MULTI-SCALE ASSESSMENT OF GROUNDWATER VULNERABILITY TO POLLUTION: STUDY CASES FROM CAMPANIA REGION (SOUTHERN ITALY)

In the Campania region (southern Italy), assessment of groundwater vulnerability is an important factor to be tackled for a proper management of risk to aquifer pollution, which is fostered by both high dependence of aqueduct systems on groundwater resources and the widespread agricultural and urbanized land uses of the territory. The different physiographic, geological and hydrogeological conditions of the region, coupled with high anthropic pressure, make such assessment complex to be dealt with, but at the same time mandatory to be accomplished. The proposed study has been developed into the framework of the “Campania Trasparente” project, which has been funded by the regional government to assess environmental factors controlling the quality of agricultural and livestock food productions. Specifically, it belongs to the research topic regarding the assessment of groundwater quality, with a special focus on the assessment of groundwater vulnerability. In this research a multi-scale approach for the assessment of groundwater vulnerability is carried out in order to propose suitable methods depending on extension of territory to be studied and related types and spatial density of available data. Scales considered were a) regional, including the whole Campania region; b) intermediate, identified with that of a single representative aquifer; c) site-specific, or local, related to a portion of aquifer for which a high spatial density of data is available.The applied methods were chosen among the many known in literature and adapted to the specific study cases. At the regional scale, the parametric SINTACS method (CIVITA & DE MAIO, 2000) has been applied to the whole region and adapted to types and spatial density of available data. At the intermediate scale, or aquifer scale, the Mt. Terminio karst aquifer was chosen as representative for the application of different parametric methods, also specifically designed for karst aquifers. At the site-specific scale, a representative sector of a shallow alluvial aquifer, located in the adjoining Casalnuovo di Napoli-Volla municipalities, in the Campania plain, at the eastern border of the city of Naples, has been studied by numerical modeling for the estimation of travel time of nitrate pollutant through the vadose zone. The obtained results can be conceived as useful for supporting a proper territorial planning aimed at the management of risk to pollution of groundwater resources

Caratterizzazione e modellazione dei processi di ricarica degli acquiferi carbonatici dell’Appennino meridionale. Il caso di studio della dorsale carbonatica dei Monti Soprano-Vesole-Chianello

