California Code, Streets and Highways Code - SHC § 8221

Annually at the time of levying county taxes, the board of supervisors shall levy a tax upon the real property within the district.The rate shall be such as will produce, after due allowance for delinquency, the amount determined as necessary to be raised by taxation on the secured roll. The tax rate so levied shall apply to the real property within the district as it appears on the assessment roll of the county.