LONGMONT — An official body representing South Platte River water users wants a say in a pending study of how much more can be diverted from Western Slope rivers before Lake Powell drops to a level that stops the turbines in Glen Canyon Dam and makes it harder to meet downstream flow obligations.

“Since we’re involved with the Colorado-Big Thompson project, the largest transmountain diversion in the state, we’re very interested in the results of this study,” Jim Hall, a senior water resources engineer at Northern Water, told his fellow members of the South Platte Basin Roundtable on Feb. 9 in Longmont.

The West Slope water study has been proposed by the Colorado River District and the Southwest Water Conservancy District in coordination with the four West Slope basin roundtables — the Colorado, Gunnison, Yampa-White and Southwest roundtables.

And while the study is meant to answer questions about water availability for the West Slope groups, the information produced will likely be of interest to water providers from San Diego to Greeley.

“I’ve heard input from East Slope roundtable folks that, more than anything, they just want to be engaged in the process and be involved,” said Joe Frank, the South Platte roundtable chair and director of the Lower South Platte Water Conservancy District.

The East Slope roundtables include the South Platte, Metro, Arkansas, North Platte and Rio Grande.

Officials in Aspen may also be interested in the result of the study, as the city’s municipal electric utility gets a small share of its power from Glen Canyon Dam.

Additionally, the Roaring Fork and Fryngpan rivers are at the heart of the broader issue, as local water either flows downstream toward Lake Powell or is sent east to the Front Range through transmountain diversions and subject to the terms of the Colorado River compact.

Chris Treese, the external affairs manager for the Colorado River District, told the South Platte roundtable on Feb. 9 if Lake Powell drops so low it can’t produce hydropower, it also means the dam will not be able release enough water to meet its rolling 10-year obligation under the compact.

“The earlier crisis point, and I don’t think that’s overstating it, is when Lake Powell falls to a level that is below the point where power can be produced through the dam,” Treese explained to the roundtable, after being asked to describe the reasons for the West Slope water study.

“That inevitability leads, without a reverse in the hydrology, to compact administration because when the water levels are low enough that they cannot be released through the power plant, through the turbines, the other release points from Lake Powell are insufficient to release 8.23 million acre feet every year,” Treese said.

“So that means we will get to a point where we are below the 75 million acre-feet, absent a change in the hydrology, absent several good years that really break the drought,” Treese said, referring to how much water is to be released on a ten-year rolling average. “So we’re looking at that and just trying to figure out, what is the water availability?”

“Compact administration” would send a call up the river from California and other lower basin states for those in the upper basin with post-1922 water rights, including large Front Range water providers, to stop diverting water from the Colorado River basin, which includes the Roaring Fork Valley.

The prospect of a “compact call” has also put the Yampa-White and Gunnison roundtables at odds over how best to respond. The Yampa basin wants to reserve the right to dam and divert more water, but if it does, the Gunnison basin is concerned it will hasten such a call.

“The issues framing the need for technical data include the Yampa-White’s call for a ‘development carve-out’ and the Gunnison’s position that development of any sort, any place poses a risk to all current users,” states the proposal for the study, which was prepared by the Colorado River District.

“The purpose of this first phase of technical data development is not meant to answer all of the questions surrounding Colorado River development but to get the four (West Slope) roundtables to a common platform to have fruitful discussions,” the proposal also states. “It is meant to create a starting line.”

Can water be stored on the Western Slope without dropping levels too low in Lake Powell?
Can water be stored on the Western Slope without dropping levels too low in Lake Powell? Credit: Brent Gardner-Smith/Aspen Journalism

Study questions

The first question the study proposes to answer refers to a pivotal level of water in the current operating guidelines for Lake Powell and the Glen Canyon Dam.

“What is the likelihood of the elevation of Lake Powell going below 3,525 feet under selected water supply and water demand scenarios?” the study will seek to answer.

The cited level of 3,525 feet is just above “minimum power pool” level of 3,490 feet.

On Feb. 12 the reservoir was at 3,595.46 feet in elevation, or 46.55 percent full. The reservoir, managed by the Bureau of Reclamation, can hold 24.3 million acre-feet of water when full at the 3,700-foot level. By way of comparison, Ruedi Reservoir, on the Fryingpan River above Basalt, can hold about 100,000 acre-feet.

“Evaluate how often and by how much water users in the upper basin and specifically Colorado would have to reduce demand to maintain Lake Powell elevation above 3,525 feet,” is the second task in the study.

The third task is to “provide an indication of the ‘risk’ to existing Colorado River water users (West Slope and transmountain diversions).”

Southwestern Water and the Colorado River District have each agreed to contribute $10,000 to the study and the four Western Slope roundtables are being asked to put in $8,000 each.

The proposal for the study is expected to be reviewed in March by the Colorado Water Conservation Board, which oversees the roundtables’ spending. The study is to be prepared by Hydros Consulting in Boulder.

A map of Colorado showing the urban areas of the state in red.
A map of Colorado showing the urban areas of the state in red.

South Platte wants in

“I guess we feel like we should be involved in the work, in support of it,” Hall from Northern Water said at the roundtable meeting. “And it’s only fair that the East Slope roundtables, as they are big users of Colorado River water, should contribute financially and also participate in working with consultants as far as looking at this issue, which is perhaps the number one issue within Colorado water right now.”

Kevin Lusk, who represents El Paso County on the South Platte roundtable and is a principal engineer at Colorado Springs Utilities, seconded Hall’s suggestion.

Lusk is also the president of the Twin Lakes Reservoir and Canal Co., which diverts water from the upper Roaring Fork River basin via a tunnel from Grizzly Reservoir.

“I think it’s a great opportunity to work together to look at these critical issues,” Lusk said. “It’s been on the top of everybody’s mind, that has a transmountain diversion, for years. I just think it is very important to work together to figure where this thing is going and what we can do about it. And I think having some East Slope folks at the table can help make sure that the right assumptions are made.”

Treese, of the Colorado River District, found himself in the position of being offered money for a study.

“There isn’t a study out there that can’t be grown,” Treese said, to knowing laughter from the roundtable members, most of whom are water managers and owners.

But, he also said, “We’re funded right now.”

Treese told the roundtable members he had talked with representatives of the Front Range Water Council, which include Denver Water and Aurora Water, about the study at the Colorado Water Congress convention in late January.

“We’re not trying to create or maintain an exclusive study or hold back any of the information,” Treese said. “We recognize that everybody has an interest in this.”

Nonetheless, the South Platte roundtable later directed its chair, Frank, to talk with Colorado roundtable chair Jim Pokrandt, also of the Colorado River District, and seek a seat on the study’s technical committee and to offer again to help fund the effort.

While not included in the roundtable’s motion, there was also a brief discussion of the South Platte roundtable possibly asking the CWCB, when it reviews the proposal, to directly invite the S. Platte roundtable to help fund the study.

Editor’s note: Aspen Journalism and the Aspen Daily News are collaborating on the coverage of water and rivers. The Daily News published this story on Wednesday, Feb. 17, 2016.

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...