Le acque sotterranee immagazzinate e trasferite dagli acquiferi carbonatici costituiscono una preziosa fonte di alimentazione per le grandi aree urbanizzate del mondo. Tali risorse sono principalmente utilizzate a scopo idropotabile, ma sono largamente impiegate anche in ambito agricolo ed industriale. Esse sono di cruciale rilevanza non solo per lo sviluppo socio-economico del territorio, ma anche per la conservazione degli ecosistemi fluviali, terresti e costieri che dipendono dalle acque sotterranee (Goldscheider, 2012). Attualmente si sta osservando un progressivo depauperamento qualitativo e quantitativo delle risorse idriche sotterranee conseguente a fenomeni di sovrasfruttamento e inquinamento generalizzato. È evidente che tali risorse devono essere ben tutelate anche perché, a causa della continua antropizzazione del territorio, che costituisce la principale fonte di contaminazione degli acquiferi, sono sempre più esposte a diffusi fenomeni di inquinamento (Cusano et alii, 2019; Tufano et alii, 2020). Inoltre, gli acquiferi molto carsificati presentano caratteristiche tali da esercitare uno scarsissimo contrasto alla propagazione degli inquinanti per l’elevata velocità del flusso e la scarsa capacità di autodepurazione. Pertanto, considerata la loro importanza strategica per l’approvvigionamento idrico attuale e del futuro, sono da ritenersi necessarie la stima della ricarica e la determinazione dei fattori che influenzano tali processi, al fine di garantire un uso sostenibile della risorsa idrica sotterranea. La presente tesi di dottorato è stata sviluppata nell’ambito del progetto internazionale MedWater (http://grow-medwater.de/home/), finanziato dal Ministero Federale dell'Istruzione e della Ricerca (BMBF) della Germania con l’obiettivo di giungere ad una gestione ottimale delle risorse idriche sotterranee degli acquiferi carbonatici in area mediterranea. È stata elaborata una procedura di studio per la caratterizzazione degli acquiferi carbonatici con particolare riferimento alla definizione del modello idrogeologico concettuale e l’analisi dei principali fattori che influenzano i processi di ricarica. Tale approccio innovativo è stato applicato al sito sperimentale che alimenta la sorgente Capodifiume (Capaccio, Provincia di Salerno, Italia meridionale), coincidente con il bacino sotterraneo della dorsale carbonatica dei Monti Soprano-Vesole-Chianello, rappresentativa di un’ampia porzione dell’Appennino meridionale. Gli approcci metodologici sviluppati, basati su attività di rilevamento in campo ed analisi di laboratorio, hanno permesso di avanzare le conoscenze sul ruolo idrogeologico delle coperture pedogenizzate (suoli) sui processi di ricarica degli acquiferi carbonatici. A tal fine è stata effettuata una caratterizzazione del sistema idrogeologico superficiale coperture-substrato carbonatico, identificando diverse tipologie di coperture di suolo, principalmente suddivise in aree ad intera copertura boschiva ed aree denudate. L’analisi degli spessori di suolo misurati in campo ha consentito l’elaborazione della mappa della tipologia di coperture di suolo dell’acquifero campione e la ricostruzione di una mappa stocastica degli spessori di depositi di copertura. Mediante analisi di laboratorio sono state ricavate le principali proprietà fisiche ed indice dei suoli campionati, classificati come sabbia con limo (SM) secondo il sistema di classificazione USCS. Sono state altresì stimate le proprietà idrauliche nei dominii della saturazione e sottosaturazione, determinando rispettivamente la conducibilità idraulica satura, Ksat, attraverso l’applicazione dell’equazione di Saxton (Saxton et alii,1986) e le Curve di Ritenzione Idrica del suolo (SWRCs) i cui parametri sono stati elaborati mediante modello di van Genuchten (van Genuchten et alii,1980). Inoltre, la definizione del modello idrogeologico concettuale, ottenuto attraverso l’applicazione di metodologie specifiche 2D e 3D, il monitoraggio dei valori di portata della sorgente Capodifume con frequenza circa mensile nonché il monitoraggio delle variazioni dei contenuti d’acqua dei depositi di copertura pedogenizzati, hanno permesso di valutare i principali fattori idrogeologici che influenzano i processi di ricarica dell’area in esame e implementare un modello di bilancio idrologico del suolo. Di particolare rilevanza tra i principali risultati ottenuti, sono da considerare le differenti aliquote di evapotraspirazione, osservate mediante monitoraggio, per le diverse tipologie di coperture di suolo. Questa osservazione ha consentito una tipizzazione del ruolo idrologico di dette coperture sui processi di ricarica, evidenziando una differente profondità alla quale si risentono gli effetti dell’evapotraspirazione. Ciò ha permesso di realizzare una mappa della riserva idrica utile disponibile, ai fini del bilancio idrico del suolo, per l’intera dorsale carbonatica indagata. L’applicazione del codice Soil Water Balance (SWB 1.2), sviluppato dall’USGS, ha permesso di effettuare una valutazione spazio-temporale della ricarica, validato mediante l’applicazione del bilancio idrico del suolo proposto da Thornthwaite-Mather (1957). Inoltre, la stima dei coefficienti noti in letteratura (EIC, Coefficiente di Infiltrazione Efficace, e AGRC, Annual Groundwater Recharge Coefficient, Allocca et alii, 2014), ha permesso di definire il diverso contributo delle tipologie di copertura individuate in termini di evapotraspirazione. Le maggiori aliquote di evapotraspirazione ricavate per le aree boschive e, al contrario, tassi più bassi di evapotraspirazione ottenuti per le aree denudate, sono in accordo con il modello clima-suolo-vegetazione presente in letteratura (Rodriguez-Iturbe et alii, 1999), secondo il quale le coperture boschive riducono il contenuto d’acqua del suolo mediante evapotraspirazione, causando una conseguente diminuzione della ricarica delle falde idriche sotterranee. Il presente lavoro consente di definire nuove linee di ricerca circa la quantificazione dei fattori che influenzano i processi di ricarica degli acquiferi carbonatici, con particolare riferimento al ruolo delle coperture di suolo sulla caratterizzazione di tali processi. I risultati raggiunti sono da ritenersi di particolare rilevanza scientifica in quanto rappresentano un avanzamento delle conoscenze idrogeologiche che, per gran parte degli acquiferi dell’Appennino meridionale, risultano essere di limitato grado di approfondimento e non sufficienti all’applicazione di modelli avanzati per la stima della ricarica in relazione a scenari di cambiamento climatico. Infine, gli approcci metodologici descritti sono da considerare esportabili ad altri acquiferi carbonatici che presentano condizioni tipiche riscontrabili in Appennino meridionale

