Water clarity in Lake Tahoe reached a record low annual average in 2017 due to a historic drought, record-breaking precipitation and warmer than usual lake temperatures, according to a new study.
The average annual clarity level for 2017 clocked in at 59.7 feet — a roughly 9.5 foot decrease from 2016 — and surpassed the previous recorded low of 64.1 feet in 1997, according to a report released by the Tahoe Environmental Research Center 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,” said Geoffrey Schladow, the research center director.
Media: Brandpoint The Tahoe Basin recorded roughly 300 percent of its normal precipitation, which was bolstered by an early winter storm in November 2017.
California was nearing the end of its worst drought in roughly 1,200 years in 2017 and recorded heavy rains.
Those rising temperatures coupled with unusually low wind speeds in July and August caused warm water temperatures to last through September, which is later than normal for Lake Tahoe.
The water clarity report suggests that warming lake temperatures help in holding sediment particles to the surface of the water for a longer period of time, causing a drop in clarity.
“It’s important to continue to make those smart investments for the long-term health of the lake and its environment.” Researchers with the Tahoe Environmental Research Center have been using water sensors, NASA buoys and manually collecting samples to help better understand under-examined areas of the lake during different weather conditions.
Clarity analyses efforts were funded through the Tahoe Regional Planning Agency and UC Davis.
Lauren Hernandez is a San Francisco Chronicle staff writer.