Water is a crucial element to life on Earth. As our quality of life improves, water is furtively becoming more and more important and in many ways becoming a shrinking resource in the same manner as fossil fuels. At the superficial level as population grows so does the demand for irrigation and drinking water. Increased population growth also bears the consequence of greater electricity demand which in turn elevates demand for water to be used in energy production. Further, tightening resources are often accompanied by elevating conflicts. UNICEF estimates that roughly 3 million people die a year from water sanitation issues and that around one in six people lack access to clean drinking water. As a result, water is developing into a larger international concern not only to meet citizen demand but as an issue of conflict resolution and cooperation. The following figure demonstrates the constricting issue of water availability on a global context.
The relationship between water and energy is complex and unfortunately not well-studied. Currently, the Department of Energy is working through Sandia National Laboratories to develop a method of estimating the interconnections between water and energy usage and overall sustainability. As Dr. Webber points out in “Catch 22: Water vs. Energy,” a lack of a regulatory body over water use is troubling. Without an authoritative agency, local governments will be mired in arguments over water rights in areas where multiple cities pump water out of communal reserves. Also, due to shifts in populations to less water-rich locations, the energy sector will be forced to accommodate longer shipping distances which will lead to increased electricity production and consequently more greenhouse gas emissions. Finally, the relationship between renewable energy and water use is often parasitic rather than synergistic. For example, water requirements for ethanol, hydrogen, plug-in-hybrids, and gasoline vehicles are 130-6200, 42, 24, and 7-14 gallons of water per 100 miles traveled. These numbers indicate that water intensity of technologies should perhaps be a more important measure when comparing technologies. In total, for the reasons mentioned here and a multitude of others, policy and regulatory agencies for water use need to be created and integrated with energy policy to develop a comprehensive view of sustainability.
Fresh water use in the United States is dominated by irrigation. Irrigation use accounts for 81% of fresh-water use while domestic demand comes in a distant second at 7%. However, water use in electricity production nearly equals irrigation in water withdrawal (water from electricity production can be returned to the source leading to a low consumption rate). Total water use for energy production was estimated by DOE/NETL at 6.2 billion gallons per day in 2005; therefore, water conservation is key to energy sustainability. As a quantitative comparison, gas/steam combined cycle, coal and oil, and nuclear production of electricity require 7,400-20,000, 21,000-50,000, and 25,000-60,000 gallons of water to generate one Megawatt-hour of electricity, respectively. Further, energy required delivering one million clean gallons of water from a lake or river, groundwater, wastewater, or seawater is 1,400, 18,000, 2,350-3,300, and 9,780-16,500 kilowatt-hours, respectively. In light of these values, it is obvious that technology type can significantly affect conservation strategies and impact our energy portfolio.
A final issue regarding water and energy coupling is the cyclical nature of the problem. To obtain clean water we must invest energy to separate contaminants. To produce electricity we require clean water to prevent scaling and fouling issues which can destroy our energy producing equipment. Finally, once we are done using the clean water for energy production, the resulting water is left in a degraded form of the clean feed and requires processing. As a fortunate consequence, any technological change affecting water use will have a two-fold effect due to the coupled nature of the processes. However, any change made to energy policy without consideration to water use will directly cause problems to water production which will in turn trickle down to the energy sector.
In a similar way to energy, the solution to water conservation will likely come from a myriad of technologies as well as behavioral adaptation. On a small scale, residents have several options for reducing fresh-water demand including grey-water systems, rain-water collection systems, distribution technologies such as drip hoses, and behavioral modifications. On a larger scale, many developing technologies such as water extraction from flue gas, air coolers instead of evaporative coolers, more efficient water treatment facilities using zero-valent iron, and drip irrigation systems are being developed and tested. While it is uncertain what impact each of these technologies will have, the best we may be able to do at the present is to shave a few percentage points off of our water use. Further, the above mentioned technologies can become money sinks and eye-sores to some.
Overall, it should be apparent that water and energy are intimately coupled both in production and necessity. Though society could survive without produced electricity, water is an essential element to life. Despite our need for water, a regulatory body for water use doesn’t currently exist in the U.S. and legislation is currently monopolized by water quality standards. Water as a shrinking resource is often overlooked due to its renewable nature; however, we know that renewable doesn’t mean sustainable; therefore, water conservation and use strategies need to be viewed in the same, “the sky falling,” nature of fossil fuels. Unfortunately for fossil fuels, the industry developed at a faster pace than globalizing regulation. Fortunately for water use, the current lack of significant international legislation provides a blank canvas for cooperative law-making. Governance over water supply should learn from the blunders of the petroleum trade and develop international agreements before supply becomes too scarce. Perhaps the biggest way to enact some form of conservation may be to re-think water pricing in view of electricity demand fluctuation in a broader sense than purely operational cost and to individually meter water use on all levels. This strategy may be viewed as “market meddling” but pricing is an effective policy lever; sometimes the only way to a person’s head is through their wallet. It may be best to conserve with foresight than to face similar problems we have now with oil.
DOE/NETL. IEP – Water-Energy Interface: Power Plant Water Management. Available at http://www.netl.doe.gov/technologies/coalpower/ewr/water/power-gen.html . Accessed March 22, 2010.
Webber ME. Catch 22: Water vs. Energy. Scientific American Earth 3.0 (Special Edition). 2008.
World Water Council. Water Crisis. 2005. Available at http://www.worldwatercouncil.org/index.php?id=25 . Accessed March 22, 2010.