http://www.usbr.gov/newsroom/newsrel...RecordID=27761
http://californiafarmer.com/story.aspx?s=21958&c=9
I don't know where the 90 percent comes from Beck used either. It could be he got it from the above Bureau of Reclamation: Central Valley Project where it says 10% or 15% water for Ag. depending on run off and precipitation might be, etc., etc.,...
I don't know where the total percentage comes from it doesn't really explain the numbers in specificity; (municipal and industrial is based on historical deliveries) so I would guess Ag is similar to them too. I don't know?
The second link is from the spring numbers and it had Ag possibly getting zero water and these numbers/percentages seem based on some kind of compact/contract between states and a watershed agreement they have with companies.