UTILIZING CONSERVATIVE AND NON-CONSERVATIVE TRACERS TO ESTIMATE CONDUIT GEOMETRY: PRELIMINARY RESULTS FROM EXPERIMENTS AT SAVOY EXPERIMENTAL WATERSHED, NORTHWEST ARKANSAS (USA)

Karst formations are characterized by dissolution features and conduits (e.g. caves and sinkholes) which determine groundwater recharge, flow paths, and discharge. These conduits might intercept and transport contaminants within karst aquifers. Thus, understanding the groundwater flow paths of potable water is important in determining the water quality and logistics of a network for optimal land-use practices and developing sustainable systems.The Savoy Experimental Watershed (SEW) is a University of Arkansas collaborative research site situated on the mantled karst of the Springfield Plateau in Northwest Arkansas, which contains a relatively simple conduit network featuring a sinking stream flowing to two springs. The goal of this research is to use conservative and non-conservative tracers to model the conduit geometry from the sinking stream to the two springs by simulating thermal damping in a cylindrical model with assumptions and simplifications of the conduits. The existence of a clear input and outputs allows for analysis of temperature, conductivity, and water-level. We will compare seasonal and short-term thermal patterns, and we will determine residence time of the water by utilizing conservative tracers such as salt and dye. Preliminary data from a dye-trace test exhibited a residence time of our base-flow spring was approximately 9 hours long and 3 hours less than the residence time of the overflow spring (12 hours). Future work will include a joint thermal pulse and salt injection to compare residence times during the late-summer season as well. By juxtaposing data from non-conservative thermal— accounting for seasonal thermal variability— and conservative salt and dye tracers, this conjunctive approach will provide new quantification and insights at SEW, which could inform the modeling of other karst conduits.