Lake Tahoe, as seen prior to siphoning. Source: Wikimedia Commons

By Nestle J. Frobish

A new study shows how Lake Tahoe might serve as a mammoth reservoir that could significantly mitigate California’s chronic water shortages without tarnishing the lake’s world-renowned beauty.

The development, reported today (April 1) in the scientific journal Limnology Tomorrow, drew surprise and delight from California water interests who have long regarded the bi-state alpine lake as politically off limits for new water supply.

“Never in my wildest imagination would I have considered this noble sheet of blue water for expanding California’s surface water storage,” said Michael O’Shaughnessy, a veteran of California’s water wars. “But this study has me thinking that there is indeed a way, politically and economically, to siphon Tahoe and bring its pure Sierra snowmelt to our doors.”

The pier-reviewed study reveals breakthroughs in acrylic or Plexiglas technology and hydrologic engineering that would enable construction of a transparent cap covering all 193 square miles of the lake and suspended about 120 feet below its surface.

The cap provides 99 percent light transmission, making the sub-surface reservoir “virtually invisible,” said A. W. Von Schmidt, a civil engineer who led the three-year study by the Reber Foundation of San Francisco.

“Some may view this as a creating false lake bottom,” Von Schmidt said. “We see it more as a true reservoir top. This new Plexiglas is as clear as the lake itself. Tourists who come to Tahoe for its fabled clarity won’t know the difference.”

The study team set the depth of the Plexiglas floor at 120 feet in accordance with the lake’s restoration plan. Lake clarity is routinely measured by lowering a white “Secchi disk” the size of a dinner plate into the lake until it is no longer visible.

Source: UC Davis

“They’ve never seen the plate deeper than 102.4 feet, and that was back in 1968 before all the development,” Von Schmidt said. “We’re giving them an extra 18 feet of depth out of an abundance of optimism.”

Designs to pump and transport Tahoe water to the Sacramento Valley are no less ambitious:

• Water would be drawn from a valve in the Plexiglas top at the lake’s dam in Tahoe City, which releases water to the Truckee River.
• A diversion dam would be built 3.75 miles downstream of the Lake Tahoe Dam. At this point a six-mile canal would branch off from the Truckee flowing into Squaw Valley.
• A five-mile tunnel beginning at the head of Big Rock Candy Mountain Creek would carry the water through the mountains to a tributary of the North Fork American River near Soda Springs.
• The water would then flow along the granite bed of the American River for 12 miles to a 40-mile canal that would link to a large reservoir near Auburn.
• From the reservoir, a pipe would carry the water to Folsom Reservoir, a key source of drinking water for many Sacramento area communities including Fair Oaks, Roseville, Citrus Heights and Folsom.

Looking over a diagram of the proposed Tahoe-to-Folsom water system, Von Schmidt mused, “Why didn’t I think of this earlier?”

The idea of siphoning Lake Tahoe is hardly original. The lake is already a reservoir that operates for irrigation storage and municipal water in the Reno-Sparks area. The Tahoe City dam, originally built in 1870, raises the natural lake by several feet.

Lake Tahoe Dam. Source: U.S. Bureau of Reclamation

A grandiose plan to tunnel Tahoe water through the Sierra Nevada to San Francisco surfaced in the 1860s but failed because it appealed “more to the imagination than the pocketbook,” according to Donald J. Pisani, an American West historian at the University of Oklahoma.

By contrast, the plan outlined in the new study would reserve for water supply not just a few feet of Tahoe’s depth, but nearly the entire volume of lake, which stretches 22 miles north-south and is the second deepest lake in the United States at 1,645 feet.

“The lake contains about 122 million acre-feet of water, almost twice the average annual runoff of snowmelt and stormwater from all of California,” Von Schmidt said. In comparison, Shasta Lake — California’s largest reservoir — can hold only 4.5 million acre-feet.

Economic analysis by the study team showed that the tunnel drilling would unearth enough Sierra gold to more than pay for the cost of the project, estimated at $35 billion.

“This truly is a golden opportunity,” said Rico Louie, lab director at the Reber Foundation. “It’s a win-win-win-win-win…situation.”

The project, dubbed “Tahoe to Tap”, would triple California’s surface storage and generate hundreds of construction jobs, said Calvin Hobbes, a modeler at the UC Davis Center for Watershed Sciences who examined the plan.

Though Hobbes cautioned “more research is needed,” news of the study went viral on social media within minutes of its online posting this morning.

The study triggered alarms among Nevada officials who claimed California had no legal right to appropriate the water.

Joe Goodman, editor of Virginia City’s Territorial Enterprise, fired off an editorial assailing California for “attempting once again to rob Nevada of its wealth.”

“They took the gold and silver from our hills,” Goodman fumed, “but the pure water that comes to us from Lake Tahoe, that makes glad our waste places, is God’s exhaustless gift, and the hand of humankind cannot deprive us of it.”

California’s chief water visionary William Mulholland said Lake Tahoe has enough water for both states and that California would use Tahoe water only in dry years in months when runoff from the western slope proved insufficient.

“Just because it’s there, doesn’t mean we’ll take it,” Mulholland said in a prepared statement. “California does, however, have a superior claim to Tahoe water since two-thirds of the lake and its outlet are within its border.”

Source: League to Save Lake Tahoe

Representatives with the League to Save Lake Tahoe said the plan has them rethinking their successful “Keep Tahoe Blue” campaign.

“It appears the threat is no longer just the diminishing of Tahoe’s water clarity but the diminishing of the lake itself,” said Trupp McCarthy, a spokesman for the group. “Perhaps we should clip our bumper stickers to simply read, ‘Keep Tahoe.’”

Nestle J. Frobish, former chairman of the Worldwide Fair Play for Frogs Committee, is curator of the Center for Watershed Sciences at UC Davis.