Cover. The Rio Grande River and Santa Elena Canyon at Big Bend National Park, Texas. Photo by Alan Cressler, U.S. Geological Survey.

Report to Congress—

Continuing Progress Toward a National Assessment 

of Water Availability and Use

Circular 1440

U.S. Department of the Interior

U.S. Geological Survey
High

Plains

Colorado

River Basin

Upper Rio

Grande Basin

Red River

Basin

Delaware

River Basin

Coastal Basins

of the Carolinas

Apalachicola–Chattahoochee–

Flint River Basin

G l a c i a l

G l a c i a l

Northwest

Volcanic

California

Coastal Basins

Coastal

Lowlands

Hawaii

Volcanic

Transboundary

Colorado

Plateaus

Central

Valley

Mississippi

Alluvial Plain

Appalachian

Plateaus

Ozark

Plateaus

Williston/

Powder River

Floridan

U.S. Geological Survey—Water Availability and Use Program

EXPLANATION

Ongoing studies

Geographic Focus Area studies

Regional Groundwater Availability studies

Estimated

Streamflow

National

Groundwater

Monitoring

Network

Drought

Science

Brackish

Groundwater

Assessment

Ecological

Water

Science

Water

Use

Evapotranspiration

Science

Groundwater

Availability

Tools

ONGOING NATIONWIDE STUDIES
Report to Congress—

Continuing Progress Toward a National 

Assessment of Water Availability and Use

By Eric J. Evenson, Sonya A. Jones, Nancy L. Barber, Paul M. Barlow, 

David L. Blodgett, Breton W. Bruce, Kyle Douglas-Mankin, William H. Farmer, 

Jeffrey M. Fischer, William B. Hughes, Jonathan G. Kennen, Julie E. Kiang, 

Molly A. Maupin, Howard W. Reeves, Gabriel B. Senay, Jennifer S. Stanton, 

Chad R. Wagner, and Jennifer T. Wilson

Circular 1440

U.S. Department of the Interior

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

RYAN K. ZINKE, Secretary

U.S. Geological Survey

James F. Reilly II, Director

U.S. Geological Survey, Reston, Virginia: 2018

For more information on the USGS—the Federal source for science about the Earth, its natural and living 

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Suggested citation: 

Evenson, E.J., Jones, S.A., Barber, N.L., Barlow, P.M., Blodgett, D.L., Bruce, B.W., Douglas-Mankin, K., Farmer, W.H., 

Fischer, J.M., Hughes, W.B., Kennen, J.G., Kiang, J.E., Maupin, M.A., Reeves, H.W., Senay, G.B., Stanton, J.S., 

Wagner, C.R., and Wilson, J.T., 2018, Continuing progress toward a national assessment of water availability 

and use: U.S. Geological Survey Circular 1440, 64 p., https://doi.org/10.3133/cir1440.

ISSN 1067-084X (print) 

ISSN 2330-5703 (online)

ISBN 978-1-4113-4229-3
iii

About This Report

This report is the second in a series of reports to the U.S. Congress on the progress toward a 

National Assessment of Water Availability and Use (also known as the USGS National Water 

Census). These reports are required by the SECURE Water Act (P.L. 111-11, Section 9508 (d)) 

(42 USC 10368). The first report, “Progress toward establishing a national assessment of water 

availability and use, U.S. Geological Survey Circular 1384” (Alley and others, 2013), was delivered in March 2013. It described the initial steps taken by the U.S. Geological Survey (USGS) 

toward accomplishing a national census of water resources. The USGS National Water Census 

(the Water Census) is designed to systematically provide information that will allow resource 

managers to assess the supply, use, and availability of the Nation’s water. This second report 

explains how the Water Census has progressed toward this goal from 2013 to 2017. This report 

describes the critical work that is underway to understand, assess, and deliver information 

about water availability, as well as the collaboration and coordination with other agencies and 

organizations that are essential for the Water Census to succeed. This report describes the 

on-going regional framework for presenting water-availability data through a set of geographic 

focus area studies and regional groundwater assessments, and the national framework for 

providing uniform information on water-budget components across the country through targeted 

topical studies. This report also documents the information management and delivery activities 

that are being conducted as part of the Water Census. Finally, this report describes the initiatives that are planned as part of the Water Census for the next 5 years.
iv

Acknowledgments

The following individuals provided helpful reviews of the draft report: Melinda Dalton and 

Patrick Lambert, U.S. Geological Survey; and Avra Morgan, Bureau of Reclamation. 
v

Contents

About This Report .........................................................................................................................................iii

Acknowledgments........................................................................................................................................iv

Executive Summary.......................................................................................................................................1

Introduction.....................................................................................................................................................1

Summary of the SECURE Water Act..................................................................................................1

Role of Other Federal Agencies in Studies of Water Availability and Use..................................3

U.S. Bureau of Reclamation.......................................................................................................3

National Oceanic and Atmospheric Administration ..............................................................3

U.S. Environmental Protection Agency....................................................................................3

National Water Census.................................................................................................................................4

Water Budgets as a Unifying Theme.................................................................................................4

Characterizing Uncertainty .................................................................................................................5

Coordination and Collaboration..........................................................................................................7

Programmatic Resources....................................................................................................................7

Geographic Focus Area Studies .................................................................................................................8

Apalachicola-Chattahoochee-Flint River Basin (2011–15) ............................................................8

Synoptic Effort..............................................................................................................................8

Water-Use Component................................................................................................................8

Simulating Surface-Water and Groundwater Flow..............................................................10

Environmental Water Component...........................................................................................10

Colorado River Basin (2011–15)........................................................................................................11

Water-Use Component..............................................................................................................11

Groundwater and Base-Flow Component .............................................................................11

Snow Pack and Sublimation Component...............................................................................13

Delaware River Basin (2011–15).......................................................................................................13

Improved Water-Use and Water-Supply Information..........................................................13

Basin Hydrologic Model ...........................................................................................................15

Environmental Water Science on Mainstem ........................................................................15

Environmental Water Science on Tributaries .......................................................................15

Coastal Carolinas Basins (2015–19).................................................................................................15

Red River Basin (2015–19) .................................................................................................................19

Upper Rio Grande Basin (2015–19) ..................................................................................................19

Topical Studies .............................................................................................................................................23

Surface Water.....................................................................................................................................23

Flow at Ungaged Locations......................................................................................................23

Analysis of Change in Streamflow..........................................................................................25

Groundwater........................................................................................................................................25

Regional Groundwater Evaluations ........................................................................................25

Composite Hydrographs ...........................................................................................................28

Tools for Groundwater Availability—Model Sustainability ................................................32

Increasing Access to Groundwater Information..................................................................32

National Groundwater Monitoring Network .........................................................................34

Brackish Groundwater..............................................................................................................34
vi

Evapotranspiration..............................................................................................................................35

Water Use ............................................................................................................................................36

Water-Use Compilation 2015....................................................................................................37

Water-Use Data and Research Program...............................................................................37

Thermoelectric Water Use.......................................................................................................38

Water Use by Principal Aquifer, 2015 .....................................................................................40

wateRuse R Programming Tools .............................................................................................40

Irrigation Consumptive Use......................................................................................................40

Water Use Research Funded by Cooperative Matching Funds ........................................41

Improving the Scale of Water-Use Information....................................................................41

Release of Pre-1985 Data and Statewide Totals...................................................................42

Water-Use Science Training....................................................................................................42

Draft Water-Use Science Strategy.........................................................................................42

Environmental Water Science..........................................................................................................43

Serving Hydrologic and Ecological Information...................................................................43

Calculation of Streamflow Metrics.........................................................................................43

National Classification of Streams .........................................................................................44

Aggregating Ecological Data from Multiple Agency Sources ...........................................45

Drought Science .................................................................................................................................45

Delivering the Data......................................................................................................................................47

Data Integration and Mapping .........................................................................................................47

The National Data Platform...............................................................................................................47

Planning for the Future................................................................................................................................49

Future Geographic Focus Area Studies..........................................................................................49

Modeling Approach............................................................................................................................49

Future Databases Needed ................................................................................................................50

References Cited..........................................................................................................................................51

Appendix 1. Geographic Focus Area Study Publications.................................................................59

Appendix 2. Regional Groundwater Availability Study Publications ...............................................61
vii

Figures

1. Schematic diagram of the components of the water budget ...............................................5

2. Example streamflow hydrograph with uncertainty intervals ................................................6

3. Map showing location of the Apalachicola-Chattahoochee-Flint River Basin..................9

4. Map showing location of the Colorado River Basin, within the United States ................12

5. Map showing location of the Delaware River Basin............................................................14

6. Map showing location of the Coastal Carolina Basins Focus Area Study .......................17

7. Screen capture of U.S. Geological Survey Coastal Carolina Basins Focus Area 

Study webpage ...........................................................................................................................18

8. Map showing location of the Red River Basin.......................................................................19

9. Screen capture of U.S. Geological Survey Red River Basin Focus Area 

Study webpage ...........................................................................................................................20

10. Map showing location of the Upper Rio Grande River Basin .............................................21

11. Screen capture of U.S. Geological Survey Upper Rio Grande River Basin Focus 

Area Study webpage..................................................................................................................22

12. Schematic diagram of the U.S. Geological Survey Precipitation Runoff Modeling 

System..........................................................................................................................................23

13. Diagram showing U.S. Geological Survey National Hydrologic Model-Precipitation 

Runoff Modeling System simulated streamflow for June 1, 2010 using the default 

parameters and model setup described in Regan and others, 2018 and Driscoll 

and others, 2017 ..........................................................................................................................24

14. Map showing Northern Atlantic Coastal Plain aquifer system cumulative 

groundwater withdrawals and storage depletion as percentage of total water 

withdrawn and percentage of total groundwater depletion from 1900 to 2013 ...............26

15. Graphs showing time series of annual values of base flow and runoff at U.S. 

Geological Survey streamgaging stations A, 03051000 Tygart Valley River 

at Belington, W.Va.; B, 03208500 Russell Fork at Haysi, Va.; and C, 03118500 

Nimishillen Creek at North Industry, Ohio ..............................................................................27

16. Map showing geographic distribution of trends in mean annual groundwater 

levels, 1984–2013 with the assumption of data independence...........................................28

17. Composite hydrograph and associated hydrologic information for the North 

Atlantic Coastal Plain principal aquifer, 1940–2010 ..............................................................29

18. Composite hydrograph and associated hydrologic information for the Coastal 

Lowlands principal aquifer, 1975–2015....................................................................................30

19. Composite hydrograph and associated hydrologic information for the California 

Coastal Basins principal aquifer for the period 1985–2015..................................................30

20. Map showing preliminary long-term average groundwater-recharge rates 

estimated for the glacial aquifers of the United States by use of the U.S. Geological 

Survey Soil-Water-Balance model as part of the USGS Glacial Aquifers 

Groundwater-Availability Study ...............................................................................................33

21. Screen capture showing sites in New York State for which borehole-geophysical 

logs are available through the U.S. Geological Survey GeoLog Locator ..........................33

22. Screen capture showing seasonal cumulative evapotranspiration anomaly 

for the conterminous United States, April 1–October 30, 2016 ...........................................36

23. Graphic showing states that received funds from the Water Use Data and 

Research Program to describe current water use and identify priorities 

for improving water-use data in their state............................................................................38
viii

24. Graphic showing states that were awarded funds from the Water Use Data 

and Research 2016 Competitive Program to improve water-use data and research 

in their state.................................................................................................................................39

25. Graphic showing states that were awarded funds from the Water Use Data 

and Research 2017 Competitive Program to improve water-use data and research 

in their state.................................................................................................................................39

26. Graphic showing hydroecological classification of 1,543 U.S. Geological Survey 

streamgages across the conterminous United States.........................................................44

27. Map showing aquatic invertebrate sampling locations aggregated from nine 

agency sources in the Delaware River Basin........................................................................46

28. Screen capture of an accumulated water budget for a watershed in Wisconsin 

showing precipitation, streamflow, and evapotranspiration...............................................48
Continuing Progress Toward a National Assessment 

of Water Availability and Use

By Eric J. Evenson, Sonya A. Jones, Nancy L. Barber, Paul M. Barlow, David L. Blodgett, Breton W. Bruce, 

Kyle Douglas-Mankin, William H. Farmer, Jeffrey M. Fischer, William B. Hughes, Jonathan G. Kennen, Julie 

E. Kiang, Molly A. Maupin, Howard W. Reeves, Gabriel B. Senay, Jennifer S. Stanton, Chad R. Wagner, and 

Jennifer T. Wilson

Executive Summary

The Omnibus Public Land Management Act of 2009 

(Public Law 111–11) was passed into law on March 30, 2009. 

Subtitle F, also known as the SECURE Water Act, calls for the 

establishment of a “national water availability and use assessment program” within the U.S. Geological Survey (USGS). 

The USGS issued the first report on the program in 2013. 

Program progress over the period 2013–17 is reported herein 

to fulfill the requirement to inform Congress on implementation of the national water availability and use assessment 

program, also referred to as the USGS National Water Census 

(the Water Census).

Much work has been accomplished during 2013–17 on 

producing water budgets for the nation, a goal USGS outlined in its first report on program progress to Congress. The 

USGS has completed three geographic focus area studies and 

has begun three others. Work has advanced on nationwide 

efforts in streamflow analysis, groundwater assessment and 

research, evapotranspiration studies, water use, environmental 

water science, and drought science (inside front cover). The 

USGS works with Federal and non-Federal agencies, universities, and other organizations to ensure that the information 

can be aggregated with other types of water-availability and 

socioeconomic information, such as data on food and energy 

production. The USGS has also made great strides in measures 

for delivering data and information on the Water Census to 

stakeholders and the public.

Much work remains to be accomplished for the Nation to 

have a comprehensive, ongoing Water Census. In this report, 

the USGS lays out activities to be accomplished in the next 

5 years (2017–22), based upon current funding levels. These 

include selecting new focus area studies, conducting hydrologic modeling to complete water budgets for the conterminous United States, expanding groundwater modeling efforts, 

mapping a national classification system for environmental 

water science, and developing an inventory of interbasin water 

transfers. All of these steps are necessary in order for the 

Water Census to achieve the goals outlined by Congress in the 

SECURE Water Act.

Introduction

Water has never been of greater importance to the health 

of our Nation, to its economies, and to the natural environment. As the United States population increases to more than 

325 million, our Nation faces a growing set of water-resource 

challenges resulting from increased demand, fluctuations in 

supply, and intensified competition for limited resources. The 

Nation has added 10 million people to its population in the 

time frame of this report, 2013–17 (https://www.census.gov/

popclock/). In the face of these challenges, the need for more 

sophisticated information and tools to aid water-resource 

managers has increased as well. The U.S. Geological Survey 

(USGS) Water Census was created to meet that need. This 

report informs the reader of the progress that has been made 

over the last 5 years to advance our knowledge of water availability and use through improved methods of information 

analysis and delivery.

Summary of the SECURE Water Act

Subtitle F of the Omnibus Public Land Management Act 

of 2009 (Public Law (P.L.) 111-11), which was passed into law 

on March 30, 2009, helps address the Nation’s need for water 

availability and use information. Also known as the SECURE 

Water Act, it contains substantive mandates for both the USGS 

and the Bureau of Reclamation (Reclamation). 

Section 9508 of the SECURE Water Act calls for the 

establishment of a “national water availability and use assessment program” within the USGS 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; 
2 Continuing Progress Toward a National Assessment of Water Availability and Use

• 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, energyproduction, and environmental uses. 

The national water availability and use assessment 

program called for by the SECURE Water Act also is referred 

to as the Water Census. It is one of six major science directions identified by the USGS in 2007 in its Science Plan for 

the next decade (U.S. Geological Survey, 2007). Additionally, 

in 2016, the USGS initiated the Water Availability and Use 

Science Program (WAUSP) and combined all of its activities that are directly related to water availability and use 

in that one programmatic line item. This action was taken 

for the most part to accomplish the task set for the USGS 

by the U.S. Congress under Section 9508 of the SECURE 

Water Act.

Included in the SECURE Water Act is a requirement 

to report to Congress every five years on progress made in 

implementing the national water availability and use assessment program (see Box A). This report summarizes progress 

for the second 5-year period.

Box A. 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).

Shoal Lillies (Hymenocallis coronaria), Anthony Shoals, Broad River, Lower Broad 

River Wildlife Management Area, Wilkes County, Georgia. Photograph by Alan 

Cressler, U.S. Geological Survey
Introduction 3

Role of Other Federal Agencies in Studies of 

Water Availability and Use

The USGS works with a number of other Federal agencies on the issues of water availability and use. This collaboration is an extremely important part of serving the Nation’s 

need for water availability and use information. In September 

2007, the Subcommittee on Water Availability and Quality (at 

the time, a part of the Committee on Environment and Natural 

Resources within the U.S. Office of Science and Technology Policy [https://www.whitehouse.gov/ostp]) published 

“A Strategy for Federal Science and Technology to Support 

Water Availability and Quality in the United States” (National 

Science and Technology Council, 2007). Appendix I of that 

strategy identified 18 Federal agencies, at the bureau/service/

authority level, that play an important role in assessing water 

availability for the Nation. Some of these agencies are major 

water-resource managers and purveyors of water, such as the 

U.S. Army Corps of Engineers, the Bureau of Reclamation, 

and the Tennessee Valley Authority. Some of these agencies, 

such as the U.S. Department of Energy, the U.S. Environmental Protection Agency (EPA), and the U.S. Army Corps 

of Engineers, fill a regulatory role. Others, such as the U.S. 

National Park Service, the U.S. Fish and Wildlife Service, 

and the U.S. Forest Service, are land-management agencies also serving as stewards of the water on that land. Still 

others, such as the USDA Agricultural Research Service, the 

National Oceanic and Atmospheric Administration (NOAA), 

the National Aeronautics and Space Administration, and the 

National Science Foundation, are agencies with a science mission complementary to that of the USGS. This report provides 

a detailed description of the water availability work done by 

three of these agencies and their ongoing collaborations with 

the USGS.

Bureau of Reclamation

Both the USGS and Reclamation have substantive 

responsibilities under the Department of the Interior WaterSMART initiative. The primary USGS WaterSMART activity 

is the Water Census. WaterSMART activities in Reclamation include the River Basin Supply and Demand Studies; 

the WaterSMART Grants Program, which concentrates on 

water conservation and sustainability grants; and the Title 

XVI Program, which concentrates on water recycling and 

reuse projects. WaterSMART activities under the Department 

of the Interior require close coordination between these two 

agencies. There is a natural synergy between the Reclamation’s River Basin Supply and Demand Studies and the USGS 

Geographic Focus Area Studies, which are described later in 

this report. The USGS and Reclamation have been active participants in the planning and execution of the studies that are 

of joint interest. This joint interest is directly apparent in the 

Colorado River Basin studies—the USGS Geographic Focus 

Area Study of the Colorado River Basin was designed to fulfill 

data needs identified during the execution of the Bureau of 

Reclamation River Basin Supply and Demand Study of the 

Colorado River. Other studies of interest to both agencies are 

being conducted on the Red River (of the south) Basin and 

the Upper Rio Grande River Basin; studies are discussed later 

in this report. Reclamation has been an active participant in 

the evaluation and selection of USGS Geographic Focus Area 

Studies and in the evaluation and ranking of Water Use Data 

and Research Cooperative Agreements. The collaboration 

between the USGS and Reclamation on WaterSMART is a 

model for Federal agencies working toward a common goal.

National Oceanic and Atmospheric 

Administration

NOAA delivers water information and predictions 

about hydroclimatic conditions from floods to droughts. The 

agency’s analyses of snow pack and precipitation, forecasts 

of streamflow and warnings of flooding are indispensable 

with respect to saving lives and managing water resources. In 

recent years, NOAA has developed the National Water Model 

(NWM), a hydrologic model that forecasts streamflow over the 

entire continental United States (http://water.noaa.gov/about/

nwm). The NWM simulates the water cycle with mathematical 

representations of the various water-budget components and 

how they fit together. Models such as the NWM are powerful 

tools for examining near-term predictions of how water availability may change in the future. The USGS has been working 

directly with NOAA to enhance the scientific underpinnings 

of the NWM and provide ways to more effectively incorporate 

certain components of the hydrologic cycle, such as human 

water use and groundwater contributions, in the NWM. NOAA 

also supports research to improve climate prediction for 

hydrologic applications and the use of information on climate 

variability and change by water-resource managers. 

U.S. Environmental Protection Agency

The EPA is responsible for ensuring that drinking water 

is safe and that watersheds, coastal oceans, and their aquatic 

ecosystems are protected and restored to provide healthy 

habitat for fish, plants, and wildlife; to support economic 

and recreational activities; and to ensure a healthy environment for people. To do this, the EPA administers a variety 

of regulatory programs pursuant to the Safe Drinking Water 

Act and Clean Water Act. Under these regulatory programs, 

the EPA collects information about water withdrawn for the 

purposes of public drinking water supply and the discharge 

of contaminants in water, including the water volume that is 

discharged. The databases maintained by the EPA for these 

purposes provide invaluable information for estimating water 

use associated with public water supply systems, the third 

largest sector of water use in the Nation, and on the volume of 

return flows in wastewater discharges from both municipal and 

industrial wastewater treatment facilities. This information is 
4 Continuing Progress Toward a National Assessment of Water Availability and Use

vital to understanding human influence on the water cycle and 

how people move water on the landscape. The USGS has a 

long-standing collaboration with the EPA on water-use science 

and works closely with the agency to improve methods for 

estimating water use.

Many other Federal agencies routinely interact with the 

USGS on information and issues related to water availability 

and use. The data, information, and collaboration of these 

agencies are vital to the success of the Water Census.

National Water Census

In the broadest sense, water availability has four components: (1) the need for a certain volume of water to meet the 

intended purpose, (2) the timing characteristics with which 

water is delivered, (3) the adequate quality of the water for 

the intended purpose, and (4) the need for water to meet both 

human and environmental/ecological uses. The Water Census is complex and must synthesize and report information 

at various spatial scales, from small watersheds to national 

compilations, with an emphasis on compiling and reporting 

this information in a way that is useful to local water managers, states, and others responsible for water management and 

natural-resource issues. A water-availability analysis of any 

given area must consider the quantity of water, the timing 

of water delivery, the quality of the water given the need the 

water is intended to satisfy, and the human and ecological 

needs for water in that area. The focus must be on the scientific aspects of water availability. 

As the primary Federal agency responsible for scientific evaluation of the natural resources of the United States, 

including its water and biological resources, the USGS has 

the lead role in the Water Census. Because the USGS utilizes 

a water-budget approach to water-availability analysis, it has 

a unique capability to assess water-availability conditions 

across the Nation and report to the Congress on the questions 

posed in the SECURE Water Act. The USGS has an existing 

infrastructure that allows it to conduct a regular inventory 

of natural resources and water use, including water quantity, 

water quality, and environmental water needs. The USGS 

accomplishes this task through partnerships with local, State, 

and regional water and environmental agencies. And, as the 

Nation’s authoritative source on water-use information, the 

USGS can characterize the demand of the Nation’s population 

on the water resource.

Water Budgets as a Unifying Theme

Much of the information that makes up a Water Census 

is essentially the components of water budgets for watersheds 

and aquifers. Water budgets account for the inputs to, outputs 

from, and changes in the amount of water in the various components of the water cycle. They are the hydrologic equivalent of the deposits to, withdrawals from, and changes in the 

balance of a checking account and provide the hydrologic 

foundation for analysis of water availability (Healy and others, 

2007). The hydrologic concept of “closing the water budget” 

involves balancing all components of the water budget within 

a given watershed area or aquifer so that the sum of the supply 

terms equals the sum of the demand terms. Basic components 

of water budgets are the supply terms (precipitation, surfacewater inflow, groundwater inflow, and human return flows 

to the watershed) and the demand terms (evapotranspiration, 

surface-water and groundwater flow out of the watershed, and 

human withdrawals). Other components, such as change in 

surface-water and groundwater storage, change in snow and 

ice storage, and interbasin transfers can be either supply or 

demand terms depending on the specific conditions (fig. 1). As 

with a monetary budget or checking account, knowing where, 

when, and how much water (or money) is “flowing” into or 

out of a water budget (or checking account) can illuminate 

how much remains for other uses (water availability) and 

reveal where stresses to the budget (the unpaid bills or water 

shortages) exist or are developing.

During the first 5 years of the Water Census (2009–13), 

much work has been conducted to independently estimate 

various water-budget components. In particular, the Water 

Census has worked to estimate flow in streams across the 

Nation where streamflow is not currently measured, evaporation from land and water surfaces and transpiration from crops 

and other vegetation, groundwater components in regional 

aquifer studies, and many different components of human 

water use. Precipitation, provided by the Water Census for all 

watersheds as a time series of data extending back to 1980, 

was obtained from the Daymet datasets produced by the Oak 

Ridge National Laboratory of the U.S. Department of Energy 

at http://daymet.ornl.gov/.

