Knowledge of surface water / groundwater interactions in high mountain karst regions is crucial for enhancing the protection and management of water resources. This is particularly relevant when dealing with mountainous areas located in the Mediterranean region, such as Sierra de Segura (SE Spain), one of the largest carbonate outcrops (3000 km2) in the Iberian Peninsula. This region acts as headwater of rivers flowing eastward (Mediterranean Sea) and westward (Atlantic Ocean) over Cretaceous-Tertiary limestones and dolostones. However, information on the surface water-groundwater interactions in rivers and streams found in the area is still limited, as well as their role in the functioning of the carbonate aquifers. This research shows the preliminary results obtained from hydrological (flow-rate) and hydrochemical records (electrical conductivity -EC-, temperature, major ions, total organic carbon -TOC-, dissolved gases -O2 and 222Rn-) measured along two of the main rivers in the area (Segura and Zumeta). 218 discharge and physico-chemical parameter measurements were carried out during the