Aspen Reaffirms Plans for New Reservoirs With Water Court Filings
The city of Aspen is reaffirming its plans to build reservoirs to store water from Castle and Maroon creeks — but where they might be built has still not been decided.
Attorneys for the city filed two applications May 30 in water court: a diligence application detailing the actions Aspen has taken toward developing the rights over the past six years and an application to change the original locations of the reservoirs. After a water court process, which saw 10 groups oppose the reservoirs, Aspen in 2019 agreed to modify the rights and move the proposed reservoirs out of Castle and Maroon valleys.
The city has previously identified five potential locations for reservoirs: on land the city owns in Woody Creek, Vagneur Gravel Quarry, and three underground sites — the Aspen Golf Course, Cozy Point Ranch, and Zoline Open Space.
“I think the city would try and prioritize sites that we own already, or those that have larger and contiguous areas and focus on those, but I think a lot of it will come down to the feasibility and constructability, and those sites that might have the least impact as well,” said Erin Loughlin Molliconi, Aspen’s utilities director.
Aspen has what’s known as conditional storage rights for up to 8,500 acre-feet of water from Castle and Maroon creeks, which it could store in one or more locations. Conditional water rights allow a water rights owner to save their place in line while they work toward developing the rights.
Since first claiming the rights in 1965, the city every six years filed little-noticed diligence applications to maintain them. But the city’s 2016 diligence filing brought statements of opposition from 10 parties: the U.S. Forest Service, Pitkin County, American Rivers, Western Resource Advocates, Trout Unlimited, Wilderness Workshop, and four private-property owners — two who owned land in the Maroon Creek Valley and two who owned land in the Castle Creek Valley.
The Maroon Creek Reservoir would have had a dam 155 feet tall and would have held 4,567 acre-feet of water in a pristine location in view of the Maroon Bells. The reservoir would have flooded 85 acres of U.S. Forest Service land, including some in the Maroon Bells-Snowmass Wilderness.
The Castle Creek Reservoir would have had a dam 170 feet tall and would have held 9,062 acre-feet of water. The reservoir would have flooded 120 acres on both private and USFS lands, including a small area in the wilderness.
After settling with the opposing parties, Aspen’s total storage rights were winnowed to 8,500 acre-feet, and the city is now required to find a new site or sites to build storage buckets.
Conditional water storage rights that have not yet been developed — such as Aspen’s — are held by many cities, water conservancy districts, and fossil fuel companies across the Western Slope.
Five new potential reservoir sites
Besides the five previously identified sites where the city might want to move its potential water storage, officials had been seeking to add five new reservoir sites to the change case, but ultimately they did not include them. In a March 28 letter to opposers in the 2016 case, the city requested approval to include Thomas Reservoir, Marolt Open Space, Snowmass Reservoir, Ziegler Reservoir, and Wildcat Reservoir in the list of potential locations.
According to the settlements with opposers, the city needs written approval from the opposers to add any new potential reservoir locations, other than the previously identified five (Woody Creek, Vagneur Gravel Quarry, Aspen Golf Course, Cozy Point Ranch, and Zoline Open Space). Aspen did not get that approval from all of the opposers for all of the locations before the May 30 water court filing deadline.
“We can say that some parties did approve of sites,” Molliconi said. “We just didn’t get all parties to approve of all sites.”
Molliconi said the city chose the five additional sites because they already have existing reservoirs or ponds.
“It would be better to get either a partnership with an existing site or enlarge an existing site,” Molliconi said.
It is unclear if the city will pursue adding any of the five new sites to a future proposal. In an emailed statement, officials said they would “continue to respect and honor the stipulations and conditions of other stakeholders in this process.”
“The city intends to maintain site flexibility because we can’t perfectly predict future demands,” the statement said. “We feel it is our responsibility to continue analyses and stakeholder conversations for storage given the need for resource resiliency, storage and demand gaps, and other beneficial uses.”
Bill Hegberg is the association president of Wildcat Ranch, a residential subdivision outside of Snowmass Village. He said he had talked with city officials about including in their plans Wildcat Reservoir, a 1,100-acre-foot lake on Wildcat Creek, a tributary of Snowmass Creek.
“It doesn’t really work when we’ve got a lake that’s a recreation amenity,” Hegberg said. “We aren’t available for that.”
Aspen officials did not provide additional information on how reservoirs in the Brush Creek and Snowmass Creek drainages could be used to provide water to the city.
Environmental conservation organization American Rivers was one of the opposers Aspen settled with in 2019. Matt Rice, American Rivers’ southwest regional director, said the organization couldn’t sign off on the five additional new locations until Aspen provided more information.
“We can’t in good faith approve Aspen’s very vague plans,” Rice said. “But we are not trying to throw up unnecessary roadblocks. They just need to do a little bit more work on that and we can have this discussion in six years, especially if they provide us a longer timeline to get our approval.”
Every six years, holders of conditional water rights must file what’s known as a diligence application with the state’s water court, proving that they still have a need for the water, that they have taken substantial steps toward putting the water to use, and that they “can and will” eventually use the water. They must essentially prove they are not speculating and hoarding water rights that they won’t soon use.
According to the water court filings, the city says the following things count as diligence over the past six years: It has spent about $310,000 to investigate the 10 potential reservoir locations, $300,000 on attorneys fees to “defend” its water rights, and it has continued to improve, operate, and maintain its water systems that serve Aspen residents.
Storage is part of Aspen’s Integrated Water Resource Plan, which was completed in 2021 and lays out options for meeting increasing water demands in a hotter and drier future. In addition to storage, the IWRP options include nonpotable reuse, groundwater wells, using Hunter Creek as a water source, enhanced water conservation, and drought restrictions.
“I think that [IWRP] is part of the reason why keeping these water rights alive was important, too, for the supply and demand,” Molliconi said.
According to the plan, which uses estimates of population growth and climate change to make projections 50 years into the future, the worst water shortages could occur in two consecutively dry years and be about 2,300 acre-feet total over the course of both years.
In recent years, Aspen has worked at reducing customers’ water use — especially outdoor water use — with increased public outreach, a landscape ordinance, automated metering, and tiered water use rates. The city has also stepped up the monitoring of snowpack and streamflow by funding a new SNOTEL site at the headwaters of Castle Creek and Airborne Snow Observatory flights that measure snowpack from planes using light detection and ranging, or lidar.
Steve Hunter, Aspen’s utilities resource manager, said he plans to recommend to City Council on June 10 that the city move into a Stage 1 water shortage declaration, which aims to reduce water use by 10% through voluntary conservation.
Now that the applications are filed, anyone who might want to oppose the city’s plans has 60 days to file a statement of opposition. The 10 original opposers in the case agreed not to fight the city’s efforts to move the rights to the five alternative locations for 20 years.
If the city’s change case is approved, officials would still need land-use and permitting approval to build any eventual new water-storage reservoir and associated infrastructure.
Aspen Journalism is supported by a community nonprofit grant from the city of Aspen.
By: Heather SackettI The Aspen Times I June 7, 2025