The Water Census has also conducted substantial work in 

the development of full hydrologic cycle models. The National 

Hydrologic Model (NHM) (Regan and others, 2018), which 

simulates the full hydrologic cycle, is one example. This 

model is capable of providing complete-budget simulations for 

historical reproductions and far into the future. The importance of models like the NHM is that they provide the USGS 

with the capability to test the boundaries of hydrologic budget 

components, estimate their magnitude, simulate them in 

historical and current context, and forecast them under future 

stresses. Additionally, the historical and current simulations 

can be compared to actual measurements to improve understanding of the uncertainty associated with the models. This 

ability provides the USGS with unique insights into the natural 

and anthropogenic processes that influence the water budget.

The next 5 years of the Water Census (2017–22) will be 

devoted to demonstrating how USGS can close the water budget, thus improving the accuracy of water budgets, in major 

areas throughout the Nation. The USGS will also work to 

identify, quantify, and communicate the uncertainty associated 

with the various water-budget components so that users of the 

information understand the reliability and limitations of using 

this information in water-availability assessments.
National Water Census 5

Precipitation

Surface-water inflow,

imported water

(pipelines, canals)

Groundwater inflow

Surface-water outflow,

exported water

(pipelines, canals)

Groundwater outflow

Aquifer

Evapotranspiration

Bedrock

Water tab le

Unsaturated zone

Figure 1. Components of the water budget. (Modified from Healy and others, 2007, fig. 1)

Characterizing Uncertainty

Uncertainty is an important concept in the science of 

water availability. Uncertainty is an inherent factor in all 

hydrologic data collection, estimation techniques, and simulations used in water-availability analysis. Although estimates 

of water availability are commonly stated as specific values, 

there is always a degree of uncertainty associated with the 

estimate and that uncertainty must be understood and communicated to those making resource-management decisions. As 

stated in the first report to Congress, “Errors associated with 

measurement techniques arise from the inability to accurately 

measure specific aspects of the hydrologic system, such as 

streamflow, the water level in a well, or soil properties that 

control evapotranspiration and runoff. Uncertainty arises from 

the inability of our data-collection networks to fully characterize the natural spatial and temporal variability associated with 

hydrology, geology, climate, and land use. Uncertainty also is 

present in hydrologic models because it is impossible to reproduce a natural hydrologic system in a model with complete 

accuracy.” (Alley and others, 2013, p. 7). The USGS made a 

commitment to both quantify and communicate uncertainty 

associated with Water Census products, and it has made progress on that commitment.

Observational uncertainty is error associated with measurement of, in this case, specific aspects of the hydrologic 

cycle. One of the primary components of the hydrologic cycle 

is streamflow, and the Water Census has recently made efforts 

to quantitatively assess the uncertainty associated with individual measurements of streamflow (Kiang and others, 2016) 
6 Continuing Progress Toward a National Assessment of Water Availability and Use

and with estimates of streamflow. With regard to observational 

uncertainty, Kiang and others (2016) found that uncertainty is 

highly variable across streamgages in the Nation. In an earlier 

study, Kiang and others (2013) assessed the ability of the 

USGS streamgaging network to support estimation of streamflow statistics at ungaged locations. For each of the statistics 

used in this study, variability was generally greatest in the arid 

and semiarid central and southwestern United States. These 

two studies support the need for more observations of streamflow and a more complete coverage with streamgages across 

the Nation to reduce the uncertainty of streamflow information. And, because streamflow is generally considered one of 

the most accurately measured components of the hydrologic 

cycle, the need for more observations of other hydrologiccycle components, such as soil moisture or evapotranspiration, 

is implicit. The USGS is also investigating different ways 

of effectively communicating uncertainty associated with 

hydrologic observations. The USGS will implement means of 

communicating uncertainty with hydrologic observations in 

the next 5 years. For example, an estimate of streamflow at an 

ungaged location can be reported as a value with an associated 

probability of uncertainty, indicated by the range around the 

reported value (fig. 2). 

Simulation uncertainty is the error associated with 

estimating hydrologic components for time periods or for 

locations where measurements are not available. Apart from 

observational uncertainty, hydrologic models can frequently 

introduce bias when used to produce statistics for waterresources management (Farmer and Vogel, 2016). The Water 

Census has recognized a need for improved quantification of 

simulation uncertainty and has made strides toward quantifying uncertainty in the simulated hydrologic cycle. Building on 

the work of Farmer and Vogel (2016), the USGS has undertaken studies to apply a novel technique for the quantification 

of simulation uncertainty in daily streamflow (Bourgin, 2015; 

Farmer and Levin, 2017). For components of the hydrologic 

cycle, this technique estimates total uncertainty across all 

components in order to inform site-specific simulations and 

forecasts. Originally developed for streamflow simulation, 

this work is being expanded to consider uncertainty in other 

components of the hydrologic cycle. Effectively communicating simulation uncertainty supports water-resources management when observations are not available. The USGS will use 

visual means similar to those employed in figure 2 to depict 

model uncertainty, although the ranges associated with model 

uncertainty will probably be larger than those associated with 

observational uncertainty.

The USGS remains committed to addressing uncertainty 

in water-availability information. Efforts ongoing at USGS 

will be to quantify uncertainty of observations; to reduce 

uncertainty through improved observations (enhanced measurement precision and accuracy), as well as improved spatial 

and temporal coverage, of hydrologic variables and improved 

estimation techniques resulting in less model uncertainty; and 

to communicate uncertainty in the most useful ways possible. 

Through these measures, the users of Water Census wateravailability information will be fully informed of the context 

of the information. 

000006001200180000000600120018000000

April 11, 2012 April 12, 2012

0

Discharge, in cubic feet per second

10,000

9,000

8,000

7,000

6,000

5,000

4,000

3,000

2,000

1,000

EXPLANATION

Discharge

95-percent prediction interval

68-percent prediction interval

Figure 2. Example streamflow hydrograph with uncertainty intervals.
National Water Census 7

Coordination and Collaboration

The USGS continues to receive guidance on the Water 

Census through the Advisory Committee on Water Information (ACWI) (https://acwi.gov/). The Water Census does this 

through periodic meetings to inform agencies and organizations on the progress to date and to gain advice and guidance 

on the types of water-availability and -use science that are 

most needed to answer society’s questions on that topic. The 

Water Census has collaborated with and received input from 

the following agencies and organizations:

• American Water Resources Association

• American Water Works Association

• Association of Fish and Wildlife Agencies

• Association of Metropolitan Water Agencies

• Association of State Drinking Water Administrators

• Interstate Council on Water Policy

• National Ground Water Association

• The Nature Conservancy

• Sustainable Water Resources Roundtable

• Water Systems Council

• Western States Water Council

• U.S. Army Corps of Engineers

• U.S. Department of Agriculture—Natural Resource 

Conservation Service

• U.S. Department of Agriculture—Economic Research 

Service

• U.S. Department of Agriculture—National Agricultural 

Statistics Service

• U.S. Department of Agriculture—U.S. Forest Service

• U.S. Department of Energy—Climate Change Policy 

and Technology

• U.S. Environmental Protection Agency

• National Aeronautics and Space Administration

• National Oceanic and Atmospheric Administration

• Bureau of Reclamation

• U.S. Fish and Wildlife Service

The USGS also has a long history of working with State, 

county, regional, and Tribal agencies on water-availability 

studies through the Cooperative Matching Funds mechanism 

of the WAUSP. Cooperative Matching Funds are federally 

appropriated dollars used to match State, county, regional, and 

Tribal agency dollars to conduct assessments and research 

into water-availability and -use questions. In reality, the 

WAUSP Cooperative Matching Funds are matched at a ratio 

of approximately 1:2 (one Federal dollars to two non-Federal 

dollars) by State, county, regional, and Tribal agencies for this 

purpose, thereby tripling the monetary investment. The studies 

are conducted by the USGS, with input into the scope of work 

from the participating agencies. This mechanism, which was 

known as the Cooperative Water Program prior to fiscal year 

(FY) 2016, has funded hundreds of millions of dollars of work 

on water-availability and -use science and assessment since 

its inception in 1895 (Taggart, 2004). In FY 2017, the USGS 

allocated $12.4 million in Federal dollars for this purpose, and 

these dollars were matched by $23.7 million in non-Federal 

dollars. The WAUSP Cooperative Matching Funds have been 

used to conduct extensive assessments and research on water 

use; water budgets; groundwater availability, storage, and 

recharge; environmental water science; and evapotranspiration 

(https://water.usgs.gov/coop/products/availability/index.html). 

Starting in FY 2015 and continuing through FY 2017, as 

much as $2 million of the USGS Cooperative Matching Funds 

were directed for water use research. Cooperative projects 

funded by the water use research funds typically addressed 

water-use and the impacts that use had on hydrology and water 

allocations. In the “Topical Studies” section of this report, 

examples of two water-use research studies are provided, 

demonstrating the collaborative scientific contribution that 

is provided by these cooperatively funded efforts with state, 

local, and Tribal agencies. The availability of WAUSP Cooperative Matching Funds is a major benefit to the program, to 

the stakeholders of the program, and to the advancement of 

water-availability and -use science.

Programmatic Resources

The SECURE Water Act authorized $20 million per year 

for the national assessment of water availability and use (here 

called the Water Census) for FY 2009 through FY 2023. This 

report documents the activities under the Water Census from 

FY 2013 though FY 2017. During that period, the Congress 

appropriated the following funds in the respective fiscal years:

Fiscal year Funding

2013 $ 6.1 million

2014 $ 6.1 million

2015 $11.5 million

2016 $13.7 million

2017 $14.6 million

These appropriations represent $52 million of the 

$100 million that the U.S. Congress authorized through the 

SECURE Water Act during this period. This funding provided 

for the activities described in this report. The USGS also 

leveraged existing studies and activities from ongoing USGS 

programs to enhance efforts toward a Water Census. The 

USGS engaged stakeholders to establish priorities for work 

in surface water, groundwater, evapotranspiration, water use, 

and environmental water science—all key areas for the Water 

Census. The studies of surface water and groundwater are fundamental to addressing items (1) and (2) in the periodic reports 

requested by the SECURE Water Act (see Box A), whereas 

evapotranspiration estimates, water use, geographic focus area 

studies, regional groundwater evaluations, and environmental 

water science are fundamental to items (3) to (6). Below, the 

current and completed Geographic Focus Area Studies are 

discussed first, and are followed by the Topical Studies.
8 Continuing Progress Toward a National Assessment of Water Availability and Use

Geographic Focus Area Studies

The SECURE Water Act mandated an assessment every 

5 years of “significant water use conflicts or shortages that 

have occurred or are occurring” (see Box A). The USGS 

interpreted this mandate as the need for information on areas 

of the Nation experiencing significant competition over water 

resources. Water-use conflicts or shortages are area-specific, 

and detailed information is needed to gain a full understanding 

of the situation. As described in USGS Circular 1348 (Alley 

and others, 2013), the Water Census developed the concept 

of Geographic Focus Area Studies (FAS) to serve this reporting purpose. Each FAS is conducted for a period of 3 years, 

followed by a year of report publication and products rollout. 

FAS serve other purposes for the Water Census as well. They 

(1) contribute to ongoing assessments of water availability 

in large watersheds with potential water-use conflicts, (2) 

provide opportunities to test and improve approaches to wateravailability assessment that can be transferred to other areas, 

and (3) inform and “ground truth” the Water Census with 

local information. Watershed stakeholders in each Geographic 

Focus Area are seeking a comprehensive technical assessment of water availability using the best available tools. The 

Apalachicola-Chattahoochee-Flint, Colorado, and Delaware 

River Basins were the first three Geographic Focus Area 

Studies conducted by the USGS Water Census; these studies 

are now completed. In 2015, an intensive process was conducted to identify three new FAS; consequently, studies were 

begun in the Carolina Coastal region, Red River of the south, 

and Upper Rio Grande River Basins. The completed FASs, 

including the work that has been accomplished and published 

as part of these studies, are discussed below, and are followed 

by a discussion of the ongoing FASs. Appendix 1 contains 

a comprehensive bibliography produced as part of the completed FAS.

An important aspect of each FAS is stakeholder involvement. During the development of each FAS work plan, the 

USGS hosts stakeholder meetings to gather input on the 

study objectives from as many stakeholders as possible. The 

USGS takes this input into consideration when developing the 

work plan for each FAS. Stakeholder meetings are also held 

throughout the execution of the study to provide updates on 

the progress and solicit input on future work that would be 

most applicable and useful to the stakeholders. 

Apalachicola-Chattahoochee-Flint River Basin 

(2011–15)

The Apalachicola-Chattahoochee-Flint (ACF) River 

Basin covers 20,230 square miles in Georgia, southeastern 

Alabama, and northwestern Florida. The basin’s population 

was 3.8 million in 2010, but many people outside the basin 

rely on water from the ACF.

Litigation over appropriation of water among the three 

states that occupy parts of the basin has been ongoing for 

nearly 30 years. Most recently, a Special Master recommended 

denying the State of Florida’s request for equitable apportionment of waters in the ACF Basin in a case against the State of 

Georgia that will ultimately be decided by the U.S. Supreme 

Court. The likelihood of litigation among the states is high, as 

continuing population growth in the Atlanta metropolitan area 

and development of agricultural irrigation in the lower Flint 

and Chattahoochee Basins is likely to continue to be a concern 

for water users downstream; for ecological needs in streams 

and rivers; and for the oyster fishery in Apalachicola Bay, 

Florida (fig. 3).

Historically, resources for resolving the interstate conflict 

over water availability have focused primarily on the management of large reservoirs that are operated by the U.S. Army 

Corps of Engineers and on flows in the major rivers in the 

basin. The ACF FAS provides scientific information on the 

many other important water-availability influences—specifically, estimates of water withdrawals and wastewater returns, 

groundwater pumping for irrigation, interbasin transfers, 

storage in unmanaged reservoirs, and effects of increases in 

impervious surface and climate variability on water availability. In addition, the FAS has studied flows in smaller streams 

that have received little attention in the past, but are critical to 

aquatic ecosystems throughout the basin. A complete bibliography of the ACF River Basin FAS is presented in appendix 1.

Synoptic Effort

During the first year of the study (2011), exceptional 

drought conditions prevailed in the lower Apalachicola-Chattahoochee-Flint and adjacent Aucilla-Suwannee-Ochlockonee 

River Basins during the summer months. Cumulative rainfall departures from 1981–2010 climate normals were in the 

range of 17 to 27 inches, providing an excellent opportunity 

to measure streamflow and groundwater levels under extreme 

dry conditions. Measurements indicated that water levels in 

12 of 43 surficial aquifer wells and 128 of 312 Upper Floridan 

aquifer wells were at record lows. Most streamflows measured 

were below normal (<25th percentile), with 286 miles of 

streams losing flow in the downstream direction and 606 miles 

of streams being dry. These data are important for understanding how the hydrologic system functions under lowflow conditions and were used to calibrate surface-water and 

groundwater flow models. The results of the synoptic study are 

published in a USGS Scientific Investigations Report (Gordon 

and others, 2012).

Water-Use Component

Water-use estimates and water returns for the ACF Basin 

were compiled by category and location for calendar year 
Geographic Focus Area Studies 9

G U L F O F M E X I C O

GEORGIA

ALABAMA

FLORIDA

SOUTH

CAROLINA

Chattahoochee River

Chipola River

Apalachicola River

New River

Flint River

Lake Lanier

West Point Lake

Walter F. George

Reservoir

Lake

Seminole

Lake Harding

Athens

Atlanta

Columbus

Auburn

Tallahassee

86° 85° 84° 83°

34°

33°

32°

31°

30°

Base modified from U.S. Geological Survey

1:100,000-scale digital data

FL

AL GA

TN NC

MS

KY VA

SC

IL MO WV

LA

AR

IN

0 25 50 MILES

0 25 50 KILOMETERS

Figure 3. Location of the 

Apalachicola-Chattahoochee-Flint 

River Basin. (From Alley and others, 

2013, fig. 2)
10 Continuing Progress Toward a National Assessment of Water Availability and Use

2010. Categories included public supply, self-suppled domestic, self-supplied commercial, industrial, mining, agricultural 

(crop irrigation, livestock, and aquaculture), and thermoelectric-power generation use. These data were compiled at 

the 8-digit hydrologic unit code (HUC-8) subbasin scale and 

published in a USGS Scientific Investigations Report (Lawrence, 2016). 

In 2010, an average of 1,645 million gallons per day 

(Mgal/d) was withdrawn in the ACF Basin, with about 

35 percent of withdrawals derived from groundwater sources 

and 65 percent derived from surface water. About 564 Mgal/d 

(34 percent of withdrawals) was returned to streams and rivers in the basin (mostly as treated wastewater), and less than 

4 percent of withdrawals was transferred outside the ACF 

Basin (interbasin transfers). Although population in the basin, 

particularly in the Atlanta metropolitan area, increased by 

45 percent from 1990 to 2010, surface-water use declined during that period, most likely as a result of conservation measures. Groundwater use, in contrast, has steadily increased as a 

result of increases in pumping for agricultural irrigation, with 

spikes in use during drought years.

Agriculture is the largest water use in the ACF Basin and 

estimates of agricultural water use are typically complex, with 

high levels of uncertainty. To address this uncertainty, three 

different methods were tested in the ACF FAS to compare 

their ability to match estimates of irrigation water use derived 

from metered wells. These methods include (1) crop demand, 

(2) geostatistical methods with variography and conditional 

simulation, and (3) remote-sensing technology to identify 

irrigated lands. Results are presented in a USGS Scientific 

Investigations Report (Painter and others, 2015) and indicate 

that information on local agricultural practices and spatial 

and temporal distribution of irrigated lands are critical for all 

three methods.

Simulating Surface-Water and Groundwater 

Flow

The USGS evaluated hydrologic flows in the ACF Basin 

by using linked groundwater (MODFLOW) and surface water 

(Precipitation Runoff Modeling System, PRMS) models. 

These are tools that resource managers can use to evaluate 

the availability of freshwater to meet the competing needs 

throughout the basin. The models greatly enhance the ability 

to simulate the effects of groundwater pumping on streamflows under a variety of climate and water-use scenarios and 

help to evaluate adequate instream flow for ecological needs 

throughout the basin. The models are documented in USGS 

Scientific Investigations Reports (Jones and others, 2017; 

LaFontaine and others, 2017). In addition, enhancements to 

the PRMS were made to facilitate the incorporation of wateruse data (described in the preceding section), stream and lake 

flow routing, and simulation of surface-depression storage 

and are published in a USGS Techniques and Methods Report 

(Regan and LaFontaine, 2017).

The simulation results indicate that recharge to the 

groundwater system is much more dynamic than previously 

believed, with nearly all recharge occurring during winter 

months or infrequently during periods of intense rainfall 

during the remainder of the year. Streamflows simulated for 

2008–12 with flow components from the linked models provided improved estimates for the warm season months, when 

irrigation is active, and underestimated streamflow volumes 

during the cool season months. The linked models indicated 

that groundwater storage in the Floridan aquifer in the study 

area declined by about 3.6 percent, and the decline is likely 

the result of dry conditions during the simulation period. The 

model was not used to simulate long-term changes in storage, 

but the simulated changes in groundwater storage coupled 

with a more realistic simulation of the dynamics of the system indicate that the model will be useful for future waterresources management.

Environmental Water Component

The environmental water project in the ACF Basin 

improves understanding of the ways in which changes in 

streamflow conditions may affect an important aspect of the 

health of streams and rivers—specifically, the local diversity 

of fishes. Many studies over the last two decades have shown 

correlative evidence that streams with more altered flow 

regimes also support diminished fish communities; however, little is known about the mechanisms underlying these 

patterns. By quantifying how well fishes can persist through 

periods of unusually low or high flows, or recover following stressful events, scientists can help managers forecast 

water-management effects on future diversity and abundance 

of fishes, enabling them to make effective resource-management decisions (Freeman and others, 2013; Peterson and 

Freeman, 2016).

To provide data on the mechanisms by which streamflows 

affect fish assemblages, the USGS completed 233 surveys of 

fishes at 40 ACF sites over a period of 6 years, including years 

of exceptionally low and relatively high streamflows. The ACF 

is a useful ecological setting for studying streamflow effects 

on fishes not only because the basin is home to a high diversity 

of fishes (at least 100 native species), as well as a variety of 

stream types, including low-gradient, sand-dominated streams 

in the Coastal Plain and higher gradient, cobble-dominated 

streams in the Piedmont and Blue Ridge Provinces. Therefore, 

analyses of the survey data have focused on understanding 

how streamflow variation affects persistence and resiliency of 

fishes that have differing habitat requirements, in physically 

different environments. 

Important findings of this work include new evidence that 

fishes show an increasing likelihood of loss from stream sites 

as seasonal streamflows dip below long-term averages, but 

that these losses may be balanced by species re-establishing 

during periods of above-average flow (Wheeler and others, 

2017, 2018). However, fishes which primarily inhabit streams 
Geographic Focus Area Studies 11

do not appear equally resilient, and populations of the same 

species may recover more readily in some streams than others. In particular, fishes that commonly inhabit a wide range 

of aquatic habitats (including lakes, wetlands, and streams), 

such as many sunfishes and mosquitofishes, may be more 

likely to re-establish at a site following local extirpation than 

are stream-dependent fishes, including many minnow and 

darter species. Additionally, populations of the same species 

show greater resilience to local losses in Coastal Plain streams 

than in higher gradient upland (Piedmont and Blue Ridge) 

streams. These findings imply that effective streamflowmanagement strategies for protecting biological diversity 

may differ depending on the types of fishes present and the 

physical setting.

Colorado River Basin (2011–15)

The Colorado River is about 1,450 miles long with a 

drainage-basin area that covers about 246,000 square miles in 

parts of seven states (fig. 4). Because of many factors, including that the most downstream portion of the river crosses the 

international border with Mexico, water management, water 

law, and flow regulation are a complex system involving 

international treaties, interstate compacts, and Supreme Court 

decrees. Within the United States, the water diverted from the 

Colorado River serves more than 30 million people, many 

located outside the hydrologic basin in California, Colorado, 

New Mexico, and Utah, and irrigates more than 4 million 

acres of agricultural land. Flow in the Colorado River also 

supports a multibillion dollar tourist and recreational industry. 

The Colorado River is a critical resource for a substantial portion of the mostly arid southwestern United States. Declining streamflows, increasing population, and a projected drier 

future climate present additional challenges to an already 

stressed water-delivery system.

Reclamation plays a major role in the control and distribution of surface water across the Colorado River Basin 

through the management of large Federal water projects like 

Glen Canyon Dam (Lake Powell) and Hoover Dam (Lake 

Mead). These and several other reservoirs and diversions 

throughout the basin are operated as a single system to facilitate the beneficial use of the annual runoff, which originates 

largely as snow melt in the Rocky Mountains. Effort is made 

each year to track the annual “natural” flow and monitor 

the consumptive surface-water use to meet litigated rights 

(part of what is referred to as “The Law of the River”), meet 

contractual obligations for water delivery, and to generate a 

substantial amount of hydropower for customers in the southwestern United States. In 2012, Reclamation and its partners 

completed a Colorado River Basin Water Supply and Demand 

Study (https://www.usbr.gov/lc/region/programs/crbstudy.

html). Early discussions with Reclamation and other stakeholders in the Colorado River Basin identified several aspects 

of the basin water budget that were in need of additional 

study and information after the Supply and Demand Study. 

Improved understanding of water use in the basin (especially 

agricultural consumptive uses); an increased understanding 

of snowpack development, runoff, and sublimation losses; 

and the relative importance of regional groundwater flow and 

groundwater discharge supporting streamflows were identified 

as primary components needing attention during the Colorado 

River Basin FAS. These components became the focus of the 

Colorado River Basin FAS. The following subsections provide 

a short summary of the USGS contribution to these topics. 

A complete bibliography of the Colorado River Basin Focus 

Area study is presented in appendix 1.

Water-Use Component

The USGS is conducting a basin-specific water use 

study, analyzing uses by category and HUC-8, including 

analysis of trends, at 5-year increments from 1985 to 2010. 

This study will also identify all major transfers of water out 

of the Colorado River Basin to adjacent areas for years 2000, 

2005, and 2010. Water-use information from the seven basin 

states is being compiled and quality-assured, and consistent 

water use estimates provided on surface-water diversions and 

withdrawals, groundwater withdrawals, and surface-water 

return flows. Particular emphasis will be placed on analyzing 

trends in water use over this 25-year period. The water-use 

study presents water-withdrawal information aggregated at 

the HUC-8 level for the following water-use sectors: public 

supply, self-supplied domestic, self-supplied commercial, 

industrial, livestock, mining, aquaculture, irrigation, thermoelectric and hydroelectric water, and wastewater return 

flows. Consumptive use estimates are included in the study for 

irrigated agriculture and thermoelectric power generation—

the only two categories of use for which USGS methods for 

estimating consumptive have been updated since 1995. These 

two water-use categories are the largest water uses nationally 

and in the Colorado River Basin. The study, when completed, 

will provide an improved understanding of the major sectors 

of water use and the spatial distribution of those uses within 

the Colorado River Basin.

