Power generation on the Colorado is drying up

Glen Canyon Dam produces just 70% of the power it normally does and may fall to zero if Lake Powell keeps dropping.

(Rick Egan | The Salt Lake Tribune) The Glen Canyon Dam, on the Colorado River in northern AZ, on Tuesday, Aug. 3, 2021.

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The West’s historic drought is not only threatening water supplies but also depressing electrical power generation in Utah, particularly at Glen Canyon Dam.

Low water in Lake Powell means less hydraulic energy to drive water through the mighty dam’s turbines, resulting in far fewer electrons being produced, according to officials with the Western Area Power Administration, or WAPA, the federal agency that markets wholesale power produced on various federal dams in the West.

This will mean higher prices for the electricity WAPA charges its customers, Tim Vigil, the agency’s Colorado River Storage Project manager, told the Legislature’s Public Utilities, Energy, and Technology Interim Committee on Wednesday.

“The elevation has dropped down to where Lake Powell, our largest source of generation at Glen Canyon Dam, is down to a third of [full]. The loss of generation all across the West from hydro is causing pressure on energy prices,” Vigil said. “You combine that with not only drought but short supply in California, and you have a pretty expensive situation for purchasing power when you don’t have enough hydro to generate on your own.”

WAPA supplies power to some 700 retail providers that in turn serve about 40 million people in the West.

To meet its contractual obligations, WAPA expects it will have to buy power on the market and pass those higher costs on to its customers. The agency is anticipating a 35% increase in its costs, but is seeking a rate increase of just 11% effective for two years starting Dec. 1, according to a filing posted to the Federal Register.

(Rick Egan | The Salt Lake Tribune) A boat heads towards the Glen Canyon Dam, from Wahweap Marina, on Tuesday, Aug. 3, 2021.

The proposed rate increase affects those who get power from the Colorado River Storage Project, the network of federal dams that includes Glen Canyon, Flaming Gorge, Aspinall and Navajo Lake. Utah accounts for about a quarter of WAPA’s power generation, Vigil said.

Utah’s largest power provider, Rocky Mountain Power, does not rely on juice from the Colorado, but at least 33 Utah cities do, including St. George, Kaysville and Logan, via Utah Associated Municipal Power Systems (UAMPS), which gets 31% of its electricity from hydropower.

“We’re incredibly tied to the fate of the Colorado River,” said Mike Squires, UAMPS director of government affairs, told Utah lawmakers on Wednesday. “Under the new conditions, we’re experiencing reductions over time [in] the amount of energy that we will see.”

The community-owned utilities served by WAPA can expect to see a financial impact, which will be directly passed to residents, but there is no way to say how much because electricity prices will range wildly.

“As capacity comes off in the West, market purchases can be volatile and at times quite expensive,” Squires said. “So not only are we getting less reliable, dispatchable energy from the river, but we then have to make that up in costs by procuring other energy.”

After 20 years of drought, flows on the Colorado have declined by 20%, leaving many hydro-generating reservoirs severely depleted, none worse than Lake Mead and Lake Powell, whose dams are among the nation’s biggest hydropower plants.

The situation is so dire at Powell that it is at serious risk of reaching “minimum power pool,” the point at which its surface level is too low to move water through Glen Canyon Dam’s turbines. The Bureau of Reclamation’s latest forecast indicates a 1-in-3 chance that the lake level will hit this threshold, set at 3,490 feet above sea level, sometime in 2023.

To reduce those chances, the bureau has been increasing releases from Flaming Gorge and two smaller upstream reservoirs. Still, Lake Powell’s level has not rebounded and currently sits at 3,545 feet, or 30% full.

The same amount of water has been passing through the dam as usual, about 8.5 million acre-feet a year, but it doesn’t pack as much drive because the low water doesn’t carry as much “hydraulic head.”

“As Lake Powell elevation continues to drop, that in turn reduces the amount of power we can generate because we have a drop in power head,” Vigil said. “We’re about 70% of our generation that we’re getting out of the units right now. With the October numbers that just came out, we lost another 6 to 7% of efficiency. If we don’t get some elevation increases in here, it’s kind of a downward spiral.”

The situation at Lake Mead is not as desperate because of the vertical orientation of Hoover Dam’s penstocks, which can be adjusted as lake levels fluctuate. Penstocks are intake structures that control the flow of water into a dam’s turbines. By contrast, Glen Canyon’s horizontal penstocks are fixed.

“Hoover Dam has generator intakes that are far lower than on Lake Powell relative to the [surface] elevation,” Vigil said. “So they aren’t at the point where they’re looking at minimum power pool just yet.”

Vigil said WAPA is taking steps to limit the rate increase as much as possible, but by law, WAPA’s revolving fund must remain solvent. That fund pays for various environmental programs associated with the Colorado River, such as endangered fish species recovery and desalinization, according to Leslie James, executive director of the Colorado River Energy Distributors Association.

What happens when Glen Canyon Dam hits minimum power pool, which could happen? We’re looking at contracts, we’re looking at rates, we’re looking at WAPA’s role, we’re looking at markets and we’re looking at operations. It’s a very hard conversation,” James told the lawmakers. “It’s a struggle, but we’re trying to do our best to meet the objectives of keeping some semblance of the important hydropower resource there but also keeping it affordable.”