Karstbase Bibliography Database

Acoustic televiewer (ATV) images, flowmeter, and borehole geophysical logs obtained from the open intervals of deep test wells were used to develop a revised conceptual model of groundwater flow for the Floridan aquifer system in northeastern Florida and southeastern Georgia. Borehole information was used to identify and map the types and distribution of highly-transmissive production zones in the Floridan aquifer system. The ATV images and flowmeter traverses indicate that water produced from most wells is largely derived from a system of highly-transmissive solution zones formed along bedding planes and major formational contacts. These “horizontal bedding-plane conduit systems” may locally influence the movement of brackish and saline water in the Floridan aquifer system. A modified conceptual model of regional flow in the Floridan aquifer system is proposed that incor-porates locally interconnected horizontal conduit systems within the largely porous matrix rock (fig. 1). Each of the conduit systems represents a highly-transmissive zone along which water can move preferentially through the aquifer system. These may or may not be laterally continuous across the area. Flow paths within the system are restricted vertically by local or regional confining units except where these are breached by collapse features or vertical fractures. Near major pumping centers, water probably moves preferentially along the horizontal conduits to reach the discharging well. The source of water moving into the transmissive open conduits is either derived from upward migration along vertical discontinuities in the rock or from diffuse leakage from adjacent porous rock units. Some trapped relict water in adjacent lower-permeability units may locally contribute to the higher chloride concentrations observed in some wells