Cal. Health & Safety Code § 6592

In the case of a district board elected by election divisions, the district board shall adjust the boundaries of the election divisions before November 1 of the year following the year in which each decennial federal census is taken. If at any time between each decennial federal census a change of organization alters the population of the district or the district increases or decreases the number of members of the district board, the district board shall reexamine the boundaries of its election divisions. If the district board finds that the population of any election division has varied so that the divisions no longer meet the criteria specified in subdivision (c) of Section 6591, the district board shall adjust the boundaries of the election divisions so that the divisions shall be as nearly equal in population as possible. The district board shall make this change within 60 days of the effective date of the change of organization or an increase or decrease in the number of members of the district board.