INTRODUCTION TO THE WORKSHOP PROCEEDINGS Competition for water resources, habitats, and urban areas in the Borderlands has become an international concern. In the United States, Department of Interior Bureaus, Native American Tribes, and other State and Federal partners rely on the U.S. Geological Survey (USGS) to provide unbiased science and leadership in the Borderlands region. Consequently, the USGS hosted a workshop, ?Facing Tomorrow?s Challenges along the U.S.-Mexico Border,? on March 20?22, 2007, in Tucson, Ariz., focused specifically on monitoring, modeling, and forecasting change within the Arizona-Sonora Transboundary Watersheds