Okla. Stat. tit. 11 § 37-118
For use in connection with the acquisition, establishment, betterment or expansion, and the maintenance or operation of its municipal waterworks system, any municipality may acquire title to, or any lesser interest in, any lands or water rights, or both, in any state adjoining the State of Oklahoma, which lie within any watershed from which the municipality obtains, or desires to obtain, its municipal water supply. The municipality may acquire any necessary easements or rights-of-way for pipelines to convey water from such water supply to a point or points within the State of Oklahoma, over and across lands not within such watershed, if, and to the extent, and in the manner, permitted by the laws of the adjoining state.
Okla. Stat. tit. 11, § 37-118