By rushing to turn on their automatic sprinkler systems at 5 a.m. Monday morning, homeowners and businesses in the Denver metropolitan area are placing unprecedented strain on Denver Water’s water system, jeopardizing the supply of locally stored and treated water.

About 80 percent of the utility’s 1.5 million customers have irrigation systems that can be set and left running for the entire season. But too many of them go off at 5 a.m. at the start of the week, a time that has become the witching hour for Colorado’s largest water utility.

In response, we politely request that more people deviate from the Monday, Wednesday and Friday summer watering schedule and use the Tuesday, Thursday and Saturday time slots instead.

Greg Fisher, manager of demand planning and efficiency, said this trend has been observed for several years as climate change has caused summer temperatures to rise and automatic irrigation systems have become the norm.

“We’re pretty confident that the default hours for new irrigation controllers will be 5 a.m. to 6 a.m. Monday, Wednesday and Friday, and those are the times when we see our maximum hours,” Fisher said.

Water use has now become so high that it is threatening Denver’s supply of locally stored, reclaimed water. If that doesn’t change, it could mean the utility will have to upgrade its delivery system and increase the amount of reclaimed water it stores for daily use, Fisher said.

In Thornton, too, the sharp increase in water usage by its 165,000 customers on Monday morning was a cause for concern, said Emily Hunt, the fast-growing city’s water resources manager.

“We definitely notice the really big spikes,” Hunt said. “Our system can handle that right now, but we have to keep an eye on it because your equipment and pumps are working so much harder. That can be really challenging.”

And that is unlikely to change in the near future, as summers in Colorado are getting hotter and hotter.

“Climate models consistently show that our summers are getting hotter, and along with the higher temperatures, we’re seeing moisture being removed from the soil and the landscape more quickly,” said Peter Goble, a climatologist at Colorado State University’s Colorado Climate Center.

“So it’s logical that irrigation needs will increase if you try to maintain the same green space as before,” he said.

Castle Rock has some of the strictest lawn watering regulations in the state, and that partly explains why the city has been able to handle the new spikes in demand, says Mark Marlowe, director of Castle Rock Water.

For example, the city only allows homeowners to irrigate every three days, while businesses are allowed to irrigate three days a week.

“The only reason Castle Rock originally implemented watering days was because our infrastructure wasn’t big enough to allow everyone to water on the same day,” he said. “To be honest, if we had everyone water on the same day, we’d have the same problem as Denver.”

Despite this summer’s record-breaking heat, the Ute Water Conservancy District in Grand Junction has been largely stress-free when it comes to peak water demand. It is the region’s largest water provider, serving about 80,000 customers.

“We’ve seen some elevated temperatures,” said Larry Cleaver, the utility’s manager. That’s because unlike many newer water systems, Ute forces its customers to use untreated water from old irrigation canals to water their lawns, so the company doesn’t have to treat drinking water and deliver it to homes. Housing developments are built with this two-pipe system.

“But overall we are doing well,” he said.

According to Goble, the transition from summer to fall will bring hotter weather, and that is not exactly encouraging for water managers.

Denver Water’s Fisher said climate change will continue to cause extreme weather and challenge communities’ ability to manage their water supplies during hot summers.

He hopes that a large number of Denver customers will change their irrigation systems to the Tuesday, Thursday and Saturday schedules so the utility doesn’t have to spend millions of dollars upgrading its pipes and expanding reclaimed water storage facilities.

“The good news is that we can easily avoid these infrastructure costs,” he said.

Story Type: News

Based on facts either directly observed and verified by the reporter or reported and verified by knowledgeable sources.