Where did you hear "10 feet a day"?? If that were true you could drive a boat all the way back to the bay area.....no trailer required. Late in the summer I've heard it draw down as much as one foot a day, but that's alot. See the attached link. Right now it's not quite at a foot/day.
Ohhh sorry, yea, anchor buddy.
http://cdec.water.ca.gov/cgi-progs/queryDaily?SHA