ENERGY DEMANDS

ON

WATER RESOURCES

REPORT TO CONGRESS

ON THE INTERDEPENDENCY OF ENERGY AND WATER

U.S. DEPARTMENT OF ENERGY

 

 DECEMBER 2006 
2
3

PREFACE 

This report has been prepared in response to a letter to the Secretary of Energy from the 

chairmen and ranking members of the House and Senate Subcommittees on Energy and Water 

Development Appropriations, dated December 9, 2004, wherein they asked for: 

“a report to Congress on the interdependency of energy and water focusing on threats to 

national energy production resulting from limited water supplies, utilizing where possible 

the multi-laboratory Energy-Water Nexus Committee.” 

The report presents background information on the connections between energy and water, 

identifies concerns regarding water demands of energy production, and discusses science and 

technologies to address water use and management in the context of energy production and use.

 
4

CONTENTS 

Executive Summary ........................................................................................................ 9

Chapter I. Energy and Water Are Essential, Interdependent Resources...................... 13

Chapter II. Supplying Energy Requires Water and Impacts Water Quality................... 17

Water Use for Thermoelectric Power Generation....................................................... 18 

Water Use for Hydroelectric Power Generation.......................................................... 19 

Water Use for Energy Extraction and Fuel Production ............................................... 20 

Water Produced During Energy Extraction................................................................. 21 

Energy Impacts on Water Quality............................................................................... 21 

Chapter III. Supplying Water Requires Energy............................................................. 25 

Supply and Conveyance............................................................................................. 25 

Treatment and Distribution ......................................................................................... 26 

End Use of Water ....................................................................................................... 26 

Future Energy Demand for Water Supply and Treatment .......................................... 27

Chapter IV. Water Shortages and Impacts on Energy Infrastructure ........................... 29 

Water Management Challenges ................................................................................. 31 

Surface Water Concerns ............................................................................................ 32 

Groundwater Concerns .............................................................................................. 32 

Potential Impact of Future Power Generation on Water Supplies............................... 33 

Chapter V. Opportunities to Secure America’s Energy and Water Future.................... 37 

Addressing Future Water Needs in the Power Sector ................................................ 37 

Addressing Water Needs in the Emerging Fuel Sector .............................................. 43 

Addressing Future U.S. Water Needs ........................................................................ 45 

Chapter VI. Addressing Critical Energy-Water Challenges: Bridging the Gaps............ 49 

Collaboration on Critical Resource Planning .............................................................. 49 

Science and System-Based Natural Resource Policies and Regulations................... 49 

Energy-Water Infrastructure Synergies ...................................................................... 49 

Bridging the Gaps: Direction and Implementation ...................................................... 50

Appendix A: Water Use in Energy Extraction, Processing, Storage, and 

Transportation ............................................................................................................ 53 

Appendix B: Water Use in Electrical Power Generation............................................... 63

References and Bibliography ........................................................................................ 71
5

 

Figures 

Figure I-1. Examples of Interrelationships Between Water and Energy ..................................................................13 

Figure I-2. Water Shortages and Population Growth. ..............................................................................................15 

Figure II-1. Estimated Freshwater Withdrawals by Sector, 2000..............................................................................18

Figure II-2. Open-Loop Cooling System...................................................................................................................18

Figure II-3. Closed-Loop Cooling System ................................................................................................................19 

Figure II-4. Estimated Freshwater Consumption by Sector, 1995.............................................................................19 

Figure II-5. U.S. Hydropower Production.................................................................................................................19

Figure II-6. Forecast for Produced Water (Wp) from Oil and Gas Extraction ..........................................................22

Figure III-1. Percent of U.S. Electricity Consumption by Sector ...............................................................................25 

Figure III-2. Per Capita Energy Use for Water Supply and Wastewater Treatment in 2000 

and Projected for 2050. ..........................................................................................................................26 

Figure IV-1. Survey of Likely Water Shortages over the Next Decade under Average Conditions...........................29 

Figure IV-2. Examples of Energy-Water Conflicts ....................................................................................................30

Figure IV-3. Trends in Total Freshwater Withdrawals, 1950–2000...........................................................................31

Figure IV-4. Comparison of Regional Thermoelectric Generation Capacity by North 

American Electric Reliability Council Region, 1995–2025...................................................................34 

Figure IV-5. Projected Steam-Electric Generation Capacity by Type Projected from EIA Reference Case..............35 

Figure IV-6. Range of Projected Daily Freshwater Withdrawal for Thermoelectric Power Generation....................36 

Figure IV-7. Range of Projected Freshwater Consumption for Thermoelectric Power Generation ...........................36 

Figure V-1. Water Withdrawal for Power Generation...............................................................................................39 

Figure V-2. Water Consumption for Power Generation............................................................................................39 

Figure V-3. Peak Reduction from Combined Use of Solar Energy and Demand Management in a 

Residential Application..........................................................................................................................42 

Figure V-4. Water Consumption Per-Unit-Energy and Current Water Use for Fuel Extraction and Processing ......44 

Figure V-5. Degraded Water Resources of the U.S...................................................................................................46 

Figure V-6. Energy Requirements for Water Desalination .......................................................................................47

Figure V-7. U.S. Oil and Gas Resources. ..................................................................................................................48 

Tables 

Table II-1. Connections Between the Energy Sector and Water Availability and Quality........................................17 

Table III-1. Energy Requirements for Water Supply and Treatment in California ....................................................25 

Table IV-1. Examples of Declining Groundwater Levels ..........................................................................................33 

Table V-1. Water Intensity for Various Power Generation Technologies.................................................................38 
6

Acronyms 

API American Petroleum Institute 

AwwaRF Awwa Research Foundation 

bbl barrel 

boe barrel of oil equivalent 

CEC California Energy Commission 

DOE U.S. Department of Energy 

EERE Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy 

EIA Energy Information Administration, U.S. Department of Energy 

EOR Enhanced Oil Recovery 

EPRI Electric Power Research Institute 

EST Eastern Standard Time 

FE Office of Fossil Energy, U.S. Department of Energy 

ft feet 

FY fiscal year 

gal gallons 

GAO General Accounting Office 

GW gigawatt 

IGCC Integrated Gasification Combined Cycle 

kW kilowatt 

kWh kilowatt-hour 

LNG Liquefied Natural Gas 

MGD million gallons per day 

MMbbls million barrels 

MMBtu Million British Thermal Units 

MTBE methyl tertiary-butyl ether 

MW megawatt 

MWh Megawatt-hour 

MWhe Megawatt-hour of electric energy 

MWht Megawatt-hour of thermal energy 

NETL National Energy Technology Laboratory 
7

NCPA Northern California Power Authority 

NGCC Natural Gas Combined Cycle 

PV Photovoltaic 

PNM Public Service Company of New Mexico 

psi pound per square inch 

RFA Renewable Fuels Association 

SWAQ Subcommittee on Water Availability and Quality 

TVA Tennessee Valley Authority 

USDA United States Department of Agriculture 

USGS United States Geological Survey 

Wp water produced 

WW wastewater 

yr year 
8
9

Executive Summary 

For the past century, America has invested 

significant research, development, and construction funding to develop both fresh surface-water and groundwater resources. The 

result is a water infrastructure that allows us 

to harness the vast resources of the country’s 

rivers and watersheds, control floods, and 

store water during droughts to provide reliable supplies of freshwater for agricultural, 

industrial, domestic, and energy uses. During this same period, the U.S. developed 

extensive natural resources such as coal, oil, 

natural gas, and uranium and created an 

infrastructure to process and transport these 

resources in an efficient and cost-effective 

manner to consumers. These two achievements have helped stimulate unprecedented 

economic growth and development. 

However, as population has increased, demand for energy and water has grown. 

Competing demands for water supply are 

affecting the value and availability of the 

resource. Operation of some energy facilities has been curtailed due to water concerns, and siting and operation of new energy facilities must take into account the 

value of water resources. U.S. efforts to replace imported energy supplies with nonconventional domestic energy sources have 

the potential to further increase demand for 

water. 

Energy Demands on Water Resources responds to a Congressional directive within a 

letter to the Secretary of Energy from the 

chairmen and ranking members of the House 

and Senate Subcommittees on Energy and 

Water Development Appropriations, dated 

December 9, 2004, wherein they asked for 

“a report on energy and water interdependencies, focusing on threats to national energy production that might result from limited water supplies.” 

This report draws on the work of the multilaboratory Energy-Water Nexus committee 

as well as reports and papers from researchers in other federal agencies and elsewhere. 

ENERGY AND WATER INTERDEPENDENCIES 

Water is an integral element of energy resource development and utilization. It is 

used in energy-resource extraction, refining 

and processing, and transportation. Water is 

also an integral part of electric-power generation. It is used directly in hydroelectric 

generation and is also used extensively for 

cooling and emissions scrubbing in thermoelectric generation. For example, in calendar year 2000, thermoelectric power generation accounted for 39 percent of all freshwater withdrawals in the U.S., roughly 

equivalent to water withdrawals for irrigated 

agriculture (withdrawals are water diverted 

or withdrawn from a surface-water or 

groundwater source) (Hutson et al., 2004). 

Water withdrawal statistics for thermoelectric power are dominated by power 

plants that return virtually all the withdrawn 

water to the source. While this water is 

returned at a higher temperature and with 

other changes in quality, it becomes 

available for further use. Many power 

plants, including most of those built since 

1980, withdraw much less water but consume most of what they withdraw by evaporative cooling. In 1995, agriculture 

accounted for 84 percent of total freshwater 

consumption. Thermoelectric power 

accounted for 3.3 percent of total freshwater 

consumption (3.3 billion gallons per day) 

and represented over 20 percent of 

nonagricultural water consumption (Solley 

et al., 1998). 
10

The Energy Information Administration 

(EIA) projects, assuming the latest Census 

Bureau projections in its reference case, the 

U.S. population to grow by about 70 million 

in the next 25 years and electricity demand 

to grow by approximately 50 percent (EIA, 

2006). The EIA reference case is a 

projection which assumes that current laws, 

regulations, policies, technological progress 

and consumer preferences continue through 

the projection period as they have in the 

past. The EIA reference case provides a useful baseline against which possible changes 

to these assumptions can be evaluated. 

Much of this growth is expected to occur in 

the Southeast, Southwest, and Far West, 

where water is already in limited supply. 

In a business-as-usual scenario, consumption of water in the electric sector could 

grow substantially, though increased demand for water would provide an incentive 

for technologies that reduce water use, thus 

dampening the increase in water use. Technologies are available that can reduce water 

use in the electric sector, including alternative cooling for thermoelectric power plants, 

wind power, and solar photovoltaics, but 

cost and economics, among other factors, 

have limited deployment of these technologies. 

In contrast, water use in the extraction and 

processing of transportation fuels is relatively small. However, as the U.S. seeks to 

replace imported petroleum and natural gas 

with fuels from domestic sources, such as 

biofuels, synfuel from coal, hydrogen, and 

possibly oil shale, the demand for water to 

produce energy fuels could grow significantly. 

Growth in energy demand occurs when 

freshwater resources and overall freshwater 

availability become strained from limitations 

on supply and increasing domestic, 

agricultural, and environmental demands. 

Few new reservoirs have been built since 

1980, and fresh surface-water withdrawals 

have leveled off at about 260 billion gallons 

per day. Many regions depend on 

groundwater to meet increasing water demands, but declining groundwater tables 

could severely limit future water availability. Some regions have seen groundwater 

levels drop as much as 300 to 900 feet over 

the past 50 years because of the pumping of 

water from aquifers faster than the natural 

rate of recharge. A 2003 General Accounting Office study showed that most state water managers expect either local or regional 

water shortages within the next 10 years under average climate conditions (GAO, 

2003). Under drought conditions, even 

more severe water shortages are expected. 

Depending on the water quality needs for 

particular applications, freshwater supplies 

can be augmented with degraded or brackish 

water. Water quantities available for use are 

dependent on the water qualities needed for 

each use. Increased use of brackish or degraded water may be required in some areas 

if water users can accept the quality limitations or can afford the cost of energy and 

infrastructure for water treatment. 

ENERGY DEMANDS ON WATER 

RESOURCES 

These trends in energy use, water availability, and water demand suggest that the U.S. 

will continue to face issues related to the 

development, utilization, and management 

of the critical resources of water and energy. 

Increasing population will increase demand 

for water for direct use as well as for energy 

and agriculture. Historically, water withdrawals for domestic supplies have grown at 

about the same rate as the population, 

though recent trends show that rate growing 

about half the rate of population growth because of the implementation of water conservation measures in many regions (Hutson 

et al., 2004; GAO, 2003). If new power 

plants continue to be built with evaporative 

cooling, consumption of water for electrical 

energy production could more than double 

by 2030 from 3.3 billion gallons per day in 
11

1995 to 7.3 billion gallons per day (Hoffmann et al., 2004). 

Consumption by the electric sector alone 

could equal the entire country’s 1995 

domestic water consumption. Consumption 

of water for extraction and production of 

transportation fuels from domestic sources 

also has the potential to grow substantially. 

Meanwhile, climate concerns and declines in 

groundwater levels suggest that less freshwater, not more, may be available in the 

future. 

Therefore, the U.S. should carefully consider energy and water development and 

management so that each resource is used 

according to its full value. Since new technologies can reduce water use, there will be 

a great incentive for their development by 

the public and private sectors. Given current 

constraints, many areas of the country will 

have to meet their energy and water needs 

by properly valuing each resource, rather 

than following the current U.S. path of 

largely managing water and energy separately while making small improvements in 

freshwater supply and small changes in 

energy and water-use efficiency. 

FEDERAL ROLES IN MEETING 

ENERGY-WATER CHALLENGES 

While regulation of electric and water utilities and resource allocations is primarily a 

state or local responsibility, federal agencies 

such as the Bureau of Reclamation manage 

some of our largest energy and water resources in cooperation with state and local 

entities. Expansion of this cooperation 

could improve the country’s ability to 

address these energy challenges. 

Collaboration on Resource Planning – 

Collaboration on energy and water resource 

planning is needed among federal, regional, 

and state agencies as well as with industry 

and other stakeholders. In most regions, 

energy planning and water planning are 

done separately. The lack of integrated 

energy and water planning and management 

has already impacted energy production in 

many basins and regions across the country. 

For example, in three of the fastest growing 

regions in the country, the Southeast, 

Southwest, and the Northwest, new power 

plants have been opposed because of 

potential negative impacts on water supplies 

(Tucson Citizen, 2002; Reno-Gazette 

Journal, 2005; U.S. Water News Online, 

2002 and 2003; Curlee, 2003). Also, recent 

droughts and emerging limitations of water 

resources have many states, including 

Texas, South Dakota, Wisconsin, and 

Tennessee, scrambling to develop water use 

priorities for different water use sectors 

(Clean Air Task Force, 2004a; Milwaukee 

Journal Sentinel, 2005; GAO, 2003; Curlee, 

2003; Hoffman, 2004; U.S. Water News 

Online, 2003). Also see Chapter IV, Figure 

IV-2 for other examples. 

Mechanisms, such as regional natural resources planning groups, are needed to foster collaboration between stakeholders and 

regional and state water and energy planning, management, and regulatory groups 

and agencies. These collaborative efforts 

are needed to ensure proper evaluation and 

valuation of water resources for all needs, 

including energy development and generation. 

Science and System-Based Natural 

Resource Policies and Regulations – 

Often, polices or regulations developed to 

support or enhance one area, such as increasing domestic energy supplies through 

enhanced oil recovery (EOR), could have 

unintended negative impacts on regional or 

national freshwater availability or water 

quality. System-level evaluations by stakeholders and government agencies can be 

used to assess the impact of current or proposed natural resource policies and regulations and improve future energy 

development and water availability. 
12

Energy Water Infrastructure Synergies – 

When the energy infrastructure is evaluated 

in a system context, significant improvements in energy and water conservation can 

often be realized through implementation of 

innovative processes or technologies, colocation of energy and water facilities, or 

improvements to energy and water infrastructures. Past investments in the water 

infrastructure by creating dams and surfacewater reservoirs in the U.S. over the past 80 

years have significantly improved the availability of water for some applications and 

decreased its availability for other applications. There will continue to be competition 

for water resources between different users, 

and ways to reduce these conflicts through 

coordinated infrastructure development 

would be beneficial. 

ADDRESSING THE CHALLENGES 

Available surface water supplies have not 

increased in 20 years, and groundwater 

tables and supplies are dropping at an alarming rate. New ecological water demands and 

changing climate could reduce available 

freshwater supplies even more. 

