WATER POLITICS

For the last two years or so, federal Bureau of Reclamation officials have been fretting publicly about what might happen to Glen Canyon Dam as water levels continue to drop. Currently the surface of Lake Powell is perilously close to the penstocks, or the water intakes that lead to the hydroelectricity turbines. Once those are rendered inoperable, the only way to get water through the dam is via the river outlet works, or ROW.

That could be a problem. First off, there are no turbines on the ROWs, so there would be no hydropower generation. And as Tanya Trujillo, the Interior Department’s assistant secretary for water and science, noted last year, the dam was not built “to operate solely through the outworks for an extended period of time.” Bad things could happen, like cavitation of the ROWs, which could then threaten the very integrity of the dam. Something needs to be done.

Last week, the Bureau for the first time made public six alternatives the agency is considering:

• Construct new, low- (3,245 feet) or mid-level (3,445 feet) power intakes through the dam that would utilize existing turbines, essentially lowering the “minimum power pool” level as much as 200 feet.
• Connect the current ROWs — at 3,374 feet — to the current turbines or install new turbines so hydropower generation could continue until the lake reached “dead pool,” or falls below the ROWs (at which point no water can be released and the Grand Canyon will dry up).
• Build a low-level bypass tunnel through the sandstone around the dam and install new turbines/power plant to allow for low-water releases with hydropower generation. (Simply reopening the original river diversion tunnels, built to allow for the construction of Glen Canyon Dam, was dismissed due to the fact that the openings are completely buried in silt. This bypass would be above the siltation level.)
• Adjust Colorado River operations (e.g. release less water from Glen Canyon Dam, get people to stop using so much water, etc.)
• Retrofit dam to allow it to generate hydropower through existing penstocks at slightly lower levels.
• Invest in other power sources to offset hydropower losses.

 

Any of the first three options would be a major and expensive undertaking. And any of them would also allow Glen Canyon Dam to be operated at much lower lake levels, which would have consequences for Lake Powell, too. Already the reservoir looks radically different than it does at “normal” levels; try to imagine it 130 feet lower?

Currently, the surface of Lake Powell is sitting at 3,522 feet. Minimum power pool is 3,490. Dead pool is 3,370. The alternatives being considered would allow the minimum power pool level to drop to 3,390, according to the chart below (although, theoretically, a 3,285 foot intake would allow the level to drop another 100 feet before hitting dead pool).

 

That would not only reveal more hidden wonders, but would also cause the big slug of silt that is concentrated in the upper reaches of the reservoir to migrate further downstream. And it would wreak more havoc on recreation. I’ll leave you with a good Twitter thread from Zak Podmore mapping out Lake Powell at 3,285 feet.