Southern Mediterranean Basin Research Articles

Groundwater potential recharge assessment in Southern Mediterranean basin using GIS and remote sensing tools: case of Khalled- Teboursouk basin, karst aquifer

Groundwater potential recharge assessment in Southern Mediterranean basin using GIS and remote sensing tools: case of Khalled- Teboursouk basin, karst aquifer

Heat index historical trends and projections due to climate change in the Mediterranean basin based on CMIP6

Air temperature and relative humidity can be considered as two essential meteorological parameters in the determination of heat stress. The heat index (HI) includes both of them and it is appropriate for determining the thermal conditions of different climates. We investigated potential changes in the HI for the Mediterranean basin using simulations from the Coupled Model Intercomparison Project Phase 6 (CMIP6) climate models under two future scenarios (Shared Socio-economic Pathways: SSP2-4.5 and SSP5-8.5) over the period 2020–2099. Results reveal an important increase of HI at the end of the 21st century for both scenarios, with greater changes for the SSP5-8.5 scenario all over the basin. Strong significant upwards trends (around 1 °C per decade; significance level computed at 5%) are expected in the entire area and for all months at the end of the century, with greatest values during the summer months (close to 1.5 °C per decade) along the coastal areas of the basin. Many areas of the Southern Mediterranean basin (Africa and Arabian Peninsula) will be strongly affected with dangerously high heat index values (higher than 41 °C) during summer months by the end of the 21st century. A northward extension of these dangerous conditions is also expected including several areas of southern Europe.

Microsatellites reveal high levels of genetic admixture in the natural populations of Laurus azorica, Lauraceae

Laurus (Lauraceae) species are currently restricted to isolated refugia in the southern Black Sea, Mediterranean Basin, southern Morocco, and Macaronesian archipelagos. One to three species of Laurus has been recognized: the Azorean endemic Laurus azorica, L. nobilis from the Mediterranean, and L. novocanariensis from Madeira and the Canary Islands. This study aims to determine the population structure, genetic diversity, and associated patterns of gene flow within and between Azorean populations, using eight existing SSR markers. We also included plant material from L. nobilis populations found in the Azores, for comparison. Amplification was performed in 212 samples of L. azorica and in 30 samples of L. nobilis. For L. azorica, 78 alleles were amplified (average 9.75 alleles per loci). Bayesian analysis with STRUCTURE unveiled five genetic groups for the Azorean accessions, with high level of genetic admixture. Genetic diversity was generally high, with moderate levels of genetic differentiation among L. azorica populations. Moreover, high gene flow levels, likely mediated by past human translocations and naturally, by birds, might have contributed to the high level of genetic admixture observed possibly reflecting hybridization events between L. nobilis and L. azorica. Conservation measures should be applied to some populations of São Miguel, Santa Maria, and Flores Islands, based on the number of private alleles, and further, ad hoc translocation events should be avoided. Conservation in situ and the preservation of laurel forest remains are recommended. The study of this species’ taxonomy, genetics, and population dynamics in the Macaronesian region should be continued.

Viticulture extension in response to global climate change drivers – lessons from the past and future projections

Abstract. The potential areal extent of agricultural crops is sensitive to climate change and its underlying drivers. To distinguish between the drivers of past variations in the Mediterranean viticulture extension since Early Antiquity and improve projections for the future, we propose an original attribution method based on an emulation of offline coupled climate and ecosystem models. The emulator connects the potential productivity of grapevines to global direct and indirect climate drivers, notably orbital parameters, solar and volcanic activities, demography, and greenhouse gas concentrations. This approach is particularly useful to place the evolution of future agrosystems in the context of their past variations. We found that variations in potential area for viticulture during the last 3 millennia in the Mediterranean Basin were mainly due to volcanic activity, while the effects of solar activity and orbital changes were negligible. In the future, as expected, the dominating factor is the increase in greenhouse gases, causing significantly drier conditions and thus major difficulties for viticulture in Spain and North Africa. These constraints will concern significant areas of the southern Mediterranean Basin when global warming exceeds +2 ∘C above preindustrial conditions. Our experiments showed that even intense volcanic activity comparable to that of the Samalas – sometimes considered to be the starting point of the Little Ice Age in the mid-13th century – would not decrease aridity and so not slow down this decline in viticulture extension in the southern margin of the Mediterranean area. This result does not confirm the idea of geoengineering that solar radiation modification (SRM) is an efficient option to limit future global warming.

