds to induce toxicity, endo-crine disruption, or impaired immuneresponse is not well known.

Detections of pesticides insurface waters are related towhere and when pesticidesare applied

The California Department ofPesticide Regulation maintainsdetailed information on pesticideapplication. This information includestype of compound, location, date,amount applied, and target crop foreach pesticide application. The vast

majority of pesticide application in theStudy Unit is for agricultural use.

Seventy percent (38 of 54) of thepesticides with known applicationwere detected. Detection frequency isalso related to the amount of pesticideapplied; 4 of the 6 most commonlydetected pesticides were among the 1most heavily applied of the pesticidesanalyzed: chlorpyrifos, diazinon,EPTC, and simazine.

There is often a correspondencebetween the time a pesticide wasapplied and when, and at what con-centration, it was detected (Panshinand others, in press). The maximumapplication and occurrence generallycoincided for 19 pesticides (forexample, EPTC), usually during thesummer irrigation season. In contrast,several pesticides (for example, chlor-pyrifos) attained their maximum con-centration in streams during winterrunoff rather than at the time ofmaximum application. This indicatesthat, in some cases, winter runoff wasmore efficient than irrigation returnflows at transporting pesticides fromthe site of application to a stream.During the autumn there is neitherrainfall nor irrigation, resulting inrelatively few detections.

Basins, California, 1992–95

MAJOR ISSUES AND FINDINGS—Pesticides in the San Joaquin River Basin

f

Some pesticides were detected frequently in samples from all three subbasins, whereasother pesticides were detected in samples from only one or two subbasins.

Data for monthly pesticide application in the San Joaquin River Basin and concen-tration in samples in the San Joaquin River near Vernalis show that the occurrenceand application are often related in the summer, whereas the concentration maypeak in the winter in spite of heavier application in the summer.

80

20

0

40

60

APPLIEDDISCHARGEDETECTEDNOT DETECTED

30

10

0

20

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

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

1993

DIS

CH

AR

GE

, IN

TH

OU

SA

ND

CU

BIC

FE

ET

PE

R S

EC

ON

D

CH

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PY

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OS

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PLI

CA

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N,

IN T

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US

AN

D P

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IVE

ING

RE

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NT

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CA

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N, I

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HO

US

AN

DP

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IVE

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RE

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1993

10

8

6

4

2

0

10

8

6

4

2

0

0.06

0.20

0

0

EP

TC

CO

NC

EN

TR

AT

ION

,IN

MIC

RO

GR

AM

S P

ER

LIT

ER

0.05

0.10

0.15

CH

LOR

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EN

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MIC

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ER

LIT

ER

0.02

0.04

0 1000 50

SimazineDiazinon

EPTCDacthal

MetolachlorChlorpyrifos

CyanazineAtrazine

DiuronCarbaryl

TrifluralinDDE, p,p’-

PebulateAlachlor

PropargiteMolinateFonofos

MalathionNapropamide

DieldrinMethomyl

Pronamide

PE

ST

ICID

E

0 1000 50

DETECTION FREQUENCY, IN PERCENT

0 1000 50

Orestimba Creek

.t

e

-

Crop type and basincharacteristics affect spatialand seasonal variability ofpesticide occurrence

Orestimba Creek is typical of thesmall western tributaries to the SanJoaquin River where streamflow ispredominantly agricultural runoffduring the summer, but may alsoinclude large amounts of runoff fromthe nonagricultural Coast Rangesduring the winter. A greater variety ofpesticides were detected here (28herbicides and 12 insecticides) com-pared with the other sites. During thewinter, high concentrations of somepesticides occur for brief periodsbecause of transport by rainfall runoff(see the following section andDomagalski and others, 1997). Duringthe irrigation season, a large number opesticides—usually greater than15—were detected (Panshin andothers, in press). Pesticides detectedmore frequently in Orestimba Creekthan at the other sites include DDE,dieldrin, fonofos, napropamide, and

propargite. The presence of thesepesticides is attributed to past or pre-sent application primarily on dry beansand truck crops.

Salt Slough drains a low-lying partof the San Joaquin Valley, which

U.S. Geol

Salt Slough Merced River

includes large areas of wetlands andcotton; the slough does not have asignificant upland area within its basin,and its streamflow is dominated byagricultural drainage much of the year.Twenty-five herbicides and eightinsecticides were detected at this sitePesticides detected more frequently aSalt Slough than at other sites wereatrazine, cyanazine, diuron, EPTC,malathion, and molinate. The presencof these pesticides is attri-buted toapplication primarily on cotton, rice,alfalfa, and truck crops.

The Merced River is one of threetributaries that carry runoff from theSierra Nevada year round, often asreservoir release, and runoff from agricultural areas during the summer.Although 26 pesticides were detectedin this river, the frequency of detectionand concentrations were usually muchlower than corresponding levels in theother two basins. This relatively lowoccurrence is due to a combination offactors: the generally coarse-grainedsoils of the eastern San Joaquin Valleyresult in little surface runoff duringrainfall or irrigation; and pesticidesthat do reach the Merced River arediluted by the release of the relativelypesticide-free water from a reservoir inthe Sierra Nevada foothills.

ogical Survey Circular 1159 7

MAJOR ISSUES AND FINDINGS—Sources and Transport of Pesticides in the San Joaquin River Basin

StanislausRiverBasin

TuolumneRiverBasin

MercedRiverBasinBear

CreekBasin

OrestimbaCreekBasin

s

trations at the San Joaquin River near Vernalis exceeded concentrations toxic to aquaticram per liter) only during January and February because of storm runoff.

Almond orchard spraying (photograph by Dave Kim,tion).

San Joaquin River Basin showingboundaries of Orestimba Creek, BearCreek, Merced River, Tuolumne River,and Stanislaus River Basins (almondorchards shown in green).

the total agricultural application of diazinon ind during two dry periods preceding storms.

J F M3 1994

0

5,000

0

1,000

2,000

3,000

4,000

DIA

ZIN

ON

AP

PLI

CA

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N, I

N P

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S P

ER

DA

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January1994Storm

February1994Storm

PRECIPITATIONDIAZINON APPLICATION

M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A1991 1992 1993 1994

YEAR

2,000

0

4,000

6,000

8,000

10,000 D

AIL

Y M

EA

N D

ISC

HA

RG

E,

IN C

UB

IC F

EE

T P

ER

SE

CO

NDDISCHARGE

CONCENTRATION

The organophosphate insecticidediazinon is used for many agriculturaland urban applications. The main agrcultural application of diazinon in theSan Joaquin River Basin occurs duringthe winter to control wood-boringinsects in dormant almond orchards.This application period coincides withthe rainy season.

Concentrations of diazinonduring storm runofffrequently exceeded toxiclevels

Diazinon concentrations duringwinter storm runoff in OrestimbaCreek, and in the Merced, Tuolumne,and San Joaquin Rivers frequentlyexceeded 0.35µg/L, a concentrationshown to be acutely toxic to water fleas(Kuivila and Foe, 1995; Domagalskiand others, 1997; Kratzer, 1997).Although this level is acutelytoxic to water fleas,the effect on otherorganisms is largelyunknown. Concentra-tions in the StanislausRiver never exceeded0.35µg/L. On thebasis of daily samplesfrom the San JoaquinRiver during 1991–94,diazinon concentra-tions only exceeded0.35µg/L during Janu-ary and Februarystorm runoff (Mac-Coy and others, 1995).

Diazinon concenlife (0.35 microg

California Department of Pesticide Regula

F M A

1.2

0.2

0

0.4

0.6

0.8

1.0

DIA

ZIN

ON

CO

NC

EN

TR

AT

ION

,IN

MIC

RO

GR

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S P

ER

LIT

ER


i-

Transport ofdiazinon in the SanJoaquin River isrelated to timing ofdiazinonapplicationand storms

The main factorsinvolved in the transportof diazinon in the SanJoaquin River are thetiming of diazinon appli-cations and the occurrenceof sizable storms duringJanuary and February.During 1991–93, 74 per-cent of diazinon transportin the San Joaquin Riveroccurred during Januaryand February. In 1994, about half ofthe diazinon application in agri-cultural areas of the San Joaquin RiveBasin occurred during two dry periodspreceding sampled storms during

About half of1994 occurre

D199

0

1.0

0

0.2

0.4

0.6

0.8

PR

EC

IPIT

AT

ION

, IN

INC

HE

S P

ER

DA

Y


r

January and February. The overallamount of diazinon transported in theSan Joaquin River during these stormwas only about 0.05 percent of theamount applied during the precedingdry periods.

MAJOR ISSUES AND FINDINGS—Sources and Transport of Pesticides in the San Joaquin River Basin

t-

d

d

y

Most diazinon in the San Joaquin River comes from west-side creeks, theTuolumne and Merced Rivers, and direct drainage from the east side.

d

EXPLANATION1

0.0050.010.020.05

0.10.20.5

CO

NC

EN

TR

AT

ION

, M

ICR

OG

RA

MS

P

ER

LIT

ER

7 138 9 10 11 12

FEBRUARY 1994

0

6

0

1

2

3

4

5

DIA

ZIN

ON

LO

AD

, IN

PO

UN

DS

AC

TIV

E IN

GR

ED

IEN

T P

ER

DA

Y

MERCED RIVER

OTHER EAST-SIDE CREEKS

AND BEAR CREEK

BEAR CREEK

SAN JOAQUIN RIVER

TOTAL

WEST-SIDE CREEKS

WEST-SIDE CREEKS

AND OTHER

EAST-SIDE CREEKS

STANISLAUS RIVER

TUOLUMNE RIVER

OTHER EAST-SIDE

CREEKS

A dye-tracer study was done duringthe February 1994 storm to estimatetraveltimes in the San Joaquin Riversystem (Kratzer and Biagtan, 1997).On the basis of storm sampling during1993–94 and estimated traveltimes,ephemeral west-side creeks probablywere the main diazinon source earlyduring the storms, whereas theTuolumne and Merced Rivers and easside drainages directly to the SanJoaquin River were the main sourceslater (Domagalski and others, 1997;Kratzer, 1997).

More pesticides weredetected in runoff from urbanareas than from agriculturalareas in the Tuolumne RiverBasin, but pesticide transportwas usually greater in runofffrom agricultural areas

The occurrence, concentrations, antransport of dissolved pesticides instorm runoff were compared in theTuolumne River Basin for two landuses: agricultural areas and theModesto urban area. Both stormsfollowed the main application periodof pesticides on dormant almondorchards. Six pesticides were detectein runoff from agricultural areas, and15 pesticides were detected in runofffrom urban areas. Chlorpyrifos,diazinon, DCPA, metolachlor, andsimazine were detected in almost eversample. Median concentrations werehigher in runoff from urban areas for

Sampling a storm drain duringFebruary 1995 storm (photograph byCharles R. Kratzer, U.S. GeologicalSurvey).

all pesticides except napropamide andsimazine. The lower occurrence andconcentrations in agricultural runoffwas partly attributed to dilution bynonstorm base flow in the TuolumneRiver and by storm runoff fromnonagricultural land (primarily nativevegetation) (Kratzer, in press).

Transport of chlorpyrifos, diazinon,metolachlor, napropamide, andsimazine was greater from agriculturalareas than from urban areas. Transportof DCPA was about the same fromagricultural and urban areas. The main

source of transport for the otherpesticides could not be determined.

In most cases, the occurrence andrelative concentrations of pesticides instorm runoff from agricultural andurban areas were related to pesticideapplications. Some pesticides detectefrequently, and in relatively highconcentrations, in the storm drains didnot relate to reported use. However,unlike agricultural use, reporting ofpesticide use in urban areas isincomplete and only includes use bylicensed pest control operators.


More pesticides were detected, and generally in higher concentrations, in stormrunoff from urban areas compared with storm runoff from agricultural areas.

0

100

0

20

40

60

80

DE

TE

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ION

FR

EQ

UE

NC

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ER

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Ben

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Car

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Pro

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PESTICIDE

0.0010.002

ME

DIA

NIN

MAJOR ISSUES AND FINDINGS—DDT and Other Persistent Organochlorine Pesticides in SuspendedSediment, Bed Sediment, and Tissue of Biota

5 MILES

5 KILOMETERS0

0

EAST-SIDE SITE

WEST-SIDE SITE

MUD AND SALT SLOUGH SITES

SAN JOAQUIN RIVER SITES

EAST-SIDE SITES

WEST-SIDE SITES

MUD AND SALT

SAN JOAQUIN

Stanisl

aus River

TuolumneRiver

Merced River

HospitalCreek

San

River

Salt

MudLos

Banos

Slough

Slough

Joaquin

Ingr

amCre

ek

DelPuert

o Creek

Orestimba Creek

Turlock IrrigationDistrict Lateral 5

Olive Ave.Drain

SpanishGrantDrain

NewmanWasteway

Creek

t

ic

t

Mud and Salt Sloughs sites (2 sites)

Compound Tissue Bed Sediment

Total DDT 79–342 1–7

Dieldrin ND–6 ND

The concentration and variety of organochlorine insecticides in tissue and bed sedimentwere highest in west-side sites, intermediate in the San Joaquin River sites, and lowest ineast-side sites. (Red values – exceeded guidelines for the protection of fish-eating wildlife[National Academy of Sciences and National Academy of Engineering, 1973]. NA – notanalyzed; tissue and sediment values in micrograms per kilogram, wet and dry weight,respectively; ND – not detected).

d

East-side sites (8 sites)


Total DDT 6–101 ND–50

Chlordane ND ND–9

.West-side sites (3 sites)


Total DDT 509–2,192 109–415

Toxaphene ND–2,000 ND–630

Dieldrin ND–10 1–10

Dacthal 11–360 ND–32

PCBs ND–57 ND

Permethrin NA ND–31

San Joaquin River sites (3 sites)


Total DDT 50–510 ND–13

Toxaphene ND–160 ND

Dieldrin ND–5 ND

Dacthal ND–33 ND

PCBs ND–57 ND

Organochlorine insecticides, such aDDT and toxaphene, were usedextensively in the San Joaquin Valleyto control agricultural pests. The use ofsuch compounds was banned in the1970s in the United States because odetrimental effects on wildlife, such asthe bald eagle and peregrine falcon.These chemicals are persistent in theenvironment because they degradeslowly and are tightly bound to soilparticles. Contaminated soils fromagricultural and urban areas containingthese compounds are still enteringstreams because of soil erosion. Oncecontaminated soil has entered a streamas sediment, it becomes available to avariety of small aquatic organisms,such as insects that obtain food fromthe water or bed sediment. Theseorganisms then are eaten by largerorganisms, resulting in the contam-inants being passed up the food chainin processes known as bioaccumu-lation. This process can result inconcentrations of organochlorinecompounds in fish and other biota thaare harmful to wildlife and humansthat consume them.