At the same time, populations continue to 

grow and move to areas with already limited 

water supplies. The growing competition of 

water availability for energy production and 

electric-power generation has already been 

documented in many river basins. 

Possible changes in energy strategies in the 

electricity or transportation sectors could put 

an even larger burden on freshwater supplies 

and consumption. As a result, the value of 

water may increase, impacting energy costs 

and providing incentives for developing and 

implementing approaches to decrease the 

water intensity of the energy sector. While 

there have been significant improvements in 

water-use and energy-use efficiency and 

conservation, market and political (e.g., 

state) forces will continue to expand these 

efforts to meet the growing energy and 

water demands. 

Two reports currently under development, 

the Subcommittee on Water Availability and 

Quality (SWAQ) strategic plan for federal 

science and technology to support water 

availability and quality, and the Department 

of Energy's Energy-Water Science and 

Technology Research Roadmap, will provide insight into emerging energy-water 

challenges. The two efforts are independent 

but closely related. 

The SWAQ was established in 2003 under 

the National Science and Technology 

Council Committee on Environment and 

Natural Resources and is comprised of the 

25 federal agencies with responsibility for 

the science and technology of water availability and quality. Their role is to coordinate a multiyear plan to improve research to 

understand the processes that control water 

availability and quality, and to collect and 

make available the data needed to ensure an 

adequate water supply for the Nation’s future. Many of the energy and water interdependencies and challenges identified in this 

report to Congress fall within the SWAQ 

charter and should be considered by the 

SWAQ. 

Congress provided funding in fiscal year 

(FY) 2005 for the U.S. Department of 

Energy (DOE) to initiate an Energy-Water 

Science and Technology Research 

Roadmap. The Roadmap process started in 

August 2005 and will be completed by the 

end of 2006. 

By the end of 2006, the combined efforts of 

the SWAQ and the Energy-Water Science 

and Technology Research Roadmap efforts 

should provide a detailed understanding of 

the major energy-water interdependencies, 

issues, needs, and challenges across the 

country. The results and conclusions from 

these efforts should be considered to help 

guide programs and approaches to address 

emerging energy and water challenges.
13

Chapter I. Energy and Water Are Essential, Interdependent Resources 

A strategic goal of the United States 

Department of Energy is 

Promoting America’s energy security 

through reliable, clean, and affordable 

energy (USDOE, 2006a). 

The availability of adequate water supplies 

has an impact on the availability of energy, 

and energy production and generation activities affect the availability and quality of 

water. In today’s economies, energy and 

water are linked, as illustrated in Figure I-1. 

Each requires the other. As these two resources see increasing demand and growing 

limitations on supply, energy and water 

must begin to be managed together to maintain reliable energy and water supplies. 

The interaction of energy and water supplies 

and infrastructures is becoming clearer. 

Low water levels from drought and competing uses have limited the ability of power 

plants to generate power (Columbia Basin 

News, 2006; also see Chapter IV, Figure IV2). Additionally, water levels in aquifers in 

many regions of the U.S. have declined significantly, increasing energy requirements 

for pumping, and, in some cases, leading to 

ground subsidence issues. 

Figure I-1. Examples of Interrelationships Between Water and Energy 
14

Lack of water for thermoelectric power plant 

cooling and for hydropower can constrain 

generation and has the potential to increase 

demand for technologies that reduce the 

water intensity of the energy sector. 

At the same time, demand for energy continues to grow. In its reference case, the Energy Information Administration projects 

that demand for energy supplies from 2003 

to 2030 will grow as follows: petroleum, 38 

percent; natural gas, 20 percent; coal, 54 

percent; nuclear power, 14 percent; and renewable energy, 58 percent. Demand for 

electricity from all sources is projected to 

increase by 53 percent (EIA, 2006). 

Unfortunately, freshwater withdrawals 

already exceed precipitation in many areas 

across the country, as illustrated in Figure 

I-2 (composed from information from EPRI, 

2003a; Solley et al., 1998; and Campbell, 

1997). The figure shows the ratio of total 

freshwater withdrawals in all counties in the 

U.S. divided by available precipitation 

(precipitation minus evapotranspiration) 

shown as a percentage. The figure provides 

an indication of the areas where current 

water demands are being met with 

significant groundwater pumping or 

transport of surface water from other 

locales. 

The shortfalls are most dramatic in the 

Southwest, in the high plains, in California, 

and in Florida. Population growth in these 

regions between 2000 and 2025 is estimated 

to be 30 to 50 percent (Campbell, 1997). 

This additional population will place an 

increased demand on water and energy, 

given current trends in energy and water use 

efficiency. 

The challenges are not limited to these regions, however. For example, the data presented from EPRI show that nearly the 

entire western shoreline of Lake Michigan 

has water demand above available precipitation (EPRI, 2003a). Groundwater 

levels along the southwestern shores of Lake 

Michigan have declined hundreds of feet 

since predevelopment and by 1980 had 

reached maximum withdrawals of up to 

900 feet near Chicago (Bartolino and 

Cunningham, 2003; Granneman et al., 

2000). While subsequent relocation of 

withdrawals has caused groundwater levels 

near Chicago to rise several hundred feet 

(Granneman et al., 2000), levels are declining as much as 17 feet per year in some 

locations (Michigan Land Use Institute, 

2003).
15

Source: Solley, 1998; EPRI 2003, A Survey of Water Use

Projected

Population

Growth

From Campbell, 1997

+20%

+29%

+10%

+81%

+68%

+37%

+36%

%

Figure I-2. Water Shortages and Population Growth 

(Water shortage is defined as total freshwater withdrawal divided by available precipitation. 

Water withdrawal data are taken from Solley et al., 1998; ratios shown are taken from EPRI, 

2003a; and projected population growth is taken from Campbell, 1997.) 
16
17

Chapter II. Supplying Energy Requires Water 

and Impacts Water Quality 

Water is used throughout the energy sector, 

including in resource extraction, refining 

and processing, electric power generation, 

storage, and transport. The energy sector 

also can impact water quality via waste 

streams, runoff from mining operations, 

produced water from oil and gas extraction, 

and air emissions that may affect downwind 

watersheds. Examples of interactions, both 

large and small, are shown in Table II-1. 

Many energy facilities, such as power 

plants, mines, and refineries, are very large 

and can have a significant impact on local 

water supplies and water quality. For example, water withdrawals for thermoelectric 

power generation alone are comparable to 

water withdrawals for irrigation. Each 

represents about 40 percent of the national 

water withdrawals (water that is diverted or 

withdrawn from a surface-water or groundwater source), as shown in Figure II-1 

(Hutson et al., 2004). However, of the 132 

billion gallons per day of freshwater withdrawn for thermoelectric power plants in 

1995, all but about 3.3 billion gallons per 

day (3 percent) was returned to the source. 

While this water was returned at a higher 

temperature and with other changes in water 

quality, it was available for further use. In 

contrast, of the 134 billion gallons per day 

withdrawn for irrigation in 1995, 81 billion 

gallons per day were consumed by evaporation and transpiration (60 percent), and 

another 25 billion gallons per day (19 

percent) were reported as lost in conveyance 

(but may have percolated to a groundwater 

source and been available for reuse) (Solley 

et al., 1998). 

Table II-1. Connections Between the Energy Sector and Water Availability and Quality 

 *Impaired water may be saline or contain contaminants 

Energy 

Element

Connection to 

Water Quantity

Connection to 

Water Quality

Refining and Processing 

Traditional 

Oil and Gas 

Refining 

Water needed to 

refine oil and gas 

End use can impact 

water quality 

Biofuels and 

Ethanol 

Water for growing 

and refining 

Refinery wastewater treatment 

Synfuels and 

Hydrogen 

Water for synthesis 

or steam reforming 

Wastewater 

treatment 

Energy Transportation and Storage 

Energy 

Pipelines 

Water for 

hydrostatic testing 

Wastewater requires 

treatment 

Coal Slurry 

Pipelines 

Water for slurry 

transport; water not 

returned 

Final water is poor 

quality; requires 

treatment 

Barge 

Transport of 

Energy 

River flows and 

stages impact fuel 

delivery 

Spills or accidents 

can impact water 

quality 

Oil and Gas 

Storage 

Caverns 

Slurry mining of 

caverns requires 

large quantities of 

water 

Slurry disposal 

impacts water 

quality and ecology 

**Includes solar and geothermal steam-electric plants 

Energy 

Element 

Connection to 

Water Quantity 

Connection to 

Water Quality 

Energy Extraction and Production 

Oil and Gas 

Exploration 

Water for drilling, 

completion, and 

fracturing 

Impact on shallow 

groundwater quality 

Oil and Gas 

Production 

Large volume of 

produced, impaired 

water* 

Produced water can 

impact surface and 

groundwater 

Coal and 

Uranium 

Mining 

Mining operations 

can generate large 

quantities of water 

Tailings and 

drainage can impact 

surface water and 

ground-water 

Electric Power Generation 

Thermoelectric 

(fossil, 

biomass, 

nuclear) 

Surface water and 

groundwater for 

cooling** and 

scrubbing 

Thermal and air 

emissions impact 

surface waters and 

ecology 

Hydroelectric Reservoirs lose large 

quantities to 

evaporation 

Can impact water 

temperatures, 

quality, ecology 

Solar PV and 

Wind 

None during operation; minimal water use 

for panel and blade washing 
18

U.S. Freshwater Withdrawals, 345 Bgal/day

Public Supply, 13%

Industrial, 5%

Thermoelectric, 

39%

Irrigation, 40%

Aquaculture, 1%

Livestock, 1%

Domestic, 1%

Mining, 1%

Figure II-1. Estimated Freshwater 

Withdrawals by Sector, 2000 

(Hutson et al., 2004) 

An overview of the most significant current 

uses of water in the energy sector is given in 

this chapter. A more detailed overview of 

water use in the energy sector is provided in 

Appendices A and B. 

WATER USE FOR THERMOELECTRIC POWER GENERATION 

Thermoelectric generating technologies that 

use steam to drive a turbine generator require cooling to condense the steam at the 

turbine exhaust. These plants can receive 

heat from a variety of sources, including 

coal, nuclear, natural gas, oil, biomass (e.g., 

wood and crop waste), concentrated solar 

energy, and geothermal energy. The amount 

of freshwater required is significant: 59 

billion gallons of seawater and 136 billion 

gallons of freshwater per day (Hutson et al., 

2004). 

Prior to 1970, most thermoelectric power 

plants were built adjacent to surface waters 

in the vicinity of large population centers 

(EIA, 2004b). These older plants commonly 

use open-loop cooling. They withdraw 

water for cooling and discharge the heated 

water back to the source, as shown in Figure 

II-2. The discharged water can lead to some 

enhanced evaporative loss to the 

atmosphere. EPRI estimates these losses to 

be about 1 percent (EPRI, 2002a). This 

estimate is reflected in water consumption 

data for open-loop cooling reported in 

Chapter V. About 31 percent of current 

U.S. generating capacity is composed of 

thermoelectric generating stations using 

open-loop cooling. 

While these plants do not consume large 

volumes of water, the availability of large 

volumes of water is critical to plant operation. Additionally, the intake and discharge 

of large volumes of water by these plants 

have potential environmental consequences. 

Aquatic life can be adversely affected by 

impingement on intake screens or entrainment in the cooling water and by the discharge of warm water back to the source. 

Enactment of the Federal Water Pollution 

Control Act in 1972 placed restrictions on 

the impact of open-loop cooling on the environment. In addition, demand for electric 

power has been high in areas where surface 

waters are not plentiful, such as the Southwest. Only about ten steam-electric plants 

have been built with open-loop cooling since 

1980 (EIA, 2004b). Nevertheless, existing 

open-loop cooling systems may have several 

decades of service life and therefore continue to represent a significant demand for 

water, though an increased value of water 

could provide an incentive for cooling 

improvements that need less water. 

Condenser

River

Steam

Condensate

Figure II-2. Open-Loop Cooling System 
19

Most thermoelectric plants installed since 

the mid-1970s are cooled by evaporation of 

the cooling water (EIA, 2004b). As shown 

in Figure II-3, water is pumped in a closed 

loop through a cooling tower or a cooling 

pond. These systems withdraw less than 

5 percent of the water withdrawn by openloop systems, but most of the water withdrawn is lost to evaporation. 

Condenser

Pump

Steam

Condensate

Freshwater

Supply

Blowdown

Cooling

Tower

Water

Vapor

Figure II-3. Closed-Loop Cooling System 

Total freshwater consumption for the 

thermoelectric power sector was 3.3 billion 

gallons per day in 1995 (Solley et al., 1998). 

While that was only 3.3 percent of total U.S. 

water consumption (which amounts to about 

100 billion gallons/day), it was nearly 20 

percent of nonagricultural consumption, as 

shown in Figure II-4. 

U.S. Freshwater Consumption, 100 Bgal/day

Livestock

3.3%

Thermoelectric

3.3%

Commercial

1.2%

Domestic

7.1%

Industrial

3.3%

Mining

Irrigation 1.2%

80.6%

Figure II-4. Estimated Freshwater 

Consumption by Sector, 1995 

(Solley et al., 1998) 

WATER USE FOR HYDROELECTRIC 

POWER GENERATION 

Hydroelectric power is an important component of U.S. electricity generation. Hydropower supplied from 5.8 percent to 10.2 

percent of generated power between 1990 

and 2003 (EIA, 2005). As shown in Figure 

II-5, hydroelectric power production varies 

greatly with the amount of water available, 

depending upon weather patterns and local 

hydrology, as well as on competing water 

uses, such as flood control, water supply, 

recreation, and in-stream flow needs (e.g., 

navigation and the aquatic environment). 

In addition to being a major source of baseload generating capacity in some regions, 

hydroelectric power plays an important role 

in stabilizing the electrical transmission grid 

and in meeting peak loads, reserve requirements, and other ancillary electrical energy 

needs because it can respond very quickly to 

changing demand. 

0

50

100

150

200

250

300

350

400

1940 1950 1960 1970 1980 1990 2000 2010

Year

Billion Kilowatthours

Recent range (±35%) 

happened with essentially 

no change in capacity

 Figure II-5. U.S. Hydropower Production 

(EIA, 2005) 

Hydroelectric plant design and operation is 

highly diverse. Projects vary from large, 

multipurpose storage reservoirs to 

run-of-river projects that have little or no 

active water storage. Approximately half 

the U.S. hydropower capacity is federally 

owned and operated; the other half is nonfederal projects that are regulated by the 

Federal Energy Regulatory Commission. 
20

There are more than ten times more nonfederal hydropower projects in the U.S. than 

federal projects. 

Water flow through hydroelectric turbines 

averages 3,160 billion gallons/day (Solley et 

al., 1998) or nearly ten times the withdrawals of water from rivers. The United 

States Geological Survey (USGS) does not 

report it as withdrawn water because it remains in the river and, in fact, can be used 

multiple times by successive dams. However, reservoir operation can shift water 

releases in time relative to natural flows. 

When hydropower projects involve large 

storage reservoirs, evaporation of water 

from those reservoirs can be a significant 

consumptive use. With an average loss for 

U.S. hydroelectric reservoirs of 4,500 

gal/MWh (Gleick, 1994) and annual generation of approximately 300 million MWh 

(EIA 2005), total losses are estimated at 3.8 

billion gallons per day. However, the water 

storage in hydropower reservoirs usually has 

multiple purposes; thus, hydroelectric power 

is not the only cause of these evaporative 

losses. 

WATER USE FOR ENERGY 

EXTRACTION AND FUEL 

PRODUCTION 

Water consumption for energy extraction 

and fuel production is included by the USGS 

under the industrial/mining sector. While 

water is used in the conventional extraction 

of resources, more water is used in conversion to useful forms of energy, whether that 

is converting coal or uranium to electricity 

as described above or converting petroleum 

into fuels such as gasoline or diesel. Refinery use of water for processing and cooling 

is about 1 to 2.5 gallons of water for every 

gallon of product (Gleick, 1994). The 

United States refines nearly 800 million 

gallons of petroleum products per day (EIA, 

2006). Therefore, refining consumes 1 to 2 

billion gallons of water per day. Natural gas 

processing and pipeline operations consume 

an additional 0.4 billion gallons per day 

(Gleick, 1994; EIA, 2006). 

In the mining sector, water is used to cool or 

lubricate cutting and drilling equipment for 

dust suppression, fuel processing, and 

revegetation when mining and extraction are 

complete. Estimates of water for coal mining vary from 1 to 6 gallons per million 

British thermal units (MMBtu), depending 

on the source of the coal (Gleick, 1994; 

Lancet, 1993). Combining those figures 

with 2003 coal production data (EIA, 2006), 

total water use for coal mining is estimated 

at 70 to 260 million gallons per day. 