Hydrogeological investigation of karst aquifers using an integrated geomorphological, geochemical, GIS, and remote sensing techniques (Southern Mediterranean Basin—Tunisia)

Hydrogeological investigation of karst aquifers using an integrated geomorphological, geochemical, GIS, and remote sensing techniques (Southern Mediterranean Basin—Tunisia)

Global bioregionalization of warm drylands based on tree assemblages mined from occurrence big data

Drylands represent about 41% of Earth’s land area, host more than 1,500 tree species and support more than 20% of the world’s human population. Trees are key to the functioning of numerous dryland ecosystems and contribute to goods and services for many local human communities, but many are threatened by global changes. From this perspective, mapping tree species assemblages of drylands can provide valuable information for conservation. To our knowledge, warm drylands, including hot deserts, have never been subject to a comprehensive tree biodiversity analysis independent of administrative boundaries or pre-defined regions. Our study aimed to address this gap by redefining warm drylands based on climate data and delineating bioregions using tree species assemblages at the global scale. We based the analyses on aridity and temperature data and a co-occurrence network approach using more than 1,000 tree species. Our data are mined from the Desert Trees of the World database, the Global Biodiversity Information Facility database, and the African Plant Database. This new delimitation of warm drylands reveals eight bioregions, covering about 19% of Earth’s land area across all continents. These are: North America, two bioregions in South America, the southern Mediterranean Basin and Macaronesian islands, the Saharo-Sindian region and the Horn of Africa, Southern Africa, the Socotra archipelago, and Australia. These bioregions have very distinct tree species assemblages, as well as high rates of endemism. This original diversity is found under a wide range of aridity conditions both within and between bioregions, offering the opportunity to anticipate different responses of tree assemblages face to future climate change among the world’s warm drylands. It will aid in conservation, restoration, and rehabilitation strategies involving the use of native trees among the most threatened regions worldwide.

Impacts of water stress on lagoonal ecosystem degradation in semi-arid coastal areas

The intensifying impacts of aridity and water stress on the dynamics and ecological degradation of wetlands in North Africa are often underestimated and largely remain unquantified. To address this deficiency, we assessed decadal changes in the sedimentary, sea surface salinity (SSS), and microfaunistic patterns of the Bizerte Lagoon, a climatically vulnerable area in the southern Mediterranean basin. Findings from sediment transport analysis indicate preferential current dispersion along the lagoon ridge associated with mixtures of sedimentary distributions. The changes in SSS between 2004 and 2016 reveal an increase of approximately 40% in areas where the river flows into the lagoon. Findings from the microfaunistic analysis suggest that over the last few decades, a progressive enrichment of alien marine species has occurred in the lagoon owing to changes in SSS and sedimentation. Results also revealed the unexpected presence of tropical to subtropical Larger B-bearing Foraminifera (LBF) species, which are exogenic to the warm southern Mediterranean coasts. The study findings highlight the impacts of damming and changes in precipitation patterns on the degradation of biodiversity in the Bizerte Lagoon and in other lagoonal systems in North Africa with similar levels of aridity.

Arab online news platforms: Innovating language, narratives, audiences and business models. Experiences from Lebanon and Jordan

This article analyses the rising relevance of online news platforms in the Arab region, particularly those created after the social uprisings that commenced in late 2010 in Tunisia and spread across the southern Mediterranean basin. As the online environment does not contemplate borders, the article refers to the term ‘Arab’, as these initiatives aimed at reaching regional audiences. However, the cases addressed in this article are based only in two countries, Jordan and Lebanon. The research focuses on four specific media start-ups: Raseef22 and Daraj in Lebanon, and 7iber and Sowt in Jordan. The selection of these news platforms integrated in the research exercise was not a simple task as many initiatives of this type were born in the last years such as Al Jumhuriya, MadaMasr and Inkyfada just to mention a few. The author has decided to follow objective aspects such as audience rates, business consolidation, external support from partners and the ability to reach new audiences, particularly young readers, which were not traditionally engaged in conventional media. The methodology to develop the present article has been based on structured interviews with the editors and/or founders of the analysed news platforms together with an analysis of the content that they produce. Research results demonstrate that despite the challenges and the difficulties to become economically sustainable, as well as the continuous political pressures suffered, these initiatives have been able to build unique narratives of unprecedented nature and innovative business models based on international agreements with global organizations. Therefore, they are becoming transformative drivers of journalism and critical thinking across the region, something that was unimaginable just few years ago.

