VARIATIONS IN GROUND WATER CHEMISTRY IN HINDS AND MADISON COUNTIES, MISSISSIPPI
Two distinct groups of ground waters have been found in Madison County. Group one waters that have high (350 mg/L) total dissolved solids (TDS) occur at shallow depths (<250 m), and are restricted to the southeastern part of the county. Group one waters also display high concentrations of Cl, SO4, and Na. Group two waters have low TDS (100 mg/L), come from depths of 250 500 m, and are distributed throughout the county. Group two waters have low concentrations of Cl, SO4 and Na. In Hinds County, however, no distinct depth-related grouping is found relative to TDS, Cl, SO4, or Na. But, ground water compositions show major east-to-west variations. Groundwater having low TDS (>250 mg/L), Cl, SO4, and Na are found on the eastern part of county. But concentrations of all elements systematically increase westward in such a way that ground waters on the western edge of the county have TDS as high as 900 mg/L.
Surface and subsurface geological analysis of the two counties suggest that regional variations in groundwater compositions can be related to following: (1) the location of the recharge area, (2) geological processes around the Jackson dome, (3) rock water interaction with clastic-dominated aquifers, and (4) brine intrusion along faults.