Climate ChangeClimate change is one of the biggest threats facing Lake Tahoe. It is increasing the lake’s water temperature and affecting regional weather patterns in ways that could change the lake’s ecosystem and cause more of a decline in the lake’s clarity.
Warmer water provides a more hospitable environment to algae and invasive species. On average at the surface, Lake Tahoe's water is almost 1.5 to 2 degrees Fahrenheit warmer than it was 44 years ago, according to UC Davis researchers.
Average atmospheric temperatures at Tahoe have risen more than two degrees and spring snowmelt occurs a week earlier than in the 1950s, according to studies by the Scripps Institute of Oceanography in San Diego and the U.S. Geological Survey.
More Rain, Less SnowIn the coming decades, UC-Davis scientists predict more rain and less snow will fall in Tahoe, and there will be more flood-causing storms where rain falls on snow. This phenomenon has already been documented throughout the West, according to Nature.
Streams and rivers will flow with greater intensity during these rainstorms, causing more fine sediment to flow into the lake. Property owners at Tahoe can help minimize the effects of these storms by installing mandated erosion and runoff control measures.
Lake mixingScientists with the Tahoe Environmental Research Center have identified one particularly concerning outcome from the warming trend.
"What we expect is that deep mixing of Lake Tahoe's water layers will become less frequent, even non-existent, depleting the bottom waters of oxygen. This will result in major, permanent disruption to the entire lake food web," researcher Geoffrey Schladow told Science Daily in 2008.
"This is not unheard of," he told the publication. "Anoxia (oxygen depletion) occurs annually in most lakes and reservoirs in California in the summer. But Tahoe has always been special. It's been above and beyond such things.
"A permanently stratified Lake Tahoe becomes just like any other lake or pond. It is no longer this unique, effervescent jewel, the finest example of nature's grandeur."
Currently, the cold water at the bottom of the lake (below 100-150 meters) typically mixes with the surface water about an average of once every four years.
As the surface water continues to increase in temperature, the extent and frequency of deep mixing could change. In as little as a decade, the lake may no longer experience deep mixing.
Without the mixing, oxygen would become depleted in the deep water, creating an uninhabitable environment for a number of aquatic species, including recreational fish species. In addition, without any oxygen near the bottom of the lake, the plant material that sinks from the surface would not undergo typical bacterial breakdown. Consequently, the bottom of the lake would become nutrient-laden and phosphorus-rich.
Schladow told the Science Daily that when the oxygen is gone, phosphorus that is currently locked up in the lake-floor sediments will get released. This phosphorus will eventually reach the lake's surface, where it will fuel algae growth. Algae blooms can cause many problems, including reduced lake clarity, unpleasant odors and bad-tasting drinking water.