Flowpath is the National Meeting on Hydrogeology promoted by the Italian Chapter of the International Association of Hydrogeologists. Since its first editions, the meeting has provided a place where young hydrogeologists, researchers, professionals, public administrations and water managers can meet, exchange experiences and discuss current challenges in groundwater science and practice. Its main objectives are to promote dialogue among the new generations of hydrogeologists, to explore the role of groundwater in a changing climate, to update the scientific and professional community on emerging hydrogeological issues, and to encourage the contribution of researchers, practitioners and institutions to the sustainable management of groundwater resources. [...]

In this paper, the assessment of the radon exhalation rate of the Modica stone building material, untreated and accelerated aged through salt crystallization test, is reported as a case study. Noteworthy, this construction material was largely employed for the construction of historical monuments of interest in the field of cultural heritage, especially in the historic city center of the Modica town, Sicily, Southern Italy, included in the UNESCO World Heritage list known as “Late Baroque Towns of the Val di Noto”. In detail, the Closed Chamber Method (CCM) with the Durridge Rad7 equipment for short-lived radon progeny alpha spectroscopy was employed to evaluate the radon exhalation rate of the investigated natural stone, and the Markkanen room model was used to calculate the potential indoor radon concentration based on the assessed rate value. Notably, the findings of this study can be employed to direct future research concerning the development of a systematic strategy for the radon content assessment in building materials, that turns out to be crucial for decision-makers, since it could be possible to identify vulnerable buildings requiring the use of well-defined protection measures.

The natural radioactivity content of the Ignimbrite campana stone, as well as its radon exhalation and mineralogical composition, were assessed and reported as a case study in the present paper. In particular, the High Purity Germanium (HPGe) gamma spectrometry and the Closed Chamber Method (CCM) with the Durridge Rad7 setup were employed to quantify the specific activities of 226Ra, 232Th and 40K, and the radon exhalation rate, respectively. In addition, several indexes were calculated to evaluate the radiological health risk related to radiation exposure from the analyzed natural stone, i.e. the absorbed gamma dose rate (D), the annual effective dose equivalent (AEDE), the activity concentration index (I), and the alpha index (I_alpha). Finally, X-Ray Diffraction (XRD) and Micro-Raman Scattering (MRS) investigations were performed to correlate the chemical composition and mineralogical characteristics of the investigated natural stone with its natural radioactivity content and radon exhalation rate.

Understanding fluid flow behaviour of faults is important for resource exploitation and management. Most studies analysing fluid flow behaviour in fault zones focus on either high-porosity or low-porosity sequences. In this study, we analyse various mechanical layers within alternating siliciclastic-carbonate sequences in fault zones in the Oligo-Miocene Logudoro basin, located in northern Sardinia (Italy). We combined a variety of methods, including field measurements of structures, in-situ permeability and Schmidt Hammer rebound measurements converted to uniaxial compressive strength. Furthermore, we performed thin section analysis, to characterize grain size, porosity, and mineral compositions. We used the gathered data to model the fluid flow conditions within deformation patterns present in one fault-zone. Deformation styles are related to mechanical properties of the rocks at the time of faulting, juxtaposition and differences in intergranular space and porosity in sandstones. The permeability is influenced by the presence of deformation structures such as fractures (high permeability), compactional shear bands (low permeability) and fault rocks within fault core (high and/or low permeability). The fluid flow model highlights the significant influence of deformation bands on the flow field and hydraulic gradient, demonstrating the importance of including these structures in the analysis.

[Article in Italian] Il Comitato Italiano dell’International Association of Hydrogeologists – IAH Italy ETS, in attuazione delle finalità previste dal proprio Statuto, che all’Art. 2 tra gli “scopi e compiti” prevede di “sostenere gli studi nel settore idrogeologico attraverso l’assegnazione di borse di studio, o altre tipologie di premi, a Laureati, Dottori di Ricerca e studiosi meritevoli, ed ogni altra iniziativa che il Consiglio Direttivo ritenesse necessaria e utile all’attuazione degli scopi dell’Associazione”, sta predisponendo i regolamenti ed i Bandi per l’assegnazione di Premi a giovani idrogeologi e idrogeologhe a partire dal 2026. [...]

