PRC §5790.15: (a) After incurring a general obligation indebtedness, and annually thereafter until the indebtedness is paid or until there is a sum in the district treasury in a special bond service fund set apart

(a) After incurring a general obligation indebtedness, and annually thereafter until the indebtedness is paid or until there is a sum in the district treasury in a special bond service fund set apart for that purpose that is sufficient to meet all payments of principal and interest on that indebtedness as it becomes due, the board of directors shall adopt a resolution directing the county tax collector to levy a tax on behalf of the district. (b) The tax shall be in addition to all other taxes levied by and for the district and shall be collected in the same manner and at the same time as county taxes. A county may recover its costs as provided in Section 29142 of the Government Code. (c) The rate of the tax shall be fixed to result in proceeds that are sufficient to pay any principal and interest that will become due before the next proceeds of a tax to be levied will be available.