U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet 004-99

December 1999

Arizona

Increased Selenium Levels in

Lower Colorado River Organisms

Some organisms in the lower Colorado River have attained or are

approaching levels of selenium

accumulation that are known to cause

reproductive abnormalities. USGS

researchers at the Arizona Cooperative Fish and Wildlife Research Unit

are studying the pathways and

impacts of selenium accumulation.

Selenium originates from shales in

the upper Colorado River Basin, not

from irrigation return flow, as is often

assumed.

Studies have shown that selenium

levels are elevated in the tissues of

clams, freshwater shrimp, aquatic

insects, crayfish, fish, fish-eating

birds, and other birds that live along

the river. Selenium levels generally

are highest in organisms living in

backwater lakes along the lower

Colorado River that have restricted

circulation but that are open to the

river. Studies have revealed, however,

that increasing water flow from these

backwater lakes does not lower

selenium levels in the lakes’ aquatic

inhabitants. The USGS is working

with other agencies to evaluate

selenium levels in wetlands near the

mouth of the Colorado River in

Mexico.

Aquaculture and Agriculture—A

Productive Combination for Arid

Regions

By combining agriculture and aquaculture, farmers can produce two

crops using the same water, thereby

reducing water costs and increasing

farm revenues by as much as 7 percent. Wastewater from an aquaculture

operation can be used to irrigate

crops, thus eliminating the cost of

effluent treatment or disposal and

providing crops with an additional

source of nitrogen.

Aquaculture and agriculture are more

efficiently integrated when fish are

raised in preexisting irrigation

structures using no more water than is

required to support crop growth.

USGS researchers at the Arizona

Cooperative Fish and Wildlife

Research Unit have cultured fish in

irrigation ditches where water is

allowed to flow through the fishculture area only when crops are

being irrigated (fig. 1). Developing

countries have shown great interest in

these “Pulsed Flow Culture Systems”

because of the potential for reducing

water use and increasing revenues.

Geologic Information for National

Parks

USGS geologists, in cooperation with

the National Park Service, are creating geologic maps and interpretive

materials for selected national parks.

In the Lake Mead National Recreation Area in northwestern Arizona,

geologists are reconstructing the long

and complex geologic story of the

region over the last 1.8 billion years.

In Grand Canyon National Park,

geologists are creating maps of the

entire Grand Canyon, within the park

and outside park boundaries. Details

of both projects can be seen on the

Web at http://wrgis.wr.usgs.gov:80/

docs/wgmt/nationalparks/

NatParks.html/

Also in Grand Canyon National Park,

geologists are identifying archeological sites in danger of destruction,

establishing a time scale of predam

erosion and deposition, and interpreting long-term patterns of sediment

input from the Paria and Little

Colorado Rivers. A recently developed model of near-channel erosion

Figure 2. The Grand Canyon region is

the focus of geologic mapping.

Figure 1. USGS biologists sample fish

raised in irrigation ditches.
science for a changing world

will help geologists determine the

effects of streamflow on cultural

resources along the Colorado River.

Metals Transport in River Basins

USGS geologists are combining new

and existing geologic data and

imagery to create three-dimensional

views and models of the upper Santa

Cruz and San Pedro River Basins of

southeastern Arizona and northern

Sonora, Mexico. This study emphasizes gaining a better understanding

of the baseline condition, aquifer

systems, and distribution of metals in

these areas. The goal of this research

is to provide objective data to use in

resolving land-use issues about

mineral and water resources.

Interactions Between Ground

Water and Surface Water

In the Southwest, most replenishment, or recharge, of ground water

takes place at high elevations along

the margins of many aquifers. Water

moves underground through these

aquifers until it comes to the surface

in discharge areas at streams, springs,

lakes, and wetlands. Ground-water

pumping between recharge and

discharge areas may ultimately

reduce water flow to the discharge

areas, which may, in turn, bring about

changes to the community of organisms that inhabit these areas.

In 1998, USGS hydrologists began

studying the interactions of ground

water and surface water in the

southwestern United States. Management of areas near rivers that depend

on ground water is important to the

management of urban and agricultural

water supplies because of potential

threats to endangered species and to

the health of these natural systems. In

this study, hydrologists are assessing

the impacts of climate variation and

ground-water development on

ground-water systems and riverdependent biological communities.

