Why do Watersheds Matter?

Pillar Point Marsh in Fitzgerald Marine Reserve


What we do on land affects the water that sustains all life within San Mateo County. We all live in a watershed, or an area of land that stormwater flows through or across on its way to a larger body of water. These watersheds carry everything that enters the storm drains--including rain, litter, used oil, and even dog poop--directly into our local creeks, the San Francisco Bay, or the Pacific Ocean without being filtered or cleaned. Since we all live in and share our watersheds, it is important to know a thing or two about how they work and what we can do to protect them!


In San Mateo County, we have 34 watersheds that are each home to various habitats that sustain plant, animal, and human life. Depending on which side of the Santa Cruz Mountains you live on, your watershed will eventually carry stormwater down to its final destination at the Pacific Ocean or the San Francisco Bay.


On the bayside, many watersheds discharge to the San Francisco Bay, with the larger ones draining into San Mateo Creek, Colma Creek, and San Francisquito Creek. These bayside watersheds host a variety of unique ecosystems that play an important role in filtering out pollutants from reaching the Bay, reducing flooding, and providing a home to endangered species like the San Francisco Garter Snake and the California Red-Legged Frog. Unfortunately, our bayside watersheds are increasingly threatened by urbanization which has led to increased runoff and pollutants. San Francisquito Creek, which supports Steelhead Trout that swim upstream to mate, is now listed by State regulatory agencies as an impaired watershed due to extreme degradation of the fish habitat. Moreover, San Mateo Creek was also designated as an impaired watershed for the presence of diazinon, a harmful pesticide that was used heavily by golf courses and has since been banned. As a result of these challenges, our program has partnered with residents and home improvement stores to promote education about many watershed-friendly topics, including the harmful impacts of pesticides and tips for proper use and disposal of garden chemicals.


On the west, San Mateo County’s Pacific coastline is one of the nation’s last remaining accessible, rural coastlines near a major metropolitan area. Scientists have designated the area a biodiversity hotspot, or an area that is rich in native plant and animal life, yet it remains impacted by urban development. Some of the major watersheds that lead to the Pacific Ocean include those draining to San Pedro Creek, Pilarcitos Creek, San Gregorio Creek, and Pescadero-Butano Creeks. Protected areas such as the Fitzgerald Marine Reserve have ensured San Mateo County can maintain the delicate balance of some of the most prized tide pools in the state and home to a variety of aquatic life including sea urchins, starfish, harbor seals, and red octopi. Denniston Creek runs through the Reserve and drains to Pacific Ocean, supporting Pillar Point Marsh, which is one of the last remaining salt marshes in the area and provides nesting and feeding areas for many animals.


Knowing and protecting our watersheds is how we can preserve the incredible diversity of life in our small but beautiful San Mateo County. By taking daily steps to prevent pollutants from entering into our storm drains and then flowing into creeks, the Bay, or ocean, you can help to ensure that our watersheds remain a healthy home for all of us!


Want to know more about what you can do to protect our San Mateo County watersheds?  Click here for more information or visit Oakland Museum’s watershed finders: (1) Upper Peninsula Watershed Finder and (2) Lower Peninsula Watershed Finder.

By Megan Kang