Energy-Water Nexus:
The Energy Sector’s Water Use
Nicole T. Carter
Specialist in Natural Resources Policy
August 30, 2013
Congressional Research Service
7-5700
www.crs.gov
R43199
Energy-Water Nexus: The Energy Sector’s Water Use
Summary
Water and energy are critical resources that are reciprocally linked; this interdependence is often
described as the water-energy nexus. Meeting energy-sector water needs, which are often large,
depends upon the local availability of water for fuel production, hydropower generation, and
thermoelectric power plant cooling. The U.S. energy sector’s use of water is significant in terms
of water withdrawals and water consumption. In 2005, thermoelectric cooling represented 41% of
water withdrawn nationally, and 6% of water consumed nationally. The majority of the
anticipated increase in water consumption by 2030 is attributed to domestic biofuel and oil and
gas production. Policy makers at the federal, state, and local levels are faced with deciding
whether to respond to the growing water needs of the energy sector, and if so, which policy levers
to use (e.g., tax incentives, loan guarantees, permits, regulations, planning, or education). Many
U.S. energy sector water decisions are made by private entities, and state entities have the
majority of the authority over water use and allocation policies and decisions.
For fuel production, water is either an essential input or is difficult and costly to substitute, and
degraded water is often a waste byproduct that creates management and disposal challenges. U.S.
unconventional oil and gas production has expanded quickly since 2008, and U.S. natural gas and
coal exports may rise. This has sparked interest in the quantities of water and other inputs
“embedded” in these resources, as well as the wastes produced (e.g., wastewaters from oil and
gas extraction). Much of the growth in water demand for unconventional fuel production is
concentrated in regions with already intense competition over water (e.g., tight gas and other
unconventional production in Colorado, Eagle Ford shale gas and oil in south Texas), preexisting
water concerns (e.g., groundwater decline in North Dakota before Bakken oil development), or
regions with abundant, but ecologically sensitive surface water resources (e.g., Marcellus shale
region in Pennsylvania and New York).
Conventional hydropower accounts for approximately 8% of total U.S. net electricity generation,
and more than 80% of U.S. electricity is generated at thermoelectric facilities that depend on
cooling water. Water availability issues, such as regional drought, low flow, or intense
competition for water can curtail hydroelectric and thermoelectric generation. An assessment of
the drought vulnerability of electricity in the western United States found broad resiliency, while
also identifying the Pacific Northwest and the Texas grid at higher risk. Future withdrawals
associated with electric generation may grow slightly, remain steady, or decline depending on a
number of factors. These include reduced generation from facilities using once-through cooling
because of compliance with proposed federal cooling water intake regulations or shifts in how
electricity is generated (e.g., less from coal and more from wind and natural gas).
Energy choices represent complex tradeoffs; water use and wastewater byproducts are two of
many factors to consider when making energy choices. For many policymakers, concerns other
than water—low-cost reliable energy, energy independence and security, climate change
mitigation, public health, and job creation—are more significant drivers of their positions on
energy policies.
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Energy-Water Nexus: The Energy Sector’s Water Use
Contents
Water for Energy Primer .................................................................................................................. 1
Energy-Sector Water Use and Vulnerability Is Receiving Increased Attention .................. 1
Relevant Data and Research Are Improving; Significant Gaps Remain ............................. 2
Fuel Production ................................................................................................................................ 3
Unconventional Oil and Gas Production Often Concentrates Water Use
Geographically and Temporally ....................................................................................... 3
Available Data on Water Use Remain Problematic ............................................................. 4
Fuel Production Remains Vulnerable to Water-Related Disruptions .................................. 5
Produced Water Represents Management Challenges and Some Opportunities ................. 5
Electric Grid and Generation ........................................................................................................... 7
Grid-Level Drought Vulnerability Exists in Select Basins .................................................. 7
Hydropower Vulnerability Is Poorly Documented, But Data Are Expected to
Improve ............................................................................................................................ 8
Thermoelectric Cooling Represents Difficult Tradeoffs ..................................................... 8
Many Power Plants Produce Wastewaters .......................................................................... 9
Policy Response Options and Considerations.................................................................................. 9
Tables
Table 1. Policy Responses to Water Demands of Energy Sector ................................................... 10
Contacts
Author Contact Information........................................................................................................... 11
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Energy-Water Nexus: The Energy Sector’s Water Use
ater and energy are critical resources that are reciprocally linked. Energy is required for
the pumping, conveyance, treatment and conditioning, and distribution of water and
Wfor collection, treatment, and discharge of wastewater. Likewise, as described in this
report, meeting energy sector needs depends upon the local availability of water, often in large
quantities, for mineral fuel production,1 hydropower, and thermoelectric power plant cooling.
