Mont. Code Ann. § 76-15-612

Whenever any project petitioned for or created by the state or federal government has been made, built, constructed, erected, or accomplished as provided in this part, it is hereby made the duty of the board or boards of supervisors under whose jurisdiction the project area was created to adequately and suitably maintain and preserve said improvements and fully to keep the same in proper repair and operation by contract or otherwise in the way or manner as the board shall deem suitable and proper.