Cal. Pub. Util. Code § 22902

If the revenues of the district are inadequate to pay the interest or principal of the bonded indebtedness of the district as it becomes due, or to pay any other expenses of or claims against the district, the board of directors shall transmit to the board of supervisors and the county auditor a written estimate of the minimum amount of money required for the payment of the principal and interest of the bonded indebtedness as it becomes due, and of the minimum amount of money required by the district for any other purpose.