California Code, Public Resources Code - PRC § 9521

(a) Except as provided in subdivision (b), the treasury of the principal county is the depository of all of the funds of the district.

(b) As an alternative to using the county treasury as depository, a district may adopt a resolution transferring responsibility for the district treasury to the board of directors of the district, which shall deposit district funds as provided in Article 2 (commencing with Section 53630) of Chapter 4 of Part 1 of Division 2 of Title 5 of the Government Code.  Following adoption of the resolution, the provisions of this article relating to the county treasurer and county treasury shall not apply to the district.