United States-Mexico Transboundary Aquifer Assessment Act

United States-Mexico Transboundary Aquifer Assessment Act - Establishes a United States-Mexico transboundary aquifer assessment program to characterize, map, and model groundwater resources along the border. Describes as the program's objectives to: (1) develop an integrated approach to assess transboundary groundwater resources, including identifying fresh and saline aquifers, prioritizing the aquifers for further analysis, and creating a geographic information system database for each priority aquifer; (2) expand existing agreements between the U.S. Geological Survey, the Border States (Arizona, California, New Mexico, and Texas), the Water Resources Research Institutes, and appropriate U.S. and Mexican authorities to conduct joint scientific investigations and archive and share relevant data; and (3) produce scientific products for each priority aquifer to provide water managers and natural resource agencies with necessary information.

Designates as priority transboundary aquifers the: (1) Hueco Bolson and Mesilla aquifers; (2) Santa Cruz River Valley aquifers; and (3) San Pedro aquifers.

Requires the Secretary of the Interior to: (1) develop partnerships with relevant organizations in Mexico; and (2) coordinate activities with water resource agencies in the Border States and affected Indian tribes. Prohibits the Secretary from initiating any field studies before consulting and coordinating with the Border State water resource agency with jurisdiction over the aquifer.

Authorizes the Secretary to make grants and enter into cooperative agreements with water resource agencies and Border States to carry out the program.