Oil shale is emerging as another potential 

source of oil. Initial recovery work to date 

has focused on mining and above-ground 

processing (retorting) that consumes 2 to 5 

gallons of water per gallon of refinery-ready 

oil (Bartis, 2005). Currently, only limited 

amounts of oil shale are being developed, 

but based on current oil demands and prices, 

opportunities may exist for significant expansion in the future. On the other hand, 

because oil shale resources are predominantly located in areas where water has a 

high value, oil shale development may be 

constrained by both water availability and 

value. More recently, an electrically driven 

in situ underground process is being prototyped that does not directly use water, 

potentially significantly reducing the water 

intensity of future oil shale development 

(Bartis, 2005). 

Biofuels currently provide about 3 percent 

of U.S. transportation fuel, with more than 

130 ethanol and biodiesel plants in operation 

producing over 4 billion gallons of biofuel 

each year (Renewable Fuels Association, 
21

2005 and 2006; National Biodiesel Board, 

2005). The most water-intensive aspect of 

biofuel production is growing the feedstock, 

with water consumption for refining 

generally similar to that for oil refining. 

When the feedstock is corn or soy (used to 

make ethanol and biodiesel, respectively) 

and grown on irrigated land, then the water 

consumption per gallon of fuel produced can 

exceed the water consumption for refining 

by a factor of one thousand based on USDA 

data (USDA, 2004a). 

Initial extraction of conventional oil and gas 

requires minimal consumption of water. 

Rather, significant quantities of water, called 

produced water, are extracted with the oil 

and gas. Produced water can range from 

being nearly fresh to being hypersaline 

brine, with the vast majority being at least as 

saline as seawater. As oil wells age, enhanced recovery techniques are used to 

extract additional oil. Many of these 

recovery techniques involve injection of 

water or steam into the well, and some are 

very water-intensive. Gleick reports water 

consumption of 2 to 350 gallons of water per 

gallon of oil extracted, depending upon the 

recovery enhancement process. However, 

most of the water used for these purposes is 

not otherwise usable (Gleick, 1994). Most 

produced water associated with onshore 

production is injected back into the 

producing zones to enhance production or 

into other formations well below any usable 

groundwater resources. 

WATER PRODUCED DURING 

ENERGY EXTRACTION 

Significant quantities of produced water are 

extracted with oil and gas, as shown in 

Figure II-6. In 1995, the American 

Petroleum Institute (API) estimated that oil 

and gas operations generated 18 billion 

barrels of produced water (49 million 

gallons per day), compared to total annual 

petroleum production of 6.7 billion barrels 

of oil equivalent (both onshore and offshore 

production, including crude oil, natural gas, 

and natural gas liquids production) (API, 

2000). Such produced water varies in 

quality; with treatment, some might be used 

for other purposes. API indicates that in 

1995, approximately 71 percent of produced 

water was recycled and used for EOR. 

The amount of water produced per well 

varies greatly. For example, water produced 

by coal-bed natural gas extraction can vary 

from 7 barrels of water per barrel of oil 

equivalent in the San Juan Basin (Colorado 

and New Mexico) to approximately 900 barrels of water per barrel of oil equivalent in 

the Powder River Basin (Wyoming and 

Montana) (Rice et al., 2000). Additionally, 

produced water rates for coal-bed natural 

gas wells are not consistent over the life of 

the wells. Water production rates are high 

initially but decline rapidly. 

ENERGY IMPACTS ON WATER 

QUALITY 

As noted in Table II-1, many of the elements 

associated with energy development have 

the potential to impact water quality negatively. Oil and gas production that is not 

adequately managed and monitored can 

contaminate surface water and shallow 

groundwater through drilling and production 

operations or from spills of produced hydrocarbons or produced brackish water. The 

refining and processing of oil and gas can 

generate by-products and wastewater 

streams that, if not handled appropriately, 

can cause water contamination. Fuel 

additives, such as methyl tertiary-butyl ether 

(MTBE), that have been used to reduce air 

emissions have also emerged as potential 

groundwater contaminants. 
22

Produced Water Forecast (MMbbls) by Resource Type

Lower 48 States Onshore

0

5000

10000

15000

20000

25000

2004 2008 2012 2016 2020 2024

Wp Total

Wp Conventional Oil

Wp Conventional Gas

Wp Unconv Gas (e.g. Coal Bed Methane)

Figure II-6. Forecast for Produced Water (Wp) from Oil and Gas Extraction 

(Feeley et al., 2005) 
23

 

Energy resource mining and processing, 

such as coal and uranium mining and oil 

shale development, can contaminate surface 

and groundwater. Runoff from both main 

mine operations and tailings piles can significantly reduce pH levels and increase 

heavy metals concentrations in mine drainage water. In addition, runoff from oil shale 

residue can wash into surface waters and byproducts from in situ retort methods could 

impact groundwater quality. An increased 

interest in U.S. uranium supplies has led 

some older mines in New Mexico and Utah 

to considering reopening. By doing so, 

these mines might generate from 3 to 5 million gallons of water a day that would need 

to be handled and disposed of (Hopp, 2005). 

On occasion, water is spilled from mining 

operations; 300 million gallons of coal 

sludge spilled in an incident in Kentucky in 

October 2000 (Clean Air Task Force, 

2004a). Water from some abandoned mines, 

including some in Pennsylvania, must be 

pumped and treated to prevent contamination of surface waters (USGS, 2002a). 

Energy transportation and storage development can also impact surface water and 

groundwater quality. Water used for pipeline testing, coal slurry pipelines, and solution mining for oil and gas storage caverns 

creates a range of contaminants that can 

contaminate fresh or coastal water sources if 

not adequately managed and disposed of. 

Finally, thermoelectric and hydroelectric 

power generation can impact water quality. 

Discharge from open-loop cooling systems 

can affect water temperature and oxygen 

levels. Air emissions from fuel combustion, 

such as mercury, sulfur, and nitrogen oxides, 

can lead to negative impacts on downwind 

water quality and aquatic ecosystems. 

Hydroelectric plants can impact water 

quality and river ecology in several ways. 

Operations can change water temperatures 

and dissolved oxygen and nitrogen levels in 

downstream waters. Operations can also 

change the natural flow characteristics of 

rivers so as to impact aquatic ecology. 
24
25

Chapter III. Supplying Water Requires Energy 

Satisfying the Nation’s water needs requires 

energy for supply, purification, distribution, 

and treatment of water and wastewater. 

Nationwide, about 4 percent of U.S. power 

generation is used for water supply and 

treatment, which, as shown in Figure III-1, 

is comparable to several other industrial 

sectors (EPRI, 2002b). Electricity 

represents approximately 75 percent of the 

cost of municipal water processing and 

distribution (Powicki, 2002). 

A recent study funded by the Electric Power 

Research Institute (EPRI) looked at energy 

requirements for water supply and treatment 

across the country. The results are examined in terms of per capita use of energy for 

water supply and treatment in Figure III-2. 

The biggest difference among regions is the 

amount of energy used to supply water for 

agriculture. In general, per capita non-agricultural use of energy for water is similar 

region to region. 

However, within regions, there can be substantial variation in energy requirements for 

water supply and treatment, depending upon 

the source, the distance water is conveyed, 

and the local topography. California is an 

0

1

2

3

4

5

6

7

Water/Wastewater Paper & Pulp Chemicals Petroleum Refining

% of US Electricty Consumption

Figure III-1. Percent of U.S. Electricity 

Consumption by Sector 

(EPRI, 2002b; EIA, 1998) 

interesting case study in electrical consumption and illustrates the cost of long-distance 

water conveyance. California uses about 

5 percent of its electricity consumption for 

water supply and treatment (CEC, 2005). 

This is substantially above the national 

average. As shown in Table III-1, a study 

by the California Energy Commission 

(CEC) illustrates how energy use can vary 

among water systems. 

SUPPLY AND CONVEYANCE 

Supply and conveyance can be the most energy-intensive portion of the water delivery 

chain. If the water source is groundwater, 

pumping requirements for supply of freshwater from aquifers vary with depth: 

540 kWh per million gallons from a depth of 

120 feet, 2000 kWh per million gallons from 

400 feet (Cohen et al., 2004). These energy 

needs will increase in areas where groundwater levels are declining. 

Table III-1. Energy Requirements for 

Water Supply and Treatment in 

California (CEC, 2005) 

kWh/Million 

gallons 

Water Cycle Segments Low High 

Supply and Conveyance 0 16,000 

Treatment 100 1,500 

Distribution 700 1,200 

Wastewater Collection 

and Treatment 1,100 4,600 

Wastewater Discharge 0 400 

TOTAL 1,900 23,700 

 

Recycled Water 

Treatment and 

Distribution for Nonpotable Uses 400 1,200 
26

2000

0 200 400 600 800 1000

Pacific

Mountain

West South

Central

West North

Central

East South

Central

East North

Central

Middle Atlantic

South Atlantic

New England

kWh/yr

Public Water Supply

Domestic Supply

Commercial Supply

Industrial Supply

Mining Supply

Public WW Treatment

Private WW Treatment

Livestock

Irrigation

2050

0 200 400 600 800 1000

Pacific

Mountain

West South

Central

West North

Central

East South

Central

East North

Central

Middle Atlantic

South Atlantic

New England

kWh/yr

Public Water Supply

Domestic Supply

Commercial Supply

Industrial Supply

Mining Supply

Public WW Treatment

Private WW Treatment

Livestock

Irrigation

Figure III-2. Per Capita Energy Use for Water Supply and Wastewater Treatment in 2000 

and Projected for 2050 (EPRI, 2002b). 

Energy requirements to pump water from 

surface waters can be negligible if users are 

located close to the source. But if water 

must be pumped long distances, then the energy requirement is much higher. In California, water is conveyed from Northern 

California up to 400 miles via the State 

Water Project to the cities of Southern California. Energy requirements for long-distance conveyance are indicated by the upper 

range in Table III-1. The table also illustrates that energy savings can be realized 

when wastewater streams are made available 

for reuse, rather than having to pump and 

convey freshwater over long distances. 

TREATMENT AND DISTRIBUTION 

Groundwater, if not brackish, can require 

minimal energy for purification. Surface 

waters generally require more treatment, and 

energy requirements for surface water 

treatment are at the upper end of the range in 

Table III-1. Energy requirements for distribution and collection vary depending on 

system size, topography, and age. Older 

systems often require more energy because 

of older infrastructure and less efficient 

equipment. 

END USE OF WATER 

One of the more interesting results that the 

California study noted is that energy consumption associated with using water is 

greater than the energy consumption for 

supply and treatment. Activities such as 

water heating, clothes washing, and clothes 

drying require 14 percent of California’s 

electricity consumption and 31 percent of its 

natural gas consumption. Most of that use is 

in the residential sector. These data 

Total U.S. 

Energy for 

Water 

Demand:

123 Million 

Mwh/yr
27

illustrate that both water and energy can be 

conserved through the use of appliances and 

fixtures that reduce hot water use. 

FUTURE ENERGY DEMAND FOR 

WATER SUPPLY AND TREATMENT 

Population growth will create an increased 

demand for water. As freshwater supplies 

become more limited, pumping water from 

greater distances or greater depths and 

treating water to access alternative sources 

will increase energy consumption to meet 

future water demands. Additionally, 

emerging water treatment requirements 

(e.g., standards for arsenic removal) are 

becoming more stringent, which will 

increase energy consumption for both 

purification and wastewater treatment. In 

agriculture, gravity-driven flood irrigation 

may be replaced with more water-efficient 

but more energy-intensive spray irrigation 

and micro-irrigation. 

An increased demand for water and water 

treatment could provide incentives to 

improve the efficiency of the water 

infrastructure. Aging supply, treatment, and 

distribution equipment may be replaced by 

newer, more energy-efficient equipment, 

and water conservation measures, 

including improved irrigation practices, 

could reduce water use. 

The EPRI study estimated future energy 

demands for water supply and treatment in 

2050. The results are presented on a per 

capita basis in Figure III-2. Compared to 

2000, per capita energy requirements are 

expected to be largely unchanged, except in 

the industrial and agricultural sectors. 

Energy for public and commercial water 

supply and treatment are expected to grow 

with population, with an average increase 

for the Nation of almost 50 percent between 

2000 and 2050. According to the EPRI 

study, energy use for water supply and 

treatment in the industrial sector is expected 

to triple because of growth projected in 

industrial activity, with strong growth in per 

capita use in the East North Central region. 

The study also projects that energy use for 

irrigation will triple based on projections of 

land use, with strong growth in per capita 

use in the South Central, West North 

Central, and West South Central regions. 

The study cites EPRI projections on 

industrial activity and U.S. Department of 

Agriculture (USDA) projections on land use 

(EPRI, 2002b). 
28
29

Chapter IV. Water Shortages and Impacts on Energy Infrastructure 

Today’s U.S. energy infrastructure depends 

heavily on the availability of water, and 

there is likely to be increased issues concerning availability and value of that water 

due to growth in competing demands. Most 

state water managers expect shortages of 

water over the next decade, as shown in 

Figure IV-1 (GAO, 2003), and water supply 

issues are already affecting many existing 

and proposed power projects as shown in 

Figure IV-2. In some regions, power plants 

have had to limit generation because of 

insufficient water supplies, and citizens and 

public officials concerned about the 

availability of water have opposed new 

high-water-use energy facilities, suggesting 

clear incentives for using lower water 

intensity designs in future energy 

infrastructure developments. 

As illustrated in Figure IV-3, total U.S. 

water withdrawals peaked in 1980 and have 

been essentially level since then. Construction of large reservoirs peaked in the 1970s, 

and only one large water storage project is 

currently under construction—the Animas 

LaPlata project in Colorado and New Mexico (GAO, 2003). In 1980, major reservoirs 

were full. However, since then, droughts 

have caused some reservoir levels to 

decline, particularly in the West, and water 

managers have had to limit water withdrawals. Also, groundwater levels have declined 

substantially in many areas of the country. 

Compounding the uncertainty regarding 

supply is the lack of current data on water 

consumption. Steady or declining rates of 

water withdrawal do not necessarily imply 

steady or declining consumption. For 

example, communities have responded to 

water shortages, in part, by increasing water 

re-use for such nonpotable uses as irrigation. 

Diverting wastewater effluent from return 

flows to consumptive uses reduces the need 

for water withdrawal, but does not reduce 

the rate of water consumption. 

TX

CA

MT

AZ

ID

NV

NM

CO

IL

OR

UT

KS

WY

IA NE

SD

MN

ND

OK

FL

WI

MO

AL

WA

GA

AR

LA

MI

IN

PA

NY

NC

MS

TN

KY

VA

OH

SC

ME

WV

MI VTNH

MD

NJ

MA

CT

DE

RI

g

AK

AK

HI

HI

HI

HI

HI

shortage

Statewide

Regional

Local

None

No response or uncertain

Figure IV-1. Survey of Likely Water Shortages over the Next Decade under Average 

Conditions (GAO, 2003) 
30

Figure IV-2. Examples of Energy-Water Conflicts 

1. As a result of a 1999 drought, water-dependent industries along the Susquehanna reported difficulty getting 

sufficient water supplies to meet operational needs (GAO, 2003). 

2. Browns Ferry Nuclear Power Plant, part of the TVA complex on the Tennessee River, often experiences warm 

river flows, such that the temperature of the water at the plant’s cooling intakes often approaches or exceeds the 

Alabama water quality criterion of 86 °F, nearly the plant’s discharge limit of 90 °F (Curlee and Sale, 2003; 

Gibson, 2006). 

3. Low water on the Missouri River leads to high pumping energy, blocked screens, lower efficiency, load 

reduction, or shutdown at power plants (Kruse and Womack, 2004). 

4. Tennessee Governor imposed a moratorium in 2002 on the installation of new merchant power plants because 

of cooling constraints (Curlee and Sale, 2003). 

5. Georgia Power lost a bid to draw water from the Chattahoochee River for power plant cooling (Hoffman, 2004). 

6. Arizona rejected permitting for a proposed power plant because of potential impact on a local aquifer (Tucson 

Citizen, 2002). 

7. A New York Entergy plant was required to install a closed-cycle cooling water system to prevent fish deaths 

resulting from operation of its once-through cooling water system (Clean Air Task Force, 2004a). 

8. Southern States Energy Board member states cited water availability as a key factor in the permitting process 

for new merchant power plants (Feldman and Routhe, 2003). 

9. South Dakota Governor called for a summit to discuss drought-induced low flows on the Missouri River and the 

impacts on irrigation, drinking-water systems, and power plants (U.S. Water News Online, 2003). 

