Hydrogeochemical and isotopic evaluation of the hydrogeological system at Ceyhan-Berke damsite, Turkey

High Berke Dam being constructed on the Ceyhan river in southeastern Anatolia is situated at the triple junction of the Anatolian and Arab Plates. The damsite and its reservoir area are covered by carbonate rock masses of Mesozoic age, where tectonics is the effective factor controlling karstification. The Haruniye thermal karst springs emerge along a major fault extending to about 1 km downstream of the dam. The hydrogeological feasibility of the dam has long been a matter of debate regarding the hydrological relationship between surface and subsurface waters. Surficial karst features are rare in the area; however, evidences of thermal karstification indicate that intensive karstification was developed beneath the surface. Randomly scattered karstic conduits and caverns were located during the exploratory drilling at the damsite, which makes it difficult to assess the input-output relationships without the help of hydrochemical and isotopic data. In this study, the authors attempted to determine the origin and evolution of the downstream karst springs and to explain the hydrological system in the area. Regarding the hydrogeological feasibility of the Berke Dam, it is concluded that problems are likely to arise in relation to karstification in the form of water leakage through the reservoir area toward the downstream karst springs along both the shallow and deep circulation systems. Randomly scattered solution conduits characterizing the thermal karstification should be taken into consideration in designing the grouting curtain to provide water tightness at the damsite.