Complex Rainfall-Driven Kinematics of the Slow-Moving Pisciotta Rock-Slide (Cilento, Southern Italy)

The Pisciotta landslide is a slow-moving deep-seated rock slide in the Cilento region (southern Italy), which involves in the middle of its body a provincial road causing continuous interruptions of vehicular traffic. It also represents a danger for two railway tunnels crossing its foot. The landslide affects a complexly folded and tectonized turbidite series composed of intercalated calcarenites, marls and mudrocks. The principal objective of this study was the kinematic analysis of the landslide and its relationship with rainfall patterns. The analysis was based on monitoring of ground deformations carried out on 50 optical targets by topographical techniques. The latters were distributed in the middle-upper part of the landslide body, in order to set an early warning system for the provincial road. The monitoring activity was performed in the periods August 2005–March 2010 (1699 days) and May 2011–September 2013 (721 days). Besides the analysis of basic kinematic parameters, such as displacement, direction of movement and velocity, also the strain field was modelled and analyzed through the SSPX numerical code. Among principal results, spatial distribution of displacements, velocities and deformation patterns revealed a strong coherence with the detected surficial structures of the landslide. Moreover, the coupled spatial and temporal variability of deformation patterns allowed understanding a complex kinematics of the landslide body whose movements were related to a series of interacting blocks of flysch rock-masses. The analysis of the temporal variability of the landslide kinematics revealed uncommon findings such as that the landslide was always in motion (active) in the observation periods, with velocities ranging from the very low to low classes. Maximum velocities were observed unexpectedly in summer, during the dry period. Cross-correlation analyses performed between mean landslide velocity and rainfall time series showed a delay of about six months

Seasonal and Event-Based Hydrological and Slope Stability Modeling of Pyroclastic Fall Deposits Covering Slopes in Campania (Southern Italy)

The pyroclastic fall deposits mantling mountain slopes in the Campania region (Southern Italy) represent one of the most studied geomorphological frameworks of the world regarding rainfall-induced debris flows threating urban areas. The proposed study focused on advancing knowledge about the hydrological response of pyroclastic fall coverings from the seasonal to event-based time scales, leading to the initiation of slope instability. The study was based on two consequential tasks. The first was the analysis of a six-year monitoring of soil pressure head carried out in a sample area of the Sarno Mountains, located above a debris flow initiation zone. The second was based on coupled hydrological and slope stability modeling performed on the physical models of slopes, which were reconstructed by empirical correlations between the slope angle, total thickness, and stratigraphic settings of pyroclastic fall deposits mantling slopes. The results obtained were: (a) The understanding of a soil pressure head regime of the volcaniclastic soil mantle, always ranging in unsaturated conditions and characterized by a strong seasonal variability depending on precipitation patterns and the life cycle of deciduous chestnut forest; and (b) the reconstruction through a deterministic approach of seasonal intensity–duration rainfall thresholds related to different morphological conditions

