1,354,992 research outputs found
Rapti-Caputo, D. (2007): Palaeo-channels and groundwater vulnerability: some considerations.
No full textIn order to define the role played by both superficial and buried palaeo-channels within the alluvial plain of the River Po, Northern Italy, aimed to determine the intrinsic vulnerability of the aquifer systems, geomorphological, lithological, hydrogeological and geochemical data have been analysed. In particular, the relationships of these sedimentary bodies with the intrinsic vulnerability and the diffusion of polluting substances in the underground water resources have been investigated.
In the eastern sector of the Po Plain and especially in the broader area surrounding Ferrara, the dominant geomorphological features are the numerous palaeo-channels. Along the natural levees of these abandoned river courses several archaeological and ancient sites were established. The space distribution of these prevailingly sandy bodies strongly influences the hydrodynamic behaviour of the aquifers as, for example, the geometrical characteristics of the superficial unconfined hydrogeological units. Indeed, along the axis of these geomorphological features the intrinsic vulnerability has been estimated to be high to extremely high (70-90%). In fact, in this superficial aquifer, important concentrations of chlorides have been detected and especially the sulphates and nitrates exceed the drinkableness limits, therefore indicating the qualitative decay of this resource mainly due to farming activities.
The occurrence of sandy bodies also influences the vulnerability of the underlying confined aquifer that represents the main source exploited for the waterworks of the surrounding territory.
When the axis of the principal palaeo-channels coincides with the present-day hydrographic network, as in the case of the Po di Volano, a hydraulic barrier with constant pressure is generated. As a consequence, the continuous mixing phenomena occurring between superficial and underground waters can either improve or worsen the quality of the water resources.
Moreover, in this complex system, the determination of the intrinsic vulnerability of the aquifer bodies is one of the fondamental parameters to be determined before any strategic decision is taken for the integrated managment and protection of the underground resources and the environment
Hydrogeology of a Volcano-Sedimentary Multi-Aquifer System: The Skydra, Northern Greece, Case Study
No full textDue to climate change, water scarcity, and overexploitation of aquifers, the sustainable management and protection of groundwater resources will be one of the main challenges in the future. Therefore, the knowledge of hydrogeological characteristics, which must be as robust as possible, becomes crucial for defining groundwater management plans. On the other hand, the earliest evidence of the fertile plains and abundant water resources of Skydra and its surroundings dates back to the Neolithic period (6500-3200 B.C.), confirming the area's current agricultural vocation and productivity. In this perspective, the aim of the present study is to define the conceptual hydrogeological model of a complex confined multi-aquifer system characterizing the volcano-sedimentary deposits of the Skydra area, northern Greece. In particular, the architecture of the hydrostratigraphic units, the hydraulic parameters, and the hydrodynamic behavior of the multi-aquifer system were analyzed. The geological, geomorphological, and structural evolution affecting the area has influenced the geometric and hydraulic characteristics of the aquifer, and consequently its productivity. The thickness of the multi-aquifer system varies between 25.0 and 94.5 m and the hydraulic conductivity, calculated through the analysis of data from 72 pumping tests, and the application of empirical method (42 wells), ranges between 2.2 10-6 and 2.5 10-3 m/s. Higher hydraulic conductivity values are calculated in areas where tuffaceous formations are fractured and/or interlayered with sandy layers; while lower values occur where tuffs present only primary porosity and are interspersed with frequent clay layers. In the central area, due to overexploitation of the aquifer, an annual piezometric level drop of approximately 6 m has been recorded. The information acquired could serve as the basis for the sustainable development of groundwater resources in the test area and could also be applied in other similar hydrogeological settings
Transitorium
No full textThe poems of Vassiliki Rapti … are appropriate for a kind of music of modern syncopated rhythms. Their diversity is their charm since they can be read also with their own particular minimal music. This poetry is both Alexandrian in the epigraphic style and graphic in the modernist style. Their appearance is their content, humorous and playful. A pleasure to read.
