Digital model evaluation of the predevelopment flow system of the Tertiary limestone aquifer, Southeast Georgia, Northeast Florida, and South South Carolina

Abstract

A computer model using finite-difference techniques was used successfully to simulate the predevelopment flow regime within the multilayered Tertiary limestone aquifer system in Southeastern Georgia, Northeastern Florida, and Southern South Carolina as part of the U.S. Geological Survey 's Tertiary Limestone Regional Aquifer System analysis. The aquifer, of early Eocene to Miocene age, ranges from thin interbedded clastics and marl in the updip area to massive limestone and dolomite 1,500 feet thick in the downdip area. The aquifer is confined above by Miocene clay beds, and terminates at depth in low-permeability rocks or the saltwater interface. Model-simulated transmissivity of the upper permeable zone ranged from about 1 x 10 super 3 foot squared per day in the updip area and within parts of the Gulf Trough (a series of alinement basins filled by fine clastic in material) to about 1 x 10 super 6 foot squared per day in South Georgia, and area having large secondarily developed solution channels. The model results indicate that only about 540 cubic feet per second of water flowed through the predeveloped system, from the updip highland area of high altitude and in the areas north of Valdosta and southwest of Jacksonville, to discharge along streams in the updip area and diffuse upward leakage in the downdip area near the coast and offshore. (USGS)