California's State Water Project (SWP), which transports water from Northern California to Southern California is the state's largest single energy user, consuming 2 to 3 percent of all electricity, Greenbiz.com reported.
But water pumps aren't the only energy consumer. Every step along the way, from source and conveyance to wastewater treatment, requires energy. Yet the report says policymakers rarely consider the energy costs — and potential savings — in water supply planning.
Energy Down the Drain includes three case studies that detail the important energy implications of water supply decisions. For instance, the San Diego County Water Authority (SDCWA), which currently serves nearly 3 million people, estimates that by 2020 it will need at least an additional 100,000 acre-feet of water per year. (An acre-foot is the volume of water that would cover an acre of land one foot deep.)
The NRDC-Pacific Institute study found that taking additional water from the State Water Project and building a seawater desalination plant would consume the most electricity, while improving water efficiency and conservation efforts could save San Diego 767 million kilowatt hours (kWh) — enough electricity power 118,000 households for a year.
Urban water use is not the only sector where energy implications have been ignored. Agriculture uses about 80 percent of California's developed water supply. The report's authors say that means that irrigation supply and farming practices may have important consequences for the state power grid.
As an example, the report studied proposals to retire drainage-impaired land on the west side of the San Joaquin Valley. Decades of irrigation have caused toxic salts to build up in the soil, rendering it practically infertile. The study found that taking this land out of production and using the water to help the environment could save enough energy for 18,000 households. However, transferring the water to cities could dramatically increase energy use.
The report’s findings:
• Water conservation lowers energy use and energy bills.
• Water recycling is a highly energy efficient water source.
• Retiring agricultural land may increase energy use if the water is transferred to other agricultural or urban uses.
• Retiring agricultural land can save energy if the water dedicated to the environment.
• Diverting water above dams costs power and money.
The report also includes specific recommendations to guide policymakers and potential future legislation.
A PDF version of the report is available online. http://www.nrdc.org/water/conservation/edrain/edrain.pdf