Useful Life of Prescribed Fires in a Southern Mediterranean Basin: An Application to Pinus pinaster Stands in the Sierra Morena Range

Prescribed fire is a globally relevant fuel treatment for surface fuel management and wildfire hazard reduction. However, Mediterranean ecosystems are adapted to low and moderate fires; hence, the useful life of prescribed fires is limited. Useful life is defined as the effective rotation length of prescribed fires to mitigate fire spread based on critical surface intensity for crown combustion. In this sense, the useful life of a prescribed fire focuses on surface fuel dynamics and its potential fire behavior. In Pinus pinaster stands, the useful life can be established between 0 and 4 years. Canopy base height, time elapsed from the burning, postfire precipitation, and fine fuel moisture content during the burning were identified as the most important variables in postburn fuel dynamics. Other stand characteristics and postfire precipitation can improve the fine fuel and live fuel dynamics models. Our findings support prescribed fires as an effective fuel treatment in the medium term for forest fire prevention, according to stand characteristics and burning implementation conditions. In this sense, forest managers can use the proposed decision tree to identify the useful life of each prescribed fire based on fine fuel moisture content during burning implementation.

Identification of bacterial biofilms on desalination reverse osmosis membranes from the mediterranean sea

Nanofiltration and reverse osmosis are two of the most effective surface water treatment processes. They provide water of high quality and eliminate a large amount of microorganisms, organic matter and micropollutants. However, the main limitation of membrane nanofiltration is fouling, which imposes an additional cost. This study focused on the search for microorganisms capable of reducing the performance of nanofilters and also to study autoaggregation and biofilms formation by bacterial strains isolated from the nanomembranes used in the seawater desalination plant of Souk Tlata (Algeria). It provides new microbiological data on the desalination of seawater in the southern Mediterranean basin. The results revealed 14 bacterial species isolated from six fouled reverse osmosis membranes; their quantities were significant with the dominance of Raoultella sp., Klebsiella sp., Staphylococcus sp., Stenotrophomonas sp., Micrococcus sp., and Escherichia coli. In addition, electron imaging of nanomembrane surfaces revealed complex structures of microorganisms forming biofilms.

Climate variability during MIS 20–18 as recorded by alkenone-SST and calcareous plankton in the Ionian Basin (central Mediterranean)

This study shows the first Mediterranean high-resolution record of alkenone-derived sea surface temperature (SST) in the marine sediments outcropping at the Ideale section (IS) (southern Italy, central Mediterranean) from late marine isotope stage (MIS) 20 - through early MIS 18. The SST pattern evidences glacial-interglacial up to submillennial-scale temperature variation, with lower values (~13 °C) in late MIS 20 and substage 19b, and higher values (up to 21 °C) in MIS 19c and in the interstadials of MIS 19a. The SST data are combined with the new calcareous plankton analysis and the available, chronologically well-constrained carbon and oxygen isotope records in the IS. The multi-proxy approach, together with the location of the IS near the Italian coasts, the lower circalittoral-upper bathyal depositional setting, and high sedimentation rate allow to document long-and short-term paleoenvironmental modifications (sea level, rainfall, inorganic/organic/fresh water input to the basin), as a response to regional and global climate changes. The combined proxies reveal the occurrence of a terminal stadial event in late MIS 20 (here Med-HTIX), and warm-cold episodes (here Med-BATIX and Med-YDTIX) during Termination IX (TIX), which recall those that occurred through the last termination (TI). During these periods and the following ghost sapropel layer (insolation cycle 74, 784 ka) in the early MIS 19, high frequency internal changes are synchronously recorded by all proxies. The substage MIS 19c is warm but quite unstable, with several episodes of paleoenvironmental changes, associated with fluctuating tropical-subtropical water inflow through the Gibraltar Strait, variations of the cyclonic regime in the Ionian basin, and the southward shift of westerly winds and winter precipitation over southern Europe and Mediterranean basin. Three high-amplitude millennial-scale oscillations in the patterns of SST and calcareous plankton key taxa during MIS 19a are interpreted as linked to changes in temperature as well as in salinity due to periodical water column stratification and mixing.The main processes involved in the climate variability include changes in oceanographic exchanges through the Gibraltar Strait during modulations of Atlantic meridional overturning circulation and/or variations in atmospheric dynamics related to the influence of westerly and polar winds acting in the paleo-Ionian basin. A strong climate teleconnection between the North Atlantic and Mediterranean is discussed, and a prominent role of atmospheric processes in the central Mediterranean is evidenced by comparing data sets at the IS with Italian and extra-Mediterranean marine and terrestrial records.

