SEASONAL SPRING WATER TEMPERATURES AS A TRACER FOR EVALUATING SURFACE IMPACTS TO SPRINGS

Storm events are often used as indicators of surface input to karst springs but seasonal patterns can also reflect the thermal interactions along flow paths in karst systems. Propagation of regional thermal signals in springs is directly related to the connection of the spring to the surface. Thermal equilibrium and the closeness of the surface-subsurface connection are controlled by recharge type, subsurface flow regime, storage water-surface water exchange, and spring shed size. These parameters vary between aquifers and between springs within the same aquifer. An inexpensive means of evaluating the surface connection – and thereby evaluating the vulnerability of the spring to surface activities - is long-term temperature data at springs. In this study we evaluated annual thermal response in six clastic and four carbonate springs in Monroe County, WV. A cosine model was applied to each spring to determine seasonal patterns. Cosine models were also fit to daily air temperature (a proxy for recharge temperature). Amplitude dampening factors were calculated based on the ratio of the modeled amplitude for air temperature to the modeled spring temperature. Lag times in thermal response represent the difference in time from maximum air temperature to maximum spring temperature. Lower amplitude dampening factors and lag times indicate spring thermal signals that are more similar to recharge temperatures and thus interpreted as having a closer surface connection. Amplitude dampening factors ranged from 4.0-23 in the carbonate springs and from 9.0-64 in the clastic springs. Lag times ranged from 32-45 days in the carbonate springs to 6-83 days in the clastic springs. Generally, springs in this study show seasonal thermal fluctuations which could be an indication surface influences on spring water quality.