California Code, Public Resources Code - PRC § 5527

The government of each district shall be vested in a board of five or seven directors, one from each of the wards or subdistricts, together with the other officers mentioned in this article. Directors shall be residents and electors of the wards or subdistricts from which they are nominated. Directors who are elected at any election which is held after October 1, 1965, shall be elected by ward or subdistrict and the qualified electors in any ward or subdistrict may only vote at a district election at which a director is to be elected to represent such ward or subdistrict and may only vote for one of the persons who is nominated for such office.