In and by such resolutions and contract the city may bind itself to establish and maintain special rates and charges for the service of said plant, over and above its regular water rates, sufficient to produce net revenues adequate to make all payments of principal and interest on     said revenue bonds or certificates when such payments become due, or to establish and maintain a prescribed schedule of such rates and charges, to pay, at an agreed rate or rates, for treatment of all water used by the city and not resold, and to do and perform any other acts or things which, in the discretion of the governing body, are deemed reasonable and appropriate for the construction, operation, and financing of said plant on the most efficient and economical basis, and the city may make covenants and agreements with respect to any and all of the matters stated in section 40-35-13.