water use in USDA Region 7 (North and South Dakota, Nebraska, and Kansas), where irrigation is used extensively. In other regions, such as Region 5 (Iowa, Indiana, Illinois, Ohio, and Missouri) where crops are primarily rain-fed, the average is 0.6 gallon per mile. Other studies have put the upper limit substantially higher (e.g., 50 gallons per mile for Nebraska). Sources include: Dominguez-Faus, R., S.E. Powers, J.G. Burken, and P.J. Alvarez. 2009. The water footprint of biofuels: A drink or drive issue? Environmental Science & Technology 43(9):3005–3010; Wu,
, M. Mintz, M. Wang, and S. Arora.
Consumptive water use in the
production of ethanol and petroleum gasoline. Argonne National Labora- tory ANL/ESD/09-1. Online at www. transportation.anl.gov/pdfs AF/557.pdf; King, C.W., and M.E. Webber. 2008. Water intensity of transportation. Envi- ronmental Science & Technology 42(21).
20 Wu et al. 2009.
21 DOE/NETL. 2006. Emerging issues for fossil energy and water: Investigation of water issues related to coal mining, coal to liquids, oil shale, and carbon capture and sequestration.
22 California Energy Commission. 2005. California’s water energy relationship. Final sta report prepared in support of the 2005 IEPR proceeding, CEC-700- 2005-011-SF. Sacramento, CA.
23 Webber, M.E. 2008. Energy versus water: solving both crises together. Scientic American 18(4).
24 The California State Water Project consumes 5.1 billion kWh. California State Water Project. 2010. California state water project today. Online at www.water.ca.gov/swp/swptoday.cfm, accessed on July 22, 1010.
25 Modeer, D.V. 2010. Confronting the intersection of water, energy, and air quality at the Central Arizona Project. Journal of the American Water Works Association.
26 Bureau of Reclamation. 2003. Water 202 : Preventing crises and conict in the West.
27 The probability of conicts is based on a combination of factors includ- ing population growth and the water requirements of endangered species. Multiple locations throughout the Southwest were considered “sub- stantially likely” or “highly likely” to experience water conict by 2025, without factoring in the highly relevant projected eects of climate change. Bureau of Reclamation 2003; Karl,
Union of Concerned Scientists
R., J.M. Melillo, and T.C. Peterson.
Global climate change impacts in
the United States. U.S. Global Change Research Program (USGCRP).
28 USGCRP 2009; Webber 2008; and Ruhl, J.B. 2005. Water wars, eastern style: Divvying up the Apalachicola- Chattahoochee-Flint River Basin. Journal of Contemporary Water Research & Education 131:47–54.
29 Energy Information Administration (EIA). 2010. Annual energy outlook 2010. DOE/ EIA-0383(2010). Washington, DC: DOE.
30 USGCRP 2009. 31 USGCRP 2009. 32 USGCRP 2009.
33 Overpeck, J., and B. Udall. 2010. Dry times ahead. Science 328(5986).
34 Milly, P.C.D., J. Betancourt, M. Falken- mark, R.M. Hirsch, Z.W. Kundzewicz,
P. Lettenmaier, and R.J. Stouer.
Stationarity is dead: Whither
water management? Science 319(5863): 573–574.
35 When the coal ash waste dike associ- ated with the Tennessee Valley Author- ity’s 1,500-megawatt (MW) Kingston Fossil Plant in Tennessee gave way on December 22, 2008, for example, it dumped an estimated 1.1 billion gal- lons of coal ash mixed with water into the Emory River. EPA. 2009. Summary of past and current EPA response activi- ties regarding the TVA Kingston coal ash spill. Online at www.epa.gov/region4/ kingston/summary.html, accessed on August 2, 2010.
36 EPA. 2010. EPA issues comprehensive guidance to protect Appalachian com- munities from harmful environmental impacts of mountain top mining. Press release, April 1. Online at www.epa.gov/ wetlands/guidance/pdf/appalachian_ mtntop_mining_press_release.pd , accessed on July 27, 2010.
37 The EPA is currently studying the water impacts; however, water quality impacts of shale gas production to date are not well documented. The agency notes that along with the expansion of hydraulic fracturing, there have been “increasing concerns about its potential impacts on drinking water resources, public health, and environmental impacts in the vicinity of these facilities.” It “agrees with Con- gress that there are serious concerns from citizens and their representatives about hydraulic fracturing’s potential impact on drinking water, human health and the environment, which
demands further study.” EPA. 2010. Hydraulic fracturing. Online at www. epa.gov/ogwdw000/uic/wells_hydro- frac.html, accessed on July 27, 2010. The importance of water quantity as an issue depends on the yield of the well post-fracturing. For estimates of water quantity, see, for example: King and Webber 2008. Ground Water Protection Council and ALL Consulting note that, “some challenges exist with water availability and water manage- ment,” but suggest the challenges are manageable. Ground Water Protection Council and ALL Consulting. 2009. Modern shale gas development in the United States: A primer. Washington DC: U.S. Department of Energy. April.
38 For more detailed treatments of options and implications, see: USGAO 2009, King and Webber 2008, and DOE 2006.
39 And indeed, given eciency losses, may increase emissions.
40 Once-though systems have historically been the most popular because of their relative simplicity, low cost, and ease of siting power plants in places with abundant supplies of cooling water. Once-through cooling is now rarely implemented due to disruptions to local ecosystems and heightened diculty in siting power plants near available water sources.
41 Most commonly, wet-recirculating systems use cooling towers to expose water to ambient air, and allow evaporation as the water cools back to an appropriate temperature. The water is then recirculated back to the condenser in the power plant. Because wet-recirculating systems only require water withdrawals to replace any water lost in the cooling tower, these systems have much lower water withdrawals than once-through systems.
42 Though no water is required for dry- cooling systems, power plants using dry-cooling systems also require water for system maintenance and clean- ing. In power plants, lower eciencies mean more fuel is needed per unit of electricity, and this in turn leads to higher greenhouse gas emissions. In 2000, 92 percent of all U.S. dry-cooling installations were in smaller power plants and most commonly in natural- gas-combined-cycle power plants. Small power plants are dened as hav- ing an electric generating capacity less than 300 MW. Dougherty, B., T. Page, and S. Bernow. 2000. Comments on the EPA’s proposed regulations on cooling water intake structures for new facilities. Boston, MA: Tellus Institute.