CNR-IRPI, Italy

This paper deals with a Southern Italy area, 40 km by 10 km wide, located where four river valleys anastomose themselves in the coastal plain. The geological and hydrogeological features of the study area and the chemical-physical groundwater characterisation have been inferred from the data analysis of 1130 boreholes. Some aquifers, connected among them, constituted by soils of different geological origin -marine terraces deposits, river valley alluvial deposits and alluvial and coastal deposits - have been considered. The coastal plain aquifer is the most interesting for practical utilisation. Groundwater flow is mainly unconfined in the marine terraces and in the river valleys while it becomes mostly confined in the coastal plain aquifer. An upper clayey layer overlies the sandy coastal aquifer characterised by a mean hydraulic conductivity value equal to 2.3 10-4 m/s. The bottom is a silty-clayey bed which lies under the sea level. Being the direct natural recharge extremely low, the recharge of this coastal aquifer is mainly guaranteed by the discharge from upward aquifers and from the river leakage. The new acquired knowledge permits to delineate scenarios useful for an optimization of the groundwater resources tapping and for pursuing the safeguard of them.

Seawater intrusion is a pervasive problem affecting coastal aquifer, where the concentration of population and the increasing water demand creates risks of overexploitation, especially in those areas where is the only resource of drinking and irrigation water. This phenomenon is more considerable for the coastal karst aquifers, as observed in many Mediterranean countries and in some Italian regions as Friuli, Sardegna, Sicilia, Lazio, Campania and Puglia. This note aims to describe a research activity finalised to define a numerical model as management tools for groundwater resource of Salento (South Italy) to reduce the quantitative and qualitative degradation risks. The numerical codes used was MODFLOW (McDonald and Harbaught, 1988) and SEAWAT (Guo and Langevin, 2002). The active domain of the study area (active cells) covered approximately 2,300 km2 with 45,925 cells. Vertically, to allow a good lithological and hydrogeological discretization, the area was divided into 12 layers, from 214 to -350 m asl. Thickness and geometry of layers was defined on the basis of the aquifer conceptualisation based on the 3D knowledge of hydrogeological complexes. On the basis of detailed geological and hydrogeological conceptualisation, the climate change effects were considered in terms of natural recharge variations from 1930 to 1999 (Cotecchia et al., 2005; Polemio and Casarano, 2008). To take account of anthropogenic activity, mainly due to tourism and agriculture, the discharging trend was assessed, focusing on late decenniums (eighties and nineties), in which the discharge increase was mainly observed. Models representing the natural steady-state condition (using data of thirties) and transient scenarios of late decenniums were realised. The purpose of this first model implementation was, besides validated model, to assess the groundwater availability and quality in a recent period of seventy years (Polemio and Romanazzi, 2012; Romanazzi and Polemio, 2013). Results emphasize an essential decrease of piezometric levels and a worsening of seawater intrusion. On these bases, six forecasting transient scenarios were implemented, referred to future periods of about twenty years (2000-2020, 2021-2040 and 2041-2060) with the aim to predicting the evolution of piezometric level and seawater intrusion. For forecast data about precipitation and temperature, among the many models in the literature, we referred to the model developed by Giorgi and Lionello (2008), in relation to the defined scenario A1B. The model predicts temperature variations (°C) and precipitation percentage variation for the period 2001-2100. It was considered an average temperature variation form 0.9 °C (2001-2020) to 2.4 °C (2040-2060). Precipitation shows a negative percentage change (referred to 1960-80) equal to -3.9, -5.9 and -9,0% respectively for 2000-2020, 2021-2040 and 2041-2060. These climatic data are in agreement with other climate change models (Garcia- Ruiz et al., 2011). For the three future scenarios new recharge and discharge were assessed. In terms of discharge, they are mainly due to irrigation. For this kind of future utilisation two hypotheses were considered. The first assumes that type and extension of cultivations will be steady and, as an effect of climate change, the pressure on groundwater resource will further rise as necessary to satisfy irrigation demand (Dragoni and Sukhjia, 2008; Goderniaux et al., 2008). In the second hypothesis the irrigation discharge will be steady and equal to those of the 1999 due the adaption of cultivation types and irrigation practices. In both cases the scenario results show a general decrease of the piezometric head and a deterioration of water quality caused by seawater intrusion (Romanazzi et al., 2013). The results call for new land and groundwater resources management criteria. Considering the Water Framework Directive (EC, 2000) and international and regional experiences (LaMoreaux, 2010; Jiménez-Madrid, 2010; Polemio et al., 2009, Polemio et al., 2010), the study area was subdivided in three zones. To define the zone boundary, the threshold criterion was used (Polemio and Limoni, 2001; Polemio et al., 2009). The threshold between pure fresh groundwater and any type of mixing between fresh and saline groundwater was defined equal to of 0.5 g/l. In the first zone, the coastal zone, salinity was always (in the past) above the threshold, a transition zone, where salinity was variable respect to the threshold, and a third zone or inland zone where salinity value was permanently below the threshold. These three zones were implemented in the model. Different combinations of discharge criterions applied to these zones suggest the best choices to be applied for management criteria able to safely considered the future effects of climate changes.

