Whenever a public agency and a municipality shall have executed a contract under Sections 21-27-161 through 21-27-191 and the payments thereunder are to be made either wholly or partly from the revenues of the public agency's waterworks system, water supply system, treatment facility, sewerage system or sewage disposal system or from both systems or a combination of both systems, the duty is hereby imposed on the public agency to establish and maintain and from time to time to adjust the rates charged by the public agency for the services of such system or systems, to the end that the revenues therefrom together with any taxes levied in support thereof will be sufficient at all times to pay:
Miss. Code § 21-27-177