10. Washoe County, Nevada, residents expressed opposition to a proposed coal-fired power plant’s planned water 

use (Reno-Gazette Journal, 2005). 

11. Proposed coal-fired power plant on Lake Michigan (Wisconsin shore) strongly opposed by environmental 

groups because of potential effects of the facility’s cooling-water-intake structures on the lake’s aquatic life 

(Milwaukee Journal Sentinel, 2005). 

12. Hot discharge water from the Brayton Point coal plant on the Massachusetts/Rhode Island border cited by EPA 

as contributing to an 87 percent reduction in fin fish in Mt. Hope Bay; EPA mandates a 94 percent reduction in 

water withdrawal, replacing seawater cooling with freshwater cooling towers (Clean Air Task Force, 2004b). 

13. University of Texas researchers said power plants would have to curtail production if 20th century drought 

conditions recurred (Clean Air Task Force, 2004a). 

14. Idaho opposed two proposed power plants because of impact on aquifer (U.S. Water News Online, 2002). 

11

1

2

3

4

5

6 

7 

8

9

10 

12 

13

14 
31

0

50

100

150

200

250

300

350

400

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

Withdrawals (billion gallons per day)

Total Freshwater

Surface Water

Ground Water

Figure IV-3. Trends in Total Freshwater Withdrawals, 1950–2000 (Hutson et al., 2000) 

While the USGS reported water withdrawal 

data in 2000, USGS last reported data for 

consumption in 1995, and the last detailed 

study was done in 1978 (U.S. Water 

Resources Council, 1978). As the GAO 

reported to Congress in 2003 (GAO, 2003): 

National water availability and use has 

not been comprehensively assessed in 

25 years, but current trends indicate that 

demands on the Nation’s supplies are 

growing. In particular, the Nation’s 

capacity for storing surface-water is 

limited and groundwater is being 

depleted. At the same time, growing 

population and pressures to keep water 

in streams for fisheries and the 

environment places new demands on the 

freshwater supply. The potential effects 

of climate change also create uncertainty 

about future water availability and use. 

WATER MANAGEMENT 

CHALLENGES 

Managing water resources requires balancing the competing needs for water with the 

availability of supplies and storage capacity. 

Reservoirs store water to mitigate the effects 

of seasonal and annual variations in supply. 

Water resources are managed to meet the 

needs of a range of uses, including irrigation, recreation, hydroelectric power, 

downstream communities, industry, thermoelectric plants, and in-stream uses, such 

as navigation, fisheries, and wildlife habitat. 

The Tennessee River system provides an 

example of the challenges of managing a 

watershed to meet competing needs. 

Tennessee Valley Authority (TVA) operates 

the Tennessee River system to provide a 

wide range of public benefits: navigation, 

flood damage reduction, affordable 

electricity, water quality, water supply, 

recreation, and economic growth. Each of 

these benefit areas is supported by different 

stakeholders, who typically want the system 

managed to serve their interests first. 

TVA conducted a Reservoir Operations 

Study to determine whether changes in river 

system operation would produce greater 

overall public value. The resulting new 

operational strategy improves recreation, 

commercial navigation, and aquatic habitat 

with a total economic benefit of $11.5 

million ($9 million in revenues from 

recreation and shipper savings of 

approximately $2.5 million), which will be 

largely offset by the increase in power costs 

of approximately $14 million annually 

(TVA, 2004; Gibson, 2006). 
 32

SURFACE WATER CONCERNS 

Climate change and climate variability can 

have a dramatic impact on water supplies, 

with the most obvious impact being drought. 

But even high precipitation provides no 

guarantee of adequate water if the inflow 

from precipitation does not come at the right 

time. For example, snow pack provides 

75 percent of the water supply in the West 

(USDA, 2004b), and snow pack is a key part 

of water storage in some areas. While 

reservoirs on the middle and lower Colorado 

River basin can store several times the 

annual river flow, reservoirs on the 

Columbia River can store only about 30 

percent of annual flow. When warm 

temperatures cause rain instead of snow or 

snow melts earlier, Columbia River 

reservoirs do not have the capacity needed 

to store the early inflow. Water then has to 

be released early and is not available later 

for the reservoir’s customers. In the past 50 

years, peak stream flow has occurred earlier, 

typically by 10 to 40 days, and spring snow 

pack has decreased by 11 percent (Mote, 

2004). 

Long-term cyclical changes in precipitation 

patterns and the effect on flows in rivers and 

the operation of reservoirs and hydroelectric 

plants are a major concern to the energy industry. The 2001 drought in the Northwest 

significantly reduced hydroelectric power 

production, leading to the loss of thousands 

of jobs in the energy-intensive aluminum 

industry (Washington State Hazard Mitigation Plan, 2004). Such loss of hydroelectric 

power affects not only total power generation, but also power reliability. Because the 

level of output from hydropower can be 

quickly changed, it is used to provide peaking power when demand is highest. Peaking 

capability is especially valuable in the 

summer, when high temperatures and high 

humidity can reduce generation efficiency 

from thermoelectric plants. In the absence 

of hydroelectric power, peaking needs are 

being met in most cases by natural gas. 

As illustrated in Figure IV-2, for those who 

build and operate power plants across the 

Nation, the consequences of limited water 

availability are already clear: there is a significant incentive to decrease the water 

intensity of energy infrastructure in a costeffective manner. Power plants that use 

open-loop cooling require plentiful supplies 

of water and may no longer be the economic 

design option. Limited availability, poor 

quality, and invasive species such as zebra 

mussels in rivers and lakes can restrict 

cooling and power generation by fouling 

intake structures, which has driven 

advancement of science to control zebra 

mussels. When warm weather or low flow 

leads to high water temperatures at the plant 

inlet, then plants may have to reduce 

generation to avoid exceeding discharge 

temperature limits specified in plant 

operating permits. In a few cases, low 

flows, other environmental concerns, and 

increasing value of water are providing 

incentives for the replacement or upgrade of 

open-loop cooling systems with new cooling 

systems to achieve water-efficient and 

economical generation of power. 

Low surface water levels can also affect 

thermoelectric plants using closed-loop 

cooling systems. Generally, these plants 

secure long-term access to water, if necessary, before installation. However, if 

surface waters are severely constrained by 

drought, plant water supplies could be 

impacted, especially if priority rights or 

water sharing are imposed. 

GROUNDWATER CONCERNS 

Almost 40 percent of water provided by 

private water suppliers is from groundwater 

sources, serving 90 million people in all 50 

states; another 40 million are self-supplied 
 33

with groundwater (Solley et al., 1998). 

Some aquifers are adjacent to surface 

waters. When these aquifers are drained, 

levels of adjacent surface waters decline, 

and some riverbeds dry out. Other aquifers 

are isolated from surface waters. Recharge 

of these aquifers can be very slow, and the 

water that is being pumped may have taken 

decades, centuries, or even longer to 

accumulate. Visible impact of over-withdrawal occurs in some areas as the land 

surface sinks when the underlying water is 

removed. Table IV-1 highlights dramatic 

evidence of groundwater depletion around 

the country. 

Energy facilities dependent on groundwater 

supplies may have secured exclusive longterm withdrawal permits or may be drawing 

water from aquifers with multiple users. In 

either case, if the rate of withdrawal exceeds 

the rate of recharge, then over time, water 

must be pumped from ever greater depths. 

Ultimately, there is a risk that freshwater 

from the aquifer will become fully depleted, 

leading to loss of water supplies. 

As aquifers are drawn down, they often 

yield brackish waters; these require 

treatment before use in a closed-loop 

cooling system. The increased energy 

requirements for water pumping and 

treatment will decrease net plant output and 

could increase the cost of power. 

POTENTIAL IMPACT OF FUTURE 

POWER GENERATION ON WATER 

SUPPLIES 

Figure IV-4 shows the expected increases in 

power generating capacity from 1995 to 

2025, as projected by the AEO2004 

reference case (EIA, 2004c). (EIA’s 

reference case is based on business-as-usual 

trend forecasts, given known current 

technology, techno-logical and demographic 

trends, and current laws and regulations.) 

The regions where capacity growth is 

expected are regions with high population 

growths, as shown in Chapter I, Figure I-2. 

Many of these areas are already facing water 

supply limitations, and efforts to build new 

power plants in these areas are encountering 

resistance from the public and from 

government officials because of concerns 

Table IV-1. Examples of Declining 

Groundwater Levels (Bartolino and 

Cunningham, 2003) 

Region Groundwater Decline 

Long Island, NY Water table declined, 

stream flows reduced, 

salt water moving 

inland 

West-central 

Florida 

Groundwater and 

surface water declining, 

salt water intruding, 

sink holes forming 

Baton Rouge, 

LA 

Groundwater declining 

up to 200 feet 

Houston, TX Groundwater declining 

up to 400 feet, land 

subsidence up to 10 feet 

Arkansas Sparta aquifer declared 

“critical” 

High Plains Declines up to 100 feet, 

water supply (saturated 

thickness) reduced over 

half in some areas 

ChicagoMilwaukee area Groundwater serving 

8.2 million people has 

declined as much as 900 

feet, declining 17 feet/yr 

Pacific 

Northwest 

Declines up to 100 feet 

Tucson/Phoenix, 

AZ 

Declines of 300 to 500 

feet, subsidence up to 

12.5 feet 

Las Vegas, NV Declines up to 300 feet, 

subsidence up to 6 feet 

Antelope Valley, 

CA 

Declines over 300 feet, 

subsidence over 6 feet 
 34

that proposed plant designs are too waterintensive, and should be changed to less 

water-intensive designs, as highlighted in 

Figure IV-2. 

The impact of power generation on future 

water demand depends on the type of 

generation installed and the rate at which 

existing plants are retired. Under a 

business-as-usual case, where most new 

power is provided by water-cooled 

thermoelectric power plants, the most 

dramatic changes will occur if old plants 

using seawater or freshwater open-loop 

plants are retired, and replacement plants as 

well as capacity additions are installed with 

evaporative closed-loop cooling. Water 

withdrawal requirements for evaporative 

closed-loop cooling are only 1 to 2 percent 

of the requirements for open-loop cooling, 

but evaporative closed-loop cooling systems 

can consume up to twice as much water as 

open-loop cooling systems (details are given 

in Table V-1). Alternatives to freshwater 

closed-loop cooling, including dry cooling, 

are discussed in Chapter V. 

The potential impacts of various power-generation scenarios on water withdrawal and 

consumption are illustrated by a study 

of thermoelectric power plant retirements 

and additions conducted by the National 

Energy Technology Laboratory (Hoffmann 

et al., 2004). This study looked at power 

plant retirements and additions, based on the 

Energy Information Administration (EIA) 

reference case. The results presented here 

were revised to incorporate the reference 

case from the 2006 Annual Energy Outlook 

(EIA, 2006), as shown in Figure IV-5. 

Figure IV-4. Comparison of Regional Thermoelectric Generation Capacity by North 

American Electric Reliability Council Region, 1995–2025 (Hoffmann et al., 2004) 
 35

The results show the range of water withdrawal and consumption possible, depending upon which plants are retired (e.g., seawater or freshwater cooled) and whether 

open-loop cooling systems were reused in 

new plants or replaced with closed-loop 

cooling systems. As shown in Figure IV-6, 

not much change in water withdrawal rates 

is expected. Withdrawal requirements could 

increase slightly as additional plants are 

installed or could decline somewhat if plants 

using freshwater open-loop cooling are 

replaced by plants using other cooling 

systems. However, as shown in Figure IV7, freshwater consumption by the powergeneration sector could more than double if 

evaporative closed-loop cooling is used for 

new and replacement generation capacity 

(the high-consumption case). Only in the 

case that capacity additions are installed in 

coastal areas and use seawater for open-loop 

cooling would consumption remain flat (the 

low-consumption case). The water required 

in the high-consumption case is equivalent 

to the daily domestic water consumption of 

about 50 million people. This would have a 

significant impact on the availability and 

value of water given competing uses, 

including agricultural and nonagricultural 

water consumption. 

0

100

200

300

400

500

600

700

800

1995 2000 2005 2010 2015 2020 2025 2030

Year

Generating Capacity, GW

Nuclear Power

Steam Component of Combined Cycle

Other Fossil Steam

Coal Steam

Figure IV-5. Projected Steam-Electric Generation Capacity by Type Projected from EIA 

Reference Case (EIA, 2006) 
 36

0.0

20.0

40.0

60.0

80.0

100.0

120.0

140.0

1995 2000 2005 2010 2015 2020 2025 2030

Year

Daily Withdrawals, Billion Gallons / Day

0

100

200

300

400

500

600

700

800

Thermoelectric Generating Capacity, GW

High Withdrawal Case

Low Withdrawal Case

USGS 2000 Baseline

Thermoelectric Generating Capacity

Figure IV-6. Range of Projected Daily Freshwater Withdrawal for Thermoelectric Power 

Generation (revised from Hoffmann et al., 2004) 

. 

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

1995 2000 2005 2010 2015 2020 2025 2030

Year

Daily Freshwater Consumption, Billion Gallons / Day 

High Consumption Case

Low Consumption Case

USGS 1995 Baseline

Figure IV-7. Range of Projected Freshwater Consumption for Thermoelectric Power 

Generation (revised from Hoffmann et al., 2004) 
37

Chapter V. Opportunities to Secure America’s Energy and Water Future 

ADDRESSING FUTURE WATER 

NEEDS IN THE POWER SECTOR 

There are a number of technologies in 

various stages of development with the 

potential to reduce the use of water per unit 

energy (the water intensity) for power 

generation. These technologies will be 

deployed when they are economical, based 

on changes in water value and availability. 

Potential options for meeting future energy 

production and generation needs with 

reduced water use intensity are identified 

below. 

Table V-1 and Figures V-1 and V-2 show 

water use for a range of electric-generating 

technologies, including water use for fuel 

extraction and processing. Data supporting 

the table are found in Appendix A for 

energy extraction and in Appendix B for 

power generation. (Not included in the 

figures is the water required to manufacture 

and construct energy facilities, such as the 

water used in manufacturing the components 

of, or to construct, a power plant.) 

Advanced Cooling for Thermoelectric 

Power Plants 

Opportunity: Reduces water use. 

Gap: Cost, complexity, hot weather 

performance, scalability to large power plants 

The amount of water used to condense 

steam from steam-driven turbine generators 

(per unit electricity output) depends on the 

type of cooling system and the efficiency of 

the turbine. Turbine efficiency increases as 

the difference between the steam temperature and the condensing temperature 

increases. Plants with higher efficiencies 

require less cooling per unit energy 

produced. Coal plants operate at higher 

temperatures than today’s nuclear plants, as 

shown in Table V-1, so coal plants require 

less water than today’s nuclear plants. Some 

renewable power plants also use steam 

turbines with closed-loop cooling. These 

include solar thermal troughs, solar power 

towers, and geothermal steam plants. 

Dry Cooling – One approach to reduce 

water use in thermoelectric plants is to 

replace the evaporative cooling towers in 

closed-loop systems (Figure II-3) with dry 

cooling towers cooled only by air, but there 

is an impact on plant efficiency. 

Evaporative closed-loop cooling provides 

cooling that approaches the dew point temperature. Dry cooling can approach only the 

ambient air temperature. Unless the relative 

humidity is 100 percent, the air temperature 

is always higher than the dew point, so the 

outlet temperature of a dry-cooling system 

will almost always be higher than for an 

evaporative system. As the cooling system 

outlet temperature increases, plant efficiency 

decreases. In other words, plant efficiency 

is higher for plants using evaporative 

cooling than for plants using dry cooling, 

especially in a hot, arid climate. 

Over the course of a year, the output of a 

plant with dry cooling will be about 2 

percent less than that of a similar plant with 

evaporative closed-loop cooling, depending 

on the local climate. However, in the hottest 

weather, when power demands are highest, 

plant efficiency may decrease by up to 25 

percent (USDOE, 2002a). Decreased plant 

efficiency means increased fuel use and 

increased emissions. This could provide 

greater incentives for other efficiency and 

emission control technology improvements. 

