Reclamation’s Ideas to Modify Glen Canyon Dam Leave Some Big Questions
By Eric Balken
This month the Bureau of Reclamation hosted a webinar describing possible alternatives to re-engineer Glen Canyon Dam so that it may salvage hydropower generation and continue delivering water at lower levels. For the Bureau of Reclamation to publicly discuss ideas to reengineer the dam is a very big deal — it confirms the glory years of the dam are truly coming to an end. We applaud the agency for taking the first steps toward modifying the dam, but if we want the Colorado River to survive the decades to come, we have to think about more than salvaging some hydropower at Glen Canyon. We have to be prepared to transition past the dam altogether, and address the problems it has created. The sooner that conversation begins, the better it will be for all stakeholders.
You may recall that last summer, Glen Canyon Institute, Utah Rivers Council, and Great Basin Water Network released a report that highlighted the dam’s big plumbing problems, specifically, that at a certain elevation, it will be physically unable to deliver enough water to meet downstream obligations. Reclamation has also expressed concerns about operating the dam solely through the River Outlet Works, the lowest current release of the dam. The dam wasn’t designed to run only on those outlets, and the agency is concerned about its structural ability to do it full time.
A quick recap of terminology: minimum power pool (Elevation 3,490) is the lowest elevation the dam can still produce hydropower, about 20 feet above the dam’s 8 hydropower penstocks. Dead pool (elevation 3,374) is the lowest elevation the dam can still release water (through the four smaller River Outlets Works that don’t produce hydropower). These outlets were built hundreds of feet above the original riverbed so that the accumulating sediment in the forebay wouldn’t prematurely end the functional life of the dam. In the webinar, Reclamation said the life of the dam is 100 years, much shorter than the 700-year lifespan once assumed by the agency.
With Lake Powell reservoir dropping, yet again, to a historical low, and negotiations among Basin states tumultuous as ever, the realities of the Colorado River’s supply-demand imbalance are top of mind, and the need to think about what happens below Glen Canyon Dam’s power pool is more critical than ever. It’s important to remember that the reservoir would likely already be at or below minimum power pool if not for the drastic efforts by Reclamation to prop up the reservoir, including: releasing more water from upstream reservoirs, holding back water from Lake Mead, and reconfiguring the annual releases from Glen Canyon Dam to be smallest in winter and spring months when the reservoir is at its seasonal nadir.
While the risks of the dam’s plumbing problems loom large, the ideas floated by Reclamation were centered around salvaging hydropower production. They included three structural modifications like drilling a new tunnel through the dam, rerouting the lower river outlet works so they could generate hydropower, and drilling a new tunnel around the dam entirely (not so different from Floyd Dominy’s napkin sketch for GCI’s president in the 1990’s). Reclamation also presented three policy scenarios, which are effectively already underway, like increasing solar and wind generation, changing Colorado River operations, or revisiting what the true minimum power pool limit is.
The lowest intake elevation presented was 3,285 feet above sea level, although several options, like ones rerouting around the dam, could theoretically be installed with lower intakes. For reference, the original riverbed elevation was about 3,130 ft, and with sediment accumulated in the forebay of the dam, that elevation is now 3200 ft.
If the dam were re-engineered with outlets at 3,285, what would that look like for Glen Canyon? Zak Podmore posted a great twitter thread exploring this. A deadpool reservoir at this elevation would still back up ~80 miles of the Colorado River, past the Escalante confluence, and the “sediment glacier” of Colorado River silt would start making its way into central Glen Canyon, which currently has very little sediment in it. More of Glen Canyon would be de-watered, but the remaining deadpool would create some big barriers to Glen Canyon’s restoration. And with the smaller reservoir, its lifespan would be greatly diminished by the onslaught of sediment.
Which begs the question: shouldn’t we be solving more than just the hydropower problem? If Reclamation moves forward with any of these modifications, they’ll effectively be lowering the elevation of power pool and dead pool. But lowering the elevation of dead pool doesn’t solve the massive problems with managing a diminished reservoir. Those problems could far outweigh what little hydropower is produced, and need to be considered in the cost-benefit analysis.
Drastic Reservoir Fluctuations
Since Glen Canyon is shaped like a martini glass, reservoir fluctuations become more extreme the lower it drops in elevation. This means that if an “average” Colorado River runoff came into a dead pool Powell reservoir, the outlets wouldn’t be able to match the inflows and it could fluctuate by over 100 feet in a single season. This would create a nightmare scenario for the Park Service to manage boat ramps and marinas, and would hinder the expansive ecological recovery that’s taking place in the tributary canyons upstream.