This interdependence is often described as the water-energy nexus.
This report addresses how the U.S. energy sector uses and relies on water; it provides summary
descriptions divided into four topics: (1) Water for Energy Primer, (2) Fuel Production,
(3) Electric Grid and Generation, (4) Policy Response Options and Considerations. CRS Report
R43200, Energy-Water Nexus: The Water Sector’s Energy Use, addresses the related topic of
energy needs of the water sector.
Water for Energy Primer
Energy-Sector Water Use and Vulnerability Is Receiving Increased Attention
Available projections estimate that, by 2030, U.S. water consumption will increase by 7% above
the level consumed in 2005; 85% of this growth is attributed to the energy sector (including
biofuels).2 The U.S. energy sector’s use of water is significant in terms of water withdrawals and
water consumption.3
• Energy Sector: While agriculture dominates U.S. water consumption (71%), the
energy sector (including biofuels, thermoelectric, and fuel production) is the
second-largest consumer at 14%, and domestic and public uses are third at 7%.4
Multiple factors contribute to the energy sector being the fastest-growing water
consumer. Biofuels produced from irrigated feedstocks play a significant role, as
well as expanding production of onshore unconventional oil and gas and hydro-
stimulation of aging wells.
• Electric Generation: Water dependence is a risk for hydroelectric and
thermoelectric generation. During low-flow or high-heat events, water intakes
and high water temperatures may harm or limit thermoelectric cooling. In 2005,
thermoelectric cooling water represented 41% of water withdrawn nationally,5
and 6% of water consumed nationally.6 Also, the withdrawal and discharge of
cooling water can harm aquatic organisms.
1 In this report, production encompasses extraction and processing of fuels.
2 This report complements CRS Report R41507, Energy’s Water Demand: Trends, Vulnerabilities, and Management,
by Nicole T. Carter, which provides more information on how and where the energy sector is using water in the United
States.
3 Consumption represents the water not available for immediate subsequent use. In the energy sector, water is
consumed when it enters the atmosphere (e.g., power plant evaporative cooling towers), is lost to geologic formations,
is sufficiently degraded to require permanent disposal, or needs treatment before use in freshwater applications or
return to the environment.
4 CRS Report R41507, Energy’s Water Demand: Trends, Vulnerabilities, and Management.
5 U.S. Geological Survey, Estimated Use of Water in the United States in 2005 (Circular 1344: 2009).
6 D. Elcock, “Future U.S. Water Consumption: The Role of Energy Production,” Journal of the American Water
Resources Association, vol. 46, no. 3 (June 2010), pp. 447-480, hereinafter referred to as Elcock 2010.
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Energy-Water Nexus: The Energy Sector’s Water Use
• Fuel Production: Water is either an essential input or is difficult and costly to
substitute; degraded water is often a waste byproduct.
• Efficiency and Conservation: Reducing energy demand through energy and
water efficiency7 and more water-efficient generation (e.g., electricity from
wind,8 photovoltaics, or natural gas) can reduce water demand. Current water
efficiency incentives in fuel production include minimizing water management
costs and reducing operational disruptions.
• Embedded Water: U.S. unconventional oil and gas production has expanded
quickly since 2008 due to the combined use of hydraulic fracturing and
horizontal drilling techniques for well development.9 This expansion has sparked
interest in the quantities of water and other inputs “embedded” in energy
resources.
Relevant Data and Research Are Improving; Significant Gaps Remain
In 2012, the Government Accountability Office in Energy-Water Nexus: Coordinated Federal
Approach Needed to Better Manage Energy and Water Tradeoffs stated that “making effective
policy choices will continue to be challenging without more comprehensive data and research.”10
Improving data on water use by the energy sector is challenging for a number of reasons. For
example, much of the U.S. energy sector is private; data consistency, accuracy, and currency are
problematic; and maintenance of high-quality data for an evolving and dispersed industry is
costly.