Groundwater and Base-Flow Component

Historically, management of water resources in the Colorado River Basin has focused on surface water; however, surface-water flow is sustained, in part, by groundwater discharge 

to streams. In light of recent droughts and ongoing landscape 

change, groundwater and surface water must be understood 

and managed as a single resource. Compared with surfacewater flows, groundwater discharge to streams is difficult to 

measure, and is a less well understood component of the water 

budget. A series of studies was conducted using instream 

water-quality data to estimate the fraction of streamflow that 

is supported by groundwater discharge to streams across the 
12 Continuing Progress Toward a National Assessment of Water Availability and Use

Base modified from U.S. Geological Survey

1:100,000-scale digital data

115° 110° 105°

40°

35°

Lake

Powell

Great

Salt Lake

Lake

Mead

Utah Lake

Colorado

River

Little Colorado R iver

Virgin River

San Pedro River Salt River

Gila

River

Green River

Yampa River

Green River

San Juan River

White River

Provo

Denver

Tucson

Phoenix

El Paso

Las Vegas

Boise

Albuquerque

Fort Collins

Salt Lake City

UTAH

ARIZONA

NEVADA

WYOMING

IDAHO

NEW MEXICO

COLORADO

CALIFORNIA

TEXAS

CA

MT

AZ

ID

NV

NM

CO

OR

UT

WY

WA

TX

ND

SD

NE

0 100 200 KILOMETERS

0 100 200 MILES

Figure 4. Location of the Colorado River Basin, within the United States. (From Alley and others, 2013, fig. 4)
Geographic Focus Area Studies 13

Upper Colorado River Basin. The methods included continuous estimation of groundwater discharge to streams at selected 

sites for periods of as long as 30 years (Miller and others, 

2014; Miller and others, 2015; Rumsey and others, 2015), and 

the development of a watershed model that predicted groundwater discharge to streams at more than 10,000 stream reaches 

in the basin (Miller and others, 2016). Results indicate that, on 

average, more than half the streamflow in the Upper Colorado 

River Basin is sustained by groundwater discharge to streams, 

and much of this groundwater discharge to streams originated 

as precipitation that fell in the past 10 to 100 years (Solder and 

others, 2016). These results indicate that streamflow depends 

on groundwater discharge to streams and that the joint groundwater/surface-water resource in the Upper Colorado River 

Basin may respond rapidly to future anthropogenic and natural 

changes in the environment.

Snow Pack and Sublimation Component

Water available for ecological and human needs in the 

Colorado River Basin is derived largely from high mountain 

snow (the “snowpack”) that accumulates during the winter and 

spring and melts during the summer each year. These annual 

mountain snowpacks serve as large natural water reservoirs, 

and their melting snow provides 70 to 85 percent of the annual 

surface-water runoff in this region. Determining the amount 

of water stored in mountain snowpacks each year is important 

for successfully managing and forecasting water resources 

in the Colorado River Basin. The USGS utilized two existing models for estimating snowpack water resources as part 

of the Colorado River Basin FAS - SNODAS (https://data.

noaa.gov/dataset/dataset/snow-data-assimilation-systemsnodas-data-products-at-nsidc) and SnowModel (Liston and 

Elder, 2006). The Colorado River Basin FAS also investigated 

factors affecting snowpack distribution, such as snowmelt timing and losses of snowpack water by snow sublimation. Peak 

snowmelt in Colorado is occurring 2 to 3 weeks earlier than in 

recent history (Clow, 2010), and upward trends in the deposition of windblown dust (a solar heat concentrator) onto mountain snowpacks is contributing to changes in snowmelt timing 

(Clow and others, 2016). Additionally, physical measurements 

of snow sublimation (Sexstone and others, 2016), combined 

with simulated estimates, show that snow sublimation is 

highly variable and an important component of the water balance in the Colorado River Basin, with losses of as much as 

27 percent of winter precipitation (G.A. Sexstone and others, 

U.S. Geological Survey, written commun., 2017). Results of 

these Colorado River Basin FAS snowpack water-resources 

investigations have important implications that can be used for 

improving water resources forecasting and management in the 

Colorado River Basin.

Delaware River Basin (2011–15)

The Delaware River Basin covers 13,500 square miles 

in parts of four states—New York, New Jersey, Pennsylvania, and Delaware (fig. 5). The population within the basin is 

approximately 7.3 million.

The basin has the largest interbasin withdrawal of water 

east of the Mississippi River and provides water to more 

than 15 million people, half of them outside the basin. Two 

Supreme Court decrees and coordination by an interstate river 

basin commission are just part of the history of allocating 

water resources in the basin. Concerns about the effects of 

new natural-gas development and the freshwater requirements 

for endangered sturgeon and a recently discovered mussel species have added new complexities to water management in the 

upper part of the basin. 

With input from more than 60 stakeholder groups, including Federal, state, and local governments, non-governmental 

organizations, academics, and others, the following issues 

were identified as priorities in the Delaware River Basin:

• acquisition, management, and integration of improved 

water-use and water-supply data;

• development of environmental water science that 

includes enhancement of the existing Decision Support 

System (DSS) for parts of the Delaware River, definition of relations between streamflow processes and 

aquatic-assemblage responses in tributaries, and development of a streamflow-estimation tool for ungaged 

sites (Archfield and others, 2010); and

• development of a hydrologic watershed model to 

evaluate the effects of water stressors, such as growth 

of population centers, land-use change, and climate 

variability and change, on water resources in the basin.

In response to these needs the Water Census developed 

the following publications and tools. A complete bibliography 

of the Delaware River Basin FAS is presented in appendix 1.

Improved Water-Use and Water-Supply 

Information

Water-use information for 2010 from the four basin states 

was compiled and quality assured, and consistent water-use 

estimates were provided for surface-water diversions and 

withdrawals, groundwater withdrawals, and surface-water 

return flows. In addition, estimates of unreported domestic 

use were developed. A report on water use in the basin was 

published (Hutson and others, 2015), and data on thermoelectric, public-supply, agricultural, commercial, and other uses 
14 Continuing Progress Toward a National Assessment of Water Availability and Use

NEW YORK

PENNSYLVANIA

NEW JERSEY

MARYLAND

DELAWARE

Allentown

Trenton

Dover

Baltimore

Philadelphia

Neversink River

Lehigh River

Schuylkill River

Delaware

River

Musconetcong River

Maurice River

Pepacton

Reservoir

Cannonsville

Reservoir

Lake

Wallenpaupack

Lake Hopatcong

Delaware

Bay

ATLANTIC

OCEAN

Chesapeake Bay

0 25 50 MILES

0 25 50 KILOMETERS

76° 75° 74°

42°

41°

40°

39°

NY

PA

ME

VT

VA

NH

MA

CT

MD NJ

WV

DE

RI

Base modified from U.S. Geological Survey

1:100,000-scale digital data

Figure 5. Location of the 

Delaware River Basin. (From 

Alley and others, 2013, fig. 6)
Geographic Focus Area Studies 15

between major components of streamflow (magnitude, durations, frequency, timing, and rate of change) and the response 

of aquatic assemblages (environmental waters), Delaware 

River Basin Streamflow Estimator Tool (DRB-SET) was 

developed (Stuckey, 2016). This tool can be used to assist 

managers in making decisions about meeting human water 

needs while maintaining healthy ecological communities in 

streams. A user’s manual developed for the DRB-SET has 

been published and the tool is available to the public (Stuckey 

and Ulrich, 2016).

Coastal Carolinas Basins (2015–19)

The coastal regions of the United States are substantially 

more crowded than the United States as a whole, and although 

these growing coastal areas represent a nexus of natural 

resources and economic opportunity, they also represent areas 

of increasing conflict over these resources. Although other 

areas of the United States are also growing, the land limitations in coastal regions often lead to higher population densities and a sharper, more focused interface between fresh- and 

saltwater ecosystems. Population growth has tripled since the 

1970s in the Coastal Plain portions of the Lower Cape Fear 

River and Lower Yadkin/Pee Dee/Waccamaw River Basins 

in North Carolina and South Carolina, a region bounded by 

the Atlantic Ocean, Atlantic Intracoastal Waterways, and 

tidally affected brackish rivers (fig. 6). Coastal areas of the 

southeastern United States, particularly in the Carolinas, are 

experiencing increased annual pulses of tourist populations 

that often place unanticipated stresses on the natural resources. 

This confluence of people and a geography that is highly 

susceptible to the effects of hurricanes, routine droughts, and 

climate change/sea-level rise has presented unique challenges 

to water-resource managers and environmental regulators. To 

further highlight and confirm the water conflict in this region 

of the Carolinas, in 2015 (just prior to the beginning of the 

Coastal Carolinas FAS), the North Carolina General Assembly passed a bill (NC House Bill 186, March 10, 2015, http://

www.ncleg.net/Sessions/2015/Bills/House/PDF/H186v6.

pdf) calling for “...an evaluation of the adequacy of currently 

available supplies to meet the expected long-term needs for all 

water demands... of the portions of the Cape Fear River Basin 

within Brunswick, New Hanover, and Pender Counties ...”. 

The Coastal Carolina Basins FAS (fig. 7) has four 

major components: (1) refined water-use data and estimates 

of HUC-8 water use; (2) a groundwater-flow and saltwaterintrusion model of the surficial, Castle Hayne, Crouch Branch/

Peedee, and McQueen Branch/Black Creek aquifers for the 

study area; (3) surface-water models of the Cape Fear River 

and Yadkin/Pee Dee/Waccamaw River Basins to simulate 

watershed/streamflow response to various future scenarios of 

climate and land-use changes and water use; and (4) ecological response models relating fish and macroinvertebrates to 

streamflow and land use in the Cape Fear River and Yadkin/

PeeDee/Waccamaw River Basins. Additionally, existing population change forecasts from the U.S. Census Bureau (U.S. 

are reported for 427 12-digit hydrologic unit code (HUC-12) 

subbasins. This was the first time USGS studies provided 

yearly water-use estimates at the detailed HUC-12 scale (a 

goal of the Water Census). Data for the HUC-12 subbasins are 

available (Hutson and others, 2016a) as Excel® tables at the 

Water Census ScienceBase-Catalog (https://www.sciencebase.

gov/catalog/item/5762a410e4b07657d19a71cb). 

Basin Hydrologic Model

The Water Availability Tool for Environmental Resources 

(WATER) is a hydrologic watershed model developed by the 

Water Census for the non-tidal Delaware River Basin (see 

Box B). The model includes information on water use, and 

projections of future land use and climate change for the years 

2030 and 2060. The model and developed datasets have been 

published and are publicly available (Williamson and others, 

2015; Williamson and Lant, 2015). Model scenarios describing possible future effects of climate and land-use change on 

basin water resources are also contained in these publications. 

The model is currently being used in a detailed assessment of 

how changes in climate might affect management of future 

reservoir releases.

Environmental Water Science on Mainstem

Flow on the mainstem of the Delaware River is controlled, to a large extent, by waters released from drinkingwater reservoirs and power-supply reservoirs. Releases are 

regulated to meet a variety of needs, including water-supply 

demands, protection of downstream fisheries habitat, and 

repelling the upstream movement of saltwater in the Delaware Estuary. These releases need to be managed to protect 

the cold-water fisheries on the Delaware River and maintain 

aquatic community diversity, structure, and function. The 

Delaware FAS developed a tool to evaluate the relation among 

flows, environmental variables (such as temperature), and 

ecological response. The Water Census study on the mainstem 

of the Delaware River determined the environmental water 

needs of a variety of freshwater species such as fishes, mussels, and submerged aquatic vegetation in the Upper Delaware 

River Basin. This information was incorporated into a DSS 

that allows managers to evaluate how different flow scenarios 

might affect the amount of habitat that is available for each 

species to spawn, grow, and reproduce (Maloney and others, 

2015). The DSS tool has been published and is being used 

to assist the Flexible Flow Management Committee of the 

Delaware River Basin Commission in evaluating how releases 

could affect fish communities on the Delaware River (Talbert 

and others, 2014).

Environmental Water Science on Tributaries

Environmental data are typically collected on tributaries 

where no flow information is available. To assist ecologists 

in the Delaware River Basin interested in studying relations 
16 Continuing Progress Toward a National Assessment of Water Availability and Use

Box B. Applying the Science to Water Management in the Delaware 

River Basin 

The Delaware River Basin Commission (DRBC) is 

a federal-state compact agency established in 1961 and 

charged with conservation, utilization, development, management, planning, control, protection, and preservation of 

the waters of the Delaware River Basin and Estuary. The 

DRBC works collaboratively with the basin states (Delaware, New Jersey, New York, and Pennsylvania) on all 

aspects of integrated water resource management including 

water allocation and the protection of drinking water and 

other water intakes.

In the 1960s, after eight consecutive years of below 

normal precipitation and a severe drought, the DRBC 

worked with the states and stakeholder to develop flow and 

drought management plans and actions that would ensure 

that the basin would be resilient to a similar drought of 

record. While the states are responsible for many aspects 

of the plans related to water conservation, the DRBC has 

the overall responsibility to preserve regional storage for 

the purposes of water supply, flow augmentation, and 

water quality in the Delaware River, and salinity control in 

the Delaware River Estuary. These plans were adopted in 

1983 and have been modified over time to address different 

stakeholder issues, including minimum releases for ecological protection and some limited spill mitigation, without 

impacting other reservoir purposes such as water supply.

With the predicted trends in precipitation and temperature during this century, the DRBC has embarked on 

a project to assess the potential risks to DRBC’s overall 

flow and drought management goals. Then, plans and 

programs will be developed to adapt to identified risks. 

To do this, DRBC will use the Water Availability Tool for 

Environmental Resources (WATER), developed during the 

Water Census pilot project for the Delaware River Basin 

and the DRBC’s Water Management Planning Support 

Tool (DRB-PST). Used together, the DRBC will be able 

to assess future water availability and drought resilience 

to educate decision makers about risks to the basin and 

begin the process of adaptive management planning and 

implementation.

With WATER, it is possible to generate the inflows 

and associated water use information, which are the major 

factors that determine water availability with DRB-PST. 

Precipitation, temperature, soil characteristics, land use, 

slopes, and other relevant information are used by WATER 

to develop a water budget for sub-basins and calculate the 

amount of runoff (streamflow) expected to reach the various streams and reservoirs in the basin. The streamflows 

are used by DRB-PST to simulate the flow and drought 

management programs and assess how well they perform 

under the future conditions.

Preliminary results indicate that the changes to 

streamflows, which enter reservoirs, streams, and rivers, 

are primarily seasonal and increase by a modest amount 

in the future. However, the seasonality of the streamflow 

shifts and is primarily related to changes in the snow pack 

and evaporation. The change in snow pack is primarily 

related to the change in temperature and not the lack of 

precipitation. The precipitation falls as rain rather than 

snow and arrives at the reservoir as runoff within days 

rather than snow melt weeks or months later. As a result, 

the timing of reservoir refills is likely to change rather than 

the overall amount of water that reaches the reservoirs. 

Streamflows in the summer are reduced, but indications 

are that those reductions are primarily due to the increased 

evapotranspiration resulting from increased temperatures.

The DRBC also uses hydrodynamic and water quality 

models to evaluate salinity and chloride concentrations in 

the Delaware Estuary. Salinity and chlorides are problematic for drinking water and other water intakes due to 

the potential for increased corrosion and the complexity 

of treatment technologies. Model results indicate that the 

Sea Level Rise (SLR) in the Delaware Estuary may hinder 

the ability of the existing flow management programs to 

control salinity. DRBC will be using a linked combination 

of WATER, DRB-PST, and these other models to evaluate 

how freshwater inflows into the estuary will alter the salt 

water–fresh water interface.

Once the risks of increased precipitation, temperature, and sea level rise have been evaluated, DRBC can 

determine if existing flow management programs can meet 

stakeholder needs and also maintain the current level of 

salinity control. If additional storage or other infrastructure 

is needed, combinations of flow management and infrastructure programs can be developed, constructed, and/or 

implemented to address the impacts of predicted trends in 

climate and SLR

—Amy Shallcross, Delaware River Basin Commission
Geographic Focus Area Studies 17

Census Bureau, 2012) and spatial urban-growth scenarios 

based on research from North Carolina State University and 

the USGS are being applied to the study area to drive various 

land-use and water-use change scenarios that will be simulated 

with the groundwater, surface-water, and ecological-response 

models. Stakeholder input was important in establishing these 

major study components. 

The water-use component includes developing a sitespecific database of water use for the study area, refining 

county-level estimates and aggregating site-specific wateruse data to the HUC-8 level, exploring improved methods to 

estimate agricultural withdrawals, and compiling available 

water-use projections. The study is focusing on water-use data 

for the period 1995–2015. 

An updated and refined groundwater-flow model of the 

study area will be used to inform resource decisions based on 

various current and future climate, land-use, and groundwateruse scenarios. The groundwater-flow model will be converted 

Pe e De e River

WACCAMAW NATIONAL

WILDLIFE REFUGE

NORTH CAROLINA

SOUTH CAROLINA

WACCAMAW

TRIBAL GROUP

Lake

Waccamaw

USGS

Borehole

0 25 50 MILES

0 25 50 KILOMETERS

03040201

03030007

03040206

03030006

03040204

03030005

03030001

03040208

03040207

Cape F ear River

02106500

02108000

Atlantic

Intracoastal

Waterway

79°30' 78°

34°30'

33°

Wacc amaw Riv e r

40

95

20

26

85 73

526

74

NORTH CAROLINA

SOUTH

CAROLINA

GEORGIA

VIRGINIA

Base from ESRI digital data, 2010,

Hydrologic boundary units from U.S. Department of Agriculture-Natural Resources 

Conservation Service, U.S. Geological Survey, and Environmental Protection Agency, 2009,

National Wildlife Refuge data from U.S. Fish and Wildlife Service, 2014

Area shown A T L A N T I C

02131000

02132000 02135000

02105500 02107000

Myrtle Beach and

Grand Strand area

Wilmington

EXPLANATION Georgetown

03040206

Focus Area Study

Hydrologic Unit and code number

U.S. Geological Survey streamgage 

used as upstream extent, and number

02132000

O C E A N

Bald Head

Island

Conway

Figure 6. Location of the Coastal Carolina Basins Focus Area Study.
18 Continuing Progress Toward a National Assessment of Water Availability and Use

Figure 7. U.S. Geological Survey Coastal Carolina Basins Focus Area Study webpage. (From U.S. Geological Survey, 2017a)

to a model that can be used to evaluate potential saltwater 

intrusion into the aquifers resulting from groundwater pumping scenarios for as many as two localized population centers 

within the study area.

Surface-water models built using the Soil and Water 

Assessment Tool (SWAT) model (Arnold and Fohrer, 2005) 

will be used to simulate streamflows at ungaged ecological 

sampling sites and key locations for water-supply in the study 

area, while also accounting for water-use and climate-change 

scenarios. The simulated streamflow data from the Yadkin/

Pee Dee/Waccamaw River surface-water model will be 

incorporated into the existing Pee Dee River and Intracoastal 

Waterway Salinity Intrusion Model-Decision Support System (PRISM-2 DSS) (Conrads and others, 2013), which was 

developed to evaluate the salinity dynamics of the Atlantic 

Intracoastal Waterway and the Waccamaw River on the basis 

of variability of streamflow resulting from climate change and 

the effects of sea-level rise. The PRISM-2 DSS, with updated 

streamflow information, will be used to simulate the effects 

of future climate, land-use, and water-use changes on the frequency, magnitude, and duration of saltwater intrusion.

Empirical models relating fish and macroinvertebrate 

metrics to flow metrics and land use will be developed for 

the Yadkin/Pee Dee/Waccamaw and Cape Fear River Basins 

by using daily streamflows obtained from the surface-water 

models. These models will also be used to predict aquaticbiota community changes associated with the various wateruse, land-use (urbanization), and climate-change scenarios. 

The ecological-flow response models will also be used to test 

the efficacy of various alternatives for flow objectives for the 

protection of ecological integrity in streams by adding these 

actual or hypothetical ecological-flow objectives into current 

and projected flow and water-use scenarios.

Combined, these new data and tools can be used by 

resource managers to plan future surface-water allocations and 

groundwater development and withdrawals as stakeholders 

evaluate potential consequences on ecology and susceptibility 

of the aquifers to saltwater contamination.
Geographic Focus Area Studies 19

Red River Basin (2015–19)

The Red River Basin is an area of about 93,200 square 

miles with a population of about 4.3 million people. The basin 

is characterized by flat agricultural land and is relatively arid, 

with annual precipitation ranging from less than 30 inches in 

the western headwaters to 50 inches at the confluence with the 

Mississippi River (fig. 8). Concerns and conflicts about water 

in the Red River Basin have been growing because of increasing needs for freshwater in the rapidly expanding Dallas-Ft. 

Worth, Texas, area; cycles of severe drought in the basin; 

and increases in water use for power generation and other 

purposes. The Red River Compact, authorized by Congress 

in 1955 and signed by the States of Arkansas, Louisiana, Oklahoma, and Texas in 1978 (P.L. 92-500, 33 USG, 33 U.S.C., 

sections 1251 et seq.), documents the volume of water each 

state in the basin can use or store from the Red River Basin. 

Despite the compact, litigation over water use among member states recently occurred: Tarrant Regional Water District 

v. Herrmann—U.S. Supreme Court, 2012 (https://www.

supremecourt.gov/opinions/12pdf/11-889_5ie6.pdf); State of 

Oklahoma, Choctaw Nation, Chickasaw Nation, Oklahoma 

City Settlement, 2016 (https://www.waterunityok.com/).

The USGS worked collaboratively with Federal, State, 

and local governments, Tribes, regional water managers, and 

other stakeholders to develop an approach to comprehensively 

assess water budgets and water availability under current 

hydrologic, land-use, and water-demand conditions and for 

a range of future conditions. To achieve the aforementioned 

comprehensive assessment, the Red River FAS is divided 

into four objectives: (1) refinement and enhancement of water 

withdrawal estimates (1980–2015) to provide a detailed picture of water use in the basin, (2) development of a groundwater-flow model to quantify groundwater/surface-water interactions and likely effects of increased withdrawals upstream 

from the Denison Dam on Lake Texoma, (3) construction of 

a rainfall-runoff model to simulate streamflow and compute 

daily water balances for each hydrologic response unit within 

the basin, and (4) develop an understanding of the relation 

between changes in water availability and the fish-community 

response for the basin within Oklahoma and Texas. Products 

of this study will include a water-use database, complementary 

groundwater and surface-water models, and an assessment of 

environmental water needs for the Red River Basin (fig. 9).

Upper Rio Grande Basin (2015–19)

The growing gap between water supply and demand in 

the Upper Rio Grande Basin has resulted in ongoing conflict 

and litigation among Federal, Tribal, State, and local users. 

The USGS Upper Rio Grande FAS is assessing existing 

knowledge and contributing new scientific data and interpretation to help stakeholders address these critical water issues.

The Upper Rio Grande River drains 32,000 square miles 

and flows 670 miles from its headwaters in Colorado (peak 

elevation 14,351 feet [ft]) to an area sixty miles downstream 

from El Paso, Texas (elevation 3,450 ft) (fig. 10). The Upper 

ARKANSAS

NEW MEXICO

OKLAHOMA

TEXAS

LOUISIANA

Amarillo

Shreveport

Wichita River

Ouachita River

Saline River

Red River

Sulphur River Big Cypress Creek

Red River Little River

Prairie Dog Town Fork Red River

Washita River Lake

Texoma

92°

92°

94°

96°

96°

98°

98°

100°

100°

102°

102°

34°

34°

32°

32°

TEXAS

NEW MEXICO

OKLAHOMA

ARKANSAS

LOUISIANA

Red River Basin

Base from U.S. Geological Survey 

1:1,000,000-scale digital data, 2014

0 50 100 MILES

0 50 100 KILOMETERS

Figure 8. Location of the Red River Basin.
20 Continuing Progress Toward a National Assessment of Water Availability and Use

Figure 9. U.S. Geological Survey Red River Basin Focus Area Study webpage. (From U.S. Geological Survey, 2017b)
Geographic Focus Area Studies 21

110° 108° 106° 104°

39°

36°

33°

30°

TX

OK

KS

AZ NM

UT CO

AREA OF DETAIL

0 50 100 MILES

0 50 100 KILOMETERS

Upper Rio Grande Basin 

Focus Study Area

Boundary

Base from ESRI digital data, 2017.

Hydrologic boundary units from U.S. Department of

Agriculture-Natural Resources Conservation Service,

U.S. Geological Survey, and Environmental Protection Agency, 2016.

World Geodetic System 1984

Elephant

Butte

Reservoir

Abiquiu

Lake

Cochiti

Lake

Figure 10. Location of the Upper Rio Grande River Basin.

Rio Grande Basin is an arid to semi-arid region where disputes 

over water shortages have occurred for more than 100 years. 

Basin features vary from alpine and forested mountains and 

river gorges in the Southern Rocky Mountains, to riparian forests (bosque) and the broad valleys and high desert of central 

New Mexico, to the Chihuahuan Desert along the boundary 

between Texas and Mexico.

The conjunctive use of water in the Upper Rio Grande 

Basin takes place under a myriad of legal constraints, including the Upper Rio Grande Compact between the States, 

an international treaty with Mexico, and several Federal 

water projects. The conveyance and use of surface water in 

the Upper Rio Grande River Basin is achieved through an 

engineered system of reservoirs, diversions, and irrigation 

canals. The region is experiencing a decrease in water supply 

and a trend toward less and earlier snowmelt due to extended 

drought and climate change. These conditions have led to 

diminishing snowmelt and groundwater recharge. At the same 

time, changes in climate and an extended period of drought 

have reduced reservoir water supplies, leading to increased use 

of groundwater for irrigation, municipal, and industrial uses. 

