CHARACTERIZING SEDIMENT TRANSPORT DURING STORM FLOW THROUGH A KARST AQUIFER, INNER BLUEGRASS REGION, KENTUCKY

The characterization of sediment transport through a karst aquifer can reveal possible vectors for contaminant transport. The Blue Hole karst groundwater basin is located in Woodford County, Kentucky. Previous dye traces in the area have shown that sources for recharge include Big Spring (a swallet located in downtown Versailles) and a sinkhole located on a farm ~1 km southeast of downtown. Blue Hole spring emerges ~540 m northwest of the Big Spring swallet. To characterize discharge at Blue Hole spring, stream stage and temperature were monitored continuously and discharge measurements were recorded weekly by wading with a current meter. Stream stage was correlated to discharge, building upon a preliminary rating curve developed by the Kentucky Geological Survey. Values of specific conductance (SC) and pH, which were measured weekly with portable meters, ranged from 0.400 to 0.740 ms/cm for SC and from 6.7 to 7.4 for pH. Following a 4.37-cm rainstorm on November 29, 2002, a quantitative dye trace with Rhodamine WT was conducted from Big Spring to Blue Hole spring. The travel time for peak dye concentration was 80 minutes. During a 6.35-cm rainstorm on March 19, 2002, total suspended sediment concentration (TSS), grain size, mineralogy, particulate organic carbon (POC), and discharge were measured at Blue Hole spring. TSS ranged from ~113 mg/L at 1.2 m3/s to ~975 mg/L at 2 m3/s. For suspended sediment POC varied from 3.7% to 6.1% and average grain size, determined by laser light scattering, ranged from 19 to 31 microns. Whole rock mineralogy of bed and suspended sediment is dominated by quartz; clay mineralogy is being determined. A dual quantitative trace with talc and Rhodamine WT from Big Spring to Blue Hole will be conducted to assess the mobility of clay particles during a subsequent storm.