The Science of Sustainability

Rumors and Truth in Lake Tahoe

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Lake Tahoe may hold mysteries. Photo: Santappa.

A few weeks ago, scuba divers in Lake Tahoe found the body of a man who had drowned in the lake 17 years ago. Still in its wetsuit, the body was very well preserved. Because the water in this high alpine lake is so cold, decomposition is very slow. This fact has spawned rumors, the most famous of which involves Jacques Cousteau and still makes me shudder, years after I first heard it. Apparently, years ago, Cousteau went scuba diving in Lake Tahoe. He emerged from the water shaken, but not with cold. He said, “The world is not ready for what I have seen.”

What did Cousteau see? Maybe the bodies of unlucky gamblers who crossed the Mafia in 1950s Reno. Or maybe it was Tahoe Tessie, the Loch Ness likeness of the lake. But, in its coverage of the recent discovery, the LA Times said that Cousteau never actually visited Lake Tahoe. The Cousteau story may be a myth, but it is no less chilling, because the physical conditions of the lake are such that bodies could still be drifting beneath the surface.

At 1645 feet (depending on the level of water in the basin), Lake Tahoe is the second deepest lake in the US. (Crater Lake in Oregon is the deepest in the country. The world record goes to Russia’s Lake Baikal, which is some 5,369 feet deep.) Lake Tahoe is located between two fault zones, and it formed through a tectonic combo of uplift and subsidence. The Sierra Nevada mountains rose up on the west and the Carson Range rose up on the east. The rock underneath the lake sank down to form a flat-bottomed basin called a graben. The word is German for “grave” and refers to the lake’s low-lying nature—and perhaps also to whatever Cousteau purportedly saw underwater.

Lake Tahoe is cold. The temperature at the surface of the lake varies, from a low of about 40 degrees in February or March to a high of about 75 degrees towards the end of the summer. Below the surface, the temperature is a chilly 39 degrees. In the winter, when the surface and the deep waters are relatively close in temperature, the wind blowing across the surface of the lake mixes the water. This brings oxygen from the surface layer down to the depths, and nutrients from the depths up to the surface.

In 2010, the mixing occurred from the surface down to about 550 feet, because the surface of the lake remained relatively warm throughout the winter. In previous years, mixing has occurred down to about 1500 feet. Since the 1970s, the surface layer of the lake has gotten warmer in the summer, and it retains that heat throughout the winter. Just like in the ocean, stratification—a warm surface layer that is distinct from the cold bottom layer—means it is hard to get the surface and deep waters to mix.

Lake Tahoe is famous for its clear waters. But, as UC Davis’s recently released Tahoe: State of the Lake Report explains, the lake is not as clear as it used to be. In the 1960s, you could see down to a depth of about 100 feet, but now you can see down to only about 70 feet. The lake has become cloudier because nutrients enter the lake via 63 rivers and streams, and those nutrients fuel the growth of algae. And, global warming plays a role: the warm surface of the lake gives a particular species of microalgae a competitive advantage, and the tiny bodies of the microalgae cloud the water.

The clarity of the lake, and its invasive species, will be on the agenda today at the Lake Tahoe Environmental Summit. Nevada Senator Harry Reid and California Senator Dianne Feinstein will both be at the Homewood Resort, discussing Lake Tahoe’s economic and ecological challenges.

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Category: Biology, Climate, Environment, Geology

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Jennifer Skene

About the Author ()

Jennifer Skene develops curriculum on climate change and ocean sciences at the Lawrence Hall of Science and teaches biology and science communication at Mills College and the University of California Berkeley. She has a degree in biology from Brown University and a Ph.D. in Integrative Biology from UC Berkeley. She started working with QUEST in 2008 as an intern. She has written for the Berkeley Science Review and the UC Museum of Paleontology’s Understanding Evolution and Understanding Science websites.
  • Kim Vincent

    interesting article Jen!

  • http://scubadiverinfo.com Conrad Blickenstorfer

    Couple of things:

    Graben doesn't mean grave in German. Grab does, but Graben simply means ditch or gulf or gully or whatever else can be carved out, depending on the context.

    Tahoe does get cold under the surface, but in the summer, even at 100 feet or so, it's still around 50 degrees.

    And yes, I can tell from my own diving experience that it's not as clear as it used to be. There's often a greenish algae bloom near the surface that robs the lake of its former clarity.

    As for Cousteau, I haven't read anywhere that he was diving Tahoe. If he did, for the most part there isn't much to see in Tahoe.

  • Jennifer Skene

    Thanks for your comments, Conrad. I've never been diving in Lake Tahoe (too cold!) so I appreciate your perspective!

  • Matt

    I like the article however a critical point was left out;

    Article- "The lake has become cloudier because nutrients enter the lake via 63 rivers and streams, and those nutrients fuel the growth of algae."

    Nutrients have always naturally entered the lake from its streams, albeit at a much lower level. The problem now, and cause for cloudiness is that elevated nutrients are being flushed into the lake from road construction and erosion, fertilizers from landscaped lawns and golf courses, urban pollution, and other unnatural sources. These and other sources of human caused nutrient elevation and runoff into the lake need to be addressed and minimized.

  • ExResident 20+ Yrs

    Jacques Cousteau did venture to the bottom of the lake, he communicated back over the radio that he wanted the authorities awaiting his return, after the tapes were reviewed with sheriff's officers in the trailer, he stepped out to the awaiting public and stated "The world is not ready to see the bottom of Lake Tahoe". Later at dinner he was asked why he would not show the tapes to the public, his reply was "I have children".

    • Boboe

      Wrong. Cousteau NEVER visited Tahoe.

  • ExResident 20+ Yrs

    The lake has become cloudy due to the construction of the Tahoe Keys, which rerouted the upper Truckee river around marsh land that acted as a natural filter for the primary water inlet, the result beyond cloudy water was the sand bar that stretches all the way to Ski Run Blvd that eventually lead to the end of Ski Run Marina water access.

  • Human Observer

    I doubt the explorer thought finding some old dead gangsters would shatter the world. I also doubt the discovery of an unknown sea creature would freak him out, I mean this is what he spent his life doing. If the story and quote is true, i would have to lean towards something a little more out there.

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  • Stephanie Hillers

    "Graben" as a noun=ditch, "graben" as a verb=to dig, neither one means grave, as stated in the article. "Grab" is German for grave, close but doesn't mean the same.