While data challenges exist, access to relevant research and data is improving. The Department of
Energy (DOE) disseminates energy-water related studies on a public online platform.11 The
reports mentioned in the box below provide additional information on the energy-water nexus
while also identifying areas needing improved understanding. While these reports differ in their
focus, they each mention the stresses that climate change places on the energy-water nexus.
7 R. Young and E. Mackres, Tackling the Nexus: Exemplary Programs that Save Both Energy and Water, Washington,
DC: American Council for an Energy-Efficient Economy, 2013.
8 One study found that expanding the nation’s electricity portfolio to 20% wind by 2030 would reduce water
consumption by 1.2 billion gallons daily compared to expanding the current electricity mix. The water saved would be
41% in the Midwest/Great Plains, 29% in the West, 16% in the Southeast, and 14% in the Northeast (DOE, 20% Wind
Energy by 2030: Increasing Wind Energy’s Contribution to U.S. Electricity Supply, July 2008,
http://www1.eere.energy.gov/wind/pdfs/41869.pdf).
9 Hydraulic fracturing is a technique developed initially to stimulate oil production from wells in declining oil
reservoirs. The technique now is widely used to initiate oil and gas production in unconventional (low-permeability) oil
and gas formations that were previously inaccessible. Fracturing is currently used in more than 90% of new oil and gas
wells. Hydraulic fracturing involves injecting large volumes of water, sand (or other propping agent), and specialized
chemicals under pressure into a well to fracture the formations holding trapped oil or gas.
10 U.S. Government Accountability Office (GAO), Energy-Water Nexus: Coordinated Federal Approach Needed to
better Manage Energy and Water Tradeoffs, GAO-12-880, September 2012, http://www.gao.gov/assets/650/
648306.pdf.
11 The site links to over 150 items related to energy-water issues: http://en.openei.org/wiki/Water_and_energy_studies.
Also the Energy Information Agency in recent years has increased the type and frequency of data collection on power
plant cooling systems. More state level data is being collected; for example, the Railroad Commission of Texas
required oil and gas operators to disclose on FracFocus (http://fracfocus.org/) water volumes and chemicals used for
hydraulic fracturing after February 2012.
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Reports Linking Energy-Water Nexus to Climate Change
U.S. government reports and reports by stakeholders are increasingly addressing the links between energy, water, and
climate change. Examples include the following reports:
•
January 2013, National Climate Assessment and Development Advisory Committee, draft Third
Climate Assessment Report (available at http://ncadac.globalchange.gov/). This draft report discussed how co-
occurrence of heat waves and droughts can amplify impacts on water and electricity supply and demand, which
can affect the energy sector in multiple and cascading ways. The report stated (p. 167 and p. 397, respectively)
that “both episodic and long-lasting changes in water availability will constrain different forms of energy
production,” and “dependence of energy systems on land availability and water supplies will influence their
development and constrain some options for reducing greenhouse gas emissions.” It also noted (p. 387) that
“jointly considering risks, vulnerabilities, and opportunities associated with energy, water and land use is difficult,
but can improve the analysis of options for reducing climate change impacts.” Recommendations for related
research were included in a technical report developed to support the assessment effort (Pacific Northwest
National Laboratory, Climate and Energy-Water-Land System Interactions, March 2012, http://www.pnnl.gov/main/
publications/external/technical_reports/PNNL-21185.pdf).
•
July 2013, Department of Energy (DOE), U.S. Energy Sector Vulnerabilities to Climate Change and
Extreme Weather (available at http://energy.gov/sites/prod/files/2013/07/f2/20130710-Energy-Sector-
Vulnerabilities-Report.pdf). The report (p. i) stated the following when discussing the impacts of climate change
on the energy sector and the potential for cascading and compounding impacts:
Some of these effects, such as higher temperatures of ambient water used for cooling, are
projected to occur in all regions. Other effects may vary more by region, and the vulnerabilities
faced by various stakeholders may differ significantly depending on their specific exposure to the
condition or event. However, regional variation does not imply regional isolation as energy
systems have become increasingly interconnected. Compounding factors may create additional
challenges. For example, combinations of persistent drought, extreme heat events, and wildfire
may create short-term peaks in demand and diminish system flexibility and supply, which could
limit the ability to respond to that demand.