In addition, dry cooling systems must be 

larger than comparable evaporative closedloop systems, and that increases the cost for 
38

Table V-1. Water Intensity for Various Power Generation Technologies 

(EPRI, 2002a; CEC, 2002; CEC, 2006; Grande, 2005; Leitner, 2002; Cohen et al., 1999) 

See Appendix A for Fuel References

 Water intensity (gal/MWhe) 

 Plant-type Process Steam Condensing Other Use 

Steam Withdrawal Consumption Withdrawal Consumption 

Mining 5–74 Coal 

Slurry 110–230 30–70 

OL Cooling 20,000–

50,000 ~300 

CL Tower 300–600 300–480 

CL Pond 500–600 ~480 

Fossil/ 

biomass/ 

waste 

Dry 0 0 

~30** 

Nuclear Mining and 

Processing 45–150 

Nuclear OL Cooling 25,000–

60,000 ~400 

Nuclear CL Tower 500–1,100 400–720 

Nuclear CL Pond 800–1,100 ~720 

Nuclear Dry 0 0 

~30**

Geothermal 

Steam CL Tower ~2000 ~1400 Not available 

Solar trough CL Tower 760–920 760–920 8** 

Solar tower CL Tower ~750 ~750 8** 

Other 

Natural Gas Supply ~11 

OL Cooling 

7,500–

20,000 100 

CL Tower ~230 ~180 

Natural Gas 

CC 

Dry 0 0 

7–10** 

Coal IGCC* CL Tower ~250 ~200 7–10 + 130 (process water)** 

Hydroelectric Evaporation 4500 (ave) 

OL = Open loop cooling, CL = Closed Loop Cooling, CC = Combined Cycle 

*IGCC = Integrated Gasification Combined-Cycle, includes gasification process water 

Other Use includes water for other cooling loads such as gas turbines, equipment washing, 

emission treatment, restrooms, etc. 

**References did not specify whether values are for withdrawal or consumption. 

Thermoelectric 

 power 

generation 

withdraws 

136 billion 

gallons 

per day 

and 

consumes 

3.3 billion 

gallons 

per day

Mining of 

coal 

consumes 

0.07 to 0.26 

billion 

gallons 

per day 
39

1 10 100 1000 10000 100000

Coal Mining

Coal Slurry

Fossil Steam, Open Loop

Fossil Steam, CL Tower

Fossil Steam, CL Pond

Fossil Steam, Dry

Coal ICGT

Nuclear Fuel Mining and Processing

Nuclear, Open Loop

Nuclear, CL Tower

Nuclear, CL Pond

Nuclear, Dry

Natural Gas Supply

Gas CCGT, Open Loop

Gas CCGT, CL Tower

Gas CCGT, Dry

Solar Tower, CL Tower

Solar Trough, CL Tower

Geothermal Steam, CL Tower

Gallons/MWhe

Figure V-1. Water Withdrawal for Power Generation 

1 10 100 1000 10000 100000

Coal Mining

Coal Slurry

Fossil Steam, Open Loop

Fossil Steam, CL Tower

Fossil Steam, CL Pond

Fossil Steam, Dry

Coal ICGT

Nuclear Fuel Mining and Processing

Nuclear, Open Loop

Nuclear, CL Tower

Nuclear, CL Pond

Nuclear, Dry

Natural Gas Supply

Gas CCGT, Open Loop

Gas CCGT, CL Tower

Gas CCGT, Dry

Solar Tower, CL Tower

Solar Trough, CL Tower

Geothermal Steam, CL Tower

Gallons/MWhe

Figure V-2. Water Consumption for Power Generation 
40

construction, installation, operation 

maintenance, and land. The result is that, as 

the value of water increases, there is 

increased need and value for technologies 

that reduce water and energy use, especially 

to meet peak demand on hot days, when drycooled systems lose efficiency. 

In total, dry-cooled systems impose a cost 

penalty ranging from 2 to 5 percent (Maulbetsch, 2006a) to 6 to 16 percent (CEC, 

2002) for the cost of energy compared to 

evaporative closed-loop cooling. These 

ranges reflect the fact that the cost penalty is 

highly dependent on the value placed on the 

energy that is not generated and must be replaced when the weather is hot and demand 

is high. Dry cooling is best suited to wet, 

cool climates (not the dry, arid climates of 

the West where water is most scarce). As of 

2002, dry cooling had been installed on only 

a fraction of 1 percent of U.S. generating 

capacity, mostly on smaller plants (CEC, 

2002). 

Hybrid Cooling – Hybrid cooling systems 

combine dry cooling and wet cooling to reduce water use relative to wet systems while 

improving hot-weather performance relative 

to dry systems. Hybrid cooling has also 

been used for plume abatement, reducing the 

vapor exhaust to avoid potential foggy or icy 

conditions on nearby roadways, but these 

systems do not emphasize water conservation. Most hybrid systems have been 

installed for plume abatement, with a 

notable exception located at the Public 

Service Company of New Mexico (PNM) 

San Juan Generating Station (see sidebar) 

(CEC, 2002). 

One approach to hybrid cooling is spray 

cooling enhancement of air-cooled condensers (EPRI, 2003b). This approach is low 

cost but uses a significant amount of water 

during operation and could lead to scaling or 

corrosion of the condenser. Thus, it is best 

suited for applications where enhanced 

cooling is needed only on the order of one 

hundred hours per year (Maulbetsch, 

2006b). 

An alternative approach useful when extended operation is needed (e.g., a thousand 

hours per year) is a parallel wet/dry system, 

which uses a dry tower and a conventional 

evaporative cooling tower to augment cooling in the hottest weather. These have been 

applied successfully to small power plants, 

but Micheletti and Burns caution that 

application of this approach to large (400 

MW) plants might be difficult to control 

(Micheletti and Burns, 2002). 

The Public Service Company of New 

Mexico operates a hybrid cooling tower 

at its coal-fired San Juan Generating 

Station. PNM reports that “Unit 3 at San 

Juan has a ‘hybrid’ cooling tower—one 

that can run in both wet and dry modes. 

Unfortunately, this unit has not 

performed as well as the wet cooling 

tower units. Engineering estimates 

indicate that converting the plant to dry 

cooling could add at least 10 percent to 

the cost of electricity production because 

of lower energy efficiency and increased 

construction and maintenance costs. Because of the ‘energy penalty’ thus imposed, the amount of emissions per 

megawatt produced will also increase 

with the use of dry cooling.” 

http://www.pnm.com/environment/sj_water.htm
41

Combined-Cycle Gas Turbines 

Opportunity: Reduce water use by half. 

Gap: High cost of fuel and increasing 

dependence on imports (gas). Technology 

validation (coal). 

Natural-gas-fired combined-cycle gas 

turbines use (withdraw and consume) about 

half as much water as coal-fired plants and 

have been deployed in large numbers in 

recent years. The gas turbines in these 

plants provide two-thirds of their power 

generation. The hot exhaust from the gas 

turbine is used to generate steam, which 

drives a steam turbine to provide the 

remaining generation. Water use is reduced 

because only the steam turbine requires 

condensate cooling. In recent years, simplecycle and combined-cycle natural gas 

turbine plants have provided much of the 

new generating capacity installed in the U.S. 

But as natural gas prices have increased, the 

EIA forecasts fewer installations of these 

plants and increased installations and 

upgrades of conventional thermoelectric 

plants (EIA, 2000; EIA, 2006). 

Integrated Gasification Combined-Cycle 

power plants are being developed that 

combine coal gasification with a combinedcycle gas turbine. As with the natural-gas 

combined-cycle plants, water use is lower 

than for conventional thermoelectric plants, 

although, as shown in Table V-1, some 

water is consumed in converting coal to 

syngas (Feeley, 2005). 

Renewable Electric Power 

Opportunity: Reduce water use, provide peak 

power needs, carbon-free. 

Gap: Cost, manufacturing/deployment capacity. 

For some technologies, intermittency/need for 

storage at high penetration. 

Some renewable energy technologies 

consume no freshwater during operation, so 

they are not included in Figures V-1 and 

V-2. These technologies include 

• Wind 

• Solar photovoltaics 

• Solar dish-engine 

• Geothermal hot water (binary) systems 

that are air cooled 

• Run-of-river hydroelectric 

• Ocean energy systems 

In addition, existing reservoirs that do not 

currently have hydroelectric capacity are 

candidates for power generation. To reduce 

impacts on the aquatic environment, these 

plants could use fish-friendly turbines. 

Of these technologies, wind is currently 

being installed in the largest quantities, with 

more than 6300 MW of capacity installed in 

the United States (USDOE, 2005a). Solar 

photovoltaic systems installation is also 

expanding rapidly, with approximately 400 

MW installed through 2004 (Margolis, 

2006). Generation of electrical power by 

these low water use technologies can help 

offset power generation from more waterintensive technologies (Thresher, 2005; 

USDOE, 2006b; USDOE, 2006c). 
42

A common concern is that while geothermal, hydropower, solar thermal power with 

integrated storage, and biomass power can 

provide dispatchable power, other technologies, such as wind and solar photovoltaic, 

are intermittent and must be backed up by 

other generating systems. However, 

demand for electricity also fluctuates 

throughout the day. Connecting modest 

amounts of intermittent renewable sources 

to the grid has not been shown to undermine 

grid stability. On the contrary, both solar 

and wind have the potential to improve grid 

operation by providing power when it is 

most needed, during the hottest/windiest part 

of the day, as shown in Figure V-3 for solar 

generation. 

At some point, deployment of solar and 

wind technologies could increase the need 

for energy storage. In terms of technical 

capability, hydroelectric generation, including pumped storage, has the capacity to meet 

these potential needs. Grid support can also 

be provided with other peaking technologies 

or with other storage technologies.

Figure V-3. Peak Reduction from Combined Use of Solar Energy and Demand 

Management in a Residential Application (USDOE, 1999) 
43

ADDRESSING WATER NEEDS IN THE 

EMERGING FUEL SECTOR 

Much of the country’s current transportation 

fuels are derived from imported petroleum. 

An approach being considered to reduce 

dependence on foreign sources of energy is 

to increase the development and use of 

domestic energy sources, and most energy 

extraction and processing activities require 

water. The water use per-unit-energy for 

fuel extraction and processing is summarized in Figure V-4. Some options to address 

these challenges are discussed below. 

Oil Shale 

Opportunity: Large domestic resource. 

Gap: Cost, potential water demand, technology 

to mitigate environmental impacts. 

The U.S. is estimated to have two trillion 

barrels of oil in the form of oil shale deposits, which is more than triple the proven oil 

resources of Saudi Arabia. Due to historically high costs for development, oil shale is 

not currently widely produced in the U.S., 

but is increasingly being considered as a 

major future source of domestic oil supplies 

(USDOE, 2004b). 

Initial recovery work focused on mining and 

above-ground processing (retorting) that 

consumed 2 to 5 gallons of water per gallon 

of refinery-ready oil (Bartis, 2005). Providing 25 percent of U.S. oil demand would 

require 400 to 1000 million gallons of water 

per day. Because oil shale resources are 

predominantly located in areas where water 

availability is limited and has a high value, 

oil shale development may be constrained. 

In addition, runoff could wash salt from 

shale residue into surface waters. 

More recently, an electrically-driven underground process is being prototyped that does 

not directly use water. However, generation 

of the required electricity would consume 

about one-third of the energy produced 

(Bartis, 2005). If combined-cycle gas 

turbines with evaporative closed-loop 

cooling systems were used to produce the 

electricity, consumptive requirements would 

be approximately 250 million gallons of 

water per day. 

In either case, the energy consumed to 

produce fuel from oil shale will increase 

U.S. emission of carbon dioxide by up to 50 

percent per unit energy, unless carbon-free 

energy sources are used for mining and 

processing or unless a vigorous program of 

carbon sequestration is implemented. 

Renewable and Alternative Fuels 

Opportunity: Renewable, carbon-neutral 

domestic fuels and fuels from domestic coal and 

gas. 

Gap: Technology, cost. Water use for current 

biofuel production. 

As noted in Chapter II, biofuels currently 

provide about 3 percent of our transportation 

fuels. In the future, biofuels are being 

considered as a potential domestic source for 

producing significantly larger volumes of 

transportation fuel (USDOE, 2005d; Tyson 

et al., 2004; Perlack et al., 2005). 

Currently, the most water-intensive aspect of 

biofuel production is growing the feedstock. 

When that feedstock is corn or soy (used to 

make ethanol and biodiesel, respectively) 

and the feedstock is grown on irrigated land, 

the water consumption is quite high, as 

shown in Figure V-4. 
44

On the other hand, biofuel feedstock produced from crop residues in excess of those 

needed to maintain a healthy ecosystem, 

from feedstocks grown without irrigation, or 

from feedstocks grown with nontraditional 

water, will have minimal freshwater use 

intensity associated with production. This 

could provide significant volumes of bioenergy and biofuels in the future with low 

water use intensity (Perlak et al., 2005). In 

all cases, some water use is associated with 

processing, as shown in Figure V-4, but 

further technology development is likely to 

lower these values. 

Production of alternative fuels, such as synfuels from coal or hydrogen from methane, 

also requires water, at up to triple the requirements for water consumption in petroleum refining. Reforming hydrogen from 

methane is quite water intensive. Even 

production of hydrogen by electrolysis using 

a water-independent source of energy like 

wind requires water as feedstock to the 

electrolyzers. In summary, virtually every 

alternative will require as much water as 

refineries consume now, if not substantially 

more. To be able to increase domestic 

supplies of transportation fuels will require 

1 10 100 1000 10000 100000

Coal Mining

Coal Washing

Coal Liquefaction

Coal Slurry

Coal Gasification

Natural Gas Extraction & Processing

Natural Gas Pipeline Operations

Gas Storage in Salt Cavern**

Petroleum Extraction

Enhanced Oil Recovery

Refining

Oil Shale Surface Retort

Oil Shale In-Situ*

Oil Sands

Oil Storage in Salt Cavern**

Uranium Mining

Uranium Processing

Hydrogen Reforming

Hydrogen Electrolysis

Corn Irrigation

Ethanol Processing

Soy Irrigation

Biodiesel Refining

Gal/MMBTU

Figure V-4. Water Consumption Per-Unit-Energy and Current Water Use for Fuel 

Extraction and Processing 

See Appendix B for Data References

Petroleum 

Refining 

Consumes 

1-2 Billon 

Gallons 

per Day 
45

significant water resources using current 

approaches and options. 

ADDRESSING FUTURE U.S. WATER 

NEEDS 

Over the past century, the U.S. has had 

national programs to develop its vast water 

resources. Programs by the Bureau of 

Reclamation, the Army Corps of Engineers, 

and other federal and state agencies have 

enabled the U.S. to harness the vast surface 

water resources of the country’s river 

systems, control floods, store water for agricultural, industrial, and domestic uses, and 

generate hydroelectric power. In parallel, 

programs through agencies like the USGS 

have allowed states to exploit tremendous 

groundwater resources and monitor and 

manage surface water flows to achieve more 

efficient use of water. As noted in previous 

sections, the ability to easily expand 

freshwater availability may be limited. 

Some possible options to address the future 

needs are discussed below. 

Increasing and Stretching Water Supplies

Opportunity: Improve water supply understanding and utilization, stretch water supplies. 

Gap: Lack of water consumption data, water 

storage to address increased needs, climate 

variability, policy, coordination. 

The rate of water withdrawal grew as the 

economy grew through most of the last 

century but has leveled off and even 

declined in recent years. Changes in the rate 

of consumption are more difficult to assess. 

The last USGS report on water consumption 

was for 1995 (Solley et al., 1998), and the 

last detailed analysis was published in 1978 

(U.S. Water Resources Council, 1978). 

Meanwhile, there are many signs that 

consumption, if not growing, may still be 

outpacing available supplies: aquifers are 

declining, stored water levels are low, and 

communities are seeking to improve their 

access to water supplies, in part through 

desalination and re-use of water. However, 

best courses of action cannot be accurately 

determined without detailed water use and 

consumption data, which are lacking. 

Water Storage – Storage is an important 

part of any water infrastructure. Reservoirs 

capture runoff for release at a later time, 

making available freshwater that would 

otherwise have flowed downstream. Several 

factors have affected the availability and use 

of freshwater supplies: decreased water 

storage capacity because of reservoir 

sedimentation, requirements to limit water 

level fluctuations within the reservoir (for 

recreation or aesthetic reasons), or 

requirements to meet downstream flow 

targets for fish and wildlife needs. Another 

type of storage is the natural storage of 

moisture in snow pack. Recent climate 

trends suggest that snow packs are 

decreasing over time and annually are 

melting earlier (Mote, 2004). The decreased 

storage of water in snow packs will limit the 

reliable yield of river systems that derive 

much of their flow from the melting of snow 

pack. Thus, even without changes in the 

amount of man-made storage, reliable yields 

of some rivers are likely to decrease if these 

snow pack trends continue. 

Few surface-water storage projects have 

been built in recent years, and groundwater 

supplies in some parts of the Nation are in 

decline. There are promising means of 

increasing storage in order to increase 

reliable yields of water that involve the use 

of aquifers as part of the water management 

system (AwwaRF, 1996; AwwaRF, 2005a) . 

