HYDRAULIC CONDUCTIVITY ACROSS A RANGE OF HILLSLOPES IN THE LITTLE TENNESSEE RIVER WATERSHED

A number of variables impact the calculated hydraulic conductivity of subsurface medium. These values are especially important in the Southern Appalachians of southwestern North Carolina, where viable permeabilities will affect infiltration rate, discharge rate, and soil moisture capacity. This research took place at the Coweeta Hydrologic Laboratory in Otto, NC and in other locations in the Little Tennessee watershed. Slug tests were performed on 28 shallow monitoring wells to determine hydraulic conductivities in multiple landscape positions and geological formations in Southern Appalachian watersheds. The goal was to determine the factors that significantly affect hydraulic conductivity. The determinants for the research sites included (1) forested versus agricultural, (2) gneiss versus schist bedrock, (3) steep versus gentle slope, and (4) proximity of the well to the nearest stream. Raw data collected from the slug tests showed a steady rate of recovery in all but two of the 28 wells. Using Kruskall Wallis tests to assess differences among spatial variables, it was determined that the only variable having a significant impact on hydraulic conductivity was the proximity of the well to the nearest stream. This could be due to the depositional environment found closer to the stream. A number of variables may explain why the remaining three factors did not have a significant impact on hydraulic conductivity. There may be no difference between forested and agricultural sites because land use has not affected soil physical properties at depth. With similar mineral compositions, both gneiss and schist may weather at a comparable rate, making any differences in hydraulic conductivities inconsequential. Hydraulic conductivities from this experiment will be combined with hydraulic gradients from continuous monitoring of water levels along hillslopes to determine specific discharge from each hillslope into the stream. Time series of specific discharges will help researchers understand how hydraulic conductivity and hydraulic gradient interact to influence patterns of runoff in the Southern Appalachians.