A decrease in water supply at a time of increasing demand 

from population growth and shifting agricultural cropping 

patterns means that current groundwater withdrawals exceed 

recharge rates. The growing gap between water supply and 

demand has resulted in continued conflict and litigation among 

Federal, Tribal, State, and local users. Quantification of key 

water-budget components as part of this study will support 

many regional efforts to understand and sustainably manage finite water resources in the Upper Rio Grande River 

Basin, including updates to the New Mexico State Water 

Plan (http://www.ose.state.nm.us/Planning/state_plan.php), 

the Rio Grande Transboundary Integrated Hydrologic Model 

(https://nm.water.usgs.gov/projects/program.areas/files/R-G.

transboundary.integrated.model.PNG), the Upper Rio Grande 

Water Operations Model (http://www.spa.usace.army.mil/
22 Continuing Progress Toward a National Assessment of Water Availability and Use

Missions/Civil-Works/URGWOM/), and the Rio Grande Basin 

of the USGS National Hydrologic Model (https://wwwbrr.

cr.usgs.gov/projects/SW_MoWS/index.html).

The Upper Rio Grande FAS is compiling and interpreting 

the spatial distributions and temporal trends of key wateravailability and -use components to help stakeholders address 

water issues. Compilation of water-use data by sector (such 

as public supply, irrigation, and domestic) from 1985 to 2015 

for the 22 HUC-8 subbasins will inform local, regional, and 

State water planning. Water losses from actual crop and landscape evapotranspiration are being quantified with a USGS 

remote-sensing-based model with Landsat satellite images, 

and verified with measured evapotranspiration data. Groundwater status and trends throughout the basin are being assessed 

through development of a basin-scale hydrogeologic framework, water-level surface and change maps, and geostatistical 

trend analysis. Improved snow-process modeling will provide 

more accurate estimates of snow accumulation, sublimation 

losses, and snowmelt rate and timing. Streamflow trend analyses and new base-flow separation methods are quantifying the 

connection between groundwater and surface water throughout the basin. Data and results from each component will be 

integrated in a regional calibration of the USGS national-scale 

watershed model, built on the precipitation runoff modeling 

system (PRMS) (Regan and others, 2018), which will provide 

a new tool to synthesize and visualize historical, current, and 

future water availability and use across the basin. 

The spatially distributed water-budget products of each 

component of this study will be compiled within a nationalscale database and integrated to improve understanding of 

interactions occurring within the basin. Summarized results 

will be publicly displayed on interactive maps at the “RealTime Map” tab on the project webpage, depicted in figure 11 

below (https://webapps.usgs.gov/watercensus/riogrande_fas/).

Figure 11. U.S. Geological Survey Upper Rio Grande River Basin Focus Area Study webpage. (From U.S. Geological Survey, 2017c)
Topical Studies 23

Topical Studies

Six topical studies key to the Water Census are discussed 

below. As described earlier, some topical studies, such as 

surface water, groundwater, evapotranspiration, and water use, 

provide uniform information about specific water-budget components for a consistent national framework of information 

vital to the understanding of water availability. Other topical 

studies provide research and innovative tools for environmental water science and drought science. For each topical study, 

this report explains the information needs and past and ongoing Water Census efforts to fill them. 

Surface Water

The SECURE Water Act calls for annual updates of 

river-basin flows and analysis of historical trends. The USGS 

Groundwater and Streamflow Information Program provides 

a strong and essential foundation for this type of streamflow 

information. The USGS operates more than 8,000 streamgages 

to provide information on floods, droughts, and current 

water availability across the United States. This network of 

streamgages provides real-time information and historical context for water-resources planning and assessment. For studies 

of trends in streamflow and water availability, long historical 

records are critical. 

Flow at Ungaged Locations

Because the streamgage network cannot provide direct 

observations of streamflow at every location of interest, 

information about streamflow at ungaged locations is needed. 

To meet this need, the USGS has long published information 

through its WaterWatch (https://waterwatch.usgs.gov) and 

StreamStats (https://water.usgs.gov/osw/streamstats/) web 

tools, which provide estimates of streamflow and streamflow 

statistics using well-established methods. The Water Census seeks to improve upon the information that is currently 

available for ungaged locations by providing estimated time 

series of daily streamflow for subwatersheds nationally. Initial 

exploratory work was conducted to assess the feasibility of 

using different statistical models for this type of work (Farmer 

and others, 2014, 2015). On the basis of these results, the most 

promising methods have been refined and used to develop 

models for the entire conterminous United States. These statistical models will be applied to ungaged locations throughout 

the Nation and the results will be publicly available in 2018. 

In addition to the statistical models, a daily deterministic precipitation-runoff model has been developed for the 

conterminous United States. This USGS model simulates 

the processes that generate runoff on the landscape (see fig. 

12) and routes the resulting flow through the river system. 

Because it simulates hydrologic processes with physically 

based code, this model can be used not only to simulate 

Precipitation

Solar radiation

Air

temperature

Hortonian runoff

Dunnian runoff

Interflow

Groundwater flow

Rain Rain

Snowmelt

Snowmelt

Groundwater sink

Recharge

Snow

Sublimation

Snowpack

Plant canopy interception 

Soil zone

Groundwater

Streamflow and lake routing

Impervious Depression

storage

Evaporation and

transpiration

Upslope surface

runoff and interflow

Figure 12. U.S. Geological 

Survey Precipitation Runoff 

Modeling System (Modified 

from Regan and others, 2018)
24 Continuing Progress Toward a National Assessment of Water Availability and Use

historical streamflow time series, but also to gain insight into 

all components of the water budget (such as soil-moisture storage or snowmelt in specific parts of the country). The model 

can also be used to explore “what-if” scenarios; for example, 

what if land use changes—how does that affect hydrologic 

processes and water availability? What if climate changes—

how will water supply be affected? A complete description 

of the USGS NHM is given by Regan and others (2017). For 

daily simulation, the USGS NHM-PRMS was built using the 

USGS Precipitation Runoff Modeling System (Markstrom and 

others, 2015) and a geospatial fabric that ties the model to the 

river network and observational data (Viger, 2014; Viger and 

Bock, 2014). Recent improvements to the USGS NHM-PRMS 

include improved parameterization of snowmelt, depression 

storage, and groundwater discharge. Improved methods for 

regional calibration of the model have also been developed 

to allow application at ungaged locations (Bock and others, 

2016; Markstrom and others, 2016). 

Figure 13 shows results for June 1, 2010, from the USGS 

NHM-PRMS built using PRMS version 5 and the default 

parameters published by Driscoll and others (2017). The 

river reaches are colored on the basis of whether flows were 

low, normal, or high for that time of year. For example, in the 

USGS NHM-PRMS simulation, the orange river reaches along 

the west coast are flowing at less than the 10th percentile for 

this date, whereas the blue reaches in the central United States 

are flowing at greater than the 90th percentile for this date. 

Additional results from the USGS NHM-PRMS will be available for download in FY 2018. 

Although most existing work is focused on the conterminous United States as a result of limitations in the available data for other states and territories, some work is also 

proceeding in Alaska and Hawaii. For example, an extension 

to PRMS to simulate glacial runoff was developed to enhance 

the model’s suitability for simulating runoff and streamflow in 

Alaska (Van Beusekom and Viger, 2016). In addition, ongoing 

EXPLANATION

Simulated stream-flow percentiles

Low

Less than 10 percent

10 to 24 percent

25 to 75 percent

76 to 90 percent

Greater than 90 percent

High

Simulated Stream Flow Percentiles

June 1, 2010

Figure 13. U.S. Geological Survey National Hydrologic Model-Precipitation Runoff Modeling System simulated streamflow for June 1, 

2010, using the default parameters and model setup described in Regan and others (2018) and Driscoll and others (2017). The colored 

stream reaches show the flow percentile in each reach relative to simulated flow throughout the 1980–2010 simulation period for that 

day of the year.
Topical Studies 25

studies of low flow in Hawaii will provide information on the 

limits of the streamgage network for transferring information 

to ungaged locations in the islands

For all models, the uncertainty in the modeled streamflow 

varies widely depending on the region. Accurate characterization of uncertainty can improve water-resource decision making, and quantification of these uncertainties is a critical next 

step in this work.

Analysis of Change in Streamflow

A second major activity of this component of the Water 

Census is to evaluate trends in streamflow over time. Changes 

in surface-water hydrology can result from a wide variety of 

causes, including changes in water-management strategies, 

land-use changes, and climate variability or change. Changes 

in hydrology can affect water availability for public supply, industry, power generation, or agricultural use, and can 

affect water quality and aquatic ecosystems. Characterizing 

trends in streamflow and developing a greater understanding of the causes of trends are therefore critical to understanding future water availability and conducting effective 

water-resources planning.

Many studies are based on streamgages included in two 

USGS products: the HydroClimatic Data Network (HCDN) 

(Slack and Landwehr, 1992; updated in Lins, 2012) and the 

GAGES-II dataset (Falcone, 2011). The HCDN designates 

a set of streamgages as suitable for study of the effects of 

meteorological conditions on streamflow. The GAGES-II 

dataset similarly designates a set of streamgages as being 

of “reference” quality, whose upstream watersheds are least 

disturbed by human modifications and diversions. GAGES-II 

also provides a set of basin characteristics that can be used for 

further analysis. Continued maintenance of a national dataset 

of such gages is necessary to allow scientists to efficiently 

conduct studies to detect and understand streamflow change. 

An update of the GAGES-II dataset is planned within the next 

several years.

Analyses of streamflow records have revealed temporal 

changes in some aspects of flow. For example, many river 

basins that are snow-dominated in winter have shown a shift 

toward earlier spring runoff peaks associated with snowmelt 

(Stewart and others, 2005; Hodgkins and Dudley, 2006; Dudley and others, 2016). Studies analyzing trends in the magnitude of peak flows have been less conclusive, with the most 

recent USGS publications showing that the largest detectable 

changes may be in smaller, more frequent flooding events 

rather than the largest, most catastrophic events (Hirsch and 

Ryberg, 2012; Hirsch and Archfield, 2015; Hodgkins and others, 2017b). These and other potential changes to streamflow 

resulting from various causes are the subject of continuing 

research. USGS analysis and data have been used in the EPA’s 

suite Climate Change Indicators (https://www.epa.gov/climate-indicators/climate-change-indicators-streamflow). These 

indicators are intended to show whether water-managementrelevant variables are changing over time.

Because streamflow is highly variable, analyzing trends 

in streamflow records is difficult. Moreover, changes in many 

different characteristics of flow may be important to different 

water managers or to different local ecological communities. 

For example, changes in seasonality of flow or day-to-day 

variability in flow may be just as important as shifts in annual 

mean streamflow, depending on the storage available in a 

particular water-resource system. Still other flow characteristics may be important for other specific purposes or concerns. 

Future studies will need to consider these factors and their 

effects on water management and water availability. USGS 

is also conducting work to better understand the causes of 

observed trends, which may arise from human modifications 

to upstream land use, river channels, and water management 

or water use, or from climate variability or change.

Groundwater

Any national assessment of water availability requires an 

assessment of the Nation’s groundwater reserves. The Water 

Census has leveraged a long history of groundwater studies 

and applied resources to accelerate ongoing regional studies 

to achieve this goal. These groundwater assessments provide 

consistent and integrated information that enables the resource 

to be viewed and understood on aquifer-wide scales that cross 

political boundaries.

Regional Groundwater Evaluations

For 2010, USGS estimated that groundwater was the 

source of 37 percent of water withdrawn for public supply, 

43 percent of water withdrawn for irrigation, and more than 

98 percent of water withdrawn for self-supplied domestic use 

(Maupin and others, 2014). Groundwater is especially important during periods of climatic drought because in many areas 

it is used as backup supply when reservoirs or rivers cannot 

meet demands. The USGS has long recognized the importance of groundwater to provide water resources to the Nation 

and has historically reported to the U.S. Congress and the 

Nation on the status of groundwater resources (Meinzer, 1923; 

McGuiness 1951, 1963; Sun and Johnston, 1994; Johnston, 

1999). In 2004, a program of regional groundwater availability 

studies was initiated under the former Groundwater Resources 

Program (Reilly and others, 2008). These studies are built 

around the estimation of groundwater budgets (Healy and others, 2007) for principal aquifer systems and typically quantify 

the response of the system to changes in pumping and variations in climate. In 2009, the Water Census funded an assessment of the glacial aquifer system, a principal aquifer system 

present in parts of 26 northern and midwestern states, and, 

in 2016, the regional groundwater availability studies from 

these programs were brought under the Water Availability and 

Use Science Program (WAUSP). The regional groundwater 

availability projects deliver information required for sound 

environmental decision making.
26 Continuing Progress Toward a National Assessment of Water Availability and Use

A recently completed regional groundwater availability 

study illustrates the information delivered through this effort 

(Masterson and others, 2016). The Northern Atlantic Coastal 

Plain aquifer system is one of the Nation’s smallest principal 

aquifers by area, but it is 7th largest in terms of population 

served and 13th largest in overall groundwater use. In additional to industrial and agricultural uses, it supplies drinking 

water for 40 percent of the population in the region, which 

extends from Long Island, New York, to northeastern North 

Carolina and from the Atlantic Ocean westward to the Fall 

Line, where the Coastal Plain sediments abut the Piedmont 

Physiographic Province. Results of this study highlight two 

opposite responses of aquifer systems to pumping (fig. 14). In 

the northern part of the study area—Long Island, New York, 

for example—pumping has not produced large declines in 

groundwater levels because the aquifer system is shallow and 

well connected to surface water, including streams, lakes, and 

the ocean. In this part of the study area, pumping reduces the 

A

A’

Study area

Chesapeake Bay

Delaware Bay

Long Island

CT

Sound NY

NEW

JERSEY

PENNSYLVANIA

MARYLAND WV

DC

VIRGINIA

DELAWARE

NORTH CAROLINA

ATLANTIC OCEAN

Pamlico Sound

Albemarle Sound

Base from U.S. Geological Survey digital data, 1:2,000,000 scale

Albers Equal Area Conic projection

Standard parallels 34°30' N and 41°30' N; central meridian 75°30' W 

North American Datum of 1983

0 50 100 MILES

0 50 100 KILOMETERS

78° 72°

39°

36°

75°

EXPLANATION

Percentage of total withdrawals

 and percentage of total depletion

1446

14

46

18 19

68 35

B

A’

A

B’

Figure 14. Northern 

Atlantic Coastal Plain 

aquifer system cumulative 

groundwater withdrawals 

(27.8 trillion gallons (Tgal)) 

and storage depletion 

(2.2 Tgal) as percentage 

of total water withdrawn 

and percentage of total 

groundwater depletion 

from 1900 to 2013. (From 

Masterson and Pope, 

2016, fig. 7)
Topical Studies 27

flow of groundwater to these surface-water features. In the 

southern part of the study area, including Virginia and North 

Carolina, the aquifers are deep and separated from streams 

and lakes by layers of material that impede groundwater flow. 

Consequently, pumping in this part of the system has produced large declines in groundwater levels. These declines 

can cause seawater to migrate into the aquifer, as well as land 

subsidence that may exacerbate the effects of sea-level rise on 

coastal communities.

The principal aquifer studies have examined the response 

of the systems to development and variations in climate, and 

through this work USGS is developing an understanding of 

how groundwater systems are responding to these drivers. 

The studies also are examining trends in groundwater levels across the country. More work is required to complete a 

national assessment, but example results from the Appalachian 

Plateaus (McCoy and others, 2015) and the glacial aquifer 

system (Hodgkins and others, 2017a) illustrate how longterm streamflow and groundwater data are being used to help 

understand the processes of the aquifer systems. Streamflow 

data may be analyzed to determine the component of the flow 

attributed to groundwater, base flow, and runoff from the land 

to the stream. Three sets of runoff and base flow time series 

show how individual stations may show little trend (fig. 15A), 

0

5

10

15

20

0

5

10

15

20

0

5

10

15

20

0

5

10

15

20

0

10

20

30

40

0

10

20

30

40

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Base flo

w, in inches

Runoff, in inches

Base flo

w, in inches

Runoff, in inches

Base flo

w, in inches

Runoff, in inches

A. 03051000 Tygart Valley River at Belington, WV

B. 03208500 Russell Fork at Haysi, VA

C. 03118500 Nimishillen Creek at North Industry, OH

EXPLANATION

Loess lines

Calendar year

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Calendar year

Figure 15. Time series of annual values of base flow and runoff at U.S. Geological Survey streamgaging stations A, 03051000 

Tygart Valley River at Belington, W.Va.; B, 03208500 Russell Fork at Haysi, Va.; and C, 03118500 Nimishillen Creek at North 

Industry, Ohio. (Modified from McCoy and others, 2015, fig. 34)
28 Continuing Progress Toward a National Assessment of Water Availability and Use

may show increases in base flow with little change in runoff 

(fig. 15B), or may show increases in both base flow and runoff 

(fig. 15C). Differences in behavior among these three stations has been attributed to the combined influence of climate 

and land-use change over the period 1920–2010 (McCoy and 

others, 2015). Groundwater-level data for wells in the glacial 

aquifer system east of the Rocky Mountains were examined 

for trends (fig. 16). Mostly positive trends are noted in the 

Northeast, indicating rising groundwater levels. In other parts 

of the system, wells show both positive and negative trends 

and many trends are significant if no underlying persistence in 

the data is assumed (Hodgkins and others, 2017a). Hodgkins 

and others (2017a) discuss these trends and the underlying 

nature of the data.

Composite Hydrographs

At the present time (2017), there are no regularly updated 

indicators for the Nation’s groundwater resources. In response 

to this need, the USGS developed “composite hydrographs” 

for many of the principal aquifers in the United States, utilizing groundwater-level measurements made by the USGS and 

available publicly in the National Water Information System 

(NWIS, https://waterdata.usgs.gov/nwis). A composite water 

level is a statistical representation of an average water level 

computed from multiple wells within each principal aquifer. 

There are currently 23 principal aquifers for which composite 

hydrographs have been calculated and are available to the public through the USGS Groundwater Watch webpages (https://

groundwaterwatch.usgs.gov/compositehome.asp).

The composite hydrographs may be used by local stakeholders who may be interested in whether the behavior of 

water in a local well is consistent with the average behavior 

of water in wells in the larger aquifer system. They also may 

be compared to other regional data to explore how the system 

is responding to climate or pumping. For example, the water 

level in the composite hydrograph of the Northern Atlantic 

Coastal Plain (NACP) principal aquifer is steadily decreasing, perhaps in response to the large increase in groundwater 

withdrawals from 1940 to 1980 (fig. 17A). Wet and dry years 

SD

IL

NE

KS

IA

MN

ND

WI

PA

IN

MI NY

MO VA

OH

ME

KY

CO WV

VT

NJ

RI

DE

NH

MD

MA

NC

CT

MT

WY

100° 90° 80° 70°

50°

45°

40°

Basemap of states from U.S. Geological Survey, 1:2,000,000, digital data

Albers Equal-Area Conic projection, standard parallels 29°30'

and 45°30', central meridian -96°, latitude of origin 23°

0 50 100 KILOMETERS

0 80 160 MILES

EXPLANATION

Trend (p is less than or equal to 0.05)

Decrease

Significant decrease

Increase

Significant increase

East Region

Central Region

West-Central Region

CANADA

Figure 16. Geographic distribution of trends in mean annual groundwater levels, 1984–2013 with the assumption of data 

independence. (Modified from Hodgkins and others, 2017b)
Topical Studies 29

as indicated by the Palmer Drought Severity Index (PDSI) 

also appear to lead to small increases or small decreases, 

respectively, in the median composite water level, as shown 

in figure 17B, which uses the NACP wells for Virginia and 

the PDSI for Virginia (National Oceanic and Atmospheric 

Administration National Centers for Environmental Information, 2017). In contrast to the slow decline in water levels 

in the NACP, the composite hydrographs for the Coastal 

Lowlands principal aquifer show an increase in water levels 

(fig. 18A,B). Examination of the pumping records and the 

PDSI for Texas (National Oceanic and Atmospheric Administration National Centers for Environmental Information, 

2017) indicates that the increase in groundwater levels is 

associated with a decrease in pumping in the greater Houston, 

Texas, area, which underwent large shifts in water use from 

groundwater to surface water beginning in 1976 in Harris and 

Galveston Counties (for pumping data and more information, 

see Kasmarek and Johnson, 2013). The recovery in the median 

composite water levels ceased in 2010 and water levels started 

to decline, presumably in response to severe drought conditions in the region from 2011 to 2015. Finally, the California 

Coastal Basins composite hydrographs appear to be strongly 

related to wet and dry conditions in California as indicated 

by the PDSI (National Oceanic and Atmospheric Association National Centers for Environmental Information, 2017). 

The median composite water level in these wells falls during 

times of drought and recovers during wet periods (fig. 19). 

These varying responses to the combined effects of climate 

and pumping from principal aquifers as indicated by the 

median composite water level show why groundwater-flow 

modeling as described in the preceding section (Regional 

Groundwater Evaluations) is so important. Through regional 

models, hydrologists can test hypotheses regarding the 

reasons for observed aquifer system responses and make predictions regarding system responses to future changes. This 

information can help water managers and stakeholders make 

informed decisions regarding groundwater-resource development (see Box C).

EXPLANATION

Estimated pumping

Median depth to water for North Atlantic 

Coastal Plain wells

EXPLANATION

Palmer Drought Severity Index

Median depth to water for North Atlantic 

Coastal Plain wells in Virginia

Depth to water, in feet Depth to water, in feet

Annual Palmer Drought Severity Index (PDSI)

for Virginia

Pumping, in million gallons per day

25

30

35

40

50

45

10

15

20

25

30

35

1940 1950 1960 1970 1980 1990 2000

1940 1950 1960 1970 1980 1990 2000

1,600

1,400

1,200

1,000

800

600

400

200

0

5

4

3

2

1

0

-1

-2

-3

A

B

Figure 17. Composite hydrograph and associated hydrologic information for the North Atlantic Coastal Plain principal aquifer, 

1940–2010.
30 Continuing Progress Toward a National Assessment of Water Availability and Use

EXPLANATION

Pumping, by county

Brazoria County

Montgomery County

Fort Bend County

Galveston County

Harris County

Palmer Drought Severity 

Index for Texas

Median depth to water

1975 2015

1975 2015

95

100

105

110

115

120

95

100

105

110

115

120

500

400

300

200

100

0

6

4

2

0

-2

-4

-6

1980 1985 1990 1995 2000 2005 2010

1980 1985 1990 1995 2000 2005 2010

Depth to water, in feet Depth to water, in feet

Annual Palmer Drought Severity Index (PDSI)

for Texas

Pumping, in million gallons per day

A

B

Figure 18. Composite hydrograph and associated hydrologic information for the Coastal Lowlands principal aquifer, 1975–2015.

2015

50

35

55

60

65

70

75

6

4

2

0

-2

-4

-6

1990 1995 2000 2005 2010

Depth to water, in feet

Annual Palmer Drought Severity Index (PDSI) for California

40

45

EXPLANATION

Palmer Drought Severity 

Index for California

Median depth to water

Figure 19. Composite hydrograph and associated hydrologic information for the California Coastal Basins principal aquifer 

for the period 1985–2015.
Topical Studies 31

Box C. Testimonial

“The USGS report, “Volcanic Aquifers of Hawai’i—Hydrogeology, Water Budgets, and Conceptual Models” is a valuable summary of the current knowledge of Hawai’i’s groundwater, and a source for updated 

estimates of groundwater recharge and water use. The USGS recharge estimates are an essential component 

of the aquifer sustainable yields developed by the State of Hawai’i Commission on Water Resource Management as part of the Water Resources Protection Plan of the Hawai’i Water Plan.”

—Jeffrey Pearson, Deputy Director, Hawai’i State Commission on Water Resource Management

Nu’uanu Pali Lookout, Oahu, Hawai’i. Photograph by Alan Cressler, U.S. Geological Survey.
32 Continuing Progress Toward a National Assessment of Water Availability and Use

Tools for Groundwater Availability—Model 

Sustainability

The primary tool used for quantitative analysis of 

regional groundwater systems is numerical modeling. Numerical models provide a holistic representation of the water-budget components of the Nation’s principal aquifers and enable 

forecasting of the responses of groundwater resources to future 

stress from groundwater development, land-use change, and 

climate variability (Dennehy and others, 2015). For more than 

50 years, the USGS has been a leader in the development and 

application of numerical modeling software for analysis of 

groundwater systems, and has made a long-term commitment 

to the development and maintenance of modeling software 

and ancillary tools that support the Water Census, the National 

Water Quality Assessment Project, and other USGS programs. 

The USGS also has developed a robust training program for 

its staff and other Federal, State, Tribal, and local partners in 

the use of its modeling software.

