Oregon Revised Statutes Water Resources: Irrigation, Drainage, Flood Control, Reclamation § 540.330

(1) Any owner or manager of a reservoir, located across or upon the bed of a natural stream, shall construct and maintain, when required by the Water Resources Commission, a measuring device below, and one above, the reservoir on each stream or source of supply discharging into the reservoir, to assist the watermaster in determining the amount of water to which appropriators are entitled and thereafter diverting it for their use.

(2) If any owner or manager of a reservoir located across the bed of a natural stream neglects or refuses to put in a measuring device after 10 days' notice by the commission, the watermaster may open the sluicegate or outlet of the reservoir, and it shall not be closed, under penalties of the law for changing or interfering with headgates, until the requirements of the commission as to such measuring devices are complied with.