Idaho Code § 42-2702
In all contracts for the sale of lands, hereafter made, the irrigation of which depends upon the construction of irrigation works under the provisions of the Reclamation Act of June 17, 1902, it shall be provided that the purchaser shall apply for a water right from the government works, and subscribe such lands in the water users' association of the project in which they are located, within one (1) year after said contract of purchase is made, or in case there should be no association, at the time of the sale of the state lands, to which such subscription can be made, it shall be provided in said contract, that such application and subscription shall be made within one (1) year after such association is formed, and upon failure of the purchaser or purchasers to comply with the provisions of this section, the lands so purchased shall revert to the state together with the payment or payments made thereon, as fully and completely as if no sale had ever been made.
Idaho Code § 42-2702