(1) Applicants seeking a water reservation of water for instream purposes or diversionary uses with points of diversion in the Missouri River basin above Fort Peck Dam pursuant to 85-2-331, MCA, shall submit applications on or before July 1, 1991. The board shall make a final determination on all applications for water reservations above Fort Peck Dam on or before July 1, 1992. Applications for the reservation of water for instream purposes or diversionary uses with points of diversion below Fort Peck Dam and the Little Missouri River basin must be submitted on or before July 1, 1991. The board shall make a final determination on applications for water reservations below Fort Peck Dam on or before December 31, 1994. For the purposes of this rule, the Missouri River basin below Fort Peck Dam includes all drainages that would enter the Missouri River downstream of Fort Peck Dam, including the Milk River basin, the Little Missouri River basin, and any groundwater therein. An application to reserve water below Fort Peck Dam may be filed as an amendment to an application to reserve water above Fort Peck Dam, if filed by the same applicant for the same purpose.

(2) The priority date of Missouri reservations applied for and granted in accordance with the deadlines provided in (1) is July 1, 1985 in the Missouri River basin and July 1, 1989 in the Little Missouri basin. Applications for water reservations in the basins submitted after the deadlines provided in (1) will be accepted, but the priority date shall be the date of filing with the department a notice of intention to apply for a water reservation. Separate environmental impact statements and board hearings may be required for such late applications.

(3) The use of reserved water with a July 1, 1985 priority date may, at the discretion of the board, be subordinated to the use of water under permits with priority dates after July 1, 1985 which are issued before the date of the board order granting such reservations. The use of reserved water with a July 1, 1989 priority date may, at the discretion of the board, be subordinated to the use of water under permits with priority dates after July 1, 1989 which are issued before the date of the board order granting such reservations. The board may provide for subordination only if it finds that such permits would not substantially interfere with the purpose of a reservation. The board may consider subordination after issuing its order reserving water. The hearing convened in the matter of objections to the reservations may be separated into two proceedings to consider the establishment of the water reservations and the subordination of those reservations independently.

(4) If, after issuing a final order reserving water in the Missouri basin, the board decides to consider the subordination of the established reservations, the department shall, if necessary, prepare a supplement to the environmental impact statement prepared for the decision to establish the water reservations. This supplement, if necessary, shall address the matter of subordination, including an evaluation of the effects of subordination to the reservants. A request to subordinate a water reservation to a permit may be initiated by the board, the department or by petition of an affected permittee. The record of evidence and testimony presented at the hearing establishing the reservations will be considered part of the record in the hearing on subordination. Additional evidence and testimony limited to the matter of subordination may be presented. The person seeking the subordination has the burden to prove by preponderance of evidence the criteria in 85-2-316(9) (d) , MCA. Notice of the hearing shall be provided to all affected permittees, permit applicants, reservants, and all parties who participated in the hearing on the matter of establishing the reservations. A separate final order may then be issued by the board on the matter of subordination.

(5) A permit does not substantially interfere with the purpose of a reservation if the reservation is not significantly diminished in value as defined in ARM 36.16.105A through 36.16.105C from water use under the permit.

(6) Substantial interference with the purpose of a reservation may result from water use under an individual permit or from the cumulative effect of water use under two or more permits. The board may subordinate a reservation to water use under only those permits, in order of priority, which cumulatively would not result in substantial interference.

(7) If a reservation is subordinated to one or more permits, and that reservation is senior in priority to one or more reservations in the same water course, all junior reservations granted pursuant to 85-2-331, MCA shall also be subordinate to the same permit or permits.