Physicochemical Properties and Thermal Stability of Microcrystalline Cellulose Isolated from Esparto Grass Using Different Delignification Approaches

Esparto grass, known as alfa, is a renewable biomass widely distributed in southern and western Mediterranean basin. The present work focused on the isolation of pure cellulose from alfa stems, via different approaches, i.e., acidified sodium chlorite (NaClO2), totally chlorine free (TCF) or their combination, followed by the preparation of microcrystalline cellulose (MCC) using acid hydrolysis method. The obtained samples were characterized using infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry (TGA) and differential scanning calorimeter (DSC). The FTIR spectroscopy exhibited the removal of lignin and hemicellulose after the delignification and alkaline treatments. The XRD data showed that all of the MCCs have higher crystallinity indexes (Alfa-MCC 73–82%) and belong to cellulose I type. From SEM images, it is clear that the different MCC particles presented rough surface and micro-sized particles. The DSC/TGA analyses revealed that MCC samples present better thermal stability than their respective cellulose ones, with higher temperature of decomposition (more than 350 °C). Moreover, the use of a combined process yields to MCC with higher crystallinity and better thermal stability. Consequently, based on these findings, the delignification with combined method can be considered as a promising approach to extract MCC from alfa fibers with outstanding features.

A dish-stirling solar concentrator coupled to a seasonal thermal energy storage system in the southern mediterranean basin: A cogenerative layout hypothesis

In the future, renewable energy sources will increasingly represent an efficient energy source capable of meeting the demands of residential and industrial buildings avoiding the emissions of greenhouse gases into the atmosphere. In this paper, a heat and electric power cogeneration plant implementing a field of dish-Stirling collectors, a seasonal geothermal storage and a system of water-to-water heat pumps is proposed for the first time. The cogeneration plant has been designed both to supply thermal energy to the heating system of Building 9 of the Department of Engineering in Palermo and to produce electricity. The operation of the plant has been tested by means of hourly-based numerical simulations that have been carried out using a numerical model implemented with Transient System Simulation Tool. The experimental data of a pilot dish-Stirling collector, located in the same area, has been used to carefully calibrate the numerical model. Using energy and economic performance indicators, it was possible to select the best configurations among 1440 analysed cases. Results of simulations show that with the best plant configuration, it is possible to cover 97% of the building's annual thermal loads with energy produced by the solar system. The remaining 64% of electrical energy produced by the electric engines is free to be used for other applications. Financial analyses have shown that market penetration of this type of plant would need a strong support through incentives.

Carbonaceous Aerosols Collected at the Observatory of Monte Curcio in the Southern Mediterranean Basin

This work provides the first continuous measurements of carbonaceous aerosol at the Global Atmosphere Watch (GAW) Monte Curcio regional station, within the southern Mediterranean basin. We specifically analyzed elemental carbon (EC) and organic carbon (OC) concentrations in particulate matter (PM) samples, collected from April to December during the two years of 2016 and 2017. The purpose of the study is to understand the behavior of both PM and carbonaceous species, in their fine and coarse size fraction, along with their seasonal variability. Based on 18 months of observations, we obtained a dataset that resulted in a vast range of variability. We found the maximum values in summer, mainly related to the enhanced formation of secondary pollutants owing to intense solar radiation, also due to the high frequency of wildfires in the surrounding areas, as well as to the reduced precipitation and aerosol-wet removal. We otherwise observed the lowest levels during fall, coinciding with well-ventilated conditions, low photochemical activity, higher precipitation amounts, and less frequency of Saharan dust episodes. We employed the HYSPLIT model to identify long-range transport from Saharan desert. We found that the Saharan dust events caused higher concentrations of PM and OC in the coarser size fraction whereas the wildfire events likely influenced the highest PM, OC, and EC concentrations we recorded for the finer fraction.