The report identified a number of opportunities to enhance information, tools, and practices to reduce the
energy sector’s climate vulnerabilities. Some of the opportunities identified (p. 44) included: better regional and
local characterization of climate trends and extreme weather relevant to the energy sector (e.g., water
availability, likelihood and magnitude of droughts); better characterization of the aggregate vulnerabilities of the
energy sector to climate change and interdependencies with other sectors leading to cascading impacts;
improved understanding of potential uses and chal enges of advanced cooling technologies and alternative water
sources; and additional assessments of impacts to hydropower.
•
July 2013, Alliance for Water Efficiency and the American Council for an Energy-Efficient Economy, Water-Energy
Nexus Research: Recommendations for Future Opportunities (available at http://www.allianceforwaterefficiency.org/
WE-WhitePaper-PR.aspx). Its recommendations included continuing investigations into the water energy
tradeoffs of differing resource development and management choices; identifying regulatory barriers to co-
implementation of energy and water efficiency programs; developing water and energy industry-accepted
protocols for efficiency programs; and assessing potential impacts to water supplies and quality from energy
resource development and identifying solutions to mitigate these impacts.
Fuel Production
Unconventional Oil and Gas Production Often Concentrates Water Use
Geographically and Temporally
Regional water resource opportunities and challenges for fuel production vary based on several
factors, including (1) which fuel is being produced in the region, (2) the local and regional
significance of its water use, and (3) regional conditions for management of wastewaters.
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Energy-Water Nexus: The Energy Sector’s Water Use
• Much of the growth in water demand for unconventional fuel production is
concentrated in regions with already intense competition over water (e.g., tight
gas and other unconventional production in Colorado, Eagle Ford shale gas and
oil in south Texas), preexisting water concerns (e.g., groundwater decline in
North Dakota before Bakken oil development), or abundant but ecologically
sensitive surface water resources (e.g., Marcellus shale region in Pennsylvania
and New York).
• The cumulative water needs of multiple drilling and fracturing operations may be
locally or temporally significant. Often many shale gas, tight gas, and tight oil
wells are located in close proximity to each other as a formation is developed,
with many wells being drilled and fractured from the same location. Water use
for these wells is concentrated in the early stages of well development, usually in
the first few weeks. Once the well is producing, little or no water is required
unless refracturing is performed. How much water is used for well development
is highly variable both across and within formations.
• Data on source water remain sparse. Groundwater often is used for shale
operations when it is available and access is permitted. Surface waters also are
used, but may require transport by truck. In cases of limited water access, well
developers also have obtained water by purchasing it from municipalities or
paying individual land owners for their supplies.
Available Data on Water Use Remain Problematic
As of mid-2013, gaps remained in the availability of authoritative and recent data on the amounts
of freshwater consumed and wastewater produced in fuel production. Available data indicate the
following:
• The amount of water needed per unit of fuel produced—referred to as the water
intensity of a fuel—ranges from conventional natural gas at the lowest end (less
than 1 gallons of water per MMBtu);12 coal, unconventional gas, and uranium
mining and enrichment next (roughly 1 to 10 gallons per MMBtu); oil next (10 to
100 gallons per MMBtu);13 and irrigated biofuels at the upper end (100 to 1,000
gallons per MMBtu).14 The water intensity of conventional and unconventional
oil produced using different techniques remains poorly documented. The water
intensity for hydraulically fractured wells often is less notable than the
concentrated, simultaneous demand for water for hydraulic fracturing in a region
where many wells are being developed concurrently.
12 MMBtu represent 1 million British thermal units which is a commonly used unit of energy.
13 Oil is produced by a variety of techniques, some of which can be particularly water-intensive (e.g., water flooding).
Oil shale is largely not discussed herein. Oil shale is distinct from the tight oil produced from shale formations. Oil
shale’s near-term impacts on water resources are limited by the relatively small scope of anticipated near-term
development (GAO, Unconventional Oil and Gas Production: Opportunities and Challenges of Oil Shale
Development, Washington, D.C, 2012).
