U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2020–3044

August 2020

Water Priorities for the Nation—U.S. Geological Survey 

Integrated Water Availability Assessments

Printed on recycled paper

The United States faces growing challenges to its water supply, infrastructure, and aquatic ecosystems because of population 

growth, climate change, floods and droughts, and aging water delivery systems. To help address these challenges, the U.S. Geological 

Survey (USGS) Water Resources Mission Area (WMA) has established the Integrated Water Availability Assessments (IWAAs) to 

capitalize on the operational and scientific strengths of the USGS and engage in these complex societal issues. Substantial advances in 

water science, together with innovations in technological and computational capabilities, have resulted in sophisticated new monitoring 

and modeling capabilities that can provide managers with the data, decision support systems, information, and insights needed to 

address today’s water-availability challenges.

Integrated Water Availability Assessments

The USGS IWAAs will provide nationally and regionally 

consistent assessments of water for human and ecological needs 

and identify factors that limit water availability at a range of 

spatial and temporal scales. When fully implemented, the IWAAs 

will do the following:

1. evaluate current water supplies and demands, along with 

the factors that affect them (fig. 1);

2. quantify long-term trends 

in water-availability metrics and 

their drivers;

3. provide seasonal to 

decadal forecasts of water 

availability; and

4. support water resource 

management through the design 

of management-relevant integrated data and water-availability 

assessment products (fig. 2).

The goals and implementation of IWAAs, and particularly

the relevance and utility of IWAA products, will rely on 

effective communication, coordination, and collaboration 

with the Federal agencies and Tribal, State, regional, and local 

partners that need or are supporting an enhanced understanding 

of water availability.

Figure 1. Numerous factors affect water availability. Water 

availability reflects the quantity, timing, quality, and use of 

water resources. More specifically, 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 human and 

environmental/ecological uses.

Figure 2. The USGS National IWAAs concept map shows daily 

estimates of natural water storage (water on the landscape such as 

standing water, snowpack, soil water, and shallow groundwater) for 

the conterminous United States. The USGS map is the first product 

to visualize a current, quantitative view of water availability at the 

national scale.

National Assessments

The national IWAA will provide a near-real-time census 

of water resources at the subwatershed scale (tracts of 10,000–

40,000 acres). When fully realized, the census will provide 

assessments and forecasts of the amount of surface water and 

groundwater available to support various uses over spatial extents 

including individual watersheds, major hydrologic regions, and 

the Nation. Assessments will also provide information on the 

quality of available source water and the socioeconomic factors 

that affect demands on water supplies. This national census—and 

the data, research, and network of models it comprises—will 

be supported by next-generation observation systems and an 

evolving hydrologic cycle and water-quality modeling capacity 

being developed by the USGS (fig. 3).

Latest natural water storage

Very high High Normal

Low Very low

EXPLANATION

Water quantity

Timing of water delivery

Water quality

Human and ecological use

Water

availability

National and Regional IWAAs
Figure 3. The Integrated Water Availability Assessments program 

is one of four priority programs in the USGS WMA designed to help 

address current and future societal issues associated with water 

availability.

Regional Assessments

Models, tools, and supporting data developed for the 

national IWAAs will be augmented by more refined information 

from select regional studies and assessments to improve national 

IWAA water-availability models. The specific information 

needs of each regional IWAA will be informed by local 

hydrologic conditions and input from partners and stakeholders 

regarding information gaps and resource management needs. 

Improved estimates and understanding of the regional water 

budget; priority components of water availability; and controls 

on water quantity, quality, and use will be used to meet regional 

and local information and tool needs and to inform and improve 

the water-availability assessments and forecasts made by the 

national IWAAs.

In 2019, the USGS began a pilot regional IWAA in the 

Delaware River Basin (fig. 4). This pilot is providing an opportunity to explore new approaches to assess factors that affect 

water supply and demand. Pilot regional IWAA activities in the 

Delaware River Basin focus on the following:

• understanding historical drought events and future

water supply under drought conditions,

• assessing the effect of water quality on water

availability for human and ecological purposes,

• developing new data processing techniques and models

to predict water use, and

• evaluating streamflow trends as model input toward use

in forecasting reservoir storage.

