Justin Kulongoski is a Research Hydrologist with the U.S. Geological Survey. His work includes regional water-quality assessments, and focused groundwater studies that explain the natural and human processes that affect water quality. As a geochemist, his research focuses on the use of isotopes to explore hydrologic systems, with the aim to better understand and quantify subsurface flow, mixing processes, and to characterize unique reservoirs. These isotopic techniques include the application of helium isotopes and noble gases, radiogenic isotopes, and the stable isotopes deuterium and oxygen-18 to investigate and characterize the timing of groundwater recharge, tectonic processes, and trends in groundwater quality.