This legislation authorizes the establishment of the Dry-Redwater Regional Water Authority System , a critical infrastructure project designed to provide a safe and adequate municipal, rural, and industrial water supply. The system will serve citizens across Dawson, Garfield, McCone, Prairie, and Richland Counties in Montana, as well as McKenzie County in North Dakota, addressing long-standing water needs in these regions. The Secretary of the Interior is authorized to carry out this project, based on a specific feasibility study, and must enter into a cooperative agreement with the Dry-Redwater Regional Water Authority. This agreement facilitates federal assistance for the planning, design, and construction phases, with the federal government covering up to 75 percent of the total costs. Federal funds can be utilized for various components, including water pumping, treatment, storage facilities, transmission pipelines, and necessary electrical power infrastructure, but explicitly exclude operation, maintenance, or replacement expenses. Title to the Water System will be held by the Authority. The bill also ensures the operational power needs of the Water System by making power available from the Pick-Sloan Missouri River Basin Program at the firm power rate. The Authority will be responsible for these power charges and any non-Federal transmission costs, while the Act clarifies it does not preempt State water laws. Finally, the legislation authorizes $602,000,000 in appropriations for the period of fiscal years 2027 through 2037, with provisions for adjusting this amount based on cost indexing and market volatility.