ABSTRACT: Karaali hot water is located 32 km south-eastern of Þanlýurfa Province, in Karaali Village at the eastern part of Yardýmcý County. Drilling logs show that the hot water is obtained from limestone used extensively for production of cold water. It has been considered that ascending hot water throughout these fault lines is spreading in to limestone aquifer by mixing with cold water, and because of this process temperature of hot water is decreased. Determination of the temperature of Karaali hot water before mixing has been purposed by this investigation. In the scope of that, mixing percentage of the hot and cold waters has been determined by using of the water chemistry data in silica-enthalpy mixing model (SEMM) and Cl-enthalpy graph. Initial (before mixing with cold water) chemical composition of Karaali hot water has been determined by this mixing percentage. Estimated reservoir temperature (ERT) of the hot water has been calculated by using of the initial chemical composition in silica and cation geothermometers. Calculated ERT (132°C) by silica-enthalpy mixing model (SEMM) is quite harmonious with the average of the Na-K and SiO geothermometers` results (138°C and 132°C, respectively) which were applied to 18% hot and 82% cold water mixing. The ERT and mixing percentage of hot water inspected by SEMM, mixing calculation and geothermometers has to be supported by the other investigations including detail mapping, geophysical investigations, detail water chemistry etc.