Hydrologic systems and the natural environment are continuously affected by human activities and climate change. Understanding these dynamic interactions is critical to predicting how hydrologic systems might respond to human activities, how these activities might degrade the natural environment, and how resilient the nation’s energy system and infrastructure are to these changes. For example, EVS applies a wide range of scientific and engineering expertise to address the complex environmental challenges associated with local hazardous waste sites, sustainable land use, regional and national hydrologic extremes, and global water resources.