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National Water Census

USGS WaterSMART activities

USGS WaterSMART activities


Early History

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Water is a key ingredient for healthy communities, economies, and natural environments and as competition for water has grown over the past few decades, so too has the need for information and tools to aid water resource managers. The first systematic national effort to address that need came in 1968, when the U.S. Water Resources Council initially published a rudimentary national assessment (U.S. Water Resources Council, 1968). This was followed a decade later by a more comprehensive Second National Water Assessment (U.S. Water Resources Council, 1978). Later efforts to update components of the Second National Water Assessment to reflect conditions in the year 1995 were summarized in a 1999 Report titled National Assessment of the Potential Consequences of Climate Variability and Change (Frederick and Schwarz, 1999).

At the time of these early national assessments, water availability was viewed in comparatively simple terms, and the reports focused largely on basic statistics about the quantities of water available for various human uses. Since then, competition for water resources has increased considerably and greater importance is attached to water for environmental and ecosystem needs, in addition to human use. Likewise, concerns have grown about groundwater depletion, streamflow alteration, climate change and variability, and water-quality impairment. There is also much greater awareness of the connectivity of surface water and groundwater and the linkages between water availability and use of other natural resources.

By 2002, however, there was a growing recognition of the value of assessing the nation's water supplies through a more comprehensive, programmatic approach. The House Committee on Appropriations directed the USGS to "prepare a report describing the scope and magnitude of the efforts needed to provide periodic assessments of the status and trends in the availability and use of freshwater resources" as part of its report on Fiscal Year 2002 Appropriations for Interior and Related Agencies. To prepare that report, the USGS solicited input from many individuals and organizations involved in issues of water availability and use, asking what types of decisions and policy issues needed improved water facts, what variables or indicators would be useful, and what spatial and temporal scales would be appropriate. The design of the Water Census built upon these comments and recommendations, which were summarized in a 2002 USGS report entitled Concepts for National Assessment of Water Availability and Use, Circular 1223.

The 2002 circular outlined a broad framework by which a national assessment could take place and advocated using 21 Water Resources Regions for the study units. The report noted several clear messages from the responses, including the potential for improved methodologies and standards for consistency of nationwide data, the importance of ecological flows as a component of water use and availability, and the connections between water quantity and water quality. In addition, the report examined how to best build on existing efforts and where to expand collaborative opportunities. National organizations noted the need for consistent indicators of water availability across the Nation, while individuals representing State and local governments emphasized that many States have done extensive planning to quantify water availability now and in the future, and that the availability of water is inherently a local issue in most respects.

In 2003, the U.S. General Accounting Office highlighted the need for an updated assessment of national water supplies, noting that "National water availability and use has not been comprehensively assessed in more than thirty years." Shortly thereafter, the National Science and Technology Council, Committee on Environment and Natural Resources through the Subcommittee on Water Availability and Quality (SWAQ) also issued their own report calling attention to the need for a comprehensive approach to assessing the Nation's water availability (National Science and Technology Council, 2004).

Pilot Studies

In 2005, upon the request of Congress, USGS initiated a National Water Availability and Use Pilot Study to explore methods of quantifying the source, movement, and dynamics of water resources. The U.S. portion of the Great Lakes Basin was chosen as the location for the initial pilot area study, and USGS scientists used the opportunity to develop new methods of hydrologic analysis while also examining how best to integrate data and provide information on water availability at such a large scale (Reeves, 2010). A series of studies were selected at different spatial and temporal scales that would allow scientists to assess the overall question of regional availability while also evaluating local variation in availability to examine the potential for local shortages of water and the evaluate uncertainties associated with the regional-scale assessments. Regional studies looked at largest scale, probing questions about groundwater storage, base flow and recharge, and trends in precipitation and streamflow over time across the U.S. portion of the Great Lakes. A series of subregional studies focused on particular aspects of the water resource systems that would be difficult to assess at the regional scale. This included a Lake Michigan groundwater flow model and estimation of streamflows at ungaged locations, as well as water withdrawals and returns. Local studies focused on localized questions, including an 'inset' model developed for a portion of the Lake Michigan groundwater flow model that simulated groundwater-surface water interactions, examining how different groundwater pumping scenarios would affect streamflow. The multi-scale approach enabled an integrated understanding of water resource availability and the effects of human uses, climate variability, and land use change.

In 2006, scientists at USGS began a second small pilot study, focused on groundwater availability in the lower Colorado River basin (Tillman and others, 2011). The purpose was to develop methods for assessing water availability in a region that was both groundwater dominated and had arid or semi-arid conditions. The project enabled USGS scientists to develop new methods and indicators for assessment and presentation of regional groundwater conditions. In addition, the pilot looked at groundwater budgets for a series of alluvial basins in Southwest Arizona, providing new estimates of groundwater budget components using recent (2000-2007) data and methods of data analysis. It also provided up-to-date estimates of inflow components of the water budget, important for water budgeting as well as analyzing trends in groundwater over time. These included mountain-front recharge, incidental recharge from irrigation of agriculture, managed recharge from recharge facilities, interbasin underflow from upgradient basins, and streamflow losses. The final aspect of the pilot study was a "proof-of-concept" multi-basin groundwater flow model to test the integration components of the water budgets created in the study and verify that the large, multi-basin models could be integrated.

The SECURE Water Act

In 2007, the National Science and Technology Council (NSTC) released a report entitled "A Strategy for Federal Science and Technology to Support Water Availability and Quality in the United States." The report noted the need for a "census" approach to assessing nationwide water supplies, stating: "The United States has a strong need for an ongoing census of water that describes the status of our Nation's water resource at any point in time and identifies trends over time." In its simplest terms the philosophy was "You can't manage what you don't measure," and therefore knowledge of the nation's water "assets" and rates of use on an ongoing basis was crucial for wise management.

