The small islands in the Mediterranean Sea suffer water shortages, aggravated by pressure from tourism during the dry season. Many are affected by the intense and increasing human water demand and the harsh climatic and geographic nature of the island terrain. The present study, carried out on the island of Favignana, Egadi Archipelago (southern Italy), evaluates the regime of recharge to the subsurface, and hypothesizes a solution for identifying the areas where groundwater is most abundant, as well as the best management options for human use. By means of hydrological measurements and chemical analyses, a specific location has been identified in the eastern sector of the island where groundwater has optimal quality and the water table is at a depth of only a few metres. In other areas of the island the groundwater is more saline, due to seawater intrusion, and it is present only at greater depths. The residents of the island have in the past lived harmoniously with the climatic and hydrological regime of the island, and have shown good ability to manage the groundwater resources, fed by the limited precipitation that comes in winter, using it as a supplement to the drinking water supply that comes from Trapani (mainland Sicily) by a submarine pipeline and by tanker. Optimized management of the groundwater resources could reduce the volume of freshwater transferred from the mainland.

Modelling tools are necessary for quantitative assessment of groundwater-dependent systems such as interacting groundwater aquifers and lakes. Numerical groundwater models supplemented by stream and lake submodels are the best available tools for testing the conceptual relation of surface water to groundwater, for identifying gaps in the amount and quality of data, and for better understanding the sustainability of a groundwater-lake system in the presence of stresses. Models are of particular interest when applied to an infrequently studied geological context that is subject to specific vulnerabilities and patterns of interaction. Volcanic lakes are one setting where flow models serve to extend current conceptual and practical understanding. In this study, a groundwater/surface-water flow model is presented for the flow-through Bracciano deep caldera lake located near Rome, Italy. The steady-state model quantifies and tests the existing conceptual understanding of the system by taking account of all sources and sinks, and by calibration of key parameters to head and flow data. A transient version of the model demonstrates the response of the system to dry and wet years and to anthropogenic stresses. Although precipitation is the dominant source of water overall for the lake, a major finding of this study is that the groundwater inflow to the lake can buffer fluctuations in lake-water level and reduce lake-level declines, especially during shorter periods of dry conditions.

In the Gran Sasso fissured carbonate aquifer (central Italy), a long-term (2001–2007) spatio-temporal hydrochemical and²²²Rn tracing survey was performed with the goal to investigate groundwater flow and water–rock interaction. Analyses of the physico-chemical parameters, and comparisons of multichemical and characteristic ratios in space and time, and subsequent statistical analyses, permitted a characterisation of the hydrogeology. At the regional scale, groundwater flows from recharge areas to the springs located at the aquifer boundaries, with a gradual increase of mineralisation and temperature along its flowpaths. However, the parameters of each group of springs may significantly deviate from the regional trend owing to fast flows and to the geological setting of the discharge spring areas, as corroborated by statistical data. Along regional flowpaths, the effects of seasonal recharge and lowering of the water table clearly cause changes in ion concentrations over time. This conceptual model was validated by an analysis of the²²²Rn content in groundwater.²²²Rn content, for which temporal variability depends on seasonal fluctuations of the water table, local lithology and the fracture network at the spring discharge areas, was considered as a tracer of the final stages of groundwater flowpaths.

A groundwater flow model of the Alpine valley aquifer in the Aosta Plain (NW Italy) showed that well pumping can induce river streamflow depletions as a function of well location. Analysis of the water budget showed that ∼80% of the water pumped during 2 years by a selected well in the downstream area comes from the baseflow of the main river discharge. Alluvial aquifers hosted in Alpine valleys fall within a particular hydrogeological context where groundwater/surface-water relationships change from upstream to downstream as well as seasonally. A transient groundwater model using MODFLOW2005 and the Streamflow-Routing (SFR2) Package is here presented, aimed at investigating water exchanges between the main regional river (Dora Baltea River, a left-hand tributary of the Po River), its tributaries and the underlying shallow aquifer, which is affected by seasonal oscillations. The three-dimensional distribution of the hydraulic conductivity of the aquifer was obtained by means of a specific coding system within the database TANGRAM. Both head and flux targets were used to perform the model calibration using PEST. Results showed that the fluctuations of the water table play an important role in groundwater/surface-water interconnections. In upstream areas, groundwater is recharged by water leaking through the riverbed and the well abstraction component of the water budget changes as a function of the hydraulic conditions of the aquifer. In downstream areas, groundwater is drained by the river and most of the water pumped by wells comes from the base flow component of the river discharge.

