The board of supervisors of the county shall annually, at the time and in the manner of levying other county taxes, levy and cause to be collected a tax upon the taxable real property in the district, based upon the last equalized assessment roll of the county sufficient to pay the interest on the bonds for that year and such portion of the principal as is to become due before the time for making the next general tax levy.
Ca. Health and Saf. Code § 4811