Geohydrology and Regional Ground-Water Flow of the Coastal Lowlands Aquifer System in Parts of Louisiana, Mississippi, Alabama, and Florida: A Preliminary Analysis

摘要

The Coastal Lowlands aquifer system of Louisiana, Mississippi, Alabama, and Florida consists of alternating, discontinuous beds of sand, gravel, silt, and clay of Miocene age and younger. The sediments thicken and dip toward the Gulf of Mexico and are highly heterogeneous. The Coastal Lowlands aquifer system has been subdivided into five regional aquifers defined on the basis of water-level and pumpage data largely from heavily pumped areas. These aquifers from youngest to oldest are: the upper Pleistocene aquifer, the lower Pleistocene-upper Pliocene aquifer, the lower Pliocene-upper Miocene aquifer, the middle Miocene aquifer, and the lower Miocene aquifer. Electric logs of 279 wells were analyzed to construct maps of aquifer thickness, sand and clay content, and dissolved-solids concentrations of interstitial water. Analysis of the hydraulic characteristics of the regional aquifers indicates that the upper Pleistocene aquifer has the highest lateral hydraulic conductivity and the lower Miocene aquifer has the lowest. A six-layer finite-difference ground-water flow model was used to investigate and quantify the regional ground-water flow of the Coastal Lowlands aquifer system. The model was calibrated to match 1980 steady-state conditions.