Climate change disrupting natural cycles at drier Lake Tahoe

TAHOE CITY, Calif. (AP) — Drought fueled by climate change has dropped Lake Tahoe below its natural rim and halted flows into the Truckee River, an historically cyclical event that’s occurring sooner and more often than it used to — raising fears about what might be in store for the famed alpine lake.

Scientists are concerned that the growing frequency of low-water extremes may become the new normal.

They point to seasonal shifts in weather patterns causing precipitation that historically falls as snow to arrive in the form of rain atop the Sierra along the California-Nevada state line.

“Our summers are lasting longer. Springs are coming sooner,” said Gregory Schladow, a water resource and environmental engineering professor who is the founding director of the UC Davis Tahoe Environmental Research Center.

“The water level has always gone up and down,” he said this week. “It’s always occasionally gone below the rim. But the frequency of the changes is increasing.”

Over the past century, the amount of precipitation falling as snow has declined from 52% in 1910 to 33% in 2020 and is projected to drop below 20% by the end of the century, according to experts at the research center in Incline Village, Nevada.

Rain runs off the mountains instead of pilling up as snow on mountaintops for safe storage until it is most needed in late spring and summer — the high Sierra equivalent of somebody leaving the freezer door open at the top of the refrigerator.

Since summer, boat ramps have been closed. Docks sit precariously above the receding lake’s dry bottom. Boat and kayaking rentals have fallen, and river rafting operations on the Truckee River had to end early.

“Our season was short, and we fear there may not be one next summer,” said Toni Rudnick of the Truckee River Raft Company.

“It all depends on the snowpack,” she said. “In 2015, didn’t open at all when the Truckee River was a series of puddles … In 2016, we had a 15-day season.”

The U.S. Forest Service canceled this month’s annual kokanee salmon festival at South Lake Tahoe because low water levels have all but cut off their migration route to spawn in Taylor Creek.

Deborah Grant Hanna is no scientist, but she’s witnessed decades of ups and downs in water levels during 42 years at the lake. She manages the Gatekeeper Museum/Gift Store next to the dam in Tahoe City where the dry lake bed now extends 200 yards (183 meters) off the normal shoreline.

“The water usually gets the lowest in mid-November. It was lower than now in 2015-16,” she said. “The problem with the rain now is it goes away from the mountain and causes flooding rather than storing snowpack. And as far as the local economy goes, the rain falls on the snow at the ski resorts.”

The lake dropped below the natural rim at an elevation of 6,223 feet (1,897 meters) twice in the 1920s after the dam was completed in 1913 and created the capacity to store…