Energy and water are inextricably linked. Water generates power, and, on the other side of the same coin, it takes large amounts of energy to clean and deliver water.
Nearly 6 percent of electricity in the U.S. comes from hydroelectric sources, which capture the natural energy stored in moving water and convert it into electricity. Hydropower has been in play for thousands of year—an original use was to grind grain at small mills.
But now huge dams associated with hydropower are under fire for altering natural flows and water quality.
In most developing countries, elaborate systems are in place to treat and transport water into our homes, onto agricultural fields, and into factories. All of this pumping and disinfection, especially of salt water, can be very energy intensive, requiring large amounts of nonrenewable resources, such as coal.
Understanding this energy-water nexus can help shine a light on our dependency on both and lead us toward conservation.
- A U.S. Congressional mandate to produce 15 billion gallons (56.8 billion liters) of corn ethanol by 2015 would annually require an estimated 1.6 trillion gallons (6 trillion liters) of irrigation water (and even more direct rainfall)—a volume exceeding the state of Iowa’s annual water withdrawals.
- Transferring Colorado River water into southern California requires about 1.6 kilowatt-hours (kWh) of electricity per cubic meter (35 cubic feet) of water; the same quantity sent hundreds of kilometers from north to south through California’s State Water Project takes about 2.4 kWh, primarily for pumping. Because of these delivery mechanisms, the energy required to provide drinking water to a typical southern California home can rank third behind that required to run the air conditioner and refrigerator.
- Producing 35 cubic feet (one cubic meter) of drinkable water through desalination reverse osmosis (the process of forcing salty water through a membrane to remove the salts) requires about 2 kWh of electricity. Although that’s down from 5-10 kWh 20 years ago, it is still energy intensive.