ORS § 539.120
The Water Resources Director, or a qualified assistant, shall proceed at the time specified in the notice to the parties on the stream given as provided in ORS 539.030, to make an examination of the stream and the works diverting water therefrom used in connection with water rights subject to this chapter, for which a registration statement has been filed as provided in ORS 539.240. The examination shall include the measurement of the discharge of the stream and of the capacity of the various diversion and distribution works, and an examination and approximate measurement of the lands irrigated from the various diversion and distribution works. The director shall take such other steps and gather such other data and information as may be essential to the proper understanding of the relative rights of the parties interested. The observations and measurements shall be made a matter of record in the Water Resources Department. The department shall make or have made a map or plat on a scale of not less than one inch to the mile, showing with substantial accuracy the course of the stream, the location of each diversion point and each ditch, canal, pipeline or other means of conveying the water to the place of use, and the location of lands irrigated, or in connection with which the water is otherwise used, within each legal subdivision.
ORS 539.120