The provisions of this subchapter shall not apply to bonds, notes, certificates, or other evidence of indebtedness issued by a regional water distribution district organized under § 14-116-101 et seq., or to any drainage district, levee district, or other improvement or special assessment district organized with the consent of the owners of land affected thereby under the laws of the state heretofore or hereafter adopted, notwithstanding that the district may pledge revenues from its operations or other sources in addition to, or in lieu of, a pledge of assessed benefits or interest thereon to secure payment of the indebtedness.