Data shows sharp decline in 2017 Lake Tahoe clarity brought on by years of drought then record snow
Submitted by editor on Wed, 06/13/2018 - 1:02pm
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, according to data released Wednesday 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.”
California Natural Resources Secretary John Laird and Nevada Director of Conservation and Natural Resources Bradley Cowell issued a statement on a report indicating Lake Tahoe’s clarity decreased to a record-low annual average in 2017. Go here for a joint letter to the Tahoe Science Advisory Council from Secretary Laird and Director Crowell.
The report highlights the combination of historic drought and one of the wettest winters on record as key factors contributing to low lake clarity last year.
“According to the latest data, one of the most iconic indicators of Lake Tahoe’s health — lake clarity — registered its lowest recorded annual level in 2017. While annual clarity declines are not unusual, the record decline experienced last year warrants an in-depth review to further understand the causes and impacts, and to help ensure the 2017 decrease is an anomaly, and not a trend.
“After 20 years of significant investment to protect the clarity of Lake Tahoe, we take this development seriously. As the natural resources leads for our states, we are asking the science community to take a fresh look at factors affecting lake clarity and recommend actions to continue our success in protecting the ecological health of Lake Tahoe in a time of changing climate.”