Nanos Valaoritis
Author of My Afterlife Guarantee
A deep multiaquifer system: an integration of geophysical and hydrogeological data.
No full textThe need for good quality fresh water is becoming a global emergency, for both growing exploitation and pollution of water resources. As far as groundwater resources are concerned, they can be threatened both for pollution by human activities, especially in the recharge areas, and, in many cases of overexploitation, by the rising up of deep brackish/salt water. Saving this precious resource demands detailed knowledge of the subsurface, of the potential sources of pollution and of the equilibrium between exploitation and recharge processes. At the same time information about the whole sequence of aquifer bodies at the greatest depths becomes a strategic priority. Careful control and management activities should then be undertaken by public Authorities.
In this spirit, in the western sector of the Friuli-Venezia Giulia region (northern Italy) analysis of a large amount of lithological, geomorphological, hydrological and hydrogeological data allowed us to define a) the principal aquifer system of the area down to a depth of about 500 m; b) the geometrical characteristics of the aquifers (thickness, lateral extension,..); c) the hydraulic parameters (permeability, transmissivity); and d) the vulnerability to pollution of each aquifer system. The studied area was chosen since it is characterized by a rich but vulnerable groundwater reservoir, generally composed of several aquifer bodies, each of them giving abundant and good-quality fresh water.
In a selected portion of the area, where many holes were drilled for fresh water supply, the conceptual hydrogeological model was integrated by a detailed and repeated three-dimensional (3D) seismic and resistivity survey. The 3D resistivity models, which are described in this paper, were obtained using combined Electrical Resistivity Tomography (ERT) and Time-Domain ElectroMagnetic soundings (TDEM). Two 2D ERT’s and two 3D ERT’s were carried out, mainly aimed at furnishing detailed information about geometry and porosity of the overburden and to calibrate the shallowest TDEM information. The TDEM survey was composed of 15 soundings, located at a mean distance of 200 m, which were repeated in two presumably different hydraulic recharge-exploitation regimes. TDEM data were inverted using a 1D smooth inversion scheme and the 1D models were stacked together to get a local 3D model of the resistivity distribution. Reliable results about the geometry of deepest aquifer were obtained, which were confirmed by a purposedly drilled deep bore-hole. The repeated TDEM surveys show resistivity variations in the exploited aquifers which are in good agreement with direct hydrogeological information
Geochemical exploration of a volcano-sedimentary aquifer system in northern Greece
No full textIn this note, hydrochemical data from a volcano-sedimentary aquifer of the Skydra region, Northern Greece, are
analysed following an integrated approach, where results obtained with classical hydrochemical methods (saturation index, mixing diagram, characteristic relationships) are compared with those obtained from multivariate statistical technique correspondence analysis (R-mode factor analysis). From several groundwater samples collected from bore-wells the pH, the total dissolved solid, the electrical conductivity, the temperature and the major ions (Ca, Mg, Na, K, SO4, NO3, HCO3, Cl and SiO2) were measured. Within the investigated area, different hydrochemical facies have been recognised, basically generated by different geological formations but also induced by human activities. In order to characterise the different facies and to infer the relationships among them, thirteen parameters are chosen and elaborated by applying multivariate analyses. Accordingly, the chemical data of the aquifers can be grouped following five major factors which best fit the total variance of the data. These factors indicate the alimentation area and the influence of the regional geology for the hydrochemical characteristics of the principal aquifer systems
Caratterizzazione qualitativa dei serbatoi acquiferi
No full textLe caratteristiche quantitative e qualitative del patrimonio idrico sotterraneo di un territorio (acquiferi) dipendono da molteplici fattori che possono essere suddivisi in due gruppi principali:
Il primo gruppo comprende fattori naturali, o primari, come quelli geologi che condizionano le caratteristiche geometriche degli acquiferi (es. spessore, estensione), idrauliche (porosità, permeabilità), ed idrogeochimiche, conseguenza del contatto tra la matrice solida (sedimenti) e fluidi (acqua).