Concentrations of DDT andorganochlorine insecticidesin aquatic organisms and bedsediment still exceedguidelines for protection offish-eating wildlife

Studies done during the 1970s and1980s documented contamination ofboth stream bed sediments and aquatorganisms in the San Joaquin Riversystem. In those studies, levels oforganochlorine insecticides in the SanJoaquin Valley were high comparedwith other parts of the Nation, andlevels in aquatic organisms exceededguidelines for the protection of fish-eating wildlife in several areas (Brown,1997). In October 1992, samples oftissue of aquatic organisms and fine-grained bed sediment were collected a18 sites and analyzed to determinewhether the distribution orconcentrations of organochlorineinsecticides had changed from theearlier studies.


s

f

Concentrations of organochlorineinsecticides in aquatic organisms andbed sediment were highest in the smawestern tributaries to the San JoaquinRiver and in the lower part of the SanJoaquin River (Brown, 1997). Concentrations in these areas were still highcompared to national values from the1970s and 1980s. Concentrations intissue and sediment at the west-sidesites were among the highest encountered at NAWQA Study Units. Com-parison of 1992 data with data thatwere available for some sites showedevidence of a decline in concentrationsin tissue at those sites. Bed-sedimentconcentrations appeared similar tohistorical data, but the historical datawere collected using differentmethods, making direct comparisonsdifficult. There was a strongcorrelation between concentrations of


EXPLANATION

DDT in tissue (of clams and fish) andin bed sediment, suggesting thatbioaccumulation was taking place(Brown, 1997).

The results of these comparisonsindicate that, though these insecticideconcentrations might be declining,they may adversely impact aquaticorganisms, and hence other wildlife, inthe San Joaquin Valley for years tocome. An additional potential impactof these compounds has been revealeby recent studies that suggest thatorganochlorine insecticides can beharmful to the hormone (endocrine)and immune systems of wildlife andhumans at much lower concentrationsthan was previously thought (Colbornand Clement, 1992).

ll

-

-

MAJOR ISSUES AND FINDINGS—DDT and Other Persistent Organochlorine Pesticides in SuspendedSediment, Bed Sediment, and Tissue of Biota

of total DDT were substantially greater ins collected during winter runoff comparedmples collected during irrigation seasonites except Hospital Creek.

Most whole-water concentrations oftoxaphene exceeded the USEPAchronic criterion for protection offreshwater aquatic life.

0.01 10,0000.1 1 10 100 1,000

INSTANTANEOUS LOADSOF TOTAL DDT,

IN GRAMS PER DAY

Spanishrant Drain

an JoaquinRiver

NewmanWasteway

OrestimbaCreek

ive AvenueDrain

Del PuertoCreek

IngramCreek

HospitalCreek

IRRIGATION SEASONWINTER RUNOFF

0.0001 100.001 0.01 0.1 1CALCULATED WHOLE-WATER

CONCENTRATION OF TOXAPHENE,IN MICROGRAMS PER LITER

USEPAChronicCriterion

USEPAAcute

Criterion

CaliforniaDrinkingWater

Standard

DetectedNot detected

Not detected

Detected

IRRIGATION SEASON

WINTER RUNOFF

NewmanWasteway

Olive AvenueDrain

SpanishGrant Drain

OrestimbaCreek

Del PuertoCreek

IngramCreek

HospitalCreek

San JoaquinRiver

SA

MP

LIN

G S

ITE

eek during a winter storm (left) and irrigation) (photographs by Sylvia V. Stork and Charles.S. Geological Survey, respectively).

Large amounts ofsediment-bound DDT andother organochlorineinsecticides are trans-ported from small west-side tributaries to the SanJoaquin River duringwinter storms

NAWQA did studies on thewest-side tributaries and mainstem of the San Joaquin River todetermine the processes con-trolling transport of sediment-bound pesticides. Samples ofsuspended sediment were anal-yzed for 15 organochlorineinsecticides to compare transportduring the irrigation season (June1994) with transport duringwinter storm runoff (January1995) (Kratzer, 1998).

The most frequently detectedorganochlorine insecticidesduring both the winter storm runoffand irrigation season werep,p -DDE,p,p -DDT, p,p -DDD, dieldrin, toxa-phene, and chlordane. Aldrin, endrin,mirex, and lindane also were detectedduring the winter storm runoff; lindanewas also detected during the irrigationseason.

Median concentrations of totalDDT, chlordane, dieldrin, and toxa-phene on suspended sediment wereslightly greater during the irrigationseason than during winter storm run-off. However, streamflows, suspendedsediment concentrations, and instant-aneous loads were substantially greateduring the winter storm runoff.

Most of the calculated whole-waterconcentrations ofp,p -DDT, chlor-dane, dieldrin, and toxapheneexceeded the USEPA chronic criteriafor the protection of freshwater aquaticlife (U.S. Environmental ProtectionAgency, 1986). In addition, 6 of 16toxaphene and 1 of 16p,p -DDTconcentrations exceeded USEPA acutcriteria for the protection of freshwateraquatic life (U.S. Environ-mentalProtection Agency, 1986), and 5 of 16chlordane and 1 of 16 toxapheneconcentrations exceeded California

Loads samplewith saat all s

G

S

Ol

SA

MP

LIN

G S

ITE

drinking-water standards (CaliforniaDepartment of Water Resources,1995).

Although controllingirrigation-induced soil ero-sion will reduce the transportof organochlorine insecti-cides, it will not eliminateorganochlorine insecticidesfrom the San Joaquin Riverbecause of transport duringwinter storms

Estimated loads oforganochlorine insect-icides for the entire irriga-tion season exceededestimated loads for theJanuary 1995 storm byabout 2 to 4 times forsuspended transport andabout 3 to 11 times fortotal transport. However,because the averagewinter runoff is 2 to 4times the runoff duringthe January 1995 storm,average winter transportof organochlorineinsecticides may be

-

r

e

Orestimba Crseason (rightR. Kratzer, U

U.S. Geo

similar to irrigation season transport.The average winter transport is alsodependent on long-term seasonalvariations in suspended-sediment andorganochlorine insecticide concen-trations, both of which are unknown.Nevertheless, these findings indicatethat runoff from winter storms willcontinue to deliver a significant load ofsediment-bound organochlorineinsecticides to the San Joaquin Riverfor an indeterminate amount of time,even if irrigation-induced soil erosionis reduced.

logical Survey Circular 1159 11

MAJOR ISSUES AND FINDINGS—Nutrients in the San Joaquin River

5 MILES

5 KILOMETERS0

0

121 00'121 15'

37 45'

37 15'

BearCreek

Merced River

LosB

anosC

reek

Mud

Slough

Newman Wasteway

San

JoaquinRiver

Salt Slough

Ore

stim

baCre

ek

Ingr

amC

reek

Tuolumne

River

Hospital

Sacramento-San Joaquin

Delta

Stanis

laus River

SanJoaquin River

Turlock Irrigation District lateral 5Spanish Grant Drain

Creek

Del Puerto

Creek

STANISLAUS C

O

STANISLAUS CO

MERCED CO

MERCED C

O

SAN JO

AQUIN C

O

5,000

ANNUAL NITRATE LOADS, IN TONS PER YEAR (AS N)

4,000

3,000

2,000

1,000

0

Wid

th o

f col

or b

ar

Ton

s pe

r ye

ar a

s N

1986 (wet year)1988 (dry year)OVERLAP OF 1986 AND 1988

STUDY UNIT BOUNDARYSITE LOCATION

San Joaquin Rivernear Vernalis

San Joaquin Riverat Patterson

San Joaquin Rivernear Newman

Modesto

f

r

.

.

t

f

During both dry and wet years, much of the nitrate load in the San Joaquin River canbe attributed to subsurface agricultural drainage discharged to Mud and Salt sloughs.

Nitrogen and phosphorus areessential nutrients for aquatic plants.However, in high concentrations, theycan cause excessive plant growth(eutrophication) and toxicity to infants(“blue baby syndrome” or methemo-globinemia from ingestion of nitrate).The USEPA has set criteria for thenitrate and ammonia forms of nitrogen,but not for phosphorus. The maximumcontaminant level (MCL) for nitrate indrinking water is 10 milligrams perliter as nitrogen (mg/L as N) (U.S.Environmental Protection Agency,1986).

The USEPA also has establishedcriteria for maximum ammonia con-centrations in surface water on thebasis of chronic and acute exposure oaquatic organisms to un-ionizedammonia (U.S. Environmental Protec-tion Agency, 1986). These criteria varyinversely with pH and temperature.The chronic criteria range from about0.2 to 2 mg/L as N for the range of pH(7.5–8.5) and temperatures (5–25°C)generally found in surface water in theSan Joaquin Valley.

Mud and Salt Sloughsaccount for nearly half of thenitrate in the San JoaquinRiver

Nutrient concentrations in the lowerSan Joaquin River are determinedprimarily by relatively concentratedinputs from west-side agriculturaldrainage, east-side wastewater-treatment plants and runoff fromdairies, and relatively dilute inputsfrom major east-side tributaries. Mudand Salt sloughs receive a part of theiflow from subsurface drains that drainabout 60,000 acres of agricultural landAlthough the sloughs account for onlyabout 10 percent of the streamflow inthe San Joaquin River near Vernalis,the subsurface drainage is very high innitrate (about 25 mg/L as N), and thesloughs contribute nearly one-half thenitrate (Kratzer and Shelton, in press)The nitrate transported in the SanJoaquin River during a wet year (1986)was about 50 percent more than thattransported in a dry year (1988).

The nitrate MCL was exceeded inSpanish Grant Drain, TurlockIrrigation District lateral 5, and


Orestimba Creek in 15, 11, and 9percent, respectively, of samplescollected between April 1993 andMarch 1995. However, these tribu-taries are not designated as drinking-water sources. The MCL was notexceeded during this period in themain stem of the San Joaquin River, adesignated drinking-water source.

Nitrate concentrations in theSan Joaquin River have beenincreasing during the last 40years

Increasing nitrate concentrations inthe San Joaquin River could beattributed to several sources,

including subsurface agriculturaldrainage, runoff from fertilizerapplications, wastewater-treatmentplant effluent, and runoff from dairies.The relative contribution of thesesources was evaluated with estimatesof nitrate loads and with trends inammonia and phosphorusconcentrations. Wastewater- treatmenplant effluent and runoff from dairieshave especially high concentrations oammonia and phosphorus, yetconcentrations of ammonia andphosphorus in the San Joaquin Rivergenerally declined or remained stablewhile nitrate concentrations steadilyincreased.


MAJOR ISSUES AND FINDINGS—Nutrients in the San Joaquin River

tt

f

The flow-adjusted nitrate concentration in the San Joaquin River has increased fromabout 0.3 to 1.4 milligrams per liter (mg/L) over the last four decades.

Nitrate loads in the San Joaquin River from subsurface agricultural drains haveincreased steadily since the 1950s.

Nitrate concentration in the SanJoaquin River have steadily increasedwhile ammonia concentration hasdeclined since 1984.

3.2

1.6

0

19601950 1970 1980 1990

FLO

W-A

DJU

ST

ED

N

ITR

AT

E C

ON

CE

NT

RA

TIO

N,

IN M

ILLI

GR

AM

S P

ER

LIT

ER

, AS

N

WATER YEAR

TRENDUSGSSTORET

1950 1960 1970 1980 1990

8,000

6,000

4,000

2,000

0

ESTIMATED NITRATE LOADS IN SAN JOAQUIN RIVER NEAR VERNALIS (5-year running averages)

OTHER SOURCES

SUBSURFACE AGRICULTURAL DRAINS

EAST-SIDE TRIBUTARIESSan Joaquin River total

NIT

RA

TE

, IN

TO

NS

PE

R Y

EA

R, A

S N

1970 19901975 1980 1985YEAR

2

1

FLO

W-A

DJU

ST

ED

NIT

RA

TE

,IN

MIL

LIG

RA

MS

PE

R L

ITE

R, A

S N 0.20

0.15

0.10

0.05

00F

LOW

-AD

JUS

TE

D A

MM

ON

IA,

IN M

ILLI

GR

AM

S P

ER

LIT

ER

, AS

NNITRATEAMMONIA

The source of the nitrate increaseduring the 1950s was indeterminate.During the 1960s, runoff from ferti-lizer applications (primarily in east-side basins) and subsurface agricul-tural drainage were the probablesources of the increase. Since 1970,subsurface agricultural drainage hasbeen the primary cause of theincreasing nitrate trend (Kratzer andShelton, in press). Other studies havedetermined that the nitrate in the sub-surface agricultural drainage primarilycomes from the leaching of native soilnitrogen and not from fertilizer appli-cation (Brown, 1975). Other sources ofnitrate loads were especially importanin the early 1980s because of the effecof an extremely wet year (1983) on the5-year running averages. Theunusually large inputs of nitrate in1983 were probably from (1) inflowfrom the Tulare Basin through theFresno Slough, (2) discharge fromwastewater-treatment plants, (3) runoffrom dairies, and (4) runoff fromfertilizer applications west of the SanJoaquin River (Kratzer and Shelton, inpress). Despite this long-term increasein the San Joaquin River, nitrateconcentrations are still well below theUSEPA drinking-water standard.

Ammonia criteria werefrequently exceeded inTurlock Irrigation Districtlateral 5 and occasionallyexceeded in Orestimba Creekand Spanish Grant Drain

On the basis of monthly samplescollected during 1985–88, ammoniaconcentrations in the San JoaquinRiver increased from Newman toPatterson, then declined fromPatterson to Vernalis as a result ofdilution by the Tuolumne and Stanis-laus Rivers (Kratzer and Shelton, inpress). The increase from Newman toPatterson is attributed to relativelyconcentrated inputs, such as TurlockIrrigation District lateral 5, OrestimbaCreek, and Spanish Grant Drain. Mosof the flow in Turlock IrrigationDistrict lateral 5 is effluent from theTurlock wastewater-treatment plant,especially during the nonirrigationseason. Ammonia concentrations

t

exceeded the USEPA chronic criteriain 2 of the 51 samples collected at theSan Joaquin River at Patterson during1985–88.

Ammonia concentrations in TurlockIrrigation District lateral 5, OrestimbaCreek, and Spanish Grant Drainexceeded the USEPA chronic criteriain 76, 14, and 5 percent, respectively,of samples collected between April1993 and March 1995. None of thesamples collected at the San JoaquinRiver at Patterson during April 1993 toMarch 1995 had ammonia concentra-tions that exceeded the USEPA chroniccriteria, but some concentrations werejust under the criteria.

