Okla. Stat. tit. 17, § 159.19

In any proceeding to issue a certificate and in any other proceeding to regulate the rates of a water transportation line subject to the jurisdiction of the Corporation Commission, said Commission shall prescribe and enforce rates to provide a fair return on the fair value of the property of the water transportation line. Laws 1969, c. 109, § 9, emerg. eff. April 1, 1969.