(1) The principal of and interest on the bonds shall be payable from: Revenues derived from the waterworks facilities and/or wastewater facilities projects acquired, constructed, reconstructed, equipped, extended, or improved, in whole or in part, with the proceeds of the bonds;
(2) Obligations of: The owners of waterworks facilities and/or wastewater facilities projects; or
(3) Any person with whom the proceeds of the bonds, or a portion thereof, are invested by contract or otherwise;
(4) Any other funds or sources of funds of the board specifically pledged and which are set aside as a special fund or source, other than taxes or assessments for local improvements, for the purpose of paying the principal of and interest on the bonds; or
(5) Any combination of subdivisions (a)(1)-(3) of this section.
(6) The board is authorized to pledge those revenues, obligations, and other special funds or sources to pay the principal of and interest on the bonds.