Quantitative Assessment of Specific Vulnerability to Nitrate Pollution of Shallow Alluvial Aquifers by Process-Based and Empirical Approaches

Shallow aquifers of coastal and internal alluvial plains of developed countries are commonly characterized by the challenging management of groundwater resources due to the intense agricultural and industrial activities that determine a high risk of groundwater contamination. Amongthe principal origins of pollution in these areas are agricultural practices based on the amendment of soils by nitrate fertilizers, which have been recognized as one of the most severe environmental emergencies for which specific policies and regulations have been issued (e.g., EU Directive 2006/118/EC). In such a framework, the results of research aimed at assessing the specific vulnerability of shallow alluvial aquifers to nitrate fertilizer pollutants by coupled process-based and empirical approaches are here proposed. The research focused on assessing the specific vulnerability to nitrate pollution of a shallow alluvial aquifer of the Campania region (southern Italy), which was selected due to its representativeness to other recurrent hydrogeological settings occurring in alluvial plains of the region and worldwide. In this area, 1D hydro-stratigraphic models of the unsaturated zone were reconstructed and applied for simulating the transport of nitrate pollutants at the water table and estimating the associated travel times. Numerical modeling was carried out by the finite dierences VS2TDI code and considered a 10-year time series of rainfall and evapotranspiration as well as typical local farming practices of nitrate fertilizer input. Results of the travel time calculated for the 1D hydro-stratigraphic models considered and at dierent depths were recognized as a proxy to assess the specific vulnerability to nitrate fertilizer pollution. Among the principal outcomes is an empirical multiple correlation between the travel time of the nitrate fertilizer pollutant, water table depth, and equivalent saturated hydraulic conductivity of the unsaturated zone or hydraulic resistance, which was used to assess the travel time at the distributed scale over the whole area studied as well as the related specific vulnerability. Given such results, the coupled process-based and empirical approach is proposed as generally applicable for assessing and mapping groundwater vulnerability in shallow aquifers, for which detailed stratigraphic and piezometric data are available

Testing Evapotranspiration Estimates Based on MODIS Satellite Data in the Assessment of the Groundwater Recharge of Karst Aquifers in Southern Italy

In many Italian regions, and particularly in southern Italy, karst aquifers are the main sources of drinking water and play a crucial role in the socio-economic development of the territory. Hence, estimating the groundwater recharge of these aquifers is a fundamental task for the proper management of water resources, while also considering the impacts of climate changes. In the southern Apennines, the assessment of hydrological parameters that is needed for the estimation of groundwater recharge is a challenging issue, especially for the spatial and temporal inhomogeneity of networks of rain and air temperature stations, as well as the variable geomorphological features and land use across mountainous karst areas. In such a framework, the integration of terrestrial and remotely sensed data is a promising approach to limit these uncertainties. In this research, estimations of actual evapotranspiration and groundwater recharge using remotely sensed data gathered by the Moderate Resolution Imaging Spectrometer (MODIS) satellite in the period 2000–2014 are shown for karst aquifers of the southern Apennines. To assess the uncertainties affecting conventional methods based on empirical formulas, the values estimated by the MODIS dataset were compared with those calculated by Coutagne, Turc, and Thornthwaite classical empirical formulas, which were based on the recordings of meteorological stations. The annual rainfall time series of 266 rain gauges and 150 air temperature stations, recorded using meteorological networks managed by public agencies in the period 2000–2014, were considered for reconstructing the regional distributed models of actual evapotranspiration (AET) and groundwater recharge. Considering the MODIS AET, the mean annual groundwater recharge for karst aquifers was estimated to be about 448 mm·year−1. In contrast, using the Turc, Coutagne, and Thornthwaite methods, it was estimated as being 494, 533, and 437 mm·year−1, respectively. The obtained results open a new methodological perspective for the assessment of the groundwater recharge of karst aquifers at the regional and mean annual scales, allowing for limiting uncertainties and taking into account a spatial resolution greater than that of the existing meteorological networks. Among the most relevant results obtained via the comparison of classical approaches used for estimating evapotranspiration is the good matching of the actual evapotranspiration estimated using MODIS data with the potential evapotranspiration estimated using the Thornthwaite formula. This result was considered linked to the availability of soil moisture for the evapotranspiration demand due to the relevant precipitation in the area, the general occurrence of soils covering karst aquifers, and the dense vegetation

