ARS | Publication request: RECURRING, MULTICOMPONENT GROUND-WATER TRACING EXPERIMENTS AT A WELL-CHARACTERIZED BASIN IN MANTLED KARST - LESSONS FROM THE SAVOY EXPERIMENTAL WATERSHED

Submitted to: Geological Society of America Meeting
Publication Type: Abstract
Publication Acceptance Date: October 30, 2002
Publication Date: October 30, 2002
Citation: Brahana, J.V., Davis, R.K., Sauer, T.J., Ting, T.E., Al-Rashidy, S., Whitsett, K., Al-Qinna, M. 2002. Recurring, multicomponent ground-water tracing experiments at a well-characterized basin in mantled Karst - lessons from the Savoy experimental watershed. GSA Abstracts and Program. 34(6): 158-159.

Technical Abstract: The SEW is a long-term field research facility of 1250 hectares owned by the University of Arkansas, and shared with state and federal researchers. More than 20 ground-water tracer tests in Basin 1 of the Savoy Experimental Watershed (SEW) have been conducted during the last 3 years, many at the same injection point, but under varying hydrologic conditions. Interpretation of these tests are providing understanding not only about the detailed hydrogeology of this basin, but also are providing insight into the effectiveness of different tracers under true field conditions in a mantled karst setting typical of the southern Ozarks. The following tracers have been used in Basin 1: fluorescein, rhodamine WT, chloride, bromide, lanthanum-labeled clay, indigenous E. coli labeled with europium, temperature, and specific conductance. Studies to date reveal that fast-flow components of the shallow karst aquifer at SEW transmits conservative tracers with point-to-point velocities that range from 15 to more than 800 meters per hour (m/hr). Computations of dilution factors for low-flow conditions all are within the range 2-9 x 10-7. Conservative tracer transport times through the vadose zone (1-2 meters) typically are several orders of magnitude longer than flow in the carbonate aquifer, reflective not only of a lower conductivity in the soil and regolith, but also of temporary storage along permeability contrasts and in response to recharge pulses. In the rapid flow part of the saturated aquifer, suspended sediments and bacteria reside in the aquifer longer than dissolved tracers (weeks and months versus days).