KARSTIFICATION AT BESKONAK DAM SITE AND RESERVOIR AREA, SOUTHERN TURKEY
Beskonak dam and hydroelectric power plant are planned to be constructed on the Koprucay river, 40 km east of the Antalya city. In the dam site and reservoir area, Koprucay Conglomerates of Miocene age and the Beskonak Formation (sandstone-claystone) alternating with each other crop out vertically. Koprucay conglomerates, with the components of limestone fragments and carbonate texture, are karstic and permeable, whereas the Beskonak Formation is impermeable. At the northern edge of the reservoir area, the Olukkopru karst springs discharge at a minimum of 30 m3/s. These springs discharge mainly through vertical and subvertical joint systems. Intensive superficial karstification developed along the joint systems and the terrane reveals columns of rocks, called ''fairy chimneys.'' Olukkopru springs represent the discharge point for a large and continuous system of underground solution cavities. In the Koprucay basin, there are numerous karstic features within the conglomerates. Within the reservoir area, Kurukopru cave, with a length of 530 m, is an example of these caves developed within the conglomerates. In some parts of the reservoir area, where the groundwater level is lower than the surface-river elevation, a highly developed karstification zone is present within the fluctuation range of groundwater between depths of 40 and 50 m. The above-mentioned Kurukopru cave is an active cave developed in the dam site and its vicinity. The solution conduits developed along the system of mostly vertical fractures and joints are interconnected, thus giving rise to a three-dimensional conduit network. On the other hand, a majority of these conduits have clay and calcite filling materials. Karstification in the dam site varies with depth exponentially. Data suggest that karstification has a vertical extention as deep as -220 m.