Abstract: What comes to mind when imagining water flow underground? Perhaps saturated sand with water moving uniformly through pore spaces, or a flownet from a standard groundwater model? These Darcy-based perceptions often ignore the reality of preferential flow—the rapid movement of water along discrete, high-conductivity pathways. Building a sound hydrogeologic conceptual model relies on recognizing the geological controls on preferential flow paths, as they dictate the true velocity and direction of subsurface transport. Clear indications of preferential flow are observed at multiple scales—from soils, to catchments, to broader regional aquifers—with the ultimate manifestation at surface springs. While preferential flow is ubiquitous, this presentation will focus on karst systems where preferential flow is the dominant mechanism, and how failing to account for these non-uniform pathways leads to critical failures in managing stormwater runoff, predicting contaminant transport, and mitigating sinkhole formation.

Bio: Dan Doctor is a Research Geologist with the USGS who specializes in the study of karst. Dan holds a B.A. in Geology from Colgate University and a Ph.D. in Hydrogeology from the University of Minnesota with a doctoral minor in Water Resources. Dan joined the USGS as a postdoctoral researcher in Menlo Park, California where he applied natural stable isotope tracers to problems in catchment hydrology and biogeochemical cycling. Since 2006 he has been with the USGS National Center in Reston, Virginia where he conducts geologic mapping and specialized studies within the Appalachian Valley and Ridge province from West Virginia to New York. His recent work has included a national assessment of sinkhole hazards, resolving stratigraphic problems of the Appalachian Basin, and the geomorphological evolution of Appalachian landscapes