[Article in Italian] L’organizzazione del Flowpath 2025 è partita da lontano, addirittura fuori dall’Italia! Era il 2023, a Malta, quando è stata proposta e selezionata Torino insieme alle sue due università per ospitare la 7° edizione del Convegno Nazionale di Idrogeologia. Le due università cittadine, l’Università degli Studi di Torino (Dipartimento di Scienze della Terra) e il Politecnico di Torino (Dipartimento di Ingegneria dell’Ambiente, del Territorio e delle Infrastrutture) hanno colto l’opportunità di unirsi in questo comune percorso. [...]

Monitoring and modelling of soil hydrological processes at large scales require measuring the spatial and temporal evolution of soil volumetric water contents, θv. Direct measurement of θv can be done by sampling and laboratory analyses. Although such methods are straightforward, they require a lot of time and effort for the collection of several samples to account for the spatial and temporal variability. Time-domain reflectometry, TDR, can be a good alternative as it is used to indirectly measure θv in the field by measuring the travel time of an electromagnetic pulse in a probe. However, it is an intrusive, point-scale method making it impractical at large scales and at subsurface measurements. Other geophysical methods, such as earth resistivity tomography, ERT, and electromagnetic induction, EMI, sensors represent a practical solution for their time efficiency and the ability to measure at large scales. In particular, compared to the ERT, which still requires the insertion of several electrodes at the soil surface and their connection with a cable network, the EMI has the further advantage (in terms of measurement rapidity) of not requiring insertion in soil to take measurements. Nevertheless, the toll to pay for this larger scale applicability, is that they do not directly measure θv and require complex electromagnetic inversion models to obtain either the electrical resistivity, ρb, or the bulk electrical conductivity, σb, spatial distributions over time respectively from the pseudo-sections coming from ERT and the series of apparent electrical conductivity, ECa, coming from EMI. In this sense, these methods require further efforts to correctly translate the ρb and the σb distributions in as many θv distributions. Accordingly, this study aims at comparing thermogravimetric, EMI and ERT systems to obtain the spatio-temporal evolution of θv at a transect scale. For this purpose, a series of measurement campaigns were carried out at a transect 24 m long and 1 m wide at a sprinkler-irrigated field in Arborea area in Sardinia, Italy. A large database of spatially, vertically and temporally distributed measurements was created from auger samples, undisturbed samples, Campbell TDR-200, ERT and CMD mini-explorer EMI sensor. TDR measurements were used to find a relationship between θv and σb. Inversion models were then used to obtain the σb distribution from ERT and EMI measurements, utilizing a previously determined characterization of the soil profile, e.g., layering, depth to groundwater table, texture, etc. The TDR-obtained θv - σb relationship was then utilized to estimate the θv distributions from EMI- and ERT-based σb distributions.

This review paper examines the hydrogeological characteristics and challenges of urban groundwater management in ten major Italian cities: Turin, Milano, Padova, Bologna, Roma, Pescara, Napoli, Bari, Catania, and Cagliari. Urbanization has placed significant pressure on groundwater systems, highlighting the need for sustainable management. The study categorizes the cities based on their hydrogeological settings and groundwater uses, identifying key issues such as salinization, industrial contamination, and land subsidence. The findings emphasize the importance of urban local aquifers (ULAs) for drinking water, industry, and ecological support, advocating for integrated urban water management and governance to enhance resilience against future water shortages and climate change impacts.

Linear transport infrastructures are essential for the socioeconomic development of industrialized countries. However, adverse meteorological and hydrogeological events can result in significant economic losses. Globally, floods have the most substantial socio-economic impact. Climate Change, due to the extent of transport infrastructures over flood -prone territories, is a very important factor in worsening flood risk. The main objective of this study is to identify the sections of the hydrographic network that are susceptible to flood and erosion hazards where road infrastructures are located. The Metropolitan City of Cagliari (Sardinia, Italy) is selected as test site, due to the presence of several coastal watersheds and of a high population density. A swift methodological approach, based on already available datasets from public repositories and GIS analyses, is presented. This approach includes: i) geomorphological characterization of the hydrographic network; ii) census of stream tracts where bridges were damaged in past flood events; iii) identification of potentially critical tracts (PCT), based on similar geomorphological conditions; iv) multi -temporal satellite imagery analysis of PCT for the identification of flood -prone areas and, therefore, vulnerable road crossings. The adopted methodology has proved to be effective for the identification of vulnerable road crossings over wide portion of territories, identifying critical sites that need further investigation.

