Firefighters headed to 321 First St. at about 9:40 a.m. in response to a report of a female in the creek.
The firefighters and a public works employee found the 29-year-old woman in the water near where the Petaluma River joins the creek, Battalion Chief Russ Rassmussen said.
The woman, who was in a motorized wheelchair, apparently fell off an embankment behind the apartment building shortly after 9:30 a.m., Rassmussen said.
The woman's roommate spotted her and called 911, and was trying to help the woman when firefighters arrived, Rassmussen said.
She was removed from the water, placed on a backboard and turned over to an ambulance crew who took her to Petaluma Valley Hospital. Her injuries did not appear to be life-threatening, he said.