The Stemple Creek watershed begins just west of Petaluma and empties into the Pacific Ocean through the Estero de San Antonio, draining 50 square miles. The watershed is characterized by grassy, rolling hills that are used extensively for agriculture. The drainage is cut almost exactly in half by the Sonoma-Marin county line. The watershed changes sharply from Highway 1 west. Slopes increase in steepness, and coastal scrub and dense stands of native perennial grasses take over the hills. The Estero de San Antonio, a small coastal lagoon, is part of the Gulf of the Farallones National Marine Sanctuary and is also included in the Central California Coast Biosphere Reserve (UNESCO Man and Biosphere Program). A sandbar often closes the mouth of the Estero in the summer or early fall. It remains closed until winter rains with heavy runoff break open the sandbar.
Learn more about the history and habitat of the Stemple Creek watershed.