Water Code § 56030

The governing body of a county drainage district is a board of directors of not less than five members.

If the district does not include a city or cities or any part thereof, the board of supervisors of the county is the board of directors of the district. If the district includes a city or cities or any part thereof, the members of the board of directors shall be as follows:

(a) The presiding officer of the governing body of each city is a member of the board of directors;

(b) The chairman of the board of supervisors is a member of the board of directors;

(c) A member of the governing body of each city included within the district, other than the presiding officer, as appointed by the governing body of the city is a member of the board of directors;

(d) Two members of the board of supervisors, other than the chairman of the board of supervisors, as appointed by the board of supervisors are members of the board of directors.