Combined interpretation of radar, hydraulic, and tracer data from a fractured-rock aquifer near Mirror Lake, New Hampshire, USA

• Published in: Hydrogeology journal 2006-01, Vol.14 (1-2), p.1-14
• Main Authors: Day-Lewis, Frederick D, Lane Jr, John W, Gorelick, Steven M
• Format: Article
• Language: English
• Subjects: Aquifers; Computational fluid dynamics; Fluid flow; Geological surveys; Geophysics; Groundwater; Groundwater flow; Heterogeneity; Hydraulics; Hydrologic research; Hydrology; Lakes; Mass transfer; Mathematical models; Piezometric head; Radar; Rock; Rocks; Solute transport; Tracers; Water flow
• ISSN: 1431-2174; 1435-0157
• DOI: 10.1007/s10040-004-0372-y

An integrated interpretation of field experimental cross-hole radar, tracer, and hydraulic data demonstrates the value of combining time-lapse geophysical monitoring with conventional hydrologic measurements for improved characterization of a fractured-rock aquifer. Time-lapse difference-attenuation radar tomography was conducted during saline tracer experiments at the US Geological Survey Fractured Rock Hydrology Research Site near Mirror Lake, Grafton County, New Hampshire, USA. The presence of electrically conductive saline tracer effectively illuminates permeable fractures or pathways for geophysical imaging. The geophysical results guide the construction of three-dimensional numerical models of ground-water flow and solute transport. In an effort to explore alternative explanations for the tracer and tomographic data, a suite of conceptual models involving heterogeneous hydraulic conductivity fields and rate-limited mass transfer are considered. Calibration data include tracer concentrations, the arrival time of peak concentration at the outlet, and steady-state hydraulic head. Results from the coupled inversion procedure suggest that much of the tracer mass migrated outside the three tomographic image planes, and that solute is likely transported by two pathways through the system. This work provides basic and site-specific insights into the control of permeability heterogeneity on ground-water flow and solute transport in fractured rock.Original Abstract: Una interpretacion integrada de radar experimental de campo transversal a pozos, trazadores, y datos hidraulicos demuestra el valor de combinar el monitoreo geofisico realizado en periodos de tiempo con mediciones hidrologicas convencionales en la caracterizacion mejorada de un acuifero rocoso fracturado. Se llevo a cabo tomografia de radar por periodos de tiempo y diferencia de atenuacion durante un experimento con trazadores salinos en el sitio de investigacion hidrologica de roca fracturada del Servicio Geologico de Estados Unidos cerca del Lago Espejo, Condado Grafton, New Hampshire, USA. La presencia del trazador salino electricamente conductivo refleja efectivamente fracturas permeables o trayectorias para imagenes geofisicas. Los resultados geofisicos orientan la construccion de modelos numericos tri-dimensionales de flujo de agua subterranea y transporte de solutos. En un esfuerzo por explorar explicaciones alternativas para los datos tomograficos y trazadores se considera un conjunto de mo