1,437 research outputs found

    Environmental risk assessment in the mediterranean region using artificial neural networks

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    Los mapas auto-organizados han demostrado ser una herramienta apropiada para la clasificación y visualización de grupos de datos complejos. Redes neuronales, como los mapas auto-organizados (SOM) o las redes difusas ARTMAP (FAM), se utilizan en este estudio para evaluar el impacto medioambiental acumulativo en diferentes medios (aguas subterráneas, aire y salud humana). Los SOMs también se utilizan para generar mapas de concentraciones de contaminantes en aguas subterráneas simulando las técnicas geostadísticas de interpolación como kriging y cokriging. Para evaluar la confiabilidad de las metodologías desarrolladas en esta tesis, se utilizan procedimientos de referencia como puntos de comparación: la metodología DRASTIC para el estudio de vulnerabilidad en aguas subterráneas y el método de interpolación espacio-temporal conocido como Bayesian Maximum Entropy (BME) para el análisis de calidad del aire. Esta tesis contribuye a demostrar las capacidades de las redes neuronales en el desarrollo de nuevas metodologías y modelos que explícitamente permiten evaluar las dimensiones temporales y espaciales de riesgos acumulativos

    Optimization Strategies for Spatio-temporal Groundwater Dynamics Monitoring

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    Räumlich kontinuierliche Daten sind in der Hydrogeologie für die wissenschaftliche Forschung, die Risikobewertung und wasserwirtschaftliche Entscheidungsprozesse von wesentlicher Bedeutung. Die meisten dieser Informationen werden allerdings nur punktuell durch Messungen an Grundwassermessstellen erhoben und anschließend regionalisiert. Die Vorhersagegenauigkeit dieser räumlich interpolierten Daten, die in der Regel die Grundlage für weitere Berechnungen und Entscheidungen bilden, ist stark abhängig von der Konzipierung des Grundwassermessnetzes, d.h. von der räumlichen Verteilung und Dichte der Grundwassermessstellen, der Beprobungshäufigkeit, dem Interpolationsverfahren sowie dem Wechselspiel zwischen diesen Faktoren. Daraus ergibt sich ein erhebliches Optimierungspotenzial hinsichtlich des Grundwassermessnetzes und der Regionalisierungstechnik. Geeignetes Grundwassermessnetze sind daher wichtige Instrumente für die nachhaltige Bewirtschaftung und für den Schutz der Grundwasserressourcen. Sie bieten Zugangspunkte für die Überwachung von Grundwasserständen und -proben und ermöglichen so einen Einblick in die Grundwasserverhältnisse. Die Kombination aus hohen Erschließungskosten und einer verhältnismäßig geringen räumlichen Repräsentativität der Brunnen aufgrund der hydrogeologischen Heterogenität machen die Konzeption eines geeigneten Überwachungsnetzes zu einer großen Herausforderung. Diese Arbeit beschäftigt sich mit Techniken zum verbesserten Verständnis der Grundwasserdynamik durch (i) räumliche und (ii) räumliche-zeitliche Optimierung von Grundwasserstands Messnetzen und (iii) verbesserter räumlichere Vorhersage der an diesen Überwachungsbrunnen gewonnenen Daten unter Verwendung von Interpolationstechniken. Zu diesem Zweck wurde im ersten Teil dieser Arbeit eine umfassende Untersuchung der meistgenutzten deterministischen und geostatistischen, uni- und multivariaten Interpolationstechniken für die Erstellung von Grundwassergleichenplänen in einem Untersuchungsgebiet durchgeführt, das durch eine komplexe Interaktion zwischen Karst, einem alluvialen Grundwasserleiter und gering durchlässigen Schichten der alpinen Molasse gekennzeichnet ist. Die untersuchten Methoden wurden durch globale Kreuzvalidierung und öko-hydrogeologische Informationen an Karstquellen, Feuchtgebieten, Oberflächengewässern und Profilschnitten bewertet. Der mögliche Effekt der Methodenwahl auf die weitere Berechnung wurde durch Abschätzung der Austauschprozesse zwischen Karst- und Alluvialgrundwasserleiter auf Basis der geschätzten Potentialunterschiede durchgeführt. Die Ergebnisse zeigen, dass die Verfahrenswahl, insbesondere bei unzureichendem Überwachungskonzept, drastische Auswirkungen auf die nachfolgenden Berechnungen haben kann. Die Studie hat ergeben, dass geostatistische oder Kriging Interpolationsmethoden den deterministischen Interpolationsmethoden überlegen sind. Bei dürftiger Grundwasserdatenlage kann das Co-Kriging mit räumlich kreuzkorrelierten Sekundärvariablen (z. B. Höhenlage, Flusspegel), die häufiger erfasst werden, wertvolle Informationen über die Primärvariable bereitstellen und so die Varianz des Schätzfehlers verringern. Im zweiten Teil dieser Arbeit wurden räumliche Monitoringkonzepte mit unterschiedlichen Messdichten an numerisch modellierter Grundwasseroberflächen mit verschiedenen Skalen und Dynamiken untersucht. Ziel war es, Einblicke in geeignete Monitoringansatze für eine verlässliche räumliche Abschätzung des Grundwasserspiegels zu gewinnen und eine Überwachungsdichte abzuleiten, bei der ein angemessenes Information/Kosten-Verhältnis erreicht wird. Die Interpolationsergebnisse wurden mit globaler Kreuzvalidierung und dem tatsächlichen räumlichen Fehler evaluiert, der anhand der numerischen Modellflächen als A-priori-Referenz errechnet wurde. Überwachungsnetze mit einer regelmäßigen Gitteranordnung boten zwar genaueste räumliche Vorhersagen für das betrachtete Dichtespektrum, sind jedoch aufgrund ihrer Nachteile, wie der mangelnden Erweiterungsfähigkeit, tendenziell ungeeignet. Eine vergleichbar gute Leistung wurde erzielt, wenn der maximale Vorhersage-Standardfehler als Auswahlkriterium für zusätzliche Brunnen für bestehende Messnetze verwendet wurde. In dieser Studie wurde außerdem eine neuartige Optimierungsstrategie für Überwachungsnetze angewandt, die auf mathematischen Quasi-Zufallsfolgen basiert. Der Ansatz liefert ebenfalls überzeugende Ergebnisse und bietet mehrere Vorteile. Er bedarf keinerlei Vorkenntnisse über den Grundwasserleiter durch vorhandene Brunnen und es werden unabhängig von den Ausbaustufen reproduzierbare räumliche Anordnungen erzielt. Im dritten Teil wurde ein datengesteuerter Sparse-Sensing-Algorithmus-Ansatz zur Auswahl von spärlichen Sensorpositionen unter Nutzung von Techniken zur Dimensionsreduktion untersucht und für die zeitliche und räumliche Optimierung eines bestehenden Grundwasserstandsmessnetzes im Oberrheingraben adaptiert. Die Optimierung erfolgt mit einem greedy search (QR)-Algorithmus, der die Überwachungsbrunnen nach ihrem Informationsgehalt über Aquifer-Dynamik selektiert und einordnet. Als Eingangsdaten wurden langjährige Ganglinien-Aufzeichnungen verwendet, um repräsentative Messstellen oder Messstellen mit redundantem oder niedrigem Informationsgehalt zu bestimmen. Des Weiteren wurde eine Optimierung auf der Grundlage regionalisierter, wöchentlicher Grundwassergleichenkarten durchgeführt, um mögliche geeignete Standorte für zusätzliche Messstellen zu identifizieren. Die Suche wurde durch eine räumliche Kostenfunktion gelenkt, bei der weniger geeignete Standorte abgewertet wurden. Der untersuchte Ansatz hat sich als potenziell wertvolles Instrument für die Optimierung der Brunnenanzahl und deren Standorte, für die Reduzierung und den Ausbau des Netzes aber auch für eine kombinierte Nutzung beider Möglichkeiten erwiesen

