Paul Hsieh, Ph.D., is a research hydrologist with the U.S. Geological Survey in Menlo Park, California, and is chief of its Hydrology of Fractured Rocks project. His experience includes fluid flow and solute transport in fractured rocks, hydraulic and tracer testing, computer simulation and visualization, groundwater resources in bedrock terrain, poroelasticity analysis of fluid/stress interaction, and subsurface deformation. Among his many distinguished honors, Hsieh served as the NGWREF Darcy Lecturer in 1995 and received NGWA’s John Hem Award in Science & Engineering in 2012.