Snowmelt not enough to chill Tahoe
May 28, 2017
The more snow melting into Lake Tahoe the colder the water will be this summer, right? Wrong.
Though it might seem logical that the large amount of snow melting into the lake would affect its temperature, according to Geoff Schladow, director at UC Davis Tahoe Environmental Research Center, that isn't the case.
"Even in the really wet winter that we had, less than 1 percent of the water in the lake changes because of all this rain and snow," explained Schladow. "Most of that water has been there for hundreds of years."
As of Friday, the lake level was more than 5 feet above its natural rim, putting the total amount of water in the lake at almost 40 trillion gallons, according to U.S. Water Master Chad Blanchard.
To put that in perspective, the Tahoe Fund calculated that it's enough water to cover the state of California to a depth of roughly 14.5 inches.
Further, due to the higher density of the snowmelt, it plunges down to the bottom of the lake, which has a maximum depth of 1,645 feet.
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"It may change the temperature of the bottom of the lake, but the surface of the lake that all of us swim in and experience, like when I fall off the paddleboard, has little to do with the snowmelt itself," said Schladow.
What does affect water temperature in Lake Tahoe each summer is weather.
Right now the temperature of the surface water is hovering between 50 and 55 degrees, according to data collected by four NASA buoys moored around Lake Tahoe collecting real-time measurements. But after a warm summer, the surface water can warm to 65 to 75 degrees in August and September.
"If it ended up being a windy, cloud-free summer that would translate into cooler surface temperatures," said Schladow, explaining that wind contributes to evaporation, which cools the water, while clouds tend to keep the surface warm.
At the very bottom of the lake, the water temperature fluctuates up and down — a pattern that resembles a "sawtooth" when documented on a graph, said Schladow — due to warming from the geothermal heat of the earth then subsequent lake mixing to Tahoe's depths every few years, diluting the warmer water.
Though the lake won't necessarily be any cooler for swimmers this summer, the risk of cold-water shock is still something of concern for officials who are responsible for keeping Lake Tahoe's waters safe.
"It's probably 10-15 [cases of cold water shock] a year that we directly respond to, but I'm sure there are more that we don't see because the sheriff handles it before we get there," said Casey Rude, petty officer with the U.S. Coast Guard Station in Lake Tahoe.
Lake Tahoe's chilly waters can quite literally take your breath away.
"This response is an uncontrollable gasp for air followed by a prolonged period of rapid breathing. Taking a couple gasps of air underwater is all it takes to drown," explained Cate Neal, a registered nurse and Trauma Program Coordinator at Barton Memorial Hospital.
Last June, 20-year-old Marc Ma, a University of Nevada, Reno football player, was presumed dead when his paddleboard was found adrift after he and several teammates encountered strong winds off Lake Tahoe's west shore. The search was eventually called off, and his body has still not been recovered. Ma, who was a surfer and trained swimmer, was not wearing a life jacket.
There are a number of ways to prevent cold water shock and drowning in Lake Tahoe. Neal recommends easing into the water, giving your body time to adjust to the cooler temperature. If paddling, wear a life jacket in case you fall in. And most importantly, don't swim alone.