The increasing overexploitation of water resources is observed on a global scale in the previous decades; this trend involves the coastal regions of Mediterranean Basin (Van Beynen et alii, 2012). As an effect of increasing groundwater discharge from coastal aquifers, the phenomenon of seawater intrusion is becoming a serious problem for most of the coastal aquifers, especially in the Mediterranean area (COST, 2003; COST, 2005). The aim of this paper is to present the modeling of a coastal porous aquifer located in the complex plain of Sibari (Southern Italy), a plain deeply modified as an effect of reclamation works realized after thirties. The model was implemented using piezometric historical data (from thirties) to establish the effect of seawater intrusion when the well discharge was negligible (natural conditions), the modification in subsequent decades, to be used for forecasting purpose and for evaluate the evolution of groundwater resource. The area actually represents a landscape with anthropic equilibrium based on the works of a land reclamation project (1960s-1990s). Study area is about 365 km2 for a coastline of about 35 km, about which an hydrogeological conceptual model was defined. The area can be conceptualized into three hydrogeological complexes (from the top): sand complex, a clay complex and a sand and conglomerate complex, constituting the deep aquifer, the bottom of which is not well-defined. Shallow aquifer is predominantly fed by direct rainwater infiltration. Deep aquifer is fed by outflows of the mountainous aquifers as the case of limestone aquifer of Pollino Mount,and of shallow granitic aquifer of the Sila massif (Guerricchio and Melidoro, 1975). The maximum piezometric levels of the deep aquifer are equivalent to approximately 40 m asl, so in some areas it presents artesian feature. The computer codes selected for numerical groundwater modelling were MODFLOW (McDonald and Harbaugh, 1998) and SEAWAT (Guo and Langevin, 2002). This groundwater flow modelling is based on the concept of a equivalent homogeneous porous medium by which it is assumed that the real heterogeneous aquifer can be simulated as homogeneous porous media within cells or elements (Anderson, 2002). The modeled aquifer area was uniformly discretized, using Peclet number, into a finite difference grid of 97,735 cells of 240 m x 350 m. For the vertical discretization, model was divided into five layers of variable thicknesses, defined on the basis of a multi-methodological geological survey. Climatic, hydrological and agricultural data were processed to defines inputs for the numerical model based on the variable-density flow. An hydrological balance using monthly and annual of 13 thermo-pluviometric stations falling in the study area, in the time period 1930-1975, was done (Polemio and Casarano, 2008, Polemio et alii, 2013). The numerical model was calibrated with PEST code with a correlation coefficient equal to 0,90. Preliminary results of steady flow and of groundwater salinity spatial are now available and shows it is not sustainable in the case of shallow aquifer and it can be improved in the case of deep aquifer.