Many countries are developing a radon action plan to provide decision-makers with a reliable tool for reducing the harmful effects of radon exposure in dwellings and among the general public and, accordingly, to implement land development strategies. Mapping the geogenic radon release in different geological environments could assist in delineating areas that require priority monitoring and regulation, as well as applying radon reduction techniques in newly constructed buildings. In this paper, the activity concentration of U-238, Ra-226, Th-232 and 40K and the exhalation rate of Rn-222 have been estimated for the Silurian black shales of Villasalto, a district in the south-eastern Sardinia (Italy). The radioactivity of Ra-226, 232Th and 40K radionuclides was found relatively high (256.32 +/- 87.00 Bq.kg(-1)), low (44.16 +/- 9.47 Bq.kg(-1)) and moderate to high (856.28 +/- 392.41 Bq.kg(-1)) respectively. The radon emanation coefficient (E) and the radon production rate (PRn) have been calculated based on the analysis of the radon growth model inside a sealed chamber. E was found to correlate well with the activity concentration of 226Ra, as well as with the grain size of the soil/rock samples under investigation. PRn was relatively high, ranging from 212.54 to 524.27 Bq.m(-3).h(-1). Furthermore, the mean value of the main radiation hazard indexes (i.e., the radium equivalent activity, the outdoor gamma-ray dose rate and the annual effective dose) were found to be 299.07 +/- 138.62 Bq.kg(-1), 169.97 +/- 75.58 nGy h(-1) and 0.21 +/- 0.09 mSv.y(-1) respectively.

This research aims at studying the intrinsic vulnerability of groundwater to diffuse environmental pollutants in the Muravera coastal agricultural area of Sardinia, Italy. The area faces contamination risks arising from agricultural practices, especially the use of fertilizers, pesticides, and various chemicals that can seep into the groundwater. The study examined the interplay among hydrological elements, including soil characteristics, groundwater depth, climate conditions, land use, and aquifer properties. To do that, the outcomes of FLOWS 1D physically-based agrohydrological model were analyzed in parallel with those of the overlay-and-index model SINTACS, in a sort of reciprocal benchmarking. By using FLOWS, water movement and solute transport in the unsaturated zone were simulated by, respectively, solving the Richard Equation (RE) and the Advection-Dispersion equation (ADE). As such, this model allowed to account for the role of soil hydraulic and hydro-dispersive properties variability in determining the travel times of a conservative solute through the soil profile to the groundwater. For FLOWS simulations, a complete dataset was used as input, including soil horizons, soil physical and hydraulic properties of 36 soil profiles, average annual depth to groundwater table at each soil profile (ranging from 1 to 50 meters), and climatic temporal series data on rainfall and evapotranspiration. Detailed analyses of travel times for the movement of 25, 50, 75, and 100% of the solute mass to reach groundwater were conducted, revealing that the depth to groundwater predominantly influences vulnerability. This result was coherent with SINTACS vulnerability map due to the large impact of the depth to groundwater on SINTACS analysis.

One of the crucial challenges of our time is climate change. The consequences of rising sea levels and drought greatly impact water resources, potentially worsening seawater intrusion. Characterizing coastal aquifers is an essential step in devising strategies to address these phenomena. Seawater intrusion poses a critical socio-economic and environmental issue in the coastal plain of Muravera, southeastern Sardinia (Italy). This coastal plain is an important agricultural area in Sardinia, and the health of the crops is compromised by the increasing salinization of shallow groundwater. To enhance our understanding of the hydrogeological conceptual model, which is essential for a sustainable resource management system, hydrogeological investigations were conducted and complemented by the chemical and multi-isotopic analyses of groundwater. The main objectives of this study were to identify groundwater recharge areas, understand salinization mechanisms and trace the evolution of water chemistry. Within this framework, a monthly survey monitoring piezometric level and electrical conductivity was carried out for one year. This survey was integrated with chemical and isotope analyses, including δ18OH2O and δ2HH2O, δ11B, δ18OSO4, δ34SSO4, and 87Sr/86Sr. Hydrochemistry analysis results revealed the occurrence of seawater–freshwater mixing, extending up to 4 km inland. H2O isotope analysis confirmed the mixing processes and indicated the meteoric origin of recharge waters for both shallow and semi-confined aquifers. The strontium isotopes ratio facilitated the identification of four main groundwater flow paths, confirmed by the SIAR model. The results of this combined hydrogeological–geochemical–isotopic survey provide essential elements for the future implementation of an integrated and sustainable management system. These findings enable interventions to slow the process of seawater intrusion and meet the economic needs for the development of local communities.

