Umatilla Basin Project Completion Act

Umatilla Basin Project Completion Act - Amends the Umatilla Basin Project Act to authorize the Secretary of the Interior to construct a third and final phase (phase III) of the Umatilla Basin Project to provide additional water flows into the Umatilla River for anadromous fish through a water exchange with the Westland Irrigation District. Requires a feasibility study prior to such construction. Requires the execution of an exchange agreement with the District to allow the use of Columbia River water in exchange for an equal amount of Umatilla River or McKay Reservoir water. Authorizes agreements with other water users before completion of phase III. Requires the Administrator of the Bonneville Power Administration to provide for Project power necessary to effect the phase III water exchange.

Adjusts the boundaries of the four Project irrigation districts. Requires the irrigation districts, after the boundary adjustments, to provide water for environmental enhancement from McKay Reservoir to the Secretary under one of two options, as specified by the Secretary. Requires the Secretary to notify the districts of the option chosen within nine months after the enactment of this Act.

Prohibits any parcel from receiving Project water unless it has a valid State water right and is classified as irrigable. Requires an updated description of irrigation districts' boundaries as an attachment to all existing Project contracts.

Directs the Secretary to initiate discussions with the State of Oregon regarding the water claims of the Confederated Tribes of the Umatilla Indian Reservation and other water needs in the Umatilla River Basin. Authorizes the Secretary to contract with the Tribes for the construction of a portion of an off-stream storage reservoir of specified capacity and associated works, to be located on or adjacent to the Tribes' reservation.

Authorizes appropriations.

Protects existing water rights.

Expresses the sense of the Congress that construction and operation of phase III, the perpetual operation of the integrated Project, and construction and operation of the joint water supply system (as authorized under the prior Act) will fulfill all Government obligations to provide the Tribes with water for fishery purposes in the Umatilla River below the mouth of McKay Creek, as recognized under the Tribes' treaty with the United States.