Tahoe Science Logbook: What a wet winter means for Lake Tahoe | TahoeDailyTribune.com

Tahoe Science Logbook: What a wet winter means for Lake Tahoe

UC Davis Tahoe Environmental Research Center

The National Weather Service reports that since Oct. 1, over 140 billion gallons of water have flowed into Lake Tahoe.

With a wet winter in Lake Tahoe and the lake level rapidly rising, many people are excited that the drought in the West is over.

But, is this true? It may be, but what is more important to recognize is that we are witnessing what scientists have been saying for many years, that our new normal is one that has extremes. These will likely include extreme dry periods and extreme wet periods — more extreme than the historical record to date.

So, how full is Lake Tahoe? As of mid-March, the surface of Lake Tahoe sits 3.84 feet above its natural rim, a mere 2.26 feet below its maximum legal limit (at 6,226.84 feet). The National Weather Service reports that since Oct. 1, over 140 billion gallons of water have flowed into the lake. With more winter weather likely and a large snowpack yet to melt, this amount will surely increase.

Historically, similar very large increases in lake surface elevation have happened in the past. For instance after the prolonged drought from 1987 to 1994 there was a dramatic increase in lake level from 6,221 ft. to 6,227 feet in 1995. During a very wet year in 2006 the lake rose 5 feet from 6,224 feet to 6,229 feet.

Historically, similar very large increases in lake surface elevation have happened in the past. For instance after the prolonged drought from 1987 to 1994 there was a dramatic increase in lake level from 6,221 ft. to 6,227 feet in 1995. During a very wet year in 2006 the lake rose 5 feet from 6,224 feet to 6,229 feet.

What does a big water year for Lake Tahoe mean this year? Lake clarity may decrease due to the large amounts of runoff. The melting snow will likely overwhelm the infrastructure built to capture and treat the fine sediment and nutrients that stormwater carries with it. The associated nutrient inputs may also lead to increased levels of attached algae (periphyton) along the shoreline during summer.

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The streams will be flowing much higher than the past several years and likely for a prolonged period in the spring and summer. We will see much smaller beaches as the water level has climbed its way up the shore. And the Truckee River will once again be flowing at the outlet this summer!

Will the surface water of Lake Tahoe be colder this year because of the snow? Probably not. Even in an extremely wet year, the additional water represents less than one-half percent of the total lake volume, with much of it flowing down to great depths to join water of the same temperature and density. Rather, the surface water temperature will be largely dictated by our summer weather, and the recent trend has been for lake warming.

So there's a mix of positive and negative impacts associated with a big water year at Tahoe. That's the natural pattern for the lake. We can enjoy the variety of conditions that Tahoe presents each year — this contributes to our region being such an amazing place to visit or live near.

Come discover the UC Davis Tahoe Science Center (www.tahoesciencecenter.com). Uncover the Tahoe Basin's ecological challenges through 3-D movies and interactive exhibits. Family friendly fun for kids ages 8 and up. Drop-in tours are Tuesday through Friday from 1-5 p.m. For school groups, we offer inquiry-based field trips. Check out our monthly lecture series on various scientific topics. To learn more about the Tahoe Science Center and TERC, visit tahoe.ucdavis.edu. The scnience center is located at 291 Country Club Drive Incline Village, Nevada. Call us at 775-881-7566.

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