This legislation, known as the Navajo-Gallup Water Supply Project Amendments Act of 2025, amends the existing Northwestern New Mexico Rural Water Projects Act to enhance and facilitate the completion of the Navajo-Gallup Water Supply Project. A primary change involves a substantial increase in authorized appropriations for the Project, raising the total from $870,000,000 to $2,175,000,000 for the period of fiscal years 2009 through 2029. This adjustment also includes mechanisms for future cost changes due to construction and market volatility. The bill expands the Project Service Area to deliver water to additional Navajo Nation communities in the Rio San Jose Basin in New Mexico and Lupton, Arizona. This expansion is intended to increase service without exceeding existing authorization levels and potentially reduce overall unit operation and maintenance costs. Furthermore, it authorizes the Secretary to acquire specific water conveyance and storage facilities associated with the San Juan Generating Station, along with taking certain Nation fee land and public domain land into trust for the Navajo Nation, including the land underlying these facilities. A key provision establishes the Navajo Nation's Navajo-Gallup Water Supply Project Deferred Construction Fund . This fund allows for the deferral of construction for selected Project facilities by mutual agreement, with allocated funds deposited into it. The Navajo Nation can then use these funds to construct the deferred facilities or approved alternate facilities, and depositing these funds fulfills the Secretary's construction obligations for those components. The legislation also revises the framework for several trust funds critical to the Project's long-term sustainability. It updates the Navajo Nation Water Resources Development Trust Fund and establishes the Navajo Nation Operations, Maintenance, and Replacement Trust Fund with an authorization of $250,000,000. Additionally, it creates the Jicarilla Apache Nation Operations, Maintenance, and Replacement Trust Fund, authorizing up to $10,000,000 after an "Ability to Pay" study, to cover their share of operation and maintenance costs. Regarding financial obligations, the bill amends the City of Gallup's repayment responsibility, setting a maximum obligation of $76,000,000 and clarifying that their contribution will be "not more than 25 percent." It also introduces new rules for taxation of Project facilities, stipulating that activities on trust land are subject to Nation taxation, while activities on other lands are subject to State or local taxation. Finally, the bill permits the Navajo Nation to convey up to 2,000 acre-feet per year of non-Project water to its communities in Utah using Project infrastructure. This provision comes with strict conditions, including that it must not delay the main Project, Project funds cannot be used for new infrastructure for this purpose, and the water must be accounted for against Utah's apportionment under the Navajo/Utah Settlement Agreement.