Idaho Code § 43-1406
One or more irrigation districts organized under the laws of this state may unite with one or more adjacent irrigation districts organized under the laws of any adjoining state in the purchase or construction of an irrigation system or works for the irrigation of the land within said respective irrigation districts; and in such case said irrigation districts are hereby jointly granted the same power of condemnation as is now possessed by one (1) district alone; and in such case the cost of purchase, acquisition or construction of such irrigation system shall be apportioned to each district in proportion to the acreage in each district for which water shall be provided and such joint works shall be owned jointly in proportion to such respective acreage; a joint commission not exceeding seven (7) in number shall be chosen by the board of directors of the respective irrigation districts, the members of which shall be apportioned to each district as nearly as practicable in accordance with the acreage for which water shall be provided in each respective district; said commission shall control and manage such joint works subject to the board of directors of the respective districts and each member of such commission shall hold office at the will of the board of directors of the district appointing him.
Idaho Code § 43-1406