Il secondo gruppo, invece, include fattori antropici, o secondari, che possono provocare, da una parte, il degrado quantitativo delle risorse idriche sotterranee (come gli emungimenti eccessivi e non controllati per soddisfare, ad esempio, le esigenze acquedottistiche, agricole ed industriali) e, dall’altra parte, possono accelerare i processi di degrado qualitativo causato dall’eccessivo aumento delle fonti potenziali di inquinamento, sia puntuali che diffuse.
In particolare, nel sottosuolo ferrarese, a causa della complessa evoluzione geologica, le risorse idriche sotterranee sono fortemente condizionate e limitate sia qualitativamente che quantitativamente dalla presenza di sedimenti permeabili deposti in ambienti lagunari, deltizi o marini. In questo tipo di sedimenti, si trovano comunemente acque primarie (i.e. sinsedimentarie), generalmente con caratteristiche salmastre che presentano, pertanto, bassi valori di resistività elettrica, generalmente minori di 5 Ohm*m, ed elevata salinità.
Sulla base di numerose colonne stratigrafiche relative a pozzi per acqua e per la ricerca di idrocarburi (AGIP, 1972; SQUARZANTI, 1980) è stato possibile ricostruire, per la prima volta, l'andamento della zona di dispersione dove si verifica il passaggio graduale tra acqua dolce ed acqua salmastra, ponendo il limite in corrispondenza di valori di salinità pari a 1 g/l. Tale limite si trova a profondità variabili da pochi metri dal piano campagna, nell'area di Casaglia (20 m), a profondità di circa 50 m, nella zona di Baura, ad i 300 m, nei pressi di Copparo (VILLA et alii, 1976; SQUARZANTI, 1980).
Negli anni successivi, sono state realizzate poche ricerche di carattere locale che generalmente hanno affrontato problematiche di carattere idrogeologico ed idrogeochimico. La ricerca qui descritta ha avuto come scopo principale la ricostruzione, per l'intero territorio provinciale, del comportamento e dell'evoluzione, sia idrodinamica che geochimica, delle risorse idriche sotterranee. A tal fine, è stato utilizzato un protocollo di lavoro che comprende l'analisi integrata di dati di carattere stratigrafico, idrogeologico e geochimico.
Sulla base dei dati stratigrafici e fino alla profondità massima di 200 m, nel sottosuolo ferrarese sono state distinte cinque unità idrogeologiche corrispondenti all’acquifero a falda libera (A0), all'acquifero A1, generalmente in pressione e, agli acquiferi più profondi A2, A3 e A4, sempre in pressione. Le caratteristiche geologiche di questi acquiferi sono state descritte in precedenza (vedi Cap. I, § 1.3).
