CA Pub Res Code Section 5783.5

In the case of a district that contains unincorporated territory and the territory of one or more cities:

(a)

The board of directors may be elected or appointed by the county board of supervisors and the city councils in which the district is located. If the board of directors is to be appointed, the board of supervisors and the city council or councils shall appoint directors according to the proportionate share of population of that portion of the county and each city within the district, provided that the board of supervisors and each city council shall appoint at least one director. The board of supervisors or city council may appoint one or more of its members to the district board.

(b)

Notwithstanding subdivision (a), the county board of supervisors may appoint itself as the board of directors, if the city council of each of the cities consents by resolution.