Water Clarity

Lake Tahoe is one of the clearest bodies of water in the world, due to its significant depth, low watershed rate and granite composition. The clarity is measured according to the Secchi depth test, where a solid white disk the size of a dinner plate is lowered into the water until it can no longer be seen by the naked eye. The depth at which the disk disappears is the recorded level of clarity. In 1968, when this measurement was first taken, the clarity was recorded as just over 100 feet deep. Since then, the clarity has slowly declined, to a record low of 64 feet in 1997 (a flood year) and 72.4 feet in 2005. Currently, scientists are encouraged by the steady 70+ foot clarities over the past five years, but they acknowledge that there is still much work to be done to regain and retain the 100-foot level of clarity.

What Can YOU Do?

Several factors contribute to a loss of clarity in the Lake. Some, such as floods, tectonic movement and storms are beyond human control. Most, however, are due specifically to human impact on the environment, including urban and road development. In order to help return Lake Tahoe to its original water purity, follow these simple guidelines.

  • Hike only on existing trails.
  • Use fertilizers and lawn chemicals sparingly.
  • Water carefully and avoid runoff. Yard chemicals and fertilizers can wash into ditches and storm drains. Use lawn and garden chemicals carefully, according to their labels, to avoid excess or unneeded application.
  • Use phosphate-free laundry detergent.
  • Take household hazardous wastes to the fire department or an appropriate recycler.
  • Recycle used automotive oil. Never dump oil, paint, antifreeze or other chemicals into a storm drain or ditch. Oil dumped on the ground or in the street can pollute groundwater, streams and the Lake.
  • Don’t litter.
  • Clean up after pets.
  • Wash cars at a commercial car wash that filters and recycles wash & rinse water.
  • Don’t ride mountain bikes on muddy dirt roads or trails. Don’t ride across streams. Use bridges instead, or walk your bike across.
  • Never pour any chemicals down storm drains.
  • Don’t use two-stroke engines for boating. Properly service engines and motors in vehicles and watercraft.
  • Report water polluters
  • Ride a bike!

Additional Resources:

EPA involvement in preservation of Lake Tahoe
Clarity report from U.S. Water News Online
Tahoe-Baikal Institute Programs and Exchanges