LOCATION: Nevada-California border 20 miles southeast of Reno, Nev.
NAME: Tahoe means ''Big Water'' in Washoe Indian Tribe dialect.
SIZE: 21.6 miles long and 12.2 miles wide, 193 square mile surface.
ALTITUDE: 6,225 feet above sea level.
AVERAGE DEPTH: 989 feet.
DEEPEST POINT: 1,636 feet.
VOLUME: 39 trillion gallons of water - enough to cover the entire state of California with 14.5 inches of water.
THREATS: Logging, housing development, traffic, air and water pollution, soil erosion, wood smoke, golf course fertilizer, algae growth.
CLARITY: A white dinner plate used to measure Tahoe's clarity was visible at depths of 105 feet in the 1960s. The same plate is visible only as deep as 66 feet today and would be visible only as deep as 40 feet by the year 2030 if the decline goes unchecked.
POPULATION: From 1960 to 1980, permanent resident population increased from 10,000 to 50,000 and summer population increased from 10,000 to 90,000. Five million people live within four hours' drive.
Source: U.S. Department of Interior's U.S. Geological Society, Tahoe Regional Planning Agency and Lake Tahoe Watershed Assessment.