The city of Aspen told the state late last week it will need 8,500 acre-feet of water storage in order to meet water demands in a hotter and drier world.

The disclosure of how much water storage the city thinks it will need to store in 2065 came as part of a response the city provided Friday to state officials in water court, who were seeking a “substantive” written response by Dec. 29 from the city to issues raised about the potential Maroon Creek and Castle Creek reservoirs.

As part of its response, the city included a Dec. 7 letter from its engineering consultants, Deere and Ault of Longmont, who concluded “the required storage capacity for the city of Aspen is approximately 8,500 acre-feet.”

To help put that into context, Lost Man Reservoir holds 100 acre-feet of water; Grizzly Reservoir on Lincoln Creek holds 590 acre-feet; Wildcat Reservoir, visible from the Snowmass Ski Area, holds 1,100 acre-feet; Harvey Gap Reservoir, north of New Castle, holds 5,060 acre-feet; Paonia Reservoir, west of McClure Pass, holds 20,950 acre-feet; and Ruedi Reservoir on the Fryingpan River holds 102,369 acre-feet.

Engineers at Deere and Ault based their storage estimate on a Nov. 30 study done for the city by Headwaters Corp., titled “Aspen’s Water Future: Estimating the Number and Severity of Possible Future Water Shortages.”

The report, which also was submitted to the court, assumed that a warming climate means less water will be flowing down Castle and Maroon creeks, the city’s two main sources of water, and that the runoff will come earlier.

And, working toward a worst-case scenario, they assumed that the city will not increase water conservation efforts, that large irrigation diversions from Maroon and Castle creeks will not be decreased, and that the city will still try to maintain environmental flow levels on both creeks, which it is not legally obligated to do.

The Headwaters report found that water shortages of over 1,000 acre-feet a year could occur in five out of 100 years, with “shortage” defined to include current irrigation diversions and environmental flows on top of domestic uses.

Deere and Ault then used the Headwaters risk-analysis study to come up with a necessary water storage amount of 8,500 acre-feet to offset the potential water shortages, although its two-page Dec. 7 letter does not describe in detail how it reached its conclusion based on the Headwaters report.

The conclusion from Deere and Ault is different than one made for the city by Wilson Water Group in 2016, which concluded in a report — adopted by the city — that the city would not need new water storage if it took other steps, such as increasing conservation, installing ground wells and using “reuse” water to irrigate its golf course.

In 1965, an engineer working for the city of Aspen selected this location, just below the confluence of East and West Maroon creeks, as the location for a potential 155-foot-tall dam. The city is still on record with the state as intending to build the dam here, if necessary, to meet its future water needs. Credit: Brent Gardner-Smith/Aspen Journalism

Storage rights

The city has been maintaining conditional water storage rights since 1965 for the two potential reservoirs on Castle and Maroon creeks.

The Maroon Creek Reservoir would hold 4,567 acre-feet of water behind a 155-foot-tall dam across upper Maroon Creek, within view of the Maroon Bells, and the Castle Creek Reservoir would hold, as currently decreed, 9,062 acre-feet behind a 170-foot-tall dam across Castle Creek, 2 miles below Ashcroft.

The conditional storage rights, which hold a 1971 decree, are distinct from the city’s absolute diversion rights on Castle and Maroon, which are senior rights and adequately supply the city’s water system today.

In July, the city announced its intention to try to transfer the conditional storage rights out of the Castle and Maroon creek valleys, and it has put a parcel of land next to the gravel pit in Woody Creek under contract and directed staff to begin developing a reservoir there.

A study done by Deere and Ault in September concluded the city could store up to 8,000 acre-feet of water on the Woody Creek site. The city has said it is also looking at other places to potentially store water, including the city’s golf course and the Cozy Point open space at the intersection of Brush Creek Road and Highway 82.

The city has also put forth a settlement proposal to the 10 parties opposing its efforts to maintain its water rights, and the proposal is predicated upon the city transferring its storage rights out of the Castle and Maroon creek valleys.

But no settlement has yet been reached and the city is still officially on the record with the state of Colorado, through its two applications in water court, saying it fully intends to build both the Castle and Maroon creek reservoirs, someday, when necessary.