Per la definizione della rete di monitoraggio dei pozzi che riesce a descrivere il comportamento idrodinamico e geochimico degli acquiferi ferraresi in pressione, ci si è basati sulla raccolta e sull’elaborazione di dati provenienti dall'archivio dell'ARPA e raccolti sia dalla rete di controllo attiva che da quella inattiva. Inizialmente, sulla base dell’elaborazione dei dati stratigrafici ed adottando criteri geometrici, litologici e di “capacità idrica” delle diverse formazioni, sono stati individuati i principali corpi acquiferi. Successivamente, ed utilizzando come criteri assoluti la descrizione litologica di ogni singolo pozzo e la posizione dei filtri, è stata effettuata una divisione ed una scelta dei pozzi per ogni corpo acquifero come questo è stato definito nella fase precedente. In tal modo, sono stati esclusi tutti i punti di misura e/o di campionamento per i quali non esiste una dettagliata descrizione stratigrafica, la posizione dei filtri oppure nel caso in cui i pozzi fossero filtrati in più acquiferi. Questo approccio metodologico ci ha permesso di distinguere nove pozzi filtrati esclusivamente nell’acquifero A1; sette pozzi in quello A2; un pozzo nell’acquifero A3 ed un pozzo in quello A4. Nei pozzi individuati esistono misure sistematiche della soggiacenza (profondità dell'acqua dal piano campagna), relative al periodo 1977-1998, con frequenza semestrale, mentre, solamente per alcuni di essi esistono informazioni relative allo stato chimico delle acque
Gharial abundance in Rapti river, Chitwan, Nepal
No full textGharial (Gavialis gangeticus) is a Critically Endangered crocodilian species whose abundance in Nepalese rivers are low due to the threat they face. We estimated gharial abundance in the Rapti River, one of the major rivers in Chitwan National Park (CNP) holding the largest numbers of gharials in Nepal. The Rapti River, running across the CNP, was divided into 18 segments, each measuring ~4 kilometers, and gharials were counted directly with three replicates. Gharial count data was analysed using an N-mixture model (negative binomial) and the overall occupancy of gharials was estimated using a single season occupancy model. Covariate effects were also investigated on gharial abundance. Our findings revealed that the Rapti River is home to 150 gharials (119 - 181), with a mean abundance of 8.3 (SD= 3.45) across each segment. The presence of humans and square of Rapti River depth were the significant covariates that had a negative and positive impact on gharial abundance, respectively. Similarly, the number of sandbank presence influenced the detection probability of gharials. Our study shows that gharial population estimation can be improved using the N-Mixture model. The overall gharial occupancy estimated using single season occupancy model was 0.84 (SD= 0.08), with a detection probability of 0.37 (SD =0.02). The management authority should concentrate on segments to minimize human disturbance (e.g., fishing, washing clothes, extraction of riverbed materials). If the gharial population in this river declines, their population in central Nepal will be threatened. Hence, we suggest designating the Rapti River section that passes across the CNP as a 'no extraction zone'.Microsoft Excel can open the data files.Funding provided by: National Trust for Nature Conservation (NTNC)*Crossref Funder Registry ID: Award Number: Funding provided by: ZSL Nepal*Crossref Funder Registry ID: Award Number:Crocodilians are typically aquatic, although they emerge from the water to bask on land during the winter months. Counting basking gharials has been used to determine their population number since it is a reliable and convenient approach. Crocodile surveys are most effective during the winter months, from November to March, when practically all individuals come out for basking and continue basking for extended periods of time, increasing the chance of sightings. Because it is mating season, breeding groups tend to congregate. Furthermore, gharials are less active during the winter months, restricting their frequent migration in our short survey time, implying that the gharial population would remain demographically closed during the course of the surveys, as needed by the occupancy model. As a result, we performed our research during the winter, from November 13 to December 13.
The Rapti River was thoroughly surveyed by dividing it into 18 of 4 kilometer length. Gharial sightings, habitat parameters, and anthropogenic pressure were recorded at every 200 m of each segment, for a total of 18*20= 360 sampling points. With two experienced observers and two boatmen, we used a dugout boat. Each segment was surveyed three times with binoculars to look for gharials, for a total of 1080 (360x3) points. Gharials were approached as closely as possible, and their sizes were determined visually. The Rapti River was thoroughly surveyed by dividing it into 18 of 4 kilometer length. Gharial sightings, habitat parameters, and anthropogenic pressure were recorded at every 200 m of each segment, for a total of 18*20= 360 sampling points. With two experienced observers and two boatmen, we used a dugout boat. Each segment was surveyed three times with binoculars to look for gharials, for a total of 1080 (360x3) points. Gharials were approached as closely as possible, and their sizes were determined visually. Then, we estimated gharial population size using a binomial N-mixture model and a single season occupancy model for gharial occupancy
Compact laser spectrofluorometer for water monitoring campaigns of Southern Italian regions affected by salinization and desertification processes.
