Oglala Sioux Tribe Angostura Irrigation Project Modernization and Development Act - Directs the Secretary of the Interior to: (1) carry out the modernization and improvement of the irrigation facilities at the Angostura Unit of the Pick-Sloan Missouri River basin program; and (2) provide for the delivery of the water saved through such modernization and improvement for fish and wildlife purposes and environmental restoration on the Pine Ridge Indian Reservation (South Dakota) .
Establishes the Oglala Sioux Tribal Development Trust Fund.
Requires the governing body of the Oglala Sioux Tribe of South Dakota to prepare a plan for the use of payments to the Tribe out of the Fund.
Prohibits distribution of any payment to any member of the Tribe on a per capita basis.
States that no payment made to the Tribe shall result in the reduction or denial of any entitlement service or program.