1,720,992 research outputs found
Geological 3D model for the design of artificial recharge facilities into the Oued Biskra inféro-flux aquifer (NE Algeria)
No full textNorth Africa arid regions of Maghreb suffers of dry climatic conditions with erratic behaviour of rainfall in which most part of available superficial waters is lost, providing scarce benefits for households living in villages of such semidesertic areas.
Oued Biskra watershed (NE Algeria) is one of two study areas implemented in WADIS-MAR demonstration project (www.wadis-mar.eu) founded by European Commission through SWIM Programme (www.swim-sm.eu). North to the city of Biskra the river bed is imposed on Mio-Plio-Quaternary deposits and the alluvial sediments constitute a phreatic aquifer called inféro-flux (AA.VV., 1980). The aquifer is overexploited for drinking water and irrigation purposes, therefore the aquifer artificial recharge systems were designed in order to increase the sustainable yield of the aquifer and to store water underground when available and to employ it when needed.
Using the software Move (Midland Valley Exploration Ltd.) a preliminary 3D hydro-geological model, based on geological, hydro-geological and sub-surface data, a 30 meters Aster DEM and photo-interpretation, was made to better understand the hydro-geological setting of the inféro-flux aquifer. This study investigated 4 kilometres of the oued Biskra. Through 28 geological cross sections orthogonal to the river bed the 3D model of the alluvial aquifer was reconstructed. It is made up by alluvial deposits, mainly sand and gravel, with thickness that increases from 20 metres in the North to 80 metres in the South. In order to estimate the storativity, from sub-surface data we inferred an effective porosity value of 30%.
Based on the hydro-geological model an aquifer artificial recharge system was designed, consists by:
· 6 dry recharge wells: they will have a diameter ranging from 2 to 3 meters and a depth from 5 to 10, according to local setting of wadi bed and alluvial aquifer. From each well, three buried drainage pipes will depart to maximize the infiltration rates;
· 6 recharge trenches: they will be arrange perpendicular to the flow direction in cascade in a v-shape manner;
· 3 recharge basin: they will permit the infiltration of excess water conducted by buried pipes from the recharge wells. Its shape will be built as an inverted pyramid and built in slightly higher areas of the wadi bed to be sure to not being affected by superficial flow.
Groundwater pollution will be prevent using a “reactive layer”, a palm leaves compost with clay and sand to improve the quality of infiltrating water, that will work as a filter. The evaluation of the artificial recharge yield according the above described system, considering the occurrence of water along the oued for 20 days per year, is 1.5 million cubic metres per year
Metodologia per la caratterizzazione spettrale delle superfici saline e delle aree interessate da aspersioni sabbiose tramite proximal sensing e remote sensing in Tunisia
No full textLo studio presenta i primi risultati di una ricerca svolta nell’area di Medenine, Tunisia meridionale,
mirata alla caratterizzazione spettrale delle superfici saline e delle aree interessate da aspersioni
sabbiose, di particolare interesse poichè limitano le attività agro-pastorali. Sono stati acquisiti i dati
spettrali con uno spettroradiometro da campo e parallelamente sono stati prelevati campioni da
sottoporre ad analisi diffrattometriche. I punti di campionamento sono stati scelti sulla base
dell’analisi morfologica, dei dati spaziali ancillari e della mappatura di copertura/uso del suolo
specificatamente realizzata per questo studio su imagini Landsat 8. Il settore analizzato (400 000
ettari) è stato validato con una campagna a terra di 400 punti di controllo. La campagna spettrale ha
permesso l’acquisizione delle misure di riflettanza di 34 punti, di cui 14 punti per le superfici saline
(con 9 campioni); 10 punti per le aree di aspersioni sabbiose (10 campioni); 3 punti per la
vegetazione specifica (sia alofita, che psammofita) e 7 punti per superfici miste. Le firme spettrali
acquisite sono state elaborate per essere importate nella piattaforma web SPECCHIO per il
confronto con misure acquisite in ambienti simili. Le analisi difrattometriche sono state concluse
per i campioni salini e hanno permesso di definire la componente mineralogica specifica della
risposta spettrale rilevata sul campo. Questo studio propone un modello di analisi spettrale basato
sull’utilizzo integrato di dati acquisiti da proximal e remote sensing finalizzato al monitoraggio dei
fenomeni di land degradation. Lo studio presentato fa parte delle attività del progetto WADISMAR,
un progetto dimostrativo finanziato dalla Commissione Europea attraverso il Sustainable
Water Integrated Management (SWIM) Programme (http://www.wadismar.eu).This paper presents the preliminary results of a research carried out in the Medenine area,
Southern Tunisia, aimed at the spectral characterization of salt-affected and sand encroachment
areas, as restrictive factors for agro-pastoral activities. Spectral data was acquired in situ using a
