The Petaluma River Watershed is located in southern Sonoma County, and a portion of northeastern Marin County, Northern California. It encompasses a 146 square mile, pear-shaped basin. The watershed is 19 miles long and 13 miles wide.
56% of the watershed is mountainous, 33% is a valley, and 11% are salt marshes.
The Petaluma River Watershed includes Black John Slough, Basalt Creek, Rush Creek, Adobe Creek, Lichau Creek, Willow Brook, Lynch Creek, and San Antonio Creek.
The Petaluma Watershed Enhancement Plan includes: