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Lake Tahoe's diminishing water level impacting flow of Truckee River

By Annie Flanzraich and Greyson Howard
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LAKE TAHOE — After a few days of flirting with its natural rim, Lake Tahoe's water level has stayed below the mark since last week.

On Wednesday, Oct. 28, according to the U.S. Geological Survey, the lake dropped to 6222.95 feet and has stayed at about that level since Tuesday afternoon.

“Unfortunately we are where we were back before the storm,” said Chad Blanchard, chief hydrologist with the US District Court Water Masters Office, of the recent October storm that dropped as much as 5 inches of rain in the area.

It marks the second time the water level has fallen below 6,223 feet in almost five years.

“We have three consecutive below-average winters — you could argue we are in a drought cycle right now, but we are definitely in a dry spell,” Bill Hauck, Truckee Meadows Water Authority senior water supply coordinator, told the Sun the last time the water level fell on Oct. 13.

Truckee River implications
This means things are pretty lean on the Truckee River, Blanchard said.

For agricultural and residential needs, water authorities try to maintain a rate of between 500 and 300 cubic feet per second flowing through Floriston on the Truckee River, depending on the time of year, known as the Floriston Rate.

As of Tuesday, only 95 cubic feet per second flowed through Floriston, Blanchard said, up from 71 on Monday with the addition of some Tahoe Meadows Water Authority water from Boca Reservoir.

“We're down to flood control water in Prosser, and Stampede is all fish water,” Blanchard said. Flood control means the reservoir's only ability now is to take in more water in case of a flood event, and fish water refers to water designated to help the Lahontan Cutthroat Trout, so neither can contribute to the Floriston Rate flow.

The good news, Blanchard said, is this time of year, agricultural irrigation is pretty much done, and residential demand has dropped without people watering lawns as much with water from the Truckee, meaning the low flow doesn't put Reno-Sparks area users in peril.

“All we can do is wait for storms, for precipitation. It would be good to get a little rain first to get water in the reservoirs before snow,” Blanchard said.

If there is another dry winter, however, the Truckee could drop below the Floriston Rate again (after things presumably pick up in the spring) before peak demand drops off next summer, potentially meaning drought restrictions, Blanchard said.

Low levels
The last time Lake Tahoe dipped below its natural rim, which sits at 6,223 feet, before this year was January 2005.

The lowest the lake's level has been is 6,220 feet in 1992, and the highest it has been was in 1907 at 6,231 feet, according to Tahoe Meadows Water Authority records.

The second-worst drought in Tahoe's recorded history lasted from 1928 to 1935, and wasn't topped until the drought of 1987 to 1994.

After the drought ended in mid-1995, Tahoe saw its most dramatic rise, going from 6,221 feet in Oct. 1994 to almost 6,227 in July on 1995, according to Tahoe Meadows Water Authority records.

Tahoe Meadows research shows it takes roughly two or three years of non-drought precipitation on average to refill the lake after a drought period.

Blanchard said it wouldn't be unprecedented for a major winter to be able to re-fill Tahoe, but it's very unlikely.