The application of statistical classification methods is investigated—in comparison also to spatial interpolation methods—for predicting the acceptability of well-water quality in a situation where an effective quantitative model of the hydrogeological system under consideration cannot be developed. In the example area in northern Italy, in particular, the aquifer is locally affected by saline water and the concentration of chloride is the main indicator of both saltwater occurrence and groundwater quality. The goal is to predict if the chloride concentration in a water well will exceed the allowable concentration so that the water is unfit for the intended use. A statistical classification algorithm achieved the best predictive performances and the results of the study show that statistical classification methods provide further tools for dealing with groundwater quality problems concerning hydrogeological systems that are too difficult to describe analytically or to simulate effectively.

Complex hydrogeological systems require detailed knowledge of aquifer dynamics to ensure appropriate and sustainable management of the groundwater resource. The Riardo Plain aquifer, southern Italy, is a strategic resource for conjunctive uses; nevertheless, the conceptual model still suffers some uncertainties due to the presence of a deep lateral inflow through the carbonate basement. Therefore, the realisation of a 3D numerical model at catchment scale needs preliminary tests to constrain the possible additional inflow rate, which is at the moment only estimated through the results of the groundwater budget calculation. A 2D section of the mixing area was modelled using FEFLOW in order to test the hypothesis of a combined recharge. Seven versions of the same model were calibrated over an increasing number of adjustable parameters according to their sensitivity. The most efficient model version was identified according to the calculated information criteria and the sum of squared-weighted residuals. In the second phase of the work, nine model scenarios characterised by different deep inflow rates were calibrated and validated according to the same procedure of the first model, in order to identify the range of possible acceptable solutions. The most likely deep inflow rate is 34 ± 4% of the total recharge, corresponding to an estimated deep inflow of 415 ± 50 L/s in the Riardo Plain aquifer through the carbonate basement. This methodological approach will be the basis of following numerical 3D numerical models of the Riardo Plain and can be a valuable tool in conceptualising similar mineral water areas.

Origin, yield and quality of the groundwater flows at high elevation in the Cimino volcano (central Italy) were examined. In this area, groundwater is geogenically contaminated by arsenic and fluoride, yet supplies drinking water for approximately 170,000 inhabitants. The origin of the high-elevation groundwater flows is strictly related to vertical and horizontal variability of the rock types (lava flows, lava domes and ignimbrite) in an area of limited size. In some cases, groundwater circuits are related to perched aquifers above noncontinuous aquitards; in other cases, they are due to flows in the highly fractured dome carapace, limited at the bottom by a low-permeability dome core. The high-elevation groundwater outflow represents about 30% of the total recharge of Cimino’s hydrogeological system, which has been estimated at 9.8 L/s/km². Bicarbonate alkaline-earth, cold, neutral waters with low salinity, and notably with low arsenic and fluoride content, distinguish the high-elevation groundwaters from those of the basal aquifer. Given the quantity and quality of these resources, approaches in the capture and management of groundwater in this hydrogeological environment should be reconsidered. Appropriate tapping methods such as horizontal drains, could more efficiently capture the high-elevation groundwater resources, as opposed to the waters currently pumped from the basal aquifer which often require dearsenification treatments.

