Progress Toward a National Water Census

Increasing demand and competition for limited regional 

water resources make it difficult to ensure adequate water availability for both human and ecological needs now and into the 

future. Recognizing the need to improve the tools and information that are available to effectively evaluate water-resource 

availability, the U.S. Geological Survey (USGS) identified a 

National Water Census (NWC) as one of its six core science 

directions for the decade 2007–17 (U.S. Geological Survey, 

2007). In 2009, the SECURE Water Act (Public Law 111–11) 

authorized the USGS to develop a national water availability 

and use assessment program that would update the most recent 

national assessment of the status of water resources in the 

United States (U.S. Water Resources Council, 1968, 1978) 

as well as develop the science to improve forecasts of water 

availability and quality for future needs. 

By evaluating large-scale effects of changes in land use 

and land cover, water use, and climate on occurrence and 

distribution of water, water quality, and human and aquaticecosystem health, the NWC will also help to inform a broader 

initiative by the Department of the Interior, WaterSMART 

(Sustain and Manage America’s Resources for Tomorrow), 

which provides multiagency funding to pursue a sustainable 

water supply for the Nation as directed under the SECURE 

Water Act. Through the NWC, the USGS actively engages 

Federal, regional, and local stakeholders to identify research 

priorities and leverages current studies and program activities 

to provide information that is relevant at both the national and 

regional scales.

The NWC will produce a current, comprehensive scientific 

assessment of the factors that influence water availability by 

(1) developing nationally consistent datasets that reflect the 

status and trends of major water budget components (diagram 

below), as well as water use, for the Nation; (2) improving 

the current understanding of flow requirements for ecological 

purposes; and (3) evaluating water-resource conditions in 

selected river basins, or Geographic Focus Areas, where 

competition for water is elevated. Future research goals of the 

NWC include (1) evaluating the relations between water supply 

and quality for both human and ecological uses, including the 

potential use of impaired water supplies; (2) development of 

Geographic Focus Area studies in additional basins; and (3) the 

continued improvement of uncertainty analysis.

Much of the information developed as part of the NWC is 

derived from models, statistical estimation techniques, and other 

transformation processes. The National Water Census Data 

Portal has been developed to allow users to access a comprehensive and nationally consistent interactive map interface 

to download data visualizations, retrieve stand-alone data for 

further analysis, or integrate multiple datasets with built-in and 

downloadable data-analysis tools.

Precipitation

Surface-water inflow,

imported water

(pipelines, canals)

Groundwater

inflow

Surface-water outflow,

exported water

(pipelines, canals)

Groundwater outflow

Aquifer

Evapotranspiration

Bedrock

Water table

Unsaturated zone

Components of a simple 

water budget for part of a watershed 

(modified from Healy and others, 2007).

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2015–3045

June 2015
Developing a National Water Budget

Data and other information produced as part of the NWC can 

be used to define the components of a water budget; unfortunately, 

consistent data for many water-budget components are not 

currently available either regionally or nationally. The unifying 

goal of the NWC is to develop and improve estimates of waterbudget components at consistent spatial (basin) and temporal 

(monthly) scales. This goal will be achieved through a series of 

topical area studies that are designed to quantify the amount of 

water that resides in, or is moving through, water budgets. 

Topical Areas

As part of the NWC, the USGS will conduct studies that 

focus on streamflow, groundwater, precipitation, evapotranspiration, and water use to develop and improve the data needed 

to achieve a comprehensive and up-to-date assessment of 

water availability at both national and basin scales. An additional topical area study will advance the science of ecological 

flow by quantitatively examining the relations between water 

availability and healthy ecosystems.

Each topical area study seeks to enhance available data and 

associated information through the research and development 

of new methodologies, improving data accessibility, and quantifying and reducing data uncertainty. In addition to providing 

a basis for national indicators of water flow and storage for the 

NWC, these studies will support analyses of water availability 

by local and regional agencies and will contribute to research 

quantifying national and global water cycles.

Geographic Focus Area Studies

Competition for water resources is focused regionally 

where competing water needs — either human needs (for 

example, potable water, irrigation, energy development, 

industrial use) or flow requirements for healthy ecosystems—

are outpacing current supplies. As a counterpart to the topical 

area studies, a series of Geographic Focus Area studies, or 

regional assessments, will provide opportunities to test and 

improve approaches for quantifying water-budget components 

and pilot the application of regional water budgets to the watermanagement challenges of large river basins. These studies 

will also provide an opportunity to inform and “ground truth” 

NWC methods and applications with local information.

The first three Geographic Focus Area studies are 

underway in the Apalachicola–Chattahoochee–Flint, Colorado, 

and Delaware River Basins (map upper right); specific basin 

research and products include: water-use databases that estimate 

current and historical trends, including consumptive use; 

developing a tool to estimate streamflow at ungaged streams 

and coupling surface- and groundwater flow models; and 

developing decision support systems and ecological models 

to predict changes in fish and mussel species associated with 

climate and land-use change and water use.

Three new Focus Area studies will begin in October 2015 

in the Red River and Rio Grande Basins, and the Coastal Basins 

of the Carolinas. Planned research includes impacts of dust on 

snow, refinement and coupling of groundwater and surfacewater models, and development of methods to evaluate 

agricultural irrigation.

References

Healy, R.W., Winter, T.C., LaBaugh, J.W., and Franke, O.L., 

2007, Water budgets—Foundations for effective waterresources and environmental management: U.S. Geological 

Survey Circular 1308, 90 p., available at http://pubs.usgs.gov/

circ/2007/1308/.

U.S. Geological Survey, 2007, Facing tomorrow’s challenges—

U.S. Geological Survey science in the decade 2007–2017: 

U.S. Geological Survey Circular 1309, 70 p., available online 

at http://pubs.usgs.gov/circ/2007/1309/. 

U.S. Water Resources Council, 1968, The Nation’s water 

resources: Washington, D.C., U.S. Government Printing 

Office, 480 p.

U.S. Water Resources Council, 1978, The Nation’s water 

resources 1975–2000—Second National Water Assessment: 

Washington, D.C., U.S. Government Printing Office, 768 p. 

Additional Information and Contacts 

Detailed information about the current status and 

activities of the National Water Census can be found in 

U.S. Geological Survey Circular 1384, “Progress Toward 

Establishing a National Assessment of Water Availability 

and Use.” This publication is available online at http://pubs.

usgs.gov/circ/1384/. For additional information, please visit 

http://water.usgs.gov/watercensus/ or contact:

Sonya Jones, Program Coordinator

National Water Availability and Use Science Program

U.S. Geological Survey

1770 Corporate Drive, Suite 500

Norcross, GA 30093

Phone: 678-924-6606

E-mail: sajones@usgs.gov

Eric J. Evenson, Program Office

Water Mission Area

U.S. Geological Survey

3450 Princeton Pike, Suite 110

Lawrenceville, NJ 08648

Phone: 609-771-3904

E-mail: eevenson@usgs.gov

ISSN 2327-6932 (online)

http://dx.doi.org/10.3133/fs20153045

LA

ID

OR

NV

CA

NM

TX

UT

AZ

NE

MT ND

WY

CO

OK

KS

SD

AR

MO

GA

FL

IA

AL

TN

MS

NC

WI MI

MN

IL IN

KY

SC

OH

WV VA MD

DE

ME

NY

PA NJ

RI

WA

NH

MA

VT

CT

Colorado

River Basin

Red River

Basin

Upper

Rio Grande

Basin

Coastal Basins

of the Carolinas

Apalachicola–

Chattahoochee–

Flint River Basin

Delaware

River Basin