Idaho Code § 42-1303
The operation, improvement, repair and maintenance of any such lateral or distributing ditch shall be under the direction of the directors of the association. Following the association's annual meeting, the association's directors and the lateral manager shall examine the lateral or laterals or distributing ditch or ditches, and prepare an estimate of the total cost to operate, repair, improve and maintain the lateral or laterals or ditch or ditches to properly deliver water to the water users' lands during the succeeding season, including the compensation of officers and lateral manager. Such total cost shall be assessed to each water user either (1) in the proportion which the quantity of water the water user is entitled to receive from such lateral or ditch bears to the total quantity of water which all association water users are entitled to receive therefrom, or (2) if the water user's land consists of a lot or lots within a city or village, then the assessment may be made upon the basis of each lot, the same to be uniform upon lots of the same size.
Idaho Code § 42-1303