Sonoma Creek is a stream in Northern California. It is one of two principal drainages of Southern Sonoma County, California, with headwaters rising in the rugged hills of Sugarloaf Ridge State Park and discharge to San Pablo Bay, the northern arm of San Francisco Bay. The watershed drained by Sonoma Creek is roughly equivalent to the wine region of Sonoma Valley, an area of about 170 square miles (435 square kilometers). The State of California has designated the Sonoma Creek watershed as a ?Critical Coastal Water Resource?.[2] To the east of this generally rectangular watershed is the Napa River watershed, and to the west are the Petaluma River and Tolay Creek watersheds.