Hydrologists also plan to develop

improved methods to quantify

ground-water recharge and assess the

potential effects of future climate

changes and development on groundwater systems in parts of California,

Nevada, Utah, Arizona, and New

Mexico. Information gained from this

study is intended to help scientists

assess the availability and

sustainability of ground-water

resources in the rapidly growing

southwestern United States. Much of

the work is being done in cooperation

with State and local agencies in the

study area.

New Tools for Studying Hydrology

Several new tools are helping USGS

hydrologists gather information on

ground-water recharge, sediment

erosion, and streamflow.

In the Tucson area, hydrologists are

using an instrument capable of

measuring Earth’s gravitational pull

very precisely to measure directly the

amount of ground-water recharge in

near-surface aquifers following

floods like those that occurred in

1992–93. Gravitational pull increases

as sediment in an aquifer becomes

saturated with water. This method

was developed in cooperation with

the Arizona Department of Water

Resources, Metropolitan Domestic

Water Improvement District, City of

Tucson, Town of Oro Valley, and

Pima County.

New sensors developed in Tucson are

being used to measure erosion and

deposition of sediment. Each sensor

contains a liquid cell that weighs the

sediment and the water lying above it

and a pore-pressure device that

weighs the water alone. The difference between the two measurements

is the weight of sediment above the

sensor. Sensors buried in a sandbar

along the Colorado River in the

Grand Canyon made it possible for

Figure 4. Water moves underground from mountains to streams in many areas of

the Southwest. Pumping of ground water can deplete the supply of water to

streams.

Wetlands

Pumping

Recharge

Stream

Outflow to

surface water

Aquifer

Inflow from

surface water

Recharge

Bedrock

Figure 3. Artifacts in the Grand

Canyon may be susceptible to erosion

in small drainages along the river.
Arizona

hydrologists to document deposition

and erosion during an experimental,

human-induced flood in 1996.

Information about the amount of sand

stored in the canyon and how sand

moves in response to releases from

Glen Canyon Dam is important to

agencies that manage the resources of

the Colorado River, including the

Bureau of Reclamation, the Western

Area Power Administration, the U.S.

Fish and Wildlife Service, and the

National Park Service.

Stream-monitoring technology took a

step forward with the installation in

1998 of a camera at a USGS

streamflow-gaging station on the

Verde River near Scottsdale. The

station is maintained in cooperation

with the Salt River Project. During

the day, an image captured by the

camera is transferred hourly by

cellular phone to the USGS office,

where it is displayed on the Web at

http://az.water.usgs.gov/

The USGS in Space

USGS planetary geologists are

working with the National Aeronautics and Space Administration

(NASA) to provide direct support to

planetary spaceflight missions. The

geologists participate in instrument

design and development, mission

design and planning operations, and

data analysis. Using their skills in

image processing and planetary

mapping, USGS geologists also

produce materials used by the international space science and education

communities.

The USGS has members on the flight

team that is supporting the Mars

Global Surveyor Mission, currently

orbiting Mars. The goal of the

mission is to provide global maps of

Martian surface topography and

mineral distribution and to monitor

Martian weather over a 2-year period.

Information gathered will significantly enhance our understanding of

Mars and also may provide insights

into Earth’s past.

The USGS is participating in the

NASA Cassini Mission to place a

spacecraft in orbit around Saturn and

a probe on Titan—one of Saturn’s

moons—in 2003. The Cassini spacecraft will orbit Saturn for 4 years and

will send back information about the

planet’s moons, rings, and magnetic

environment. Titan is particularly

interesting to scientists because its

surface and atmosphere may contain

hydrocarbons from which life is

thought to have begun on Earth. (Life

is not expected to exist on Titan,

because temperatures are about

–360 °F.)

Deep-Space 1, a solar-electron/ionpropulsion spacecraft, will soon

embark on a mission to investigate

comets and asteroids at the far

reaches of the solar system. USGS

scientists are involved in the flight of

this spacecraft and are part of the

team responsible for designing and

producing specialized instruments,

which include a miniature camera,

that Deep-Space 1 will carry.

Information on the USGS’s planetary

and terrestrial programs in northern

Arizona can be seen on the Web at

http://wwwflag.wr.usgs.gov/

Maps and Imagery for Many Uses

USGS cartographers have completed

a set of 1,956 digital maps of the

entire State of Arizona using Digital

Raster Graphics (DRG’s) developed

from topographic maps (at a scale of

1:24,000). These maps depict natural

and human-made features, which

include lakes, streams, highways,

railroads, and boundaries, as well as

geographic names. Contour lines

show elevation and shape of the

terrain. These maps are useful for

civil engineering, land-use planning,

natural-resource monitoring, and

other technical and scientific applications.

