Historic drought followed by record-breaking precipitation and warm lake temperatures converged to produce the lowest annual average clarity levels recorded at Lake Tahoe in 2017, indicates data released by the Tahoe Environmental Research Center at the University of California, Davis.
The average annual clarity level for 2017 was 59.7 feet. This was a 9.5-foot decrease from the previous year, surpassing the previous lowest value of 64.1 feet in 1997. Mid-lake clarity levels can swing widely from season to season and year to year, and the five-year average lake clarity is approximately 70 feet.
“In 2017, Lake Tahoe’s low clarity was primarily the result of two extreme climatic and hydrologic events — a perfect storm, so to speak,” said TERC Director Geoffrey Schladow, a professor of engineering at UC Davis. “The combination of arguably the most extreme drought period ending with the most extreme precipitation year produced the low clarity values seen. Measurements for 2018 have already shown a large improvement that are more in line with the long-term trend.”