From planting green roofs to scaling up rainwater harvesting to right-sizing treatment technologies, some Colorado pioneers are testing elements of One Water that, taken together, could significantly advance the movement.
In some ways, good water years worry Steve Hunter, utilities resource manager for the City of Aspen, as much as dry ones. The city’s Integrated Water Resource Plan, released in 2021, looks out to 2070, glimpsing potential shortages and tough possibilities amid population growth, drought, aridification, erratic snowfall, and wildfire risk. The plan maps a way forward for a resilient water supply while caring for the environment, but a key to its success is public awareness of ongoing water scarcity.
“It’s amazing how short people’s memories are when it comes to drought—until they see it at the tap,” Hunter says.
Even in this relatively good water year, Hunter told city councilors in June he was willing to downgrade the stage two water shortage declaration that had been in place since September 2020, but not to lift water conservation mandates entirely.
“We’re a headwater community,” Hunter says. “Even though we have the legal authority to use [our water], that doesn’t always benefit downstream communities, and doesn’t always benefit the environment, which has a massive effect on recreation, which has a massive effect on money coming into the state.”
Aspen’s water plan offers tools to guide decisions for meeting drinking water needs while still supplying water for irrigation, the environment and snowmaking, and to go even further in decades to come, when the forecast projects reduced water availability. The plan projects that by 2070, the city could see a water shortage of around 2,300 acre-feet over two back-to-back dry years and that, by the same year, as much as a 25% increase in outdoor water demand is possible due to climate change. The city’s main water supply, Castle Creek, is adjacent to its back-up water source, Maroon Creek; one wildfire could devastate both and leave the city without clean drinking water. The city has less than a day’s worth of storage space as backup supply. Both creeks rely on snowmelt, and researchers are still pinpointing the extent to which that translates to runoff, with implications for two hydroelectric facilities as well as flows that fish require and boaters and anglers crave.
Public feedback ahead of drafting Aspen’s water plan called on the city to create “a connection between every drop of water that you use in town and water being directly pulled out of rivers and streams.” This more holistic view of water, which sets both voluntary and decreed streamflow goals and requires the city to add water supplies to the stream or reduce use in times of shortage, is unique. The intention to value all of water’s forms and uses, taking a systems-wide approach that considers economic, environmental and social benefits, is fundamental to what’s become known as the One Water perspective. The One Water approach demands breaking barriers that have long divided drinking water, wastewater and stormwater management strategies, pitted one user group against another, and valued some forms of water while seeing others as useless or, worse, an expensive problem to mitigate.
Across Colorado, leaders and researchers are advancing work that matches the goals of a One Water concept, even if they’re not yet calling it that. They’re readying pieces of a puzzle that may lead to more integrated water management as they overcome boundaries around information and planning, and deploy innovative technologies, all with a scarcer future in mind.
For now, some efforts to advance One Water adoption face policy or technological barriers when leaping from the pilot and research stage to a more broadly applicable scale. But these pioneering projects make a first step toward illuminating possible solutions and paths forward.
How water sources could change
Every time a new road is paved, or a new house is roofed, the developer has to plan for where the water to serve the community will come from, and where the water that falls during Colorado’s heavy rainstorms will go when it hits those newly impermeable surfaces and runs off, often laden with pollutants including excess nitrogen, metals, salt or sediment. The amount, timing and quality of that stormwater runoff directly affects the amount and quality that ultimately becomes available for water supply—a connection that is at the heart of One Water.
Stormwater has typically been viewed as a nuisance to manage, but it could be an opportunity, says Shannon Spurlock, senior researcher in public policy and practice uptake at the Pacific Institute. Spurlock is based in Denver but the Pacific Institute works on global water challenges and resiliency.
In Colorado, Spurlock is leading a statewide assessment on the volumetric and economic potential of urban stormwater as a water supply. In addition to the Pacific Institute, the multi-disciplinary project team includes Wright Water Engineers and One Water Econ. The year-long project, expected to conclude in early 2024, will provide some baselines for how much stormwater is available to capture and use under various scenarios, considering variables such as adoption rates, whether or not storage is available, and legal limitations. The economic data might spur demand for integrating stormwater management within existing water administration policies and practices, leading to an uptick in One Water-style planning.
“Colorado faces an ongoing supply-demand gap, so how can we all do our part to help minimize that gap?” Spurlock says. “How can we build out our existing water supplies, how can we develop underutilized water supplies, and what does that look like?”
