Index of Subjects

Water and Mineral Data

Topographic Mapping 

National Water-Quality Assessment 

Sediment Resources in Grand Canyon 

National Park

Water Resources of the Upper San Pedro 

River Basin

Revised Maps of Phoenix

Mineral-Resource and Mineral-Environmental 

Assessment of the Prescott National Forest

Accounting for Consumptive Use of Lower 

Colorado River Water

Trace Metals Related to Mining

Water, Mineral, and Energy Resources on 

Indian Reservations

Geologic Information Centers

Geochemistry of the Patagonia Mountains

United States/Mexico Border

Cooperative Programs

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

U.S. Geological Survey

Programs in Arizona

Collecting, analyzing, and disseminating earth science information to solve 

problems that concern the natural 

resources of the Nation has been an integral part of the USGS mission since its 

creation in 1879. A long tradition of providing accurate and impartial information 

to everyone underscores our continued 

dedication to “Earth Science in the Public 

Service.”

Water and Mineral Data

Streamflow data are needed for waterrights issues (compacts, court decrees, and 

adjudications), flood-plain management, 

bridge design, water supply, reservoir 

operations, and flood warning. The U.S. 

Geological Survey (USGS), in cooperation with State, local, and other Federal 

agencies, operates 234 streamflow-gaging 

stations in Arizona and provides data to 

those agencies, utilities, and irrigation districts that actively manage the storage and 

release of water. At 110 of these stations, 

streamflow data are relayed by satellite 

(fig. 1) to a USGS computer in Tucson and 

can be accessed by agencies in near real 

time for immediate water-management 

decisions. The importance of the streamflow network was demonstrated during the 

floods of January and February 1993 when 

streamflow data from satellite telemetry 

were used by the Bureau of Reclamation 

(BOR) and the Salt River Project (SRP) to 

manage storage and releases from the reservoir systems along the Verde, the Salt, 

and the Gila Rivers.

 The USGS also collects data on minerals in Arizona. As a result of the North 

American Free Trade Agreement, the 

USGS is developing cooperative projects 

with Mexican counterparts to inventory 

and assess the quantity and quality of mineral resources in the border area between 

Arizona and Sonora, Mexico. This information is vital to land-management agencies, regional planners, industries, and 

local governments that are responsible for 

ensuring adequate mineral supplies.

Topographic Mapping 

Among the most popular and versatile 

products of the USGS are its 1:24,000-

scale topographic maps (1 inch on the map 

represents 2,000 feet on the ground). 

These maps depict basic natural and cultural features of the landscape, such as 

lakes and streams, highways and railroads, 

boundaries, and geographic names. Contour lines are used to depict the elevation 

and shape of terrain. Arizona is covered by 

1,968 maps at this scale, which are useful 

for civil engineering, land-use planning, 

natural-resource monitoring, and other 

technical applications. These maps have 

long been favorites with the general public 

for outdoor uses, including hiking, camping, exploring, and back-country hunting 

and fishing expeditions.

National Water-Quality 

Assessment

In 1993, the USGS initiated a regional 

assessment of water quality in central Arizona and northern Mexico. The purpose 

of the study is to describe the status and 

trends in the quality of Arizona's major 

ground- and surface-water resources 

(fig. 2) and to provide a better understanding of the factors that affect water quality. 

The study area encompasses 34,700 

square miles and includes a population of 

more than 3.1 million people. The ProFigure 1. Streamflow data-collection 

network.

Figure 2. Water-quality data-collection sites in 

Arizona.
Tucson

Lower


Colorado


River


aquifer

San


Pedro


Valley

Black


Mesa

50 KILOMETERS

0 50 MILES

0

UNITED STATES


MEXICO

Grand Canyon


National Park

Phoenix

Flagstaff

Prescott

Yuma

gram focuses on pesticides; nutrients, 

such as nitrates and phosphates; volatile 

organic compounds; and aquatic ecology. 

Data are being collected during the sampling phase from 1996 to 1998.