USGS software continually evolves to incorporate 

advances in hydrologic research and computer technology into 

operational tools that can better address the complex, interdisciplinary nature of water availability (see Box D). During 

the past 5 years, the USGS made advancements in many of its 

numerical modeling software, including its flagship groundwater-simulation code MODFLOW. Named “MODFLOW 6,” 

the code has been redesigned to provide greater flexibility 

to simulate regional- and local-scale groundwater systems 

simultaneously and for improved integration with other types 

of watershed, chemical-transport, and water-operations models 

(Hughes and others, 2017; Langevin and others, 2017). This 

new multiscale modeling approach will be a key component 

of the recently initiated groundwater-availability study of the 

Box D. Testimonials

“The MODFLOW suite of codes is the most 

widely used set of groundwater codes in the 

world and the standard for litigation purposes 

in the United States. MODFLOW has been 

applied to numerous and diverse field problems 

and is the focus of a series of international 

professional conferences (http://igwmc.mines.

edu/Conference.html).

—Anderson and others, 2015 (p. 100–101)

”

“MODFLOW gained broad acceptance 

because it is a versatile, well tested, well documented, and in the public domain.

—Fitts, 2013 (p. 360)

”

Coastal Lowlands aquifer system extending along the Gulf 

Coast from South Texas to the western part of the Florida panhandle. Advancements also have been made to the water-quality simulation capabilities of MODFLOW (Bedekar and others, 2016), which are needed to improve understanding of the 

suitability of groundwater resources for human and ecosystem 

needs. The Water Census also supported the application of the 

Soil-Water Balance software (Westenbroek and others, 2010) 

to various parts of the country and the Groundwater Toolbox 

(Barlow and others, 2014) to better quantify groundwaterbudget components such as recharge and discharge to streams. 

These codes have been applied to several of the regional 

studies, including the High Plains (Stanton and others, 2011, 

2013), Appalachian Plateaus (McCoy and others, 2015; Nelms 

and others, 2015) and glacial (fig. 20) aquifer systems. The 

USGS has also continued development of software tools to aid 

scientists in the process of building, calibrating, and visualizing model results (Welter and others, 2015; Bakker and others, 

2016; White and others, 2016), and to link hydrologic models 

with water-resource management and operations models (Ahlfeld and Barlow, 2013; Morway and others, 2016; Niswonger 

and others, 2017; White and others, 2018).

Increasing Access to Groundwater Information

In 2015, Congress provided increased funding to the 

USGS to address groundwater sustainability through open 

access to groundwater information, on the basis of work 

proposed through the White House Office of Science and 

Technology Policy and as required by the 2016 USGS Public 

Access Plan (U.S. Geological Survey, 2016). Through the 

Water Census, the USGS has enhanced access to its groundwater models and borehole geophysical logs. Implementation 

of consistent and standardized approaches for archiving and 

public release of USGS models and geophysical data makes 

these important and valuable products accessible, discoverable, and usable by USGS scientists, cooperators, academia, 

and the public, and illustrates the leadership provided by the 

USGS in this area.

Since 1993, the USGS has required that groundwater 

models developed as part of USGS studies be archived and 

made available to the public upon request. These requirements 

ensure that the data and related information that compose the 

models remain available to support and validate model results 

reported in USGS publications, and that working versions of 

all models are available for future scientific use. During FYs 

2016 and 2017, the USGS developed an approach and webpage to assist USGS scientists in the public release of groundwater models on the DATA.GOV cataloging site (https://catalog.data.gov/dataset?q=usgsgroundwatermodel), including the 

release of several completed regional groundwater-availability 

studies; work also continues on the development of methods 

to display model results through USGS web pages. During FY 

2017, the USGS publicly released “GeoLog Locator” (https://

webapps.usgs.gov/GeoLogLocator/#!/) (fig. 21), which is 

a web-accessible, map-based viewing and retrieval tool to 
Topical Studies 33

MT

CO

KS

UT

SD

IL

WY

NE

IA

MN

ND

WI

MO

PA

IN

MI

NY

VA

OH

KY

ME

WV

MI VT

NH

MD

MA

CT

DE

NY

NJ

RI

Lake Superior

Lake Michigan

Lake

Huron

Lake Erie

Lake Ontario

11 0 ° 1 0 0 ° 9 0 ° 8 0 ° 7 0 °

4 5 °

4 0 °

C A N A D A

Base modified from Esri 1:70,000, digital data, 2009,

U.S. Geological Survey, 1:2,000,000, digital data,

Albers Equal-Area Conic projection, standard parallels 29°30' 

and 45°30', central meridian -96°, latitude of origin 23°

0 130 260

0 130 260

MILES

KILOMETERS

EXPLANATION

Glacial Aquifer SWB mean annual potential 

recharge rate, in inches per year

0 to 3.00

3.01 to 6.00

6.01 to 9.00

9.01 to 12.00

12.01 to 15.00

15.01 to 18.00

18.01 to 21.00

21.01 to 24.00

24.01 to 27.00

27.01 to 43.00

Area of enlargement

Figure 20. Preliminary long-term average (1980–2011) groundwater-recharge rates estimated for the glacial 

aquifers of the United States by use of the U.S. Geological Survey (USGS) Soil-Water-Balance (SWB) model as part 

of the USGS Glacial Aquifers Groundwater-Availability Study. Recharge rates are lowest in the western United States 

(red and orange areas) and generally increase eastward (yellow and green areas). (Modified from Westenbroek and 

others, 2010 )

Figure 21. Sites in New York State for which borehole-geophysical logs are available through the U.S. Geological 

Survey GeoLog Locator. (From U.S. Geological Survey, 2017e)
34 Continuing Progress Toward a National Assessment of Water Availability and Use

publish USGS borehole geophysical logs. The initial release 

of GeoLog Locator provides the public with access to nearly 

7,000 geophysical logs—many for the first time. The application uses underlying data from nearly 17,000 logs stored 

within an internal database, and provides the necessary review 

and approval flags to assure the proper workflow for publication of the data.

National Groundwater Monitoring Network

The SECURE Water Act, Section 9507, provided legal 

authority for the USGS to implement the National GroundWater Monitoring Network (NGWMN). The NGWMN was 

developed through the efforts of the Advisory Committee on 

Water Information (ACWI, https://acwi.gov/), Subcommittee 

on Groundwater (SOGW, https://acwi.gov/sogw/index.html). 

The goal of the NGWMN is to integrate groundwater-level 

and groundwater-quality data collected by Federal, State, and 

local agencies to address groundwater availability questions at 

the principal aquifer scale (https://water.usgs.gov/ogw/aquifer/

map.html). 

The SOGW created a design for the NGWMN in the 

document “A National Framework for Ground-Water Monitoring in the United States” (https://acwi.gov/sogw/ngwmn_

framework_report_july2013.pdf). In 2009, five pilot studies 

were conducted to test the concepts of the proposed network. 

As part of the pilot effort, a NGWMN Data Portal was developed to share NGWMN data, and feedback from the pilot 

participants was used to update the original network design 

described in the Framework document. Information about the 

NGWMN and links to the NGWMN Data Portal are available 

at https://cida.usgs.gov/ngwmn/. 

After successful piloting, Congressional funds were 

appropriated in FY 2015 to support implementation of the 

NGWMN. These initial funds allowed 11 states to become 

new data providers to the NGWMN, or to complete work 

initiated during the pilot studies. A summary of the projects 

supported during FY 2015 are available at https://cida.usgs.

gov/ngwmn/doc/NGWMN_FY15_ProjectSummary.pdf. A 

competitive process for future funding opportunities for data 

providers was initiated in FY 2015, and the National GroundWater Monitoring Network Program Board was formed to 

assist in evaluation of NGWMN proposals, as recommended 

in the Framework document. The NGWMN Program Board 

is composed of data providers, Federal agencies, and SOGW 

members. In FY 2016, support was provided to 24 agencies 

to become new data providers or to improve or enhance their 

existing NGWMN sites. This collaborative funding approach 

increases the number of data providers, increases the number 

of groundwater-level and groundwater-quality sites in the 

NGWMN, reduces data gaps, and improves the overall quality 

of data supplied by NGWMN data providers. A summary of 

the projects supported during FY 2016 are available at https://

cida.usgs.gov/ngwmn/doc/NGWMN_FY16_ProjectSummary.pdf. In 2017, awards were made to 19 State agencies. A 

summary of the projects supported during 2017 is available at 

https://cida.usgs.gov/ngwmn/doc/NGWMN_FY17_ProjectSummary.pdf.

To date (2017), these projects have resulted in NGWMN 

growth from the 5 pilot project data providers in 2014 to 19 

current data providers, with current projects supporting an 

additional 12 agencies working to become NGWMN data 

providers. The NGWMN has also supported data providers 

to maintain their connection to the Portal and enhance data 

available from their network wells. The number of wells in the 

NGWMN has increased from 2,831 groundwater-level sites in 

early 2015 to 5,792 sites in July 2017. The number of groundwater-quality sites has increased from 534 in early 2015 to 

1,325 in July 2017. 

The SECURE Water Act also authorized the USGS to 

expand the groundwater Climate Response Network (PL 111-

11, Sec 9507 (b)(3)(B)) into each of the 373 Climate Divisions 

in the United States and its territories. The Climate Response 

Network (CRN) provides near-real-time, continuous groundwater levels in wells and springs designed to monitor the 

effects of droughts and other climate variability on groundwater levels. Expansion began with the appropriation received in 

FY 2015. As of 2017, Federal funds have supported instrumentation of 200 wells and springs, and instrumentation of 33 

additional sites is in progress.

Brackish Groundwater

Secure, reliable, and sustainable water resources are 

fundamental to the Nation’s food production, energy independence, and ecological and human health and well-being. At 

any given time, water resources are under stress in selected 

parts of the country. In some regions, particularly arid and 

semiarid regions, water supply is not adequate to meet 

demand, and severe drought intensifies the stresses affecting water resources. If drought conditions continue, water 

shortages could adversely affect human health, economic 

well-being, and minimum water flows necessary to maintain 

ecosystem health. These risks can potentially be mitigated, at 

least in part, by developing new water-supply sources.

Advances in desalination technology and increases in 

demand for uses that do not need high-quality water (for 

example, mining, oil and gas development, and thermoelectric power generation) have led states such as Texas and 

California to turn to brackish groundwater as an alternative 

to freshwater. Brackish water refers to water that contains 

more dissolved salts and minerals than freshwater, but less 

than seawater (dissolved-solids concentration between 1,000 

and 10,000 milligrams per liter [mg/L]). Brackish groundwater resources can potentially meet many water-resource 

needs. Identification of new sources of brackish groundwater, 

especially in areas with limited freshwater resources, has 

the potential to enhance the Nation’s water security. In some 

areas, the use of brackish groundwater could reduce effects on 

freshwater resources commonly used for drinking, business, 
Topical Studies 35

and recreational activities. The strategic development and 

treatment of brackish groundwater to produce new water supplies for a variety of uses could help water-stressed regions 

stretch their limited freshwater supplies. The use of brackish 

groundwater, however, has been hampered by the lack of basic 

knowledge concerning its geographic distribution, accessibility, chemical composition, use, treatment requirements, and 

effects on the environment.

The USGS completed the National Brackish Groundwater Assessment to provide updated information about brackish 

groundwater as a potential resource to augment or replace 

freshwater supplies. For the national brackish groundwater 

assessment, brackish groundwater was quantitatively defined 

as having a dissolved-solids concentration between 1,000 and 

10,000 mg/L. Study objectives were to consolidate available 

data into a comprehensive database of brackish groundwater resources in the United States and to produce a summary 

report highlighting the distribution, physical and chemical 

characteristics, and use of brackish groundwater resources. 

The assessment is contained in U.S. Geological Survey Professional Paper 1833 entitled, “Brackish groundwater in the 

United States” (Stanton and others, 2017). This assessment 

was authorized by section 9507 of the Omnibus Public Land 

Management Act of 2009 (42 U.S.C. 10367), passed by Congress in March 2009. Funds supporting the assessment were 

appropriated in FYs 2012 through 2017 and totaled $2.2 million over that time. 

This new assessment builds on a 1965 study (Feth, 1965) 

which, for more than five decades, has served as the primary 

source of information on the national distribution of brackish 

groundwater. By incorporating data from more than 380,000 

sites, compared to about 1,000 for the 1965 study, the 2017 

assessment provides more comprehensive, nationwide data on 

the quantity and quality of brackish groundwater across the 

country. This compilation includes information such as the 

chemical composition of the water and the amount of water 

yielded by wells, which are necessary for understanding the 

potential—at the National and regional scales—for expanding 

brackish groundwater development and for informing decision 

and policy makers.

Data from the assessment indicates that brackish groundwater can be present at some depth within 3,000 feet below 

land surface in every state except New Hampshire and Rhode 

Island. A conservative estimate for the volume of brackish 

groundwater underlying the country is more than 35 times 

the amount of fresh groundwater currently used each year 

(Stanton and others, 2017). Consequently, it is reasonable to 

consider brackish groundwater a substantial water resource 

available for use by the Nation.

In addition to limitations caused by high concentrations 

of salts and minerals, the presence of other chemicals can 

have important implications for the feasibility, treatability, and 

associated cost of using brackish groundwater. The study identified specific chemicals in brackish groundwater that require 

specialized treatment beyond that required to reduce overall 

salt content.

Despite the availability of this new information, there is 

still more to uncover on sustainable development of brackish 

groundwater. For many locations, data have not been collected 

for depths greater than 500 ft. The next challenge with regard 

to possible development of brackish groundwater is to acquire 

detailed information for specific aquifers that contain brackish 

groundwater, which is needed to evaluate sustainable brackish 

groundwater development, including the effects of brackish 

groundwater withdrawals on adjacent water resources. This 

assessment could be accomplished through the compilation 

of additional existing data, collection of new data, and use of 

additional tools for evaluating these potential resources.

Evapotranspiration

Evapotranspiration (ET) is the upward flux of water 

from the land surface to the atmosphere, and is a combination of evaporation from the soil and transpiration by plants. 

An essential component of water-budget determinations for 

water availability, ET is also a fundamental variable of water 

use, especially for irrigation, and has important implications 

for administration of water rights and river-basin compacts. 

Historically, reliable estimation of ET required site-specific 

field measurements made by using specialized instruments. 

However, because these measurement sites represent conditions only in their immediate vicinity, quantifying ET over 

broad areas such as irrigation districts, river basins, or states is 

a difficult task. Substantial progress has been made in meeting this challenge by using remote sensing to make estimates 

of ET across the landscape. USGS is applying its satellite 

remote-sensing resources and expertise to quantify ET for the 

Water Census by developing and implementing the Operational Simplified Surface Energy Balance Model (SSEBop) 

(Senay and others, 2013).

A new ET dataset has been constructed from these data 

for the entire conterminous United States (Senay and others, 

2013). Although temperature data are collected daily by satellite, energy-budget calculations are made on 8-day composite 

images to reduce problems of cloud cover. These results, in 

turn, are accumulated into monthly, seasonal, and annual 

summaries of ET from 2000 to 2015. Crop water use has been 

estimated by using this dataset along with geographic information system (GIS) layers and remote-sensing imagery for 

identification of irrigated cropland (Savoca and others, 2013). 

Monthly and annual GIS layers (2000–15) are posted at the 

USGS Geo Portal site at https://cida.usgs.gov/gdp/. Anomalies in recent ET for the conterminous United States are also 

available online to assist with water management and drought 

monitoring (https://earlywarning.usgs.gov/useta/etaseasonal.

php; see fig. 22).

Water-use reporting (irrigation consumptive use) requires 

estimates of actual ET (ETa) at the scale of agricultural fields. 

USGS Landsat thermal infrared imagery, with a resolution of 

60 to 120 meters (197 to 394 ft), was used for this purpose in 

the Colorado River Basin (Senay and others, 2016). Results 
36 Continuing Progress Toward a National Assessment of Water Availability and Use

Figure 22. Seasonal cumulative evapotranspiration anomaly for the conterminous United States, April 1–October 30, 2016. (From 

U.S. Geological Survey, 2017d)

are available for one complete year at a monthly time step. 

Application of Landsat data to ET estimation has been completed for four additional Focus Area Studies—the Delaware, 

ACF, Rio Grande, and Red River Basins. Stakeholders have 

shown a strong interest in using these detailed estimates. With 

the experience gained from these studies, along with enhanced 

computing power, USGS is preparing to estimate ET at the 

Landsat scale for the entire conterminous United States. This 

new dataset will be available online within a few years. Future 

work will also include improved parameterization for complex 

terrain and uncertainty estimation. 

The California Department of Water Resources and 

other stakeholders participating in the National Integrated 

Drought Information System (NIDIS, https://www.drought.

gov/drought/what-nidis) California pilot study led by NOAA 

identified information on fallowed land as being particularly 

important to understanding effects of drought on water use. 

In response, USGS developed the Fallow-land Algorithm 

based on Neighborhood and Temporal Anomalies (FANTA) to 

quantify fallowed-land extent by using remote-sensing imagery (Wallace and others, 2017). The FANTA method compares 

current greenness and historical greenness of individual pixels 

derived from satellite imagery to classify land as fallowed. 

Fallowed land assessment is an important tool for state water 

resource agencies, enabling them to more accurately assess the 

need for irrigation water in the current year. The method was 

applied to the State of California for 2001–15, with verification by field visits to more than 450 sites in 2014. Work is 

ongoing to extend the method for use in other irrigationdependent agricultural regions of the United States.

Water Use

The SECURE Water Act places direct emphasis on 

assessment of the use of surface water and groundwater for 

understanding the demand side of water availability. As further 

evidence of the interest in water use by the U.S. Congress, 
Topical Studies 37

Section 9508 (d) (3 and 4) places specific reporting requirements on the USGS with regards to water use. Improved information is needed on withdrawal, conveyance, consumptive 

use, and return flow by sector of use as well as on the factors 

that influence these components of water use. Such information will allow water managers and planners to make more 

effective decisions for the future. 

The term “water use,” in a restrictive sense, refers to 

water that is withdrawn by humans for a specific purpose, such 

as public supply, irrigation, or thermoelectric-power cooling. 

More broadly, water use pertains to the interaction of humans 

with and their influence on the hydrologic cycle, and includes 

elements such as water withdrawals, delivery, consumptive 

use, wastewater release, reclaimed wastewater, return flow, 

and instream use. The term “water withdrawals” in this report 

refers to the removal of water from a groundwater or surfacewater body that is subsequently put to a beneficial use.

In addition to the many accomplishments that follow, in 

2016, the USGS developed an interactive data visualization 

that shows freshwater-use by state every 5-years from 1950 to 

2010 (https://owi.usgs.gov/vizlab/water-use/). This tool allows 

users to discover the most comprehensive national-scale data 

on water use for the United States. The USGS compiles and 

estimates this water-use information in cooperation with 

State, Federal, and local agencies. The visualization presents 

estimates by categories including public supply, irrigation, and 

thermoelectric power. The visualization highlights how water 

use differs from one part of the country to another. Water withdrawal for thermoelectric power generation are most prominent in the eastern half of the United States while irrigation 

water use is dominant in the west. The data and software for 

the visualization are publicly available and open source.

Water-Use Compilation 2015

Every 5 years since 1950, the USGS has compiled a 

national estimate of water use by various categories and areas 

for the United States, the District of Columbia, Puerto Rico, 

and the U.S. Virgin Islands. The 2015 compilation is the 14th 

report in this series and provides the most comprehensive 

assessment of water withdrawals from available resources 

(groundwater and surface water; fresh and saline) for eight 

categories of use: public supply, domestic, irrigation, livestock, aquaculture, industrial, mining, and thermoelectric 

power. This product, however, is the first since 1995 to also 

include consumptive use for two of the largest categories of 

use, irrigation and thermoelectric power. In 2016 and 2017, 

the USGS made a deliberate effort to rapidly issue available 

information on 2015 water use. Through this effort, public 

supply withdrawals, domestic water use, and total population 

information for 2015 were released both as a USGS Open-File 

Report (Dieter and Maupin, 2017; https://doi.org/10.3133/

ofr20171131) and a data release (Dieter and others, 2017; 

https://doi.org/10.5066/F7TB15V5) in October of 2017. These 

products documenting water use in 2015 represent the most 

rapid data release possible given the project capabilities. The 

national totals and trends report is produced when data for all 

categories have been approved and summarized. 

Data are compiled and synthesized using local, State, and 

Federal data sources, as well as data provided by the National 

Water Use Science Project (NWUSP). These data are checked 

and verified, then entered into the USGS Aggregated Water 

Use Database System (AWUDS), which has the capability 

to store data by area (State, county, watershed, and aquifer), 

and year for each state. Data required for the compilation are 

reported at the county level as annual average withdrawals in 

million gallons per day. The AWUDS database is the source of 

the data available online at USGS Water Data for the Nation 

(http://waterdata.usgs.gov/nwis), which displays the best available water-use data from AWUDS.

The 5-year compilations present water-use statistics, 

aggregated by county, state, and the entire country for the 

target year, for all eight categories of water use (public supply, domestic, irrigation, livestock, aquaculture, self-supplied 

industrial, mining, and thermoelectric power). In addition, 

the compilation presents an analysis of trends in water use 

from 1950 through the target year for each category. The most 

recent published compilation as of the time of this report 

is “Estimated Use of Water in the United States in 2010” 

(Maupin and others, 2014). By presenting this information, the 

compilations fulfill two of the major reporting requirements of 

the SECURE Water Act, sections 9508 (d) (3 and 4), relating 

to the withdrawal and use of surface water and groundwater 

by various sectors and the significant trends relating to each 

water-use sector.

Water-Use Data and Research Program

The SECURE Water Act, Section 9508 (c), provided legal 

authority for the USGS to establish the Water Use Data and 

Research Program (WUDR). The overall goal of the WUDR is 

to improve water-use data (in the broad sense) for the United 

States by providing resources to State water-resource agencies 

or their designees, to improve their water-use information. 

This program will improve the accuracy of estimates of water 

use in the United States, and provide information needed to 

manage water resources and (or) forecast future water-use 

needs. Improved data will also allow the USGS, other agencies, scientists, and researchers to better understand which categories account for the most water, and work toward reducing 

the “footprint” of water use in the high-use categories.

Much of the data used to compile water-use estimates 

at the national level is reported to State agencies throughout 

the United States. The WUDR Program promotes cooperative 

work with State agencies by providing funding to them for 

improving water-use data collection, methods development, 

database development and data storage, and quality-assurance 

activities. Improvements at the State level will, in turn, 

improve estimates at the national level. WUDR cooperative 

agreements also require collaboration between State agencies 
38 Continuing Progress Toward a National Assessment of Water Availability and Use

and USGS offices nationwide by requiring data from funded 

projects be incorporated into USGS databases. 

Between FY 2015 and FY 2017, 44 states, American 

Samoa, the District of Columbia, and the U.S. Virgin Islands 

each received $26,000 through WUDR to describe current 

water-use information in each state or district, as well as the 

priorities for improving water-use information and possible 

approaches to addressing those priorities (fig. 23). 

In FY 2016, 18 states (fig. 24) received WUDR funds 

totaling $1.4 million through a competitive process to address 

priorities for improving water-use information. A list of states 

with project titles is available online at https://water.usgs.

gov/wausp/wudr/awardsFY16.html. In FY 2017, 15 states 

(fig. 25) received WUDR funds totaling $1.32 million through 

a second competitive process. A list of states with project titles 

and summaries is available online at https://water.usgs.gov/

wausp/wudr/awardsFY17.html. The projects in both FY 2016 

and FY 2017 include improving database systems, improving 

reported data quality, and working to acquire more robust data.

The WUDR Program has led to many discussions 

between State agencies and USGS, both in the exchange 

of ideas with respect to which water-use data need to be 

improved, and in improved data sharing. Additionally, WUDR 

listening sessions were held in three locations across the 

United States (Salt Lake City, Utah; Chicago, Illinois; and 

Tuscaloosa, Alabama) in 2015; during those sessions, State 

agencies identified the need to share expertise among State 

agencies and the USGS. (Session notes are available online 

at https://water.usgs.gov/wausp/wudr/stakeholders.html). To 

address this need, a monthly webinar series, the USGS Water 

Use Open Forum (WUOF), began in February 2016, and since 

then 15 1-hour recorded sessions have been held (https://water.

usgs.gov/wausp/wudr/wu-forum.html). The WUOF provides 

an excellent opportunity for State agencies to share information on all aspects of water-use data, from database systems 

to estimation methods, reported data, and so forth, with other 

states and the USGS. All of these aspects of the WUDR 

program actively build collaboration and cooperation between 

State agencies and the USGS.

Thermoelectric Water Use

Water withdrawals for thermoelectric-power generation, 

used predominantly in the cooling process, are the largest in 

the United States, accounting for 45 percent of total withdrawals in 2010. Historically, thermoelectric cooling water withdrawals have been reported by the Department of Energy’s 

(DOE) Energy Information Administration (EIA) and state 

regulatory agencies with responsibility for thermoelectric 

generating plants. These agencies, however, have different 

reporting, methods, and data sources requirements, which have 

resulted in incomplete datasets, inconsistent water-use data, 

and uncertain data quality.

