Lake Tahoe approaches natural rim; Truckee River flow slows

TAHOE CITY, Calif. - As Lake Tahoe's water level drops to less than a foot from its natural rim the Truckee River is getting lower and slower with it.

Water stops flowing through Tahoe's dam into the Truckee River when the lake drops below its natural rim (6,223 feet in elevation) - an event that may occur this fall unless precipitation picks up, said Dave Wathen, hydrologist for the Water Master's Office in Reno.

Tahoe is currently .93 feet above the natural rim, at 6,223.93 feet.

"For the last three years we were hovering right above the rim, but this year we're probably going to hit the rim," Wathen said.

As of Wednesday, 200 cubic feet per second was flowing through the dam, and that rate is decreasing by five to 10 cubic feet per second each day, Wathen said.

This year, early-summer storms helped, Wathen said, but now the wind associated with the unusual summer weather is accelerating evaporation on Tahoe, he said.

"It takes a lot of water to fill Tahoe; we'll need a pretty major winter to get out of this hole we're in," Wathen said. "If it's another average or less-than-average winter, the chances of running low during the high demand season are much increased."

Truckee River operators open and close dams to maintain a minimum flow of 500 cubic feet per second measured in Floriston, called the Floriston rate.

This year, Wathen said the Truckee isn't in danger of dipping below that rate until late fall, although operators are relying on other reservoirs earlier than normal.

"Now we are relying on daily changes at Prosser Reservoir, and we'll start supplementing more with Boca," Wathen said. "When we run out we won't be able to make the Floriston rate, which we expect to happen in the end of October or early November."

Bill Hauck of the Truckee Meadows Water Authority said he's also hoping for a good winter, but said the authority will have enough water to get the Truckee Meadows area into the next wet season.

"If I had a crystal ball I'd like to say we'll have at least an average year - that's all I'm hoping for," Hauck said.

Things aren't bad enough, however, to dip into Donner Lake for drought supplies, he said.

"It's pretty much a typical year for this time of year on Donner Lake," Hauck said. "Sometime in the fall we'll start making releases - we have to have two gates open by mid-November for flood control."

He said the authority never has had to use Donner Lake for emergency drought supplies.