Sediment Resources in Grand 

Canyon National Park

In Grand Canyon National Park 

(fig. 3), operations of Glen Canyon Dam 

are affecting recreational use of sand bars, 

changing riverine habitat for plants and 

animals, and threatening a loss of archeological sites. The dam has reduced the 

sediment supply to the Grand Canyon and 

decreased the magnitude and frequency of 

floods that rebuild sand bars and transport 

coarse debris. Understanding the effects 

of regulated flows on the physical and biological systems along the Colorado River 

downstream from the dam is the objective 

of a series of studies which began in 1982. 

The studies, being conducted by or in 

cooperation with contractors, universities, federal and state agencies, and Indian 

tribes, will provide managers with a scientific basis for optimizing dam operations.

USGS studies show that low, moderately fluctuating flows through the dam 

transport sand, brought to the canyon by 

tributaries downstream from the dam, 

through the canyon along the channel bed. 

These low flows also allow the build up of 

coarse debris that can affect the navigability of the river. A test of controlled flood 

releases in the spring of 1996 showed that 

enough sand is available from tributaries 

downstream from the dam to rebuild sand 

bars, and that controlled floods can redistribute recently-deposited coarse debris. 

The USGS is developing a series of computer models to describe the deposition 

and erosion processes in the Grand Canyon. These models will make it possible 

to simulate different operational plans for 

the dam, and to predict their effects on 

sediment resources in the canyon.

Water Resources of the Upper 

San Pedro River Basin 

The San Pedro River in southeastern 

Arizona has perennial flow along much of 

its length, from its headwaters near Cananea in Sonora, Mexico, to its confluence 

with the Gila River at Winkleman. The 

San Pedro River includes the site of the 

first National Riparian Conservation Area 

established by the Bureau of Land Management (BLM). The area (fig. 3) is habitat for diverse plants and animals, some of 

which are threatened or endangered; a 

vital flyway for migrating birds; and the 

basis of the substantial ecotourism industry in the area. 

Ground-water withdrawals associated 

with population growth in Cochise 

County and the city of Sierra Vista may 

decrease streamflow in the upper San 

Pedro River and, thus, adversely affect the 

riparian corridor. These withdrawals also 

may complicate the adjudication of water 

rights that involve Native American 

Tribes. Subsidence and the development 

of earth fissures are other features that 

may result from lowering of the water 

table.

 USGS geologists, hydrologists, and 

geophysicists are working to determine 

the three-dimensional subsurface shape of 

the San Pedro Basin, to estimate the character and distribution of the basin-fill sediments, and to obtain objective data on the 

amount of ground water stored in basin 

aquifers and on the connection between 

these aquifers and the river. The geological and geophysical studies are currently 

(1996) focused in the upper San Pedro 

Valley between Cananea and Benson.

 To date, geologic mapping is being 

conducted north of Cananea. New geophysical data in Arizona have defined two 

northwest-trending subbasins beneath the 

upper San Pedro Valley. The Palominas 

Subbasin is about 2,300 meters deep, and 

the Huachuca City Subbasin is about 

1,100 meters deep. They are separated by 

an east-trending buried ridge beneath 

Sierra Vista.

 These data obtained in the USGS 

investigations are essential to all the parties involved in discussions on water 

usage in the San Pedro Valley, including 

the cooperating agencies—the BLM, the 

BOR, the U.S. Army, the Arizona Department of Water Resources, the University 

of Arizona, the Arizona Geological Survey, the San Pedro Technical Advisory 

Committee, The Nature Conservancy, 

and Cochise County.

Revised Maps of Phoenix 

The USGS has started a 1:24,000-

scale series mapping revision/replacement 

project for the 41 maps that cover Phoenix 

and the surrounding area. Existing maps 

are being updated to reflect recent urban 

growth and ground subsidence. The 

project is part of the USGS program for 

replacement mapping in areas of critical 

need, such as those with rapid urban 

growth.

To date, aerial photographs have been 

acquired for the area and high-accuracy 

surveys have been completed in partnership with the U.S. Department of Commerce, National Geodetic Survey. The 

USGS is evaluating additional cartographic-control requirements that are necessary for compiling new maps. Once 

analyzed, these data provide critical information that concerns the location and 

magnitude of subsidence in the Phoenix 

area.

