The Water/Energy Nexus:  Saving Water Saves Energy & Reduces Emissions

The famous San Antonio River Walk shows the integration of water resources as a scenic, cultural and recreation amenity in the middle of a large urban area.

In the production of energy, water provides cooling for thermoelectric power plants, both fossil and nuclear and – surprisingly—also for concentrating solar power plants. This is one reason why concentrating solar power is a bad choice for most desert areas, since their groundwater resources are so precious (and a good reason why it will never get off the ground in most parts of the world!)

The water/energy connection is particularly strong in places where water has to travel long distances from source to city, such as Southern California. Water supply and wastewater treatment account for 19 percent of California’s statewide electricity use and 32 percent of all natural gas use, generating 106 million annual metric tons of CO2-equivalent emissions.

Recognizing the water/energy nexus, the City of San Antonio’s energy supplier and water agency partnered to combine wastewater treatment costs with power plant cooling costs.  One of the city’s sewage treatment plants discharges its highly treated sewage into a lake that provides cooling for the nearby electric power plant.

In the coming decades, the water/energy nexus will continue to challenge water and energy planners, and I expect to see more such partnerships and creative undertakings in the future. One way to avoid taxing the energy and water systems is to rely much more on photovoltaic solar and wind power to provide the electric energy for moving and treating water. Read more about the water/energy nexus in Chapter 4 of my new book, Dry Run: Preventing the Next Urban Water Crisis, released last June by New Society Publishers.


[Table:  4.1 ]
Energy use for the water cycle in Southern California is dominated by conveyance (transportation), because of both the distances involved and lifting water more than 3,000 feet to get over the Tehachapi Mountains. In Northern California, most of the water supply flows by gravity from the Sierra Nevada to the urban centers.

Source: California Energy Commission, California’s Water-Energy Relationship, Final Staff Report, 2005, available at: www.energy.ca.gov/2005publications/CEC-700-2005-011/CEC-700-2005-011-SF.PDF.