Coupled decadal variability of the North Atlantic Oscillation, regional rainfall and karst spring discharges in the Campania region (southern Italy)

Abstract. Thus far, studies on climate change have focused mainly on the variability of the atmospheric and surface components of the hydrologic cycle, investigating the impact of this variability on the environment, especially with respect to the risks of desertification, droughts and floods. Conversely, the impacts of climate change on the recharge of aquifers and on the variability of groundwater flow have been less investigated, especially in Mediterranean karst areas whose water supply systems depend heavily upon groundwater exploitation. In this paper, long-term climatic variability and its influence on groundwater recharge were analysed by examining decadal patterns of precipitation, air temperature and spring discharges in the Campania region (southern Italy), coupled with the North Atlantic Oscillation (NAO). The time series of precipitation and air temperature were gathered over 90 yr, from 1921 to 2010, using 18 rain gauges and 9 air temperature stations with the most continuous functioning. The time series of the winter NAO index and of the discharges of 3 karst springs, selected from those feeding the major aqueducts systems, were collected for the same period. Regional normalised indexes of the precipitation, air temperature and karst spring discharges were calculated, and different methods were applied to analyse the related time series, including long-term trend analysis using smoothing numerical techniques, cross-correlation and Fourier analysis. The investigation of the normalised indexes highlighted the existence of long-term complex periodicities, from 2 to more than 30 yr, with differences in average values of up to approximately ±30% for precipitation and karst spring discharges, which were both strongly correlated with the winter NAO index. Although the effects of the North Atlantic Oscillation (NAO) had already been demonstrated in the long-term precipitation and streamflow patterns of different European countries and Mediterranean areas, the results of this study allow for the establishment of a link between a large-scale atmospheric cycle and the groundwater recharge of carbonate karst aquifers. Consequently, the winter NAO index could also be considered as a proxy to forecast the decadal variability of groundwater flow in Mediterranean karst areas

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

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

Groundwater flow characterization and reconstruction of the hydrothermal system of Ischia as a tool for volcanic risk mitigation

The volcanic system of Ischia is characterized by an intense hydrothermal activity, documented since the early 16th century by the study of Iasolino [1588], which represents the first systematic analysis of the thermal springs of the island for therapeutic purposes. Later studies partially contributed to the enhancement of knowledge on the volcanic, hydrogeological and hydrothermal features of the island, highlighting the strong interaction between hydrothermal flowpaths and volcanotectonic processes. The reconstruction of the hydrothermal system becomes, therefore, a fundamental element for territorial planning, not only in terms of management of the huge water and geothermal resource, but also and above all in a perspective of prevention and mitigation of volcanic risk. Thermal springs, fumaroles and clay deposits due to the hydrothermal alteration of volcanic products testifies for the existence of an active deep hydrothermal system. However at Ischia the geochemical characterization of fluids and groundwater, performed through sampling and analysis of a discrete number of scattered springs, wells and fumaroles, has been used for the definition of the origin and structure of hydrothermal systems as a whole, as the hydrogeological information is incomplete. Moreover, volcanic hydrothermal systems, such as that characterizes the island of Ischia, are particularly difficult to analyze and outline, as the groundwater resources are the result of an articulated and dynamic interaction among meteoric water, sea water and fluids of deep origin. In such cases, the need for an interdisciplinary approach is evident, involving knowledge and research methods ranging from geology to volcanology, geophysics, geochemistry, mineralogy and hydrogeology. With particular reference to the functional and structural representation of the geothermal system of the island of Ischia and the resulting correlations with the volcanotectonic processes, the examination of previous information highlights the need to update and improve the knowledge on groundwater hydrodynamics and mineralization processes. Therefore, the present work represents a strong interdisciplinary action that, starting from the design and implementation of a database on the existing geological/volcanological and hydrogeological information, contributes to highlight the critical issues, define an operating scheme of the hydrogeothermal system of the island of Ischia, and upgrade its hydrogeological, geochemical and volcanic monitoring system, in order to contribute to the mitigation of volcanic and related risks. The knowledge of groundwater dynamics and pathways, in fact, is of fundamental importance for understanding the water/magma interaction processes in case of realimentation of the shallow magmatic system, and the assessment of the possibility of phreatic explosions occurrence. Moreover, the knowledge of the thermal fluids’ circulation and the related rock alteration processes is of paramount importance in the definition of the mechanic characteristics of rock masses and their proneness to failure

Groundwater flow process in the active volcanic system of Ischia Island (Italy)

