Changing climate impacted Lake Tahoe's clarity again in 2016

Clarity levels at Lake Tahoe in 2016 increased in winter and decreased in summer in 2016 according to a report released on May 17 by researchers from University of California, Davis.

They said the summer values were due to the continuing effects of climate change and were so large that they outweighed the improving winter clarity which were at their highest since 2012.

In 2016 the average clarity level was a 69.2 feet according to data from the UC Davis Tahoe Environmental Research Center (TERC) and the Tahoe Regional Planning Agency (TRPA). That was a decrease of 3.9 feet from the previous year. Even though a decrease this is still more than 5 feet greater than the lowest recorded level in 1997 when it was 64.1 feet.

The decline was the second year in a row the clarity of Lake Tahoe was impacted, but the reasons each year were different. In 2015 the drop in clarity was due to warmer layers of water near the lake's surface, while in 2016 the clarity was reduced by an early spring. The warmer and drier weather that spring brought caused growth of light-blocking blooms of very small algal cells.

“Lake managers and researchers must continue to work together to better understand the impacts that continued climate change will have at Lake Tahoe, and look for new solutions to mitigate those impacts as we work to restore lake clarity,” said Dr. Geoffrey Schladow, director of the University of California, Davis, Tahoe Environmental Research Center. “Lake Tahoe has an international reputation for collaboration between science and policymakers and in light of these new threats, it’s more important than ever to continue that collaboration.”

Winter clarity of Lake Tahoe continues to increase. From December 2015 through March 2016 it increased by 11.7 feet. The winter average of 83.3 feet was the highest, or clearest, recorded since 2012.

Summer clarity of Lake Tahoe from June through September 2016 fell to 56.4 feet, a 16.7-foot decline over the preceding year. Data indicate that the decline was caused by large increases of Cyclotella, a small diatom.

Schladow will be presenting his annual "State of the Lake" report on July 27 at the TERC center in Incline Village, NV from 5:30 p.m. to 7:00 p.m. For more information on the event: http://terc.ucdavis.edu/events/ and the report: https://www.ucdavis.edu/news/climate-and-ecology-linked-lake-tahoe-clarity-decline-2016.