14 International Energy Agency, World Energy Outlook 2012, Paris, 2012; E. Mielke, et al., Water Consumption of
Energy Resource Extraction, Processing, and Conversion, Cambridge, Massachusetts: Harvard Kennedy School, 2010;
World Energy Council, Water for Energy, London: World Energy Council, 2010.
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Energy-Water Nexus: The Energy Sector’s Water Use
• Despite the recent increase in water demand for hydraulic fracturing, water use
for stimulating oil production from conventional wells through water flooding
and enhanced oil recovery have represented the largest water use by the oil and
gas sector in the United States.15 The use of these techniques is anticipated to
increase; to what extent saline, produced waters, or freshwater will be used is less
clear. Limited data on production rates and quantities for many saline aquifers
can be a disincentive to their use.
• Each fuel and production technique presents its own risks, potential water quality
impacts,16 and wastewater issues; also, some techniques may be more water-
efficient but less efficient at recovering energy resources.17 Data remain poor on
the range of “produced water” quantities and qualities derived from conventional
and unconventional fuel production.
Fuel Production Remains Vulnerable to Water-Related Disruptions
The vulnerability of fuel production to freshwater availability is receiving attention in part
because of increasing water demands (e.g., population growth) and concerns over changes to
water supplies (e.g., drought and climate change).
• Instances of low flow and drought conditions have reduced the availability and
increased the cost of water for operations in some locations (e.g., Susquehanna
River basin in VA, WV, and PA, and Eagle Ford Shale region in TX). No analysis
is available of the risk posed by a multi-year drought in areas of intense water use
for energy (e.g., North Dakota) and how to manage the risk.
• Fossil fuel transport also may be disrupted by water conditions, such as flood-
induced pipeline breaks resulting from riverbed scouring, flood- or storm-related
refinery or distribution system disruptions (e.g., Hurricane Sandy disruptions),
and drought- or flood-impaired fuel transport. No analysis of energy sector
transport risks is available.
Produced Water Represents Management Challenges and Some Opportunities
Produced water—wastewaters (often saline) brought to the surface by oil and gas wells—
represents the largest byproduct of fuel production. Approximately 2.3 billion gallons are
produced daily from onshore oil and gas wells in the United States.18 For oil wells, this represents
15 M. Matichich, The Changing Value of Water to the US Economy: Implications from Five Industrial Sectors, Boston:
CH2M Hill, 2012.
16 A discussion of water quality impacts is beyond the scope of this report. For a regional discussion of water quality
concerns associated with shale gas, see CRS Report R42333, Marcellus Shale Gas: Development Potential and Water
Management Issues and Laws, by Mary Tiemann et al. For a general discussion, see L. Allen, et al., Fossil Fuels and
Water Quality, in P. Gleick, The World’s Water. Vol. 7, Washington, DC: Island Press, 2012, pp. 73-96.
17 Beyond water considerations, fuel production can have other development impacts (e.g., roads, housing). For
example, see CRS Report R42611, Oil Sands and the Keystone XL Pipeline: Background and Selected Environmental
Issues, coordinated by Jonathan L. Ramseur.
18 This compares to an estimated 4.6 billion gallons per day of freshwater used for fuel production.
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an average ratio of 7.6:1 of produced water to oil produced. By 2025, as a result of aging wells
with decreasing oil production, the ratio is expected to average 12:1 for onshore crude oil.19
• U.S. produced water is primarily from conventional oil and gas and coal bed
methane (CBM).20 Research indicates that shale gas wells may produce less
produced water per unit of recovered gas than conventional natural gas wells.21
Disposal of produced water from shale development and associated fracking has
received more attention recently than wastewaters from conventional production
because of the rate of increase in shale development and its associated
wastewaters in locations that are not accustomed to oil and gas development.
• Management of produced water is evolving rapidly, with different techniques
dominating in different locations and raising concerns related to water quality
and seismicity. Where deep wells for the permanent disposal of the produced
water are limited, producers increasingly are recycling and reusing produced
water as the fracturing fluid. This reduces the amount of freshwater resources
needed for subsequent wells and relieves stress on disposal sites. At the same
time, reuse of produced waters may increase the transport and handling of saline
waters, potentially increasing a risk pathway.
Recent state actions and anticipated federal actions are affecting or are anticipated to affect the
management of produced water.
