; (ii) to supplement municipal supply in a subsurface aquifer; or (iii) to mitigate the effect of groundwater use on instream flow or senior water rights. (C) Aquifer storage and recovery projects designed to supplement existing irrigation water supply, or to store water in subsurface aquifers, for use by the Kittitas Reclamation District, the Roza Irrigation District, or any other proratable irrigation entity participating in the repayment of the construction, operation, and maintenance costs of the facilities under this section during years in which the total water supply available is insufficient to provide to those proratable irrigation entities all water to which the entities are entitled, 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 aquifer storage to enhance applicable existing irrigation water supply in accordance with such terms and conditions to which the Bureau of Indian Affairs and the Yakama Nation may agree