MONITORING THERMAL AND GEOCHEMICAL DIFFERENCES OF TWO ADJACENT SPRINGS

Two karst springs in the Northern Appalachian Ridge and Valley Province of central Pennsylvania, Tippery Spring and Near Tippery Spring, emerge from the same folded carbonate bedrock less than 25 m apart but display differing thermal and geochemical patterns. First classified by Shuster and White (1971) as conduit-flow dominated but with slightly different geochemistry, the springs were later shown to have discrete capture zones with no apparent crossover based on dye tracing. These springs are currently being revisited with continuous monitoring data-loggers (temperature, pH) and base- and stormflow water sampling for geochemical analyses (major ions, alkalinity, rare earth elements [REEs]). Both springs show seasonal temperature variation, although Tippery shows more storm response than Near Tippery, indicating fast flow paths. Near Tippery has stronger REE anomalies and slightly higher alkalinity, indicating more water-rock interaction. Stormwater sampling was limited due to the dry season, but showed a contrast between the springs for one storm sampled. Tippery showed no hysteresis while Near Tippery showed hysteresis in Mg/Ca ratios during the storm. Variations in annual and storm-response thermal patterns, along with stormwater hysteresis, reflect conduit geometry. Both stormwater hysteresis and REE anomalies reflect water-soil-bedrock interaction. These differences in water temperature and chemistry are thought to result from the conduit geometry and geology specific to each springs’ recharge area. This new monitoring has shed light on the factors affecting physiochemical heterogeneity of spring water at this study site, and the potential for identifying source areas and flow paths at other karst springs.