Water Code § 50601
CHAPTER 1. Selection, Tenure and Compensation
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.