The governing body of every municipality issuing bonds under the authority of this chapter, before the delivery thereof, shall levy by recorded resolution or ordinance a direct, annual tax which, together with any other moneys provided by, or sources of revenue authorized by, the legislative assembly, shall be sufficient in amount to pay, and for the express purpose of paying, the interest on such bonds as it falls due, and also to pay and discharge the principal thereof at maturity. The municipality shall be and continue without power to repeal such levy or levies or to obstruct the collection of any such tax until such payments have been made or provided for, except that if the governing body in any year makes an irrevocable appropriation to the sinking fund of moneys actually on hand, or if there is on hand in the sinking fund an amount that would be sufficient to retire the bonds, the governing body shall cause its recording officer to certify the fact and amount to the county auditor with the direction that the county auditor should reduce by the amount so certified the amount otherwise to be included in the tax rolls next thereafter prepared. A copy of such resolution or ordinance must be certified to and filed with the county auditor, and after the issuance of such bonds, any such tax on property from year to year must be carried into the tax roll of the municipality and collected as other property taxes are collected. No further annual levy for that purpose is necessary. The governing body may, in its discretion and in anticipation of the sale of bonds, at any time after the issuance of bonds has been authorized by the electors or by resolution of the governing body when no election is required, levy and certify to the county auditor for collection a portion of the tax herein required, which must be credited against the amount otherwise required to be levied after the bonds have been sold. Any other tax or source of revenue authorized by the legislative assembly for such purposes and imposed or pledged by the municipality for those purposes is likewise irrepealable and subject to the same conditions and limitations as any taxes levied on property for the same purposes. Any annual or periodic amounts provided for the municipality issuing such bonds by the legislative assembly out of state funds for paying the interest and principal of such bonds constitute an irrepealable and continuing appropriation until the liability for all interest and principal payments of the bonds have been satisfied. When insufficient funds are available to pay the matured bonds, the county auditor shall notify the governing body of such municipality of such deficiency and the governing body thereupon may levy a direct tax on the taxable property to pay said deficiency and interest thereon. If the governing body of the issuing municipality no longer exists, the county auditor shall levy a direct tax against the taxable property in the original issuing municipality to pay said deficiency and the interest thereon. The manner of levy, certification, and collection of said tax must be the same as provided by this section for the levy, certification, and collection of taxes by this section. When such bonds are further sustained by revenue of a revenue-producing utility, industry, or enterprise, said resolution or ordinance may provide that the tax to be levied and assessed may be reduced by such amount and under such conditions as must be determined in said resolution or ordinance so long as adequate provision is always made for the payment of such bonds and interest thereon.