EXPLANATION

Predicted arsenic concentrations, micrograms per liter

Less than 1.0

1.0 to 1.9

2.0 to 2.9

3.0 to 4.9

5.0 to 9.9

10 to 24

Equal to or greater than 25

Arsenic Predictions

Observed arsenic concentration, micrograms per liter

Less than 1.0

1.0 to 1.9

2.0 to 2.9

3.0 to 4.9

5.0 to 9.9

10 to 24

Equal to or greater than 25

EXPLANATION

Arsenic Training Observations

EXPLANATION

Hydrogeologic area boundary—Names of 

the hydrogeologic areas are shown on 

the online version of this plate available 

at http://pubs.usgs.gov/sim/3234/

Hydrogeologic areas

Trinity

River

Eel River

Russian

River

River

Sacramento

Feather River

North Yuba River

American River

River

Mokelumne

River American

North Fork

Tuolumne River

Merced River

River

San Joaquin

River

Joaquin

San

River

Kings

Salinas River

Kern River

Quinn River

River

Humboldt

Reese River

Sevier River

River

Bear

Jordan River

Meadow Valley

Wash

White River

Pahranagat Wash

Muddy

River

Amaragosa

River

Verde River

Salt River

Colorado

River

River

Gila

Mojave River

Rio Grande

Rio Chama

Puerco

Rio

Owens River

Grande

Rio

Great

 Salt

 Lake

Walker

Lake

Pyramid

Lake

Rye Patch

Reservoir

Lake

Tahoe Walker

River

Lake

Mead

Lake

Mohave

Smith

River

Basin

Klamath

Basin

Scott

River

Basin

Shasta

Valley

TrinitySalmon

Basin

Shasta

Lake Area

MadRedwood

Basin

Mattole

River

Basin

Lower

Pit River

Basin

Butte

Creek

Basin

Eel

River

Basin

Northern

Coastal

Basins

Ukiah

Valley

Sacramento

Valley

Upper Cache

Creek Basin

Santa Rosa

Valley

Upper Putah

Creek Basin

Napa

Valley Bodega

Basin

Petaluma

Valley

Sonoma

Valley Suisun- Fairfield

Valley

Smith

Valley

Mason

Valley

Carson

Valley

Tahoe

Valley

Santa

Rosa

Valley

Eagle

Valley

Washoe

Valley Dayton

Valley

Churchill

Valley

Truckee

River BasinTracy Segment

Truckee

River

Basin- Reno/Sparks

Segment

Lemmon

Valley

Spanish

Springs

Valley

Truckee

River BasinDodge Flat

Lost River

Basin

Upper Pit

River Basin

Lake

Almanor

Valley

Indian

Valley

Upper

Susan

River

and Eagle

Lake

Valley

Sierra

Valley

Carson

Desert

Fernley

Area

Warm

Springs

Valley

Long

Valley

Pyramid

Lake

Valley

Honey

Lake

Valley

Willow Creek

and Horse

Lake Valleys

Smoke

Creek

Desert

San

Emidio

Desert Kumiva

Valley

Winnemucca

Lake

Valley

Granite

Springs

Valley

Humboldt

River

BasinLovelock

Segment

Madeline Plains

Duck Lake

Valley Hualapi

Flat

Black

Rock

Desert

Humboldt

River BasinImlay Segment

Goose

Lake

Valley

Surprise

Valley

Long

Valley

Massacre

Lake

Valley

Swan

Lake

Valley

High Rock

Lake Valley

Mud

Meadow

Creek

Basin

Virgin

Valley

Summit

Lake

Valley

Gridley

Lake

Valley

Continental

Lake

Valley

Pine

Forest

Valley

Kings River

and Desert

Valleys

Ione

Valley

Gabbs

Valley

East Soda

Spring

Valley

West

Soda

Spring

Valley

Walker

Lake

Valley

East Walker

River Basin

Antelope

Valley

Dixie

Valley

Fairview

Valley

Stingaree

Valley

Smith

Creek

Valley

Edwards

Creek

Valley

Buena

Vista

