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Fort Peck Indian Reservation Compact

85-20-201 MCA

A compact between the State of Montana, the United States, and the Assiniboine and Sioux Tribes of the Fort Peck Indian Reservation was ratified by the 1985 Montana Legislature and signed by Governor Ted Schwinden on May 15, 1985. This compact allows the Fort Peck Indian Reservation to divert water annually from the Missouri River and its tributaries, providing water for consumptive domestic, agricultural and industrial uses. The compact was approved by appropriate federal agencies, and the Montana Water Court issued a final decree for this compact in August 2001 (Case #WC-92-1).

Compact Summary

The Fort Peck Reservation is located in northeastern Montana. It is 110 miles long (east to west) and 40 miles wide (north to south), encompassing slightly over two million acres. Over 6,000 tribal members live on the Reservation along with several hundred Indians belonging to other tribes. Reservation lands were allotted to the Indians beginning in 1908 and then opened to settlement by non-Indian homesteaders. Today, about half the lands of the Reservation are owned by non-Indians. Approximately 550,000 acres are held in trust by the United States for Indian allottees and another 400,000 are held in trust for the Tribes. Trust and fee lands are interspersed in a “checkerboard” pattern.

The climate is semi-arid, with average annual precipitation between 12 and 13 inches. The major water resource of the Reservation is the mainstem Missouri which has an average annual flow of approximatley seven million acre feet. Fort Peck Dam, a major Missouri Basin hydroelectric project constructed by the Corps of Engineers, is located five miles upriver from the Reservation. The one-hundred mile Reservoir holds 20 million acre-feet of water. A number of much smaller tributaries of the Missouri originate on or flow through the Reservation in a generally north to south direction. The major run-off in these streams is in March and April; flows are often intermittent in the late summer, and the water quality is poor.


The Compact quantifies the  water reserved for the Assiniboine and Sioux Tribes as 1,050,472 acre feet of diversions, or a consumptive use of 525,236 acre feet per year. A maximum of 950,000 acre feet may be diverted, and 475,000 acre feet may be used, from surface water each year. The rest would have to come from groundwater. The Tribes can use this water for irrigation, or for any other purpose determined by them on the Reservation. Part of the Tribes’ water right may be used to establish instream flows to protect fish and wildlife resources on various tributary streams on the Reservation.

The Compact provides that nonuse of the Tribal Water Right does not abandon or forfeit the Tribes’ right, which is a standard component of reserved water rights.

Tribal Jurisdiction Over Tribal Water Rights and Resolution of Disputes by Impartial Board
Under the Compact, the United States continues to administer and settle disputes concerning water use on the Fort Peck Irrigation Project, which presently serves less than 20,000 acres of Indian and non-Indian lands on the Reservation with water from the Missouri River. The Tribes administer all other uses of water on the Reservation by itself, by Indians, or by non-Indians who either lease water from the Tribes or claim a water right under federal law because they purchased a former trust allotment. The Tribes have adopted a water code that is the basis for resolving all water disputes among these persons. The State administers all water rights established pursuant to state law, including those held by non-Indians on the Reservation.

These separate administrative systems make it less likely a dispute will arise between the Tribes and the State, or between tribal and state water users. If a dispute does occur, resolution will be determined by a new Joint Tribal-State Board established by the Compact. This Board has one representative from the State, one from the Tribes, and a third to be selected by neutral means. It has the power to subpoena witnesses, to hold hearings and take testimony. All decisions must be by majority vote.

Appeals of the Board’s decisions may be had in a court of competent jurisdiction, but the scope of review is limited in a fashion very similar to that of an award in binding arbitration. Decisions of the Board must be enforced by any court of competent jurisdiction unless an appeal is timely filed.


The Compact recognizes that the Tribes may market water within the Reservation to non-Indians without complying with any state law or administrative regulation. The permanent sale of tribal water is not authorized. The Compact also provides that the Tribes may market their water outside the Reservation by leasing or otherwise transferring it for up to 50 years, so long as a number of requirements in the Compact are met.

Protection of Existing Uses on Missouri River Tributaries
The Tribes agree in the Compact to make no use of the mainstem of Milk River, which is the western boundary of the Reservation for only a few miles above its confluence with the Missouri. This is because their engineers advised the Tribes that the lands in this area could better be served from the Missouri, which is a dependable, high-quality source.

The Compact also protects all existing Indian and non-Indian uses on the other streams that flow through, and the ground water basins that underlie, the Reservation. About 33,000 acres are presently irrigated from these streams or groundwater basins, mostly by non-Indians. About half the irrigation is from groundwater. Most of the acres irrigated from surface flow are by means of “water spreading”—capturing high stream flows during the early spring runoff. These irrigation uses are protected, as are present and future domestic uses and figure stock watering impoundments not in excess of 20 acre-feet per year. All new non-Indian uses, however, will be subordinate to future exercise of the Tribes’ reserved rights.


Compact Appendices

Appendix A - Protected Uses


Instream Flow Schedule