• Zoos in the American West are implementing water conservation measures due to drought conditions.
• The Denver Zoo has significantly reduced its water usage through upgrades like filtration systems and replacing old pipes.
• The Phoenix Zoo focuses on housing animals suited for its hot climate and has upgraded its irrigation systems to save water.

DENVER — Zoos are of necessity big gulpers of water, a fact that has some zookeepers in the drying American West working to rapidly upgrade efficiency and reduce unnecessary irrigation or leaks.

Denver Zoo, formally known as the Denver Zoo Conservation Alliance, has rapidly reduced its demands on threatened and declining water sources, including the Colorado River.

Among the upgrades is a sea lion water filtration system that allows most of the water to be cleaned and reused each time the pool is drained. That’s saving more than 8 million gallons a year, zoo sustainability director Blair Neelands said. “You can get in there, scrub it with a toothbrush and refill it with the same water,” she said.

Similar upgrades to an African penguin showcase reduced its water use by 95% by largely eliminating what’s sent down the drain. (Like a backyard swimming pool, though, these tanks sometimes still need to be drained and refreshed with new water to reduce mineral buildup.)

“The biggest thing for us is swapping from dump-and-fill pools to life-support systems,” Neeland said.

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Another biggie is replacement of a 50-year-old water main with funding of about $3 million from the city. There’s no way of knowing how much that pipe had leaked over the years, but Neeland suspected it was more than a million gallons a year. The savings should become apparent as the zoo tracks its water use over the next few years.

Creating hippo-sized water savings

When The Arizona Republic visited in 2025, the zoo was on the cusp of eclipsing a goal to reduce its water use by half of what it had been in 2018. The zoo had used 80 million gallons in 2024, or about 219,000 a day, a 45% reduction in just a handful of years. Much of the savings had come in the form of smarter irrigation practices and use of drought-tolerant native plants where possible. The landscaping also pivoted to recycled “purple pipe” water from the city, which owns the zoo’s land, restricting potable water to areas where animals really need it.

“When people hear ‘recycled water,’ they get worried about cleanliness and hygiene,” zoo spokesman Jake Kubié said. “But it’s safe for the animals, and it’s not their drinking water.”

Getting past the water conservation goal would mean draining the pool where Mahali the hippo spent most hours lurking with just his eyes, ears and snout visible to visitors. Because he spent so much time in the pool, the water needed daily changes. It amounted to 21 million gallons a year, not to mention water heater bills that drove the cost to $200,000 a year, according to zoo officials. They estimated that Mahali used as much water as 350,000 four-person households.

“This facility is outdated,” Kubié said. “Some day this will become a huge saver of water.”

That day came before year’s end, and it indeed brought a tremendous savings. The zoo shipped Mahali to a new home (and a potential mate) at a wildlife preserve in Texas and drained the pool one last time. Ending the daily change-outs shaved more than a quarter of the zoo’s entire water usage from the previous year. It put the zoo significantly beyond its goal.

Denver Zoo’s water savings are part of a broader waste- and pollution-prevention effort aimed at being a good neighbor in uncertain times, Neeland said.

“Water savings and drought is top of mind for anyone who lives in the Western United States,” she said.

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In Phoenix, a different mix of animals

That’s true of the Phoenix Zoo, as well, where zookeepers must maintain landscaping and animal exhibits in a city that baked under 100-degree-plus high temperatures for a third of the days last year. The zoo creates a “respite in the desert,” spokeswoman Linda Hardwick said, but has no hippos, penguins, grizzly bears or many of the other species that would require big water investments for outdoor swimming or cooling.

“We really specialize in animals that will thrive in the temperatures here,” Hardwick said.

The Phoenix Zoo uses most of its water on landscaping. After a consultant’s 2023 irrigation assessment, the staff centralized irrigation scheduling under a single trained technician and employed technologies including weather-based controllers and smart meters. Salt River Project awarded $70,000 in grant funds for the upgrades and several thousand more for training.

The zoo uses about 189,000 gallons a day, she said. That represents a 17% reduction from 2023, or 20% when adjusted for the year’s particular weather and evapotranspiration demand.

Brandon Loomis covers environmental and climate issues for The Arizona Republic and azcentral.com. Reach him at brandon.loomis@arizonarepublic.com.