U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2007–3112

December 2007

FACING TOMORROW’S CHALLENGES: USGS SCIENCE IN THE DECADE 2007–2017

A Water Census of the United States

Printed on recycled paper

In 2007, the U.S. Geological Survey (USGS) developed a science strategy outlining 

the major natural science issues facing the Nation in the next decade. The science 

strategy consists of six science directions of critical importance, focusing on areas 

where natural science can make a substantial contribution to the well-being of the 

Nation and the world. This fact sheet focuses on the development of a water census 

of the United States, and how USGS research can strengthen the Nation with information needed to meet the challenges of the 21st century.

Importance of a Water Census

A fresh and dependable supply of 

water is critical to sustaining life and supports healthy communities, economies, 

and natural environments. Changing climate patterns will affect the availability 

of freshwater both locally and regionally. 

Many States expect future water shortages and are concerned about how the 

Federal Government could help them 

meet that challenge, yet no comprehensive census of water information for the 

Nation exists.

In the past, water needs were viewed 

primarily in relation to human activity. 

Now, however, the demand for water for 

environmental purposes is an important 

factor as well. Decisions about water that 

involve competing demands can lead to 

controversy and conflict, in part because 

available information is insufficient to 

resolve those disagreements. Therefore, it 

is essential to make scientifically rigorous 

determinations of environmental water 

needs and to provide reliable prediction 

capabilities relating ecosystem response 

to hydrologic conditions.

Because the availability of adequate 

quantities of suitable water is crucial to 

the Nation’s human population, economy, 

and environment, the USGS will conduct 

a Water Census of the United States to 

provide citizens, communities, naturalresource managers, and policymakers 

with a clear knowledge of the status of 

their water resources, data on trends in 

water availability and use over recent 

decades, and an improved ability to 

forecast the availability of freshwater for 

future human, economic, and environmental uses.

Why Action is Needed Now

As American population centers 

migrate to coastal areas and the arid west, 

water shortages will undoubtedly occur. 

In fact, ground-water levels in parts of 

the southwestern United States already 

have fallen so far as a result of pumping 

that many perennial streams, such as the 

Rio Grande, have at times ceased to flow. 

Cities that rely on ground water—for 

example, Tucson, Arizona—need to know 

how long pumping can be sustained. 

Conflicts over water are occurring within 

and among states, between states and the 

Federal government, and between environmentalists and government agencies. 

Tribal water rights are an additional concern, particularly in the western United 

States. Water availability conflicts also 

are likely to arise from future needs to 

develop energy or mineral resources and 

to meet the water-quality requirements of 

aquatic ecosystems. Fundamental data on 

the quantity and quality of the Nation’s 

freshwater resources, as well as spatial 

and temporal variations and trends, are 

needed to ensure that decisionmakers 

have access to complete, up-to-date, and 

reliable scientific information.

★ Ecosystems Climate Energy and Minerals Natural Hazards Environment and Human Health ★ ★ ★ ★ ★ ★ Water

SOURIS-RED-RAINY

UPPER

MISSISSIPPI

OHIO

MISSOURI

PACIFIC

NORTHWEST

GREAT BASIN

ARKANSAS-WHITE-RED

TEXAS-GULF

LOWER

COLORADO

RIO

GRANDE

UPPER

COLORADO

GREAT

LAKES

 LOWER MISSISSIPPI

SOUTH ATLANTIC-GULF

NEW ENGLAND

MID ATLANTIC

T E N N E S S E E

CALIFORNIA

ALASKA

HAWAIIAN

 ISLANDS

PUERTO RICO

The Water Census will focus on the 21 waterresources regions of the Nation, including their 

watersheds and associated aquifers. Waterresources regions along the coasts also include 

offshore freshwater aquifers.

