This bill, titled the Transboundary Aquifer Assessment Program Act , reauthorizes the existing United States-Mexico transboundary aquifer assessment program. It amends the original Act to expand the designation of priority transboundary aquifers to include areas in Arizona , with a specific exclusion for a portion of the Yuma groundwater basin. Furthermore, the legislation significantly updates the program's funding by authorizing $1,500,000 annually for each of fiscal years 2026 through 2033. This replaces the previous lump sum authorization and extends the program's financial support for an additional eight years. Finally, the bill adjusts the program's sunset clause, effectively extending its operational period by referencing the enactment date of this new reauthorization act.