Abstract

In this study, the isotopic properties of the water resources located in Köprüören Basin are determined. δ18O and δD contents of the samples respectively ranged from -10.84‰ to -7.09‰ and from -73.6‰ to -53.3‰ in dry season and ranged from -10.81‰ to -4.71‰ and -73.3‰ to -41.5‰ in wet season. Majority of the samples plotted along Global Meteoric Water Line although some of them show deviations from this line. The reason for the deviations are attributed to evaporative enrichment, modifying the original δ18O and δD signatures of the samples. δ18O content of the thermal samples are not modified as a result of water-rock interaction due to low wellhead and reservoir temperatures. Tritium concentrations for all samples range from ~0 to 6 TU in wet season and from ~0 to 8 TU in dry season. Accordingly, some of the groundwater samples are recharged from modern precipitation, their groundwater residence times are short and they have shallow circulation. Besides, samples with tritium concentrations close to detection limits (thermal water samples and two of the groundwater samples) were recharged before tritium from nuclear weapon tests and have relatively higher residence times. These samples were also analysed for δ13C and 14C to get information about the residence times. δ13C ve percent modern carbon contents of five samples range from -5‰ to -14.6‰ and from 8.2 to 78 pmc, respectively. The corrected 14C ages for these samples are up to 11500 years before present, thereby indicating the presence of paleowaters in the basin. δ13C data indicate that 14C contents of the thermal waters were diluted as a result of water-rock interaction.

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