In recent years, with the development of intensive farming and livestock breeding activities, nitrate contamination of aquifers has occurred. The importance of the unsaturated zone in the study of nitrate percolation is well recognized. The vadose zone represents a fundamental part of the water cycle, capable of storing water, providing water for vegetation, transporting solutes and degrading contaminants before they reach the aquifer.This research involves two areas with different geological, hydrogeological and pedological properties located in Sardinia. The plain of Arborea has been designated as Nitrate Vulnerable Zone (NVZ) since 2005, but despite the reduction of nitrogen input no significant improvement in water quality has been achieved. In the Southern Campidano plain, an area with an agricultural tradition, significant nitrate concentrations were observed in groundwater.The main objective of this research is to estimate the groundwater recharge rate using vadose-zone water stable isotope profiles.Firstly, to understand the dynamics of water percolation through the vadose zone, soil samples were collected at different depths to analyzed for physical properties, including soil-water content, and grain size to estimate soil hydraulic properties. In addition, suction cups were installed at different depths at each site to extract pore water from the soil for chemical analysis.In hydrological systems, the use of stable isotopes (18O and 2H) of pore water as environmental tracers is considered the most useful tool for establishing water flow and contaminant transport. In this study stable pore water isotope profiles combined with water content profiles were used to obtain insight into the transit time of water percolating through the vadose zone. At each of the two study sites, vertical soil sampling was made along the vadose zone and the soil samples collected were analyzed for stable water isotope ratios (18O and 2H) and volumetric water content. Through the seasonal signatures of stable isotopes in leachate water it is possible to quantify possible groundwater recharge, this approach, called the peak-shift method assumes advection-dominated transport.Analysis of nitrate concentrations in soil water below the root zone using suction cups combined with groundwater recharge rates will allow an estimate of site-specific nitrate leaching. Through this approach, it is possible to evaluate potential and conservative propagation of nitrogen at specific depths to be compared with the concentrations measured to gain information on nitrate transformation processes in the soil.

<p>The Einstein Telescope (ET) is a proposed underground infrastructure to host a third-generation, gravitational-wave observatory. There are currently two candidate sites to host it: one of this is located in Sardinia region (Italy), in a favourable geological context, the other one in the Meuse-Rhine Euregion. Site-characterization studies are under way towards the site selection, which is expected for 2024. The scope work of this research is to evaluate the surface deformation of this site by integration of remote sensing techniques with geological and geophysical data. In this framework the PSI (Persistent Scattered Interferometry) technique with SAR data is the proposed approach for the analysis of a long time-series imagery. Although recent crustal movements in the study area are supposed to be very small (≃ - 0.5 mm/years from 2014 as measured by EUREF Permanent Network https://epnd.sgo-penc.hu), ESA Sentinel-1 data from Copernicus program, represents an effective tool to update this knowledge and monitor the phenomenon. A first analysis has been performed in the study area using the Snap2Stamps methodology. During the first assessment of this research, this methodology has been tested to a dataset of 94 images from Sentinel-1. The radar data (SLC, Single Looking complex) acquired from January 2021 to July 2022 for both descending and ascending orbits on an area of 250 sq km has been managed. The applied methodology requires a long-time for the processing in order to derive vertical velocities, and we considered the opportunity to use a cloud service. So, we exploited the possibility offered by SNAPPING service provided by Terradue (https://www.terradue.com/portal/), a cloud on-demand computing service for Sentinel-1 Multi-Temporal DInSAR processing, based on integrated SNAP and StaMPS chain. In this service, the dataset can be improved, considering a longer time of acquisition, exploiting the complete Sentinel revisiting time, starting from 2014.</p><p>The first results of this analysis have been calibrated with the existing GNSS measures provided by EUREF using the data of the Nuoro station. The ground vertical displacement calculations, composing data from both acquisition orbits, confirm the existing evaluations and extend the current information to the whole study area. Moreover, it will be possible to consider also future acquisition with a continuous monitoring process.</p><p>These results can be considered an important value for the proposed Italian site and the ET infrastructure realization.</p><p> </p>

