HYDROGEOLOGY OF THE GOKPINAR KARST SPRINGS, SIVAS, TURKEY

Abstract

Fikret Kacaroglu: Hydrogeology of the Gokpinar karst springs, Sivas, Turkey Gokpinar karst springs are located 8 km to the south of the Gurun district centre, Sivas, Turkey. The springs have two main outlets (Gokpinar-1 and Gokpinar-2) and outflow from Jurassic-Cretaceous Yuceyurt formation (limestone). The total discharge of the springs ranges between 4.5 and 7.8 m(3)/s. The study area is formed of allocthonous and autocthonous lithological units whose ages range from Upper Devonian to Quaternary. These lithologies are mostly formed of limestones. Yuceyurt formation (limestone), from which Gokpinar karst springs outflow, constitute the main aquifer in the study area and is karstified. The unit has a well developed karst system comprising karren, dolines, ponors, underground channels and caves. The recession (discharge) analysis of the Gokpinar springs was carried out and the storage capacities and discharge (recession) coefficients of the Gokpinar-1 and Gokpinar-2 springs were calculated as 141x10(6) m(3) and 98x10(6) m(3), and 2.71x10(-3) day(-1) and 2.98x10(-3) day-1, respectively. The storage capacities and discharge (recession) coefficients obtained suggest that the karst aquifer (Yuceyurt limestone) has large storage capacity, and drainage occurs very slow. The major cations in the study area waters are Ca2+ and Mg2+, and anion is HCO3-. The waters are calcium bicarbonate type. Some of the water chemistry parameters of the Gokpinar springs range as follows: T=10.8-11.1 degrees C, pH=7.65-7.95, EC=270-310 mu S/cm, TDS=170-200mg/L, Ca2+=40.0-54.0mg/L, Mg2+=4.5-10.0 mg/L, HCO3-=144.0-158.0 mg/L. Temperature, EC, TDS, and Ca2+ and HCO3- concentrations of the Gokpinar springs did not show significant variations during the study period.