Probing the Plumbing of Wakulla Spring: Instrumentation and Preliminary Results

Wakulla Spring is a first-magnitude spring fed by flow within a dendritic network of deep (~ 85 m below the water table) karst tunnels and having many notable hydrologic features, including flashy discharge, constancy of water temperature (less than 1°C) and strong tidal influence (observed in flow, temperature, electrical conductivity and water level). Beginning in 2004 an ambitious program, funded by the Florida Geological Survey and strongly supported by the Woodville Karst Plain Project, was launched to study and quantify flow and transport dynamics within this system, employing both oceanographic flow meters (measuring flow, temperature and electrical conductivity), water-level meters and tracing experiments. This paper describes a select few of the many interesting features of the system that have been revealed, illuminated and quantified by these instruments and experiments. Of particular interest is that the state of the flow system changes episodically; measurements of flow velocity within tunnels show distinct changes in mean speed, direction and variability, lasting typically several months, suggesting that the system may operate in as many as three distinct dynamic modes. Also, measurements of temperature suggest a hidden source of water for Wakulla Springs, not measured by the flow meters currently in place.