Another set of maps, based on Digital

Elevation Models (DEM’s), also have

been completed for Arizona. DEM’s

depict topographic relief. Maps

Figure 5. Gravitational pull measured

along Swan Road near Tucson

increased in response to groundwater recharge from floods in Rillito

Creek in 1992–93.

80

60

40

20

–20

0

GRAVITY CHANGE SINCE

DECEMBER 1992, IN MICROGALS

RECHARGE

April 3,

1993

Dec. 31,

1993

S FLOOD PLAIN N Rillito Creek

Rillito Creek

at Dodge Blvd

DISCHARGE, IN CUBIC

FEET PER SECOND

0

12,000

9,000

6,000

3,000

1992 1993

0.0 0.5 1.0 1.5 2.0 MILES

DISTANCE ALONG SWAN ROAD

Figure 6. Mars Pathfinder provided panoramic views of the Martian landscape.

In this view, look for the rover “Sojourner” nestled against a large rock named

“Yogi.”
Printed on recycled paper

USGS office locations USGS State Representative

520 N. Park Avenue, Suite 221

Tucson, AZ 85719

(520) 670-6671, ext. 221

FAX (520) 670-5592

USGS Home Page

http://www.usgs.gov

Reports and products

1-888-ASK-USGS

The USGS has 304

employees in Arizona

Yuma Tucson

Tempe

Flagstaff

created from DEM’s show threedimensional perspectives of the

landscape, help researchers to assess

slope and aspect when mapping

vegetation and habitats, are used with

hydrologic computer models for

flood analysis, and are used for

planning hazard mitigation.

USGS cartographers are producing

another digital product—Digital

Orthophoto Quadrangles (DOQ’s)—

in cooperation with the USDANatural Resources Conservation

Service and the Farm Service

Agency. DOQ’s are scanned aerial

photographs in which distortion and

displacement caused by camera

orientation and terrain have been

digitally removed. These very

accurate aerial images then can be put

into a geographic information system

and used with other data for analyses.

DOQ’s provide information about

soils, land use, and land cover, and

are useful as base maps for naturalresource inventories and mapping,

field-boundary delineation, and other

geoscience applications.

The USGS uses sonar-, satellite-, and

airborne-image data to identify and

monitor environmental problems on

the land and in coastal and interior

waterways. Satellite imagery and

DEM’s are being used to evaluate

ground-water resources in the Flagstaff area and to map wind erosion in

the southwestern United States. The

results of these and other projects can

be seen on the Web at http://

terraweb.wr.usgs.gov/TRS/

Information for Addressing United

States/Mexico Border Issues

USGS cartographers are working

with agencies and organizations in

the United States and Mexico to

create DOQ’s for a 100-mile zone on

each side of the border. DRG’s

already have been developed from

1:24,000-scale topographic maps of

the four States on the United States

side of the border—Texas, New

Mexico, Arizona, and California.

Furthermore, in cooperation with the

University of Arizona, USGS geologists are working on a digital

transboundary geologic map and

database. The area involved in this

project consists of a band about 155

miles wide along the entire 2,000-

mile border between the United

States and Mexico. The database is

intended to be used by scientists and

managers in joint United States/

Mexican activities that involve air

pollution, natural resources, urban

development, watershed analysis,

environmental health, emergency

response, and shared water resources.

Additional information about the

mapping project can be found at the

United States-Mexico Border Field

Coordinating Committee’s Web page

at http://www.doi.gov/fcc/

Yuma

San Die San Diegogogogo

Laredo

No El Paso Nogales gales g

Del Rio

TEXAS

CALIFORNIA

ARIZONA

NEW MEXICO

SONORA CHIHUAHUA

COAHUILA

100% Complete

Digital Elevation Model

Aerial Photography

Digital Raster Graphic

NUEVO

LEON TAMAULIPAS

Digital Orthophoto Quadrangle

30% Complete - 70% In progress

Digital Line Graph

PLSS 100% Complete

Boundary 100% Complete

Hydrography 18% Complete

Transportation 18% Complete

Hypsography 18% Complete

U.S. M a p p i n g S t a t u s

BAJA

CALIFORNIA

TAMAULIPAS

No ales

Figure 7. United States-Mexico transboundary mapping.