The researchers use what’s called a sekki disk to measure the clarity.
“It’s a 10-inch, white plate or disk that is lowered into the water until it disappears,” Heather Segale, with the UC Davis Tahoe Environmental Research Center told KCBS.
This year, Segale says “we can see down 73 feet on average.” That figure is nearly five feet less than when the clarity was measured last year.
Segale said the decline is in part because of the relatively low snow-to-rain ratio of last year’s runoff.
“Because that water came in warmer, the fine particles that come in flowed closer to the surface, where they impacted the clarity, instead of plunging deep,” Segale said.
Lake Tahoe’s clarity is impacted by a number of factors according to Segale.
“When we’re driving around the lake, we are grinding up the soil, and dirt and rocks on the roads, just like a mortar and pestle,” Segale said.
UC Davis researchers have been measuring the clarity of the water in Lake Tahoe for 50 years.
By measuring the lake’s clarity, the researchers are helping local planners gauge the success of efforts to reduce storm water runoff, and erosion impacts.
“It also helps protect the lake from being invaded by invasive species,” Segale said.