LAKE TAHOE — Lake Tahoe dropped below its natural rim this week for the first time in five years as a result of a three-year dry spell.
“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,” said Bill Hauck, Truckee Meadows Water Authority senior water supply coordinator.
On Tuesday, the lake hit 6,222.93 feet before getting a boost to 6,223.05 due to this week's rainstorms. It was October 2004 the last time the lake dipped below its natural rim, which sits at 6,223 feet.
Local hydrologists expect that storms this week will help the lake's level — but not significantly.
“One single storm is not going to bring it up dramatically because the soil conditions are so dry and it's a short-duration storm,” said Chad Blanchard, chief hydrologist with the U.S. District Court Water Masters Office in Reno. “But anything that will help, we'll take it.”
The lake is forecasted to rise about a tenth of a foot due to the storm, Blanchard said. A tenth of a foot of water in Lake Tahoe is equivalent to about 12,000 acre feet or enough water to fill a third of Boca Reservoir.
“The amount of water that comes into Lake Tahoe can be significant but the impact will be minimal because the surface area is so large,” Blanchard said. “You can get a huge amount of water and it will barely raise it.”
The lowest the lake's level has been is 6,220 feet in 1992 the highest level was in 1907 at 6,231 feet, according to TMWA 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 TMWA records.
TMWA research shows it takes roughly two or three years of non-drought precipitation on average to refill the lake after a drought period.
When Tahoe falls below its natural rim, it limits the amount of water flowing into the Truckee River, Blanchard said. As a result, the water master's office must release reserves from reservoirs like Boca to keep up the required flow of water.
However, demand for water decreases this time of year because most of the agricultural water-needs have lessened, and people are watering their laws less, Hauck said.
Both agencies are keeping an eye on this winter's precipitation.
“This winter for us and the Truckee River is going to be key in shaping the water supply outlook for next summer,” Hauck said.