No person may construct or cause to be constructed a dam or reservoir for the purpose of accumulating, storing, appropriating, or diverting any of the waters of this state, except in a thorough, secure, and substantial manner.
Mont. Code Ann. § 85-15-208, under Construction, Inspection, and Repair of Dams.
Mont. Code Ann. § 85-15-208
No person may construct or cause to be constructed a dam or reservoir for the purpose of accumulating, storing, appropriating, or diverting any of the waters of this state, except in a thorough, secure, and substantial manner.