Idaho Code § 42-901
It shall be the duty of those owning or controlling any ditch, canal or lateral to appoint a superintendent or watermaster, whose duty it shall be to measure the water from such ditch, canal or lateral through the outlet of those entitled thereto, according to his or her pro rata share: provided, that any vicinity or neighborhood, the inhabitants of which use the waters of any ditch, canal or lateral for the purpose of irrigation, or have or claim a common right to the waters of any ditch or lateral for such purposes, provided the waters so claimed or used have not been allotted to the individual users thereof, shall constitute a water district.
Any one or more of said joint owners so using the water of any ditch, canal or lateral as aforesaid, when the appointment of a watermaster can not be agreed upon, may petition the judge of the district court in whose district the ditch, canal or lateral may be located for the appointment of a watermaster for said ditch, canal or lateral, and shall set forth in said petition the facts of his or her ownership in said ditch, canal or lateral; the ownership and interest of all other joint owners; the location and length of said ditch, canal or lateral, and requesting said district court to appoint a watermaster to take charge of the same. Upon due notice being given to all of the water users under said ditch, canal or lateral, and after hearing before said court, it shall be the duty of the judge of said district court if he deem it necessary or equitable in order that the rights of all water users under said ditch, canal or lateral may be protected, to appoint a watermaster for the ditch, canal or lateral described in the petition. Said watermaster to receive such compensation as the court in his judgment may deem adequate, and shall be paid in the same manner as is provided for the payment of watermasters under chapter 5 [6] of this title, and shall perform the same duties and have the same power and authority as other watermasters appointed or elected in accordance with the provisions of this code.
Idaho Code § 42-901