Water and Air Flows in Karstic Caves and Conduits

This dissertation seeks to understand physical processes in submerged and dry caves in Florida. First, for submerged caves, we prove the possibility of an upward saline water intrusion due to the Venturi effect occurring in a submerged cave's restrictions, i.e. narrow connections between two otherwise large tunnels. A model is developed to obtain an analytical solution for estimating the saltwater discharge through caves into freshwater aquifers. Additionally, Florida springs are examined, and the saltwater discharges due to the Venturi effect are calculated to be between 0.02 to 0.23 m3/s, which is significant especially for the springs with a mean annual freshwater discharge of less than 10 m3/s. Second, in an effort to develop a deeper understanding of dry caves, the microclimate of the so-called Dragon's Tooth Cave is examined. The ventilation patterns are analyzed by using in-situ measurements of temperature, CO2, and Radon-222. Estimated cave air renewal times vary from 2.4 days at the Entrance room to 6.6 days at the Dragon's Belly room. Next, a theoretical model is developed that uses outside temperatures to predict ventilation rates. Combined with simple first-order CO2 and Radon-222 mass balances, the model predicts net CO2 and Radon-222 concentrations in the cave, and shows an excellent agreement with the measurements.