TEXAS

UTAH

MONTANA

CALIFORNIA

ARIZONA

IDAHO

NEVADA

OREGON

KANSAS

WYOMING

NEW MEXICO

ILLINOIS

OHIO

MISSOURI

MINNESOTA

NEBRASKA

OKLAHOMA

ALABAMA

ARKANSAS

WASHINGTON

WISCONSIN

NORTH DAKOTA MAINE

VIRGINIA

INDIANA

MICHIGAN

MISSISSIPPI

KENTUCKY

LOUISIANA

TENNESSEE

PENNSYLVANIA

NORTH

CAROLINA

 WEST 

VIRGINIA

MICHIGAN

VERMONT

MARYLAND

 NEW 

JERSEY

NEW HAMPSHIRE

MASSACHUSETTS

CONNECTICUT

DELAWARE

RHODE ISLAND

EXPLANATION

ALASKA

AMERICAN

SAMOA

GUAM

HAWAII PUERTO RICO

U.S. VIRGIN ISLANDS

DISTRICT OF

COLUMBIA

States that received $26,000 funding

2015 (41 states)

2016 (4 states)

(2017) American Samoa 

and U.S. Virgin Islands

Figure 23. States that received funds ($26,000) from the Water Use Data and Research Program to describe current 

water use and identify priorities for improving water-use data in their state.
Topical Studies 39

TEXAS

MONTANA

KANSAS

NEW MEXICO

ILLINOIS

MINNESOTA

OKLAHOMA

WASHINGTON

NORTH MAINE

DAKOTA

INDIANA

TENNESSEE

PENNSYLVANIA

NORTH

CAROLINA

MISSISSIPPI

DELAWARE

EXPLANATION

ALASKA

AMERICAN

SAMOA

GUAM

HAWAII PUERTO RICO

U.S. VIRGIN ISLANDS

DISTRICT OF

COLUMBIA

Competitive award recipients, 

fiscal year 2016 (18 states)

Figure 24. States that were awarded funds from the Water Use Data and Research 2016 Competitive Program to 

improve water-use data and research in their state.

NEVADA

UTAH

VIRGINIA

MONTANA VERMONT

KANSAS

ILLINOIS

MISSOURI

IDAHO

NEBRASKA

 WEST 

VIRGINIA

KENTUCKY

PENNSYLVANIA

MASSACHUSETTS

CONNECTICUT

EXPLANATION

ALASKA

AMERICAN

SAMOA

GUAM

HAWAII PUERTO RICO

U.S. VIRGIN ISLANDS

DISTRICT OF

COLUMBIA

Competitive award recipients, 

fiscal year 2017 (15 states)

Figure 25. States that were awarded funds from the Water Use Data and Research 2017 Competitive Program to 

improve water-use data and research in their state.
40 Continuing Progress Toward a National Assessment of Water Availability and Use

From FY 2011 to FY 2013 the USGS, in collaboration 

with the EIA, developed models for estimating thermoelectric 

water withdrawals that provide estimates that are independent 

from EIA plant-operator-reported data. The NWUSP, as part 

of the WAUSP, developed these models and has produced 

estimates of withdrawal and consumptive use for approximately 1,300 thermoelectric power plants in the United 

States to support the USGS 2010 and 2015 national water-use 

compilations. The models are based on linked heat-and-water 

budgets that are constrained by power-plant fuel consumption 

and electricity production, generation technologies, coolingsystem technologies, and environmental variables. The 

models provide a consistent method for estimating withdrawals and consumptive use across all plants in the United States. 

The methods for estimating thermoelectric consumptive use 

were published in Diehl and others (2013); the withdrawal 

methods plus the 2010 model estimates for withdrawals and 

consumptive use were published in Diehl and Harris (2014).

In addition to withdrawal and consumptive-use estimates, the models also provide thermodynamically plausible 

ranges of withdrawal and consumptive use for each plant, 

thereby providing a quality-assurance check for the EIA 

plant-operator-reported data, as well as for the USGS compilation data that may be obtained from State agencies and 

(or) plant operators. A journal article and associated data 

release product, which shows a three-way comparison among 

the 2010 USGS model estimates, the EIA-reported data, and 

the USGS compilation data, were published in Harris and 

Diehl (2017a,b).

USGS will continue to collaborate with EIA to improve 

reported data, which in turn improves the thermoelectric 

models. In 2016, EIA published a tool which allows users to 

relate boilers, generators, and cooling systems to one another 

at each plant. USGS requested this tool to enhance EIA data 

for the models. The tool greatly improved the models by more 

accurately mapping the heat path in a plant from fuel consumption to cooling system.

This research has resulted in continued collaboration 

among USGS, EIA, DOE, the national energy laboratories, 

and other Federal and State agencies on matters related to 

water and energy issues. 

Water Use by Principal Aquifer, 2015

The Water Census has improved the understanding 

of groundwater resources with regional analysis of principal aquifers that collectively account for a majority of the 

Nation’s total groundwater withdrawals (https://water.usgs.

gov/ogw/gwrp/activities/gw-avail.html). However, groundwater studies continue to lack water-use data that satisfy needs at 

the regional and local levels. To fill these data needs, groundwater withdrawals reported for the USGS national compilation for 2015 will be used to estimate water use by principal 

aquifer for each county in the United States. 

Sixty-six principal aquifers in the United States have 

been defined as regionally extensive aquifers, or aquifer systems, with the potential to be used as sources of water of suitable quality and quantity to meet various water needs (Maupin 

and Barber, 2005). In 2000, withdrawals from these principal 

aquifers were estimated for three major categories (public 

supply, self-supply industrial, and irrigation) that accounted 

for more than 98 percent of all groundwater withdrawals for 

all categories of use in the United States (Maupin and Barber, 

2005). The 2000 estimates were reported as statewide totals 

by category and principal aquifer, which is a very broad and 

high-level scale assessment. For the new effort, a USGS team 

will use the 2015 county groundwater withdrawals by category, along with water-well records, aquifer maps, and other 

ancillary data, to estimate withdrawals by principal aquifer 

for each county for all major categories reported in the 2015 

compilation. Along with the estimates, the team will develop 

and document a variety of methodologies and protocols for 

estimating withdrawals by principal aquifer that will cover a 

variety of situations related to data availability in a state. A 

long-term goal of the WAUSP is to report national groundwater use for all categories by principal aquifers at a high spatial 

and temporal resolution. This ongoing study is collaborating 

and coordinating data collection and reporting efforts for the 

regional aquifer assessment with the NWUSP.

wateRuse R Programming Tools

Using open-source programming software (R), the USGS 

has developed a package of quality-assurance/quality-control 

(QA/QC) and visualization tools designed specifically to work 

with NWUSP aggregate water-use data. This tool enables 

users, absent of first-hand knowledge of the NWUSP aggregated water-use data, to upload, plot, and visualize the data 

with multiple spatial, temporal, and categorical specifications. 

Data can be displayed using simple map plotting functions for 

multiple years, categories, and areas, such as counties. The R 

programming package (wateRuse) is available as an opensource package from the USGS (http://usgs-r.github.io/) and 

on github (https://github.com/USGS-R/wateRuse). 

Irrigation Consumptive Use

One of the priorities of the Water Census for water-use 

science and data improvements is to develop scientifically 

sound and consistent methods for estimating consumptive use 

on irrigated lands. Irrigation consumptive-use estimates have 

not been provided nationally as part of NWUSP 5-year compilations since 1995. Irrigation is not the largest category with 

respect to withdrawals (thermoelectric use accounts for more 

water withdrawals than irrigation), but more water is used 

consumptively (evaporated, transpired, or locked up in crop or 

soil material and otherwise not available for immediate use) 
Topical Studies 41

for irrigation than for all other water-use sectors combined. In 

1995, irrigation consumptive use was estimated to be at least 

20 times that of thermoelectric consumptive use (Solley and 

others, 1998). Beginning in 2015, the NWUSP worked collaboratively with other USGS scientists to develop irrigation 

consumptive-use estimates (expressed as actual evapotranspiration (ETa) and considered equivalent to consumptive use) by 

using remote-sensing technologies and geospatial applications. 

Scientists from the USGS Earth Resources Observation and Science (EROS) Center have provided the NWUSP 

with 2015 estimates of ETa for the conterminous states plus 

Hawaii, based on 1-kilometer (0.621-mile) resolution MODIS 

satellite data analyzed by using the SSEBop model parameterized for operational applications (Senay and others, 2013). 

These values represent the spatial and temporal variation of 

the consumptive use of water across the landscape, depicted as 

average depth (in inches).

The SSEBop method results in ETa estimates that incorporate the spatial and temporal variation that occurs naturally 

throughout the growing season. This national coverage of ETa 

is scientifically defensible, is consistently generated on the 

basis of remotely sensed data, and can be used as a foundation 

for the 2015 compilation of irrigation consumptive use. This 

analysis has shown the importance of the addition of both a 

detailed GIS layer of irrigated lands throughout the United 

States and implementation of the increased spatial resolution 

provided by the use of LANDSAT imagery (30-meter [98.4-ft] 

resolution) for future water-use compilation efforts.

Water Use Research Funded by Cooperative 

Matching Funds 

As discussed earlier in the Coordination and Collaboration section of this report, the WAUSP is providing as much as 

$2 million per year of Cooperative Matching Funds targeted at 

water use research projects. The following are two examples 

of projects with state agencies that are being jointly funded to 

advance this area of research.

In the State of Georgia, the USGS is working with the 

Georgia Environmental Protection Division to build on previous work related to the assessment and accounting of 2015 

water use information. These assessments involve geospatial analyses, database tools, and comparisons with related 

published information for the purpose of (1) quantifying water 

withdrawals, deliveries, and returns by county, hydrologic 

unit, aquifer, and water planning region; (2) identifying categories of water use or regions of the state where refinements 

to water use source data are needed for improving accuracy of 

reported water use information; and (3) identifying sources of 

information that, if collected at a different spatial or temporal 

scale, would allow for a more complete and accurate water use 

accounting for Georgia. USGS will provide alternate technologies or methodologies for collecting or estimating withdrawals, water use deliveries, and returns of water use information 

with the expectation that improved water use accounting will 

be incorporated into the State of Georgia’s water management 

strategies. This project is scheduled to end in FY 2018.

The Treasure Valley of southwestern Idaho is the agricultural area that stretches west from Boise, Idaho into Oregon 

and is commonly referred to as the lower Boise River hydrologic unit. It contains four of the largest cities in Idaho: Boise, 

Meridian, Nampa, and Caldwell, respectively. The population 

of the Treasure Valley is about 600,000, but is projected to 

grow to 1.6 million by 2065. The objective of the USGS cooperative water use research study is to work with Idaho Department of Water Resources (IDWR) to develop an updated 

transient numerical groundwater flow model of Treasure 

Valley and surrounding areas to be used for water-supply planning and management. As part of the groundwater-flow model 

development, monthly water use data are collected from water 

providers in Treasure Valley and entered into the USGS NWIS 

Site-Specific Water Use Database System (SWUDS). These 

data are crucial to the accuracy of the groundwater-flow model 

and is the water-use research component to this project. This 

project is scheduled to end in 2021.

Improving the Scale of Water-Use Information

USGS has completed a 6-year, $5 million project to 

develop a site-specific database of public-water-supply systems and their groundwater and surface-water sources. This 

project is the first part of the effort to refine the scale of available water-use information from county and State totals to 

site-specific data, which can be used to analyze water use for 

watersheds at multiple scales. 

The public-supply database effort was coordinated with 

the EPA and utilized a 2010 end-of-year dataset from the EPA 

Safe Drinking Water Information System national database 

(SDWIS/Fed), which contains public water system information as reported by states to the EPA (https://www.epa.gov/

ground-water-and-drinking-water/safe-drinking-water-information-system-sdwis-federal-reporting). SDWIS/Fed includes 

system and water-source information, but does not have water 

withdrawals. Under the agreement with the EPA, USGS treats 

all public-water-source information obtained from SDWIS/

Fed as proprietary. 

The information on systems and water sources from 

SDWIS/Fed was first integrated into an interim database called 

Public Supply Database (PSDB), which also contains a 2010 

extract of public supply sources from the USGS NWIS. The 

structure and development of PSDB is documented in Price 

and Maupin (2014). PSDB was then used to provide system 

and site information to USGS offices nationwide, where it was 

more extensively compared to USGS site information and, 

additionally, to public supply water-use information obtained 

by USGS from State and local agencies. This work was done 

to develop the final datasets for the NWIS Site-Specific WaterUse Data System (SWUDS). Water sources and systems not 
42 Continuing Progress Toward a National Assessment of Water Availability and Use

already in SWUDS were added, as was information on water 

movement or conveyances between the sources and systems, 

and water withdrawal information for the year 2010, the most 

recent available year at the start of this project. In cases where 

specific source withdrawals were not available, water volumes 

are aggregated and stored in SWUDS at the system level.

The SWUDS database provides a circa-2010 archive of 

the site-specific data underlying the national 5-year report, 

improving the consistency and quality of those estimates. 

The site-specific data will be used in water-budget reports to 

compare available water-use data for this sector to other waterbudget components. 

Release of Pre-1985 Data and Statewide Totals

Beginning in 1985, the underlying data for the 5-year 

report “Estimated Use of Water in the United States” was 

developed at the county level (and at the hydrologic cataloging 

unit level HUC-8 for 1985 to 1995) and stored in the USGS 

Aggregate Water Use Data System (AWUDS), as part of the 

NWIS. Prior to the 2010 report, AWUDS was enhanced to 

support multiple datasets for a given year and state, allowing for one dataset that supports a publication and another 

that contains the “best available” data—that is, data that 

incorporate corrections and improved estimates made after 

publication. Publication datasets are linked to the reports 

they support, and best available county data are made available through NWISWeb (https://waterdata.usgs.gov/nwis/

wu/) and the Water Census portal (https://cida.usgs.gov/

nwc/#!waterbudget). 

With the additional capability of multiple datasets for 

counties and watersheds in AWUDS, revisions to this important set of water-use estimates can be tracked and documented. 

However, the data for the reports from 1950 to 1980 were 

not available in digital form, and information on revisions to 

the data since publication was limited. In 2017, AWUDS was 

enhanced to allow the storage of estimates at the State level 

for the set of data elements used in the 1960 to 1980 reports 

(http://water.usgs.gov/watuse/50years.html); data for the 1950 

and 1955 reports were beyond the scope of this effort. Published data from the 1960 to 1980 reports were used to develop 

input data as the publication datasets, and available notes and 

worksheets on revisions to these data were used to develop 

“best available” datasets. AWUDS can now (2017) provide a 

digital data source and a means of tracking revisions for the 

1960 to 1980 estimates of water use at the State level, similar 

to the functionality for 1985 to present county-level estimates.

Water-Use Science Training

Training needs for the water-use community in the 

NWUSP have increased with improved computer and database 

functionality, as well as the need for more accurate water-use 

data for USGS studies. The NWUSP conducted a project from 

2016 through 2017 to develop 1-hour online training modules 

for all aspects of water-use science. These completed training modules are made available through the USGS Office of 

Organizational and Employee Development (OED) websites 

(https://www2.usgs.gov/humancapital/ecd/ecd_telavailcourses.

html). The target audience is USGS scientists who collect or 

use water-use data, but can include scientists from cooperating agencies. The training modules encompass sessions about 

the concepts of water-use science in USGS, as well as both 

the aggregated (AWUDS) and site-specific (SWUDS) database systems, and the categories of water use, which include 

public supply, domestic, industrial, commercial, irrigation, 

thermoelectric power, hydroelectric power, livestock, mining, 

aquaculture, and wastewater treatment. The modules provide 

user interaction with question and answer sessions, and links 

to glossaries, guidelines, coding forms, and other resources. 

The training modules are listed below.

• USGS Water Use—Introduction to the 5-Year WaterUse Compilation (DOILearn module USGS-H-17-127)

• USGS Water Use—Water-Use Concepts (DOILearn 

module USGS-H-17-126)

• USGS Water Use—Public Supply (DOILearn module 

USGS-H-17-094)

• USGS Water Use—Thermoelectric Power (DOILearn 

module USGS-H-17-129)

• USGS Water Use—Irrigation (DOILearn module 

USGS-H-17-128)

Draft Water-Use Science Strategy

The Water Availability and Use Science Program is 

producing a science strategy for the NWUSP in 2018. A Draft 

Science Strategy is planned to be comprehensive of the many 

aspects of the water-use project. The Draft Science Strategy 

addresses both new scientific and programmatic directions for 

the NWUSP, along with the resources necessary to address 

those efforts both for the WMA headquarters and for the 

USGS Water Science Centers (WSCs) which support and contribute to the NWUSP. The Draft Science Strategy was guided 

by a committee, with scientists from many programs across 

the USGS, along with a representative of Reclamation and of 

the Western States Water Council.

A Draft Science Strategy was developed around the 

central theme that water use is an integral component of the 

hydrologic cycle and, in order to understand that cycle, the 

USGS must connect water-use information with it—at all 

spatial scales. This objective means that, in both large and 

small watersheds and aquifers, the USGS must be able to 

provide fine-scale water-use information to describe the effects 

of water use on the hydrology of the watershed or aquifer. The 

Draft Science Strategy finds that, for most water-use sectors, 

only site-specific water-use information will fulfill this need.

The USGS has always worked closely with States and 

their agencies which deal with water use in the compilation 
Topical Studies 43

and analysis of water use information and it will continue this 

close working relationship. A Draft Science Strategy purports 

the use of direct surveys of water users, along with the use of 

statistical models, to provide the needed site-specific wateruse information in areas where it is not readily available from 

other agencies. The USGS will work closely with its State 

agency partners to produce the best survey approaches and 

leverage and advance ongoing State activities to achieve these 

water-use compilation goals. In order to fully implement these 

measures, the USGS will have to comply with the requirements of the Paperwork Reduction Act (Pub. L. No. 96-511, 

94 Stat. 2812, codified at 44 U.S.C. §§ 3501–3521) and will 

have to invest substantial resources in the development of 

trained personnel and information technology infrastructure. 

Further, the Draft Science Strategy proposes relating wateruse information to socioeconomic information, a new area of 

endeavor for the USGS. This effort is proposed to help expand 

the National understanding of water use and the factors that 

influence, or are influenced by, water use.

Environmental Water Science

The SECURE Water Act, Section 9508 (a) (6) calls for 

the USGS “...to develop the basis for an improved ability to 

forecast the availability of water for future economic, energy 

production, and environmental uses.” As further evidence 

of the interest in environmental uses of water by the U.S. 

Congress, Section 9508 (b) (1) (D) calls for “...a focus on 

the scientific integration of any data relating to water use, 

water flow, or water quality to generate relevant information 

relating to the impact of human activity on water and ecological resources.” Finally, Section 9508 (b) (2) (C) calls for 

“...developing and applying predictive modeling tools that 

integrate groundwater, surface water, and ecological systems.” 

Such information will allow water managers and planners to 

make more effective decisions in the future with regards to the 

environmental uses of water.

Environmental water science is the study of the quantity, timing, and quality of water flow and storage required to 

sustain freshwater and estuarine ecosystems and the human 

well-being and livelihoods that depend on them. Water flow 

and storage include streamflows as well as variations in water 

levels in lakes, rivers, streams, springs, wetlands, and aquifers. 

Environmental water science has advanced greatly over the 

past two decades, driven largely by a need to improve understanding of the relation between environmental water uses 

and the environmental flows required to maintain those uses, 

prevent degradation of freshwater ecosystems, and improve 

the balance between human and environmental water needs.

In support of environmental water science at the national 

scale, the USGS is developing innovative tools and web-available resources that provide stakeholders and environmental 

water science practitioners with the hydrologic and ecological information necessary for comparing natural and altered 

hydrologic regimes and determining the effects of streamflow 

alteration and water withdrawals on aquatic ecosystems. To 

support such comparisons, streamflow-simulation modeling 

tools for building a national foundation of baseline hydrographs (see Flow at Ungaged Locations) are being developed 

that will ultimately provide hydrologic data for all ungaged 

streams in the United States. A baseline hydrograph is a graph 

that reflects fluctuations in key elements of the natural flow 

regime (that is, duration, magnitude, timing, frequency, and 

rate of change in streamflow). The development of a national 

foundation of baseline hydrographs is an important step in 

environmental water assessment because it provides a hydrologic reference point with which hydrologic alterations can 

be considered (for example, comparing a current or modified 

hydrograph to an unimpaired hydrograph).

Serving Hydrologic and Ecological Information

Hydrologic and ecological information is being served 

nationally to stakeholders by means of the Water Census Data 

Portal (https://cida.usgs.gov/nwc/), which is a data platform 

and portal where stakeholders can access national estimates 

of water-budget components for local watersheds, waterwithdrawal data for counties, tools to calculate statistics 

of daily streamflow records, simulated daily streamflow at 

ungaged stations, and records of aquatic biology observations. 

Additionally, the Water Census Data Portal will enable connections to other large data compilations through interactive 

web services, including data collected by other Federal, State, 

and Tribal organizations. These Water Census efforts provide 

stakeholders, water purveyors, scientists, and environmental water practitioners with access to a broad range of data, 

information, and statistical tools that can be used to support 

hypothesis-driven experimentation; scientific advancement 

and innovation; and sustainable water-management practices, 

water-allocation plans, and water-governance policies.

Calculation of Streamflow Metrics

Estimates of daily streamflow as well as a suite of 

ecologically relevant hydrologic measurements are currently 

integrated with biological observations through the Water Census Data Portal. As part of this national effort, the Water Census has developed software that will calculate a broad suite 

of ecologically relevant streamflow statistics for any USGS 

gaging station within the National Water Information System 

(NWIS; available at https://waterdata.usgs.gov/nwis) by using 

the Streamflow Statistics Calculator. The Streamflow Statistics 

Calculator is an online tool that was created to simplify the 

process of generating hydrologic indicator statistics by using 

daily streamflow records. Essentially, this tool is an update of 

the USGS National Hydrologic Assessment Tool (Henriksen 

and others, 2006) that uses daily streamflow data from NWIS 

to calculate 183 ecologically relevant streamflow statistics 

that address multiple aspects of the hydrologic regime. This 

software tool is also available as a stand-alone open-source 
44 Continuing Progress Toward a National Assessment of Water Availability and Use

R package (available at https://github.com/USGS-R/EflowStats) and can be downloaded and used to calculate streamflow statistics on data that reside outside NWIS. Ecologically 

relevant streamflow statistics that characterize the magnitude, 

frequency, duration, timing, and predictability of streamflow 

and flow levels and account for the full range of hydrologic 

variability are critical for shaping riverine communities and 

ecosystem processes and for maintaining the biodiversity of 

aquatic, riparian, and wetland ecosystems. These ecologically 

relevant streamflow statistics are also important in understanding long-term trends in hydrology and climate and supporting 

investigations that are concerned with the restoration of flow 

characteristics that have been lost through flow regulation, 

water impoundment, or water extraction.

National Classification of Streams

In addition to the Streamflow Statistics Calculator, a 

national streamflow classification structure and a set of flexible tools are being developed and will be implemented in 

the Water Census Data Portal in the future. This classification structure, which will give stakeholders the capability 

to evaluate a region of interest at the scale necessary for 

sound management, is offered by the Water Census as one 

example of a means to classify streams for further environmental water work. The classification structure is designed to 

a predetermined set of stream classes derived from a subset 

of existing baseline hydrographs and, alternatively, to provide users with the option of deriving a set of stream classes 

based on user-specified input. Water managers and practitioners are also encouraged to explore their own classification 

systems in considering future work. Streamflow classification 

is one of the primary components of the Ecological Limits 

of Hydrologic Alteration (ELOHA; Poff and others, 2010), a 

scientific framework that outlines a multistep environmental 

water process of building a hydrologic foundation, developing 

streamflow classification, and constructing flow-ecology and 

flow-alteration ecological response relations for stream types. 

Components of the ELOHA framework have been adopted by 

the Water Census as well as by State and basin agencies that 

use it to assess hydroecological impairment and as a foundation for prioritization of streamflow restoration. 

Streamflow classification is a process of subdividing 

reference streams by similar hydrologic responses into stream 

types and is considered to be one of the first steps toward 

developing environmental water goals. This process requires 

the aggregation of daily streamflow data, digital watershed 

boundaries, and datasets characterizing human activities and 

natural features. The Water Census study by Archfield and others (2013) classified 1,543 streamgages in the conterminous 

United States (fig. 26) whose catchments are considered to be 

minimally regulated. Each streamgage used in this study had 

EXPLANATION

Streamgage classification

Group 1

Group 2

Group 3

Group 4

Figure 26. Hydroecological classification of 1,543 U.S. Geological Survey streamgages across the conterminous United States.

Four of the eight streamflow classes identified in Archfield and others (2013) are shown. Group 1 (blue) is characterized by the 

lowest annual variability, fewer outliers, a high correlation with daily streamflow, and a large seasonal signal; group 4 (orange) is 

characterized by the highest variability, more outliers, a lower correlation with streamflow, and a small seasonal signal.
Topical Studies 45

a minimum 20-year period of daily streamflow record from 

1950 to 2009.

This novel classification approach, the first since Poff 

(1996), uses seven fundamental properties of daily streamflow to represent the key elements of the natural flow regime. 

