Any municipality, at the option of its governing body, may provide for the payment by general taxation of all the taxable property in the municipality of not more than one-fifth of the cost of any improvement financed by the levying of special assessments other than the opening and widening of streets or the laying of sewer or water connections from the main to the curb line. Any amount which the municipality shall determine to pay by general assessment shall be considered as a part of the debt of the municipality and shall not be valid unless such amount is within the constitutional debt limit of such municipality. Any incorporated city, by a two-thirds vote of the qualified voters thereof voting upon the question at a general or special election, may increase its limit of indebtedness three percent on the assessed valuation of taxable property in such city beyond five percent of the valuation thereof, and by a majority vote, in like manner, may increase its limit of indebtedness four percent of such valuation without regard to the existing indebtedness of such city for the purpose of constructing or purchasing waterworks for furnishing a supply of water to the inhabitants of such city, or for the purpose of constructing sewers; provided, that such increase or increases must be duly voted before the levy of any general taxes exceeding the existing debt limit may be made to pay part of the cost of any such improvement. In making any contract with reference to any special improvement, the governing body may take into consideration such portion of the cost of the improvement as will be paid by general assessment and may make appropriations and levy taxes and assessments therefor in annual installments extending over the same period of time as is provided in the special assessments for such improvement. The appropriation may be made at such time as occasion may require and shall be included in the municipality’s first annual tax levy thereafter. The appropriation and levy, whether it is made as a part of the regular annual appropriation ordinance or otherwise, shall state the specific improvement for which the assessment is made and the tax levied, the amount thereof, and the district in which the improvement is made. The amount of such assessment and the moneys collected thereon shall become a part of the district fund upon which the warrants issued in payment for the improvement are to be drawn.