Valley

Silver State

and Quinn

River Valleys

Grass

Valley

Pleasant

Valley

Jersey

Valley

Wah Wah

Valley

Snake

Valley

North

Spring

Valley

Tippett

Valley

Thousand Springs

Valley-Toano and

Rock Spring Areas

Thousand Springs

Valley-Rocky

Butte Area

Grouse

Creek

Valley

East Park

Valley

West Park

Valley

Pilot

Valley Pilot

Creek

Valley

Thousand

Springs

ValleyMontello

and

Crittenden

Area

Great Salt

Lake Desert

Goshute

Valley

Sink

Valley

Great

Salt Lake

Tooele

Valley Skull

Valley

Antelope

Valley

Cache

Valley

Curlew

Valley

Hansel

and Northern

Rozel Flat

Pocatello

and

Blue

Creek

Valleys

Lower

Bear

River

Basin

East

Shore

Area

Salt Lake

Valley

Utah Valley

Cedar

Valley

Rush

Valley

Dugway

Valley

Deep

Creek

Valley

Northern

Juab

Valley

Leamington

Canyon Area

Sevier Desert

Fish

Springs

Flat

Tule

Valley

Pavant

Valley

Cave

Valley

White

River

Valley

North

Railroad

Valley

South

Little

Smoky

Valley

North Little

Smoky

Valley

Little

Fish

Lake

Valley

Monitor

Valley

Big Smoky

ValleyNorthern

part

Upper

Reese

River

Valley

Antelope

Valley

Kobeh

Valley

Grass

Valley

Carico

Lake

Valley

Antelope

Valley

Steptoe

Valley

South

Butte

Valley Long

Valley

Jakes

Valley

Newark

Valley

Diamond

Valley

Pine

Valley

Middle

Reese

River

Valley

Humboldt

River

Basin- Winnemucca

Segment

Buffalo

Valley

Humboldt

River

Basin-Red

House

Segment Rock

Creek

Valley

Maggie

Creek

Basin Susie

Creek

AreaHumboldt River

Basin-Elko and Marys Creek Segment Dixie Creek

and Tenmile Creek Basin

South

Fork

Area Lower

Reese

River

Valley Crescent

Valley

Humboldt River

Basin-Boulder

Flat Segment

Huntington

Valley

Ruby

Valley

North

Butte

Valley

Clover

Valley

Independence

Valley

Hardscrabble

Area

Little

Humboldt

Valley

Paradise

Valley

Willow

Creek

Valley

North Fork

Humboldt

River Basin

and

Lamoille

Valley

Upper

Humboldt

River Basin

Thousand Springs

Valley-Herrell

Siding and Brush Creek Area

Detrital

Valley

Lake

Mohave

Basin

Truxton

Wash

Hualapai

Basin

Lake

Mead

Basin

Garnet

and

Hidden

Valleys

California

Wash

Lower

Moapa

Valley

Muddy

River

Springs

Area

Lower

Meadow

Valley

Wash

Kane

Springs

Valley

Delamar

Valley

Clover

Valley

Panaca

Valley

Escalante

Desert EagleRose-Dry

Valley

Patterson

Valley

South

Spring

Valley

Pine

Valley

Lake

Valley

Dry Lake

Valley

Pahroc

Valley

Cedar

City

Valley

Milford

Area

Beaver

Valley

Parowan

Valley

Las Vegas

Valley

Sacramento

Valley

Mohave

Valley

South Piute

Valley

North

Piute

Valley

Big Sandy

River

Basin

Big

Chino

Basin

Verde

Valley

San Joaquin

Valley

South

Tikapoo

Valley

Coyote

Spring

Valley

Pahranagat

Valley North

Tikapoo

Valley

Emigrant

Valley

Yucca

Flat

Oasis

Valley

Gold

Flat

Cactus

Flat

Kawich

Valley

Coal

Valley

Garden

Valley

Penoyer

Valley

South

Railroad

Valley

Hot Creek

Valley

Stone

Cabin

Valley

Saline

Valley

Eureka

Valley

Deep

Springs

Valley

North

Owens

Valley

Sarcobatus Flat

Lida

