Attended the SAGEEP meeting in\u00a0Denver, Colorado USA I March 17-21, 2013. \u00a0Presented a paper:<\/p>\n
Monitoring Shallow Subsurface Flow on a Hillslope using Time-lapse GPR and ERT<\/b><\/p>\n
Jonathan E. Nyquist, Derek Lichtner, Laura Toran, Temple University, Philadelphia, PA<\/p>\n
Li Guo, and Henry Lin, Penn State University, University Park, PA<\/p>\n
To improve our understanding of aquifer recharge, storm water management, contaminant transport, weathering, erosion and soil development, we need better ways to characterize subsurface flow in response to precipitation and snowmelt.\u00a0 Rainfall on a hillside does not simply partition into surface runoff and water that percolates vertically to the water table.\u00a0 Much of the flow is lateral through the root zone, controlled by networks of macropores, and these preferential flow paths can change from event to event depending on precipitation and antecedent moisture conditions. \u00a0\u00a0Our research focused on using geophysical monitoring tools to detect these shallow preferential flow paths.<\/p>\n
In July, 2012, we conducted a series of infiltration tests at the Shale Hills Critical Zone Observatory in central Pennsylvania. Working on a forested hill slope with a thin soil cover (approximately 30 cm thick Weikert soil series ) we conducted a set of small-scale infiltration experiments.\u00a0 In each case, we released 26.5L or 53L of water at constant head into a 1-m long, 10 cm deep trench located 20 cm upslope of our 1 m by 3 m geophysical survey area. \u00a0The geophysical methods tested were time-lapse electrical resistivity tomography (ERT), time-lapse ground penetrating radar (GPR), and two other GPR methods sensitive to moisture changes: GPR ground wave velocity and GPR surface reflectance. \u00a0While calibration of the geophysical data to obtain volumetric soil water content proved problematic, qualitatively all of the methods detected unexpectedly rapid lateral flow, with water traveling as far as 80 cm downslope within 15 minutes after the water injection ended.\u00a0 Introducing a second water pulse shortly after the first showed flow controlled by hillside microtopography and by hydrologic connectivity created by the first water release.\u00a0 \u00a0\u00a0\u00a0While none of the geophysical methods had sufficient resolution to map individual macropores, they all showed promise for characterizing heterogeneous patterns of subsurface lateral flow.<\/p>\n","protected":false},"excerpt":{"rendered":"
Attended the SAGEEP meeting in\u00a0Denver, Colorado USA I March 17-21, 2013. \u00a0Presented a paper: Monitoring Shallow Subsurface Flow on a Hillslope using Time-lapse GPR and ERT Jonathan E. Nyquist, Derek Lichtner, Laura Toran, Temple University, Philadelphia, PA Li Guo, and … Continue reading