Clarity is determined by measuring the water depth at which an 8-inch diameter white disk disappears from view. The Lake owes it extraordinary natural clarity mainly to its exceptional depth and volume, a relatively small watershed and favorable climatological conditions. In 2013, clarity averaged 70.1 feet, far less than the maximum 105 feet of clarity measured in 1968. In the last 10 years, the rate of loss of clarity has decreased due to environmental improvements in the watershed.
Fact credit: TahoeFacts.com