Valley

Long

Valley

Fish Lake

Valley

Clayton

Valley Stonewall

Flat

Ralston

Big Smoky Valley

ValleyTonapah Flat

Columbus

Salt Marsh

Valley

Alkali

Spring

Valley

Adobe Lake

Valley

Mono

Valley

Huntoon

Valley

Teels

Marsh

Valley

Rhodes

Salt Marsh

Valley

Monte

Cristo

Valley

Garfield

Bridgeport Flat

Valley

Antelope

Valley

Fenner

Valley

Kelso

Valley

Soda Lake

Valley

Lower Mohave

River Valley

Harper Valley Coyote

Lake Valley

CroniseValley

Superior

Valley

Goldstone

Valley

Red Pass

Valley

Riggs

Valley Bicycle

Valley

South

Ivanpah

Valley

Shadow

Valley

North

Ivanpah

Valley Mesquite

Valley

Valjean

Valley

California

Valley

Chicago

Valley

Freemont

Valley Cuddeback

Valley

Searles

Valley

East Pilot

Knoband

Brown

Mountain

Valleys

Leach

Valley

Lost Lake

and Owl Lake Valleys

Indian

Wells

Valley

Rose

Valley

Panamint

Valley

Death

Valley

Darwin

Plateau

Basins

South

Owens

Valley

Race Track

and Hidden

Valleys

Amargosa

Desert

Lower

Amargosa

Valley

Pahrump

Valley

Indian

Springs

Valley

Frenchman Flat

South Three

Lakes

Valley

NorthThree

Lakes Valley

Fortymile

Wash

Crater

Flat

Mercury

Valley

Rock

Valley

Lanfair

Valley

Eldorado

Valley

Hidden

Valley

Jean

Lake

Valley

Tomales- Drakes

Basin Novato

Valley ConcordPittsburg

Area San Ramon

Valley

East Bay

Plain

San Francisco

Bay Peninsula

Basins

San

Mateo

Coastal

Basins Santa

Clara

Valley

Livermore

and Sunol

Valleys

Upper

Coyote

Creek

Basin

Monterey

Basin

San BenitoUpper Pajaro

River Basin

Central

California

Coastal

Basin Middle

Salinas River

Valley

Lockwood

Valley

Cholame

Valley

Upper

Salinas River Valley

Carrizo

Plain

Cuyama Santa Valley Maria River

Valley San Antonio

Creek Valley

Coachella

Valley

Borrego

Valley

Salton

Sea

Cottonwood, Campo, and Potrero Valley

Vallecito,

Carrizo,

and Coyote

Wells Valleys

Orocopia

Valley

Pinto

Basin

Ogilby

Valley

Imperial

Valley

Chuckwalla

Valley

Arroyo

Seco Basin

Palo

Verde

Valley

Yuma

Wash

La Posa

Plain

Ward and

Rice

Valleys

Johnson

Valley

Twentynine

Palms Area

Bristol

Valley

Dale

Valley

Cadiz

Valley

Parker and Vidal

Valleys

Renegras

Plain

Chemehuevi

Valley Lake

Havasu

Basin

Lower Bill

Williams

River Basin

Broadwell

Valley Lavic

Valley

Butler

Valley

King and

San

Cristobal

Valleys

Upper Mohave

River Valley

Santa Ana

Inland

Basin

San

Jacinto

Basin

Temecula

Santa Valley

Margarita

Valley

San Luis ReyEscondido

Coastal Basin

Yuma

Basin

Lucerne

Valley

Mohave

River

Valley

Lechuquilla Desert Mohawk

Valley

Santa

Ynez River

Valley

Santa Barbara

Coastal Basins

Ventura

River

Valley

Santa

Clara River

Valley

Calleguas-Oxnard

Basin

Malibu

Coastal

Basins Coastal

Plain of

Los Angeles

San Gabriel Valley

Santa Ana

Coastal

Basin

Aliso- San Onofre

Coastal Basins

San Diego

Coastal

Basins

San Fernando Valley

Palomas and

Sentinal

Plains

McMullen

Valley

Harquahala Basin

Bullard

Wash

Burro

Creek

Basin Little

Chino

Basin

Agua Fria

River

Basin

Kirkland

