Hydrogeological study of Fethiye Girmeler Spa (Muğla) and surrounding area

The basement of the study area is the metamorphic rocks belonging to the Precambrian to the Triassic Menderes Massif. The Mesozoic rock assemblages of the Lycian Nappes and Beydağları autochthonous overlie the Menderes Massif rocks. Neogene terrestrial sediments overlie all these units unconformably. Quaternary alluviums are the youngest units in the field. The aquifers are the alluvium, carbonated rocks of the Lycian Napples and the Beydağları autochthonous and carbonates of the Neogene sediments. With this study, the chemical properties of the groundwater in the region have been investigated and the purposes for which they can be used were investigated. For the determination of pH, temperature and conductivity in hot and cold-water sources, in situ measurements were made with the help of multimeter. As per the results of major ion analysis of six water samples taken, hydrogeochemical processes such as water rock interaction are examined. The hardness values of the waters in the study area range between 4.40-8.70, while the temperature ranges between 9.8-36.5°C and the electrical conductivity (EC) values vary between 242-4150 μS/cm. With the Durov and Piper diagrams, it is determined that the waters are Mg-Ca-HCO3-SO4, Ca-HCO3-SO4 and Mg-Ca-HCO3 water types and cold water had similar chemical properties. As stated by Schoeller, it is found that the cold waters are normal chlorinated and normal sulphated and the hot waters are oligocluroric and oligosulphate respectively according to the amount of chloride and sulfate. Based on the amount of carbonate and bicarbonate, the waters are found to be usual carbonated. When the Wilcox chart and the US Salinity Laboratory diagram are examined, it is determined that the hot water in Girmeler region is not suitable for irrigation and cold water can be used in all kinds of irrigation. Keywords: Hydrogeology, hydrogeochemistry, geothermal, Fethiye, Girmeler