This study presents an updated scoping assessment of current and future water withdrawal requirements, compared with water availability, resolved at the level of counties across the contiguous United States. This report will be useful to power sector environment, generation, and delivery managers; power sector planners; government energy and water resource managers and regulators; and the municipal and agricultural sectors.

Background

Over a decade ago, the Electric Power Research Institute (EPRI) identified water availability constraints as a major issue facing current operations and future development of the electric power sector in the United States and internationally and initiated research to assess and reduce both current and future vulnerabilities to water shortages. Since then, the U.S. Congress; government agencies at national, regional, state, and local levels; environmental nongovernmental organizations; professional technical societies; universities; research organizations; and water users across all economic and social sectors have initiated discussions and studies of the energy/water nexus.

Objective

• To present the results of a national framing analysis of future freshwater availability and demand in the United States
• To develop simple indices of vulnerability to water availability shortages

Approach

The basic analytical approach used in this work, documented in EPRI report 1005474, can be divided into two steps. In the first step, water withdrawals for individual sectors are compared to an estimate of water availability, computed as the difference between precipitation and evapotranspiration. These calculations can be used to gauge water availability constraints. In the second step, future water demand is projected under different scenarios and compared to available water supply. In a previous EPRI report (1017946, Managing Water Resource Requirements for Growing Electric Generation Demands), the relative merits and recommended uses of this methodology and more detailed analytical methodologies for assessing and managing water resources are described. In addition to providing a national-scale overview, this report identifies areas of concern for one or more sustainability metrics, such as excessive groundwater withdrawal, rapid projected growth in municipal or electric power demand, and need for new storage. These areas can then be studied with more detailed analytical tools.

Results

In a pattern consistent over the last two to three decades, thermoelectric cooling and agricultural withdrawals are the major components of total freshwater withdrawals (40% and 36%, respectively, of 2005 freshwater withdrawals). Of the 40% withdrawn for thermoelectric cooling, 36% is for once-through cooling systems and 4% is for recirculating cooling systems. Public municipal and domestic withdrawal is about 14% of the total, with all other sectors constituting the remaining 10%. Water-use data exhibit considerable complexity in spatial patterns, with large thermoelectric withdrawals located in the eastern United States, and much of the irrigation withdrawal located in the western United States. Municipal withdrawals occur throughout the United States, although per capita withdrawals are much lower in the Northeast and Midwest, compared to the rest of the country.

Many regions of the United States, especially the High Plains states and portions of the Southwest, continue to have significant groundwater overdraft, estimated at a total of 34.8 bgd in 2005 (about 10% of the total U.S. freshwater withdrawal, or about a third of all groundwater withdrawal). The water supply sustainability risk index shows that the most significant future water stresses are in the southern/southwestern United States and in the Great Plains states. When the locations of existing power generation facilities are overlaid on the map of the index, roughly 250,000 MW of generation, or about a quarter of the U.S. total, are in counties that are associated with some type of water sustainability concern.