Cal. Water Code § 74750

The treasury of the principal county is the repository of all the funds of a district. For this purpose, the treasurers of any other counties wherein is situated a portion of the district, shall, at any time, not more often than twice a year, upon the order of the board, settle with the board and pay over to the treasurer of the principal county all moneys in their possession belonging to the district. The treasurer of the principal county shall receive and receipt for such moneys, and place such moneys to the credit of the district. He shall be responsible upon his official bond for the safekeeping and disbursement, in the manner provided in this division, of these and all moneys of the district held by him.