The bonds are special obligations of the local agency and shall be a charge against and are secured by a lien upon and shall be payable, as to the principal thereof and interest thereon, and any premiums upon the redemption thereof, from the revenues and such funds as are described in the resolution authorizing the issuance of the bonds. If funds and revenues described in the authorizing resolution are insufficient for the payment of interest and principal on the bonds, the local agency, at its discretion, may make such payments from any other funds or revenues that may be legally applied to their payment.