Cal. Water Code § 40306

The term of office of each director elected after the formation election shall be four years, and until his or her successor is elected and has qualified. Upon the district receiving actual written notice that a director or the entity the director represents no longer is a holder of title within the district or that the holder of title the director represents is withdrawing the director’s authorization, a vacancy shall be deemed to occur, but the director shall continue to serve until his or her successor is elected or appointed and qualified.