Northern Arizona University

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The Interrelations of Water and Energy

Dr. Gary Deason, CSE Deputy Director

View the Water and Energy Fact Sheet

Water and energy are rarely considered together although their infrastructures are inextricably linked. This is especially true in the West where water is used for cooling electrical generating plants and where electricity is used to move water over vast distances and high elevations. On the average in the eight Intermountain western states, fossil fuel generation of 1 kilowatt-hour of electricity requires one-half gallon of water. Dominated by coal and gas fired steam generating plants, electrical generation in the Intermountain West consumes over 650 million gallons of water per day, primarily for condensing steam that has been used to drive turbines (Last Straw, p. 1). This is enough water to meet the needs of four million people, about the population of the state of Colorado.

Conversely, enormous pumps moving water throughout the West use extensive amounts of electricity to raise groundwater to the surface, transport it over long distances (even over mountain ranges), distribute it for agricultural and urban uses, move it to waste treatment plants, and return it to surface streams after processing. In arid regions of the Southwest, the largest users of electricity are invariably companies that transfer and distribute water such as the California State Water Project (Energy Down the Drain, p. v).

The interdependency of water and energy exacerbates all of the major environmental problems of the West. With steady population growth, states such as Arizona and Nevada require increasing amounts of water which, in turn, require more energy to access and distribute. Since this increased electrical demand is largely met by fossil fuel- fired electrical generation plants, significant amounts of additional water are required for cooling the plants. More greenhouse gases are emitted, which contribute further to global warming. Atmospheric warming eventually decreases water supplies and forces more intensive pumping from deeper sources or longer distances, resulting in even greater demands for electricity. These interdependencies, which are usually ignored in water and energy planning, create a downward spiral among electrical generation, climate change and water supplies that is cumulative and non-linear.

Seventy percent (70%) of water used in the United States goes to agricultural production with some states such as California using as much as 85% of water for irrigation. Currently in the United States, it takes an average of 1000 liters of water to produce 1 kg of cereal grain and 43,000 liters for 1kg of beef. About 65% of irrigation water comes from underground aquifers, where uncontrolled withdrawal in some areas has caused a fall in the water table of 30m or more (Pimental, BioScience, 2004, p. 910). Withdrawal from the Ogallala Aquifer through the Midwest from southern Minnesota to Texas is three times faster than recharge, creating a rapid depletion of groundwater that threatens future water availability for food production and ranching operations.

Most estimates suggest that as much as 50% of water used for irrigation is wasted due to inefficient technologies, system leaks, evaporation and over-watering. Thus, significant opportunity exists for efficiency improvements and economic benefits. Government water subsidies, which artificially suppress true costs, as well as the failure of planning and policy to associate electrical costs with water use, have diverted attention from this problem. Most farmers know that excess water leads to salting and water-logging which significantly decrease crop production and income. Coordinating exact watering levels with crop types is essential for efficient and profitable farming operations.

Excess water adds significantly to electrical costs, as electricity used for irrigation typically represents 90% of all electricity used on farms (Energy Down Drain, p. v). Depending on local conditions, installation of efficient irrigation systems may save a landowner as much as 45% of overall electrical costs. Even in an urban setting such as San Diego, it has been estimated that 25% of electrical costs can be saved by water conservation measures (Energy Down the Drain, p. vi).

As continual pumping decreases water levels, water sources must be found deeper or further away, sharply increasing pumping demands and electrical costs sharply. Depending on local conditions, electrical costs increase about 32 times for each 100m of pumping depth. It is estimated that 150,000 ha of agricultural land in the United States has already been abandoned because of high pumping costs (Pimental et al, Water Resources, Agriculture and Environment, 04-1). In recent years, drought has intensified water scarcity and pumping needs, causing skyrocketing electrical costs alongside reduced crop yields. Since 2002, the Southwest has seen record numbers of foreclosures and involuntary sales of farms and ranchlands due to drought, high electricity bills, and reduced income from low crop yields.

Because of the interdependency of water and energy, water conservation has the double benefit of saving both water and electricity. Water saved at the consumer end, such as high efficiency clothes washers or drip irrigation, results in significant energy savings because less water needs to be accessed, conveyed, treated, distributed, removed and treated again as waste, all of which are highly energy intensive. There is even a triple benefit in that electricity savings also means less water is needed to cool generating plants. Water use creates a domino effect and so does water savings.

Finally, reducing water use and associated energy needed to move water increases the portion of future energy needs that can be met by renewable energy resources. In a word, the less energy we need, the more likely renewables can supply it. In addition, renewable technologies use less water and produce less pollution than fossil fuel generating plants. By conserving water and reducing or eliminating greenhouse gases, renewables decrease the likelihood of future water shortages driven by climate change. The fact that renewable energy technologies use less water and produce fewer greenhouse gases are two major reasons why the Southwest, and indeed the U.S., should increase renewable energy production as rapidly as possible.

References:
“Energy Down the Drain: the Hidden Costs of California’s Water Supply,” National Resources Defense Council and Pacific Institute, April, 2004.

“The Last Straw: Water Used by Power Plants in the Arid West,” Hewlett Foundation Energy Series, April, 2003.

“Water Resources: Agricultural and Environmental Issues,” David Pimental, et al, BioScience, Vol. 54, No. 10, October 2004.

Water Resources, Agriculture, and the Environment. D. Pimentel, B. Berger,, et al, Ithaca New York: New York State College of Agriculture and Life Sciences, Cornell University Environmental Biology Report.

View the Water and Energy Fact Sheet

   

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