Whenever five or a majority of the holders of title to or evidence of title to any land susceptible of irrigation from the water supply and system of works of any irrigation district in this state, comprising within its boundaries two hundred thousand or more acres of land now existing or hereafter organized, desire to have such land included in said irrigation district, they may file a petition, in writing, with the board of directors thereof praying that such land be included in such district.
RCW 87.03.615