Creek

Basin

Lower Verde

River Basin

Upper

Hassayampa

River Basin

Lake

Pleasant

Paradise Middle Valley Hassayampa

River Basin

Salt River

ValleyPhoenix Area

Salt RiverValley- Chandler Area

Growler

Valley

Gila

Bend

Basin

Waterman

Wash

Valley of

the Ajo

Vekol

Valley

Stanfield

Area

Eloy

Area

Donnelly

Wash

Dripping

Springs

Wash

Lower San

Pedro River

Basin

Santa

Rosa

Valley

Aguirre

Valley

Avra

Valley

Willcox

Basin

San Simon

Valley

Aravaipa

Valley

Safford

Valley

Quijotoa

Valley

Baboquivari

and Tecolote

Valleys

Altar

Valley

Upper Santa

Cruz River

Basin

Cienega

Creek

Basin Upper

San Pedro

River Basin

Douglas

Basin

Duncan

Basin

Lordsburg

Animas Basin

Basin

Mimbres

River

Basin

Playas

Basin

Mesilla

Basin

Palomas

Basin

Jornada del

Muerto BasinSouthern Part

Tularosa

Basin

Engle

Basin

MontecelloCuchillo

Basin

San

Agustin

Basin San

Marcial

Basin

Jornada del

Muerto BasinNorthern Part

Socorro

Basin

La Jencia

Basin

AlbuquerqueBelen

Basin

Espanola

Basin

San Luis

Valley

ARIZONA NEW MEXICO

UTAH COLORADO

MEXICO

OREGON

CALIFORNIA

IDAHO

WYOMING

NEVADA

35°

40°

40°

124°

124°

117°

110°

Reno

Sacramento

San

Francisco

Stockton

Modesto

San Jose

Fresno

Bakersfield

Las Vegas

Los Angeles

San Diego

Yuma

Phoenix

Tucson

El Paso

Flagstaff

Santa Fe

Albuquerque

Salt Lake City

U.S. Geological Survey digital data, 1:2,000,000, 2,500,000, and 5,000,000 scale, 2003, 2005, and 2006

National Elevation Data 1:24,000, 1999

Albers Equal Area Conic Projection, central meridian -113, NAD 83

Pacific Ocean

Las

Cruces

Observed and predicted arsenic concentrations in basin-fill aquifers of the Southwest Principal Aquifers study area

By

 Kimberly R. Beisner, David W. Anning, Angela P. Paul, Tim S. McKinney, Jena M. Huntington, Laura M. Bexfield, and Susan A. Thiros

2012

Any use of trade, product, or firm names in this publication is for descriptive purposes only 

and does not imply endorsement by the U.S. Government.

For sale by U.S. Geological Survey, Information Services, Box 25286, Federal Center, 

Denver, CO 80225, 1–888–ASK–USGS

Digital files available at http://pubs.usgs.gov/sim/3234/

Suggested citation: Beisner, K.R., Anning, D.W., Paul, A.P., McKinney, T.S., Huntington, 

J.M., Bexfield, L.M., and Thiros, S.A., 2012, Maps of estimated nitrate and arsenic 

concentrations in basin-fill aquifers of the southwestern United States: U.S. Geological Printed on recycled paper Survey Scientific Investigations Map 3234, pamphlet 8 p., 2 sheets.

0 50 100 150 200 MILES

0 50 100 150 200 KILOMETERS

NATIONAL GEODETIC VERTICAL DATUM OF 1929

Elko

U.S. Department of the Interior

U.S. Geological Survey

National Water-Quality Assessment Program Scientific Investigations Map 3234

Sheet 2 of 2

Southwest Principal Aquifer 

(SWPA) study-area boundary

117°

35°

110°

Alamosa

Concentration data is from Anning and others, 2012, for an aquifer penetration depth of 200 feet. 

Systematic changes in predicted concentrations with aquifer penetration depth were not found in 

most areas