FAQ's about Stormwater and Pollution

What is a watershed?

Many think a watershed is a shed that is used for water storage -- but it’s not.  A watershed is an area of land that drains down to the lowest point. The water moves through a system of drainage pathways, both underground and on the surface. These pathways flow into streams and rivers, which become larger as the water moves downstream, eventually reaching a lake or ocean. The Lake Tahoe Watershed includes every drop of water or precipitation from the tops of our mountains to streams, including rainfall that hits our roofs and runs down our driveways  --  all eventually ending up in Lake Tahoe. We live, work and play in one big watershed. It’s our job to take care of it.

What is stormwater?

Stormwater is water from rain or melting snow that runs across the land instead of seeping into the ground. In Tahoe, this runoff goes over the surface of our driveways, streets and gutters collecting pollutants and eventually ending up in the lake. Because runoff is not treated in any way, it’s important to have a good storm drainage system in place that helps filter out or treat as many pollutants as possible before entering the Lake.

Why is having an effective stormwater drainage system in place important?

Storm drain systems are designed to direct stormwater to its appropriate location so it doesn’t pool or pond where it isn’t wanted.  The system(s) Caltrans is placing for Lake Tahoe not only directs stormwater runoff to the Lake, but it also incorporates a filtration system. This system mimics the natural land treatment and ultimately protects the environment from pollution by eliminating as many pollutants as possible prior to reaching the Lake. This will help keep Lake Tahoe cleaner and blue for decades to come.

What kind of pollution will be filtered out by the new storm drain system?

There are many kinds of pollutants that end up in the Lake. They include visible trash – like cigarette butts and litter, as well as things that are not as easily seen such as sediment, animal waste, pesticides and automobile fluids. The new system will help reduce these and other pollutants. We can all help by cleaning up after pets and properly maintaining vehicles. Check for fluid drips from antifreeze, brake fluid and used motor oil which end up on driveways and roadways then get washed into the Lake by rain and snowmelt.  If you use pesticides or fertilizers in your yard, please follow the directions on the label for proper application  -- or better yet, use less toxic alternatives. For more information on stormwater programs in your county visit: 

Placer County Stormwater Quality Program 
Town of Truckee Keep Truckee Green

Lake Tahoe’s Clarity

Fine sediment particles and erosion affect Lake Tahoe’s clarity. Most of the fine sediment particles that end up in the lake are from urban areas (i.e. road dust, wood burning). These fine particles end up in the streams or air, and eventually make their way to the lake. Stream channel erosion also plays a role in clouding the water. Failing stream banks and eroding stream beds add to the pollutants that make their way to Lake Tahoe. Water clarity can increase by many feet in just a few years when these things are reduced. This is why Caltrans is working hard to help keep Tahoe blue.