RENO, Nev. (AP) - The clarity of Lake Tahoe worsened a bit last year but scientists say in the big picture it's still positive news about a decade-long trend of stabilization in the azure mountain waters.
The UC Davis Lake Tahoe Environmental Research Center's annual clarity report showed average clarity in 2013 at about 70 feet, a 5-foot decrease from 2012.
Clarity is measured by the depth at which a 10-inch white disk lowered into the lake remains visible from the surface. Measurements began in 1968, when the disk could be seen to depths of 102 feet.
Tahoe's worst year for clarity was in 1997 at 64 feet. Scientists say the trend has been one of general improvement since then due in large part to efforts to control erosion and runoff into the lake
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