Hydrogeochemical investigation of groundwater in the Türkmentokat (Eskişehir) Region

This thesis investigates the hydrogeochemical and isotopic characteristics of some groundwater resources in the Türkmentokat (Eskişehir-Odunpazarı) region and their suitability for irrigation purposes. A total of 28 water samples were collected for the study. The pH values of the samples range from 7.4 to 8.1, electrical conductivity (EC) values range from 393 to 699 µS/cm, and temperatures vary between 16°C and 22.6°C. The waters are generally classified as CaMgHCO3 waters, which are believed to result from the dissolution of magnesium-rich minerals in the region's carbonates and ophiolitic rocks. The isotopic results show δ18O values ranging from -9.15 to -8.28 and δ2H values ranging from -68.25 to -63.95, while tritium values range from 0.35 TU to 0.77 TU. Mineral saturation index calculations reveal that most of the samples are saturated with dolomite, calcite, and aragonite minerals, while they are undersaturated with gypsum and anhydrite minerals. To evaluate the suitability of the waters for irrigation, parameters such as Kelley Ratio (KR), Soluble Sodium Percentage (SSP), Magnesium Hazard (MT), Permeability Index (PI), Sodium Adsorption Ratio (SAR), and Residual Sodium Carbonate (RSC) were calculated. According to the calculations, all the waters are suitable for irrigation based on the sodium adsorption ratio, Kelley ratio, soluble sodium percentage, and residual sodium carbonate parameters. However, based on permeability index values, samples 3W and 14D are classified as unsuitable for irrigation. Based on magnesium hazard values, all samples, except 1D, 7D, 18W, and 20W, are deemed unsuitable for irrigation. On the Wilcox diagram, the waters fall into the very good-good class, and on the USDA Salinity Laboratory diagram, they belong to the C2-S1 (medium salinity-low sodium hazard) class