Mont. Code Ann. § 77-1-134

77-1-134 . Irrigation structures, utility structures, and bridges of formerly taxable land -- water rights. (1) If an irrigation structure, a utility structure, or a bridge was placed on land that consists of the bed of a navigable river or stream, the irrigation structure, utility structure, or bridge remains the property of the original owner or the original owner's successors in interest or assignees. Subject to 77-1-1112 (10), access to the irrigation structures, utility structures, and bridges described in this section for the purposes of operation, maintenance, repair, enhancement, or improvement may not be impeded by the state.

(2) Subject to 77-1-1112 (10), the change of designation of the bed of a navigable river or stream from a taxable to a nontaxable status may not interfere with or impede the exercise of a water right, including a livestock watering right for which a claim was not required to be filed pursuant to 85-2-212 and 85-2-222 .