The guy began by
explaining that a watershed is defined as the area where percipitation
(rain and snow that falls there) drains into the same creek. San
Francisco has several different watersheds.
All of the water that falls on the west
side of the ridge flows to the same treatment plant, but there are two
different creeks draining the bay side. The watershed that drains down
Cesar Chavez is the Precita Creek one.