Or. Admin. R. 690-385-6000
If the water right records show two or more rights as primary on the same land, the right with the oldest priority date shall be considered the primary water right unless the applicant designates a right, other than the right with the oldest priority date, as the primary water right. All other water rights shall be diminished to supplemental water rights.
ORS 536.025 & 536.027
ORS 540.580
WRD 9-2004, f. & cert. ef. 11-16-04