Jennifer Bousselot (left) and Sybil Sharvelle are collaborating on research at Colorado State University’s Spur campus. Atop a couple of buildings on campus, and also at ground level, the pair are irrigating a series of planters with stormwater and other sources of reclaimed water and testing plant productivity. (Eli Imadali)
The project grew in part from a 2022 U.S. Environmental Protection Agency report, “Pure Potential: The Case for Stormwater Capture and Use” that evaluates stormwater as a resiliency strategy. Water conservation and efficiency often aim for “lowest cost, least expensive hanging fruit,” Spurlock says, such as leak detection to avoid water loss in transit in potable water distribution systems. But EPA’s stormwater report calls for a new menu of options and Spurlock’s study could help elected officials, utility managers, housing developers and others determine whether and how to engage with the untapped potential of stormwater. It could also result in recommendations that could ultimately lead to more reliable water systems and more widespread adoption of One Water approaches.
Dr. Sybil Sharvelle, a professor in civil and environmental engineering at Colorado State University, specializes in water reuse projects. At the CSU Spur campus she’s leading research in the Water Technology Acceleration Platform (Water TAP) Lab, capturing water from five different sources onsite and testing its quality, along with treatment technologies, to generate “fit-for-purpose” water. (Eli Imadali)
But how to turn something as erratic as summer storms into a reliable water source? A team of researchers at the Water Technology Acceleration Platform (Water TAP) Lab at Colorado State University’s Spur campus led by Sybil Sharvelle, a professor of civil and environmental engineering, is working on that. The Water TAP Lab captures water in big cisterns and tests its quality along with different treatment technologies to generate “fit-for-purpose water” from stormwater, graywater, roof runoff, recycled water and river water drawn from the lab’s perch on the banks of the South Platte River in north Denver. A vacant tank is reserved to hold water trucked in from additional, offsite sources, like hydrofracking water and agricultural runoff. Using physical and chemical-based systems like membrane filtration or ultraviolet treatment, as well as nature-based solutions, including bioswales, rain gardens and other green infrastructure, the facility can treat up to 1,000 gallons per day from each source, a sizeable step up from lab benchtop systems that typically treat three to five gallons.
The work is in part to test, validate and innovate technologies, Sharvelle says, and to make those technologies more efficient. “Fit-for-purpose” means treating the water to the appropriate level for its end use. For example, water that will be used to irrigate landscaping or gardens will only be filtered to the minimum quality level safe for that use, not to drinking water quality standards. Developing monitoring and sensing technology for water quality, as well as automation to increase reliable and safe water deliveries, might be the greatest challenge, Sharvelle says.
Just outside the Spur campus Hydro building where the Water TAP Lab is located are planters landscaped with native plants and supplied by treated water. The loveliest piece might be a patch of prairie growing there, where coreopsis and hyssop’s gold and orange blooms ripple in the breeze and bees, butterflies and hummingbirds buzz by. These plots include built-in systems to irrigate using stormwater runoff collected onsite. Through a partnership with Sharvelle, the Mile High Flood District, and the City and County of Denver, Jennifer Bousselot, an assistant professor of urban horticulture and green roof culture with Colorado State University, is testing plant productivity while Sharvelle looks at results to inform stormwater treatment.
The lab also irrigates planters on the roof of the Hydro building. There, chile pepper plants and leafy greens tuck under rooftop solar panels as part of an experiment that uses the plants to keep the panels at optimal electricity-producing temperatures while shade-tolerant plants yield food. It’s a window, contends Bousselot, into creating cities as places where more than people can live. This kind of symbiotic strategy can reduce the urban heat island effect, clean air, evaporatively cool buildings, even protect rooftops from hail and, perhaps most crucially, slow stormwater runoff.
The plants on green roofs consume some water, but most of it drifts through the roots and growth medium, trickling through instead of rushing off the surface. This is just one example of a “green stormwater management” technique, and, says Bousselot, it’s a double-win, slowing the water enough to prevent downstream flooding while making more use of all the water in the system.
“I love this idea of One Water, because it really is a single water system,” she says. “Whether it’s wastewater or stormwater, it has a value, and water is what’s needed in our climate and especially with our population.”
Colorado water law allows for collecting (from rooftops) and using up to 110 gallons of rainwater residentially. This is typically accomplished by attaching a rainbarrel to the downspout coming from a gutter, and can be a higher amount in situations where the captured water use matches what would be allowed for a residential well permit, though that isn’t available for all properties. Green roofs are allowable as long as the roof only intercepts precipitation that falls directly on the roof and doesn’t store water below the plants’ root zone, mimicking the amount of pre-development absorption and consumption that would have occurred on the existing landscape. Certain governments are allowed to detain stormwater, but these systems must be designed so that water drains within a short period of time. To be “net zero” in water use, however, green roofs need to store water from big, intermittent rainstorms for drier days, and Bousselot is convinced they can accomplish this without affecting users downstream.
“The biggest barrier to successful green roof implementation in our state has to do with our Colorado water law, because we can’t capture and reuse,” Bousselot says. “My argument is, it’s an effective use of water and provides a lot of other benefits at a small cost, but I keep banging my head into that issue, so I want to do whatever I can to sort of demonstrate the feasibility of these systems with as low water impact as possible.”
