Whenever a public agency shall have executed a contract pursuant to this act and the payments thereunder are to be made either wholly or partly from the revenues of the public agency's waterworks, water supply system, sewerage system or sewage disposal system or a combination of such 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, such that the revenues therefrom together with any taxes levied in support thereof will be sufficient at all times to pay:
Miss. Code § 51-9-197