Mineral-Resource and MineralEnvironmental Assessment of 

the Prescott National Forest

 At the request of the U.S. Forest Service, the USGS is conducting mineralresource and mineral-environmental 

assessments of the 1.2-million-acre Prescott National Forest. The forest is centered around the rapidly growing city of 

Prescott and borders the developing Verde 

and Chino Valleys in central Arizona. It 

Figure 3. Selected project areas. includes or is close to current and historic 
mining districts that have made significant contributions to the Nation's mineral 

wealth. The forest and surrounding areas 

continue to attract commerce, recreation, 

and mineral exploration. Recent economic development and growth around 

the forest have placed demands on water 

resources and industrial materials within 

the forest and have created conflicting 

views on future mining.

In 1994, the USGS began a project to 

assess the mineral resources of the forest 

and to evaluate the historic and current 

environmental hazards associated with 

mining. These studies considered a variety of point sources, including old mines, 

recent mines, mills, and smelters; desert, 

semiarid, and montane climatic regimes; 

and several geologic settings. Geochemical studies of mining and smelting sites in 

the Prescott/Jerome area have determined 

the probable dispersion into and possible 

natural mitigation of toxic metals by the 

environment.

 The USGS has completed mineral 

resource assessments of the Kaibab, the 

Coronado, and the Coconino National 

Forests. These assessments have become 

part of the basic data used for management planning for these National Forest 

areas.

Accounting for Consumptive 

Use of Lower Colorado River 

Water

The Colorado River Compact of 1922 

requires the participation of the USGS 

and the BOR to monitor flow and estimate 

consumptive use of water from the Colorado River. The U.S. Supreme Court 

Decree of 1964, Arizona v. California, is 

specific about the responsibility of the 

Secretary of the Interior to account for the 

consumptive use and distribution of water 

from the lower Colorado River in Arizona, 

California, and Nevada. Domestic, municipal, and industrial consumptive uses of 

water pumped from wells are components 

of the water budget; therefore, accounting 

for consumptive use from all these wells 

provides an estimate and distribution of 

consumptive use by vegetation to agricultural users. The identification of wells outside the flood plain that yield water that 

will be replaced by water from the river is 

based on the concept of a river aquifer and 

an “accounting surface” within the river 

aquifer. The “accounting surface” provides a uniform criterion of identification 

based on hydrologic principles for all 

users that pump water from wells. 

Accounting for the consumptive use of 

Colorado River water requires the identification of all points of withdrawal of 

water; however, this accounting is incomplete because the location of all wells is 

unknown. Cooperative work continues 

with the BOR to inventory all wells completed in the river aquifer so they can be 

included in the water-accounting process.

Trace Metals Related to Mining

Trace-metals and radionuclides in 

water and sediments from mining is a possible hazard for the people and environment of Arizona. Copper has been mined 

near Globe since 1903. In 1984, the 

USGS, in cooperation with the Arizona 

Department of Health Services and the 

SRP, initiated a study of ground-water 

quality. The study focuses on the 

geochemical processes that control tracemetal movement in ground-water systems. An understanding of the processes 

that control trace-metal movement 

obtained during this ongoing study may 

be useful in other areas of the United 

States.

Water, Mineral, and Energy 

Resources on Indian 

Reservations

The desert environment, drought, continued growth, and planned development 

are placing increasing demands on the 

water and mineral resources and complicating the adjudication of water rights for 

Native American Tribes throughout Arizona. The diversion of surface flows, 

pumpage of ground water, and degradation of water quality from agriculture, 

urbanization, and mining have decreased 

the amount of usable water in a region 

where water is scarce.

The USGS is involved in data collection and interpretive studies on 10 reservations in Arizona that will assess the 

quantity and quality of the Tribes’ water 

resources, provide an understanding of the 

hydrologic system, and determine how 

activities in a basin could divert streamflow and ground water and affect water 

quality. The results from this work will 

help the Tribes plan growth and economic 

development.

The Black Mesa coal field in northeastern Arizona is a major producer of 

coal for powerplants in the Southwestern 

United States. Production from this field 

is a major source of revenue for the 

Navajo and the Hopi Tribes. The USGS 

study of the Black Mesa, in cooperation 

with the Tribes, outlines the distribution 

of coal, determines the geologic controls 

on coal thickness and distribution, estimates the amount of coal that is economically recoverable, and analyzes the 

composition of coal. Both Tribes can use 

the results of this study to aid in resource 

inventories, land-use planning, and predicting environmental effects of coal use.