Lectotype designation for Scilla undulata Desf. (Asparagaceae) from among the mixed original material

Scilla undulata Desfontaines (1792: 161) was described for plants occurring in Barbary, namely on the northern coastal areas of Tunisia and Algeria. The name has been applied to hysteranthous plants with undulate, glabrous leaves; inflorescence long racemose, usually loose; flowers pedicellate, stellate, with small, shortly spurred, deciduous bracts; perigone lobes linear to subspatulate, shortly fused at base, pinkish with a darker central band; capsules subquadrate to obovate-elliptic in outline, trigonous, appressed to the axis; seeds numerous, blackish, shinning, flattened, broadly winged (Maire 1958, Rico 2013). It is widespread mostly in the low land of the southern Mediterranean basin, from western Morocco to the Middle East, extending to southeastern Iberian Peninsula, Corsica and Sardinia (McNeill 1980, Tison & Foucault 2014, Bartolucci et al. 2018).

FRP-confined tuff masonry columns: regular and irregular stone arrangement

Fiber-Reinforced Polymer (FRP) represents one of the most diffuse and effective strengthening technique for retrofitting columns in existing buildings when presenting insufficient mechanical properties. In fact, the confinement effect provided by wraps with high-tensile strength and stiffness induces significant enhancement of the mechanical behaviour.In this paper experimental results of axial compression tests on both un-confined and FRP-confined prismatic yellow tuff masonry columns are presented. In particular, two types of masonry arrangements, regular and irregular, were reproduced in order to investigate the effectiveness of the confinement on column typologies widely used in the past in Southern Italy and Mediterranean basin. The performed experimental tests allowed to obtain the constitutive axial and transversal stress-strain laws and to evaluate the improvement of the mechanical behaviour, in terms of strength and ductility, due to FRP confinement. The results have highlighted a significant difference in the shape of the constitutive law for confined masonry with respect to the one of confined concrete.Contrary to FRP confined concrete members, in the case of confined masonry members specific theoretical constitutive model has been not yet developed. To this aim, in this paper the various stress-strain laws developed for FRP-confined concrete elements has been applied to masonry elements too and a comparative analyses between experimental and theoretical results has been carried out.

Modeling the biogeochemical impact of atmospheric phosphate deposition from desert dust and combustion sources to the Mediterranean Sea

Abstract. Daily modeled fields of phosphate deposition to the Mediterranean from natural dust, anthropogenic combustion and wildfires were used to assess the effect of this external nutrient on marine biogeochemistry. The ocean model used is a high-resolution (1∕12°) regional coupled dynamical–biogeochemical model of the Mediterranean Sea (NEMO-MED12/PISCES). The input fields of phosphorus are for 2005, which are the only available daily resolved deposition fields from the global atmospheric chemical transport model LMDz-INCA. Traditionally, dust has been suggested to be the main atmospheric source of phosphorus, but the LMDz-INCA model suggests that combustion is dominant over natural dust as an atmospheric source of phosphate (PO4, the bioavailable form of phosphorus in seawater) for the Mediterranean Sea. According to the atmospheric transport model, phosphate deposition from combustion (Pcomb) brings on average 40.5×10−6 mol PO4 m−2 yr−1 over the entire Mediterranean Sea for the year 2005 and is the primary source over the northern part (e.g., 101×10−6 mol PO4 m−2 yr−1 from combustion deposited in 2005 over the north Adriatic against 12.4×10−6 from dust). Lithogenic dust brings 17.2×10−6 mol PO4 m−2 yr−1 on average over the Mediterranean Sea in 2005 and is the primary source of atmospheric phosphate to the southern Mediterranean Basin in our simulations (e.g., 31.8×10−6 mol PO4 m−2 yr−1 from dust deposited in 2005 on average over the south Ionian basin against 12.4×10−6 from combustion). The evaluation of monthly averaged deposition flux variability of Pdust and Pcomb for the 1997–2012 period indicates that these conclusions may hold true for different years. We examine separately the two atmospheric phosphate sources and their respective flux variability and evaluate their impacts on marine surface biogeochemistry (phosphate concentration, chlorophyll a, primary production). The impacts of the different phosphate deposition sources on the biogeochemistry of the Mediterranean are found localized, seasonally varying and small, but yet statistically significant. Differences in the geographical deposition patterns between phosphate from dust and from combustion will cause contrasted and significant changes in the biogeochemistry of the basin. We contrast the effects of combustion in the northern basin (Pcomb deposition effects are found to be 10 times more important in the northern Adriatic, close to the main source region) to the effects of dust in the southern basin. These different phosphorus sources should therefore be accounted for in modeling studies.