The volcanic system of Ischia is characterized by an intense hydrothermal activity, documented since the early 16th century by the study of Iasolino (1588), which represents the first systematic analysis of the thermal springs of the island for therapeutic purposes. Later studies partially contributed to the enhancement of knowledge on the volcanic, hydrogeological and hydrothermal features of the island, highlighting the strong interaction between hydrothermal flowpaths and volcano- tectonic processes. The reconstruction of the interplay between hydrothermal and magmatic system becomes, therefore, a fundamental element for territorial planning, not only in terms of management of the huge water and geothermal resource, but also in a perspective of prevention and mitigation of volcanic risk. Thermal springs, fumaroles and mud deposits give beginning clues about deep hydrothermal conditions. Till now at Ischia, the local geochemical characterization of fluids and groundwater has been used for the definition of the origin and structure of the hydrothermal system as a whole, as the hydrogeological information is incomplete. However, volcanic hydrothermal systems, such as that characterizes the island of Ischia, are particularly difficult to analyze and outline, as the groundwater resources are the result of a complex and dynamic mixing among meteoric water, sea water and deep fluids. In such cases, the need for an interdisciplinary approach is evident, involving knowledge and research methods ranging from geology to volcanology, geophysics, geochemistry and hydrogeology. With particular reference to the functional and structural representation of the geothermal system of the Ischia island and the resulting correlations with the volcano-tectonic processes, the examination of previous information highlights the need to update and improve the knowledge on groundwater hydrodynamics and mineralization processes. Therefore, the present study aims at a strongly interdisciplinary action that, starting from the design and implementation of a database on the existing geological/volcanological and hydrogeological information, will contribute to highlight the critical issues, define an operating scheme of the hydro-geo-thermal system of the island of Ischia, and upgrade its hydrogeological, geochemical and volcanic monitoring system. The preliminary results improved the definition of the hydrogeological complexes and advanced knowledge of the groundwater flow conditions

The quantification of low-probability–high-consequences events: part I. A generic multi-risk approach

ISSN:0921-030XISSN:1573-084

Environmental status of groundwater resources in the Solofrana River Valley

Heterogeneity of natural systems governs the pathway of pollutant in the environment, mostly in groundwater resources. A large number of hydrogeological research aims to parametrize and model these processes. The spatial variability of the hydrogeological properties of the rock can be define from geologic observation and local measurements. The Solofrana River Valley is a real natural laboratory to improve understanding of the behaviour and transfer of pollutants on larges scale, because of its geological and structural complexity combined with a strong industrial and agricultural activities. A multidisciplinary approach has been employed to delineate aquifer/aquitard unit and characterize scale-dependent heterogeneity using geological, hydrogeological and geochemical tecniques. The paper describes firstly the experience carried out in an area characterized by a high antropic impact. Besides, it reports about relevant geological and hydrogeological aspects of the Solofrana River Valley and presents some interesting aspects related to field operations and quantitative evaluation of pollution flow and transport

Environmental indexes as a tool to identify contamination sources in alluvial aquifer systems

The increased use of chemicals in many anthropogenic activities and their dispersion into the environment can damage irreversibly the natural resources essential for human life. Among these, groundwater resources are, undoubtedly, strategic for the existence of human communities, primarily in those areas where population density is high and the land human use is intensive, so that a relevant groundwater resource vulnerability exists. The identification and characterization of contamination sources for groundwater can be more difficult than for other environmental pathways; in fact the relationship between environmental pressures and the complex structure of groundwater flow systems involves many processes, which affect the behaviour and transport of pollutants. With regard to the wide variety of structural, volcanic and depositional processes which characterize the alluvial aquifer systems in the Campania Region (South Italy), this paper describes a multidisciplinary approach to delineate aquifer/aquitard unit and recognizes scale-dependent heterogeneity by means of geological, hydrogeological, geochemical and geostatistical techniques. In such complex hydrogeological structures special attention has to be paid to recharge mechanism of confined or semiconfined aquifers, as well as of bedrock karst aquifers underlying heterogeneous deposits such as pyroclastic-alluvial successions. Moreover, heterogeneity affects leakage in complex aquifer systems and increases hydrodispersion parameter uncertainty. Decisions on groundwater protection policy, according to European directives, may be based on the improvement of the concept of “aquifer analogue” to basin fills. It is useful to identify heterogeneity properties, which control the permeability distribution. So hydro-stratigraphic architecture derives from equivalent parameters variability, which describes homogeneous media or hydrogeological units. In this line, the aquifer analogy can be associated to a set of indicators representative of the groundwater composition. Each indicator describes a specific aspect of groundwater quality and leads in combination with others to the definition of groundwater environmental index, due to natural and anthropogenic phenomena. The results of multivariate statistical analyses provide the identification of a number of homogeneous zones even in complex alluvial aquifer systems. At the same time, in wide regions this approach is able to point out the more hazardous sites where contamination sources are likely to be localized, and provides the working scale for planning technical and procedural solutions. The experience carried out in the Solofrana River Valley (South Italy) characterized by a high human impact and by geological and structural complexity of the territory is discussed in detail. Relevant geological and hydrogeological features and some interesting aspects related to pollutant flow and transport are presented