In the European Union, nitrate vulnerable zone (NVZ) should be designed for the mitigation of nitrate (NO3-) contamination caused by agricultural practices. Before establishing new NVZ, the sources of NO3-; must be recognized. A geochemical and multiple stable isotopes approach (hydrogen, oxygen, nitrogen, sulfur and boron) and statistical tools were applied to define the geochemical characteristics of groundwater (60 samples), calculate the local NO3-; threshold and assess potential sources of NO3-; contamination in two study areas (hereafter Northern and Southern), located in a Mediterranean environment (Sardinia, Italy). Results of the integrated approach applied to two case study, permits to highlight the strengths of integrating geochemical and statistical methods to provide nitrate source identification as a reference by decision makers to remediate and mitigate nitrate contamination in groundwater.Hydrogeochemical features in the two study areas were similar: near neutral to slightly alkaline pH, electrical conductivity in the range of 0.3 to 3.9 mS/cm, and chemical composition ranging from Ca-HCO3-; at low salinity to Na-Cl-; at high salinity. Concentrations of NO3-; in groundwater were in the range of 1 to 165 mg/L, whereas the nitrogen reduced species were negligible, except few samples having NH4+ up to 2 mg/L. Threshold values in the studied groundwater samples were between 4.3 and 6.6 mg/L NO3-;, which was in agreement with previous estimates in Sardinian groundwater.Values of delta S-34 and delta O-18(SO4) of SO42-; in groundwater samples indicated different sources of SO42-; . Sulfur isotopic features attributed to marine SO42-; were consistent with groundwater circulation in marine-derived sediments. Other source of SO42-; were recognize due to the oxidation of sulfide minerals, to fertilizers, manure, sewage fields, and SO42-; derived from a mix of different sources.Values of delta N-15 and delta(ONO3)-O-18 of NO3-; in groundwater samples indicated different biogeochemical processes and NO3-; sources. Nitrification and volatilization processes might have occurred at very few sites, and denitrification was likely to occur at specific sites. Mixing among various NO3-; sources in different proportions might account for the observed NO3-; concentrations and the nitrogen isotopic compositions. The SIAR modeling results showed a prevalent NO3-; source from sewage/manure. The delta 11B signatures in groundwater indicated the manure to be the predominant NO3-; source, whereas NO3-; from sewage was recognized at few sites. Geographic areas showing either a predominant process or a defined NO3-; source where not recognize in the studied groundwater. Results indicate widespread contamination of NO3-; in the cultivated plain of both areas. Point sources of contamination, due to agricultural practices and/or inadequate management of livestock and urban wastes, were likely to occur at specific sites.

Come di consueto il mese di settembre è stato ricco di eventi organizzati o co-organizzati da IAH Italia. [Article in Italian]

