ADAPTING FIBER OPTIC DISTRIBUTED TEMPERATURE SENSING TO CAVE STREAM ENVIRONMENTS: HYDROLOGIC MONITORING OF TUMBLING ROCK CAVE, AL

Fiber optic distributed temperature sensing (FO-DTS) is an emerging technology for environmental applications, allowing for continuous temperature measurements at fine spatial resolutions. Cave streams are unique and dynamic environments where such measurements are incredibly useful, but DTS use in caves is largely unexplored due to inaccessibility and complex field logistics. In partnership with the Southeastern Cave Conservancy and Center for Transformative Environmental Monitoring Programs, this study took advantage of the untapped potential of FO-DTS for the characterization of subsurface karst hydrology with a pilot project at Tumbling Rock Cave, Alabama. Work was aided by previous research encompassing LiDAR mapping, air temperature monitoring, water quality analysis, rock-water interactions studies, and a stream survey. Our research goals were to monitor flood events in response to local precipitation, identify inflow locations based on temperature differences, and overall explore surface water-groundwater interactions. Our team installed 933 meters of dual-channel armored fiber optic cable measuring temperatures of the cave stream, cave air, resurgence, and surface from March 2nd to May 12th, 2024. Four independent water temperature sensors were also placed for calibration with ambient and controlled temperature baths. The first three weeks of data were calibrated in MATLAB and analyzed with the USGS DTS GUI. Preliminary results show marked differences in cave vs. surface and stream vs. air temperature patterns, a strong relationship between surface precipitation and warm cave inflows, and the ability to track propagation of storm water entering the cave. We expect this study to provide methodologies to adapt FO-DTS use to caves, improve our understanding of karstic water interactions, characterize the stream system, help mitigate flood risks, and improve management strategies.