This bill reauthorizes the United States-Mexico Transboundary Aquifer Assessment Program. It extends the authorization of appropriations for the program from fiscal years 2026 through 2036 , ensuring continued funding for cross-border water resource studies. The legislation also expands the geographic scope for designating priority transboundary aquifers to include Arizona, alongside New Mexico and Texas, though it specifically excludes an aquifer within the Yuma groundwater basin. Furthermore, it updates the program's sunset clause to align with this reauthorization, thereby extending the program's operational authority. These changes aim to facilitate ongoing scientific assessment and management of shared groundwater resources between the United States and Mexico.