<p>Many coastal areas around the world, especially low-lying delta areas, have a high density population and host important economic activities. In such context groundwater abstraction for public water, irrigation and private water supply can lead to over-exploitation and seawater intrusion phenomena. Saltwater intrusion is a critical socio-economic and environmental issue in the coastal plain of Muravera, south-eastern Sardinia (Italy). Since the early fifties the natural hydrodynamic equilibrium between groundwater, surface-water and seawater has been deeply modified by human interventions mainly related to the development of agriculture and tourism activities. The aim of this work is to deepen the knowledge about groundwater recharge areas, salinization mechanisms and water chemistry evolution through a combined hydrogeological and multi-isotopic approach. In this frame, a monthly piezometric and electrical conductivity monitoring survey was carried out for one year, integrated with chemical and isotope analyses of δ<sup>18</sup>O<sub>H2O</sub> e δ<sup>2</sup>H<sub>H2O</sub>, δ<sup>11</sup>B, δ<sup>18</sup>O<sub>SO4</sub>, δ<sup>34</sup>S<sub>SO4</sub>, <sup>87</sup>Sr/<sup>86</sup>Sr. Isotope analyses of δ<sup>18</sup>O<sub>H2O</sub> e δ<sup>2</sup>H<sub>H2O</sub> from two precipitation samples are also performed to provide a reference for local meteoric composition.</p> <p>Results from hydrochemistry analysis show the occurrence of seawater-freshwater mixing, extending up to 4 km inland. δ<sup>18</sup>O<sub>H2O</sub> & δ<sup>2</sup>H<sub>H2O</sub>, δ<sup>11</sup>B, δ<sup>18</sup>O<sub>SO4</sub> & δ<sup>34</sup>S<sub>SO4</sub> isotopes analysis confirms the mixing processes and indicates the meteoric origin of recharge waters for both shallow and semi-confined aquifers. Moreover, a clear correlation between precipitation and seawater H<sub>2</sub>O isotopic composition is observed. Strontium isotopes ratio has allowed the identification of four main groundwater flow paths, including lateral recharge from bedrock, surface water infiltration from the Flumendosa river and Rio Flumini Uri, and the occurrence of young mixing processes between fresh and sea waters. Outcomes from the combined investigation approach are crucial in the implementation of an integrated and sustainable management system which aims, on the one hand, at slowing the process of saltwater intrusion, and on the other hand to meet socio-economic needs for local communities’ development.</p>

<p>The alluvial aquifer of the Flumendosa delta plain, in south-eastern Sardinia (Italy), is overexploited for drinking and agriculture purposes and it is subjected to ongoing sea water intrusion phenomena. In a context of progressive quali-quantitative deterioration of groundwater resources, development of a sustainable management plan and, eventually, effective remediation actions require a deep understanding of the investigated system. A systematic review of dataset collected from literature, integrated with new field hydrogeological and geochemical data, is performed to improve the knowledge of the aquifer system. Despite the large amount of processed data, many aspects require further investigations. In this frame, a fast-running steady state groundwater flow numerical model is developed as a tool for testing the preliminary assumptions, to address the main uncertainties, and to optimize the acquisition of new field data. The adopted approach follows the methodology proposed by Lotti et al. (2021) for the development of a Numerically Enhanced Conceptual Model (NECoM).</p><p>Geometrical discretization of the numerical model is based on results of the 3D hydrogeological reconstruction of the plain area (Arras et al. 2019); simulation of main inflows and outflows, water exchange between surface water bodies and groundwater, irrigation and drinking water withdrawals is performed through the implementation of general head boundaries (GHB), river (RIV), and well (WEL) packages, respectively. Results from the application of the Soil Water Balance code (Porru et al. 2020) are used as input for simulating the average recharge from precipitation. Lateral recharge from the Paleozoic basement is also simulated. More than 4000 heads observations from about 350 wells and piezometers are used as targets in the calibration process; weights are assigned to deal with the high heterogeneity of the dataset quality. RIV and GHB conductance, irrigation well yields, direct and lateral recharge, and hydraulic conductivity are set as parameters in the calibration process. Due to the high sensitivity of some parameters, different calibration cycles are performed; hydraulic conductivities and lateral recharge are then calibrated in the last cycle.</p><p>Model results show that the hydrogeological conceptualization used for implementing the numerical model can reproduce the main general features of the piezometric head field. According to field observations, the Flumendosa river shows losing conditions in the western part of the plain and next to the river mouth, while gaining conditions occur in its central part; gaining conditions are also observed along the abandoned branches of the Flumendosa river, also known as <em>foxi</em>. Moreover, mass balance analysis show that the Flumendosa river represents the main recharge input of the whole groundwater system, providing an average inflow of about 4.3 Mm<sup>3</sup>/year. Nevertheless, several local incongruencies with the observed data were precious to highlight the effects of unknown variables such as agricultural extraction wells, the hydrogeological role of the bedrock or the water exchange between surface and groundwater bodies. The discrepancies, rather than the agreements, provided useful direction for the detection of new data to be collected to capture the salient information needed for a proper water resource management.</p>