• In Texas, produced water generally is disposed through deep-well injection (often
on-site) or evaporation ponds; interest in reuse is increasing as the result of
limited water availability in some regions (e.g., West Texas) and recent drought
conditions. In May 2013, the Texas legislature clarified liability and ownership of
produced waters transferred among oil and gas operators for purposes of
recycling for a beneficial reuse.22
• Pennsylvania regulations constraining surface water disposal wastewaters from
shale gas production and the limited in-state deep well-injection options have
resulted in a rapid increase in the rate of produced water recycling for shale gas
fracking.23 Operators in Pennsylvania are required to prepare a wastewater source
reduction strategy to maximize recycling and reuse.
19 Global Water Intelligence, Water’s growing role in oil and gas, March 2011, http://www.globalwaterintel.com/
archive/12/3/market-profile/waters-growing-role-oil-and-gas.html.
20 CBM production generally requires the dewatering of a coal formation for the gas to be released; the quantity and
quality of CBM produced waters varies widely across formations (e.g., salinities ranging from freshwater or more
saline than seawater). For more on CBM water issues, see National Research Council, Management and Effects of
Coalbed Methane Produced Water in the Western United States, National Academies Press, August 2010.
21 B. Lutz, A. Lewis, and M. Doyle, “Generation, transport, and disposal of wastewater associated with Marcellus Shale
gas development,” Water Resources Research, 49 (2013).
22 H.B. 2767 (Texas). Also in 2013, the Railroad Commission of Texas stopped requiring a recycling permit if
operators are recycling on their own leases or transferring fluids to another operator’s lease for recycling ("Railroad
Commission Today Adopts New Recycling Rules to Help Enhance Water Conservation By Oil & Gas Operators,”
press release, March 26, 2013).
23 J. Logan, et al., Natural Gas and the Transformation of the U.S. Energy Sector: Electricity. Golden, Colorado: Joint
Institute of Strategic Energy Analysis, 2012, http://www.nrel.gov/docs/fy13osti/55538.pdf.
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• In August 2013, EPA proposed to discontinue efforts to establish discharge
standards for wastewaters from CBM under the agency’s Effluent Guidelines
Program. EPA has been unable to identify a wastewater treatment technology that
would be economically achievable.24 The agency will continue with a rulemaking
for wastewaters associated with shale gas extraction, which is expected to be
proposed in 2014.
Electric Grid and Generation
Water availability issues, such as regional drought, low flow, or intense competition for water, can
curtail hydroelectric and thermoelectric generation. Fuel and power plant choices and capital
investments made in the near term are likely to establish the trajectories for electric generation’s
long-term water use and vulnerability.
Grid-Level Drought Vulnerability Exists in Select Basins
An assessment of the drought vulnerability of electricity in the western United States found the
majority of basins showing limited risk; also, most of this risk could be mitigated by known
strategies, including maintaining excess generation and transmission capacity.25 While identifying
broad resiliency, the western U.S. assessment revealed two regions whose electric generation was
at greater risk:
• The Pacific Northwest was shown to be vulnerable because of its heavy reliance
on hydroelectric generation.
• The Texas grid was vulnerable because of heavy dependence on thermoelectric
generation that relied on surface water for cooling, and because of the region’s
vulnerability to drought and poor connections to the other U.S. grids, which
reduces the ability to purchase power to offset generation curtailment.
No similar assessment of grid drought vulnerability for the eastern United States has been
performed. (See following section, “Thermoelectric Cooling Represents Difficult
Tradeoffs,” for a discussion of electric generation in the eastern United States.)
Recent drought experiences include the following:
• In the summer of 2011, high temperatures in Texas resulted in increased
electricity demand. At the same time, the drought reduced the amount of water
available for cooling electric generators. The grid operator put into effect its
emergency action alert system, which at first recommended conservation by
customers and later deemed customer conservation critical to avoid rotating
outages. During a few days, the peak demand purchases in the real-time
wholesale electricity market were at or near the market cap (i.e., $3,000 per
24 EPA, Economic Analysis for Existing and New Projects in the Coalbed Methane Industry, EPA 820-R-13-006, July
29, 2013, http://water.epa.gov/scitech/wastetech/guide/oilandgas/unconv.cfm
25 C.B. Harto, et al., Analysis of Drought Impacts on Electricity Production in the Western and Texas Interconnections
of the United States, Oak Ridge, Tennessee: U.S. Department of Energy, 2011.