Unlike nitrate, ammonia concentra-tions at the San Joaquin River nearVernalis did not increase from 1974 to1990. Instead, ammonia concentra-tions increased until 1984, thendeclined. This decrease was probablydue to a combination of factors,including conversion of ammonia to

U.S. Geol

nitrate by improved wastewatertreatment, reduced discharges fromwastewater-treatment plants due to asequence of dry years during the late1980s and expanded use of landdisposal, and reduced inputs fromdairies during the sequence of dryyears (Kratzer and Shelton, in press).


MAJOR ISSUES AND FINDINGS—Fish Communities, Stream Habitat, andWater Quality in the San Joaquin River Drainage

Native species

San Joaquin Main Stem species

Largemouth bass and sunfish

Catfish

Smallmouth bass

Other introduced species

San Joaquin Main StemSan Joaquin

Lower Tributary

Stanislaus River

Upper Tributary

5 10 MILES

5 100

0

Ripon

ModestoVernalis

Patterson

Gustine

Riverbank

Knights Ferry

Waterford

Merced

Merc

edRiver

OrestimbaCre

ek

Tuolumne River

SanJoaquin

River

Stanislaus River

SC CF AL0

60

0

20

40

ME

AN

PE

RC

EN

TA

GE

OF

MA

XIM

UM

VA

LUE

Lower Tributary group

Habitat variablesHabitat variables Fish communityFish communitySC CF AL

0

60

0

20

40

ME

AN

PE

RC

EN

TA

GE

OF

MA

XIM

UM

VA

LUE

San Joaquin Main Stem group

SC CF AL0

60

0

20

40

ME

AN

PE

RC

EN

TA

GE

OF

MA

XIM

UM

VA

LUE

SC CF AL0

60

0

20

40

ME

AN

PE

RC

EN

TA

GE

OF

MA

XIM

UM

VA

LUE

Habitat variables Fish community Fish communityHabitat variables

KILOMETERS

EXPLANATION

FISH TYPES

SITE GROUPS

s

d

.

At the 20 lower elevation sites, fish communities, habitat, and water chemistry variedsignificantly among the site groups. (SC – Specific conductance; CF – Cover for fish;AL – Agricultural land).

Human activities, including devel-opment of water resources, agricultureand urbanization in the San Joaquin–Tulare Basins, have been accompa-nied by large-scale changes in aquaticecosystems. Populations of anadro-mous salmon have declined, alongwith other migratory and residentnative species. Though there are likelymany reasons for the decline, the roleof water chemistry and habitat degra-dation have not been assessed on abasin-wide scale. Fish communitieswere sampled in the San Joaquin–Tulare Basins to determine their statusand whether they provided useful indications of water chemistry and habitatconditions.

Introduced fish speciesoutnumber native speciesalmost 2 to 1, indicatingimpaired habitat or waterchemistry or both

Assessments of fish communitieswere made at 32 sites during Augustand September from 1993 to 1995.Fish were collected and identified tospecies, and habitat and water-chemistry data were collected at eachsite (Meador and others, 1993a,b).A total of 34 species of fishwere collected. Twelvespecies were native toCalifornia and 22 specieswere introduced fromoutside California. Nativespecies were generallymore abundant at higherelevation sites in the valley, thefoothills, and the Sierra Nevada.Introduced species were generallymore abundant at lower elevation siteon the valley floor. High percentagesof introduced species are consideredan indication of impaired water chem-istry and habitat conditions (Hughesand Gammon, 1987; Karr, 1991).

Using the fish data collected, groupsof sites with similar relative abun-dances of fish species were definedusing statistical techniques. Thisanalysis was done twice: once for the20 low-elevation sites most likely to beaffected by human activities, and oncefor all of the 32 sites sampled.


Stanislaus River group Upper Tributary group

,

s

-

The 20 low-elevation sites were allin the lower San Joaquin River drain-age, downstream from the major foot-hills reservoirs. Four groups of siteswere identified on the basis of fishcommunities, water chemistry, andhabitat quality: a San Joaquin MainStem group, a Lower Tributary group,a Stanislaus River group, and an UpperTributary group.

The San Joaquin Main Stem groupwas characterized by high percentagesof introduced species tolerant of harshenvironmental conditions, particularlythe fathead minnow, red shiner,threadfin shad, and inland silverside(all referred to as the San JoaquinMain Stem species). The San JoaquinMain Stem group included eight siteson the main stem of the San Joaquin

River and on small western andsouthern tributary streams. Specificconductance (an indicator of salinity),which was highest at these sites, is agood indicator of general waterchemistry and of the influence ofirrigation return flows in the SanJoaquin River drainage. Fishcover—the percentage of area thatprovides cover from predators—waslowest at these sites. Environmentaldegradation, as indicated by increasespecific conductance and decreasedfish cover, was related to humanactivities such as agricultural land useThe Lower Tributary group wascharacterized by high percentages ofintroduced largemouth bass, redearsunfish, and white catfish. These siteswere located in the lower and middle


MAJOR ISSUES AND FINDINGS—Fish Communities, Stream Habitat, andWater Quality in the San Joaquin River Drainage

r

t

-

-r

he Stanislaus River has good riparianam habitat, and water chemistryy Larry R. Brown, U.S. Geological Survey).

and instream habitats are good at Orestimbaut because water chemistry is poor andns in flow are substantial, the site had a highge of introduced fish species (photograph byBrown, U.S. Geological Survey).

reaches of the Merced andTuolumne Rivers, but only thefarthest downstream site onthe Stanislaus River. Valuesof specific conductance, fishcover, and agricultural landuse were intermediatebetween the Upper Tributaryand San Joaquin Main Stemgroups.

The Upper Tributarygroup included the farthestupstream site on the Stan-islaus and Merced Rivers,and the two farthest up-stream sites on theTuolumne River. Thesesites were characterized by highpercentages of the native species:Sacramento squawfish, hardhead,Sacramento sucker, and prickly scul-pin. Specific conductance and agri-cultural land use were lowest at thesesites, and fish cover was highest.

The two middle sites on the Stanis-laus River formed a separate groupcharacterized by high percentages ofintroduced smallmouth bass and nativetule perch. Water chemistry and habitawere similar to the Upper Tributarysites.

The second analysis, which wasbased on the fish data from all 32 sitesalso resulted in four groups of sites: aSan Joaquin Main Stem group, a Foohill group, a Lower Tributary group,and a Sierra Nevada group. The SanJoaquin Main Stem group was identi-cal and the Lower Tributary group verysimilar to the groups obtained using 20sites. The Foothill group included allbut one site in the previously definedUpper Tributary group, the StanislausRiver group, and additional siteslocated upstream from the foothill res-ervoirs. These sites were characterizeby native Sacramento squawfish, hardhead, tule perch, scul-pins, and intro-duced smallmouth bass. The SierraNevada group was dominated bynative rainbow trout and introducedbrown trout. Water chemistry and habitat conditions were very differentamong site groups, as would beexpected in a study that included

RiparianCreek, bfluctuatiopercentaLarry R.

t

,

t-

d-

-

small, cold, high-elevation streams andlarge, warm, low-elevation rivers.Thus, these groups are most indicativeof large-scale, natural gradients andless related to environmental impair-ment than the groups obtained fromthe analysis of 20 low-elevation sites.

Native species are moresuccessful in the majoreastern tributaries whenflows are higher

Overall environmental quality isreflected by fish communities: nativespecies are common at the least alteresites, and tolerant introduced speciesare common at the most altered sites.However, the influences of waterchemistry and habitat on fish com-munities could not be separatedbecause both sets of variables wererelated to land use (Brown and othersin press). Additional variables mayalso contribute to thispattern. Dissolved pesti-cide concentrations some-times reached levels toxicto some invertebrates,primarily at sites in theSan Joaquin Main Stemgroup. Similarly, concen-trations of organochlorineinsecticides in sedimentsand tissues of biota werehighest at sites in the SanJoaquin Main Stem group(Brown, 1997). Thedominance of tolerantintroduced species at

This site on thabitat, instre(photograph b

U.S. Geol

the San Joaquin main stem sites isconsistent with these patterns.

Environmental degradation due tohuman activities may have beenstressful to resident fish as indicated bythe high incidence of externalabnormalities, such as parasites andlesions, at the Lower Tributary sites(21 percent) and San Joaquin mainstem sites (17 percent). The incidenceof abnormalities was much lower at theStanislaus River (3 percent) and UppeTributary sites (3 percent). In otherareas of the country, an incidence ofexternal abnormalities greater than 2percent is considered an indicator ofimpaired conditions (Hughes andGammon, 1987; Karr, 1991).

The rarity of native fishes at theLower Tributary and San Joaquin mainstem sites may not be irreversible.High discharges in 1995 in the Mercedand Tuolumne Rivers were accompa-nied by higher percentages of residenand migratory native species. Statisti-cal analysis of data from sites sampledin more than one year indicated thatfish communities in 1993 and 1994were very similar, but in 1995 werevery different from the other years.Also, the greater abundance of nativespecies in the Stanislaus River, particularly tule perch, at downstream sitescompared with the other eastern tributaries, suggests that the higher summeflows favor native species. Furthermonitoring during different flow con-ditions could help determine condi-tions necessary to reestablish nativefish communities.

d

,


MAJOR ISSUES AND FINDINGS—Effect of Agriculture on Ground Water, Eastern San Joaquin Valley

a

r

-in

e

;

d

f

e

Characteristic

Median nitrate concentration, in milligrams(number of samples that exceeded the USwater standard in parenthesis)

Source: nitrogen applied within a 0.25-mile

Susceptibility: sediment texture

Susceptibility: potential for nitrate removal breactions (nitrate reduction)

Nitrate concentrations in 24 percent ofdomestic wells exceeded USEPAdrinking-water standards (RAS – regionalaquifer survey; VIN – vineyard land use;ALM – almond land use; CAV – corn,

Nitrate sources and aquifer susceptibility va .

RAS VIN ALM CAV

TYPE OF WELL

0.01

100

0.02

0.05

0.1

0.2

0.5

1

2

5

10

20

50

NIT

RA

TE

, IN

MIL

LIG

RA

MS

PE

R L

ITE

R

Drinking-waterstandard

Nationalbackgroundlevels

Ground water is the source of drink-ing water for most of the population ofthe eastern San Joaquin Valley. Eachyear, millions of pounds of nitrate (infertilizer and manure) and pesticidesare applied to cropland. Some of thesechemicals infiltrate to the water table,degrade the water quality, and poten-tially cause a public health risk.

The quality of ground water in thealluvial fans of the eastern San JoaquinValley was assessed by collecting datfrom three sets of wells: 30 domesticwells representative of the regionalaquifer, 60 shallow domestic wells inthree well-defined and contrastingagricultural land-use settings, and 20multilevel monitoring wells in a3.5-mile transect along a ground-wateflow path (see p. 24–25).

Nitrate concentrations inground water in the easternSan Joaquin Valley oftenexceeded the drinking-waterstandard

Nitrate concentrations in 24 percent(21 of 88) of the domestic wells sam-pled during 1993–95 in the regionalaquifer survey and land-use studies othe eastern San Joaquin Valleyexceeded the drinking-water standardof 10 mg/L established by the USEPA.Furthermore, ground-water samplesfrom 77 percent of the wells hadnitrate concentrations greater than2 mg/L, which is believed to representbackground concentrations (Muellerand Helsel, 1996). These findings indcate that ground-water quality hasbeen degraded over a large part of thiaquifer because of the input of nitratefrom human activity.

Ground-water samples collected in1995 from the 30 domestic wells in theregional aquifer survey (median welldepth 182 feet) had a median nitrateconcentration of 4.6 mg/L; 5 of the 30wells (17 percent) exceeded theUSEPA drinking-water standard. Themedian concentration of 4.6 mg/L washigher than the median of 2.4 mg/L forground water in similar alluvial set-tings with agricultural land use nation-wide (Mueller and others, 1995).


f

i-

s

Nitrate concentrations in groundwater sampled during 1993–95 fromshallow domestic wells (median welldepth 150 feet) were compared amongthree contrasting agricultural land-usesettings. These 60 wells (three sets o20) represent a part of the aquifer thais usually used as a domestic watersupply. Nitrate concentrations were thehighest in samples from the wells inthe almond land-use setting, whereasconcentrations were the lowest in samples from wells in the vineyard land-use setting. Nitrate concentrationswere intermediate in samples from agrouped land-use setting of corn,alfalfa, and vegetables. Median nitrateconcentrations in the three land-usesettings were greater than or equal to

alfalfa, and vegetable land use).


ft

-

the median in the regional aquifer sur-vey; therefore, some of the other landuse settings in the eastern San JoaquValley must have generally lowernitrate concentrations than these threagricultural settings.

Nitrate concentrations insamples from shallowdomestic wells were relatedto nitrate application,sediment texture, andpotential for nitrate removalby chemical reactions

Sources of nitrate from agricul-ture—fertilizer and manure—wereestimated for a 0.25-mile-radius circlecentered at each well in each of thethree agricultural land-use settings.Nitrate concentrations in ground waterin the three land-use settings wererelated to estimates of the amount ofnitrogen applied: the greatest amountof nitrogen was applied in the almondland-use setting; a slightly loweramount was applied in the corn,alfalfa, and vegetable land-use settingand the smallest amount was applied inthe vineyard land-use setting (Burowand others, in press, a). The estimateamount of nitrogen applied to individ-ual sites was not strongly related tonitrate concentrations in ground-watersamples from the wells, however.These results indicate that estimates othe amount of nitrogen applied are afair indicator of nitrate concentrationsfor an area; however, the estimates arnot a good predictor of concentrationin an individual well.

This lack of predictability probablyis due to several factors. The amount

Vine-yard Almond

Corn,alfalfa, veg-

etables

per literEPA drinking-

Low4.6(3)

High10(8)

Intermediate6.2(7)

radius Low7,300 lb

High19,900 lb

High16,400 lb

High High Low

y chemicalLow Intermedi-ate High

ry in the three agricultural land-use settings


-

s

l-

f

-

-f

n

Fertilizer use and median nitrate concentration in ground water have generallyincreased over the past four decades.

