What’s a Watershed?

A watershed is a land area that drains water into a stream, lake, wetland, bay or estuary, and an area that percolates into groundwater. Watersheds come in different shapes and sizes. Local watersheds are parts of larger, regional basins. The Santa Clara Basin, for example, is a sub-basin of the larger San Francisco Bay Basin. 

A watershed begins at the top of a hill or mountain ridge and is ultimately defined by gravity. The Santa Clara Basin is bounded by the Diablo Mountains to the east and the Santa Cruz Mountains to the south and west. South San Francisco Bay receives water from six major watersheds.

For more information about watersheds, including an interactive history map, visit Valley Water's watershed site.

Which Watershed are you located in?

Storm drains collect runoff from both overflowing irrigation water and rain from streets and parking lots that flows to an underground storm drain system. There are approximately 35,000 inlets in the City of San José, and each flow to a creek or river, which then flows to the San Francisco Bay.

Find out which watershed you live in and where your inlets flow by viewing the maps linked below. You can also read the stencil on the sidewalk above or beside the inlet near your home or business that says “NO DUMPING”, the name of the waterbody that the inlet drains to, and the stormwater hotline phone number, (408) 945-3000. Residents or visitors can call this hotline or use this complaint form to report illegal dumping if they have witnessed anything other than rain water entering an inlet or its surrounding area.

• All Watersheds in San José
• Baylands Watershed: Inlets at the northern tip of the City will be marked as Flows to Bay.
• Calabazas Watershed: Inlets will be marked as Flows to Bay.
• Coyote Watershed: Inlets will be marked as one of three subwatersheds:
  
  • Flows to Coyote Creek
  • Flows to Silver Creek
  • Flows to Thompson Creek
• Guadalupe Watershed: Inlets will be marked as one of four subwatersheds:
  
  • Flows to Guadalupe River
  • Flows to Los Gatos Creek
  • Flows to Canoas Creek
  • Flows to Alamitos Creek
• Lower Penitencia Watershed: Inlets will be marked as Flows to Penitencia Creek
• San Tomas Aquino Watershed: Inlets will be marked as Flows to San Tomas Aquino Creek.

Storm Drains on Private Property

If the inlets on your private property (not in the public right-of-way) are in need of stenciling with “NO DUMPING” messages, the Watershed Protection Division of the Environmental Services Department will provide you with stencils and instructions at no charge (property owners purchase paint). To obtain the stencils, please call (408) 945-3000 and be prepared to provide the following information:

• Contact Information
  
  • Name
  • Phone number
  • Either the company name for commercial or industrial property or the complex name (multi-family housing)
• Site information
  
  • Name of site (e.g., name of shopping center or store, condo complex, industrial company)
  • Address
  • Nearest cross street
  • Number of inlets to be stenciled

Daily Activities Can Impact Our Watershed

Common pollutants such as litter, oil, soap, paint, copper, nickel, mercury, and pesticides can degrade or impair water quality in our local creeks and rivers. Less commonly recognized pollutants, such as leaves or landscape clippings, can reduce the amount of oxygen available in the creeks. This makes it difficult for wildlife, such as fish, to live. Even soil and sediment can impair water quality, both by degrading spawning habitats for fish in the creeks and by carrying pollutants such as copper, nickel and other heavy metals that readily bind to sediment. 

These pollutants, individually and cumulatively, adversely affect the wildlife that live in and depend on the City’s rivers and creeks and the San Francisco Bay.

Tips to protect our watersheds

• If you see litter, pick it up and put it in a trash can. Keep residential garbage and recycling carts tightly covered to prevent overflow. Instead of overfilling carts, purchase an extra garbage sticker to label a garbage bag.
• Use a commercial car wash or wash cars on a lawn or dirt surface.
• Rake leaves and put them out on the curb the day before your yard waste is collected (avoid doing so when rain is expected or order an optional yard trimmings cart). For proper raking instructions, click here.
• Sweep dirt into landscaping to prevent it from entering storm drains.
• Compost yard waste or practice sustainable landscaping. For free landscaping workshops including virtual opportunities, visit South Bay Green Gardens.
• Check out more tips on water pollution prevention here and at MyWatershedWatch.org.

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