Along with many countries around the world, the United States faces two significant, and sometimes competing, challenges: (1) providing sustainable supplies of freshwater for humans and ecosystems and (2) ensuring adequate sources of energy for future generations.
Along with many countries around the world, the United States faces two significant, and sometimes competing, challenges: (1) providing sustainable supplies of freshwater for humans and ecosystems and (2) ensuring adequate sources of energy for future generations. A new U.S. Geological Survey report reviews the complex ways in which water and energy are interconnected and describes the earth science data collection and research that can help the Nation address these important challenges.
A binding link
Water and energy resources are linked in the most basic ways. Energy is required to withdraw, transport, and treat water for human consumption. A rural homeowner who looks out at his or her backyard might be able to see the electrical pump that withdraws water from underground; an urban dweller can appreciate the energy it takes to operate a large water treatment plant. At the same time, water is required to extract and process fossil fuels (e.g. mining coal or hydraulic fracturing for oil or natural gas); to grow biofuels (corn or sugar cane for ethanol); and to cool thermoelectric power plants that produce electricity.
Scientists and other experts use the word nexus to describe this especially complex relationship. Stemming from the Latin word nectere, “to bind,” nexus can have related meanings of “connection, link” or “center, focus.”
A full understanding of the water-energy nexus is hampered by our incomplete knowledge of some fundamental issues, such as the quantity of freshwater that is available, the amount of water that is used in energy development, the effects that emerging energy development technologies have on water quality and quantity, and the amount of energy required to treat and deliver freshwater.
What we know
Even with these uncertainties, some findings are clear.
• Reducing the use of freshwater and protecting it from contamination conserve energy. Reducing energy use, in turn, conserves water.
• Electricity generation accounts for much of the energy-related water consumption, with most of that water being used for cooling at coal, natural gas, and nuclear power plants.
• Hydroelectric, geothermal, and concentrating solar power plants use renewable sources to generate electricity with low carbon emissions; however, these plants generally consume more water per kilowatthour of generated electricity than power plants that use nonrenewable fuels.
• Production of biofuels is more water intensive than production of hydrocarbon fuels. While biofuels make up about 5 percent of transportation fuels in the United States, the irrigation of crops used to make those fuels consumes as much as one half of the total amount of water consumed in production of all transportation fuels.
• The capture of carbon at fossil-fuel power plants and its subsequent geologic sequestration might lead to improved air and water quality, but these processes consume additional quantities of fuel and water.
• Techniques such as directional drilling and hydraulic fracturing have led to a surge in oil and natural gas development in the United States, but the environmental costs of development operations are not always fully understood.
• The benefits and costs of tradeoffs in options for water and energy development and use need to be weighed, but coordinated planning among energy developers, water developers, water-resource managers, and ecosystems managers can result in mutual benefits.
The report considers a long list of earth science issues relevant to the water-energy nexus including: freshwater availability; water use; ecosystems health; assessment of saline water resources; assessment of fossil-fuel, uranium, and geothermal resources; subsurface injection of wastewater and carbon dioxide and the related potential for induced seismicity; climate change and its effect on water availability and energy production; byproducts and waste streams of energy development; emerging energy-development technologies; and energy for water treatment and delivery.
After highlighting the many challenges found at the water-energy nexus, the report notes in conclusion that these challenges need not be viewed as mutually exclusive options, even though competition for limited water and energy resources is already occurring in some parts of the country. Sometimes water and energy resources can both be protected with prudent management strategies. Furthermore, advances in technology might eventually take some of the edge off the competition associated with water and energy development. As technology continues to evolve in the future, new advances will likely aid our understanding of the important water-energy issues that we face as a Nation and contribute to our ability to address them.
The Water-Energy Nexus — An Earth Science Perspective. 2015. USGS Circular 1407.