While for much of its course Watsonville Slough appears to be little more than a drainage ditch, it is in fact the backbone of the system that drains the rest of the sloughs. It includes several important wetlands at its upper reaches. From its origin along Ramsay park in Watsonville, Watsonville Slough passes under Main Street and harkins Slough Road and thence under Highway One, Lee Road, and San Andreas Road. It is pumped into the lower, tidal reaches at Shell Road and flows under Beach Road to join the Pajaro River at Monterey Bay. It can be viewed as a ditch paralleling Beach Road to the ocean, and as a tidal slough as it widens at Palm Beach.