The coastal karst aquifers are known to be highly vulnerable to anthropogenic and natural changes, and in particular to the overexploitation of groundwater resources. The high degree of vulnerability is due to their intrinsic characteristics, anthropogenic pollution, and the effects seawater intrusion. The progressive population concentration in coastal areas and the increasing discharge overlapped to peculiarities of karstic coastal aquifers constitute a huge worldwide problem, particularly relevant for coastal aquifers of the Mediterranean basin. In Italy, Apulia, with its coastline extending over 800 km, is the region with the largest coastal karst aquifers. The predominant karstic Apulian features make the region extremely poor of surface water resources and rich of high quality groundwater resources. These resources still allow the social and economic development of population, improving agricultural and tourist opportunities. The continuous increasing well discharge causes or contributes to the groundwater quality degradation, often making the groundwater unusable for irrigation and drinking (Polemio et al. 2009). The strategic importance of groundwater resources and its wise management for Apulian population is due to these risks (Cotecchia and Polemio 1998, Margiotta and Negri 2005). The aim of this study is to define the efficacy of existing management tools and to develop predictive scenarios to identify the best way to reconcile irrigation and drinking water demands with enduring availability of high quality groundwater. The Salento (Salentine Peninsula), was selected being the Apulian aquifer portion exposed to the highest risk of quality degradation due to seawater intrusion.

The considered study area is, subjected to a semiarid climate, lying in Southern Italy. Data coming from 1130 boreholes have been considered to define the geological and hydrogeological set-up of the study area and for estimating the groundwater use and the salt-related groundwater quality degradation. The aquifers are constituted by marine terraces deposits, river valley alluvial deposits and alluvial and coastal deposits. Groundwater flow is mainly unconfined in the marine terraces and in the river valleys while it becomes mostly confined in the coastal plain aquifer. Being the direct natural recharge extremely low, the recharge of this coastal aquifer is mainly guaranteed by the discharge from upward aquifers and from the river leakage. Two dominant types of groundwater have been distinguished: the HCO3-Ca (in the marine terraces and in the alluvial deposits) and SO4-Cl-Na (in the coastal plain deposits). The variability of major ions contents is related to many factors such as the different lithologies of the aquifers, the seawater intrusion, the mixing with river water and the impact of intensive farming. As regards the presence of the seawater intrusion in the study area, the analysis of the concentration maps of TDS, groundwater electrical conductivity and of the ions present in seawater, generally indicate that seawater contamination is relevant along a strip of land stretching for 2.5-3 km from the coastline inwards. The new acquired knowledge permits to delineate scenarios useful for an optimization of the groundwater resources tapping and for pursuing the safeguard of them.

The Vadoncello landslide was mobilized in December 1993 and is still active. It involves highly tectonized soils and is the reactivation of a landslide dragged by a larger landslide at the toe of the slope soon after the 1980 Irpinia (Southern Italy) earthquake. Investigations and monitoring of the Vadoncello landslide were carried out, between 1994 and 1996, within an EC funded research project. The slope has been found to be formed of chaotic successions of soil and rock strata which have been grouped into soil complexes. The soil mechanical properties are shown to be very poor, the deep soils being prone to large plastic straining even due to relatively small loading changes. The soil displacements show that a shallow fast rotational sliding has occurred at the top of the slope and a shallow earthflow has developed downslope, both lying above deeper soils involved in a mechanism of slow and long-lasting irrecoverable movements. These slow deep movements are considered to be consequent to the plastic flow of the clayey soils. They can be activated by the effects of seasonal rainfall, of low-medium intensity seismic events and by the effects of the morphological changes resulting from the slow movements themselves. The landslide reactivation in 1993 is seen to have been the combination effect of a low return-period rainfall event and the slow movements active at depth in the slope.