Hydrogeological conceptual model and groundwater recharge of Avella Mts. karst aquifer (southern Italy): A literature review and update

Study region: Avella Mts., southern Italy. Study focus: The paper is focused on groundwater of Avella Mts. This aquifer has been experiencing an increasing human pressure due to periods of drought and growth in groundwater extraction. A novel hydrogeological conceptual model was developed, and groundwater recharge was estimated by two approaches. The study was carried out by an in-depth literature review and a GIS-based analysis of geological and piezometric data, ground-based meteorological and remotely sensed data. New hydrological insights for the region: The new hydrogeological conceptual model allowed to reconstruct the aquifer lithology, its deep geometry, and, for the first time, groundwater flow scheme. Five groundwater basins were recognized with distinct outlets and subsurface outflows, suggesting a new aquifer compartmentalization in-series groundwater basins. Some basal springs are fed by autonomous basins with smaller extension, while other springs have dried up completely. The groundwater recharge varies from 7.30 to 6.90 m3/s as estimated by Turc formula and MODIS data, respectively; the values are comparable among them, confirming mutually the validity of approaches used. The comparison with previous studies highlights variations and changes for both the hydrogeological conceptual model and water balance, linked to natural and anthropogenic factors. The results obtained represent a way for supporting sustainable management of groundwater, waterwork systems security and groundwater-dependent ecosystems protection of a large sector of Campania region

A comparison of methods for assessing groundwater vulnerability in karst aquifers: the case study of Terminio Mt. aquifer (Southern Italy)

Abstract The assessment of groundwater vulnerability to pollution is becoming even more important all over the world due to the increase of impacts of human activities on groundwater resources and the related risks to the human health, economics, and the environment. Owing to the variability of methods known for estimating groundwater vulnerability, basically depending on hydrogeological parameters considered and the scale of analysis, the comparison of results of different methods appears straightforward for identifying the best approach in a given hydrogeological condition and reference scale. In such a view, this work attempts to assess the groundwater vulnerability of the Terminio Mt. karst aquifer, by applying four different groundwater vulnerability methods, index-based, and comparing results in order to identify the best performing one in karst environments. The study aquifer, located in the Picentini Mts Regional Park (Campania region, southern Italy) represents a strategic drinking water resource since Roman times and hosts massive groundwater resources which outflow mainly from tapped basal and subordinately perched springs. The peculiar characters of the study karst aquifer, which favour direct infiltration and groundwater recharge processes, as well as the occurrence of industrial, agricultural and grazing activities, make it very vulnerable to groundwater pollution, thus requiring a proper and careful territorial management. Beside the most frequently and generally used methods for assessing groundwater vulnerability, such as the DRASTIC and SINTACS, also DAC and COP methods specifically designed for karst aquifers were applied and mutually compared. Results of SINTACS, DRASTIC and DAC methods show groundwater vulnerability maps of the Terminio Mt. karst aquifer as chiefly characterized by two classes of intrinsic groundwater vulnerability, varying between the medium and high degrees. Furthermore, high and extremely high values of groundwater vulnerability were found in areas controlled by the shallow depth of the water-table. Instead, the COP method resulted as the most effective in identifying the endorheic areas and the related karst morphologies as very high groundwater vulnerability zones, therefore the most suitable in capturing specific hydrogeological features of karst areas that control groundwater pollution and vulnerability. Results obtained will support decision tools aimed at the land use planning and protection of karst aquifers from pollution in karst areas