Hydrogeological investigation of the Gökpinar karst springs (Gürün-Sivas) [Gökpinar karst kaynaklarinin (Gürün-Sivas) hidrojeoloji incelemesi]
The Gökpinar Karst Springs are located 8 km to the south of the town of Gürün, Sivas, in Turkey. The springs issue from a Jurassic-Cretaceous Yüceyurt formation (limestone) and have two main outlets. The total discharge of the springs ranges between 4.5 and 7.8 m3/s. This study aims at determination of the hydrogeology, discharge regime and water chemistry of the Gökpinar karst springs. The Yüceyurt formation (limestone), from which Gökpinar karst springs issue, constitutes the main aquifer in the study area. The unit has a well developed karst system comprising karens, dolines, ponors, undergound channels and caves. The recession (discharge) analysis of the Gökpinar springs revealed that the karst aquifer (Yüceyurt limestone) has large storage capacity and low transmissivity. The total storage capacity of the springs is 239×106 m3, and the discharge (recession) coefficient is 2.83×103 day1. The major cations in the waters of the study area are Ca2+ and Mg2+, and the major anion is HCO3-1. The waters are of a calcium bicarbonate type. Some of the water chemistry parameters of the Gökpinar springs range as follows: T=10.8-11.1 °C, pH=7.65-795, EC=270-310 ?S/cm, TDS=170-200 mg/l Ca2+=40.0-54.0 mg/l, Mg2+=4.5-10.0 mg/l, HCO3-1=144.0-158.0 mg/l. The waters are suitable for domestic use. They have medium salinty hazard and a low sodium (alkali) hazard in terms of irrigation water use, and plot in the C2S1 class in the USA Salinty Laboratory irrigation water classification diagram.