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 isn’t visible to the naked eye. The depth at which the disk disappears determines the recorded level of clarity. The measurement was first taken 1968, with a recorded clarity of just over 100 feet deep. Since 1968, the Lake’s clarity has slowly declined. The record low of 64 feet was recorded in 1997 (a flood year) and 72.4 feet in 2005. Though the recent steady 70+ foot clarities are encouraging, but scientists also caution that there is still a lot of work to be done to regain and retain the 100-foot level of clarity.
HOW CAN I KEEP TAHOE BLUE?
Multiple factors contribute to the loss of clarity in the Lake. A few, like floods, tectonic movement and storms are beyond human control. Most, however, are the direct result of human impact on the environment, including urban and road development.
To help return Lake Tahoe to its original water purity, visitors can follow these simple guidelines:
Hike only on existing trails.
Avoid fertilizers and lawn chemicals.
Water carefully and avoid runoff. Yard chemicals and fertilizers can wash into ditches and storm drains. Avoiding lawn and garden chemicals is the best approach.
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.
Clean up after pets.
Wash cars at a commercial car wash that filters and recycles wash and rinse water.
Don’t ride mountain bikes on muddy dirt roads or trails. Don’t ride across streams. Instead, use bridges, 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!