This includes “conjunctive use” (wherein 

groundwater and surface water are managed 

jointly, using surface water when it is abundant and groundwater during dry seasons 

and dry years). In addition, artificial 

recharge and aquifer storage and recovery 
46

are approaches that can increase reliable 

supplies by purposefully augmenting 

recharge with excess surface water (or 

treated effluent) in times when it is readily 

available, and then withdrawing that water 

in times of shortage. There are, however, 

significant energy implications of these 

technologies in terms of the energy that is 

required to treat and inject water and then to 

pump it out when the water is needed. In 

addition, there are efficiency questions with 

these technologies. Not all of the water 

injected can ever be withdrawn. Also, there 

are a variety of geochemical problems that 

can arise from the mixing of surface water 

and groundwater in the aquifer. These 

problems can result in the long-term decline 

in the effectiveness of these storage systems 

(Hirsch, 2006). 

Desalination – Options to expand freshwater supply include use of impaired water 

such as brackish groundwater or seawater. 

Saline groundwater underlies much of the 

country, as shown in Figure V-5. These 

waters may be converted to potable water by 

using desalination. Desalination requires 

more energy than typical public water 

supplies, as shown in Figure V-6. Energy 

requirements for desalination are similar to 

the requirements for pumping water long 

distances via projects like the California 

State Water Project. 

Another source of brackish water is produced water from oil and gas extraction. 

Produced water from conventional oil and 

gas production is usually saline, while 

produced water from coal bed natural gas 

production may be fresh or nearly fresh. 

Depending on their resultant quality, these 

produced waters may be used with minimal 

cleanup for nonpotable applications such as 

irrigation. If the water is more heavily 

contaminated, treatment and disposal 

following applicable laws and regulations 

may be the only alternative. 

Figure V-5. Degraded Water Resources of the U.S. 

(USGS, 2003)
47

0

2000

4000

6000

8000

10000

Public Brackish Saline

kWh per acre foot of water

Goal

State Water 

Project (CA)

Figure V-6. Energy Requirements for 

Water Desalination (CEC, 2005; Watson 

et al., 2003; Pankratz and Tonner, 2006; 

Miller, 2003; Affordable Desalination 

Coalition, 2006) 

Use of Degraded Water – Freshwater 

supplies can be supplemented by use of degraded water, such as produced water from 

oil and gas extraction (Figure V-7) and 

discharge from wastewater treatment plants. 

Degraded water can be recycled into applications such as EOR, or it can be treated, if 

necessary, and made available for 

various uses, such as irrigation, power plant 

cooling, and industrial and domestic uses. 

Re-use/recycle reduces withdrawal rates and 

pumping costs but may increase energy 

needed for treatment.

Coordinated Energy and Water 

Conservation – Water and energy 

conservation measures represent an 

opportunity to stretch both resources. 

Reducing water consumption can save 

energy for water supply and treatment as 

well as for heating water and thus reduce the 

requirements for water for the energy sector. 

Power companies often have the authority to 

invest in programs that save energy, but as 

noted by the California Energy Commission, 

utilities may not have the authority to invest 

in customer programs that lead to energy 

savings by reducing water consumption 

(CEC, 2005). 

Synergistic Energy and Water Production – Throughout the energy sector, there 

are opportunities to co-produce energy and 

water. Locating power plants adjacent to 

water treatment facilities or more brackish 

or produced water resources could at least 

partially displace freshwater needs. In addition, waste heat from power plants can be 

used in some desalination cycles, and biogas 

from wastewater treatment plants can be 

used to generate power. Within the energy 

sector, the need to provide heat for regasification of liquefied natural gas fits well with 

the need to provide cooling for power plants.
48

Figure V-7. U.S. Oil and Gas Resources (USGS, 2006) 

Explanation 

 Oil Production Mixed Production 

 Gas Production Dry Wells 
49

Chapter VI. Addressing Energy-Water Challenges: 

Bridging the Gaps 

To sustain a reliable and secure energy 

future that is cost effective, environmentally 

sound, and supports economic growth and 

development, the energy and water 

challenges and gaps identified in the 

previous chapters must be effectively 

addressed. This includes consideration of 

the impact that water policies and 

regulations have on energy supplies and 

demands, and the impact energy policies and 

regulations have on water demands and 

availability. 

Properly quantifying and valuing energy and 

water resources will enable the public and 

private sectors to better balance the energy 

and water needs of all users and develop 

strategies and approaches to enhance future 

energy security and sustainability. Major 

considerations are described in the following 

sections. 

COLLABORATION ON RESOURCE 

PLANNING 

Collaboration on energy and water resource 

planning is needed among federal, regional, 

and state agencies as well as with industry 

and other stakeholders. In most regions, 

energy planning and water planning are 

done separately. The lack of integrated 

energy and water planning and management 

has already impacted energy production in 

many basins and regions across the country. 

For example, in three of the fastest growing 

regions in the country, the Southeast, 

Southwest, and the Northwest, new power 

plants have been opposed because of potential negative impacts on water supplies. 

(Tucson Citizen, 2002; Reno-Gazette Journal, 2005; U.S. Water News Online, 2002 

and 2003; Curlee, 2003). Also, recent 

droughts and emerging limitations of water 

resources has many states, including Texas, 

South Dakota, Wisconsin, and Tennessee, 

scrambling to develop water use priorities 

for different water use sectors (Clean Air 

Task Force, 2004a; Milwaukee Journal 

Sentinel, 2005; GAO, 2003; Curlee, 2003; 

Hoffman, 2004; U.S. Water News Online, 

2003). Also see Chapter IV, Figure IV-2 for 

other examples. 

Mechanisms, such as regional natural 

resources planning groups, are needed to 

foster collaboration between stakeholders 

and regional and state water and energy 

planning, management, and regulatory 

groups and agencies. These types of 

collaborative efforts are needed to ensure 

proper evaluation and valuation of water 

resources for all needs, including energy 

development and generation. 

SCIENCE AND SYSTEM-BASED 

NATURAL RESOURCE POLICIES 

AND REGULATIONS 

Often, polices or regulations developed to 

support or enhance one area, such as 

increasing domestic energy supplies through 

EOR, could have unintended negative 

impacts on regional or national freshwater 

availability or water quality. System-level 

evaluations by stakeholders and government 

agencies can be used to assess the impact of 

current or proposed natural resource policies 

and regulations and improve future energy 

development and water availability. 

ENERGY-WATER INFRASTRUCTURE 

SYNERGIES 

When the energy infrastructure is evaluated 

in a system context, significant improvements in energy and water conservation can 

often be realized through implementation of 

innovative processes or technologies, colocation of energy and water facilities, or 

improvements to energy and water infrastructures. Past investments in the water 
50

infrastructure by creating dams and surfacewater reservoirs in the U.S. over the past 80 

years have significantly improved the 

availability of water for some applications 

and decreased its availability for other 

applications. There will continue to be 

competition for water resources between 

different users, and ways to reduce these 

conflicts through coordinated infrastructure 

development would be beneficial. 

BRIDGING THE GAPS: DIRECTION 

AND IMPLEMENTATION 

Based on the emerging trends in energy and 

water natural resource availability and use, 

the U.S. will continue to face issues related 

to natural resource planning and management. Available surface water supplies have 

not increased in 20 years, and groundwater 

tables and supplies are decreasing. Ensuring 

ecosystem health could further constrain 

freshwater supplies. 

At the same time, populations continue to 

grow and move to areas with already limited 

water supplies. Based on current water 

markets and values, the growth in energy 

demand, along with stricter environmental 

regulations on cooling water withdrawals, 

could double water consumption for electric 

power generation over the next 25 years, 

consuming as much additional water per day 

as 50 million people or more. 

The increasing and interrelated value of 

water and energy production and electricpower generation has been documented in 

many river basins across the country as 

noted in Chapter IV. Additionally, changes 

in energy strategies in the electricity and 

transportation sectors could further increase 

water consumption and the value of freshwater supplies. 

Two major activities are under way that can 

help provide insight to these emerging critical energy-water challenges. These two 

activities are independent but are closely 

related and should be considered as 

programs and approaches are developed to 

address emerging energy and water issues. 

Subcommittee on Water Availability and 

Quality – In August 2004, the Office of 

Science and Technology Policy and the 

Office of Management and Budget called for 

a “coordinated, multi-year plan to improve 

research to understand the processes that 

control water availability and quality, and 

to collect and make available the data 

needed to ensure an adequate water supply 

for the Nation’s future.” (SWAQ, 2004) 

That work is being carried out by the Subcommittee on Water Availability and Quality (SWAQ), established under the National 

Science and Technology Council Committee 

on Environment and Natural Resources 

(SWAQ, 2004). The SWAQ includes representatives from the federal agencies associated with water management, water monitoring, water availability, and water quality. 

Many of the energy security and reliability 

issues and challenges identified in this report 

are impacted by water availability and quality and the collection of water data. Therefore, many of the challenges identified are 

issues that will be considered by SWAQ in 

its broader review of water research and 

water data needs. The challenges identified 

in this report should be provided to the 

SWAQ for their review and integration as 

they find appropriate. This will provide a 

national-level screening by federal water 

agencies of appropriate priorities and 

implementation strategies. 
51

Energy-Water Research Roadmap – As a 

next step in addressing emerging critical 

energy and water challenges, Congress 

provided funding in FY 2005 for DOE to 

initiate an Energy-Water Science and 

Technology Research Roadmap. 

The purpose of the Roadmap is to help DOE 

and the Nation assess current regional and 

national energy and water issues and concerns, and identify appropriate interactions 

and coordination approaches with federal 

and state energy and water agencies. As defined by Congress, these efforts must ensure 

that the following energy and water issues 

are addressed in the future: 

1. Energy-related issues surrounding 

adequate water supplies and optimal 

management and efficient use of water. 

2. Water-related issues surrounding 

adequate supplies, optimal management, 

and efficient use of energy. 

The Energy-Water Research Roadmap effort 

included a series of workshops with participation by representatives from a broad 

range of user communities, including environmental organizations, policy and regulatory groups, economic development organizations, industry/supplier associations, 

government agencies (federal, state, tribal), 

nongovernmental organizations, science and 

technology providers (national laboratories, 

universities, research institutions), water and 

energy resource management and generation 

and production groups, and other knowledgeable stakeholders from across the 

country. 

The workshops were led by Sandia National 

Laboratories with support from the Utton 

Transboundary Resources Center of the 

University of New Mexico School of Law 

and Lawrence Berkley National Laboratory, 

and were facilitated by McNeil Technologies. The workshops were developed 

under the guidance of Energy-Water Nexus 

Executive Committee and the National 

Laboratory Energy-Water Nexus 

Committee. The Executive Committee 

includes eighteen representatives from the 

federal government, industry, and 

universities. The National Laboratory 

committee includes all of the twelve DOE 

national laboratories. 

Three regional workshops were held to 

identify critical regional issues and needs 

that could be combined to produce a broader 

framework of national issues. These 

workshops were held November 2005 in 

Kansas City (56 participants), December 

2005 in Baltimore (94 participants), and 

January 2006 in Salt Lake City (121 

participants). Each workshop identified a 

number of regional issues and concerns. As 

expected, many of the concerns identified 

are common throughout the country. Most 

regions and subregions, specifically in the 

West, Central, and Southeastern parts of the 

U.S., are trying to deal with growing water 

shortages and the impact of increasing water 

demands of several sectors on future growth, 

energy resource value, and future energy 

and water availability and costs. 

The regional needs-assessment workshops 

were followed by a technical evaluation 

workshop in March 2006 to identify gaps 

between current federal and state energy and 

water research and management programs 

and future needs and directions. This was 

followed by a national technology innovation workshop, held in May 2006, to identify 

major science and technology research and 

development steps needed to address these 

challenges and bridge these gaps. 

SUMMARY 

As identified in this report, the Nation has 

started to experience an increased need and 

value for technologies that allow energy 

production with reduced freshwater intensity. There are a variety of indicators that 

suggest that many regions of the country 
52

may need to reassess the value of energy and 

water resources and consider new technologies and approaches to optimize economic 

growth and support long-term energy and 

water supply reliability and sustainability. 

By the end of 2006, the combined efforts of 

the SWAQ and the Energy-Water Science 

and Technology Research Roadmap should 

provide a much more detailed understanding 

of the major water issues and needs across 

the country. The information developed 

through the SWAQ and the Energy-Water 

Research Roadmap should provide a strong 

foundation to help address these emerging 

energy-water challenges.
53

Appendix A: Water Use in Energy Extraction, Processing, Storage, and 

Transportation 

OVERVIEW 

This appendix provides supporting data on the 

use of water and water resources in the 

various stages of energy-resource extraction 

and production including energy extraction, 

refining and processing, energy transportation, and energy storage. Data are presented 

at a national level, with an emphasis on the 

impacts of energy production, generation, and 

use on water resource availability and water 

quality. 

To permit a relative comparison of the water 

needed to develop and utilize a broad range of 

energy resources, the information is presented 

as the volume of water used per-unit-energyproduced (gallons of water per MMBtu). The 

data are summarized in Figure A-1. Because 

of the extreme variation in the data, a 

logarithmic scale is used in the figure. Some 

fuels, such as coal and uranium, are used 

primarily or exclusively for electric power 

generation. For these fuels, the water use per 

unit of thermal energy is shown here; water 

use per unit of electrical energy is shown in 

Appendix B. 

The details of the water use and impact are 

summarized for each of the major energy 

sectors in the sections below. 

COAL 

Coal Mining – Water needed for coal mining 

varies by mining method, whether it is surface 

mining (approximately 90 percent of current 

Western coal) or underground mining 

(approximately 65 percent of current Appalachian coal) (EIA, 2003a). Typical mining 

processes that require water include coal cutting in underground mines and dust suppression for mining and hauling activities. 

In addition, reclamation and revegetation of 

surface mines also require water, and 

requirements can be highly variable 

depending on a variety of factors including 

coal properties, mining waste disposal 

methods, and mine location. 

Estimates of water requirements for mining 

activities range from 10 to 100 gallons per ton 

of coal mined (1 to 6 gal per MMBtu), with 

the lower range applicable to Western coals 

with minimal revegetation activities, and the 

higher end applicable to underground mining 

of Eastern coals (Gleick, 1994). 

Open-Surface Coal Mine 

Coal can be washed to increase heat content 

and partially remove sulfur. In general, the 

heat content of coal is increased by removing 

some of the noncombustible matter from the 

mined product. An estimated 80 percent of 

Eastern and interior coal is washed (TooleO’Neil, 1998). Western coals typically are 
54

1 10 100 1000 10000 100000

Coal Mining

Coal Washing

Coal Liquefaction

Coal Slurry

Coal Gasification

Natural Gas Extraction &

Processing

Natural Gas Pipeline Operations

Gas Storage in Salt Cavern**

Petroleum Extraction

Enhanced Oil Recovery

Refining

Oil Shale Surface Retort

Oil Shale In-Situ*

Oil Sands

Oil Storage in Salt Cavern**

Uranium Mining

Uranium Processing

Hydrogen Reforming

Hydrogen Electrolysis

Corn Irrigation

Ethanol Processing

Soy Irrigation

Biodiesel Refining

Gal/MMBTU

 *Water Consumption for Electric Power from Evaporatively-Cooled Combined Cycle Gas Turbine 

 **One-Time Use for Solution Mining of Salt Cavern 

 

Figure A-1. Water Consumption for Energy Extraction, Processing, Storage, and 

Transport 

1 MMBtu = approximately 8 gallons of 

gasoline 
55

found in homogeneous seams with low 

sulfur content and are rarely subjected to 

washing. Rather, western coals are usually 

only subjected to crushing and screening to 

facilitate handling and to remove some of 

the extraneous material introduced during 

the mining process. 

Water requirements for coal washing are 

quite variable, with estimates of roughly 20 

to 40 gallons per ton of coal washed (1 to 2 

gal per MMBtu) (Gleick, 1994; Lancet, 

1993). 

In addition to water withdrawn to meet the 

needs described above, water might naturally accumulate in subsurface mines and be 

pumped to the surface. Western mines may 

also have coal seams that must be dewatered. This water, while incidental to mining activities, nevertheless represents withdrawal of groundwater. 

Water pumped from mines may be used to 

supply process needs, including cutting and 

washing. Excess mine water and discharged 

process water are contaminated and require 

treatment via settling ponds or other means. 

On occasion, water is spilled from mining 

operations; 300 million gallons of coal 

sludge spilled in an incident in Kentucky in 

October, 2000 (Clean Air Task Force, 

2004a). Recycling of water in the underground mining process can dramatically 

reduce water consumption. 

