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Your Stemple Creek Watershed

DO YOU KNOW WHERE YOUR STORM DRAINS FLOW?

The Stemple Creek watershed drains a total of 50 square miles of Sonoma and Marin counties (26-square miles in Marin). The Sonoma-Marin County line cuts the Stemple Creek watershed almost exactly in half. It begins west of Petaluma and empties into the Pacific Ocean through the Estero de San Antonio. Estero de San Antonio is a small coastal lagoon that’s part of the Gulf of the Farallones National Marine Sanctuary and the Central California Coast Biosphere Reserve.

The land draining into Stemple Creek is largely grassland with rolling hills for agriculture. Willows have been re-established along parts of the main creek and tributary streams. Coastal oak woodland can still be found along some of the higher tributaries. Eucalyptus, once planted in rows for windbreaks and fuel, are now one of the most common trees in the watershed.

Stemple Creek winds its way through the Sonoma County communities of Two Rock and Fallon and the land use in the watershed is almost exclusively agricultural with 90% of the watershed is used for livestock grazing. Once it enters Marin the creek flows west winding its way between Tomales Petaluma Road to the south and Fallon Two Rock Road to the north with a tributary flowing in from the south that runs alongside the north end of Chileno Valley Road. Just after crossing under Hwy 1 Stemple Creek joins tributaries from the north that form Estero de San Antonio. The Marin County portion of the watershed contains mostly beef and sheep ranches, as well as some dairies. Sonoma County Agricultural Preservation and Open Space District and Marin Agricultural Land Trust are both active in the watershed, protecting agricultural land use through conservation easements.

Although the Estero de San Antonio is part of the Gulf of the Farallones National Marine Sanctuary, the land surrounding it is all privately owned. A sandbar often closes the mouth of the Estero in the summer or early fall. The Estero remains closed until winter rains with heavy runoff break open the sandbar. Since access across private land is by permission only, recreational uses are limited.

Stemple Creek was a marginal Coho salmon and Steelhead trout stream, until the early 1960s when a small dam built on the Button Ranch closed off the last available spawning areas. Resident accounts also tell of dense flocks of waterfowl. However, as in most areas along the Pacific Flyway, waterfowl numbers have dropped. Farm ponds, especially those with shallow edges, now provide some of the best remaining habitat for waterfowl, northwestern pond turtles, and other aquatic species.

California Department of Fish and Wildlife has identified the Estero de San Antonio and Estero Americano as among the most significant habitat areas in the State. They contain a remarkable mosaic of intermingling habitat types including densely wooded riparian ravines, saltgrass areas, mudflats, eelgrass beds, and small freshwater ponds. The area between the two Esteros contains extensive areas of native coastal terrace prairie.

Special-status species in the watershed include California freshwater shrimp, Northwestern pond turtle, Tidewater goby, Myrtle’s silverspot butterfly, and California red-legged frog. The Estero is used by over 40 species of waterfowl and is an important winter feeding area for migrating birds. Golden eagles are known to nest in the upper watershed. River otters have been observed in the Marin County portion of Stemple Creek east of Highway 1. Eelgrass beds in the Estero de San Antonio provide nursery habitat for Dungeness crabs.

Remember, storm drains connect streets to creeks. Simple changes can make a big impact. Stemple Creek Watershed is Ours to Protect.

LEARN BEST PRACTICES FOR PROTECTING OUR CREEKS AND RIVERS HERE >

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