Hydrogeological and speleological characterization of a karstic spring: the Cokragan cave system

Karstic landscapes, shaped by water dissolving rocks, are unique ecosystems with complex water systems. Karst aquifers, vital for over 25% of the world’s drinking water, offer a sustainable resource but are vulnerable, such as pollution and over-extraction. Therefore, it’s important to understand the potential and capacity of karst springs in areas suffering from water shortages. Hydrogeological and speleological studies are crucial for understanding the unique characteristics of karst springs. Moreover, epiphreatic caves located near the water table at the interface between vadose and phreatic zones in karst landscapes, hold valuable information about past geological events. By identifying their former presence and location in uplifted limestone regions, we can reveal phases of uplift, lowering of the base level, and the rate of vertical karst development. Consequently, epiphreatic caves and associated karst processes are of considerable interest for understanding past geological changes. Here, we present an integrated study of a spring in the epiphreatic Cokragan Cave, which is an important water resource for the Uşak region, using both speleology and hydrogeology. The complex Cokragan Cave system, stretching over 2050 m, reveals multiple past groundwater levels through its geometry, with elevation differences suggesting tectonic influence. Between 2003 and 2007, Cokragan spring discharged an average of 63.5 million m 3 /yr, while recharge averaged 62.37 million m 3 /yr. Measured discharge ranged from a maximum of 1.488 m 3 /s to a minimum of 0.108 m 3 /yr. In-situ measurements and analysis of 13 samples revealed the groundwater’s physicochemical characteristics, including major ions such as calcium, magnesium, and bicarbonate, and trace elements such as arsenic, boron, iron, manganese, and zinc.