The by-laws of a district may provide, or be amended to provide, for a board of five or seven members, and, if the original by-laws so provide, five or seven eligible persons respectively shall be elected as trustees at each election, or, if the by-laws are amended, then five or seven eligible persons shall be elected at the next district election held subsequent to the date of amendment, and at each election held thereafter.
Ca. Water Code § 50601