ORS § 538.410
All rights to the waters of the lakes, rivers and streams of this state acquired before February 24, 1909, for the purposes of municipal water supply are confirmed, and no rights acquired under the Water Rights Act (as defined in ORS 537.010) shall impair the rights of any municipal corporation to waters taken before February 24, 1909. The Water Resources Commission shall reject, or grant subject to municipal use, all applications where, in the commission's judgment, the appropriation of the waters applied for impairs a municipal water supply. Municipal corporations of the state, on request of the Water Resources Commission, shall furnish a statement of the amount and source of the municipal water supply, with probable increase or extension of the same.
ORS 538.410