# Geohydroology of a Reference Mediterranean Catchment (Cilento UNESCO Geopark, Southern Italy)
## 1 Introduction  
The Mediterranean river eco-system equilibrium greatly depends on aquifer feedings and surface-groundwater functional interactions [1]. The assessment of their ecological services requires interdisciplinary approaches, the integration of monitoring systems and inter-institutional planning and management. This complexity is particularly evident in protected areas, where institutional protocols (e.g., derived from the European Water Framework Directive WFD, [2]) require the implementation of appropriate activities related to geodiversity-biodiversity relationships [3]. In these areas, the biodiversity protection and conservation have to be guaranteed by the structural integrity and functionality maintenance of the hydro-geodiversity, addressed toward integrated actions in best practice management, effective disaster mitigation and human health preservation. In order to support the institutional issues for the risks and resources assessment and management of the Cilento, Vallo Diano and Alburni National Park, in the 2015 recognized UNESCO GlobalGeopark, a research program was planned based on extensive hydro-geomorphological surveying and hydro-chemical monitoring activities. The above integrated activity was first set up in the highly karst-conditioned Upper Bussento river basin by the interdisciplinary research group of the Department of Civil Engineering and C.U.G.RI., working at the University of Salerno [4; 5; 6; 7; 8]. Successively, the research areas were extended to other selected catchments located in different landscapes of the Geopark, focusing on the complex karst carbonate systems and small, forested, no-karst (sandstone and marly clayey complexes) headwater catchments of the Geopark. The first results of this research program were illustrated in [7; 9], highlighting promising aspects in further studies and addressing a few case studies that were managed as experimental catchments. One of these was the 3-km\({}^{2}\) Ciciriello Torrent experimental catchment (Caselle in Pittari Municipality), where, since December 2012, hydro-geomorphological surveying has been performed and a hydro-chemical monitoring program started and is currently ongoing [4; 5; 6; 7; 8; 10; 11; 12]. The basic tool for studying the response of basins or catchments to precipitation events is a two-component--surface and base flow--analysis of the total stream discharge variation over time, plotted as a storm flow hydrograph. However, there is increasing evidence that observed hydrograph patterns can be explained as a complex of hydrological processes where both new and old waters are collected from the hillsopes, conveyed into the drainage network and delivered to the stream channels through an extension and reduction mechanism of the contributing areas, which progressively provide contributions from different source areas [13]. Therefore, the separation of surface runoff from the observed hydrograph depends on several physiographic and meteorological variables (i.e., watershed area and morphology, soil and rock properties, storm recurrence and seasonality, antecedent moisture conditions, vegetation and land use). In order to separate the streamflow components and identify components of the above sources and pathways, many authors have extensively employed chemical and isotopic tracers in experimental parcels or small watershed. The underlying idea is to use the geochemical or isotopic signature of the water at the small catchment scale. Among others, basic physical-chemical parameters including electrical conductivity (EC) were extensively used as proxy parameters for the total dissolved solids (TDS) in the streamflow [14; 15]. While EC in the streamflow is not considered a conservative tracer [16], it has been used as a tracer for hydrograph separation for decades [17; 18; 19], due to its practical and effective advantages.