Wash. Rev. Code § 87.68.060
In any election called and held in an irrigation district organized and existing under the laws of this state, comprising two hundred thousand or more acres of land within its boundaries, for the purpose of voting on any proposed contract between the district and the United States or any agency thereof where the proposed contract is to include a provision in accordance with the fourth proviso in section 1(b) of the act of congress of May 27, 1937 (50 Stat. 208), the notice of said election shall state, in addition to the other matters and things required by law relating to elections in such districts, that the proposed contract shall include a provision in accordance with the fourth proviso in section 1(b) of the act of congress of May 27, 1937 (50 Stat. 208), and shall also set forth the provisions of section 1(a) and (b) of said federal act.
RCW 87.68.060
Qualification of voters: RCW 87.03.045.