Ohio Rev. Code Ann. § 6131.59

When an improvement consisting of a ditch, drain, or watercourse has been established and constructed or used for seven years or more, it shall be considered to be a public watercourse notwithstanding any error, defect, or irregularity in the location, establishment, or construction thereof, and the public shall have and possess in and to any such watercourse that has thus been constructed or used for seven years the rights and privileges that relate to and pertain to natural watercourses, but the same shall be subject to any improvement upon petition as provided in sections 6131.01 to 6131.64 of the Revised Code.