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megawatt-hour). In the end, only one Texas plant had water-curtailed generation;
others were nearing curtailment when weather conditions improved.26
• During the drought of 2012, the mid-continent electric grid avoided major
drought-related disruption. Some individual power plants curtailed operations
due to water access problems or water temperature issues; others pursued
regulatory waivers to continue operations at higher water temperatures or made
cooling system investments. Lost generation at drought-impaired facilities was
offset by other generation or purchasing power from other sources on the
wholesale market.
Hydropower Vulnerability Is Poorly Documented, But Data Are Expected to
Improve
In §9505 of P.L. 111-11, Congress required the Secretary of Energy to assess the risks posed by
climate change for water supply to federal hydroelectric power generators; the report is
anticipated in 2013. Depending on the storage capacity (and its uses) in a basin’s reservoirs,
hydropower may be vulnerable to seasonal, annual, or multi-year drought conditions. For large
reservoirs and reservoir systems, it is often the multi-year droughts that most harm generation,27
as illustrated by summer 2013 conditions in the Colorado River Basin.
Thermoelectric Cooling Represents Difficult Tradeoffs
More than 80% of U.S. electricity is generated at thermoelectric facilities that depend on cooling
water; these facilities withdraw 143 billion gallons of freshwater per day. The two common
cooling methods for thermoelectric power plants are once-through cooling and evaporative
cooling. Most once-through cooling is found at power plants located in the eastern United States
and is associated with older facilities, or is at coastal facilities using saline waters. Newer
facilities and those in more arid regions generally use evaporative cooling.
• Once-through cooling, while largely non-consumptive, requires water to be
continuously available for power plant operations.28 This reduces the ability for
this water to be put toward other water uses and can make cooling operations
vulnerable to low flows.
• Evaporative cooling withdraws much smaller volumes of water for use in a
cooling tower or reservoir, where waste heat is dissipated by evaporating the
26 During and after the summer of 2011, Texas power plant operators reduced their low water vulnerability by building
pipelines to alternative and impaired water sources, acquiring additional water rights, lowering water intake structures,
and installing additional groundwater pumping capacity. Also the Texas grid operator instituted changes to reduce its
water vulnerability. All new generation facilities as of 2013 must provide proof of water rights before being included in
grid planning (which largely determines grid access). Few data are available on the extent to which low-water
renewable technologies may be used to mitigate the Texas grid’s drought risks.
27 For example, in 2012, hydropower production nationally was above average although drought conditions covered
much of the continental United States. The Missouri River basin’s strong hydropower generation in 2012 can be
attributed to full reservoirs at the beginning of the year and the generation associated with releases of stored water to
augment low river flows.
28 Once-through cooling pulls large quantities of water off a water body, discharges the power plant’s waste heat into
the water (which may raise the temperature of the withdrawn water by 10° to 20°F), and then returns the majority of the
withdrawn water.
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cooling water. Evaporative cooling consumes more water at the facility than does
once-through cooling.
• Cooling technologies that consume less water and use degraded water supplies
may reduce freshwater use. These options include dry cooling, hybrid dry-wet
cooling, cooling with fluids other than freshwater (e.g., brackish groundwater,
produced waters), and emerging technologies. While hybrid and dry cooling
options may reduce water consumption, they can reduce operational efficiency
(potentially increasing greenhouse gas emissions) and often are more costly.
• Future withdrawals associated with electric generation may grow slightly, remain
steady, or decline depending on a number of factors, including reduced
generation from facilities using once-through cooling (industry actions resulting
from proposed federal cooling water intake regulations29 or shifts in how
electricity is generated (e.g., less from coal and more from wind and natural
gas).30 In comparison, water consumption is more likely to increase, especially if
more water-consumptive cooling is adopted (e.g., evaporative cooling) and if
current carbon capture technologies are added to power plants.
