Mont. Code Ann. § 85-7-1907

The board may also construct and maintain the necessary dams, reservoirs, and works for the collection and distribution of water for the district or any subdistrict in the district, from one or more sources and from different and additional sources; operate such works; secure, in any of the manners provided in this chapter, additional water supplies from the same or different sources; and do any and every lawful act necessary to be done in order that sufficient water may be furnished for irrigation purposes to all the lands in the district or subdistrict included at the time of its organization or at any time thereafter.