# Geohydroology of a Reference Mediterranean Catchment (Cilento UNESCO Geopark, Southern Italy)
## 4 Discussion
All the events defined as ordinary fell within the boundary curves of the daily chart. The daily Q-EC analysis, performed by [7] on the same catchment, highlighted that the Ciciriello is characterized by a deep percolation mechanism that takes place in the bedrock and that constitutes the base of the stream flow (340 \(\upmu\)S/cm) during the dry period. During the initial phase of the wet season, the intense and short showers induced storm flow only from riparian corridors and impervious surfaces with short, peaked and opposite flood hydro-chemographs. After a prolonged rainfall, the sub-surficial runoff component, from regolith and infilling soil on the hillside and hollows, was added to the groundwater component as delayed return flow (Q-EC values ranging from 50 to 100 l/s and 100-120 uS/cm, respectively). During and just after the storm event, quick return flow from the topsoil added new water to the total storm flow (the lowest EC-Q values were 70-110 uS/cm): this represents the peak flow conditions during wet periods. This catchment behavior was confirmed by the 5-min event analysis performed on the Q-EC data using the chart. The compound event of the 14 th of February 2016 showed the system response during the wet phase, with a peak flow condition and the activation of topsoil with the fast return flow. The delayed response was the sub-surface flow from the regolith and infilling soil on the hillside and hollows. The single event that occurred on the 1 st March 2016 exhibited a progressive rise from a minimum flow to a well-defined peak of 750 l/s, after which there was a progressive return to zero. Its position in the hydro-chemograph analytical curves, with EC ranging between 120 and 160 uS/cm, confirmed that the catchment at the end of the rainy period was saturated [4] and the hydrologic response was sustained by groundwater ridging and sub-surface flow as main components. The event that occurred on the 23 rd of March 2016 was a single event with a peak discharge lower than 400 l/s that was not high enough to show the activation of the hillside and the hollow contribution. This event was affected by the antecedent soil moisture conditions of the 1 st of March. Its position on the chart was due to the deep aquifer (EC between 160 and 370 uS/cm) that started to sustain the hydrologic response of the system. The event of the 20 th of May 2016 was an isolated peak that occurred at the beginning of the dry period. A high ground water contribution was verified and the sub-surface flow acted as the faster response of the system activated from the nearest hillside and hollow to the riparian corridor. Figure 13 shows a schematic representation of the geohydrologic perceptual model of the Ciciriello, where only a portion of catchment was representing by a 3D scheme, including a generic hillslope-riparian corridor-channel transect during a peak discharge, both in dry and wet season. Detected natural geomorphic processes, that affect the hydro-chemograph response as material transfer by erosion and shallow landslides, are added. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Events** & **Event Type** & **Hydrologic Type Event** \\ \hline
16 February 14 & Ordinary & Compound event \\
16 March 01 & Ordinary & Ordinary \\
16 March 13 & Ordinary & Sub-event \\
16 March 23 & Ordinary & Ordinary \\
16 May 20 & Ordinary & Ordinary \\
16 September 14 & Affected & organic sediment \\
16 September 22 & Affected & pollution \\
16 September 19 & Affected & pollution \\
17 January 15 & Affected & snow \\
17 Febbraio 14 & Affected & snow \\
17 November 6 & Affected & Inorganic sediment \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Event types classification. The affected events, characterized, during a dilution phase, by a positive Q-EC relation or a constant EC value, were classified with respect to their origins: snow-melt, organic sediment and farmer waste.