Lake Tahoe falls to alarmingly low level

This week, a historically dry period in California will come to bear at Lake Tahoe, where the water level is expected to sink below the basin’s natural rim. That’s the point at which the lake pours into its only outflow, the Truckee River.

It’s not a crisis, researchers and conservationists say, but it marks another extreme swing for Tahoe amid historic drought, wildfires and erratic weather, all intertwined with climate change and becoming more prominent aspects of the alpine environment.

“Going below the natural rim won’t change much in the lake itself. But there’s very little positive about low lake levels once they get below the rim,” said Geoffrey Schladow, director of the Tahoe Environmental Research Center at UC Davis.

Tahoe’s natural rim rests at 6,223 feet in elevation. A dam on the Truckee River allows the lake to fill about 6 feet higher, to 6,229.1 feet, according to the U.S. Geological Survey.

The water level has fallen below the rim four times since 2004, most recently in the fall of 2016, the height of California’s historic drought. However, that tense period was followed by a banner winter for precipitation in the Tahoe area, in 2017, which replenished the Sierra snowpack and brought the lake to its highest heights in decades.

The water level has mostly been falling since the summer of 2019, when it was near the lake’s limit, and is currently about 1½ inches above the rim. The plunge is due primarily to meager snowpack in the mountains ringing the lake as well as evaporation, which sucks about 3 feet of depth off the lake each year, according to Tahoe water authorities.

This time, researchers and environmental nonprofits keeping watch of the lake aren’t optimistic about the water coming back as quickly as it did in 2017.

“If we have another dry winter, it could become a bigger concern,” Schladow said.

Tahoe has been steadily receding all year, and the plunging water level is changing the character of its shoreline.

The Truckee River, Tahoe’s only outflow, has slowed to a trickle. Private piers across the North Shore are high and dry. Boat ramps plunge straight into bare earth. Entire coves on the East Shore, popular with kayakers, have dried up. The South Shore has become one giant sandbar. Beaches in shallower areas have grown by hundreds of feet, exposing parts of the lake people aren’t used to seeing and revealing stinking deposits of rotting algae.

“You can’t get within 150 yards of the normal shoreline” in South Lake Tahoe, said Kelsey Weist, owner of Clearly Tahoe, which runs clear-bottom kayak tours around the lake.

The brunt of the impact so far has been felt by boating and tourism companies who have had to get creative about getting their customers on the water. Marinas are dredging more deeply to retain access for boaters.

Weist, who runs tours year-round, has adapted by overhauling her routes. A popular one that led paddlers along the Upper Truckee Marsh — typically a great place to spot wildlife — had to be canceled in early July, Weist said.

“We don’t foresee this being the last time we have this challenge,” Weist said. “With global warming, we know we’re never going to be able to anticipate a normal season again.”

The lakebed is exposed at Kings Beach on Sunday - the water level is so low at Lake Tahoe that it in danger of becoming stagnant.

The lakebed is exposed at Kings Beach on Sunday — the water level is so low at Lake Tahoe that it in danger of becoming stagnant.

Max Whittaker/San Francisco Chronicle

Upper Truckee Marsh marks the spot where Tahoe’s largest inflow, the Upper Truckee, reaches the lake. It’s key habitat for kokanee salmon, which would normally be running upriver this time of year by the hundreds to spawn. But on Friday, under the afternoon sun, Jesse Patterson looked into the water there and counted only two. Nearby, piles of dead algae decayed on the beach.

“It’s crazy low,” said Patterson, chief strategy officer for the League to Save Lake Tahoe, a conservation and cleanup nonprofit. “The concern is what it looks like if this continues for multiple years in a row.”

Beyond cosmetics, there’s potential for environmental effects.

Climate change has warmed the lake, which has in turn given rise to algal blooms that have, in recent years, mucked up its famous clarity. The warmer the lake gets, the less likely it is to “turn over,” a periodic mixing phenomenon that helps keep the aquatic ecosystem balanced and healthy.

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