Fossil Ground‐Water Gradients in Arid Regional Sedimentary Basins

Abstract

ABSTRACTThe hypothesis that present‐day ground‐water gradients in arid regional sedimentary basins are a decay feature of very old recharge mounds is examined using a resistance network analogue. A longitudinal section model of a conceptual basin with some specific control of aquifer permeability and ground‐water age is used.With reasonable combination of aquifer permeability and specific yield it is shown that an acceptable head decay could have occurred over the past 10,000 years to produce the present‐day gradient. In the model adopted, decreasing permeability with depth was found to be required to accord with 14C ground‐water age data.Although the model is not considered to be definitive for any particular aquifer the results show that fossil gradient conditions could exist in the regional basins for long periods and should be taken account of in ground‐water resources assessments.