Findings of this study indicate that classification based on the 

seven fundamental properties of daily streamflow resulted in 

a high level of stability in streamflow class membership. Additionally, the use of the classification variables allows scientists 

to communicate results of hydroecological classifications to 

stakeholders and basin managers effectively and efficiently 

and provides a standardized classification structure across all 

regions in the conterminous United States. 

Aggregating Ecological Data from Multiple 

Agency Sources

One of the fundamentals of environmental water science is the ability to compare hydrologic data with datasets 

of aquatic biota occurrence and abundance. It is the goal of 

the Water Census to provide stakeholders with access to the 

greatest extent of aquatic biological datasets by means of the 

Data Portal. However, this type of access necessitates an indepth exploration of the comparability of ecological datasets 

that extend across State, catchment, and regional boundaries. 

The increasing availability of web-based data-mining sites 

containing ecological data from multiple agency sources has 

great potential for furthering understanding of the effects of 

hydrologic alteration across broad spatial or temporal scales. 

However, as access to and availability of such data sources 

become more commonplace, there is a pressing need to 

understand the effects of the preparation and use of these data 

on comparability and applicability to environmental water 

assessments, especially those that may have management or 

regulatory implications. Inconsistencies in taxonomic data can 

arise when data from multiple sources are combined. Such 

inconsistencies can represent operational and management 

challenges to State agencies and basin stakeholders because 

they may affect the sensitivity of biotic indices and can reduce 

their effectiveness for assessing environmental change. Prior 

to the development of biotic indices, taxonomic data need to 

be harmonized—that is, resolved to a common taxonomic 

level across multiple data sources that may use similar 

collection protocols, but do not necessarily identify organisms to the same taxonomic level or use the same standard 

organism count. 

The Water Census initiated an effort to examine the 

effects of important taxonomic data processing steps on 

aquatic invertebrate assemblage structure among nine city, 

State, interstate, and Federal agency sources within the Delaware River Basin (fig. 27), a Water Census Focus Area. This 

investigation by Cuffney and Kennen (2017) assesses how 

differences in data processing can affect numerical criteria for 

a common set of aquatic invertebrate assemblage metrics and 

presents how choices made during the data-processing steps 

can potentially alter the interpretation of relations with known 

landscape drivers (for example, urban land use, impervious 

surface cover, and streamflow).

Findings of this innovative Water Census study indicate 

that great care should be exercised when harmonizing taxa 

and subsample sizes prior to aggregating data across multiple 

agency sources. Failure to harmonize taxonomic data can 

overstate differences among assemblages, reduce the ability 

to detect environmental change, and introduce methodological discrepancies that can lead to erroneous interpretations of 

flow-ecology response relations. An important component of 

all State biomonitoring programs is the translation of an identified change in ecological condition into management goals 

or actions.

Drought Science

In 2016, the Congress provided the USGS with funding 

to improve water data and forecasting for drought. The USGS 

has worked to create science-based information and tools with 

the goal to make it easier to monitor, forecast, and provide 

early warnings for drought. More accurate information about 

the timing and duration of droughts can enable States, Tribes, 

counties, and cities to plan more effectively and reduce the 

effects of drought. The program is also looking to enhance 

monitoring activities and data-delivery systems to create 

a stronger link among the ground-based surface-water and 

groundwater monitoring networks of the USGS, groundwater 

networks of State agencies, and the soil moisture network of 

the Natural Resources Conservation Service. The following 

studies represent work conducted to date (2017) to achieve 

these objectives.

The first study investigated the behavior of soil moisture 

during droughts, as simulated in global circulation models 

(Berg and others, 2017). The study results indicate that analyzing soil-moisture changes on a layer-by-layer basis is important in order to avoid overestimating total soil-water availability. A second study (Dettinger, 2016; Albano and others, 2017) 

is considering the periodicity of atmospheric rivers and its 

role in producing humid (rainy) or arid (drought) conditions in 

the western coastal regions of the Nation. It is postulated that, 

if researchers can forecast the number of atmospheric rivers 

that will arrive on the West Coast in coming years, they will 

have the capability to forecast the majority of drought situations in the region months in advance. The third study focuses 

on the periodicity of very large storms and medium storms 

under future conditions and its role in drought occurrence. The 

research indicated that the future drought regime in California 

is likely to be one of longer precipitation deficits punctuated 

by a few very large storms, with the precipitation deficits arising mostly from a decrease in the number of medium-sized 

storms (Cayan and others, 2016; Dettinger and others, 2016; 

Harpold and others, 2017).
46 Continuing Progress Toward a National Assessment of Water Availability and Use

NEW YORK

PENNSYLVANIA

MARYLAND

NEW JERSEY

DELAWARE

Delaware 

 Bay

A T L A N T I C O C E A N

42°

41°

40°

39°

76° 75° 74°

EXPLANATION

Extent of Delaware River Basin

Agency source of invertebrate sampling location

Delaware River Basin Commission 

National Park Service

National Water-Quality Assessment Program

Environmental Monitoring and Assessment Program (EPA)

Philadephia Water Department

New York State Department of Environmental Conservation

Delaware Department of Natural Resources and Environmental Control

New Jersey Department of Environmental Protection

Pennsylvania Department of Environmental Protection

0 10 20 30 MILES

0 10 20 30 KILOMETERS

Base from U.S. Geological Survey 

1:100,000-scale digital data

Figure 27. Aquatic invertebrate sampling locations aggregated from nine agency sources in the Delaware River Basin. (Modified from 

Cuffney and Kennen, 2017)
Delivering the Data 47

Delivering the Data

To meet the objectives of the Water Census, data from 

multiple disciplines and sources must be assembled and 

integrated. Some of these data are obtained from existing 

sources within the USGS and partner agencies, whereas 

other data are developed directly as part of the Water Census 

activities. Many of the “data” developed by the Water Census are derived from models, statistical estimation, and other 

transformation processes. 

A data-management plan has been developed to provide a 

framework that will guide and document these activities across 

the entire Water Census effort. The Water Census was one of 

the first major science efforts in the USGS to formally develop 

a data-management plan, and the process of data-management 

planning continues to evolve within the USGS. Data management spans the entire data life cycle to include data acquisition, documentation, processing, analysis, preservation, and 

delivery. The data-management plan emphasizes adoption of 

existing international and Federal standards for data elements, 

processing, preservation, and delivery to serve as unifying and 

integrating criteria to facilitate interoperability with partners. 

The Water Census could not be accomplished without the 

solid framework of data and science that has been provided by 

the USGS water programs over the past 125 years. Most of the 

data used in water-availability analysis is stored in the USGS 

NWIS database and served to the Nation. The database provides hydrologic data on 1.5 million sites and contains records 

of surface water, groundwater, water use, and water quality. Additionally, the Water Census draws upon information 

provided by data portals maintained by other USGS programs, 

such as the EROS Data Center and the National Water Quality 

Assessment Water Quality Portal. 

Data Integration and Mapping

Many of the objectives of the Water Census involve 

delivery of integrated data and information resources. Some of 

these data, such as precipitation and evapotranspiration (ET), 

are provided in a form that must be processed to watershed 

units to be considered in a water budget. Others, like streamflow at ungaged locations, are generated through a combination of data assimilation and modeling and are inherently generated on a per-watershed basis. In both cases, water-budget 

variables have been processed and cataloged, and are being 

distributed, on a per-watershed basis. 

Precipitation and ET datasets used for the Water Census 

Data Portal (DP) are available as continuous gridded time 

series. In the case of ET, each grid cell represents the cumulative monthly ET for a 1-square-kilometer (0.39-square-mile) 

area. In order to use this ET data in a watershed-based water 

budget, the gridded time series must be attributed to watershed units by using spatial analysis to intersect grid cells 

and watershed polygons. For both the SSEBop and Daymet 

datasets, this attribution was accomplished by using the USGS 

Geo Data Portal (GDP) processing system. The GDP’s archive 

(https://cida.usgs.gov/thredds/) serves as the primary host of 

the SSEBop dataset. The project’s processing services (https://

cida.usgs.gov/gdp/) are compatible with the web services 

provided from the GDP archives as well as those provided by 

Oak Ridge National Laboratory (Oak Ridge, Tennessee) for 

Daymet precipitation data.

The spatial analysis performed by the GDP requires a set 

of watershed polygons. For the Water Census DP, HUC-12 

units derived from the Watershed Boundary Dataset were 

used for this purpose. HUC-12 units are “local-incremental” 

watershed units, averaging about 35 square miles in size 

across the Nation. Consequently, upstream HUC-12s must 

be joined together in order to be representative of an entire 

watershed. Data QA/QC of the connectivity between HUC12s was completed for the Water Census and published within 

the Watershed Boundary Dataset. Software that joins the 

HUC-12 units upstream from a given HUC-12 was developed and is available as an open-source R package at https://

github.com/USGS-R/HUCAgg. Aggregate watershed boundaries and water-budget variables are used to create Water 

Census DP “accumulated” water-budget data resource pages 

such as the one at https://cida.usgs.gov/nwc/#!waterbudget/

achuc/070900020703 for a watershed in Wisconsin. The image 

in figure 28 depicts all of the area that is contributing flow 

above the watershed of interest.

For data and model output developed by the USGS, a 

WATER CENSUS data-management plan was developed that 

provides requirements and guidance for data management. 

It is used as a program-wide policy to ensure consistency in 

planning, execution, and delivery of data from all WATER 

CENSUS activities. By using the plan, projects have clear 

guidelines for the data and metadata that will need to be 

delivered and the repository that will be used if no enterprise 

repository, such as the USGS’s NWIS, is available for the 

project’s deliverables. 

The USGS ScienceBase repository (https://www.

sciencebase.gov/catalog/item/5151f07ee4b0f0b3d011a817) 

is being used as a catalog and data store to track projects and 

their deliverables including publications, models, and datasets. 

Many of the model and data outcomes of focus area and topical studies are available directly from ScienceBase, whereas 

reports and data stored elsewhere are available through links 

cataloged in ScienceBase. As mentioned above, SSEBop estimates of evapotranspiration have been deposited in the GDP 

model data archive, and water-use data are housed in NWIS.

The National Data Platform

As they are completed, WATER CENSUS data resources 

are published through a single portal, the DP (https://cida.

usgs.gov/nwc/) that helps users discover information for 8- 

and 12-digit HUC watersheds. The DP provides a map view 

of HUCs, allowing users to zoom to their area of interest and 

select one of the Water Census watershed units. Once the 
48 Continuing Progress Toward a National Assessment of Water Availability and Use

Figure 28. An accumulated water budget for a watershed in Wisconsin showing precipitation, 

streamflow, and evapotranspiration. (From U.S. Geological Survey, 2017f)

appropriate watershed has been selected, a user can explore 

the dominant water-budget components of the watershed in 

which they have an interest. 

In the first 5 years of the WATER CENSUS, DP development has included building infrastructure to catalog and 

display completed nationally consistent water-budget data for 

any HUC-12 watershed in the country. In the next 5 years, this 

infrastructure will be leveraged to provide a complete, closed 

water budget as discussed previously in this report. As of 

2017, the DP contains precipitation data from Daymet and ET 

data from SSEBop for every watershed in the lower 48 states, 

and area-aggregated water-use estimates for counties from the 

AWUDS database. Daymet data are available starting in 1980, 

SSEBop data are available starting in 2000, and AWUDS data 

are available starting in 1985. For watersheds that have an 

NWIS streamgage near their outlet and for watersheds in part 

of the southeastern United States, where modeling has been 

completed, runoff data (represented as streamflow per unit 

area) are also available. Streamflow data for the rest of the 

country will be added in 2018. In the next 5 years, as progress 

is made on modeling a complete, closed water budget, it is 

expected that other terms, such as storage, snow water equivalent, and site-specific water use, will be included.

The DP also includes pilot functionality to discover 

aquatic-biology data and utilities to calculate streamflow 

statistics for environmental water evaluation. As the DP 

progresses, this functionality will be maintained but may be 

combined into other data systems better suited to satisfying the 

needs of environmental water studies. A view of the resources 

in the ScienceBase project data inventory is also included in 

the DP. It is expected that this functionality will be migrated 

to the main WATER CENSUS web presence as the USGS 

webpage infrastructure is updated in the coming years. 

In order to facilitate use of the portal and its data 

resources, a set of educational materials targeted at a college 

hydro-informatics classroom was developed. The materials, 

which are available at https://github.com/NWCEd/NWCEd, 

provide a set of classroom activities that guide students 

through the use of the portal and its data as well as introduce 

them to basic hydro-informatics scripting concepts. These 

materials are available publicly at https://github.com/USGS-R/

NWCEd and are documented in Nelson (2017).
Planning for the Future 49

Each water-budget data resource can be accessed from a unique URL of 

the form: 

https://cida.usgs.gov/nwc/#!waterbudget/achuc/070900020703, 

where 

“https://cida.usgs.gov/nwc/#!waterbudget/” is the portal entry to all 

water-budget data resources and

“achuc/070900020703” specifies the total accumulated upstream watershed view of hydrologic unit 070900020703. 

Building the system by using these referenceable URLs allows the waterbudget data resources to be included in other information products and 

will aid in future efforts to expose the system to search engines. 

Planning for the Future

Progress toward a Water Census has been made by initiating new work and by integrating information from a number 

of programs and ongoing national-scale efforts, such as the 

USGS Groundwater and Streamflow Information Program and 

the USGS Regional Groundwater Evaluations. USGS efforts 

have also built upon the legacy provided by long-term monitoring and assessment programs funded under the previous 

USGS Cooperative Water Program and the National Streamflow Information Program. Over the next 5 years, progress 

will continue with the existing efforts and expand as funding 

allows. In addition to completing the ongoing work described 

in this report, priorities for future work are described below.

Future Geographic Focus Area Studies

The Water Census will complete the three ongoing FASs 

and will initiate new FASs in the future. The three ongoing 

studies are planned for completion by 2019 and the Water 

Census will initiate a process prior to their completion to 

select new locations for FASs. As stated earlier, the Water 

Census has learned a great deal from the six FASs that are 

either completed or ongoing. They (1) contribute to ongoing assessments of water availability in large watersheds 

with potential water-use conflicts, (2) provide high-resolution water-use databases that can be used for a multitude 

of purposes, (3) provide opportunities to test and improve 

approaches to water-availability assessment that can be transferred to other areas, and (4) inform and “ground truth” the 

Water Census with local information. The Water Census FASs 

also fulfill USGS reporting on two of the primary assessments 

that the U.S. Congress requested of the USGS in the SECURE 

Water Act: where are the significant water-use conflicts or 

shortages that have occurred, or are occurring, and what 

are the factors that have caused, or are causing, the conflict 

or shortage?

The Water Census has previously used a two-stage process for soliciting and selecting candidates for new FASs. The 

first stage involves soliciting USGS WSCs to nominate candidate river basins, through an efficient preproposal process, for 

the future studies. The second stage involves full proposals of 

candidates from the earlier stage. All proposals are reviewed 

by a panel of experts from across the USGS and a representative of the Bureau of Reclamation. The final candidate FASs 

are selected for project funding over a 3-year period. 

Within the effort scoped for FASs, the emphasis will 

remain on fulfilling the water-use data needs at the HUC-8 

level. Continuing to compile water-use data for the major 

categories (as reported since 2010), and potentially backfilling 

in other categories of use, such as waste-water return flows, 

would benefit the NWUSP as well as other Water Census 

project objectives, such as closing the water budget. Collecting as much site-specific data as possible for categories such 

as public supply and thermoelectric water withdrawals will be 

beneficial. These data will be stored in the appropriate USGS 

NWIS databases, either aggregated or site-specific. These data 

will help to improve the knowledge about water budgets and 

assess trends in water use.

Modeling Approach

Over the next 5 years, the Water Census will place a 

considerable effort on providing current and historical wateravailability information on a daily time step and at the scale of 

HUC-12 subbasins. For context, HUC-12 subbasins average 

approximately 35 square miles in area and there are approximately 88,500 of them in the conterminous United States. 
50 Continuing Progress Toward a National Assessment of Water Availability and Use

The Water Census strives to present a daily water budget for 

each of these subbasins within the conterminous United States 

within the next 5 years. The primary building blocks of the 

water budget are precipitation, streamflow, ET, water use, 

and change in storage. Today, the Water Census, through the 

WATER CENSUS DP, presents a continuous coverage for the 

conterminous United States of precipitation at a daily time 

step and ET at a monthly time step. Streamflow is presented at 

a daily time step only for the southeastern United States, and 

water use is presented only on a county scale and at 5-year 

time intervals for the conterminous United States. There is 

much work to be accomplished in the next 5 years.

The first set of priorities will be to provide daily streamflow estimates for the remainder of the conterminous United 

States and to increase estimation of ET from a monthly time 

step to a daily time step. These tasks will be accomplished 

through the application of a watershed model, which is 

calibrated to physical measurements of water-budget components at various locations across the United States and 

simulates those components where measurements do not exist. 

The watershed model will generate the daily estimates of 

streamflow and ET at the scale of HUC-12 subbasins and the 

estimates will be provided to the public through the WATER 

CENSUS DP at https://cida.usgs.gov/nwc/. The ET estimates 

from the model will incorporate information from ET estimation using remote-sensing data from LandSAT. 

As stated previously in this report, water budgets provide 

the foundation for sound water-availability analysis. When all 

of the water-budget components for a watershed have been 

estimated, hydrologists work through a process to “close” the 

water budget. This process involves balancing all components 

of the water budget so that the sum of the supply terms equals 

the sum of the demand terms, taking into account changes in 

storage. During the next 5 years, the Water Census will use 

a selected modeling application to close the water budget for 

HUC-12 watersheds throughout the conterminous United 

States at a daily time step. 

In the area of environmental water science, ongoing 

national classification work by the Water Census is leveraging the findings of the Archfield and others (2013) study to 

develop statistical models that will be used over the next 

5 years to assign all ungaged rivers in the conterminous United 

States to one of the published stream classes on the basis of 

measured basin and climate characteristics within an established range of uncertainty. Once completed, this follow-up 

effort will provide a broad-based classification structure that 

can be overlain onto a national mapping framework, such as 

NHDPlus, and used as a basis for understanding the full scope 

of stream classes across the United States. Additionally, this 

study is evaluating the degree of model misclassification (that 

is, the level of uncertainty in stream-class assignment), which 

will provide stakeholders with the information necessary to 

make informed decisions about management actions that may 

affect all streams of a given stream class. 

The science of environmental water continues to progress, in part as a result of frameworks such as ELOHA, which 

have provided a strong scientific foundation for stakeholders 

and environmental water practitioners that support a better 

understanding of the interdependencies between streamflow 

and ecological response. Future Water Census efforts will 

place a strong emphasis on the development of newer, more 

dynamic statistical and process modeling techniques capable 

of integrating components of the water cycle and accounting 

for ecosystem response. These dynamic models will leverage 

the availability of synthetic hydrographs developed by using 

simulation modeling and the broader access to biological data 

through web sources to support an improved understanding 

of the relations between streamflow change and ecological 

response. This type of approach is strongly needed and represents the fundamental underpinnings of environmental water 

science and management in the future.

Future Databases Needed

In the next 5 years, the Water Census will create a 

database of interbasin transfers of water in the United States. 

Interbasin transfers are the movement of water from one 

subregion (HUC-4) to another through manmade or artificial 

conduits (tunnels, canals, pipes) in most cases, but also possibly through natural conduits (rivers or reservoir connections). 

In all of these cases, the transfer of water is under human management and control. Interbasin transfers are necessary when 

water is moved to meet demands in regions outside the source 

watershed. Because it is difficult, if not impossible, to account 

for all of the individual categories and quantities of uses of 

the water in the receiving subregion, this effort will focus on 

accounting for the total quantities of water that are transferred, 

to the smallest temporal scale (seasonal, monthly) possible 

within the context of accuracy limitations. The USGS inventoried interbasin water transfers at the HUC-4 scale for calendar 

years 1973 to 1982 in the western states (Petsch, 1985) and 

the eastern states (Mooty and Jeffcoat, 1986). At the time of 

these reports, 256 interbasin water transfers were inventoried. 

Water transfers can have a substantial effect on the hydrology 

of and water availability in both the exporting and importing 

basins, and it is of great interest to the NWUSP to inventory 

and assess the characteristics of interbasin transfers. Transfers 

are also crucial to the understanding of water budgets in both 

the exporting and receiving river basins.

The NWUSP will begin regular reporting of interbasin 

transfers of water at the HUC-4 scale. Transfers of water that 

exceed 100,000 gallons per day averaged over a calendar 

month will be counted. This rate will be known as the volumetric threshold for interbasin transfers. 

The NWUSP will identify the names and locations of 

all conveyances that transfer water in excess of the volumetric threshold between two HUC-4 basins on an annual basis. 

The location data will include the latitude and longitude of 

the point of origin of the conveyance and the initial point of 

delivery in the receiving HUC-4 basin. Storing the locations of 

these diversion sites as point locations in NWIS would enable 

the water-transfer data to be provided to other WAUSP project 
References Cited 51

activities, such as mapping water depletions for use in waterbudget analyses at the HUC-4 basin scale 

This work will be a multiagency effort, with collaboration and cooperation among the USGS, U.S. Army Corp of 

Engineers, Bureau of Reclamation, and State agencies that are 

responsible for the management and operation of interbasin 

transfers. This effort will begin with forming a multiagency 

committee to identify other agencies and organizations that 

have purview over water transfers and the operation of the 

infrastructure that enables the transfers. As part of an inventory, an informational survey will be shared with the committee to update and improve the listing of interbasin transfers, 

including assessing locational information and identifying 

geospatial nomenclature.

Through these ongoing and planned future activities, 

the USGS will add to the science of water availability and 

incrementally work toward the goal that Congress articulated 

in the SECURE Water Act—an ongoing national assessment 

of water availability and use.

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Appendix 1. Geographic Focus Area Study Publications 59

Appendix 1. Geographic Focus Area Study Publications

Apalachicola-Chattahoochee-Flint River Basin

Clarke, J.S., and Painter, J.A., 2014, Influence of septic 

systems on stream base flow in the Apalachicola-Chattahoochee-Flint River Basin near Metropolitan Atlanta, 

Georgia, 2012: U.S. Geological Survey Scientific Investigations Report 2014–5144, 68 p. [Also available at https://doi.

org/10.3133/sir20145144.]

Freeman, M.C., Buell, G.R., Hay, L.E., Hughes, W.B., 

Jacobson, R.B., Jones, J.W., Jones, S.A., LaFontaine, J.H., 

Odom, K.R., Peterson, J.T., Riley, J.W., Schindler, J.S., 

Shea, Colin, and Weaver, J.D., 2013, Linking river management to species conservation using dynamic landscapescale models: River Research and Applications, v. 29, 

p. 906–918. [Also available at http://onlinelibrary.wiley.

com/doi/10.1002/rra.2575/full.]

Gordon, D.W., Peck, M.F., and Painter, J.A., 2012, Hydrologic 

and water-quality conditions in the lower ApalachicolaChattahoochee-Flint and parts of the Aucilla-SuwaneeOchlockonee River basins in Georgia and adjacent parts of 

Florida and Alabama during drought conditions, July 2011: 

U.S. Geological Survey Scientific Investigations Report 

2012–5179, 69 p., 1 sheet. [Also available at http://pubs.

usgs.gov/sir/2012/5179/.]

Jones, L.E., Painter, Jaime, LaFontaine, Jacob, Sepulveda, 

Nicasio, and Sifuentes, D.F., 2017, Groundwater-flow 

budget for the lower Apalachicola-Chattahoochee-Flint 

River Basin in southwestern Georgia and parts of Florida 

and Alabama, 2008–12: U.S. Geological Survey Scientific 

Investigations Report 2017–5141, 76 p. [Also available at 

https://doi.org/10.3133/sir20175141.]

LaFontaine, J.H., Jones, L.E., and Painter, J.A., 2017, Simulations of hydrologic response in the Apalachicola-Chattahoochee-Flint River Basin, Southeastern United States: U.S. 

Geological Survey Scientific Investigations Report 2017–

5133, 112 p. [Also available at https://doi.org/10.3133/

sir20175133.]

Lawrence, S.J., 2016, Water use in the Apalachicola-Chattahoochee-Flint River Basin, Alabama, Florida, and Georgia, 

2010, and water-use trends, 1985–2010: U.S. Geological 

Survey Scientific Investigations Report 2016–5007, 72 p. 

[Also available at https://doi.org/10.3133/sir20165007.]

Painter, J.A., Torak, L.J., and Jones, J.W., 2015, Evaluation 

and comparison of methods to estimate irrigation withdrawal for the National Water Census Focus Area Study 

of the Apalachicola-Chattahoochee-Flint River Basin in 

southwestern Georgia: U.S. Geological Survey Scientific 

Investigations Report 2015–5118, 32 p. [Also available at 

https://doi.org/10.3133/sir20155118.]

Peterson, J.T., and Freeman, M.C., 2016, Integrating modeling, monitoring, and management to reduce critical uncertainties in water resource decision making: Journal of Environmental Management, v. 183, p. 361–370. [Also available 

at https://doi.org/10.1016/j.jenvman.2016.03.015.]

