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Science and Innovations

Study: Water Use Dropping In Western Cities Even While Population Grows

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Many western cities have been able to shrink their total water use in recent decades, even as their populations grew. That’s the finding of a new study published in the journal Water last week. KNAU’s Melissa Sevigny spoke with lead author Brian Richter about how simple water conservation measures could be a cost-effective way to combat shortages in the Colorado River Basin.

How is this possible? How can water use drop while the population grows?

The explanation of that is that they have found ways to encourage people, to incentivize people, to use less water per person on average. What we found across the board in the western Cities that we surveyed—we looked at 20 different cities—we found their average rate of growth from 2000 to 2015 was about 21 percent, yet their average rate of reduction in their water use was 19 percent.

Yeah, that’s surprising. And that included our cities here in Arizona, too, Flagstaff, Phoenix, and Tucson?

Yes. Sure did…. And it turns out that two thirds of the cities in the western United States have been able to do this.

So how are they pulling this off, what’s happening that makes their water use per individual go down?

There were two things that really jumped out for us…. One, outdoor landscaping. It’s not uncommon for western cities to use half or more of their water outdoors, irrigating lawns, big commercial landscape areas and that sort of thing. That was the place the cities saw some of the biggest declines in use, because a lot of them had been financially incentivizing homeowners and businesses to reduce their outdoor irrigation…. The other big part of the story was indoors, on toilets… Back in 1992, we passed the Federal Energy Act—Energy Act, not Water Act. What was interesting about that was the framers, the architects of that energy act recognized that the movement of water, the cleaning of water to get it ready and make it potable for our use, was a very large portion of U.S. energy use. They said, if we can reduce water use, then we’re also going to reduce energy use…. What the Energy Act said was any new toilets sold in the United States from that day forward were going to have to be high efficiency ones. Overnight, the new toilets being sold were using half of the water that they did previously.

After doing this research, what’s your takeaway for the future of water supplies in the West?

I’ve always been a hopeful, optimistic person…I do think we need to freeze the water use, the total water use in cities and farms, as a first step to not doing more damage… In many, many places we need to go beyond that, we need to find ways to use less water. That’s a real challenge in the Western U.S., we’re seeing rapid population growth in a lot of our cities. And we’re seeing a lot of shifting in our population growth with the pandemic… people fleeing out of places like California and going to Bozeman, Montana, Flagstaff, Arizona, and Boise, Idaho. And so it’s really challenging for water managers in these places to absorb that population and not increase their water use. But that’s why the story we tell in our paper is really important, in fact it achievable… The irony is, we have been so wasteful water up to this point, that there’s a lot of room for being more efficient, more conservative, and using less water.

Brian Richter, thank you so much for speaking with me.

You’re very welcome, I enjoyed it.

Melissa joined KNAU's team in 2015 to report on science, health, and the environment. Her work has appeared nationally on NPR and been featured on Science Friday. She grew up in Tucson, Arizona, where she fell in love with the ecology and geology of the Sonoran desert.
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