The creek runs from the southeast to the northwest, originating near Orinda and flowing into San Pablo Bay. It drains one of the largest watersheds in the East Bay, comprising some . The creek has 34 named tributaries. The creek was dammed in 1919, forming the San Pablo Reservoir. Briones Reservoir, constructed in 1964, dams the Bear Creek tributary. San Pablo Reservoir essentially splits the creek in two, with about half of the creek and its related feeder creeks on either side of the artificial lake; for much of its course, it runs parallel to Wildcat Creek, which drains from Wildcat Canyon, the next valley to the west. The East Bay Municipal Utility District (EBMUD) gets less than 10% of its water from the creek.