The Tohono O’Odham Nation is supporting a study to measure streamflow in 

which an array of sensors are buried in 

transects across an unstable sand channel 

of a large ephemeral wash. This installation of sensors should significantly 

decrease missing records and improve the 

accuracy of records of surface inflow to 

the Nation’s lands at the Mexican border.

Geologic Information Centers

The National Geomagnetic Information Center (NGIC), which is located in 

Golden, Colorado, provides magnetic 

data to the scientific community and the 

general public over a commercial telephone network. The USGS operates 11 

magnetic observatories across the United 

States, 1 of which is located in Tucson. 

Data from these observatories are used to 

prepare nautical and aeronautical navigation charts, by the Federal Aviation 

Administration to update magnetic headings on runways and airports and by other 

users to improve the accuracy of groundlevel base data for satellite and airborne 

surveys. Information from the NGIC also 

is used to help power companies understand and plan for power-system failures 

caused by high-frequency magnetic variations. An Earth Science Information 

Center, operated by the USGS and the 

Arizona Geological Survey, is located in 

Tucson.
Geochemistry of the Patagonia 

Mountains

The Patagonia Mountains are the most 

highly mineralized part of the Coronado 

National Forest but have seen little largescale mining development. For this reason, the area (fig. 4) is a unique laboratory in which to study the natural effects 

of mineralizing processes on rocks, water, 

and vegetation in arid environments. 

USGS scientists are beginning studies to 

measure naturally occurring levels of 

metals in rocks, stream sediments, water, 

and vegetation and to determine their 

mobility, bioavailability, and leachability 

in this arid environment. Samples of surficial materials are analyzed and compared 

with drill core data from the Red Mountain porphyry copper deposit, which is in 

the Patagonia Mountains.

The results of this work provide the 

data on which to base remediation expectations and standards as new mining operations are undertaken. Appropriate and 

effective remediation standards will 

ensure the availability of materials, such 

as copper, that are critical to the Nation’s 

industrialized economy and, at the same 

time, ensure the continued safety of 

drinking water and water-based recreational sites that surround the mountain 

range. 

United States/Mexico Border

Arizona is one of four States involved 

in U.S./Mexico border mapping activities. 

The USGS is working with Federal, State, 

and local agencies and other organizations in the United States and Mexico to 

develop digital-map data for a 100-mile 

zone on each side of the border. The 

USGS is obtaining color infrared aerial 

photography for the zone on the U.S. side 

of the border. From these aerial photographs, the USGS produces digital orthophotoquads that are used to revise maps 

and data bases to support studies by scientists and government agencies that deal 

with the environment and resource management. 

Cooperative Programs

Work is pursued in partnership with 

numerous State, local, and tribal agencies, 

as well as Mexican agencies. A few examples not referenced above are the Flood 

Control District of Maricopa County, the 

Pima County Department of Transportation and Flood Control District, the city of 

Tucson, the White Mountain Apache 

Tribe, and Consejo Recursos Minerales. 

The USGS provides support to the Arizona Water Resources Research Institute, 

which conducts research, education, and 

information and technology transfer.

USGS State representative

375 S. Euclid Avenue

Tucson, AZ 85719

(520) 670-6671

Fax: (520) 670-5592

Email: dc_az@usgs.gov

Additional earth science

information can be found by

accessing the USGS Home Page

on the World Wide Web at

http://www.usgs.gov/

For more information on

all USGS reports and products

(including maps, images,

and computerized data), call

1-800-USA-MAPS

The USGS provides maps,

reports, and information to help

others meet their needs to manage,

 develop, and protect America’s water,

 energy, mineral, biological, and land

resources. We help find the natural

resources needed to build tomorrow

and supply the scientific understanding needed to help minimize or mitigate the effects of natural hazards

and environmental damage caused

by natural and human activities. The

results of our efforts touch the daily

life of almost every American.

U.S. Geological Survey

Fact Sheet FS-003-96

Figure 4. The creek drains a small prospect and tailings pile. Location is downstream from 3-R 

mine. The photograph was taken December 6, 1994

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