Headlines in recent years have heralded soaring increases in global demand for energy, so a report issued in March 2014 by the United Nations, finding that global demand for energy will rise by 50 percent over the next 15 years, was not particularly surprising. The real news was the finding that global demand for fresh water in that same period will increase by 40 percent. Of course, that growth in demand will not all come from the energy sector; it will also be driven by other water-intensive industries, as well as more frequent and widespread droughts, population growth and contamination of freshwater supplies, among other things. Nevertheless, the predicted rise in water and energy demand, taken together, indicate that the availability of an already scarce essential resource is sure to become a significant challenge for power producers and energy policy makers.
How much water are we using?
In the US, electric power generation, agriculture, industry and municipalities are by far the largest water consumers. According to the US Geological Survey, nationwide, approximately 201,000 million gallons per day (mgd) of water are used in thermoelectric power generation (scrubbers on a single coal-fired plant may use up to 5 mgd); 130,000 mgd for agricultural uses (irrigation and livestock); 44,000 mgd for public water supply; 18,000 mgd for industrial uses; and about 4,000 mgd for mining activities, including oil and gas extraction. All "mining" activity nationwide -- mineral, oil and gas extraction -- accounts for approximately 1 percent of total water withdrawals from surface and groundwater sources, although specific regional percentages will vary. At the same time, the water industry is highly energy-intensive, so that an increase in demand for water necessarily increases demand for electricity, making the relationship somewhat circular.
Worldwide, the statistics are more alarming. In a 2012 special report on the water-energy nexus, the International Energy Agency (IEA) found that water withdrawals worldwide for energy production are tremendous. Nearly 15 percent of the world's total freshwater withdrawals are for use in connection with energy production. As one observer noted, this means that the global energy sector withdraws water at a rate equal to the downstream flows of the Mississippi River. At the same time, 20 percent of the world's aquifers today are depleted.
Tensions rise among energy producers and other water users
Disputes over water for energy are playing out across the US. In the southeastern part of the country, hydro- and nuclear power interests have been pitted against municipal and industrial uses of water supplies for decades. Further west and in the northeast, the oil and gas industry wrestles with the potential that restrictions on withdrawals will constrain industry growth. And in the southwestern deserts and California, with sprawling agriculture and booming populations, there is little water to be had for any purpose.
Alternative fuels may actually worsen the water issue
National efforts to combat climate change through reduced power plant emissions may in fact be contributing to the strain on water resources. Nuclear power has among the highest water consumption of thermoelectric technologies, with significant evaporation occurring in the cooling process. Based on widespread media coverage, water use in the production of natural gas has many people worried, although the quantity of water used in gas drilling, and particularly in the hydraulic fracturing techniques used to release gas trapped underground, represents only a very small fraction of water use nationwide. More water is used to water the nation's golf courses.
There is far greater consumption of water in generating power from plants fueled with natural gas. Improvements in technologies for steam turbines and combined cycle gas turbines have reduced water intake, but increased consumption of water (although gas still ranks far lower than other fuel sources in terms of water use per unit of energy produced.) And carbon capture and storage (CCS) technologies that are under development for coal plants also have the potential to increase water consumption.
In terms of alternative fuels, biomass is tremendously water-intensive. The World Energy Council a few years ago studied freshwater consumption in energy production, and found that 90 percent of freshwater used to produce primary energy is used for the production of biomass, but biomass accounts for less than 10 percent of total primary energy production.
Measures to increase use of biofuels may also be exacerbating the water problem. Another recent study indicates that the water consumed in the irrigation of corn crops used to produce ethanol exceeds that of other sources of liquid fuels by as much as two orders of magnitude.
The future of water
The implications of these reports are that policy makers going forward will be required to engage in a complex balancing exercise. Energy policy decisions will have to include not only consideration of price, fuel availability and emissions, but also broader considerations of the cross-sector and even cross-policy trade-offs that may need to occur if certain technologies are emphasized over others. Moreover, in tackling the problem, someone will need to step up to advocate for water interests, which, as the UN report documented, lacks the "great political clout" of the energy sector. There is little margin to get the balance wrong, and little possibility to fix the problem later. This is not an "either-or" choice, as both water and energy are essential to our daily lives and to economic prosperity.
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