1,720,958 research outputs found
Model based quantification of salinization dynamics under changing hydrological conditions in the Volturno River (Italy) coastal aquifer
Full text linkThis work presents a semi-coupled modelling approach to study salinization dynamics in the Volturno River coastal aquifer (Italy), distinguishing among different salinization mechanisms. The area is of particular interest, given its location in the Mediterranean region, a climate change hot-spot. A 1D HEC-RAS numerical model was built up and run for a decade (2010-2020) to quantify the areal extent and timing of salinization events due to seawater encroachment within the Volturno River mouth. The results were used as input in a 3D SEAWAT model that incorporated salinity variations on a monthly basis for the same period. The SEAWAT model was down-scaled from a large calibrated MODFLOW model of the whole Campania region. Both national and worldwide databases were used to constrain the models. The model was then compared with 9 high resolution vertical profiles of porewater salinity obtained using a continuous coring sediment sampler, providing good model performance indicators (R2 = 0.867, NSE = 0.808, and RMSE = 3.926 g/L). Results highlight an increasing groundwater salinization pattern due to intrusion from the Volturno riverbed. The classical mechanism of seawater wedge intrusion from the coastline was minimal, while large inland portions of the model domain were characterized by high salinity (up to 75 g/l) due to remnant paleo seawater trapped into peaty and silty-clay aquitards. This physically-based modelling approach could be replicated in any coastal porous aquifer (if hydrological and hydrogeological datasets are available) to identify and quantify the salinization mechanisms and to help water managers to implement tailored solutions in the most affected areas
Seawater intrusion assessment along the Volturno River (Italy) via numerical modeling and spectral analysis
Full text linkSurface and groundwater salinization are becoming a significant challenge to inland water quality, negatively affecting people and ecosystems in coastal areas. Even if rivers provide critical pathways for seawater intrusion, this salinization phenomenon has received relatively little attention compared to other salinization mechanisms. To assess the distribution of salinity along the final reach of the Volturno River (Italy), an entire hydrologic year was modeled using the HEC-RAS software. The model was fed with high resolution time-series measurements (time interval of 10 min) of water surface elevations at both river mouth and Cancello Arnone (a hydrometric station located 13 km inland). Field observations and remote sensed data were used to perform the hydrody-namic analysis. The model showed good performance indicators (R2 = 0.878, NSE = 0.870, and MAE = 0.037 m) and well caught hydrometric variation over the simulation period. The tidal component was affected by dissi-pation moving upstream and showed the capability to shape the salinity profile during dry periods. Whereas during wet periods, even if a strong tidal component is present, the profile is totally regulated by the river discharge. The analysis of the salinity distribution, modelled via the Water Quality module, revealed the massive contribution of the river discharge in limiting seawater intrusion. A correlation between intrusion events and hydrometric stages was established over twenty years (2002-2022), showing a consistent trend between intrusion occurrence and the surface water storage anomaly in the lower Volturno River calculated by Global Land Data Assimilation System (GLDAS) model. Although the 1D approach here used may lead to uncertainties in the reproduction of the involved hydrodynamic and salinization processes, the results are useful for the under-standing of seawater intrusion in rivers, and may be utilized to study seawater intrusion in aquifers
Quantifying the impact of evapotranspiration at the aquifer scale via groundwater modelling and MODIS Data
Full text linkIn shallow alluvial aquifers characterized by coarse sediments, the evapotranspiration rates from groundwater are often not accounted for due to their low capillarity. Nevertheless, this assumption can lead to errors in the hydrogeological balance estimation. To quantify such impacts, a numerical flow model using MODFLOW was set up for the Tronto river alluvial aquifer (Italy). Different estimates of evapotranspiration rates were retrieved from the online Moderate Resolution Imaging Spectroradiometer (MODIS) database and used as input values. The numerical model was calibrated against piezometric heads collected in two snapshots (mid-January 2007 and mid-June 2007) in monitoring wells distributed along the whole alluvial aquifer. The model performance was excellent, with all the statistical parameters indicating very good agreement between calculated and observed heads. The model validation was performed using baseflow data of the Tronto river compared with the calculated aquifer-river exchanges in both of the simulated periods. Then, a series of numerical scenarios indicated that, although the model performance did not vary appreciably regardless of whether it included evapotranspiration from groundwater, the aquifer-river exchanges were influenced significantly. This study showed that evapotranspiration from shallow groundwater accounts for up to 21% of the hydrogeological balance at the aquifer scale and that baseflow observations are pivotal in quantifying the evapotranspiration impact
Unravelling the salinity origins in the coastal aquifer/aquitard system of the Volturno River (Italy)
No full textTo counteract the ongoing salinization of coastal aquifers, which poses a significant environmental and socioeconomic challenge to local communities, it is necessary to first understand the origin and mechanisms of this phenomenon. This study investigates the origins of salinity in the Volturno River lowland in Southern Italy and reveals that the primary source in the area is paleo-seawater entrapped within sediments that were subject to evapoconcentration processes. By systematically collecting sediment samples at variable depths and locations and extracting porewaters, a comprehensive understanding of the interplay between freshwater and saline water was gained, including complex patterns of vertical stratification of groundwater salinity. The study highlights the limitations of traditional methods that rely on salinity monitoring via integral depth sampling, particularly in capturing the vertical redox and salinity gradients characteristics of layered aquifer/aquitard systems. On the contrary, environmental tracers, like chloride and bromide, provide valuable insights into the sources of groundwater salinity, distinguishing between current seawater intrusion and other causes, such as paleoseawater and return flow from drained agricultural land. Results suggest that the majority of salinity does not originate from modern seawater intrusion or recent evaporation. Instead, it can be attributed to paleo-seawater affected by evapoconcentration processes. This study has broader implications for the sustainable management of coastal aquifers and the safeguarding of freshwater resources. While our findings are specific to the Volturno River coastal area, the methodologies and insights here presented can be reproduced in every coastal region facing similar salinity challenges
Groundwater-surface water interaction revealed by meteorological trends and groundwater fluctuations on stream water level|Interazione acque sotterranee-acque superficiali rivelate dalle tendenze meteorologiche e dalle fluttuazioni delle acque sotterranee sul livello di un corso d’acqua
No full textThe importance of considering groundwater (GW) and surface water (SW) as a single resource of two interconnected components has rapidly increased during the last decades. To investigate GW-SW interaction in an aquifer system exploited by several pumping wells, an integrated continuous monitoring of the hydrological conditions was carried out. The sub-catchment (14 km2), located in the Aspio basin near Ancona (Central Italy), is drained by a small stream named Betelico, and it is characterised by the presence of an unconfined alluvial aquifer and a semi-confined limestone aquifer. The aim of this study is to evaluate the drivers of stream drying up occurred during the last couple of years. This has been achieved by applying a trend analysis on rainfall, air temperatures, piezometric and stream level, and well pumping rates. Precipitation trends were analysed over a 30-years period through the calculation of the Standard Precipitation Index (SPI) and through heavy rainfall events frequency plots, while the correlation between piezometric stream levels and pumping rate was analysed during the last six years. The groundwater level was compared with the stream baseflow level, highlighting the interconnection between GW-SW over the years. The analysis on the water surplus (WS) trend, together with the rainfall events characterisation, supports the hypothesis of the decrease in recharge rate as the main driver of the stream drying up. This case study stresses the importance of studying GW-SW interactions in a continuously changing climatic context characterised by a decreasing precipitation trend, coupling both the advantages of a robust method like trend analysis on time series and the field continuous monitoring
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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