1950 20001950 1960 1970 1980 1990

YEAR

0

7

0

2

4

6

ME

DIA

N N

ITR

AT

E C

ON

CE

NT

RA

TIO

N,

IN M

ILLI

GR

AM

S P

ER

LIT

ER

0

1,000

0

200

400

600

800E

ST

IMA

TE

D N

ITR

OG

EN

FE

RT

ILIZ

ER

US

E,

IN M

ILLI

ON

PO

UN

DS

PE

R Y

EA

R

DECADE, (666) NUMBER OF SAMPLESESTIMATED FERTILIZER USE23 WELLS SAMPLED DURING 1986-87 AND IN 1995

(618) (1,038) (1,010) (666)

of coarse-grained sediments (sand- ogravel-sized) in the subsurface, whichis referred to as sediment texture, is amajor factor in the susceptibility of asite to nitrate contamination. The sediment texture influences the rates ofinfiltration and ground-water flow inthe aquifer, which controls how rapidlywater at the surface, with high nitrateconcentrations, can infiltrate the soiland move downward to a well in theaquifer. The sediment textures in thealmond and vineyard land-use settingswere generally coarse-grained andconducive to rapid infiltration andground-water flow. The sediment tex-ture in the corn, alfalfa, and vegetableland-use setting was generally fine-grained with abundant clay, resultingin slow rates of infiltration and ground-water flow.

These contrasts in sediment textureconsidered along with the contrasts inthe amount of nitrogen applied, indi-cate that nitrate concentrations inground water were highest where highsusceptibility and high amounts ofnitrogen applied occurred together (thealmond land-use setting); nitrate con-centrations in ground water were low-est where the amount of nitrogenapplied was low, even though the sus-ceptibility was high (the vineyard land-use setting); and nitrate concentrationin ground water were intermediatewhere the amount of nitrogen appliedwas high, but the susceptibility waslow (the corn, alfalfa, and vegetableland-use setting) (Burow and others, inpress, a).

Nitrate in ground water can also beremoved by biochemical reactionssuch as nitrate reduction, in whichnitrate is converted to nitrogen gas.These biochemical reactions can happen in ground water that has very lowconcentrations of dissolved oxygen.The chemical traits that indicate apotential for nitrate reduction, such aslow dissolved-oxygen concentrationsand high concentrations of iron andmanganese, existed in ground-watersamples from the corn, alfalfa, andvegetable land-use setting. The fewsamples that have these chemical traitdo in fact have low or nondetectable

r

-

,

s

nitrate concentrations. In contrast,there is little evidence of nitrate reduc-tion in samples from the almond andvineyard land-use settings. Therefore,ground water in parts of the corn,alfalfa, and vegetable land-use settingis less susceptible to nitrate contamina-tion than ground water in the other twoland-use settings because nitrate maybe removed by biochemical processes.

The presence of fine-grained sedi-ment textures and evidence of nitratereduction at some sites in the corn,alfalfa, and vegetable land-use settingare a result of its location on the lowestparts of the eastern alluvial fans, nearthe boundary between the alluvial fansand basin, where sediments weredeposited by different sedimentaryprocesses. As a result, sediment tex-ture and chemical conditions in thecorn, alfalfa, and vegetable land-usesetting are more variable than in thealmond and vineyard land-use settings.This high variability makes it difficultto generalize the conclusions from theoverall data set to specific sites.

Nitrate concentrations inground water have increasedin the eastern San JoaquinValley

Analyses of several thousandground-water samples were compiledfrom USGS and USEPA data bases toevaluate the long-term changes in

nitrate concentrations. Data from wellsin the eastern San Joaquin Valley thatwere less than or equal to 200 feetdeep indicate that median nitrate con-centrations increased significantlyfrom the 1950s to the 1960s, and fromthe 1970s to the 1980s. From 1950 to1980, the amount of nitrogen fertilizerapplied in the eastern San Joaquin Valey counties increased from 114 to 745million pounds per year, an increase o554 percent. The number of dairies andother confined-animal feedlots, andhence manure production, also haveincreased greatly during this period.However, estimates indicate that nitrogen fertilizer is the largest source ofnitrate in the eastern San Joaquin Valley (Gronberg and others, in press). Ocourse, this generalization may not bethe case for areas where the sourcemay be attributed to confined-animalfeedlots located close together.

As indicated by a much smaller butbetter controlled data set, nitrateconcentrations increased over less thaa decade. Of the 30 wells in theregional aquifer survey in the easternSan Joaquin Valley that were sampledin 1995, 23 also had been sampledduring 1986–87. The median nitrateconcentration of this subset of 23domestic wells increased from2.4 mg/L during 1986–87 to 4.8 mg/Lin 1995 (Burow and others, inpress, b). The increase in



4,000 FEET0

0 1,000 METERS

6.41977

3.01991

<0.031956

<0.031992

<0.031992

1.31989

2.01970

<0.03NA

<0.03NA

<0.031965

0.86NA

0.31979

0.031961

<0.031940

0.861963

<0.031947

<0.03

1947

2.61986

2.81992

0.461954

0.291954

EXPLANATIONCONCENTRATIONS OF NITRATEESTIMATED

RECHARGE DATE

DBCP CONCENTRATION, IN MICROGRAMS PER LITER

ESTIMATED RECHARGE DATE

depth ofhouseholdwell

1990s

1980s

1970s

1960s

Pre-1960s

Greater than 10 milligrams per liter

3 to 10 milligrams per liter

Less than 3 milligrams per liter

water table

.n

,

ine, atrazine, diuron, and DBCP are the moston pesticides in the eastern San Joaquin, California (atrazine detections includeylatrazine).

SIMAZINE ATRAZINE DIURON DBCPSELECTED PESTICIDE

00

20

40

60

80

VINEYARD LAND USEALMOND LAND USECORN, ALFALFA, AND VEGETABLE LAND USEREGIONAL AQUIFER SURVEY

ells installed along the ground-water flow path in the vineyard land-use setting shownd nitrate concentrations generally are lowest in older water and are high but variable

-

0

25

50

75

100

125

150

175

200

225

250

275DE

PT

H B

ELO

W L

AN

D S

UR

FAC

E, I

N F

EE

T

Monitoring wthat DBCP ain the younge

nitrate concentration islikely attributed toincreased fertilizer usefrom 1950 to 1980.

Analyses of samplesfrom the 20 multilevelmonitoring wells in thevineyard land-use settingindicated that nitrateconcentrations havegenerally increased overthe last four decades. Inaddition to analyses fornitrate and pesticides, theestimated date when theground water sampledfrom these wells was re-charged was determinedby measuring concentra-tions of chlorofluoro-carbons (CFC). CFCconcentrations insamples from the deepestwells indicate that thedeepest ground waterhad entered the aquiferprior to 1960. Nitrateconcentrations in thepre-1960 water are generally less than3 mg/L. In general, ground-water ageincreases with depth below landsurface, whereas nitrate concentrationdecrease with depth. The highestnitrate concentrations occur in shallowground water that was rechargedduring 1977 to 1992. Because typicaldomestic well depths in the vicinity ofthe monitoring well transect are about90 to 130 feet below land surface,these data suggest that nitrateconcentrations could increase indomestic wells in the vineyardland-use setting.

Taken together, these studies offercompelling evidence that nitrate con-centrations in the ground water in theeastern San Joaquin Valley haveincreased over the last four decades;prediction of future change is problematic because of the decrease in theamount of fertilizer application overthe last decade.


Pesticides were detected in69 percent of the ground-water samples collected fromdomestic wells in the easternSan Joaquin Valley

Pesticides were detected in 61of the 88 domestic wells sampledduring 1993–95 (69 percent), butconcentrations of most pesti-cides were low—less than0.1µg/L. Although 25 pesticideswere detected, only 5 pesticideswere detected in more than10 percent of the samples:simazine, 1,2-dibromo-3-chloropropane (DBCP), atrazine,desethylatrazine (atransformation product ofatrazine), and diuron. Thegreatest number of pesticideswere detected in ground-watersamples from wells in thevineyard land-use setting, where17 different pesticides were

SimazcommValleydeseth

1

DE

TE

CT

ION

FR

EQ

UE

NC

Y, I

N P

ER

CE

NT

r water (<, less than).

s


detected in 80 percent of the samplesPesticides were detected least often (i55 percent of samples) in ground-water samples from wells in the corn,alfalfa, and vegetable land-use settingalthough the number of pesticidedetections were not significantlydifferent among the three land-usesettings.

00


e

,

at

e

The number of pesticide detections issimilar during 1986–87 and 1995(red – concentration remained the sameor decreased; blue – concentrationincreased; white – indeterminate; * –estimated. <, less than; µg/L,micrograms per liter)

Pesticide 1986-87concentration

(µg/L)

1995concentration

(µg/L)Atrazine <0.1 0.02

<0.1 0.0560.1 0.007

<0.1 0.002<0.1 0.120.4 0.081

<0.1 0.0030.2 0.009

Simazine <0.1 0.0590.2 0.01

<0.1 0.0020.1 0.095

<0.1 0.0060.1 0.11

<0.1 0.0490.2 0.0090.1 <0.0050.2 0.075

DBCP <3.0 1.11,2-dichlo-ropropane

6.4 0.4

Prometon <0.1 0.008*<0.1 0.004*

Cyanazine <0.1 0.023EDB <0.2 0.55Dicamba 0.01 <0.035

0.01 <0.035Dichlorprop 0.01 <0.032

The occurrence of DBCP andsimazine in the three agricultural land-use settings is generally consistentwith the available information on theuse of these pesticides (Burow and oth-ers, in press, a). In contrast, atrazineand diuron detections were not consis-tent with their reported use, possiblybecause of their application on rights-of-way for weed control.

The number of pesticide detectionswas related to characteristics that dic-tate the relative susceptibility ofground water beneath the three land-use settings. The greatest number ofpesticide detections occurred in thevineyard land-use setting. The numberof pesticide detections per sample wascorrelated with the coarse-grained sed-iment texture and dissolved-oxygenconcentrations. Furthermore, samplesfrom 15 of the 18 (83 percent) wellswith nitrate concentrations exceedingthe USEPA drinking-water standardalso contained at least one pesticide. Inthe vineyard land-use setting, concen-trations of DBCP and nitrate were pos-itively correlated, indicating thatground-water samples with the high-est nitrate concentrations also had thehighest DBCP concentrations.

DBCP concentrationsexceeded the USEPAdrinking-water standard in 20percent of the ground-watersamples collected fromdomestic wells in the easternSan Joaquin Valley

Concentrations of DBCP, a soilfumigant banned since 1977, exceededthe USEPA drinking-water standard of0.2µg/L in 18 of the 88 (or 20 percent)domestic wells sampled during 1993–95. Ten of the DBCP samples thatexceeded the USEPA standards werefrom wells in the vineyard land-usesetting, where DBCP was used to com-bat nematodes. In contrast, DBCP wasnot detected in any of the samplesfrom the wells in the corn, alfalfa, andvegetable land-use setting. The soilfumigant 1,2-dibromoethane (alsocalled EDB or ethylene dibromide)was the only other pesticide detected at

a concentration that exceeded aUSEPA drinking-water standard,although only six of the pesticidesdetected in ground water in the easternSan Joaquin Valley have drinking-water standards. EDB was detected inone ground-water sample.

Pesticide concentrations indomestic wells wereconsistent over time (1986–87to 1995) but were higher inmonitoring wells near thewater table than at greaterdepths

Of the 30 domestic wells sampled aspart of the regional aquifer survey in1995, 19 had been sampled for pesti-cides during 1986–87. Samples fromboth periods were tested for 21pesticides and 37 volatile organiccompounds (VOC), but the laboratorymethods of analyses were different forthe two time periods. An increase from13 pesticide detections during 1986–87 to 23 pesticide detections in 1995can be attributed to the use of ananalytical method that was 10 timesmore sensitive than the method usedduring 1986–87 (Burow and others, inpress, b). If the data are adjusted to thsame level of sensitivity, the number ofpesticide detections is similar for thetwo periods: 10 detections during1986–87 and 7 detections in 1995.Concentrations of pesticides generallywere lower in 1995 than during1986–87. Although the number ofwells resampled is small, and the ageof the sampled ground water has notbeen determined, there is no evidencethat the pesticide concentrations or thenumber of pesticides detected during1986–87 increased in 1995.

Analyses of samples from the 20multilevel monitoring wells in thevineyard land-use setting show thatDBCP concentrations generallydecreased with depth and were highlyvariable near the water table. Pesti-cides were detected most frequentlynear the water table in ground waterthat was recharged after 1980.Simazine was detected in all sixground-water samples from shallow

U.S. Geol

wells (less than 90 feet deep), atrazin(or desethylatrazine) was detected infive of the six shallow wells, andDBCP was detected in four of the sixshallow wells. Although plausibleexplanations exist for the high DBCPconcentrations in young ground watercurrent data are insufficient to confirmthe source of the high DBCPconcentrations. These data suggest thground water from domestic wells inthe vineyard land-use setting wouldlikely continue to contain DBCP,simazine, and atrazine (ordesethylatrazine).


20 Water Quality in the San Joaquin–Tulare Basins, California, 1992–95

WATER-QUALITY CONDITIONS IN A NATIONAL CONTEXT—Stream-Water Quality

Seven major water-quality characteristics were evaluated for stream sites in eachNAWQA Study Unit. Summary scores for each characteristic were computed for allsites that had adequate data. Scores for each site in the San Joaquin–Tulare BasinsStudy Unit were compared with scores for all sites sampled in the 20 NAWQAStudy Units during 1992–95. Results are summarized by percentiles; higherpercentile values generally indicate poorer quality compared with other NAWQAsites. Water-quality conditions at each site also are compared to established criteriafor protection of aquatic life. Applicable criteria are limited to nutrients andpesticides in water and semivolatile organic compounds (SVOC), organochlorinepesticides, and PCBs in sediment. (Methods used to compute rankings and evaluateaquatic-life criteria are described by Gilliom and others, in press.)

FISH COMMUNITY DEGRADATION

High percentages of fish at sites in thefixed-site network were nonnative,omnivores, diseased or deformed, ortolerant of human-caused streamdegradation. Disease or deformityincludes external parasites, tumors, andskeletal deformities. All sites receivedthe poorest score for percentage of non-native species and percentage of fishwith external anomalies. Fish commun-ities at all sites were scored as highlydegraded when compared with fishcommunities at other sites across theNation.

STUDY AREA showing inset

Greater than the 75th percentile(among the highest 25 percentof NAWQA stream sites)

Between the median and the 75th percentile

Between the 25th percentile and the median

Less than the 25th percentile(among the lowest 25 percentof NAWQA stream sites)

EXPLANATION

Ranking of stream quality relative to allNAWQA stream sites — Darker coloredcircles generally indicate poorer quality.Bold outline of circle indicates one or moreaquatic life criteria were exceeded.

STREAM HABITAT DEGRADATION

Physical characteristics of streams canhave substantial effects on waterchemistry and aquatic life. On the basisof stream modification, bank erosion,bank stability, and riparian vegetationdensity, sites in the Study Unit weremoderately to highly degraded whencompared with other sites in the Nation.There are no standards or guidelines thatapply to stream habitat.

