California Code, Water Code - WAT § 30734

(a) The board shall promptly by resolution divide the district into five divisions as nearly equal in acreage as practicable and assign a number to each division.

(b) The board shall, not less than 85 days prior to the general district election next after the election approving the election of directors from divisions, by resolution designate the division from which directors shall be elected at that election to succeed directors whose terms then expire.  Directors shall be elected from the remaining divisions at the general district election next following that election.

(c) The board may, at any time after initially dividing the district into divisions but not less than 85 days before a general district election, by resolution change the boundaries of the divisions to keep them as nearly as equal in size as practicable.