Lake Tahoe is the clearest it has been in 10 years, said U.C. Davis researchers last week.

The lake's clarity is measured by lowering a white, frisbee-sized disk into the water and noting the depth at which the disk disappears from sight. In 2002, the disk could be seen to a depth of 78 feet for the first time since 1992.

Efforts to restore the lake's clarity are thanks to a $900 million program and cooperation between developers and environmentalists.