That same year, USGS released a forward-looking report that considered the agency's strategy for addressing national science priorities titled Facing Tomorrow's Challenges – U.S. Geological Survey Science in the Decade 2007-2017 Circular 1309. The strategy identified "A Water Census of the United States: Quantifying, Forecasting, and Securing Freshwater for America's Future" as one of the major strategic directions for the USGS. As the primary Federal agency responsible for scientific evaluation of the natural resources of the United States, it made sense for USGS to play a key role in national assessment of water availability and its use. The agency has a diverse cadre of scientists and technicians and 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 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.

On March 30, 2009, U.S. Congress created the national framework for a programmatic approach to water availability and use with the passage of the Omnibus Public Land Management Act of 2009 (Public Law 111–11) Subtitle F – SECURE Water. Also known as the SECURE Water Act, it contains substantive mandates for both the U.S. Geological Survey (USGS) and the U.S. Bureau of Reclamation. Section 9508 of the SECURE Water Act establishes a "national water availability and use assessment program" within the USGS – this is the research program known as the National Water Census, or simply the Water Census. In accordance with the provisions in the Act, the programmatic goals are to:

  • provide a more accurate assessment of the status of the water resources of the United States;
  • assist in the determination of the quantity of water that is available for beneficial uses;
  • assist in the determination of the quality of the water resources of the United States;
  • identify long-term trends in water availability;
  • use each long-term trend to provide a more accurate assessment of the change in the availability of water in the United States; and
  • develop the basis for an improved ability to forecast the availability of water for future economic, energy production, and environmental uses.

Report Requested in SECURE Water Act (P.L. 111-11)

Not later than December 31, 2012, and every 5 years thereafter, the Secretary shall submit to
the appropriate committees of Congress a report that provides a detailed assessment of—
    (1) the current availability of water resources in the United States, including—
         (A) historic trends and annual updates of river basin inflows and outflows;
         (B) surface water storage;
         (C) groundwater reserves; and
         (D) estimates of undeveloped potential resources
              (including saline and brackish water and wastewater);
    (2) significant trends affecting water availability, including each documented or projected
         impact to the availability of water as a result of global climate change;
    (3) the withdrawal and use of surface water and groundwater by various sectors, including—
         (A) the agricultural sector;
         (B) municipalities;
         (C) the industrial sector;
         (D) thermoelectric power generators; and
         (E) hydroelectric power generators;
    (4) significant trends relating to each water use sector, including significant changes in water
         use due to the development of new energy supplies;
    (5) significant water use conflicts or shortages that have occurred or are occurring; and
    (6) each factor that has caused, or is causing, a conflict or shortage described in paragraph (5).

WaterSMART Initiative

The Department of the Interior implemented the SECURE Water Act by launching an initiative in February 2010 known as WaterSMART (Sustain and Manage America's Resources for Tomorrow). WaterSMART harnesses the expertise of two DOI agencies, the Bureau of Reclamation and the U.S. Geological Survey (USGS) to address water resource challenges facing the Nation. USGS WaterSMART goals included:

  • Bring existing plans and legislative mandates together in one strategy.
  • Integrate existing science efforts across the Department of the Interior to focus resources on water availability questions.
  • Set forth a strategy to answer the questions:
    • Does the Nation have an adequate quantity of water, with sufficient quality and timing-characteristics, to meet both human and ecological needs?
    • Will this water be present to meet both existing and future needs?

WaterSMART enabled USGS to begin creating a new research program known as the Water Census which had been sketched out in the 2007 ten-year science strategy by providing a mechanism that allowed USGS to integrate research activities and reach out to stakeholder to identify their information needs. WaterSMART identified three geographic Focus Areas that could benefit from cutting edge approaches to assessing water availability while also serving as pilot studies where multiple lines of research could be integrated and designed to meet stakeholder's information needs. Each Focus Area offered unique challenges that USGS could investigate at the scale of a large river basin. USGS began working with stakeholders to identify their information needs and provide research outputs – such as data and reports – in formats that would be useful to those who were ultimately making resource management decisions at various levels, including state and local agencies.

Ultimately, the two pilot studies contributed to USGS understanding of the technical issues that needed to be addressed to boost national capacity to assess water availability and use. The report on the Great Lakes pilot was released in 2010 and the Arizona Alluvial Basins study report was released in 2011. Lessons learned from these two studies proved valuable to identifying programmatic research needs. For information on the Water Census program's current emphasis and activities, visit the Program Overview page.


Frederick, K.D., and Schwarz, G.E., 1999, Socioeconomic impacts of climate change on U.S. water supplies: Journal of the American Water Resources Association, v. 35, no. 6, p. 1563-1583.

Reeves, H.W., 2010, Water Availability and Use Pilot – A multiscale assessment in the U.S. Great Lakes Basin: U.S. Geological Survey Professional Paper 1778, 105 p.

Tillman, F.D., Cordova, J.T., Leake, S.A., Thomas, B.E., and Callegary, J.B., 2011, Water availability and use pilot: Methods development for a regional assessment of groundwater availability, Southwest Alluvial basins, Arizona: U.S. Geological Survey Scientific Investigations Report 2011-5071.

U.S. Department of the Interior, 2012, WaterSMART: A three-year progress report.

U.S. Geological Survey, 2002, Report to Congress: Concepts for national assessment of water availability and use: U.S. Geological Survey Circular 1223, 34 p.

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.

U.S. Water Resources Council, 1968, The Nation's water resources: Washington, DC, U.S. Government Printing Office.

1978, The Nation's water resources 1975-2000, Second National Water Assessment: Washington, DC, U.S. Government Printing Office.

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