The Mar Piccolo (literally “narrow sea”), a sea internal basin which is part of the Taranto Gulf, located along the Ionian coast in southern Italy (Apulia region), represents both a peculiar and sensitive environmental area and a national environmental and social emergency due to the level of sea water pollution due to the pollutants coming from the close industrial area of Taranto. The area, located between the southern part of the Murgia plateau and the Ionian sea, is geologically characterized by a sequence of Mesozoic limestone (the Apulian carbonate platform) constituting the foreland of the southern Apennines chain. The Mesozoic sequence is intensely fissured and karstified, and forms an important groundwater reservoir. The aquifer occurring in the carbonate sequence of the Murgia plateau feeds numerous coastal springs and constitute the main local source of pure fresh groundwater. Galeso, Battentieri and Riso are the main subaerial springs located along the coast of Mar Piccolo, not far from the town of Taranto. This area is also characterized by several submarine springs, locally called “Citri”. Submarine freshwater discharge plays an important, though not well quantified, role in the hydrogeological equilibrium of the system, but also the source of the spreading of many pollutants in the Mar Piccolo area due to the close presence of one of the largest European steel mill together a number of hazardous industrial activities of other types. The paper describes the efforts and the preliminary results to define a detailed conceptualisation of the aquifer as main support to characterise the hydrological balance of the internal sea and the quality of sea water and the effect on of the ecological equilibrium of the coastal environment.

The Mar Piccolo basin is an internal sea basin located along the Ionian coast (Southern Italy), and it is surrounded primarily by fractured carbonate karstic environment. Because of the karstic features, the main continental water inflow is from groundwater discharge. The Mar Piccolo basin represents a peculiar and sensitive environment and a social emergency because of sea water and sediments pollution. This pollution appears to be caused by the overlapping effects of dangerous anthropogenic activities, including heavy industries and commercial and navy dockyards. The paper aims to define the contribution of subaerial and submarine coastal springs to the hydrological dynamic equilibrium of this internal sea basin. A general approach was defined, including a hydrogeological basin border assessment to detect inflowing springs, detailed geological and hydrogeological conceptualisation, in situ submarine and subaerial spring measurements, and flow numerical modelling. Multiple sources of data were obtained to define a relevant geodatabase, and it contained information on approximately 2,000 wells, located in the study area (1,600 km2). The conceptualisation of the hydrogeological basin, which is 978 km2 wide, was supported by a 3D geological model that interpolated 716 stratigraphic logs. The variability in hydraulic conductivity was determined using hundreds of pumping tests. Five surveys were performed to acquire hydro-geochemical data and spring flow-yield measurements; the isotope groundwater age was assessed and used for model validation. The mean annual volume exchanged by the hydrogeological basin was assessed equal to 106.93 106 m3. The numerical modelling permitted an assessment of the mean monthly yield of each spring outflow (surveyed or not), travel time, and main path flow.

e paper deals with the seawater intrusion hazard along the Ionian coastal plain (Southern Italy), between the mouths of Sinni and Bradano Rivers. Subjected to intense agricultural activities, the good-quality of the tapped groundwater is seriously important for the economic growth of this coastal area. The stratigraphical and hydrogeological set-up of the area as the geochemical features of the groundwater arise from the data analysis of 1130 boreholes, widespread over the whole area and from 1.3 up to 423 meters deep. The contribution of seawater intrusion to salinization processes of the studied groundwater system is characterised. As pointed out by chemical-physical data, this phenomenon involves the studied coastal plain for a width of 1-1.5 km on average and it is less evident moving inwards where the altitude of the clayey bottom of the aquifer becomes progressively higher than the sea level. A preliminary seawater hazard map has been carried out through piezometric and aquifer geometrical data.

The coastal carbonate Apulian aquifers, located in southern Italy, feed numerous coastal cold springs and constitute the main local source of high quality water. The group of Santa Cesarea springs constitutes the unique occurrence of thermal groundwater outflow, observed in partially submerged coastal caves. The spring water is rich of hydrogen sulfide; temperature ranges from 25 to 33 C°. For their properties, spring waters are used for spa activities from several decades. Hydrogeological spring conceptualisations proposed up now were not able to justify water geochemical peculiarities or were not completely confirmed up now. To reduce these uncertainties, a complex hydrogeological survey has been defined. Geological and structural surveys, chemical and isotopic groundwater analyses, spring and well discharge measurements, well loggings, multi-parameters spring automatized measurements, and cave explorations are ongoing. All available data have been used to improve the knowledge of groundwater flow system, including the valuable deep aquifer, the origin of the thermal waters, and to investigate the possibility of using low-enthalpy geothermal fluids to fulfil the thermal needs of the town of Santa Cesarea Terme.