La eficacia del helecho de agua Azolla para eliminar polifenoles y reducir la demanda química de oxígeno (DQO) de los alpechines obtenidos en el proceso de obtención tradicional y continuo del aceite de oliva, fue investigado mediante ensayos de filtración. Cinco conos secuenciales de Imhoff y cinco columnas secuenciales se rellenaron de biomasa de Azolla. En ambos experimentos, el filtrado procedente de la quinta extracción mostró una disminución en el contenido de polifenoles de 7650 mg/L a 3610 mg/L en el alpechín obtenido mediante el sistema tradicional y de 3852 mg/L a 1351 mg/L en el alpechín del sistema continuo. La demanda química de oxígeno del alpechín del sistema tradicional disminuyó de 110200 mg/L a 52400 mg/L en y de 41600 mg/L a 2300 mg/L en el procedente del sistema continuo. Una proporción en peso 5:1 de alpechín:Azolla fue la óptima tanto para la reducción de los polifenoles como para la de la DQO. La eficiencia del tratamiento biológico con alfalfa se comparó con la obtenida con Azolla. Los resultados indicaron que el tratamiento con alfalfa no dio lugar a la reducción de los polifenoles ni de la DQO. | We investigated the biofiltration ability of the aquatic fern Azolla to remove polyphenols and chemical oxygen demand (COD) from olive mill wastewater (OMWw) collected from the traditional (TS) and continuous (CS) extraction systems. Azolla biomass was packed into five sequential Imhoff cones and five sequential columns. In both experiments, the filtrates collected from the 5th biofilter showed a decrease in polyphenol contents: from 7650 mg/l to 3610 mg/l in TS OMWw and from 3852 mg/l to 1351 mg/l in CS OMWw. The COD contents decreased from 110200 mg/L to 52400 mg/L in TS OMWw and from 41600 mg/L to 2300 mg/L in CS OMWw. A 5:1 OMWw to Azolla-fresh-weight ratio was optimal for both polyphenol and COD removal. The biofiltration ability of alfalfa was compared with that of Azolla, but the treatment with alfalfa did not result in the reduction of COD or polyphenols.

Introducing the time variable in groundwater vulnerability assessment is an innovative approach to study the evolution of contamination by non-point sources and to forecast future trends. This requires a determination of the relationship between temporal changes in groundwater contamination and in land use. Such effort will enable breakthrough advances in mapping hazardous areas, and in assessing the efficacy of land-use planning for groundwater protection. Through a Bayesian spatial statistical approach, time-dependent vulnerability maps are derived by using hydrogeological variables together with three different time-dependent datasets: population density, high-resolution urban survey, and satellite QuikSCAT (QSCAT) data processed with the innovative dense sampling method (DSM). This approach is demonstrated extensively over the Po Plain in Lombardy region (northern Italy). Calibrated and validated maps show physically consistent relations between the hydrogeological variables and nitrate trends. The results indicate that changes of urban nitrate sources are strongly related to groundwater deterioration. Among the different datasets, QSCAT-DSM is proven to be the most efficient dataset to represent urban nitrate sources of contamination, with major advantages: a worldwide coverage, a continuous decadal data collection, and an adequate resolution without spatial gaps. This study presents a successful approach that, for the first time, allows the inclusion of the time dimension in groundwater vulnerability assessment by using innovative satellite remote sensing data for quantitative statistical analyses of groundwater quality changes.

Irrigation in low-lying coastal plains may enhance the formation of fresh groundwater lenses, which counteract salinization of groundwater and soil. This study presents seasonal dynamics of such a freshwater lens and discusses its influence on the salinity distribution of the unconfined aquifer in the coastal plain of Ravenna, Italy, combining field observations with numerical modeling (SEAWAT). The lens originates from an irrigation ditch used as a water reservoir for spray irrigation. The geometry of the freshwater lens shows seasonal differences because of freshwater infiltration during the irrigation season and upconing of deeper saltwater for the remainder of the year. The extent of the freshwater lens is controlled by the presence of nearby drainage ditches. Irrigation also results in a temperature anomaly in the aquifer because of the infiltration of warm water during the irrigation season. The surficial zone in the vicinity of the irrigation ditch is increased considerably in thickness. Finally, different irrigation alternatives and the influence of sea-level rise are simulated. This shows that it is necessary to integrate irrigation planning into the water management strategy of the coastal zone to have maximum benefits for freshening of the aquifer and to make optimal use of the existing infrastructure.