DID YOU KNOW?
by Shawna Anderson
Spring 2005

Watershed Awareness

Did you know that May is Watershed Awareness Month? Are you familiar with the San Dieguito River Watershed? The San Dieguito watershed is 434 square miles in size, and while it is large, what occurs 55 miles upstream has an effect on the quality of water downstream, which eventually reaches the ocean. The headwaters are located on Volcan Mountain in the Witch Creek basin in East San Diego County. As the drainage travels southwest from Volcan Mountain into Sutherland Reservoir, through the Pamo and Boden basins and into the San Pasqual Valley, it flows primarily through undeveloped and agricultural lands. Past Lake Hodges the watershed becomes progressively more urbanized, until it broadens as the San Dieguito Lagoon and finally discharges into the Pacific Ocean at Del Mar. Thanks to preservation efforts, almost 70 percent of the San Dieguito watershed is undeveloped or in agricultural use.

A primary influence on the quality of any watershed is the amount of impervious surfaces – ground or covered areas into which rainfall cannot effectively infiltrate. These include roads, buildings, parking lots, sidewalks, driveways, and other hard surfaces. Impervious surfaces collect pollutants, which are washed into the aquatic system via storm drains. This occurs during storms in the rainy months but even during dry seasons, pollutants are washed into storm drains from irrigation overspray, leaking water pipes, hosing sidewalks or parking lots, and other ways. Unlike the sewer system, which carries water from indoor drains and underground pipes to water treatment plants, the storm drain system releases water into the nearest water body and eventually to the ocean without any filtering or treatment. For example, one storm drain located at the end of San Andreas Drive in the vicinity of the San Dieguito Lagoon discharges urban runoff from a 300-acre upstream area. Oils, fertilizers, pet wastes, and other pollutants end up in the river.

Almost 70 million pounds of pesticides are applied to urban lawns in the U.S. each year, averaging 5 to 7 pounds of pesticides per acre, according to the EPA and the Center for Watershed Protection. Agricultural uses can also impact the quality of our watershed if not controlled and buffered from natural riparian areas. Runoff from nearby agriculture can contain pesticides, herbicides, and fertilizers. Another common pollutant to our drainages occurs when drainage channels or exposed soils are scoured by fast moving stormwater. When construction sites do not utilize barriers (such as fiber rolls) and stockpile covers, large quantities of sediment erode off the site into the storm drain.   Stormwater carries sediment and causes siltation of our natural waterways damaging plants and animals. Eggs and larva can become buried in silt and young plants can suffocate.  

Public awareness about the causes and effects of urban runoff is increasing thanks to public campaigns such as “I Love a Clean San Diego” and the City of San Diego’s “Think Blue” program. Some cities have adopted new regulations that require filtering systems in new urban development projects. However, as our watersheds continue to urbanize, the amount of urban runoff increases and the quality of our riverine systems continue to decrease.

During Watershed Awareness Month, please be mindful of the runoff that flows from your property into the storm drain and:

• Conserve water. Don't over water your lawn. Maintain your irrigation system, repair leaks, and adjust sprinklers if water runs into the gutter. Water during cooler times of the day.
• Keep your gutters swept clear of dirt, leaves and grass cuttings.
• Identify pests before spraying pesticides. Ask a specialist at your garden center for advice on how to treat for that specific pest, and use non-chemical pesticides whenever possible.
• Only buy pesticides you need in amounts you will use.
• Use pesticides and fertilizers sparingly and never apply to your lawn or garden if the weather calls for rain.
• Create healthy soil by adding compost that contains organic matter and nutrients.
• Use drought resistant native plants that conserve water, which reduces runoff. Use mulch instead of herbicides to prevent weeds from growing and to help absorb water.
• Pick up trash and litter around your yard.
• Sweep up dirt and debris instead of using a hose.
• If you wash your own car, use a shutoff nozzle on your hose to reduce runoff. Consider pulling your car up onto the lawn to avoid runoff to the storm drain OR take your car to a car wash that recycles water.
• Shop for non-hazardous household cleaning products.
• If you use water based paints, rinse paint brushes in the sink. For oil based paints, filter and reuse paint thinner. Dispose of thinner through a household hazardous waste program in your area.
• Keep trashcans closed to prevent animals from scattering trash.
• If you use hazardous substances such as paints, solvents and cleaners, use them sparingly, according to the directions. Store properly to avoid spilling.
• If you're working on a home improvement project, dispose of drywall, concrete and mortar in the trash. Don't rinse concrete or mortar into the street.
• Participate in local recycling programs. To find out more about recycling in your area call (800) 237-2583.

More information about San Diego County watersheds is at www.projectcleanwater.org

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