Stanisla

usRiver

TuolumneRiver

Merced River

San

River

Salt

MudLos Banos

Slough

Slough

Joaquin

DelPuert

o Creek

Orestimba Creek


Creek

Stanisla

usRiver

TuolumneRiver

Merced River

San

River

Salt

MudLos Banos

Slough

Slough

Joaquin

DelPuert

o Creek

Orestimba Creek


Creek


Stanisla

usRiver

TuolumneRiver

Merced River

San

River

Salt

MudLos Banos

Slough

Slough

Joaquin

DelPuert

o Creek

Orestimba Creek


Creek

Stanisla

usRiver

TuolumneRiver

Merced River

San

River

Salt

MudLos Banos

Slough

Slough

Joaquin

DelPuert

o Creek

Orestimba Creek


Creek

Stanisla

usRiver

TuolumneRiver

Merced River

San

River

Salt

MudLos Banos

Slough

Slough

Joaquin

DelPuert

o Creek

Orestimba Creek


Creek

SEMIVOLATILE ORGANICCOMPOUNDS in bedsediment

Few SVOCs were detectedin the Study Unit. Thosedetected were usuallyfound at low concentra-tions, and values were lowcompared with other sitesin the Nation. Criteria forprotection of aquatic lifewere not exceeded.

CONCLUSIONS

The Study Unit is in poor condition compared with theother 19 Study Units in the categories of fish com-munities, PCBs, and organochlorines in streambedsediment and fish tissue, and pesticides in the water.Several sites exceeded guidelines and criteria, andthe occurrence of nonnative fish species and fishwith external anomalies were especially high in theStudy Unit. Stream habitat and nutrientconcentrations in water were close to the median forthe 20 Study Units. Only the occurrence andconcentrations of SVOCs in sediment were lowrelative to the other Study Units.

NUTRIENTS in water

Nutrient concentrations inthe Study Unit ranged fromvery low to one of thehighest in the Nation. Thehigh concentrations occur atsites that are downstreamfrom agricultural drainageor wastewater-treatmentplant discharge. Ammoniaconcentrations exceededguidelines for fish toxicityat three sites in the StudyUnit.

PESTICIDES in water

Concentrations of dissolvedpesticides in the Study Unitwere among the highest of allNAWQA sites nationwide.For many pesticides, thisStudy Unit had the max-imum concentration of all 20Study Units. All sitesexceeded the aquatic-lifecriteria for at least onepesticide at least 17 percentof the time. However,drinking-water-qualitystandards were not exceeded.

TRACE ELEMENTS in bedsediment

Concentrations of traceelements in bed sedimentgenerally were higher thanconcentrations found inother NAWQA StudyUnits.

ORGANOCHLORINEPESTICIDES and PCBs inbed sediment and biologicaltissue

Concentrations oforganochlorine chemicalsin the Study Unit,particularly DDT com-pounds and toxaphene,were high in bed sedimentand tissues of fish or clams.Levels at some sites wereamong the highest in theNation.

Stanisla

usRiver

TuolumneRiver

Merced River

San

River

Salt

Mud

Los Banos

Slough

Slough

Joaquin

DelPuert

o Creek

Orestimba Creek


Creek

Stanisla

usRiver

TuolumneRiver

Merced River

San

River

Salt

MudLos Banos

Slough

Slough

Joaquin

DelPuert

o Creek

Orestimba Creek


Creek

WATER-QUALITY CONDITIONS IN A NATIONAL CONTEXT—Stream-Water Quality


WATER-QUALITY CONDITIONS IN A NATIONAL CONTEXT—Ground-Water Quality

Five major water-quality characteristics were evaluated for ground-water studies in eachNAWQA Study Unit. Ground-water resources were divided into two categories:(1) drinking-water aquifers, and (2) shallow ground water underlying agricultural orurban areas. Summary scores were computed for each characteristic for all aquifers andshallow ground-water areas that had adequate data. Scores for each aquifer and shallowground-water area in the San Joaquin-Tulare Basins Study Unit were compared withscores for all aquifers and shallow ground-water areas sampled in the 20 NAWQAStudy Units during 1992–95. Results are summarized by percentiles; higher percentilevalues generally indicate poorer quality compared with other NAWQA ground-waterstudies. Water-quality conditions for each drinking-water aquifer also are comparedwith established drinking-water standards and criteria for protection of human health.(Methods used to compute rankings and evaluate standards and criteria are described byGilliom and others, in press.)

NITRATE

Nitrate concentrations in shallowground water from domesticwells in agricultural areas wereamong the highest of allNAWQA Study Units. The waterquality was different in areas withdifferent crops. Drinking-waterstandards were exceeded in 40percent of the wells in the almondarea, and in only 15 percent ofwells in the vineyard area.

EXPLANATIONREGIONAL AQUIFER SURVEY (RAS) (includes all land uses)

Unspecified land use

Almonds land use (ALM)

Vineyards land use (VIN)

Corn, alfalfa, vegetables land use (CAV)

Ranking of ground-water quality relative toall NAWQA ground-water studies — Darkercolored circles generally indicate poorerquality. Bold outline of circle indicates thatone or more standards or criteria wereexceeded.

Greater than the 75th percentile (among the highest 25 percent of NAWQA ground-water studies)

Between the median and the 75th percentile

Between the 25th percentile and the median

Less than the 25th percentile (among the lowest 25 percent of NAWQA ground-water studies)

RAS

ALM

CAV

VIN

RADON

Radon concentrations wererelatively high when comparedwith other NAWQA Study Units.No current water-qualitystandards exist for this element.

RAS

VIN

CAV

ALM

All of these land-use settings represent both shallowground water areas and drinking-water aquifers. Fornational comparison purposes, these land-usesettings were compared with the summary scores ofother drinking-water aquifers.


WATER-QUALITY CONDITIONS IN A NATIONAL CONTEXT—Ground-Water Quality

PESTICIDES

Pesticides were detected in morethan 50 percent of ground-watersamples in the Study Unit. Allaquifer areas sampled had levelsabove the national median forNAWQA studies, but were notamong the highest in the Nation.No drinking-water standards wereexceeded, except for DBCP (seeVOC results below).

VOLATILE ORGANIC COMPOUNDS

VOCs were detected in 27 percentof the wells overall, and the per-cent detection in most of the areaswas greater than the median forall NAWQA Study Units. Thehigh rate of VOC detection andthe exceedance of the drinking-water standard in 40 percent ofthe wells in the vineyard area arelargely the result of the detectionof the banned soil fumigantDBCP.

CONCLUSIONS

Ground-water quality in the San Joaquin–Tulare Basins is generally poor comparedwith the other Study Units. Nitrateconcentrations were higher than thenational median and frequently exceededdrinking-water standards in all of the fourareas sampled. Pesticides were fre-quently detected and the rate of detectionwas above the national median. Nodrinking-water standards were exceeded.The rate of detection for VOCs was highcompared to the other Study Unitsbecause of the frequent detection ofDBCP. No drinking-water standards wereexceeded except for DBCP, and in onesample, EDB.

DISSOLVED SOLIDS

Concentrations of dissolvedsolids in the eastern alluvial fansgenerally were higher than themedian for all NAWQA StudyUnits; however, dissolved solidsin areas where corn, alfalfa, andvegetables are grown were amongthe highest. The dissolved-solidsstandard is for aesthetics—appearance and smell—andthough often exceeded, no healththreat is indicated.

ALM

CAV

VIN

RAS

ALM

CAV

VIN

RAS

RAS

VIN

CAV

ALM

STUDY DESIGN AND DATA COLLECTION

ore

y.

cts

tictes,r-

e-

els

EXPLANATIONLAND USE

UrbanAgricultureRangelandForestTundraOther

STREAMCHEMISTRYSITES

BasicIntensiveSynoptic

20 40 MILES

20 40 KILOMETERS0

0

Sampling sites were selected to represent major, large-scale contrasts in ecoregions, land use, and hydrogeologMost of the data were collected in the predominantly agri-cultural San Joaquin Valley because factors likely to impawater quality are concentrated in this area. This focus waconsistent with the first two topics selected for study at thenational level by the NAWQA Program: pesticides andnutrients.

Studies were designed to provide multiple lines of evi-dence to describe water quality conditions (Gilliom andothers, 1995). To this end, investigations of surface-waterchemistry, contaminants in sediment and in tissues of aquaorganisms, and aquatic ecology took place at the same siif possible. The studies also were designed to provide infomation on water quality over a range of complementarytemporal and geographic scales. The time scale of surfacwater investigations varied from once-a-year, to once-a-month, to several times a day. The geographic scale of thground-water investigations ranged from sampling 30 weldistributed over 2,000 square miles to sampling four wellswithin 200 feet. Each scale of study revealed relationsbetween water quality and causal factors not apparent atlarger or smaller scales.

At all levels of study, relevant ancillary information, suchas land use, soil and aquifer properties, fertilizer-use rate,and locations of dairies, was collected to help explain thechemical and ecological data. Detailed information, such change in streamflow during a winter storm or the timing ouse of a particular pesticide, was also used for both desig

24 Water Quality in the San Joaquin–Tulare Basins, California, 199

Location of steam ecology sites.

20 40 MILES

20 40 KILOMETERS0

0

and interpretation of specialized studies. In general, thequestions addressed by each study component became mfocused during each of the 3 years of intensive datacollection (September 1992 to August 1995).

asfn

Location of stream chemistry sites.

2–95

Location of ground-water chemistry sites.

EXPLANATIONPHYSIOGRAPHY

Eastern alluvial fansWestern alluvial fans

Sierra NevadaCoast Ranges

GROUND-WATERCHEMISTRY SITES

Regional Aquifer SurveyVineyard land useAlmond land useCorn, alfalfa,

land useFlow path

Regional Aquifer SurveyVineyard land useAlmond land useCorn, alfalfa, or vegetable land use

Flow PathStudy Area

STUDY DESIGN AND DATA COLLECTION

r

SUMMARY OF DATA COLLECTION IN THE SAN JOAQUIN-TULARE BASINS STUDY UNIT, 1992–95

Studycomponent

What data were collected and Why Types of sites sampledNumberof sites

Sampling frequencyand period

Stream Chemistry

Basic Fixed Sites(BFS)—gen-eral waterchemistry

Streamflow, nutrients, major chemical constituents, organic car-bon, suspended sediment, water temperature, specific con-ductance, pH, and dissolved oxygen to describeconcentrations and seasonal variations.

Representative of a variety of agri-cultural land uses, and the basinoutflow.

10 Monthly plus storms

Jan. 1993–Dec. 1994

Intensive FixedSites (IFS)—pesticides

In addition to the above constituents, approximately 83 dis-solved pesticides to describe concentrations and seasonalvariations.

Subset of basic sites representingcontrasting physiographicareas, and the basin outflow.

4 twice weekly to monthlyJan. 1993–Dec. 1993

Synopticsites—waterchemistry

Streamflow, pesticides, water temperature, specific conduc-tance, pH, and dissolved oxygen to describe concentrationsand spatial distributions.

Basic sites and others representingagricultural and urban landuses.

23 (lowflow)

Once June 1994

Contaminants inbed sediments

Total PCBs, 32 organochlorine pesticides, 63 semivolatileorganic compounds, and 44 trace elements to determineoccurrence and spatial distribution.

Depositional zones of all basic andintensive sites, plus additionalsynoptic sites.

17 Once Oct. 1992

Contaminants inaquatic biota

Total PCBs, 30 organochlorine pesticides, and 24 trace elementswere analyzed to determine occurrence and spatial distribu-tion. Clams and whole fish for organic contaminants. Clams,fish livers, or crayfish for trace elements.

Same sites as for contaminants inbed sediment where tissuecould be collected.

18 Once Oct.–Nov. 1992

Stream Ecology

Intensive assess-ments

Assess communities of fish, macroinvertebrates, and algae ateach site; and quantitatively describe stream habitat for theseorganisms.

Subset of BFS (9 of 10) plus a sitein Yosemite National Park.

346

3 reaches/site in 19951 reach/year, 1993–95

1 reach in 1993

Synoptic studies Similar to the above, one reach per site, for areal comparison ofhabitat and community composition, nutrient samples col-lected.

Subset of BFS plus others. 32 Once in either 1993 o1994

Ground-Water Chemistry

Regional AquiferSurvey—east-ern alluvial fans

Major chemical constituents, nutrients, 83 pesticides, 60 vola-tile organic compounds, and radon to determine occurrenceof these constituents in this region.

Domestic wells in the eastern allu-vial fans, San Joaquin Valley.

30 Once in 1995

Land-useeffects—corn,alfalfa, and veg-etable rowcrops

Major chemical constituents, nutrients, 83 pesticides, 60 volatileorganic compounds, and radon to describe the effects of agri-cultural land use on shallow ground water, eastern alluvialfans.

Shallow domestic wells;Shallow monitoring wells;>50 percent corn, alfalfa, and veg-

etables grown in rotation withina 0.25-mile radius.

2010

Once in 1995

Land-use effects—almondorchards


Shallow domestic wells;Shallow monitoring wells;>50 percent almond orchards

within 0.25 mile radius.

2010

Once in 1994

Land-useeffects—vine-yards


Shallow domestic wells;Shallow monitoring wells;>50 percent vineyards within

0.25-mile radius.

2010

Once in 1993

Chemical andphysical pro-cesses alongground-waterflow paths

Major chemical constituents, nutrients, 83 pesticides, 60 volatileorganic compounds, radon, transformation products of 1,2-dibromo-3-chloropropane, and constituents used to estimatedate when ground water was recharged.

20 wells at 6 sites along anapproximate ground-water flowpath beneath vineyard land usein eastern alluvial fan, SanJoaquin Valley.

20 Once in 1994Once in 1995

Special Studies

Dissolved pesti-cide transport inwinter storms

Dissolved pesticides and streamflow were measured along witha dye traveltime study to assess the variability of concentra-tions during storms and the impact on the basin outflow. Spe-cific agricultural and urban areas were assessed.

2 IFS, 3 western valley sites, andbasin outflow.

5 eastern valley sites, 3 agricul-tural drains, and basin outflow.

5 urban sites, 3 agricultural drains,7 eastern valley sites, and basinoutflow.

6

9

16

Jan.–Feb. 1993

Jan.–Feb. 1994

Feb.–Mar. 1995

Transport of sedi-ment-boundpesticides

Sediment-bound pesticides, dissolved pesticide, suspended sed-iment, and streamflow to compare winter and irrigation sea-son transport.

