Wash. Rev. Code § 87.03.849
The members of the board of directors of the major irrigation district shall hold office as directors of the district formed by the merger until the end of their terms of office. If the major district is divided into director divisions, the board of the major district shall propose a plan for redividing the district into divisions that reflect the boundaries of the district created by the merger and this requirement regarding the directors of the major district. If the major district is considering a merger with more than one minor district, the board shall submit plans for the various possible mergers. The proposal or proposals shall be filed with the county legislative authority before the merger is approved in the major district or the minor district or districts. Following the merger, the county legislative authority shall approve the plan submitted for the districts that actually merged.
On the effective date of the merger, the directors of the minor district shall transfer the property and other assets of the district as required in RCW 87.03.853. Following the transfer of the property and other assets, the minor irrigation district and the office of director of the minor district shall cease to exist.
The board of directors of the district formed by the merger shall have all the powers and obligations of the boards of the major and minor districts that were merged to form the district including, but not limited to, such boards' powers and obligations for any local improvement districts created in the minor or major district under this chapter.
RCW 87.03.849