Three Affiliated Tribes and Standing Rock Sioux Tribe Equitable Compensation Act

Three Affiliated Tribes and Standing Rock Sioux Tribe Equitable Compensation Act - Declares that: (1) the Three Affiliated Tribes (TAT) (the Mandan, Hidatsa, and Arikara Tribes that reside on the Fort Berthold Indian Reservation) are entitled to additional financial compensation from amounts deposited to a TAT Recovery Fund for the taking of reservation lands for the site of the Garrison Dam and Reservoir; and (2) the Standing Rock Sioux Tribe (SRST) (members of the Great Sioux Nation that reside on the Standing Rock Indian Reservation) is entitled to additional financial compensation from amounts deposited to a SRST Economic Recovery Fund for the taking of reservation lands as the site for the Oahe Dam and Reservoir.

Establishes such Funds. Directs the Secretary of the Treasury to deposit into each Fund 25 percent of the receipts from deposits to the Treasury for the preceding fiscal year from the integrated programs of the Eastern Division of the Pick-Sloan Missouri River Basin Project administered by the Western Area Power Administration, subject to certain limitations. Authorizes appropriations to each Fund. Makes available only the interest on the moneys in each Fund for use by the Secretary of the Interior in making payments to the SRST for use for educational, social welfare, economic development, and other programs. Specifies that: (1) no payments pursuant to this Act shall result in the reduction or denial of any Federal services or programs to which the TAT or SRST, or any of their members, are otherwise entitled to because of their status as a federally recognized Indian tribe or member pursuant to Federal law; (2) no such payments shall be subject to Federal or State income tax, or affect power rates; and (3) no part of any moneys in either Fund shall be distributed to any TAT or SRST member on a per capita basis.

Authorizes the Secretary to develop irrigation within the boundaries of the Standing Rock Indian Reservation, subject to a finding by the Secretary of irrigability of the lands to receive water.

Declares certain lands in North Dakota to be held in trust by the United States for the TAT as part of the Fort Berthold Reservation. Retains for the United States a flowage and sloughing easement over a specified portion of such lands for flood control and related Garrison Dam and Reservoir project purposes.

Requires the Secretary of the Army to: (1) sell certain lands and minerals underlying such lands, subject to the right of the United States to continuously or intermittently inundate such lands with water as necessary for the operation of dam and reservoir projects; and (2) give the right of first refusal to any applicant, with respect to any land owned by such person immediately prior to its acquisition by the United States. Requires that any such lands sold be conveyed subject to any lease in effect with respect to such lands at the time of such conveyance.

Declares certain lands to be held in trust by the United States for the SRST as part of the Standing Rock Indian Reservation.

Transfers: (1) certain nontribal lands to those individuals from whom they were taken, or their assignees; and (2) certain lands acquired from the State of North Dakota to the State.

Authorizes appropriations, including sums to carry out irrigation projects for the SRST.