Empirical model for predicting the inside air temperature of a naturally ventilated greenhouse with tomato crop, under hot and arid climates

The energy balance components of a greenhouse as well as the greenhouse design may strongly impact the greenhouse energy. Few studies were devoted to the description of the energy balance components of a greenhouse located in the semi arid region of the southern Mediterranean basin, and no attention was paid to the prediction of the inside air temperature. In this study, experiments were undertaken to investigate the response of a greenhouse to the outside climate conditions considering a naturally ventilated Venlo glasshouse with a tomato crop. The measurements show that the difference between inside and outside air temperature is strongly linked to the incoming solar radiation as well as to the wind speed. From these results a simplified model was established to predict the greenhouse air temperature, knowing the greenhouse characteristics and the outside climate variables. The model is based on the energy balance of the greenhouse. Using a parameter identification technique, the model was calibrated against the experimental results. A sensivity analysis was conducted to assess the impact of several physical parameters such as solar radiation, wind speed and cover transmission on the evolution of the inside air temperature. This model appears to be suitable for predicting the greenhouse air temperature satisfactorily.

Habitat- and soil-related drivers of the root-associated fungal community of Quercus suber in the Northern Moroccan forest.

Soil fungi associated with plant roots, notably ectomycorrhizal (EcM) fungi, are central in above- and below-ground interactions in Mediterranean forests. They are a key component in soil nutrient cycling and plant productivity. Yet, major disturbances of Mediterranean forests, particularly in the Southern Mediterranean basin, are observed due to the greater human pressures and climate changes. These disturbances highly impact forest cover, soil properties and consequently the root-associated fungal communities. The implementation of efficient conservation strategies of Mediterranean forests is thus closely tied to our understanding of root-associated fungal biodiversity and environmental rules driving its diversity and structure. In our study, the root-associated fungal community of Q. suber was analyzed using high-throughput sequencing across three major Moroccan cork oak habitats. Significant differences in root-associated fungal community structures of Q. suber were observed among Moroccan cork oak habitats (Maâmora, Benslimane, Chefchaoun) subjected to different human disturbance levels (high to low disturbances, respectively). The fungal community structure changes correlated with a wide range of soil properties, notably with pH, C:N ratio (P = 0.0002), and available phosphorus levels (P = 0.0001). More than 90 below-ground fungal indicators (P < 0.01)–either of a type of habitat and/or a soil property–were revealed. The results shed light on the ecological significance of ubiquitous ectomycorrhiza (Tomentella, Russula, Cenococcum), and putative sclerotia-associated/ericoid mycorrhizal fungal taxa (Cladophialophora, Oidiodendron) in the Moroccan cork oak forest, and their intraspecific variability regarding their response to land use and soil characteristics.

Hydrochemistry and stable isotopes (δ18O and δ2H) tools applied to the study of karst aquifers in southern mediterranean basin (Teboursouk area, NW Tunisia)

Karst aquifers receive increasing attention in Mediterranean countries as they provide large supplies water used for drinkable and irrigation purposes as well as for electricity production. In Teboursouk basin, Northwestern Tunisia, characterized by a typical karst landscape, the water hosted in the carbonates aquifers provides large parts of water supply for drinkable water and agriculture purposes. Groundwater circulation in karst aquifers is characterized by short residence time and low water-rock interaction caused by high karstification processes in the study area. Ion exchange process, rock dissolution and rainfall infiltration are the principal factors of water mineralization and spatial distribution of groundwater chemistry. The present work attempted to study karstic groundwater in Teboursouk region using hydrochemistry and stable isotopes (δ18O and δ2H) tools. Karst aquifers have good water quality with low salinity levels expressed by TDS values largely below 1.5 g/l with Ca-SO4-Cl water type prevailing in the study area. The aquifers have been recharged by rainfall originating from a mixture of Atlantic and Mediterranean vapor masses.