Hydrogeochemical Evaluation of Groundwater in Lorestan Central Plain

The reduction in the quantity and quality of water due to over-cultivation and continued drought has caused irreparable damage to the groundwater resources of Lorestan province. The water levels have also dropped in the Central Plain, one of the large plains of the Khorramabad basin, which is the subject of this study. Water resource management is the most important and most strategic way to control this growing crisis. Hydrogeochemical assessment of the water resource is the first step in achieving this goal. For this purpose, the EC, pH and TDS parameters and the major anion and cation concentrations were measured in 40 samples well scattered within the aquifer. Ion ratios, saturation index and Gibbs, ion exchange and TDI graphs were used to determine the water quality and to define the factors affecting it. The Piper diagram shows that water samples from all parts of the aquifer contain Ca-HCO33 due to the distribution and diffusion of dissolved carbonate formations in the study area. The ion ratios indicate that the composition of water is influenced by the weathering of carbonate rocks, plagioclase minerals and, in the next stage, by direct and reverse ion exchange processes. Saturation indices show that due to the geological formations, the aquifer is undersaturated in gypsum, anhydrite, and halite minerals and oversaturated in aragonite, calcite and dolomite. The results of the Gibbs graph show that weathering is the dominant process in determining the water quality. Direct and reverse ion exchanges also affect the quality of water.