Cal. Pub. Util. Code § 90972.5

In the event that no unincorporated territory shall have been included in the original formation of the district, an election shall be held concurrent with the first annexation election of unincorporated territory for the purpose of selecting one board member for the district in the event the annexation is successful. The initial member elected to represent the unincorporated territory on the board of directors shall serve until a successor is elected at the next succeeding election of directors within the unincorporated territory and qualifies.