Water Quality
At shallower levels, bodies of water run the risk of developing toxic algal blooms, especially in warmer environments. At Utah Lake, for example, toxic algal blooms have forced the closure of access due to toxic waters that can be poisonous enough to kill dogs. This could be extremely problematic at the reservoir.
Sediment
None of the design ideas included a long term plan to deal with the sediment accumulating in the reservoir. Sooner or later, this problem must be dealt with. Sediment has already taken up 6.8% of its storage capacity, and with a much smaller pool, that proportion could increase more rapidly. At the webinar, GCI asked if any of the design ideas would allow sediment to move around the dam. Reclamation’s response was that sediment passage was not top of mind, but theoretically, a passage could be designed to bypass sediment around the dam.
If Glen Canyon Dam is to be modified for the long term, it must have the ability to pass sediment downstream. Anything else would be far too short-sighted.
How much is hydropower really worth?
The cost of hydropower modifications at Glen Canyon Dam would be significant. At the meeting, Reclamation officials implied the range would likely be between $500 million and $3 billion dollars. Minimum elevation hydropower production estimates were between 60 and 210 Megawatts, a small fraction of the dam’s 1320 Megawatt capacity. Those are wide ranges for both inputs and outputs, but decision makers and the public should be cognizant of the reality that it just might not be worth spending billions of dollars to chase a small amount of hydropower, especially when considering the aforementioned problems of operating a shrunken reservoir. At that point, it would probably be more beneficial to help surrounding communities and tribes build out new solar and wind capacity, and transition off Glen Canyon’s less-than-reliable hydropower.
Participants in the meeting asked where funding would come from for programs currently paid for by Glen Canyon’s hydropower revenue, like the Adaptive Management Program. Reclamation pointed out that in 2023 it’s coming from appropriations instead of hydropower sales. Reclamation implied this change may be the future solution for many programs including the endangered fish programs.
A number that gets thrown around a lot in the news is that 5 million people get their power from Glen Canyon Dam. A more accurate way of saying that is that 5 million people get a portion of their power from Glen Canyon Dam, and for most of those end customers, that portion is very small. In 2015 GCI released a study that assessed the impact to ratepayers if the dam stopped producing hydropower. It found that there was plenty of electric capacity available to meet demand, but utilities would have to pay market rates instead of the subsidized price from the dam. The average rate increase for residential customers was $.08 per month.
That analysis is almost eight years old, so those numbers will have changed, but the overall picture is likely similar. And we’re already seeing the transition take place, as Western Area Power Administration, the agency who distributes the dam’s power to utilities, has been fulfilling many of its contracts with power purchased elsewhere on the grid.
In other words, when Glen Canyon Dam stops producing hydropower the grid won’t crumble, and most of those millions of customers won’t even notice. The sooner we prepare for that transition, the better it will be for all stakeholders.
Timeline: “A decade is optimistic”
When discussing the potential timeline for any of these modifications to be implemented, Reclamation officials said “a decade is optimistic.” The ideas presented were preliminary, and have “no guarantee of moving forward.” The next steps would be an appraisal study, a feasibility study, the NEPA process, design, and then construction. That’s a long timeframe and will require getting authorization and appropriation of funds from Congress; it’s very possible this dam will have ceased generating hydropower for years by the time Reclamation gets around to modifications.
At that point, the question shouldn’t be “do we want to try and salvage some hydropower from a diminished reservoir?” The question should be, “how do we modify this dam in a way that will stand the test of time, allow passage of sediment around the dam, avoid the problems of dead pool, and optimize the naturalization of the river corridor through Glen Canyon and Grand Canyon?“
GCI and many others have witnessed what happens when Glen Canyon and the Colorado River are allowed to return from under the reservoir. We’re seeing the rebound of riparian ecosystems, geologic features, and whitewater recreation upstream. We’re seeing hundreds of miles of riparian corridor come back to life, teeming with flora and fauna. We’re seeing that just like Canyonlands to the north and Grand Canyon to the south, Glen Canyon is a National Park waiting to be given its chance in the sun.
Overuse and climate change will continue to put pressure on the Colorado River and its reservoirs, requiring the Basin to be strategic about where to store and how to manage water. We have to be realistic about how much we want to spend to chase the diminishing returns of hydropower. We have to be honest about the realities of managing a diminished reservoir behind Glen Canyon Dam, and start to mitigate the problems it has created. Glen Canyon Dam was not designed for our aridifying climate. It’s time to start talking about what comes after Lake Powell — some version of it is probably coming whether we like it or not.
