Evaluation using geographic information systems of the hydrogeochemical characteristics of groundwater resources in the Aksaray region

In this study, the hydrochemical properties of groundwaters from Aksaray area were investigated using Geographic Information System. The 64 water samples from varies wells in the region were collected in order to evaluation of the groundwater quality. Sampling was performed in September 2015 and May 2015. Units which characterized aquifers in the study area include the Paleozoic marbles with high crack and fracture contents, Tertiary marine and terrestrial clastics which generally consist of alternations of sandstone and conglomerate, karstic limestone with high fracture content, and Quaternary alluvium with levels of unconsolidated sand and gravel. The some parameters of the water samples in May and September sampling period are: pH (5.89 - 8.92) (5.91 - 8.49), electrical conductivity (EC) (158.62 – 3625.20) (139.81 – 2789.39) µS/cm, total dissolved solids (TDS) (122.57 – 2676.50) (119.78 – 2513.44) mg/L, respectively. The water samples have Ca-HCO3, Na-HCO3, Mg-HCO3 and Na-Cl water facies feature. The dominant water type present in groundwater is the Ca-HCO3 type. Ca2+ and HCO3- are dominant ions in groundwater. The order of relative abundance of major ions are; Ca2+ > Mg2+ > (Na++K+) / HCO3- > Cl- > SO4-2. Ion abundances for many sampling points have remained the same during the whole sampling seasons. Hovewer, the ion sequencing of some waters have changed due to climate conditions. 26 wells are not suitable for drinking due to the arsenic concentration. Groundwaters are not saturated with gypsum, halite and anhydrite according to their general hydrogeological characteristics during all sampling periods and these minerals can be solved. At the same time, groundwaters are saturated with calcite, dolomite, aragonite and have the ability to precipitate in terms of these minerals. The areas that have lower water quality are located in the western and inner parts of the region. Lower groundwater quality is observed, especially toward the Lake Tuz.