handheld spectroradiometer and samples were taken for X-ray diffractometric analysis. The
sampling sites were chosen on the basis of a morphological analysis, ancillary data and a land
cover/land use map specifically generated for this study employing Landsat 8 imagery. The study
area (400 000 hectares) has been validated with 400 ground truth points. The spectral campaign
has enabled the acquisition of spectral reflectance measurements of 34 points, of which 14 points
for saline surfaces (9 samples); 10 points for sand encroachment areas (10 samples); 3 points for
typical vegetation (halophyte and psammophyte) and 7 points for mixed surfaces. The acquired spectral signatures were processed to be integrated into the web platform SPECCHIO for
comparison with measurements acquired in similar environments. Diffractometric analyses were
completed for the saline samples and allowed the identification of the main mineralogical
components. This study proposes a methodology based on the integrated spectral data acquired
through proximal and remote sensing aimed at monitoring of land degradation phenomena. The
study is part of the WADIS-MAR, a demonstration project funded by the European Commission
through the Sustainable Water Integrated Management (SWIM) Programme
(http://www.wadismar.eu)
Preliminary results of a 3-D groundwater flow model in an arid region of NE Algeria using PMWin: the Inféro-flux phreatic aquifer (Biskra)
No full textInféro-flux phreatic aquifer (Biskra, NE Algeria) is overexploited for irrigation and drinking water purposes since the fifties. The effect is a quali-quantitative deterioration of the groundwater resources mostly due to an insufficient natural recharge. WADIS-MAR Project aims to the realization of a Managed Aquifer Recharge (MAR) in the Biskra area in order to contribute to re-pressuring the piezometric level of the Inféro-flux. Groundwater flow models can contribute to the understanding of the groundwater behaviour related to the impact of existing and future activities on groundwater resources including the realization of an MAR system. In this work, the preliminary results for a groundwater flow model developed for the Inféro-flux aquifer are presented. They include the model construction and the results of the steady state calibration based on the piezometric head measured in 1966
Numerically Enhanced Conceptual Modelling (NECoM) applied to the Flumendosa Plain groundwater system (SE Sardinia, Italy)
Full text linkThe 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).
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.
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 foxi. 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
Mm3/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
Land Cover Change Modeler: indicatori di trasformazione del territorio come driver per il monitoraggio della salinizzazione in un settore dell’Algeria
No full textQuesto studio ha come obiettivo la valutazione del trend spaziale di cambiamento della copertura e uso del suolo in un’area arida e semiarida del Nord Africa, nonché il potenziale di transizione da una classe di copertura del suolo ad un’altra considerando vari indicatori ambientali, culturali e socio-economici. Tali indicatori possono costituire i drivers per la costruzione degli scenari di evoluzione spaziale e temporale della salinizzazione dei suoli nel territorio dell’Oued Biskra in Algeria. Lo studio presentato fa parte delle attività del progetto dimostrativo WADIS-MAR, finanziato dalla Commissione Europea attraverso il Sustainable Water Integrated Management (SWIM) Programme (http://www.wadismar.eu). Partendo dalle mappe di land cover (LC) e salinizzazione elaborate da dati satellitari Landsat, sono stati testati alcuni algoritmi dedicati al Land Change Modeler (LCM). Lo studio si basa su un’analisi multitemporale di dati Landsat che ha portato allo sviluppo di un classificatore di tipo Decision Tree dedicato al riconoscimento delle aree salinizzate in ambiente arido e semiarido (Melis et al., 2013; Afrasinei et al., 2015). Questo classificatore è stato testato in particolare nel settore dell’Oued Biskra (Algeria orientale) lungo il limite settentrionale del sistema morfologico sahariano. La metodologia adottata propone di utilizzare queste mappe come base per la predizione degli scenari di evoluzione del fenomeno della salinizzazione. Tale fenomeno appare fortemente controllato dalle dinamiche sociali ed economiche legate all’utilizzo intensivo del territorio per l’agricoltura e in particolare per le coltivazioni di palme da dattero. Inoltre in questi ambienti il clima e le condizioni biofisiche locali hanno un’influenza immediata sulle variazioni di land cover anche con impatto giornaliero, pertanto questo tipo di driver, estremamente variabile, deve essere considerato nella sua dinamicità in modo differente rispetto ai parametri stabili nel tempo quali la morfologia e la litologia e rispetto a quelli a variabilità media come quelli socio-culturali ed economici
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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