2 Coast Ranges sites, 2 agricul-tural drains, 7 western valleysites, and basin outflow.

812

June 1994Jan. 1995

Aquatic ecology–-Merced River,YosemiteNational Park

Assessment of algal community, chlorophyll-a and ash-free drymass, and supporting data on nutrients, major constituents,trace elements, and organic contaminants in bed sedimentand tissue.

Synoptic sites. 8 Sept. 1995


SUMMARY OF COMPOUND DETECTIONS AND CONCENTRATIONS—Analysis And Detection of Pesticides, VolatileOrganic Compounds, and Nutrients in Ground and Surface Waters of the San Joaquin–Tulare Basins Study Unit

Herbicide(Trade or common

Rateof

Concentration, inµg/L

The following tables summarize data collected for NAWQA studies from 1992–95 by showing results for the San Joaquin–Tulare Basins Study Unit compared to the NAWQA national range for each compound detected. The data were collected at a widevariety of places and times. In order to represent the wide concentration ranges observed among Study Units, logarithmic scales areused to emphasize the general magnitude of concentrations (such as 10, 100, or 1000), rather than the precise number. The completedataset used to construct these tables is available upon request.

Concentrations of herbicides, insecticides, volatile organic compounds, and nutrients detected in ground and surface waters of the SanJoaquin–Tulare Basins Study Unit. [mg/L, milligrams per liter; µg/L, micrograms per liter; pCi/L, picocuries per liter; %, percent; <, lessthan; - -, not measured; trade names may vary]

EXPLANATION

Range of surface-water detections in all 20 Study Units

Detection in the San Joaquin–Tulare Basins Study Unit

Range of ground-water detections in all 20 Study Units

Drinking water standard or guidelinea

Freshwater-chronic criterion for the protection of aquatic lifea

Herbicide(Trade or common

ame)

Rateofdetec-

b


0.001 0.01 0.1 1 10 100 1,000
name) detec-
tion b0.001 0.01 0.1 1 10 100 1,000 n

Alachlor (Lasso) 9%0%

2,6-Diethylaniline(Alachlor metabolite)

<1%0%

Atrazine (AAtrex,Gesaprim)

27%7%

Deethylatrazinec

(Atrazine metabolite)

<1%7%

Benfluralin (Balan,Benefin, Bonalan)

2%0%

Bromacil (Hyvar X,Urox B, Bromax)

8%0%

Butylate (Sutan,Genate Plus, butilate)

4%<1%

Cyanazine (Bladex,Fortrol)

34%1%

2,4-D (2,4-PA) 12%0%

2,4-DB (Butyrac,Embutox)

1%0%

DCPA (Dacthal, chlo-rthal-dimethyl)

22%<1%

Dichlorprop (2,4-DP,Seritox 50, Kildip)

3%0%

Dinoseb (DNBP, DN289, Premerge)

0%2%

Diuron (Karmex,Direx, DCMU)

54%12%

EPTC (Eptam) 43%1%

26 Water Quality in the San Joaquin–Tulare Basins, 1992–95

tion

Ethalfluralin (Son-alan, Sonalen)

13%<1%

Linuron (Lorox,Linex, Sarclex)

<1%0%

MCPA (Agritox,Agroxone)

3%0%

Metolachlor (Dual,Pennant)

44%1%

Metribuzin (Lexone,Sencor)

3%0%

Molinate (Ordram) 9%0%

Napropamide(Devrinol)

24%1%

Norflurazon (Evital,Solicam, Telok)

8%2%

Oryzalin (Surflan,Dirimal, Ryzelan)

8%0%

Pebulate (Tillam) 11%0%

Pendimethalin(Prowl, Stomp)

4%0%

Prometon (Gesa-gram, prometone)

3%1%

Pronamide (Kerb,propyzamid)

3%0%

Propachlor (Ramrod,propachlore)

<1%0%

Propanil (Stampede,Surcopur)

<1%0%


Insecticide(Trade or commonname)

Rateofdetec-

b


0.001 0.01 0.1 1 10 100 1,000

Herbicide(Trade or commonname)

Rateofdetec-

tion b


0.001 0.01 0.1 1 10 100 1,000

Simazine (Aquazine,Princep, GEsatop)

95%34%

Tebuthiuron (Spike,Perflan)

2%0%

Terbacilc (Sinbar) <1%1%

Thiobencarb (Bolero,Saturn, benthiocarb)

2%0%

Triallate (Far-Go) <1%<1%

Triclopyr (Garlon,Grazon, Crossbow)

1%0%

Trifluralin (Treflan,Trinin, Elancolan)

30%<1%

Insecticide(Trade or commonname)

Rateofdetec-

tion b


Aldicarbc (Temik) 1%0%

Azinphos-methylc

(Guthion, Gusathion)

12%0%

Carbarylc (Sevin,Savit)

25%1%

Carbofuranc

(Furadan, Curaterr)

5%0%

Chlorpyrifos (Durs-ban, Lorsban)

52%<1%

p,p’-DDE (p,p’-DDTmetabolite)

14%<1%

Diazinon 71%<1%

Dieldrin (Panoram D-31, Octalox)

10%1%

Disulfotonc (Disys-ton, Dithiosystox)

<1%0%

Ethoprop (Mocap,Prophos)

<1%<1%

Fonofos (Dyfonate) 10%0%

alpha-HCH (alpha-BHC, alpha-lindane)

4%0%

gamma-HCH 4%0%

Malathion (maldison,malathon, Cythion)

8%1%

0.001 0.01 0.1 1 10 100 1,000

Methomyl (Lannate,Nudrin)

5%0%

Methyl parathion(Penncap-M)

<1%0%

cis-Permethrinc

(Ambush, Pounce)

<1%0%

Propargite (Comite,Omite, BPPS)

20%0%

Terbufos (Counter) <1%0%

Volatile organiccompound(Trade or commonname)

Rateofdetec-

tion b


1,2,3-Trichloropro-pane (Allyl trichloride)

--7%

1,2,4-Trimethylben-zene (Pseudocumene)

--2%

1,2-Dibromo-3-chlo-

ropropaned (DBCP)

--21%

1,2-Dibromoethaned

(EDB)

--1%

1,2-Dichloropropane(Propylene dichloride)

--6%

Dichloromethane(Methylene chloride)

--1%

Methylbenzene (Tolu-ene)

--2%

total Trihalomethanes --2%

Trichloroethene(TCE)

--2%

Trichlorofluoromethane(CFC 11)

--2%

Volatile organiccompound(Trade or commonname)

Rateofdetec-

tion b


Tetrachloroethene(Perchloroethene)

--3%

0.01 0.1 1 10 100 1,000

0.01 0.1 1 10 100 1,000 10,000 100,000

tion



Other Rateofdetec-

b

Concentration, in pCi/L

1 10 100 1,000 10,000 100,000

Nutrient(Trade or commonname)

Rateofdetec-

Concentration, in mg/L

0.01 0.1 1 10 100 1,000 10,000 100,000

Dissolved ammonia 94%56%

Dissolved ammoniaplus organic nitrogenas nitrogen

77%6%

Dissolved phospho-rus as phosphorus

96%85%

Dissolved nitrite plusnitrate

95%97%

R

tion b


Herbicides, insecticides, volatile organic compounds, and nutrients Basins Study Unit.

adon 222 --100%

tion

not detected in ground and surface waters of the San Joaquin–Tulare

Herbicides

2,4,5-T

2,4,5-TP (Silvex, Feno-prop)

Acetochlor (Harness Plus,Surpass)

Acifluorfen (Blazer, Tackle2S)

Bentazon (Basagran, Ben-tazone, Bendioxide)

Bromoxynil (Buctril, Bro-minal)

Chloramben (Amiben,Amilon-WP, Vegiben)

Clopyralid (Stinger, Lon-trel, Reclaim, Transline)

Dacthal mono-acid(Dacthal metabolite)

Dicamba (Banvel, Dianat,Scotts Proturf)

Fenuron (Fenulon, Feni-dim)

Fluometuron (Flo-Met,Cotoran, Cottonex, Metu-ron)

MCPB (Thistrol)

Neburon (Neburea, Neb-uryl, Noruben)

Picloram (Grazon, Tordon)

Propham (Tuberite)

Insecticides

3-Hydroxycarbofuran(Carbofuran metabolite)

Aldicarb sulfone (Standak,aldoxycarb, aldicarb metab-olite)

Aldicarb sulfoxide (Aldi-carb metabolite)

Methiocarb (Slug-Geta,Grandslam, Mesurol)

Oxamyl (Vydate L, Pratt)

Parathion (Roethyl-P, Alk-ron, Panthion, Phoskil)

Phorate (Thimet, Granu-tox, Geomet, Rampart)

Propoxur (Baygon, Blat-tanex, Unden, Proprotox)

Volatile organiccompounds

1,1,1,2-Tetrachloroethane(1,1,1,2-TeCA)

1,1,1-Trichloroethane(Methylchloroform)

1,1,2,2-Tetrachloroethane

1,1,2-Trichloro-1,2,2-triflu-oroethane (Freon 113, CFC113)

1,1,2-Trichloroethane(Vinyl trichloride)

1,1-Dichloroethane (Eth-ylidene dichloride)

1,1-Dichloroethene(Vinylidene chloride)

1,1-Dichloropropene

1,2,3-Trichlorobenzene(1,2,3-TCB)

1,2,4-Trichlorobenzene

1,2-Dichlorobenzene(o-Dichlorobenzene,1,2-DCB)

1,2-Dichloroethane (Ethyl-ene dichloride)

1,3,5-Trimethylbenzene(Mesitylene)

1,3-Dichlorobenzene(m-Dichlorobenzene)

1,3-Dichloropropane(Trimethylene dichloride)

1,4-Dichlorobenzene(p-Dichlorobenzene,1,4-DCB)

1-Chloro-2-methylbenzene(o-Chlorotoluene)

1-Chloro-4-methylbenzene(p-Chlorotoluene)

2,2-Dichloropropane

Benzene

Bromobenzene(Phenyl bromide)

Bromochloromethane(Methylene chlorobromide)

Bromomethane(Methyl bromide)

Chlorobenzene(Monochlorobenzene)

Chloroethane(Ethyl chloride)

Chloroethene(Vinyl chloride)

Chloromethane(Methyl chloride)

Dibromomethane(Methylene dibromide)

Dichlorodifluoromethane(CFC 12, Freon 12)

Dimethylbenzenes(Xylenes (total))

Ethenylbenzene (Styrene)

Ethylbenzene(Phenylethane)

Hexachlorobutadiene

Isopropylbenzene(Cumene)

Methyl tert-butyl ethere

(MTBE)

Naphthalene

Tetrachloromethane(Carbon tetrachloride)

cis-1,2-Dichloroethene((Z)-1,2-Dichloroethene)

cis-1,3-Dichloropropene((Z)-1,3-Dichloropropene)

n-Butylbenzene(1-Phenylbutane)

n-Propylbenzene(Isocumene)

p-Isopropyltoluene(p-Cymene)

sec-Butylbenzene

tert-Butylbenzene

trans-1,2-Dichloroethene((E)-1,2-Dichlorothene)

trans-1,3-Dichloropropene((E)-1,3-Dichloropropene)

Nutrients

No nondetects


Concentrations of semivolatile organic compounds, organochlorine compounds, and trace elements detected in fish and clam tissue andbed sediment of the San Joaquin–Tulare Basins Study Unit. [µg/g, micrograms per gram, in dry weight; µg/kg, micrograms per kilogram,in dry weight for semivolatile organic compounds and organochlorine compounds in bed sediment, and in wet weight for organochlorinecompounds in fish and clam tissue; %, percent; <, less than; - -, not measured; trade names may vary]

emivolatile organicompound

Rate ofdetec-

tion b

Concentration, inµg/kg

10.1 10 100 1,000 10,000 100,000

EXPLANATION

Range of detections in fish and clam tissue in all 20 Study Units

Detection in bed sediment or fish tissue in the San Joaquin–Tulare Basins Study Unit

Range of detections in bed sediment in all 20 Study Units

Guideline for the protection of aquatic lifef

Detection in clam tissue in the San Joaquin–Tulare Basins Study Unit

1-Methylphenan-threne

--6%

1-Methylpyrene --6%

2,6-Dimethylnaphtha-lene

--78%

2,6-Dinitrotoluene --6%

2-Methylanthracene --6%

4,5-Methyle-nephenanthrene

--11%

9H-Carbazole --6%

9H-Fluorene --6%

Acridine --6%

Anthracene --17%

Anthraquinone --6%

Benz[a ]anthracene --28%

Benzo[a ]pyrene --17%

Benzo[b ]fluoran-thene

--33%

Benzo[k ]fluoran-thene

--33%

Butylbenzylphthalate --28%

Chrysene --33%

Di- n -butylphthalate --78%

Semivolatile organiccompound

Rate ofdetec-

tion b


10.1 10 100 1,000 10,000 100,000

Sc

D

Da

D

F

Ip

P

P

P

bh

p

Oc(

t

Dr

p

t

D3

i- n -octylphthalate --6%

ibenz[a,h ]nthracene

--6%

iethylphthalate --17%

luoranthene --35%

ndeno[1,2,3-cd ]yrene

--11%

henanthrene --33%

henol --56%

yrene --35%

is(2-Ethyl-exyl)phthalate

--94%

-Cresol --28%

rganochlorineompoundTrade name)

Rateofdetec-

tion b


otal-Chlordane 0%6%

CPA (dacthal, chlo-thal-dimethyl)

28%6%

,p’-DDE 89%72%

otal-DDT 89%72%

ieldrin (Panoram D-1, Octalox)

17%17%

0.01 0.1 1 10 100 1,000 10,000 100,000



Organochlorinecompound(Trade name)

Rateofdetec-

tion b


0.01 0.1 1 10 100 1,000 10,000 100,000

Trace element Rateofdetec-

tion b

Concentration, inµg/g

0.01 0.1 1 10 100 1,000 10,000

PCB, total 11%0%

cis-Permethrin(Ambush, Pounce)

--6%

trans-Permethrin(Ambush, Pounce)

--6%

Toxaphene (cam-phechlor)

11%6%

A

C

C

C

L


rsenic 94%100%

admium 62%56%

hromium 94%100%

opper 100%100%

ead 38%100%

Mercury 69%100%

Nickel 88%100%

Selenium 75%100%

Zinc 100%100%


Semivolatile organic compounds, organochlorine compounds, and trace elements not detected in fish and clam tissue and bed sedimentof the San Joaquin–Tulare Basins Study Unit.