In 2020, the USGS selected the Upper Colorado River 

Basin (fig. 4) to perform a fully implemented regional IWAA. 

This basin was selected to provide an opportunity to improve 

regional water-availability prediction in snowmelt dominated 

systems. Ultimately, a new regional IWAA will be added 

each year, as funding is available, until 10 basins identified 

by a basin selection team have implemented IWAA projects. 

The basin selection team developed criteria that accounted 

for environmental, engineered, and social settings; ecological 

resources; water demand; water quality and water quantity; and 

changes to water resources in different regions.

The USGS WMA plays an essential role in meeting the 

current and future challenges associated with managing the 

Nation’s water resources (National Academies of Science, 

Engineering, and Medicine, 2018). The IWAAs program is one of 

four priority programs established by the USGS WMA (fig. 3) to 

help ensure that its observational networks and renowned water 

science and research continue to provide timely and actionable 

information to stakeholders, managers, and decision makers.

Figure 4. The Upper and Lower Delaware River Basins (left) and 

Upper Colorado River Basin (right) were selected in 2019 and 2020, 

respectively, to implement regional IWAAs. Additional basins are 

anticipated to be added each year through 2029.

Reference Cited

National Academies of Sciences, Engineering, and Medicine, 

2018, Future water priorities for the Nation—Directions for 

the U.S. Geological Survey Water Mission Area: Washington, 

D.C., The National Academies Press, 96 p. [Also available at

https://doi.org/10.17226/25134.]

NEVADA

IDAHO WYOMING

COLORADO

NEW MEXICO

ARIZONA

UTAH

PA

MD

DE

NJ

NY

CT

Schu ylkill R. Lehigh

River

Delaware

River

Colorad oRi ver

Atlantic Ocean

40°

35°

115° 110°

Base from U.S. Geological Survey National Map, 1:2,000,000, Albers Equal-Area Conic

projection, standard parallels 29°30' N. central meridian 96°00' W. latitude of origin 23°00' N.

North American Datum of 1983, Map image is the intellectual property of Esri and is used

herein under license. Copyright © 2014 Esri and its licensors. All rights reserved. Base modified

from Esri digital data, 1:72,000 (Esri, 2014)

0 100 MILES

0 100 KILOMETERS

42°

40°

76° 74°

0 40 MILES

0 40 KILOMETERS

Integrated Water Availability Assessments (IWAA) IWAAs examine the supply,

use, and availability of the Nation’s water. These regional and national

assessments evaluate water quantity and quality in both surface and

groundwater, as related to human and ecosystem needs and as affected

by human and natural influences.

Integrated Water Prediction (IWP) IWP builds a powerful set of modeling tools

to predict the amount and quality of surface and groundwater, now and into the

future. These models use the best available science to provide information for

more rivers and aquifers than can be directly monitored.

Next Generation Water Observing System (NGWOS) NGWOS collects real-time

data on water quantity and quality in more affordable, rapid, and widespread

ways than has previously been possible. The flexible monitoring approach

enables USGS networks to evolve with new technology and emerging trends.

National Water Information System (NWIS) Modernization NWIS data systems

that house USGS water information are being modernized to maximize data

integrity, simplify data delivery to the general public, and automate early

warning to enable faster response times during water emergencies.

Assess

Predict

Observe

Deliver

Photograph credits:

Water shortage on corn, Bob Nichols, used with permission, 

U.S. Department of Agriculture. All other images from

U.S. Geological Survey

By Mark P. Miller, Brian R. Clark, Sandra M. Eberts, Patrick M. Lambert, and

Patricia Toccalino

For more information: 

USGS Water Resources Mission Area,

Integrated Water Availability Assessments Program 

https://www.usgs.gov/mission-areas/water-resources/science/integratedwater-availability-assessments-iwaas

Publishing support by the

Reston and Rolla Publishing Service Centers

ISSN 2327-6916 (print)

ISSN 2327-6932 (online)

https://doi.org/10.3133/fs20203044