No full textA compact laser spectrofluorometer has been developed and employed in the diagnosis of
water quality parameters in the frame of the Italian project Integrated Research for Applying
new technologies and processes for combating DEsertification (RIADE). The instrument has
been designed to be autonomously operated in field campaigns as that conducted in the
groundwater-bearing areas of Licata (Southern Italy), affected by high salinity contents
induced by the Salso river and by coastal seawater intrusion phenomena. Dissolved
(chromophoric dissolved organic matter, tyrosine and tryptophan) and particulate (algae)
matter was monitored during the abovementioned field campaign (May 2005) in different
wells within the countryside around the Licata area. Measurements of that monitoring activity
were therefore compared to: a) the groundwater depth of wells, b) the in situ measurement of
chemical-physical parameters (electrical conductivity, pH and temperature) and c) the
geochemical composition of the groundwater. The results stress the reduction of water retain
due to salt releases in the aquifers. Georeferenced maps of the measured parameters are
presented and discussed
Evoluzione geochimica e modalità di gestione di un acquifero alluvionale
No full textIn the eastern hydrographic basin of the Po river, Northern Italy, the underground water circulation is strongly
influenced by the recent geological and palaeogeographic evolution of the region, while the qualitative characteristics of the
water are controlled by the depositional environment (continental, marine, etc.). Within such complex sedimentary
environments, the exploitation mode plays a crucial role for the preservation of the overall aquifer quality. In order to
evaluate the influence of the exploitation on the geochemical characteristics of the underground resources, hydrodynamic
(piezometric level) and hydrochemical (Ph, temperature, electrical conducibility, content in HCO3, Ca, NH4, Fe, Mn, SO4,
Cl, NO3, Cl, F and Br) data have been collected from the first unconfined aquifer and analysed. The investigated area
corresponds to the territory surrounding Ferrara town. The elaboration of these data based on classical hydrogeological and
hydrogeochemical methods, integrated with isotopic analyses allows a) to separate the principal hydrogeochemical facies,
b) to recognise the occurrence of mixing phenomena between the water of the exploited aquifer and the salty water of the
underlying aquifer, c) to infer about the equilibrium between the amount of pumping and the quality of the water
Groundwater fluorescence analysis in Southern Italian regions affected by desertification processes
No full textDesertification is the degradation of land in arid, semi-arid, and dry sub-humid areas and it is primarily due to human activities and climatic variations. Nowadays, this matter does not refer only to the expansion of existing deserts but it occurs because dryland ecosystems are extremely vulnerable to climate changes, over-exploitation and inappropriate land use.
In the Italian scenario, the impact of desertification is restricted to the southern regions where the risk is linked to water erosion, strong human aggressiveness, intense precipitations and to water and soil salinization.
To this respect, the Italian project RIADE (Integrated Research for Applying new technologies and processes for combating DEsertification), has selected the area of Syracuse and the alluvial plain of the Licata town for an integrated application of the hydrogeochemical and spectroscopical methods in order to settle on qualitative characteristics of the water resources.
Laser Induced Fluorescence (LIF) spectroscopy has been chosen for its intrinsic skills to be employed in real time water quality parameter determinations, with portable instruments during intensive monitoring campaigns. This technique allows to perform qualitative and quantitative in situ determination of dissolved (humic and fulvic acids, pollutants) or particulate (phytoplankton) organic matter. The ENEA laser remote sensing laboratory has designed and developed a new portable instrument, in order to match the requests of monitoring skills on relevance sites for RIADE.
In the late Spring 2005 (May 22 – 25), a joint campaign has been performed in the Licata area (Sicily, Agrigento province), along the Salso river and in different wells in the neighbourhood territory. Distribution maps of the measured parameters as: a) dissolved matter, i.e. CDOM (Chromophoric Dissolved Organic Matter), tyrosine and tryptophan; b) particulate matter (algae); c) groundwater depth; d) electrical conductivity; e) pH; f): temperature; will be presented and discussed in term of emerging information on ongoing desertification processes
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