Clarity of lake is 66 feet |

Clarity of lake is 66 feet

Lake Tahoe’s clarity in 1998 was worse than almost any other year in recent history, the University of California, Davis announced Thursday.

The depth of clarity was 66 feet, the second-worst year since UC Davis started frequent and long-term measurements in the mid-1960s.

In 1997, the average depth of clarity was about 64 feet.

“You can’t get too excited one way or the other when you’re looking at it year to year,” said Bob Richards, researcher for the UC Davis Tahoe Research Group. “You just have to put it in line with all the other measurements and see how it lines up with all the other readings. You have to look at the long term.”

While year-to-year measurements often vary significantly, the long-term trend has shown Lake Tahoe’s clarity decline at a rate of more than 1 foot a year. Increased algal growth and the presence of sediment in the water have led to the decline in clarity.

“Tahoe is a system that reacts slowly, and it’s taken a longtime to see the lost clarity,” Richards said. “It’s also going to take a longtime to get it back. People are going to have to be patient with the measures that are being taken. It’s not going to be a quick fix.”

The transparency measurements are made from UC Davis’s research vessel the John Le Conte. Officials lower a secchi disc, which resembles a white dinner plate, into the water. Poor viewing conditions related to wave height or cloud cover are eliminated, and about 35 measurements comprise the average annual transparency.

The visibility into Lake Tahoe was more than 100 feet when UC Davis started its measurements about 30 years ago.

“I’ve taken a majority of the readings, and, of course, I have noticed it has changed quite a bit,” Richards said. “There are definitely fewer and fewer days each year when I’m able to see very clearly.”

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