Regan, R.S., and LaFontaine, J.H., 2017, Documentation of 

the dynamic parameter, water-use, stream and lake flow 

routing, and two summary output modules and updates to 

surface-depression storage simulation and initial conditions 

specification options with the Precipitation-Runoff Modeling System (PRMS): U.S. Geological Survey Techniques 

and Methods, book 6, chap. B8, 60 p. [Also available at 

https://doi.org/10.3133/tm6B8.]

Colorado River Basin

Clow, D.W., 2010, Changes in the timing of snowmelt and 

streamflow in Colorado—A response to recent warming: 

Journal of Climate, v. 23, no. 9, p. 2293–2306. [Also available at https://doi.org/10.1175/2009jcli2951.1.]

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and aerosol chemistry: Atmospheric Environment, v. 146, 

p. 183–194. [Also available at https://doi.org/10.1016/j.

atmosenv.2016.06.076.]

Liston, G.E., and Elder, Kelly, 2006, A distribution snow-evolution modeling system (SnowModel): Journal of Hydrometeorology, v. 7, p. 1259–1276. [Also available at https://doi.

org/10.1175/JHM548.1.]
60 Continuing Progress Toward a National Assessment of Water Availability and Use

Miller, M.P., Buto, S.G., Susong, D.D., and Rumsey, C.A., 

2016, The importance of base flow in sustaining surface 

water flow in the Upper Colorado River Basin: Water 

Resources Research, v. 52, p. 3547–3562. [Also available at 

http://onlinelibrary.wiley.com/doi/10.1002/2015WR017963/

full.]

Miller, M.P., Johnson, H.M., Susong, D.D., and Wolock, 

D.M., 2015, A new approach for continuous estimation 

of baseflow using discrete water quality data—Method 

description and comparison with baseflow estimates from 

two existing approaches: Journal of Hydrology, v. 522, 

p. 203–210. [Also available at http://dx.doi.org/10.1016/j.

jhydrol.2014.12.039.]

Miller, M.P, Susong, D.D., Shope, C.L., Heilweil, V.M., 

and Stolp, B.J., 2014, Continuous estimation of baseflow 

in snowmelt-dominated streams and rivers in the Upper 

Colorado River Basin—A chemical hydrograph separation 

approach: Water Resources Research, v. 50, p. 6986–6999. 

[Also available at http://onlinelibrary.wiley.com/

doi/10.1002/2013WR014939/full.]

Rumsey, C.A., Miller, M.P., Susong, D.D., Tillman, F.D., and 

Anning, D.W., 2015, Regional scale estimates of baseflow 

and factors influencing baseflow in the Upper Colorado 

River Basin: Journal of Hydrology—Regional Studies, 

v. 4, p. 91–107. [Also available at https://doi.org/10.1016/j.

ejrh.2015.04.008.]

Sexstone, G.A., Clow, D.W., Stannard, D.I., and Fassnacht, 

S.R., 2016, Comparison of methods for quantifying surface 

sublimation over seasonally snow-covered terrain: Hydrological Processes, v. 30, no. 19, p. 3373–3389. [Also available at https://doi.org/10.1002/hyp.10864.]

Solder, J.E., Stolp, B.J., Heilweil, V.M., and Susong, D.D., 

2016, Characterization of mean transit time at large springs 

in the Upper Colorado River Basin, USA—A tool for 

assessing groundwater discharge vulnerability: Hydrogeology Journal, v. 24, p. 2017–2033. [Also available at https://

doi.org/10.1007/s10040-016-1440-9.]

Delaware River Basin

Cole, J.C., Maloney, K.O., Schmid, Matthias, and McKenna, 

J.E., 2014. Developing and testing temperature models for 

regulated systems—A case study on the upper Delaware 

River: Journal of Hydrology, v. 519, p. 588–598. [Also 

available at https://doi.org/10.1016/j.jhydrol.2014.07.058.]

Hutson, S.S., Linsey, K.S., Ludlow, R.A., Reyes, Betzaida, 

and Shourds, J.L., 2015, Estimated use of water in the 

Delaware River Basin in Delaware, New Jersey, New York, 

and Pennsylvania, 2010: U.S. Geological Survey Scientific 

Investigations Report 2015–5142, 76 p. [Also available at 

https://dx.doi.org/10.3133/sir20155142.]

Maloney, K.O., Cole, J.C., and Schmid, Matthias, 2016, Predicting thermally stressful events in rivers with a strategy 

to evaluate management alternatives: River Research and 

Applications, v. 32, no. 7, p. 1428–1437. [Also available at 

https://doi.org/10.1002/rra.2998.]

Maloney, K.O., Talbert, C.B., Cole, J.C., Galbraith, H.S., 

Blakeslee, C.J., Hanson, Leanne, and Holmquist-Johnson, 

C.L., 2015. An integrated riverine environmental flow decision support system (REFDSS) to evaluate the ecological 

effects of alternative flow scenarios on river ecosystems: 

Fundamental and Applied Limnology/Archiv für Hydrobiologie, v. 186, p. 171–192. [Also available at https://doi.

org/10.1127/fal/2015/0611.]

Stuckey, M.H., 2016, Estimation of daily mean streamflow 

for ungaged stream locations in the Delaware River Basin, 

water years 1960–2010: U.S. Geological Survey Scientific 

Investigations Report 2015–5157, 42 p. [Also available at 

https://doi.org/10.3133/sir20155157.]

Stuckey, M.H., and Ulrich, J.E., 2016, User’s guide for 

the Delaware River Basin Streamflow Estimator Tool 

(DRB-SET): U.S. Geological Survey Open-File Report 

2015–1192, 6 p. [Also available at https://doi.org/10.3133/

ofr20151192.]

Talbert, Colin, Maloney, K.O., Holmquist-Johnson, C.L., 

and Hanson, Leanne, 2014, User’s manual for the upper 

Delaware River riverine environmental flow decision support system (REFDSS) (ver. 1.1.2): U.S. Geological Survey 

Open-File Report 2014–1183, 23 p. [Also available at 

https://doi.org/10.3133/ofr20141183.]

Williamson, T.N., Lant, J.G., Claggett, P.R., Nystrom, E.A., 

Milly, P.C.D., Nelson, H.L., Hoffman, S.A., Colarullo, 

S.J., and Fischer, J.M., 2015, Summary of hydrologic 

modeling for the Delaware River Basin using the Water 

Availability Tool for Environmental Resources (WATER): 

U.S. Geological Survey Scientific Investigations Report 

2015–5143, 68 p. [Also available at https://doi.org/10.3133/

sir20155143.] 

Williamson, T.N., Nystrom, E.A., and Milly, P.C.D., 2016, 

Sensitivity of the projected hydroclimatic environment of 

the Delaware River basin to formulation of potential evapotranspiration: Climatic Change, v. 139, p. 215–228. [Also 

available at https://doi.org/10.1007/s10584-016-1782-2.]
Appendix 2. Regional Groundwater Availability Study Publications 61

Appendix 2. Regional Groundwater Availability Study Publications

Columbia Plateau Regional Aquifer System 

Ely, D.M., Burns, E.R., Morgan, D.S., and Vaccaro, J.J., 2014, 

Numerical simulation of groundwater flow in the Columbia 

Plateau regional aquifer system, Idaho, Oregon, and Washington (ver. 1.1, January 2015): U.S. Geological Survey 

Scientific Investigations Report 2014–5127, 90 p. [Also 

available at https://doi.org/10.3133/sir20145127.] 

Kahle, S.C., and Vaccaro, J.J., 2015, Groundwater resources of 

the Columbia Plateau regional aquifer system: U.S. Geological Survey Fact Sheet 2015–3063, 6 p. [Also available 

at https://doi.org/10.3133/fs20153063.]

Vaccaro, J.J., Kahle, S.C., Ely, D.M., Burns, E.R., Snyder, 

D.T, Haynes, J.V., Olsen, T.D., Welch, W.B., and Morgan, 

D.S., 2015, Groundwater availability of the Columbia 

Plateau regional aquifer system, Washington, Oregon, and 

Idaho: U.S. Geological Survey Professional Paper 1817, 

87 p. [Also available at https://doi.org/10.3133/pp1817.] 

High Plains Aquifers

Houston, N.A., Gonzales-Bradford, S.L., Flynn, A.T., Qi, S.L., 

Peterson, S.M., Stanton, J.S., Ryter, D.W., Sohl, T.L., and 

Senay, G.B., 2013, Geodatabase compilation of hydrogeologic, remote sensing, and water-budget-component data for 

the High Plains aquifer, 2011: U.S. Geological Survey Data 

Series 777, 12 p. [Also available at https://pubs.usgs.gov/

ds/777/.]

Peterson, Steven, 2016, Base of aquifer contours for the 

Northern High Plains aquifer: U.S. Geological Survey 

data release, accessed September 29, 2017, at https://doi.

org/10.5066/F7K072C9.

Peterson, S.M., Flynn, A.T., and Traylor, J.P., 2016a, Groundwater-flow model of the Northern High Plains aquifer in 

Colorado, Kansas, Nebraska, South Dakota, and Wyoming: 

U.S. Geological Survey Scientific Investigations Report 

2016–5153, 88 p. [Also available at https://doi.org/10.3133/

sir20165153.]

Peterson, S.M., Flynn, A.T., and Traylor, J.P., 2016b, MODFLOW-NWT groundwater flow model used to evaluate 

conditions in the Northern High Plains aquifer in Colorado, 

Kansas, Nebraska, South Dakota, and Wyoming: U.S. Geological Survey data release, accessed September 29, 2017, 

at https://doi.org/10.5066/F7JS9NKD.

Floridan Aquifer System

Kuniansky, E.L., 2016, Simulating groundwater flow in karst 

aquifers with distributed parameter models—Comparison 

of porous-equivalent media and hybrid flow approaches: 

U.S. Geological Survey Scientific Investigations Report 

2016–5116, 14 p. [Also available at https://doi.org/10.3133/

sir20165116.]

Reyes, Betzaida, 2017, Daily weather data (precipitation, 

minimum and maximum air temperatures) of Florida, parts 

of Georgia, Alabama, and South Carolina, 1895–1915: U.S. 

Geological Survey data release, accessed February 1, 2018, 

at https://doi.org/10.5066/F7639MT4.

Williams, L.J., and Dixon, J.F., 2015, Digital surfaces and 

thicknesses of selected hydrogeologic units of the Floridan 

aquifer system in Florida and parts of Georgia, Alabama, 

and South Carolina: U.S. Geological Survey Data Series 

926, 24 p. [Also available at https://doi.org/10.3133/ds926.]

Williams, L.J., and Kuniansky, E.L., 2015, Revised hydrogeologic framework of the Floridan aquifer system in Florida 

and parts of Georgia, Alabama, and South Carolina: U.S. 

Geological Survey Professional Paper 1807, 140 p., 23 pl. 

[Also available at https://doi.org/10.3133/pp1807.]

Williams, L.J., Raines, J.E., and Lanning, A.E., 2013, Geophysical log database for the Floridan aquifer system 

and southeastern Coastal Plain aquifer system in Florida 

and parts of Georgia, Alabama, and South Carolina: U.S. 

Geological Survey Data Series 760, 11 p. [Also available at 

http://pubs.usgs.gov/ds/760.]

Northern Atlantic Coastal Plain Aquifer System

Charles, E.G., 2016, Regional chloride distribution in the 

Northern Atlantic Coastal Plain aquifer system from 

Long Island, New York, to North Carolina: U.S. Geological Survey Scientific Investigations Report 2016–5034, 

37 p., 2 app. [Also available at https://doi.org/10.3133/

sir20165034.]

Eggleston, Jack, and Pope, Jason, 2013, Land subsidence 

and relative sea-level rise in the southern Chesapeake Bay 

region: U.S. Geological Survey Circular 1392, 30 p. [Also 

available at https://doi.org/10.3133/cir1392.]
62 Continuing Progress Toward a National Assessment of Water Availability and Use

Finkelstein, J.S., and Nardi, M.R., 2015, Geospatial compilation and digital map of center-pivot irrigated areas in the 

mid-Atlantic region, United States: U.S. Geological Survey 

Data Series 932, accessed May 25, 2016, at https://doi.

org/10.3133/ds932.

Masterson, J.P., and Pope, J.P., 2016, Sustainability of groundwater supplies in the Northern Atlantic Coastal Plain aquifer 

system: U.S. Geological Survey Fact Sheet 2016–3046, 6 p. 

[Also available at https://doi.org/10.3133/fs20163046.]

Masterson, J.P., Pope, J.P., Fienen, M.N., Monti, Jack, Jr., 

Nardi, M.R., and Finkelstein, J.S., 2016a, Assessment of 

groundwater availability in the Northern Atlantic Coastal 

Plain aquifer system from Long Island, New York, to North 

Carolina: U.S. Geological Survey Professional Paper 1829, 

76 p. [Also available at https://doi.org/10.3133/pp1829.]

Masterson, J.P., Pope, J.P., Fienen, M.N., Monti, Jack, Jr., 

Nardi, M.R., and Finkelstein, J.S., 2016b, Documentation of 

a groundwater flow model developed to assess groundwater 

availability in the Northern Atlantic Coastal Plain aquifer 

system from Long Island, New York, to North Carolina: 

U.S. Geological Survey Scientific Investigations Report 

2016–5076, 70 p. [Also available at https://doi.org/10.3133/

sir20165076.]

Masterson, J.P., Pope, J.P., Monti, Jack, Jr., Nardi, M.R., 

Finkelstein, J.S., and McCoy, K.J., 2013, Hydrogeology 

and hydrologic conditions of the Northern Atlantic Coastal 

Plain aquifer system from Long Island, New York, to North 

Carolina: U.S. Geological Survey Scientific Investigations 

Report 2013–5133, 76 p. [Also available at https://doi.

org/10.3133/sir20135133.]

Pope, J.P., Andreasen, D.C., McFarland, E.R., and Watt, M.K., 

2016, Digital elevations and extents of regional hydrogeologic units in the Northern Atlantic Coastal Plain aquifer 

system from Long Island, New York, to North Carolina: 

U.S. Geological Survey Data Series 996, 28 p. [Also available at https://doi.org/10.3133/ds996.]

Glacial Aquifer System

Bayless, E.R., Arihood, L.D., Reeves, H.W., Sperl, B.J.S., Qi, 

S.L., Stipe, V.E., and Bunch. A.R., 2017, Maps and grids 

of hydrogeologic information created from standardized 

water-well drillers’ records of the glaciated United States: 

U.S. Geological Survey Scientific Investigations Report 

2015–5105, 34 p. [Also available at https://doi.org/10.3133/

sir20155105.]

Callegary, J.B., Kikuchi, C.P., Koch, J.C., Lilly, M.R., and 

Leake, S.L., 2013, Review—Groundwater in Alaska (USA): 

Hydrogeology Journal, v. 21, no. 1, p. 25 (abstract). [Also 

available at https://doi.org/10.1007/s10040-012-0940-5.] 

Feinstein, D.T., Fienen, M.N., Reeves, H.W., and Langevin, 

C.D., 2016, A semi-structured MODFLOW-USG model to 

evaluate local water sources to wells for decision support: 

Groundwater, v. 54, no. 4, p. 532–544. [Also available at 

https://doi.org/10.1111/gwat.12389.]

Fienen, M.N., Nolan, B.T., and Feinstein, D.T., 2016, Evaluating the sources of water to wells—Three techniques for 

metamodeling of a groundwater flow model: Environmental 

Modelling & Software, v. 77, p. 95–107. [Also available at 

https://doi.org/10.1016/j.envsoft.2015.11.023.]

Fienen, M.N., Nolan, B.T., Feinstein, D.T., and Starn, J.J., 

2015, Metamodels to bridge the gap between modeling and 

decision support: Groundwater, v. 53, no. 4, p. 511–512. 

[Also available at https://doi.org/10.1111/gwat.12339.]

Fienen, M.N., and Plant, Nathaniel, 2014, A cross-validation 

package driving Netica with Python: Environmental Modelling & Software, v. 63, p. 14–23. [Also available at https://

doi.org/10.1016/j.envsoft.2014.09.007.]

McMahon, P.B., Böhlke, J.K., Dahm, K.G., Parkhurst, D.L., 

Anning, D.W., and Stanton, J.S., 2015, Chemical considerations for an updated national assessment of brackish groundwater resources: Groundwater, v. 54, no. 4, 

p. 464–475. [Also available at https://doi.org/10.1111/

gwat.12367.]

Williston and Powder River Aquifer System

Long, A.J., Aurand, K.R., Bednar, J.M., Davis, K.W., Mckaskey, J.D.R.G., and Thamke, J.N., 2014, Conceptual model 

of the uppermost principal aquifer systems in the Williston and Powder River structural basins, United States and 

Canada: U.S. Geological Survey Scientific Investigations 

Report 2014–5055, 41 p., 1 app. [Also available at https://

doi.org/10.3133/sir20145055.]

Thamke, J.N., LeCain, G.D., Ryter, D.W., Sando, Roy, 

and Long, A.J., 2014, Hydrogeologic framework of the 

uppermost principal aquifer systems in the Williston and 

Powder River structural basins, United States and Canada: 

U.S. Geological Survey Scientific Investigations Report 

2014–5047, 38 p. [Also available at https://doi.org/10.3133/

sir20145047.]
Appendix 2. Regional Groundwater Availability Study Publications 63

Hawaii Volcanic-Rock Aquifer System

Engott, J.A., Johnson, A.G., Bassiouni, Maoya, Izuka, S.K., 

and Rotzoll, Kolja, 2017, Spatially distributed groundwater 

recharge for 2010 land cover estimated using a water-budget 

model for the Island of O‘ahu, Hawai‘i (ver. 2.0, December 

2017): U.S. Geological Survey Scientific Investigations 

Report 2015–5010, 49 p. [Also available at https://doi.

org/10.3133/sir20155010.] 

Izuka, S.K., Engott, J.A., Rotzoll, Kolja, Bassiouni, Maoya, 

Johnson, A.G., Miller, L.D., and Mair, Alan, 2018, Volcanic 

aquifers of Hawai‘i—Hydrogeology, water budgets, and 

conceptual models (ver. 2.0, March 2018): U.S. Geological 

Survey Scientific Investigations Report 2015-5164, 158 p. 

[Also available at https://doi.org/10.3133/sir20155164.] 

Johnson, A.G., Engott, J.A., Bassiouni, Maoya, and Rotzoll, 

Kolja, 2018, Spatially distributed groundwater recharge 

estimated using a water-budget model for the Island of 

Maui, Hawai`i, 1978–2007 (ver. 2.0, February 2018): 

U.S. Geological Survey Scientific Investigations Report 

2014–5168, 53 p. [Also available at https://doi.org/10.3133/

sir20145168.] 

Ozarks Plateaus Aquifer System

Hays, P.D., Knierim, K.J., Breaker, B.K., Westerman, D.A., 

and Clark, B.R., 2016, Hydrogeology and hydrologic conditions of the Ozark Plateaus aquifer system: U.S. Geological Survey Scientific Investigations Report 2016–5137, 

61 p., 2 app. [Also available at https://doi.org/10.3133/

sir20165137.]

Knierim, K.J., Nottmeier, A.M., Worland, Scott, Westerman, 

D.A., and Clark, B.R., 2016, Groundwater withdrawal rates 

from the Ozark Plateaus aquifer system, 1900 to 2010: U.S. 

Geological Survey data release, accessed September 29, 

2017, at https://doi.org/10.5066/F7GQ6VV1.

Knierim, K.J., Nottmeier, A.M., Worland, Scott, Westerman, 

D.A., and Clark, B.R., 2017, Challenges for creating a 

site-specific groundwater-use record for the Ozark Plateaus 

aquifer system (central USA) from 1900 to 2010: Hydrogeology Journal, v. 25, no. 6, p. 1779–1793. [Also available at 

https://doi.org/10.1007/s10040-017-1593-1.]

Knierim, K.J., Wagner, D.M., Roland, V.L., and Nottmeier, 

A.M., 2015, Ozark Plateaus seepage run dataset, southern 

Missouri and northern Arkansas, 1982–2006: U.S. Geological Survey data release, accessed September 29, 2017, at 

https://doi.org/10.5066/F7W9577Q.

Nottmeier, A.M., 2015, Regional potentiometric surface of the 

Ozark aquifer in Arkansas, Kansas, Missouri, and Oklahoma, November 2014–January 2015: U.S. Geological 

Survey Scientific Investigations Map 3348, 1 sheet. [Also 

available at https://doi.org/10.3133/sim3348.]

Nottmeier, A.M., 2016, Regional potentiometric surface dataset of the Ozark aquifer in Arkansas, Kansas, Missouri, and 

Oklahoma, November 2014–January 2015: U.S. Geological Survey data release, accessed September 29, 2017, at 

https://doi.org/10.5066/F74747XS.

Turner, N.L., Knierim, K.J., and Kresse, Timothy, 2016, 

Sinkholes and springs of the Ozark Physiographic Province, 

northern Arkansas, from topographic maps: U.S. Geological Survey data release, accessed September 29, 2017, at 

https://doi.org/10.5066/F7XK8CNZ.

U.S. Geological Survey, 2015, Groundwater, a source to 

streams in the Ozark Plateaus: U.S. Geological Survey 

video, accessed November 9, 2017, at https://www.youtube.

com/watch?v=CTw4cfZyTMw.

Westerman, D.A., Gillip, J.A., Richards, J.M., Hays, P.D., and 

Clark, B.R., 2016a, Altitudes and thicknesses of hydrogeologic units of the Ozark Plateaus aquifer system in 

Arkansas, Kansas, Missouri, and Oklahoma: U.S. Geological Survey data release, accessed September 29, 2017, at 

https://doi.org/10.5066/F7HQ3X0T.

Westerman, D.A., Gillip, J.A., Richards, J.M., Hays, P.D., and 

Clark, B.R., 2016b, Altitudes and thicknesses of hydrogeologic units of the Ozark Plateaus aquifer system in Arkansas, Kansas, Missouri, and Oklahoma: U.S. Geological 

Survey Scientific Investigations Report 2016–5130, 32 p. 

[Also available at https://doi.org/10.3133/sir20165130.]

Pennsylvanian and Mississippian Aquifer System 

of the Appalachian Plateaus

Ladd, D.E., 2016, Mean-annual and mean-seasonal waterbudget estimates from a Soil-Water-Balance model of the 

Appalachian Plateaus, 1980 through 2011: U.S. Geological Survey data release, accessed September 29, 2017, at 

https://doi.org/10.5066/F7X06544.

McCoy, K.J., Yager, R.M., Nelms, D.L., Ladd, D.E., Monti, 

Jack, Jr., and Kozar, M.D., 2015, Hydrologic budget and 

conditions of Permian, Pennsylvanian, and Mississippian aquifers in the Appalachian Plateaus Physiographic 

Province (ver. 1.1, October 2015): U.S. Geological Survey 

Scientific Investigations Report 2015–5106, 77 p. [Also 

available at https://doi.org/10.3133/sir20155106.]
64 Continuing Progress Toward a National Assessment of Water Availability and Use

Nelms, D.L., Messinger, Terence, and McCoy, K.J., 2015, 

Annual and average estimates of water-budget components 

based on hydrograph separation and PRISM precipitation for gaged basins in the Appalachian Plateaus region, 

1900–2011: U.S. Geological Survey Data Series 944, 10 p. 

[Also available at https://doi.org/10.3133/ds944.]

Yager, R.M., McCoy, K.J., Voss, C.I., Sanford, W.E., and 

Winston, R.B., 2017, The role of uplift and erosion in the 

persistence of saline groundwater in the shallow subsurface: 

Geophysical. Research Letters, v. 44, no. 8, p. 3672–3681. 

[Also available at https://doi.org/10.1002/2017GL072980.]

Northwest Volcanic Aquifer Study

Burns, E.R., Gannett, M.W., Sherrod, D.R., Keith, M.K., 

Curtis, J.A., Bartolino, J.R., Engott, J.A., Scandella, B.P., 

Stern, M.A., and Flint, A.L., 2017, Geothermal implications of a refined composition-age geologic map for the 

volcanic terranes of southeast Oregon, northeast California, 

and southwest Idaho, USA: Geothermal Resources Council 

Transactions, v. 41. [Also available at https://pubs.er.usgs.

gov/publication/70191365.]

Burns, E.R., Zhu, Yonghui, Zhan, Hongbin, Manga, 

Michael, Williams, C.F., Ingebritsen, S.E., and Dunham, J.B., 2017, Thermal effect of climate change on 

groundwater-fed ecosystems: Water Resources Research, 

v. 53, no. 4, p. 3341–3351. [Also available at https://doi.

org/10.1002/2016WR020007.]
For additional information, contact:

Melinda S. Dalton

Coordinator—Water Availability and Use Science Program

U.S. Geological Survey

12201 Sunrise Valley Drive

Reston, VA 20192

or visit our website at:

https://water.usgs.gov/wausp/

Prepared by USGS West Trenton Publishing Service Center
Evenson and others—Report to Congress—Continuing Progress Toward a National Assessment of Water Availability and Use—Circular 1440

ISSN 1067-084X (print)

ISSN 2330-5703 (online)

https://doi.org/10.3133/circ1440