Semivolatile organiccompounds

1,2,4-Trichlorobenzene

1,2-Dichlorobenzene (o-Dichlorobenzene, 1,2-DCB)

1,2-Dimethylnaphthalene

1,3-Dichlorobenzene (m-Dichlorobenzene)

1,4-Dichlorobenzene (p-Dichlorobenzene, 1,4-DCB)

1,6-Dimethylnaphthalene

1-Methyl-9H-fluorene

2,2-Biquinoline

2,3,6-Trimethylnaphtha-lene

2,4-Dinitrotoluene

2-Chloronaphthalene

2-Chlorophenol

2-Ethylnaphthalene

3,5-Dimethylphenol

4-Bromophenyl-phe-nylether

4-Chloro-3-methylphenol

4-Chlorophenyl-phe-nylether

Acenaphthene

Acenaphthylene

Azobenzene

Benzo [c] cinnoline

Benzo [g,h,i] perylene

C8-Alkylphenol

Dibenzothiophene

Dimethylphthalate

Isophorone

Isoquinoline

N-Nitrosodi-n-propylamine

N-Nitrosodiphenylamine

Naphthalene

Nitrobenzene

Pentachloronitrobenzene

Phenanthridine

Quinoline

bis (2-Chloroethoxy)meth-ane

a Selected water-quality standards and guidelines (G

b Rates of detection are based on the number of aninsecticides were computed by only counting decompounds, which had widely varying detectionthan 0.01µg/L, or the detection rate rounds to lesslimits for most compounds were similar to the lowsummarized in (Gilliom and others, in press).

c Detections of these compounds are reliable, but coas estimated values (Zaugg and others, 1995).

d In the San Joaquin–Tulare Basins Study Unit, 1521,2-dibromoethane (EDB) at lower detection limidetected in one sample.

e The guideline for methyltert-butyl ether is between 2be 20µg/L (Gilliom and others, in press).

f Selected sediment-quality guidelines (Gilliom and o

(These tables were de

Organochlorinecompounds

Aldrin (HHDN, Octalene)

Chloroneb (chloronebe,Demosan, Soil Fungicide1823)

Endosulfan I (alpha-Endosulfan, Thiodan,Cyclodan, Beosit, Malix,Thimul, Thifor)

Endrin (Endrine)

Heptachlor epoxide (Hep-tachlor metabolite)

Heptachlor (Heptachlore,Velsicol 104)

Hexachlorobenzene (HCB)

Isodrin (Isodrine, Com-pound 711)

Mirex (Dechlorane)

Pentachloroanisole (PCA,pentachlorophenol metabo-lite)

alpha-HCH (alpha-BHC,alpha-lindane,alpha-hexachlorocyclohexane,alpha-benzene hexachlo-ride)

illiom and others, in press)

alyses and detections in thetections equal to or greater limits. For herbicides and inthan one percent. For otherer end of the national range

ncentrations are determine

ground-water samples werets (0.03 and 0.04µg/L, respective

0 and 40µg/L; if the tentative ca

thers, in press).

signed and built by Sarah R

beta-HCH (beta-BHC,beta-hexachlorocyclohex-ane,alpha-benzenehexachloride)

delta-HCH (delta-BHC,delta-hexachlorocyclohex-ane,delta-benzenehexachloride)

gamma-HCH (Lindane,gamma-BHC, Gammex-ane, Gexane, Soprocide,gamma-hexachlorocyclo-hexane,gamma-benzenehexachloride,gamma-ben-zene)

o,p’-Methoxychlor

p,p’-Methoxychlor (Mar-late, methoxychlore)

U.S. Geological Survey

.

Study Unit, not on national dthan 0.01µg/L in order to facilitate eqsecticides, a detection rate ocompound groups, all detects shown. Method detection li

d with greater uncertainty tha

analyzed for 1,2-dibromo-3ly). DBCP was detected in 5

ncer classification C is accep

yker, Jonathan Scott, and Ala

Trace elements

No nondetects

Circular 1159 31

ata. Rates of detection for herbicides andual comparisons amongf “<1%” means that all detections are lessions were counted and minimum detectionmits for all compounds in these tables are

n for the other compounds and are reported

-chloropropane (DBCP) and0 of these samples and EDB was

ted, the lifetime health advisory will

n Haggland.)

REFERENCES

-

,

Brown, R.L., 1975, The occurrenceand removal of nitrogen insubsurface agricultural drainagefrom the San Joaquin Valley,California: Water Research, v. 9,no. 5/6, p. 529–546.

Brown, L.R., 1997, Concentrations ofchlorinated organic compounds inbiota and bed sediment in streamsof the San Joaquin Valley,California: Archives ofEnvironmental Contaminationand Toxicology, v. 33, no. 4, p.357–368.

Brown, L.R., Kratzer, C.R., andDubrovsky, N.M., in press,Integrating chemical, waterquality, habitat and fishassemblage data from the SanJoaquin River drainage,California,in Smith, C.S., andScow, K., eds., IntegratedAssessment of Ecosystem Health:Ann Arbor, Mich., Ann ArborPress.

Burow, K.R., Shelton, J.L., andDubrovsky, N.M., in press, a,Occurrence of nitrate and pesti-cides in ground water beneaththree agricultural land-usesettings in the eastern SanJoaquin Valley, California,1993–1995: U.S. GeologicalSurvey Water ResourcesInvestigations Report 97-4284.

Burow, K.R., Stork, S.V., andDubrovsky, N.M., in press, b,Nitrate and pesticides in groundwater in the eastern San JoaquinValley, California: Occurrenceand trends: U.S. GeologicalSurvey Water ResourcesInvestigations Report 98-4040.

California Department of PesticideRegulation, [1994], Pesticides usedata for 1993. (Digital data forreview at the CaliforniaDepartment of PesticideRegulation, Sacramento, Calif.)

California Department of WaterResources, 1991, Management ofthe California State WaterProject: California Department of

Water Resources Bulletin 132-91,370 p.

———1995, Compilation of federaland state drinking water standardsand criteria: [Sacramento, Calif.],Division of Local Assistance,Quality Assurance TechnicalDocument series, no. 3, 56 p.

Colborn, Theo, and Clement, Coralie,(eds.), 1992, Chemically-inducedalterations in sexual andfunctional development—Thewildlife/human connection:Princeton, N.J., PrincetonScientific Publishing, Advancesin Modern EnvironmentalToxicology series, v. 21, 403 p.

Domagalski, J.L., Dubrovsky, N.M.,and Kratzer, C.R., 1997,Pesticides in the San JoaquinRiver, California—Inputs fromdormant sprayed orchards:Journal of Environmental Quality,v. 26, no. 2, p. 454–465.

Gilliom, R.J., Alley, W.M., and Gurtz,M.E., 1995, Design of theNational Water-QualityAssessment Program—Occurrence and distribution ofwater-quality conditions: U.S.Geological Survey Circular 1112,33 p.

Gilliom, R.J., Mueller, D.K., andNowell, L.H., in press, Methodsfor comparing water qualityconditions among NationalWater-Quality Assessment StudyUnits, 1992-1995: U.S.Geological Survey Open-FileReport 97-589.

Gronberg, J.M., Dubrovsky, N.M.,Kratzer, C.R., Domagalski, J.L.,Brown, L.R., and Burow, K.R., inpress, Environmental setting ofthe San Joaquin-Tulare Basins,California: U.S. GeologicalSurvey Water-ResourcesInvestigations Report 97-4205.

Hughes, R.M., and Gammon, J.R.,1987, Longitudinal changes infish assemblages and waterquality in the Willamette River,

Oregon: Transactions of theAmerican Fisheries Society,v. 116, p. 196-209.

Karr, J.R., 1991, Biologicalintegrity—A long neglectedaspect of water resource management: Ecological Applications,v. 1, p. 66–84.

Kratzer, C.R., 1997, Transport ofdiazinon in the San Joaquin RiverBasin, California: U.S.Geological Survey Open-FileReport 97-411, 22 p.

———1998, Transport of sediment-bound organochlorine pesticidesto the San Joaquin River,California: U.S. GeologicalSurvey Open-File Report 97-655,30 p.

Kratzer, C.R., in press, Pesticides instorm runoff from agriculturaland urban areas in the TuolumneRiver Basin in the vicinity ofModesto, California: U.S.Geological Survey Water-Resources Investigations Report98-4017.

Kratzer, C.R., and Biagtan, R.N.,1997, Determination of travel-times in the lower San JoaquinRiver Basin, California, fromdye-tracer studies during 1994–1995: U.S. Geological SurveyWater-Resources InvestigationsReport 97-4018, 20 p.

Kratzer, C.R., and Shelton, J.L., inpress, Water-quality assessmentof the San Joaquin-Tulare BasinsCalifornia: Analysis of availabledata on nutrients and suspendedsediment in surface water, 1972–1990: U.S. Geological SurveyProfessional Paper 1587, 94 p.

Kuivila, K.M., and Foe, C.G., 1995,Concentrations, transport andbiological effects of dormantspray pesticides in the SanFrancisco Estuary, California:Environmental Toxicology andChemistry, v. 14, no. 7,p. 1141–1150.


REFERENCES

MacCoy, D.E., Crepeau, K.L., andKuivila, K.M., 1995, Dissolvedpesticide data for the San JoaquinRiver at Vernalis and theSacramento River at Sacramento,California, 1991–94: U.S.Geological Survey Open-FileReport 95-110, 27 p.

Madison, R.J., and Brunett, J.O., 1985,Overview of the occurrence ofnitrate in ground water in theUnited States,in U.S. GeologicalSurvey, National Water Summary1984—Hydrologic events,selected water-quality trends, andground-water resources: U.S.Geological Survey Water-SupplyPaper 2275, p. 93–105.

Meador, M.R., Cuffney, T.F., andGurtz, M.E., 1993a, Methods forsampling fish communities as partof the National Water-QualityAssessment Program: U.S.Geological Survey Open-FileReport 93-104, 40 p.

Meador, M.R., Hupp, C.R., Cuffney,T.F., and Gurtz, M.E., 1993b,Methods for assessing streamhabitat as part of the NationalWater-Quality AssessmentProgram: U.S. Geological SurveyOpen-File Report 93-408, 48 p.

Mueller, D.K., and Helsel, D.R., 1996,Nutrients in the Nation’swaters—Too much of a goodthing?: U.S. Geological SurveyCircular 1136, 24 p.

Mueller, D.K., Hamilton, P.A., Helsel,D.R., Hitt, K.J., and Ruddy, B.C.,1995, Nutrients in ground waterand surface water of the UnitedStates: An analysis of datathrough 1992: U.S. GeologicalSurvey Water-ResourcesInvestigations Report 95-4031,74 p.

National Academy of Sciences andNational Academy ofEngineering, 1973 [1974], Waterquality criteria, 1972: U.S.Environmental ProtectionAgency, EPA R3-73-033, 594 p.

Panshin, S.Y., Dubrovsky, N.M.,Gronberg, J.M., and Domagalski,J.L., in press, Occurrence anddistribution of dissolvedpesticides in the lower SanJoaquin River Basin, California:U.S. Geological Survey Water-Resources Investigations Report98-4032.

San Joaquin Valley Drainage Program1990, A management plan foragricultural subsurface drainageand related problems on thewestside San Joaquin Valley:

U.S. Ge

,

Final report of the San JoaquinValley Drainage Program:[Sacramento, Calif.], San JoaquinValley Drainage Program, 183 p.

U.S. Bureau of Reclamation, 1990,Report of operations: U.S. Bureauof Reclamation, Mid-PacifricRegion, Central ValleyOperations Coordinating Office,42 p.

U.S. Environmental ProtectionAgency, 1986, Quality criteria forwater 1986 (“Gold Book”): U.S.Environmental ProtectionAgency, Office of WaterRegulations and Standards, EPA440/5-85-001.

Zaugg, S.D., Sandstrom, M.W., SmithS.G., and Fehlberg, K.M., 1995,Methods of analysis by the U.S.Geological Survey NationalWater Quality Laboratory—Determination of pesticides inwater by C-18 solid-phaseextraction and capillary-columngas chromatography/massspectrometry with selected-ionmonitoring: U.S. GeologicalSurvey Open-File Report 95-181,49 p.

ological Survey Circular 1159 33

GLOSSARY

The terms in this glossary were compiled from numerous sources. Some definitions have been modifiedand may not be the only valid ones for these terms.

Algae—chlorophyll-bearing non-vascular, primarily aquatic species thathave no true roots, stems, or leaves;most algae are microscopic, but somespecies can be as large as vascularplants.

Alluvial aquifer— A water-bearingdeposit of unconsolidated material(sand and gravel) left behind by a riveror other flowing water.

Alluvium— Deposits of clay, silt,sand, gravel or other particulate rockmaterial left by a river in a streambed,on a flood plain, delta, or at the baseof a mountain.

Ammonia—A compound of nitro-genand hydrogen (NH3) that is a commonbyproduct of animal waste. Ammoniareadily converts to nitrate in soils andstreams.

Anomalies—As related to fish,externally visible skin or subcu-taneous disorders, includingdeformities, eroded fins, lesions, andtumors.

Aquatic life criteria— Water-qualityguidelines for protection of aquaticlife. Often refers to U.S.Environmental Protection Agencywater-quality criteria for protec-tion ofaquatic organisms.See Water-qualityguidelines, Water-quality criteria, andFreshwater chronic criteria.

Aquifer— A water-bearing layer ofsoil, sand, gravel, or rock that willyield usable quantities of water to awell.

Background concentration—Aconcentration of a substance in aparticular environment that isindicative of minimal influence byhuman (anthropogenic) sources.

Base flow—Sustained, low flow in astream; ground-water discharge is thesource of base flow in most places.

Basic Fixed Sites—Sites on streamsat which streamflow is measured andsamples are col-lected for temperature,salinity, suspended sediment, majorions and metals, nutrients, and organiccarbon to assess the broad-scalespatial and temporal character andtransport of inorganic constituents ofstream water in relation to hydrologicconditions and environmental settings.

Basin—See Drainage basin.

Bed sediment—The material thattemporarily is stationary in the bottomof a stream or other watercourse.

Bed sediment and tissuestudies—Assessment of concentra-tions and distributions of traceelements and hydrophobic organiccontaminants in streambed sedi-mentand tissues of aquatic organ-isms toidentify potential sources and to assessspatial distribution.

Benthic invertebrates—Insects,mollusks, crustaceans, worms, andother organisms without a back-bonethat live in, on, or near the bottom oflakes, streams, or oceans.

Biota—Living organisms.

Chlordane—Octachloro-4,7-methanotetrahydroindane. Anorganochlorine insecticide no longerregistered for use in the United States.Technical chlordane is a mixture inwhich the primary components arecis-andtrans-chlordane,cis- andtrans-nonachlor, and heptachlor.

