Abstract

Available water chemistry data collected between 1965 and 2013 from the Chicot and Evangeline aquifers in coastal South Texas were studied to identify time dependent depth variations and spatial differences in total dissolved solids (TDS) ground water level (GWL) and ground water TDS varied noticeably. This study analyzed correlation relationships among several water chemistry parameters and spatio-temporal variations in selected water chemistry parameters such as pH, Mg²⁺, and F⁻, at varying depths. Hydro-chemical analyses reveal that both the Chicot and Evangeline aquifers water are Na–K–Cl–SO₄ type, while the Evangeline aquifer showed higher proportions of Na⁺ and Cl⁻ compared to the Chicot aquifer, suggesting that the hydrogeochemical processes operating in those two aquifers differ significantly. Major ions such Na⁺, Cl⁻, SO₄²⁻, and F⁻ showed significant spatial and depth variations. In the deeper part of the Evangeline aquifer, SO₄²⁻ and F⁻ concentrations gradually increased with depth, while HCO₃⁻ and Ca²⁺ simultaneously decreased with depth. Time dependent spatial and depth variations of the concentrations of total dissolved silica, Ca²⁺, F⁻, and HCO₃⁻, along with ground water level fluctuations in the Chicot aquifer, suggest the hydrogeochemical processes are not in hydrodynamic equilibrium condition, but datasets with much higher spatial and temporal resolution would be required to establish this with sufficient confidence.