In a test plot at the Colorado State University Spur campus in Denver, Colorado, leadplant and other plants are irrigated with stormwater and other non-traditional supplies such as roof runoff and graywater.
(Eli Imadali)
If these plots prove effective and green roofs become legally more accessible, Bousselot says, a quick scan of buildings in downtown Denver shows 5,000 acres of rooftops that might be able to host a green roof, which would make a palpable difference on sweltering summer days. Denverites liked that idea, voting in 2018 to require commercial buildings over 25,000 square feet to install green roofs, but the ordinance ran into so many hurdles that it was revised to include a suite of options, and most buildings have opted instead for investing in energy efficiencies as an alternative to planting and maintaining green roofs.
From here, research and policies will both need to advance incrementally, one informing or allowing for the other. To start, CSU’s data will help shape the Mile High Flood District’s next criteria manual, which steers designers and engineers on how to meet Clean Water Act requirements to address stormwater runoff from new buildings into waterways, or what’s known as the “in-stream standards.” The district has already experimented with rainwater capture, working with the Denver Green School to install a 3,000-gallon cistern to collect rainwater from its roof. The 8,000-square-foot roof yielded enough water to spray-irrigate an area of landscaping about one-third that size each time it filled. The system was linked with real-time forecasting so it could purge itself to match the anticipated volume of incoming rainstorms.
But more than cutting the water bill, says Holly Piza, research and development director with the Mile High Flood District, running stormwater through vegetated landscaping reduces the volume, reuses it locally, and reduces pollutants flowing downstream, a persistent concern for communities. “I think reusing stormwater is a great solution for the stormwater problem—it is very difficult for local governments to meet the in-stream standards.”
A partnership with Denver Water and some careful accounting made the Denver Green School pilot project possible. It required navigating the maze of existing water rights and using what’s known as a substitute water supply plan, through which Denver Water provided replacement water to the system to avoid harming other water rights. After five years, the system was dismantled. “With any kind of rainwater harvesting system of this scale,” Piza says, “you run into issues with water rights in Colorado.”
These projects demonstrate cost-effective ways to treat stormwater, and perhaps justification for tangling with Colorado’s tricky water rights system to find a way to move forward.
How communities could change
Driving around Sterling Ranch, a master-planned community 20 miles southwest of downtown Denver, it might not immediately be visible that the neighborhood is trailblazing how communities in Colorado could thrive in a drier future. But residents there are using 70% less water than what Douglas County requires to be committed for new development.
Dominion Water and Sanitation District was formed in 2004 in part to address the water, wastewater, and stormwater services of Sterling Ranch, and to help a 33,000-acre service area in northwest Douglas County shift from nonrenewable groundwater to renewable sources. To that end, explains Andrea Cole, general manager of the district, Dominion is building a closed-loop, One Water-type solution to collect and treat return flows to the South Platte. But the community really stepped up by planning for demand management from the start.
“There’s two parts to the equation—there’s the demand management and the supply management,” Cole says. “A true One Water solution takes both of those pieces into mind.”
Rather than planting and later tearing out turf, which is expensive, or trying to retrofit parks with more sustainable water supplies, planners jumped in to cutting demand in the design phase. Homes come with dual water meters that separate outdoor and indoor water use so outdoor use can be charged at a higher rate if users overspend their water budget. Irrigation systems include sensors to determine when watering is needed. Residents are offered a “playbook” of native, drought-resistant plants drafted by the Denver Botanic Gardens, in lieu of looking to thirsty bluegrass that will suffer with every watering restriction
Brock Smethills (left), president of the Sterling Ranch Development Company, and Andrea Cole, general manager of Dominion Water and Sanitation District, pose on a trail at Sterling Ranch, a master-planned community southwest of Denver that has been integrating a One Water-type view from its start. The community has maintained native landscaping, installed dual water meters in all homes, and is working on a regional rainwater harvesting project. (Eli Imadali)
Dominion is also pursuing regional-scale rainwater harvesting, with plans to irrigate facilities that could include recreational turf and community gardens. Design and construction are advancing on this first-of-its-kind, large-scale rainwater harvesting project, which could potentially double the amount of rainwater the community is currently permitted to collect and use. The project will make use of a 2009 legislative bill, which paved the way for such pilot projects to be approved by Colorado’s water court, a process Cole has been cautioned to expect to take two to three years from when they file an augmentation and substitute water supply plan with the state later this year. If it goes through, 15 years of data that Dominion has collected working closely with the Colorado Water Conservation Board on whether rainwater is physically, technically and feasibly available will be made available to other developers considering rainwater harvesting. Their approval could, at least, give similar efforts a map to follow.
Says Cole, “I think folks are watching to see if it can be done and if it can be done cost-effectively.”
Independent journalist Elizabeth Miller has written about environmental issues around the American West for publications including The Washington Post, Scientific American, Outside, Backpacker and The Drake.
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