A detail of a graphic from the September 2017 Deere and Ault study for the city of Aspen, showing the largest potential reservoir, at 8,000 acre-feet, that could be built in Woody Creek. The u-shaped dam, shown in brown, is 5,000 feet long and 60 feet high at its maximum section. Credit: City of Aspen

Outstanding questions

After reviewing the two due diligence applications filed by the city in October 2016 seeking to maintain the conditional storage rights, the division engineer and water court referee in Divison 5 in Glenwood Springs raised a set of threshold issues they wanted the city to address.

The officials asked on Jan. 23 for the city to demonstrate it could secure permits and land-use approvals to build the dams and reservoirs, that it could do so in a reasonable time, that it has a specific plan to build them, and that there was sufficient population growth in Aspen’s water service area to justify storing the water.

The city’s water attorney, Cynthia Covell of Alperstein and Covell in Denver, has been reluctant to respond in detail to the court’s request, which came in the form of a summary of consultation.

In her Dec. 29 letter to the court, Covell suggested it was outside of the court’s purview to ask the city to do so at this point in the proceedings.

“Aspen maintains that much of this concern is based on the division engineer’s view of applicable law, and is beyond the proper scope of a consultation report, but nevertheless, responds as follows …” Covell said in her letter.

Covell then reiterated several points that city officials have been making over the past year, including that the city today does not have any “meaningful storage facilities” and that climate change projections “demonstrate the need for storage.”

And while she did not make a detailed case to the court that the city of Aspen could build the Castle Creek Reservoir or the Maroon Creek Reservoir, she did say Aspen could get the necessary permits and arrange financing for reservoirs.

“As a financially stable municipality, Aspen has available to it a number of financing options and therefore will be able to construct a reservoir sufficient to store 8,500 acre-feet,” Covell told the court in her letter in the Castle Creek case. “The decreed location of the Castle Creek Reservoir is primarily on private land. Aspen is able to acquire private land by purchase, lease or eminent domain. Legal procedures and mechanisms exist to obtain land-use approvals and permits on federal land, if necessary, including special-use permit, Congressional authorization and presidential authorization.”

On the other hand, Covell included language that alludes to the city’s stated intent to try to transfer the Castle and Maroon rights out of Castle Creek to another location, such as Woody Creek, and then fill that new reservoir with water from both Castle and Maroon creeks.

“Aspen will develop both the Castle Creek Reservoir storage right (to the extent of 8,500 acre-feet) [and] the companion Maroon Creek Reservoir storage right … in order to provide two sources to meet this storage need,” Covell wrote, without specifically mentioning a reservoir outside of the Castle or Maroon creek valleys. “The total amount of storage will be 8,500 acre-feet from both sources, with no more than 8,500 acre-feet to be diverted annually from Castle Creek. Aspen will relinquish the remaining 562 acre-feet decreed to the Castle Creek Reservoir.”

It’s not clear why the city is willing to relinquish 562 acre-feet from the potential Castle Creek Reservoir right, which is now decreed at 9,062 acre-feet, but it may be a reflection of two earlier agreements with adjoining land owners to reduce the size of the reservoir so as not to flood their properties.

In a separate letter to the court regarding Maroon Creek, Covell took a similar stance, saying the city “will be able to construct a reservoir sufficient to store the 4,567 acre-feet per year to be diverted from Maroon Creek,” but didn’t say where that reservoir might be located.

A status conference in the two water court cases is set for Jan. 4. The parties could agree to keep the case on a quasi-administrative track in front of a water court referee, or the case could be set on a trial track in front of a water court judge.

Editor’s note: Aspen Journalism is collaborating on coverage of rivers and water with The Aspen Times, the Glenwood Springs Post Independent, the Vail Daily, and the Summit Daily News. The Aspen Times published this story in its print edition on Tuesday, Jan. 2, 2018 and the Post Independent published it on Jan. 3.

Brent Gardner-Smith, the founder of Aspen Journalism, and who served as AJ’s executive director until August 2021 and as editor from 2011-2020, is the news director at Aspen Public Radio. He's also been...