Douglas County News-Press

Posted Sunday, July 17, 2022

Elliott Wenzler

Sterling Ranch begins state’s first commercial rainwater harvesting pilot program

As Colorado’s drought drags on, one Douglas County community is hoping to pave the way for a new commercial water source: rain.

Sterling Ranch, a master-planned community in the northwest region of the county, is ready to test the idea out after more than a decade of working with the legislature and gathering data. If it works, it could change the way the entire state thinks about rainwater harvesting. 

“I really think it could be something that municipalities look at in the future,” said Andrea Cole, general manager for Sterling Ranch’s water provider Dominion Water and Sanitation. “It’s getting drier so we have to figure out how to be better and more efficient with our water use.”

Historically, most areas of the state have outlawed the collection of rainwater, requiring that every drop make it to downstream users. Now, Dominion Water is looking to prove they can gather the precipitation without harming others' water rights. “When you go in and develop an area, since you change the landscape, you’re increasing runoff,” Cole said. That added runoff is in part due to the increase in hard surfaces such as roads and roofs, she said. “When it rains on a road, you get more runoff than when it lands in a field,” she said. A 2007 study from Leonard Rice Engineers found that a maximum of about 15% of rain returned to the stream system, according to Water Education Colorado. Cole says the data Dominion has collected shows excess water entering the system because of the hard surfaces there. Now, they will test it out by actually removing the rainwater. 

Rainwater in Colorado

In 2009, two new pieces of legislation related to rainwater were approved. One, House Bill 09-080, allowed limited rainwater to be collected by some homes that use domestic wells and are outside of cities or water districts. The other, House Bill 09-1129, gave permission for up to 10 pilot programs for rainwater harvesting to take place. In 2016, House Bill 16-1005 passed, which allowed most homes to collect two rain barrels for outdoor use on lawns and gardens.

Using diversion structures, the rain for the pilot program will be collected in a small pond in the Willow Creek area. It will then be pumped for outdoor, non-potable uses such as irrigating parks and recreational fields. 

As part of the pilot, Dominion will be required to get their plan approved by a water court. Cole expects that process to take about three years. “We’re pretty confident that we can get through the water court process,” Cole said. “Water rights are always about no harm, no injury, so we have to show that we’re not injuring or harming downstream water rights.”


A spokesperson for Denver Water said the agency would evaluate their impact after seeing the water right application.

“We are always interested in exploring innovative approaches to addressing Colorado’s water supply-demand gap through efficient uses of water, and we look forward to learning more about Sterling Ranch’s plans,” according to the spokesperson.

Sam Calkins with Centennial Water and Sanitation said his department will keep a close eye on the project as they learn more about it. Centennial Water provides water and wastewater services to residents in Highlands Ranch.

“If they can find something that hasn’t been used and doesn’t harm other water rights on the Platte River then it sounds like an interesting idea,” he said.

If it’s successful, Sterling Ranch hopes to expand rainwater harvesting to other areas. The first project is expected to glean up to 60 acre-feet per year. If the whole system can be built out, it could add as much as 400 acre-feet of water per year.  The Colorado State University Extension estimates that a typical household uses about half of an acre-foot of water a year. Cole said she sees the program as a way to reduce the amount of demand for treated, potable water. If successful, she believes it may make sense for other large developed areas to consider doing the same thing to add to their water portfolio. 

Sterling Ranch focuses on water conservation through a program they call “demand management,” which gives residents a live look at their water usage and bills, asking them to manage their own consumption. They also have banned the use of bluegrass, a high-demand turf, and instead offer native, drought-resistant plants for landscaping. Their water provider Dominion, which is set to have about 12,000 homes by 2040, plans to be 90% renewable water by that same time. 

Tracy Kosloff with the state engineer’s office said they would also be monitoring the process of the program. “It seems since no one else has applied that there’s not a lot of demand to do this kind of thing,” she said. “But perhaps once they're actually operational, maybe others will see that and see they want to try to get approval and capture stormwater.”