Two current USGS projects, one in the Great 

Lakes Region and another on the Lower Colorado River in California, Nevada, and Arizona, 

could be used as pilot studies for the development of the Water Census. These pilot studies will demonstrate the best ways to evaluate freshwater resources and to deliver the 

information in a manner that is most helpful 

to planners and policymakers working at 

local, regional, and national levels.

The Water Census of the United States.
How the USGS Can Help

The USGS is the primary Federal 

agency responsible for scientific evaluation of the natural resources of the United 

States, including its water and biological 

resources. Many of its current programs 

provide the foundation upon which the 

Water Census of the United States can 

be built. The agency has a diverse cadre 

of scientists and technicians who work 

on aspects of the status and trends of 

freshwater quality and quantity for the 

Nation’s human and environmental needs 

at the local, State, regional, and national 

levels. The USGS also has an existing 

infrastructure from which it can conduct 

a regular inventory of natural resources 

and water use, including water quantity, quality, and environmental water 

needs, in partnership with local, State, 

and regional water and environmental 

agencies. The USGS has the skills needed 

to better define the geologic framework 

of aquifers, physical characteristics of 

watersheds, geochemical aspects of soil, 

land-cover change, land-use practices, 

and related environmental factors, all 

of which affect the movement of water 

and its quality. The USGS also has the 

biological capabilities needed to relate 

the presence of individual species, groups 

of species, and ecosystem function to 

the quantity, quality, and timing of water 

movement as well as environmental 

habitat requirements of those organisms. 

Its research on past climate variability 

enables the USGS to provide scientific 

understanding and modeling perspectives 

for expected changes in water availability due to ongoing climate fluctuations. 

USGS ground-water flow models are the 

international standard and, when coupled 

with watershed, water-quality, and ecosystem models, will enable decisionmakers to better predict the consequences of 

water- and land-use decisions.

Discharge measurement during drought conditions. A USGS streamgager measures 

discharge at North Fork Little Wind River near Fort Washakie, Wyoming, August 28, 2002. 

Photo by Jerrod Wheeler, U.S. Geological Survey.

USGS Science Can Meet the Challenge

The USGS is ready to take action by: 

•	 Defining the water needs of the Nation’s natural landscapes and changing environments, and relating the quantity, quality, and temporal variability of water to 

ecosystem structure and function.

•	 Expanding its capabilities for collection of data on the status of and trends in 

water quantity, quality, and use by humans and biota, and making the information available to decisionmakers and the public in increasingly useful, nationally 

consistent formats.

•	 Promulgating the systematic identification and mapping of changes in land cover 

and land use in the United States on a continuous basis and relating these changes 

to the availability of water resources for human and environmental needs.

•	 Documenting changes in the water-storage and -retention capabilities of aquifers 

and watersheds through the development and use of advanced technologies such 

as geophysics and remote sensing.

•	 Refining existing ground-water and watershed models and developing new 

modeling techniques that accurately characterize system interactions, identify 

uncertainties, and forecast changes in the hydrologic cycle to provide resource 

managers with improved tools for predicting the consequences of their management decisions.

•	 Designing and developing a Water Census of the United States in cooperation 

with local, State, regional, and other Federal agencies that provides these partners, policymakers, communities, and citizens with a regularly updated, nationally consistent inventory of the Nation’s freshwater resources.

A Vision For the Future

An enhanced, fully integrated, 

real-time data-collection network 

is supplemented by remote sensing, analyses and models based on 

long-term records, and improved 

water-use and -demand information. 

The USGS provides the Nation with 

a comprehensive view of the status of 

and trends in the quantity and quality 

of its freshwater supply to facilitate 

a flexible and informed response 

by water decisionmakers to a wide 

range of challenges and ensure that 

local, State, and regional water needs 

are met.

For Additional Information

U.S. Geological Survey, 2007, Facing 

Tomorrow’s Challenges—U.S. Geological Survey Science in the Decade 

2007–2017: Available online at http://

pubs.er.usgs.gov/usgspubs/cir/cir1309

Also, visit the USGS home page at

http://www.usgs.gov/