Chlorofluorocarbons—A class ofvolatile compounds consisting ofcarbon, chlorine, and fluorine.Commonly called freons, which havebeen used in refrigerationmechanisms, as blowing agents in thefabrication of flexible and rigid foams,and, until several years ago, aspropellants in spray cans.

Community—In ecology, the speciesthat interact in a common area.

Concentration—The amount or massof a substance present in a givenvolume or mass of sample. Usuallyexpressed as micrograms per liter(water sample) or micrograms perkilogram (sediment or tissue sample).

Confluence—The flowing together oftwo or more streams; the place wherea tributary joins the main stream.

Contamination—Degradation ofwater quality compared to original ornatural conditions due to humanactivity.

Criterion— A standard rule or test onwhich a judgment or decision can bebased.

Cubic foot per second—(ft3/s, or cfs)is the rate of water dischargerepresenting a volume of a 1 cubicfoot passing a given point during 1second, equivalent to approxi-mately7.48 gallons per second or 448.8gallons per minute or 0.02832 cubicmeter per second.

Degradation products—Com-poundsresulting from trans-formation of anorganic substance through chemical,photochemical, and(or) biochemicalreactions.


GLOSSARY

h

s

r,

Denitrification— A process by whichoxidized forms of nitrogen such asnitrate (NO3

-) are reduced to formnitrites, nitrogen oxides, ammonia, orfree nitrogen: com-monly broughtabout by the action of denitrifyingbacteria and usually resulting in theescape of nitrogen to the air.

Detection limit—The concentra-tionbelow which a particular analyticalmethod cannot deter-mine, with a highdegree of certainty, a concentration.

DDT—dichloro-diphenyl-trichloro-ethane. An organochlorine insect-icideno longer registered for use in theUnited States.

Dieldrin— An organochlorineinsecticide no longer registered for usein the United States. Also adegradation product of the insecticidealdrin.

Discharge—Rate of fluid flowpassing a given point at a givenmoment in time, expressed as volumeper unit of time.

Dissolved solids—Amount ofminerals, such as salt, that aredissolved in water; amount ofdissolved solids is an indicator ofsalinity or hardness.

Drainage basin—The portion of thesurface of the Earth that con-tributeswater to a stream through overlandrunoff, including tributaries andimpoundments.

Drinking-water standard orguideline—A threshold concen-tration in a public drinking-watersupply, designed to protect humanhealth. As defined here, standards areU.S. Environmental ProtectionAgency regulations that specify themaximum contamination levels forpublic water systems required to

protect the public welfare; guide-lineshave no regulatory status and areissued in an advisory capacity.

Ecological studies—Studies ofbiological communities and habitatcharacteristics to evaluate the effectsof physical and chemicalcharacteristics of water and hydro-logic conditions on aquatic biota andto determine how biological andhabitat characteristics differ amongenvironmental settings in NAWQAStudy Units.

Ecoregion—An area of similarclimate, landform, soil, potentialnatural vegetation, hydrology, or otherecologically relevant variables.

Ecosystem—The interacting popu-lations of plants, animals, andmicroorganisms occupying an area,plus their physical environment.

Effluent—Outflow from a partic-ularsource, such as a stream that flowsfrom a lake or liquid waste that flowsfrom a factory or sewage-treatmentplant.

Environmental setting—Land areacharacterized by a unique combi-nation of natural and human-relatedfactors, such as row-crop cultivationor glacial-till soils.

Ephemeral stream—A stream or partof a stream that flows only in directresponse to precipitation or snowmelt.Its channel is above the water table atall times.

Erosion—The process wherebymaterials of the Earth's crust areloosened, dissolved, or worn away andsimultaneously moved from one placeto another.

Eutrophication—The process bywhich water becomes enriched withplant nutrients, most com-monlyphosphorus and nitrogen.

Fertilizer— Any of a large number ofnatural or synthetic materials,including manure and nitrogen,phosphorus, and potassium com-pounds, spread on or worked into soilto increase its fertility.

Fish community—See Community.

Flow path—An underground routefor ground-water movement,extending from a recharge (intake)zone to a discharge (output) zone sucas a shallow stream.

Freshwater chronic criteria—Thehighest concentration of a contami-nant that freshwater aquatic organismcan be exposed to for an extendedperiod of time (4 days) withoutadverse effects.See Water-qualitycriteria.

Fumigant—A substance or mix-tureof substances that produce gas, vapofume, or smoke intended to destroyinsects, bacteria, or rodents.

Ground water—In general, any waterthat exists beneath the land surface,but more commonly applied to waterin fully saturated soils and geologicformations.

Habitat—The part of the physicalenvironment where plants and animalslive.

Herbicide—A chemical or otheragent applied for the purpose ofkilling undesirable plants.See alsoPesticide.

Hydrograph—Graph showingvariation of water elevation, velo-city,streamflow, or other property of waterwith respect to time.


GLOSSARY

s

.

Insecticide—A substance or mix-tureof substances intended to destroy orrepel insects.

Intensive Fixed Sites—Basic FixedSites with increased sampling fre-quency during selected seasonalperiods and analysis of dissolvedpesticides for 1 year. Most NAWQAStudy Units have one to two integratorIntensive Fixed Sites and one to fourindicator Intensive Fixed Sites.

Invertebrate—An animal having nobackbone or spinal column.See alsoBenthic invertebrates.

Irrigation return flow— The part ofirrigation applied to the surface that isnot consumed by evapotranspirationor uptake by plants and that migratesto an aquifer or surface-water body.

Land-use study—A network ofexisting shallow wells in an areahaving a relatively uniform land use.These studies are a subset of theStudy-Unit Survey and have the goalof relating the quality of shallowground water to land use.See Study-Unit Survey.

Leaching—The removal of materialsin solution from soil or rock to groundwater; refers to movement ofpesticides or nutrients from landsurface to ground water.

Load—General term that refers to amaterial or constituent in solu-tion,suspension, or in transport; usuallyexpressed in terms of mass or volume.

Main stem—The principal course of ariver or a stream.

Maximum contaminant level(MCL)— Maximum permissible levelof a contaminant in water that isdelivered to any user of a public watersystem. MCL's are enforceablestandards established by the U.S.Environmental Protection Agency.

Mean—The average of a set ofobservations, unless otherwisespecified.

Mean discharge (MEAN)—Thearithmetic mean of individual dailymean discharges during a specificperiod, usually daily, monthly, orannually.

Median—The middle or central valuein a distribution of data ranked inorder of magnitude. The median isalso known as the 50th percentile.

Metabolite—A substance pro-ducedin or by biological processes.

Method detection limit—Theminimum concentration of a sub-stance that can be accurately ident-ified and measured with presentlaboratory technologies.

Micrograms per liter ( µg/L)—A unitexpressing the concentration ofconstituents in solution as weight(micrograms) of solute per unitvolume (liter) of water; equivalent toone part per billion in moststreamwater and ground water. Onethousand micrograms per liter equals 1mg/L.

Milligrams per liter (mg/L)— A unitexpressing the concentration ofchemical constituents in solu-tion asweight (milligrams) of solute per unitvolume (liter) of water; equivalent toone part per million in moststreamwater and ground water. Onethousand micrograms per liter equals 1mg/L.

Monitoring well— A well designedfor measuring water levels and testingground-water quality.

Mouth—The place where a streamdischarges to a larger stream, a lake,or the sea.

Nitrate—An ion consisting ofnitrogen and oxygen (NO3

-). Nitrate isa plant nutrient and is very mobile insoils.

Nonpoint source—A pollution sourcethat cannot be defined as originatingfrom discrete points such as pipedischarge. Areas of fertilizer andpesticide applications, atmosphericdeposition, manure, and natural inputfrom plants and trees are types ofnonpoint source pollution.

Nutrient— Element or compoundessential for animal and plant growth.Common nutrients in fertilizer includenitrogen, phos-phorus, and potassium

Organochlorine compound—Synthetic organic compoundscontaining chlorine. As generallyused, term refers to compoundscontaining mostly or exclusivelycarbon, hydrogen, and chlorine.Examples include organo-chlorineinsecticides, polychlor-inatedbiphenyls, and some solventscontaining chlorine.

Organochlorine insecticide—A classof organic insecticides con-taining ahigh percentage of chlorine. Includesdichlorodi-phenylethanes (such asDDT), chlorinated cyclodienes (suchas chlordane), and chlorinated ben-zenes (such as lindane). Mostorganochlorine insecticides werebanned because of their carcino-genicity, tendency to bioaccu-mulate,and toxicity to wildlife.

Organophosphate insecticides—Aclass of insecticides derived fromphosphoric acid. They tend to havehigh acute toxicity to verte-brates.Although readily metab-olized byvertebrates, some metabolic productsare more toxic than the parentcompound.


GLOSSARY

.

Pesticide—A chemical applied to

crops, rights of way, lawns or

residences to control weeds, insects,

fungi, nematodes, rodents or other

"pests."

Phosphorus—A nutrient essential for

growth that can play a key role in

stimulating aquatic growth in lakes

and streams.

Precipitation—Any or all forms of

water particles that fall from the

atmosphere, such as rain, snow, hail,

and sleet.

Radon—A naturally occurring,

colorless, odorless, radioactive gas

formed by the disintegration of the

element radium; damaging to human

lungs when inhaled.

Recharge—Water that infiltrates the

ground and reaches the saturated zone.

Relative abundance—The number of

organisms of a particular kind present

in a sample relative to the total

number of organisms in the sample.

Riparian—Areas adjacent to rivers

and streams with a high density,

diversity, and productivity of plant

and animal species relative to nearby

uplands.

Runoff—Excess rainwater or snow-

melt that is transported to streams by

overland flow, tile drains, or ground

water.

Sediment—Particles, derived from

rocks or biological materials, that have

been transported by a fluid or other

natural process, sus-pended or settled

in water.

Semivolatile organic compound(SVOC)—Operationally defined as agroup of synthetic organic com-pounds that are solvent-extractableand can be determined by gaschromatography/mass spectrometry.SVOCs include phenols, phthalates,and polycyclic aromatic hydrocarbons(PAH).

Species—Populations of orga-nismsthat may interbreed and pro-ducefertile offspring having simi-larstructure, habits, and functions.

Specific conductance—A measure ofthe ability of a liquid to conduct anelectrical current.

Streamflow—A type of channel flow,applied to that part of sur-face runoffin a stream whether or not it isaffected by diversion or regulation.

Stream reach—A continuous part ofa stream between two specified points.

Study Unit—A major hydrologicsystem of the United States in whichNAWQA studies are focused. StudyUnits are geograph-ically defined by acombination of ground- and surface-water features and generallyencompass more than 4,000 squaremiles of land area.

Study Unit Survey—Broadassessment of the water-qualityconditions of the major aquifersystems of each Study Unit. TheStudy-Unit Survey relies primarily onsampling existing wells and, whereverpossible, on existing data collected byother agencies and programs.Typically, 20 to 30 wells are sampledin each of three to five aquifersubunits.

Subsurface drain—A shallow draininstalled in an irrigated field tointercept the rising ground-water leveland maintain the water table at anacceptable depth below the landsurface.

Surface water—An open body ofwater, such as a lake, river, or stream

Suspended(as used in tables ofchemical analyses)—The amount(concentration) of undissolvedmaterial in a water-sediment mix-ture.It is associated with the materialretained on a 0.45-micro-meter filter.

Suspended sediment—Particles ofrock, sand, soil, and organic detrituscarried in suspension in the watercolumn, in contrast to sediment thatmoves on or near the streambed.

Suspended-sedimentconcentration—The velocity-weighted concentration of suspendedsediment in the sampled zone (fromthe water surface to a pointapproximately 0.3 foot above the bed)expressed as milligrams of drysediment per liter of water-sedimentmixture (mg/L).

Synoptic sites—Sites sampled duringa short-term investigation of specificwater-quality conditions duringselected seasonal or hydro-logicconditions to provide improved spatialresolution for critical water-qualityconditions.

Total DDT—The sum of DDT and itsmetabolites (breakdown products),including DDD and DDE.

Trace element—An element found inonly minor amounts (concen-trationsless than 1.0 milligram per liter) inwater or sediment; includes arsenic,cadmium, chromium, copper, lead,mercury, nickel, and zinc.


GLOSSARY

a

t

.

Urban Site—A site that has greaterthan 50 percent urbanized and lessthan 25 percent agricultural area.

Volatile organic compounds(VOC)—Organic chemicals that havea high vapor pressure relative to theirwater solubility. VOCs includecomponents of gasoline, fuel oils, andlubricants, as well as organic solvents,fumigants, some inert ingredients inpesticides, and some by-products ofchlorine disinfection.

Water-quality criteria— Specificlevels of water quality which, ifreached, are expected to render a bodyof water unsuitable for its designateduse. Commonly refers to water-qualitycriteria estab-lished by the U.S.Environmental Protection Agency.Water-quality criteria are based onspecific levels of pollutants that wouldmake the water harmful if used fordrinking, swimming, farming, fishproduc-tion, or industrial processes.

Water-quality guidelines—Specificlevels of water quality which, ifreached, may adversely affect humanhealth or aquatic life. These arenonenforceable guide-lines issued bygovernmental agency or otherinstitution.

Water-quality standards—State-adopted and U.S. EnvironmentalProtection Agency-approved ambi-enstandards for water bodies. Standardsinclude the use of the water body andthe water-quality criteria that must bemet to protect the designated use oruses.

Watershed—See Drainage basin.

Water table—The point below theland surface where ground water isfirst encountered and below which theearth is saturated. Depth to the watertable varies widely across the country


Water year—The continuous 12-month period, October 1 throughSeptember 30, in U.S. GeologicalSurvey reports dealing with thesurface-water supply. The water yearis designated by the calendar year inwhich it ends and which includes 9 ofthe 12 months. Thus, the year endingSeptember 30, 1980, is referred to asthe "1980" water year.

Wetlands—Ecosystems whose soil issaturated for long periods seasonallyor continuously, including marshes,swamps, and ephemeral ponds.

Withdrawal— The act or process ofremoving; such as removing waterfrom a stream for irrigation or publicwater supply.

Dubrovsky and others •

Water Q

uality in the San Joaquin-Tulare Basins

USG

S Circular 1159 •

1998

National Water-Quality Assessment (NAWQA) ProgramSan Joaquin-Tulare Basins

NAWQA

Stockton

Fresno

Bakersfield

StanislausRiv

er

Tuolumn e Rive

r

Merced R .

KingsRi

ve

r

Kern Riv

er

CaliforniaAqueduct

San Joaquin River

CALIFORNIA

Documents

science for a changing world Water Quality in the San ... · and 1995 from the water-quality assessment of the San Joaquin–Tulare Basins Study Unit and to relate these findings