By combining 2003 national coal production 

statistics (EIA, 2006) with the data above, a 

rough estimate of national water consumption required for coal extraction (mining and 

washing) is 70 to 260 million gallons per 

day, approximately 3 to 13 percent of freshwater withdrawals for the mining water-use 

sector in 2000 (Hutson et al., 2004). 

Coal Transport – Water is also important 

for the transport of coal. While more than 

70 percent of coal consumed by power 

plants in 2003 was delivered by rail, 

approximately 10 percent of coal was 

transported on the Nation’s rivers (EIA, 

2003b). 

Coal can also be transported by pipeline in 

the form of coal-water slurry. An example 

of such a system was the Black Mesa project, which delivered approximately 5.5 

million tons of coal per year to the Mojave 

Power Plant in southern Nevada, until the 

power plant suspended operations on December 31, 2005. More than 1 billion gallons of water per year were pumped from 

groundwater aquifers to supply water for the 

transport of coal to the plant. Coal slurry 

pipelines typically require water equal to the 

volume of coal or 11 to 24 gal per MMBtu 

(Gleick, 1994). About 70 percent of the 

water can be recycled at the power plant. 

 Coal Barges 

Coal and other cargo transport through locks 

can present energy management challenges 

during low flows. Use of locks reduces 

upstream reservoir storage behind dams and 

can impact downstream power plants. A 

reservoir can lose about 2 to 10 million 

gallons of water for each lock operation. 
56

Figure A-2. Expected Coal Production, 1970–2030 (million short tons) (EIA, 2006) 

 

Expected continued reliance on domestic 

fossil energy sources will require ongoing 

mining of coal. To meet U.S. coal demand, 

the AEO2006 reference case projects 

continued growth in annual coal production, 

with the vast majority for use by the electricgenerating sector. The increase in coal 

production is driven in large part by sulfur 

emission regulations, driving significant 

production increases in the western United 

States as shown in Figure A-2. This is an 

increase of up to12 billion gallons per year 

in water use, enough to support a city of 

200,000 people. Water consumption for 

domestic and commercial needs averages 

30 gal per day per capita nationwide, (Solley 

et al., 1998), but water consumption can be 

much higher in the arid West because of 

irrigated landscaping. 

URANIUM 

Uranium Mining – Gleick provides 

estimates of water consumption in mining 

and processing uranium (Gleick, 1994). 

Water required for uranium mining varies 

from less than 1 gal per MMBtu for 

underground mining to 6 gal per MMBtu for 

surface mines. 

Uranium is primarily mined in three states: 

Wyoming, Texas, and Nebraska. With 

recent interest in energy needs and the need 

to reduce greenhouse gases, older mines in 

New Mexico and Utah are considering 

reopening. By doing so, these mines might 

generate from 3 to 5 million gallons of water 

a day that must be handled and disposed of 

(Hopp, 2005). In the past, this water has 

simply been disposed of by pumping into 

dry arroyos. However, under current 

regulations, the water must be treated to 

remove trace metals before disposal. This 

treatment might make the water usable for 

other applications. 

Uranium Processing – Water is also 

consumed in milling, enrichment, and fuel 

fabrication, with total consumption 

estimated at 7 to 8 gal per MMBtu (Gleick, 

1994). About half of this estimated 

consumption is attributed to enrichment by 

gaseous diffusion; with enrichment by 

centrifuge, the consumption for milling, 

enrichment, and fuel fabrication would be 4 

to 5 gal per MMBtu (Gleick, 1994). 
57

OIL AND GAS 

Oil and Gas Extraction – Onshore oil and 

gas exploration and extraction have 

relatively minor water requirements. Water 

consumption for natural gas extraction is 

negligible, and oil extraction and production 

requires approximately 5 to 13 gallons per 

barrel of oil equivalent (boe) output (0.8 to 

2.2 gal per MMBtu) (Gleick, 1994). 

The largest water use in onshore oil and gas 

extraction is for EOR. Enhanced recovery 

wells are used to inject water, steam, or 

other substances into a producing formation 

to displace and move oil and gas to nearby 

wells. The quantity of water for EOR can 

vary greatly, depending on the age of the 

field and the recovery method. The least 

water-intensive method for EOR (for-ward 

combustion/air injection) requires approximately 81 gal/boe (14 gal per MMBtu) and 

the most water-intensive method (micellar 

polymer) requires approximately 14,000 

gal/boe (2500 gal per MMBtu). Depending 

on the degree of water recycle, the use of 

carbon dioxide for EOR can require more 

than 1000 gal/boe produced (Gleick, 1994). 

Water is typically a by-product of oil, gas, 

and coal-bed natural gas production. In 

1995, the American Petroleum Institute 

estimated that oil and gas operations 

generated 18 billion barrels of produced 

water, compared to total annual petroleum 

production of 6.7 billion boe (both onshore 

and offshore, including crude oil, natural 

gas, and natural gas liquids production) 

(API, 2000). Such produced water varies in 

quality, and some is used for other purposes. 

API indicates that in 1995, approximately 

71 percent of produced water was recycled 

and used for EOR. The amount of water 

produced per well varies greatly. For 

example, water produced by coal-bed 

Drilling Rig

natural gas extraction can vary from 1.3 gal 

per MMBtu in the San Juan Basin (Colorado 

and New Mexico) to approximately 161 gal 

per MMBtu in the Powder River Basin 

(Wyoming and Montana) (Rice et al., 2000). 

EIA projects in the AEO2006 reference case 

that annual production of domestic crude oil 

will increase due to deepwater offshore 

resources and then decline through 2030, as 

shown in Figure A-3. However, as 

productivity at marginal wells declines, the 

use of water for EOR may increase. 

As shown in Figure A-4, natural gas 

production over the same time period is 

projected to increase, with substantial rampup of unconventional production from tight 

sands, shale, and coal-bed natural gas. The 

largest increase of onshore production is 

projected to occur in the Rocky Mountain 

production area. 

Oil Shale and Oil Sands – A recent report 

by the Rand Corporation prepared for the 

DOE reviewed the status of oil shale 

resource and development potential within 

the United States (Bartis, 2005), and it is the 

primary source of the information 

summarized in this section. The U.S. is 
58

Figure A-3. Crude Oil Production of Contiguous States (million barrels per day) 

(EIA, 2006) 

estimated to have 2 trillion barrels of oil in 

the form of oil shale deposits, which is more 

than triple the proven oil resources of Saudi 

Arabia. The world’s largest oil shale deposit 

is the Green River Formation, which covers 

parts of Colorado, Utah, and Wyoming. 

Initial work on oil shale processing focused 

on mining and above-ground processing/ 

retorting that consumed 2 to 5 gallons of 

water per gallon of refinery-ready oil (15 to 

38 gal per MMBtu). Studies from that 

period indicated there were likely sufficient 

water resources in the region, but insufficient infrastructure for a production rate that 

would reduce U.S. oil imports (3 million 

bbl/day). However, growth in water demand 

since that time may invalidate those earlier 

results. Water quality issues were also 

identified, with the primary concern being 

that the post-processed shale residue has a 

high salt content that could migrate to 

surface waters. High salinity damage is 

currently estimated to be a $500 to 750 

million per year problem in the Colorado 

River Basin in which the most shale resources reside. 

Figure A-4. Natural Gas Production by Source, 1990-2030 (trillion cubic feet) 

(EIA, 2006) 
59

A potentially lower-cost approach to shale 

oil production now in prototype testing is in 

situ (below ground) retorting. Electric heaters are used to heat the shale underground, 

and the products are collected from producer 

wells. About 250 to 300 kWh/boe of 

electricity is required to drive the process. 

Approximately two-thirds of the energy 

product is oil, and one-third is similar to 

natural gas. It would take the equivalent of 

all the produced gas to generate enough 

electricity for heating the shale. Water 

consumption with this method appears to be 

dominated by electricity production, but 

processing and decommissioning operations 

would also use water, although much of it 

might be recycled. 

If electricity were being provided by an 

evaporatively cooled Combined Cycle Gas 

Turbine power plant, about a gallon of water 

would be consumed for every gallon of 

refinery-ready oil produced (8 to 9 gal per 

MMBtu). Other electricity production 

options (e.g., using nearby coal resources) 

would change water use accordingly. Water 

quality issues are similar to those for surface 

retorting, except that the shale is left 

underground, which may reduce concerns 

when compared to above-ground processing. 

Plans are to use freeze barrier technology to 

eliminate migration of pollutants from the 

process to underground water supplies 

during operation. However, after 

decommissioning, leaching could still occur. 

Oil sands (tar sands) are a significant energy 

resource in Canada, but a relatively minor 

resource in the U.S. Water consumption at a 

commercial tar sand plant in Canada is 

approximately 8 tons of water per ton of 

product in the largest, most energy-efficient 

facilities (20 to 50 gal per MMBtu) (Gleick, 

1994).

Oil and Gas Processing and Transport – 

Refineries are large industrial complexes, 

with the water withdrawal rate at a typical 

refinery ranging from 3 to 4 million gallons 

per day (CH2M HILL, 2003). Most of the 

water is lost to evaporation, with only about 

30 to 40 percent discharged as wastewater. 

Since process water may contact the petroleum product, wastewater may contain residual product as well as the water-treatment 

chemicals and increased dissolved solids 

typical of blowdown from steam systems 

and cooling towers. Total water consumption is about 1 to 2.5 gallons of water for 

every gallon of product (7 to 18 gal per 

MMBtu) (Gleick, 1994). 

 

 Oil Refinery 

Natural gas requires minimal processing 

after extraction. Gleick reports that 

approximately 2 gal per MMBtu are 

consumed for gas processing, and another 

estimated 1 gal per MMBtu is associated 

with pipeline operation (Gleick, 1994). 
60

Liquefied Natural Gas – Natural gas 

imported from overseas is shipped as 

liquefied natural gas (LNG). LNG requires 

water for regasification, which is often 

provided via an open-loop system. An 

open-loop system requires significant 

volumes of water, up to 200 MGD (Shaferi, 

2005) for heating the LNG to a gas to pump 

into pipelines. The water-quality concerns 

for the open-loop systems are similar to the 

issues associated with open-loop power 

plant cooling: marine life can be drawn into 

intake structures or be subject to thermal 

stresses at the discharge. The final design 

and location of systems will determine 

whether seawater or freshwater is the 

thermal source for regasification. 

Oil and Gas Storage – Seasonal variations 

in demand require that natural gas be stored. 

Natural gas is most often stored in natural 

geologic formations such as depleted gas 

and oil fields and aquifers, but can also be 

stored in salt formations. In addition, the 

U.S. stores oil in the salt caverns of the 

Strategic Petroleum Reserve. 

Salt caverns are created by slurry mining of 

salt formations. Slurry mining requires 

seven gallons of water to create one gallon 

of storage capacity, and most of the resulting 

saline solution must then be discharged 

(Kaufman, 1960). Because of the high 

volumes of water required, nearby surface 

sources are typically used in slurry mining. 

Compared to the discharge, seawater is only 

mildly saline; thus seawater, if nearby, can 

be used as a water source. For mining a 

cavern for oil storage, a one-time use of 

about 50 gal per MMBtu of oil storage 

capacity is required. The water requirement 

for gas storage depends on the operating 

pressure of the cavern, which is limited by 

the depth of the cavern below ground. To 

create a salt cavern operating at 2,000 psi 

would require a one-time use of 500 to 600 

gal per MMBtu of gas storage capacity. 

ALTERNATIVE FUELS 

A variety of other fuels are candidates to 

replace or supplement petroleum products. 

These include corn-based ethanol, biodiesel, 

coal-based synfuel, and hydrogen. 

Synfuels – Gaseous and liquid fuels can be 

produced from coal. The conversion 

process from coal to liquid fuels consists of 

syngas production, Fischer-Tropsch 

conversion from gas to liquid, and then fuel 

refining and upgrading to desired specific 

fuels such as gasoline, diesel, and other 

distillates. Water required to produce one 

gallon of Fischer-Tropsch liquid product 

varies between 4.6 gallons to 6.8 gallons, 

depending on the coal used for the process 

(41 to 60 gal per MMBtu) (Marano and 

Ciferno, 2001). The higher water-use 

number is derived from bituminous coal acquired from the Illinois #6 surface and underground mine. The lower water use 

number is based upon sub-bituminous coal 

acquired from the Powder River Basin 

surface mine in Wyoming. Sub-bituminous 

coal generally has higher moisture content 

than bituminous coal and therefore requires 

less water for the conversion process. 

Coal can also be used to produce synthetic 

gas for use in combustion turbines and other 

applications. Gleick estimates 11 to 26 gal 

per MMBtu are required for coal gasification (Gleick, 1994). 

Hydrogen – Hydrogen is primarily used in 

various industrial processes, from food 

production and electronic manufacturing to 

metal processing and fertilizer production. 

Although hydrogen can be produced via 

electrolysis, photoelectrochemical, biological, and biomass and waste processing, 

almost all of the hydrogen (95 percent) 
61

produced in the U.S. today is produced 

through steam reforming of natural gas. For 

the near term, this method of production will 

continue to dominate. Currently, hydrogen 

production is estimated at 9 million tons per 

year (USDOE, 2002b), with most of the use 

dominated by ammonia production facilities 

(40 percent), oil refineries (37 percent), and 

methanol production plants (10 percent) 

(Spath, 2001). 

Hydrogen production via natural gas steam 

reformation requires about 4.9 gal of water 

for every kilogram of hydrogen produced. 

Water is used in the reaction process as well 

as in plant operation; 95 percent (4.6 gal) is 

consumed. Approximately 1 gallon of water 

is consumed for the conversion of natural 

gas into 1 kg of hydrogen, and 3.5 gallons 

are lost in the production of steam (Spath, 

2001). The energy content of a kilogram of 

hydrogen is about the same as that of a 

gallon of gasoline. Thus, 43 gallons of 

water are required to produce 1 MMBtu of 

hydrogen via natural gas reformation. 

Electrolysis, in which water is used only as 

feedstock, requires 21 gal per MMBtu. 

However, a typical evaporatively-cooled 

thermoelectric power plant will use 100 to 

200 gal per MMBtu to power the 

electrolyzer. If renewable energy sources 

such as wind or photovoltaics were used to 

power the electrolyzer, little additional water 

would be needed. 

Biofuels – Feedstock for current biofuel 

production includes corn and soybeans, 

sources for ethanol and biodiesel respectively, which require large quantities of 

water when grown on irrigated farmland. 

Reduction of water use requires the ability 

to use plant material that does not require 

additional water, including crop and forestry 

waste and crops that do not require much 

irrigation, such as switchgrass. Research is 

under way to develop the processes to 

produce ethanol from the lignocellulose in 

these materials. 

As of 2004, the Renewable Fuels Association (RFA) reported that 81 ethanol plants 

were in operation in the U.S., producing 3.4 

billion gallons of ethanol, a 109 percent increase since 2000 (RFA, 2005). Water use 

for corn production is variable among the 

states, mostly depending on climate conditions and related annual rainfall. The 2003 

national average of water used in irrigated 

corn production was 1.2 acre-feet per acre 

with a yield of 178 bushels per acre (USDA, 

2004a). Based upon the USDA’s figures, 

the average water consumed is 

approximately 2,200 gallons of water per 

bushel. However, water use/yield can vary 

between 500 gal/bushel for Pennsylvania 

and 6,000 gal/bushel for Arizona. 

Harvesting Corn 

Most ethanol is produced via dry mills, with 

only 25 percent of ethanol produced in wet 

mill facilities (RFA, 2005). A dry mill 

averages 2.7 gallons of ethanol per bushel of 

corn, while water use in dry mills averages 

4.7 gallons/gallon of ethanol (Shapouri and 

Gallegher, 2005). Taking into account the 

energy content of a gallon of ethanol, which 

is somewhat less than the energy content of 

a gallon of gasoline, water required for 

production of irrigated corn is 11,000 gal per 
62

MMBtu of water, with a range of 2,500 to 

29,000 gal per MMBtu. Water consumption 

during processing is comparable to water 

use in synfuel processing, averaging 62 gal 

per MMBtu, with a range of 13 to 145 gal 

per MMBtu. Continuing technology 

research and development could reduce 

these values. 

As of 2004, at least 45 biodiesel plants were 

in operation, producing approximately 25 

million gallons of biodiesel with 54 more 

plants proposed or under construction 

(National Biodiesel Board, 2005). Water 

use for irrigated soy production in the U.S. 

varies from 0.2 acre-feet/acre for Pennsylvania to about 1.4 acre-feet/acre for Colorado, with a national average of 0.8 acre-feet 

of water (USDA, 2004a). The average 

output is estimated at 42 bushels per acre 

with a corresponding range from 40 to 51 

bushels per acre. The average water use was 

6,200 gallons of water per bushel of soy 

with a range of 1,600 to 9,000 gal/bushel. 

