Oregon Revised Statutes Water Resources: Irrigation, Drainage, Flood Control, Reclamation § 547.755

No part of a drainage district annexed to a city shall be withdrawn from the district, except upon the consent of the voters of that part of the district. The votes shall be counted in the same manner as in elections for officers of the district. If three-fourths of those voting in that part of the district favor withdrawal from the district the withdrawal is effective, subject to ORS 222.520 (2), ORS 222.528 and 222.560 relating to division of assets and liabilities upon withdrawal from sanitary districts.