California Code, Water Code - WAT § 30733

(a) The board shall promptly by resolution divide the district into five divisions as nearly equal in population 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 by division, by resolution designate which divisions shall elect directors at that election to succeed the directors whose terms then expire. The remaining divisions shall elect directors at the general district election next following that election.

(c) Notwithstanding any other provision of law, subdivision (d) applies to districts in which directors are elected by divisions.

(d) The board of directors shall, by resolution, adjust the boundaries of any divisions pursuant to Chapter 8 (commencing with Section 22000) of Division 21 of the Elections Code.