The Water-Energy Nexus

Electricity is needed to get water to you, and water is needed to produce electricity. This relationship is explored in the latest issue of “Arroyo” published by the Water Resources Research Center of the University of Arizona.

This 12-page publication has some interesting and little known facts. For instance, do you know the single largest user of electricity in Arizona? It’s the Central Arizona Project which brings water to Tucson.

“Groundwater accounts for 40 percent of Arizona’s water supply. Extraction of groundwater for potable use, on average, consumes 30 percent more electricity than diversions from surface water sources, primarily because of the pumping requirements.”

In Tucson, treating wastewater consumes 1 kilowatt-hour of electricity per 1,000 gallons, while in Benson the cost is 7.3 kWh/kgal and in Patagonia it’s 13.5 kWh/kgal.

Which method of home cooling is more efficient, air conditioners or swamp coolers? “Air conditioners use between 2 to 4 times the electricity of a swamp cooler, but they do not require water. Evaporative coolers use less energy, but require continuous additions of water. The study found that if the electricity is generated by coal, the air conditioner is still a water saver, consuming only 425 gallons per month, while the swamp cooler uses more than 4,600 gallons per month. On the other hand, air conditioners are significantly more expensive to run, and their lower water footprint might not offset their greater energy consumption.” In other words, it depends.

This publication is worth the read. Download it from: http://ag.arizona.edu/azwater/files/Arroyo_2010.pdf

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