Would Utah Lake dredging really increase Utah’s water supply? Don’t bet on it

Water providers raise serious doubts about “restoration” project’s claims

(Trent Nelson | The Salt Lake Tribune) The Jordan River meets Utah Lake in Saratoga Springs on Tuesday, March 1, 2022.

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The company proposing to dredge Utah Lake claims its controversial “restoration” project would significantly increase Utah’s water supply by enlarging the lake’s storage capacity and reducing evaporation.

By raising 18,000 acres of artificial islands, Lake Restoration Solutions (LRS) insists, the lake’s volume would expand by 386,000 acre-feet. And the reduced surface area would save up to 30 billion gallons otherwise lost to evaporation each year, while removing invasive reeds from the shoreline would save another 9 billion gallons.

But under closer examination, neither claim holds much water, raising concerns about the island-building project’s unforeseen impacts on water providers that depend on Utah Lake.

(Trent Nelson | The Salt Lake Tribune) The pumphouse where the Jordan River meets Utah Lake in Saratoga Springs on Tuesday, March 1, 2022.

“We are concerned that we haven’t seen any good concrete scientific evaluation that supports that,” said Salt Lake City Public Utilities Director Laura Briefer, speaking on behalf of the Utah Lake Water Users Association. “It doesn’t take into consideration the interconnected distribution plan [for Utah Lake water] and the difference between active and inactive storage on the lake.”

Water from the lake supplies various water districts and canals, which are represented by Briefer‘s association.

LRS president Jon Benson said his company’s figures are preliminary estimates, subject to change as the project’s design comes into sharper focus.

Increasing Utah’s water supply would be a clear public benefit as Utah grapples with prolonged drought occurring at a time of breakneck growth.

In its marketing materials, LRS touts its proposal as one of the largest water conservation projects ever undertaken in the West, citing water volumes on par with some of Utah’s largest reservoirs, such as the 314,000-acre-foot Jordanelle.

“Ongoing drought, dry conditions, and a major influx of people will put significant strain on Utah’s already diminishing water supply,” its website says. “Conservation efforts like this one are absolutely critical to ensure Utahns have access to water right now and in the future.”

A closer look

Dropping the lake bed 7 feet would undoubtedly enable the 150-square-mile lake to hold more water. The problem, however, is a potentially large part of that gain represents an increase in the lake’s “dead pool.” Dead pool is the volume of water in a reservoir’s lower reaches that is unavailable for use.

When full, Utah Lake’s surface is at 4,489 feet above sea level, known as the “compromise” elevation in reference to a historic legal settlement over the lake’s management. The average depth is 10 feet and the lake holds 870,000 acre-feet of water at this elevation. About half the water flowing into the lake escapes into the atmosphere, while the other half flows into the Jordan River through a pump station on the lake’s north shore in Saratoga Springs.

About 10 miles downstream, the river is captured behind the Turner Dam, constructed in 1914 at the Jordan Narrows, and diverted into various canals for delivery to Salt Lake County cities and irrigators.

Operated by the Utah Lake Water Users Association, the pumps can draw water down to 8.7 feet below the compromise elevation, resulting in 710,000 acre-feet of active storage. Today the lake sits midway between compromise elevation and dead pool, at 4,485 feet, and is 60% full, according to the Utah Lake Commission.

What matters for the state’s water supply is lake’s active storage, but it’s not clear that dredging would add much, even though LRS repeatedly cites 386,000 acre-feet.

“Of all the numbers that are preliminary, that’s the most preliminary,” Benson said. “We get into the design of the islands and the topography, and there will be so many things that could adjust that.”

‘An ongoing conversation’

How much of the lake’s increased volume would be active storage?

“That’s an ongoing conversation that we’re having with the water users,” Benson said. “Dead pool has its own benefits. If you drop the lake down 8.7 feet from compromise, the remaining lake is much smaller. You have 160,000 acre-feet.”

For the sake of argument, Benson described a scenario where all the added capacity is dead pool. And say water users drew Utah Lake’s active storage all the way down.

“You would not have just a puddle, but you’d still have a substantial lake. That’s a value to the ecosystem,” Benson said. “We’re working with the water users to help that be a win for them as well is a primary objective here.”

Despite the uncertainty, LRS executives have aggressively touted the project’s water storage and water conservation benefits as they pitch the $6.4 billion project to various state and local leaders. The claim is also central to their quest for $893 million in federal loans under the Water Infrastructure Financing and Innovation Act program, or WIFIA, administered by the Environmental Protection Agency.

The project might not be eligible for this financing unless it materially advances Utah’s ability to provide water. Briefer and others fear that it could do the opposite.

The project, currently under review by the U.S. Army Corps of Engineers, proposes to dredge a billion cubic yards of sediments off the lake bed and pile it up into 34 islands that would rise, on average, 21 feet above the lake’s surface when it’s full.

Briefer and others are concerned that while dredging is underway, stirred-up sediment could impede the pumps that move water into the Jordan River or render the water unusable.

“Our Utah Lake water rights are used to satisfy century-old exchange contracts,” she said. “If that is disrupted, it puts at risk Salt Lake City’s water supply.”

The dredging project’s first phase will dredge lake bed off Vineyard, a few miles east of the pump station.

How much reduced evaporation?

Lake Restoration proposes to sell most of the islands for real estate development as a way to pay for the project, which the company says will clean the lake’s water and result in many other environmental and social benefits. Utah’s scientific community, however, fears island building could compound the lake’s ecological problems stemming from invasive plants and fish, a legacy of effluent dumping, algal blooms and a loss of native biodiversity.

Meanwhile, the company’s filings say the project would reduce evaporation losses by up to 92,000 acre-feet, nearly what Pineview Reservoir holds. But how this amount was calculated is not clear. The islands would reduce the lake’s surface area by 20%, so it is reasonable to assume that the project would reduce evaporation by a similar amount, as the company has claimed.

According to the company’s own filings, current evaporation losses average about 277,000 acre-feet. But 20% of that is about 55,000 acre-feet.

So why is the company claiming up to 92,000 acre-feet, or 30 billion gallons, in reduced evaporation? Because that’s what “current modeling” points to, but the figure remains preliminary and subject to change, according to Benson.

And what about the 9 billion gallons of water savings realized by replacing invasive phragmites with native plants, as LRS proposes to do on 8,000 acres of lakeshore? According to the Utah Department of Natural Resources, it is not known how much water would be saved by removing phragmites since they will eventually be replaced by other water-loving, preferably native plants, such as bulrushes and cattails.

Regardless, phragmites removal is well underway at Utah Lake.

After eight years of mechanical and chemical treatments, the state has reduced phragmites cover around the lake by 70%, leaving about 3,200 acres left to tackle, according to Ben Stireman, Utah’s sovereign lands program director.

Phragmites removal could be complete within a few years, so that is hardly something LRS needs to even propose, much less take credit for when it comes to water savings.