; (ii) shall be used exclusively by the Secretary to enhance the water supply during years for which the total water supply available is not sufficient to provide a percentage of proratable entitlements in order to make that additional water available, in a quantity representing not more than 70 percent of proratable entitlements to the Kittitas Reclamation District, the Roza Irrigation District, or any other proratable irrigation entity participating in the construction, operation, or maintenance costs of a facility under this section, in accordance with such terms and conditions as the districts may agree, subject to the conditions that— (I) the Bureau of Indian Affairs, the Wapato Irrigation Project, and the Yakama Nation, on an election to participate, may also obtain water from Kachess Reservoir inactive storage to enhance applicable existing irrigation water supply in accordance with such terms and conditions as the Bureau of Indian Affairs and the Yakama Nation may agree; and (II) the additional supply made available under this clause shall be available to participating individuals and entities based on— (aa) the proportion that— (AA) the proratable entitlement of each participating individual or entity; bears to (BB) the proratable entitlements of all participating individuals and entities; or (bb) such other proportion as the participating entities may agree; and (iii) shall not be any portion of the total water supply available. (B) Effect of paragraph Nothing in this paragraph affects, as in existence on the date of enactment of this Act, any— (i) contract; (ii) law (including regulations) relating to repayment costs; (iii) water rights