The conversion process from soy to biodiesel requires 1 bushel per gallon of fuel. 

Water withdrawal for the conversion process 

is about one gallon of water for every gallon 

of biodiesel produced (Sheehan, 1998); 

water consumption is negligible. Water use 

for soy production averages 45,000 gal per 

MMBtu, with a range of 14,000 to 75,000 

gal per MMBtu. Water use during 

processing is only 4.2 gal per MMBtu 

produced. 

Bio-Diesel-Powered Bus 

SUMMARY 

It is difficult to accurately predict future 

energy development directions and 

demands. Sustained natural gas prices and 

concerns over energy security and 

sustainability could increase demand for 

domestic fuel production and processing, 

with associated water needs. Alternatively, 

an increase in imports, especially of refined 

fuels, could lead to a decrease in domestic 

water needs for fuels. 

In examining the potential of domestic and 

sustainable fuel resources, the information 

provided in this appendix suggests that 

future decisions on energy sources and 

processes must take into consideration water 

use and water consumption. 
63

Appendix B: Water Use in Electrical Power Generation 

OVERVIEW 

This appendix provides supporting data on the 

use of water and water resources for electric 

power generation. Data are presented at a 

national level, with an emphasis on the 

impacts of power generation on waterresource availability and water quality. 

To permit a relative comparison of the water 

needed to develop and utilize a broad range of 

energy resources, the information is presented 

as the volume of water used per-unit-energy 

produced (gallons of water per Megawatthour). Not included in this analysis is the 

water required to manufacture and construct 

energy facilities, such as the water used in 

manufacturing the components of, or to 

construct, a power plant. 

Thermoelectric Generation – Fossil and 

nuclear power generation systems, which 

account for about 80 percent of electric power 

generating capacity, require cooling to 

condense the steam turbine exhaust. Power 

plants also use water for other purposes, 

including equipment washing and cooling, 

emissions treatment, and restrooms. 

Depending upon the technology used, the 

water withdrawn for steam condensing may 

be consumed by evaporation in cooling towers or returned to the source, but at a higher 

temperature. Figures B-1 and B-2 show water 

withdrawal and consumption for various 

power plants in terms of gal/MWhe. Also 

included is the water used to provide fuel, 

assuming a nominal thermal-to-electric 

conversion efficiency for that fuel. Because 

of the extreme variation in the data, a 

logarithmic scale is used in the figure. 

From a cost and efficiency perspective, the 

preferred method to condense the steam is the 

use of large quantities of cooling water. The 

amount of water required depends on the 

generating and cooling technologies, as well 

as the ambient meteorological conditions at 

the plant. The range of water withdrawal and 

consumption (including downstream 

evaporation of open-loop systems) is 

presented in Table B-1. 

Prior to 1970, most thermoelectric power 

plants were built adjacent to surface waters 

and withdrew water for cooling and 

discharged the heated water back to the 

source. Withdrawal requirements for openloop cooling are very large: 20,000 to 50,000 

gal/MWh for a typical coal-fired power plant 

having 35 percent efficiency. Today’s fleet of 

pressurized water and boiling water nuclear 

reactors operate at a lower temperature than 

coal plants, so the plants operate at somewhat 

lower turbine efficiency (approximately 

30 percent) and require more cooling water: 

25,000 to 60,000 gal/MWh (EPRI, 2002a). 

At plants using open-loop cooling, essentially 

all of the water withdrawn for cooling is 

returned to the source. However, the water 

discharged is warmer than the receiving water 

Thermoelectric Power Plant 
64

1 10 100 1000 10000 100000

Coal Mining

Coal Slurry

Fossil Steam, Open Loop

Fossil Steam, CL Tower

Fossil Steam, CL Pond

Fossil Steam, Dry

Coal ICGT

Nuclear Fuel Mining and Processing

Nuclear, Open Loop

Nuclear, CL Tower

Nuclear, CL Pond

Nuclear, Dry

Natural Gas Supply

Gas CCGT, Open Loop

Gas CCGT, CL Tower

Gas CCGT, Dry

Solar Tower, CL Tower

Solar Trough, CL Tower

Geothermal Steam, CL Tower

Gallons/MWhe

Figure B-1. Water Withdrawal for Power Generation 

1 10 100 1000 10000 100000

Coal Mining

Coal Slurry

Fossil Steam, Open Loop

Fossil Steam, CL Tower

Fossil Steam, CL Pond

Fossil Steam, Dry

Coal ICGT

Nuclear Fuel Mining and Processing

Nuclear, Open Loop

Nuclear, CL Tower

Nuclear, CL Pond

Nuclear, Dry

Natural Gas Supply

Gas CCGT, Open Loop

Gas CCGT, CL Tower

Gas CCGT, Dry

Solar Tower, CL Tower

Solar Trough, CL Tower

Geothermal Steam, CL Tower

Gallons/MWhe

Figure B-2. Water Consumption for Power Generation 
65

Table B-1. Water Use by Thermoelectric Power Plants 

(EPRI, 2002a; CEC, 2002; CEC, 2006; Grande, 2005; Leitner, 2002; Cohen, 1999) 

 Water intensity (gal/MWhe) 

 Plant-type Process Steam Condensing Other Use 

Steam Withdrawal Consumption Withdrawal Consumption 

OL Cooling 20,000–

50,000 ~300 

CL Tower 300–600 300–480 

CL Pond 500–600 ~480 

Fossil/ 

biomass/ 

waste 

Dry 0 0 

~30** 

Nuclear OL Cooling 25,000–

60,000 ~400 

Nuclear CL Tower 500–1,100 400–720 

Nuclear CL Pond 800–1,100 ~720 

Nuclear Dry 0 0 

~30**

Geothermal 

Steam CL Tower ~2000 ~1400 Not available 

Solar trough CL Tower 760–920 760–920 8 

Solar tower CL Tower ~750 ~750 8 

Other 

OL Cooling 

7,500–

20,000 100 

CL Tower ~230 ~180 

Natural Gas 

CC 

Dry 0 0 

7–10** 

Coal IGCC* CL Tower ~250 ~200 7–10 + 130 (process water) 

OL = Open loop cooling, CL = Closed Loop Cooling, CC = Combined Cycle 

*IGCC = Integrated Gasification Combined-Cycle, includes gasification process water 

Other Use includes water for other cooling loads such as gas turbines, equipment washing, emission 

treatment, restrooms, etc. 

** References did not specify whether values are for withdrawal or consumption. 

body, which can result in increased 

evaporation downstream of the discharge 

point and the need for large volumes of water 

to dilute the effluent to meet discharge water 

quality standards. EPRI estimates water 

consumption for these plants at 300 to 400 

gal/MWh (EPRI, 2002a). 

The large volumes of water used by these 

plants have associated environmental effects. 

Aquatic life can be adversely affected by 

impingement on intake screens, entrainment 

in the cooling water, or by the discharge of 

water that is significantly warmer than the 

source. 

During drought conditions, plants can 

experience sedimentation and fouling of the 

intake system and water flows that are too 

low to meet thermal discharge permit 

requirements. In surface water systems with 

both hydropower and thermoelectric power 

plants, this complicates river management. 

During dry times, it is desirable to store water 

for hydro power and other needs, but 

sufficient water must be made available 

downstream to provide dilution water for 

open-loop power plants. This makes water 

and energy management especially difficult 

during droughts and dry seasons. 
66

Closed-loop cooling systems withdraw much 

less water than open-loop plants, as shown in 

Table B-1, but a significant fraction of the 

water withdrawn is lost to the atmosphere by 

evaporation. Consumption of water in these 

 plants ranges from 300 to 720 gal/MWh 

(EPRI, 2002a). 

Future electric power generation plants will 

most likely move to closed-loop cooling. 

Recent regulatory limits (commonly called 

EPA 316a and 316b) will limit the ability to 

permit new open-loop cooling systems. This 

may limit future water withdrawals, but could 

significantly increase water consumption, as 

described in Chapter IV. 

The highest-efficiency, fossil-based 

electricity-generating technologies employ 

combined-cycle technology. Natural Gas 

Combined Cycle (NGCC) plants burn 

methane and Integrated Gasification 

Combined Cycle (IGCC) units burn synthesis 

gas (syngas) from coal in combustion turbines 

and extract useful heat out of the exhaust gas 

in a heat recovery steam generator. The 

steam is then sent to a steam turbine where 

additional electricity is generated. Typically, 

combined cycle systems are configured as a 

2-on-1 system, where one-half to two-thirds of 

the plant generating capacity is from dual 

combustion turbines and the balance is a 

result of the steam turbine. 

Because the steam cycle is responsible for 

only a fraction of the overall generating 

capacity, combined cycle systems are 

inherently less water intensive than steamonly generating units. However, compared to 

NGCC systems, IGCC systems have process 

water requirements beyond cooling water 

needs (see the section on synfuels above). 

Overall, IGCC and NGCC systems are much 

less water-intensive than state-of-the-art coalbased units using steam turbines with wet flue 

gas desulfurization. For all water-cooled 

thermoelectric technologies, water for cooling 

represents the largest water requirement of the 

unit. 

Alternative Cooling Technologies – As 

discussed in Chapter V, dry and hybrid 

cooling technologies eliminate or reduce the 

use of water to condense steam. However, 

plant water use is not entirely eliminated, 

since water is required for other cooling 

loads, equipment washing, emission 

treatment, restrooms, etc. For example, the 

gas turbine portion of combined-cycle power 

plants uses water for turbine cooling and 

emissions control. 

Geothermal Electric Power – Geothermal 

power plants use the earth as their source of 

thermal energy. Some geothermal wells 

provide steam, while others provide hot 

water. Steam sources use steam Rankinecycle turbines much like coal and nuclear 

plants, but on a smaller scale. Over time, 

geothermal steam sources may decline, not 

because the heat of the resource has been 

consumed, but because the water/steam 

resource is being withdrawn faster than it is 

being recharged. For that reason, it is 

desirable to recharge the resource. 

The Northern California Power Authority 

(NCPA) operates two geothermal power 

plants at the Geysers Known Geothermal 

Resource Area. Their turbines typically 

withdraw approximately 17.0 lb of 

steam/kWh (2000 gal/MWh) from the 

geothermal field (Grande, 2005). The 

condensate from the steam cycle is used in the 

cooling system. Approximately 70 percent of 

the water is evaporated by the cooling tower. 

In an innovative approach to replenishing the 

geothermal reservoir, the remaining 600 

gal/MWh of condensate is augmented by a 

28-mile long pipeline providing treated 

effluent from the City of Clearlake 

wastewater facility. 
67

Geothermal systems using hot water sources 

typically employ an air-cooled binary cycle, 

where the geothermal heat is used to 

evaporate an organic working fluid that drives 

an organic Rankine-cycle turbine. The 

organic working fluid is condensed in aircooled towers, although hybrid wet/dry 

cooling has been explored to improve 

performance in hot weather. In the drycooled systems, all of the geothermal water is 

returned to the geothermal resource, so 

consumption is limited to other site needs. 

Solar Thermoelectric Power – Nine 

parabolic-trough solar thermal power plants, 

totaling 354 MW, have been operating in the 

Mojave Desert for more than 15 years. These 

plants concentrate sunlight to heat a heattransfer fluid, which in turn is used to make 

steam in an unfired boiler. Natural gas can be 

used to provide capacity when there is no 

sunlight or during times of peak demand. 

These plants use evaporative cooling systems. 

Water consumption is 770 to 920 gal/MWh 

(Leitner, 2002; Cohen, 1999). 

 Solar Troughs 

 Solar Power Tower 

A higher temperature approach—the solar 

power tower—has been demonstrated at the 

10 MW pilot-plant scale. Water consumption 

in a commercial-scale facility is estimated at 

750 gal/MWh (Leitner, 2002). In addition, 

Stirling Energy Systems has announced their 

intent to deploy large numbers of 25 kW 

parabolic dish-engine systems. These 

systems are air-cooled and require no water 

except for mirror washing. 

Hydropower – Hydropower supplies a 

significant fraction of the total U.S. electricity 

generation, ranging from 5.8 percent to 10.2 

percent between 1990 and 2003 (EIA, 2005). 

In 1995, the USGS estimated that hydropower’s annual water usage was 3,160 billion 

gallons per day, or more than 20 times that 

used for thermoelectricity (Solley et al., 

1998). The amount of water available for 

hydroelectric power varies greatly, depending 

upon weather patterns and local hydrology, as 

well as on competing water uses, such as 

flood control, water supply, recreation, and 

in-stream flow needs (e.g., navigation and the 

aquatic environment). 

In addition to being a major source of base 

load electricity in some regions of the U.S., 

hydropower plays an important role in 

stabilizing the electrical transmission grid and 

in meeting peak loads, reserve requirements, 

and other ancillary electrical energy needs. 

This is due in part to the fact that hydropower 

can provide an almost immediate response to 

electric energy demands. 

Hydropower project design and operation are 

highly diverse; projects vary from major 

projects with large, multi-purpose storage reservoirs to small run-of-river projects that have 

little or no active water storage. Approximately half of the U.S. hydropower capacity 

is federally owned and operated; the other 

half consists of nonfederal projects that are 

regulated by the Federal Energy Regulatory 
68

Commission. There are at least ten times 

more nonfederal hydropower projects in the 

U.S. than federal projects. Current estimates 

suggest that between 30,000 to 70,000 MW of 

additional hydroelectric generating capacity is 

available in the U.S., with suggested nominal 

values of about 40,000 MW. This includes 

both large and small hydroelectric opportunities and could nearly double current hydroelectric capacity (Hall, 2005). As the cost of 

fossil fuels continues to increase, hydroelectric generation is becoming more economically attractive. 

 Hoover Dam 

Water used in hydroelectric turbines is generally not consumed, but the timing of water 

releases may be shifted in time relative to 

natural flows through reservoir storage and 

release. When hydropower projects involve 

large storage reservoirs, evaporation of water 

from those reservoirs can be a significant 

consumptive use. Estimates suggest an 

average loss for U.S. hydroelectric reservoirs 

of 4,500 gal/MWh (Gleick, 1994) and with 

annual generation of about 300 million MWh 

(EIA, 2006), evaporative losses associated 

with hydropower may be as high as 13 

million gallons per day. However, the water 

stored in hydropower reservoirs usually is for 

multiple purposes; thus, hydroelectric power 

is not the only cause of these evaporative 

losses. 

Other Renewables – Solar photovoltaics and 

wind require no water during normal 

operation. Ocean energy sources require the 

presence of sea water, but none is consumed 

in operation. Of course, water is used in 

manufacturing and construction of these 

facilities, just as is the case for construction of 

coal and nuclear power plants. Water 

consumption in equipment fabrication and 

plant construction is beyond the scope of this 

report. 

Wind Turbines 

Solar Photovoltaic Power Plant 
69

SUMMARY 

It is difficult to accurately predict future 

electricity generation supply and water 

demand. Sustained natural gas prices could 

shift electricity generation technology 

choices, and substantial advancements in 

clean coal technologies could result in 

increased interest in new coal-fired capacity. 

Any measures to reduce the carbon dioxide 

intensity of the electric generation sector 

would also influence technology choices, 

and might spur technologies amenable to 

carbon capture and sequestration such as 

IGCC plants or possibly additional 

construction of carbon-neutral, nuclearbased technologies. It is even more difficult 

to gauge sufficient water availability to meet 

the needs of future electricity projections, in 

part because of the way basic water data are 

collected and electricity supply and demand 

are projected. 

Because water data are typically collected 

on the basis of watersheds or drainage 

basins, and electricity supply and demand 

are usually projected on the basis of census 

divisions and power grid boundaries, the 

two are often incongruent. 

Because of the higher cost and lower 

efficiencies of dry- and hybrid-cooling technologies, owner-operators of thermoelectric 

generators will continue to prefer wet 

cooling and will require access to sufficient 

quantities of water for cooling and process 

needs. As documented in this report, power 

plants still need water for other process 

needs, even for dry cooling. 

The quantity of water needed will vary, 

based on the final mix of renewable technologies, thermoelectric technologies, and 

the ease of application of dry and hybrid 

cooling approaches. Of more importance is 

that, based on regional energy demands and 

water availability, it is possible that major 

changes in electric generation, transmission, 

and distribution approaches will need to be 

supported in different regions of the country 

to address water availability and value 

issues. 
70
71

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