Many Power Plants Produce Wastewaters
In addition to water for cooling purposes, many power plants also use water for handling solid
waste, including ash, and for operating wet flue gas desulfurization scrubbers. According to the
U.S. Environmental Protection Agency (EPA), in 2009, power plants discharged 0.7 billion
gallons of wastewater daily. EPA recently proposed revisions to Clean Water Act rules that govern
wastewater discharges from such plants. The proposed rule would reduce the use of these process
waters by 19%-58%, depending on the regulatory option selected when the rule is finalized.31
Policy Response Options and Considerations
Policy makers at the federal, state, and local levels are faced with deciding whether to respond to
the growing water needs of the energy sector, and if so, which policy levers to use. In the United
States, private entities make many of the energy sector’s water decisions. In many cases, federal
entities lack authority over water use decisions, and states have most of the water allocation
authority. Instead of direct influence on water use, the public sector influences private water
decisions through other routes (e.g., tax incentives, loan guarantees, permits, regulations,
planning, and education). If action to manage energy-sector water issues is deemed appropriate, a
range of options are available, as shown in Table 1: minimize water use, facilitate access to water,
or improve decisions and data. Energy choices represent complex tradeoffs; water use and
wastewater byproducts are two of many factors to consider. For many policymakers, concerns
29 See CRS Report R41786, Cooling Water Intake Structures: Summary of EPA’s Proposed Rule, by Claudia Copeland.
30 Natural gas-fueled generation is generally less water-intense and less water-dependent than coal-powered electricity.
This is because many gas-fueled electric facilities use engine-based technology (National Energy Technology
Laboratory, Estimating Freshwater Needs to Meet Future Thermoelectric Generation Requirements (2009 Update),
2009).
31 U.S. Environmental Protection Agency, Technical Development Document for the Proposed Effluent Limitations
Guidelines and Standards for the Steam Electric Power Generating Point Source Category, EPA-821-R-13-002, April
2013, pp. 12-13 – 12-14.
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Energy-Water Nexus: The Energy Sector’s Water Use
other than water—low-cost reliable energy, energy independence and security, climate change
mitigation, public health, and job creation—are more significant drivers of their positions on
energy policies.
Table 1. Policy Responses to Water Demands of Energy Sector
Water Demand
Water Supply
Options for Knowledge
Management Options
Management Options
Development and Use
Minimize Energy Sector’s
Improve Energy Sector’s Access Support Informed Decision-
Growth in Water Use
to Water
Making
Promote water-efficient energy
Allocate sustainably available water,
Data and assessments; information
sources through standards,
not otherwise allocated
sharing (e.g., data and research
regulations, or incentives (e.g.,
warehousing)
rebates, water pricing)
Promote water conservation and
Facilitate transfer of water from non-
Education, training, and
efficiency in the energy sector
energy sectors (e.g., purchase of
dissemination of knowledge and
through standards, incentives,
water from municipalities, or land
information
regulations, or pricing
owners; water markets)
Promote energy conservation and
Integrated energy-water planning;
efficiency to reduce demand for
coordination of research, decisions,
energy and the embedded water
and investments
Support research, development,
Decision-support research and
scaling up, or adoption of
technical assistance; development of
technologies to reduce energy
standard protocols and codes
sector water use (e.g., public-private
research col aborations)
Source: CRS.
Analyses quickly get complex when attempting to comprehensively evaluate energy-water
tradeoffs. Some energy alternatives, such as solar photovoltaics and wind turbines, do not pose
energy-water tradeoffs, but may pose other challenges, such as intermittent production or reduced
dispatchability, which is the ability and ease with which output from an electric generation
facility can be altered. Other energy tradeoffs include transport and storage. Some fuels are easier
to store and use existing transport networks and multiple transport modes, while others may
require new or expanded infrastructure investments (e.g., pipelines). Significantly, low-carbon
energy is not necessarily low in water or environmental impact (e.g., new hydropower reservoirs,
freshwater-cooled utility-scale solar), and specific carbon mitigation policies and actions may
increase or decrease water consumption. Because of these complexities and the difficulty in
comparing different types of impacts, analyses supporting decision-making are often incomplete.
It is within this complex and confusing context that policy decisions that influence future energy
and related water policies are being made.
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Energy-Water Nexus: The Energy Sector’s Water Use
Author Contact Information
Nicole T. Carter
Specialist in Natural Resources Policy
ncarter@crs.loc.gov, 7-0854
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