Rates, fees, and charges for water service, sewer service, and fire protection service rendered by the district from any of its water systems, sewer systems or fire protection facilities shall be so fixed and from time to time revised as at all times to provide funds at least sufficient to:
(1) Pay the cost of operating, maintaining, repairing, replacing, extending, and improving the systems and facilities or either from which such services are rendered;
(2) Pay the principal of and the interest on all bonds issued and obligations assumed by the district that are payable out of the revenues derived from operation of those systems and facilities as the said principal and interest become due and payable;
(3) Create and maintain such reserve for the foregoing purposes or any of them as may be provided in any mortgage and deed of trust or trust indenture executed by the district under this chapter or in any resolutions of the board authorizing the issuance of bonds, the assumption of any obligation or the acquisition of any such system or facility; and
(4) Make such annual payments, if any, to the United States of America or any agency or instrumentality thereof, the state, municipalities, counties, departments, authorities, agencies. and political subdivisions of the state and any public corporations organized under the laws of the state as the district may have contracted to make.