    An integrated DRASTIC model using frequency ratio and two new hybrid methods for groundwater vulnerability assessment

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    Groundwater management can be effectively implemented by mapping groundwater contamination. Intense agricultural activities and land overexploitation have resulted in groundwater contamination, which is becoming a critical issue, specifically in areas where fertilizers are extensively used on large plantations. The goal of this study was to develop an integrated DRASTIC model with a frequency ratio (FR) as a novel approach. Two new hybrid methods namely single-parameter sensitivity analysis (SPSA) and an analytical hierarchy process (AHP) are also implemented for adjusting feature weights to local settings. The FR is used for DRASTIC model rates, whereas both SPSA and AHP are used for DRASTIC weights. The FR-DRASTIC, FR-SPSA and FR-AHP methods are developed; nitrate samples from the same month in different years are used for analysis and correlation (May 2010 and May 2012). The first nitrate samples are interpolated using the Kriging approach. The Kerman plain is used as an example, which is located in south-eastern part of Iran. Additionally, the new methods are employed in the study area to compare with each other and the original DRASTIC model. The validation results exhibited that using FR approach improved the correlation between vulnerability index and nitrate concentrations compared with original DRASTIC vulnerability correlation which was 0.37. The results indicated that the new hybrid methods exhibited higher correlation 0.75 in the FR-DRASTIC model. Correlations of the FR-SPSA and FR-AHP approaches were 0.77 and 0.80. Hence, the new hybrid methods are more effective and provide reasonably good results. Furthermore, quantitative measures of vulnerability offer an excellent opportunity to effectively prevent as well as reduce contamination

    Assessing nitrate contamination risks in groundwater : a machine learning approach

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    Groundwater is one of the primary sources for the daily water requirements of the masses, but it is subjected to contamination due to the pollutants, such as nitrate, percolating through the soil with water. Especially in built-up areas, groundwater vulnerability and contamination are of major concern, and require appropriate consideration. The present study develops a novel framework for assessing groundwater nitrate contamination risk for the area along the Karakoram Highway, which is a part of the China Pakistan Economic Corridor (CPEC) route in northern Pakistan. A groundwater vulnerability map was prepared using the DRASTIC model. The nitrate concentration data from a previous study were used to formulate the nitrate contamination map. Three machine learning (ML) models, i.e., Support Vector Machine (SVM), Multivariate Discriminant Analysis (MDA), and Boosted Regression Trees (BRT), were used to analyze the probability of groundwater contamination incidence. Furthermore, groundwater contamination probability maps were obtained utilizing the ensemble modeling approach. The models were calibrated and validated through calibration trials, using the area under the receiver operating characteristic curve method (AUC), where a minimum AUC threshold value of 80% was achieved. Results indicated the accuracy of the models to be in the range of 0.82–0.87. The final groundwater contamination risk map highlights that 34% of the area is moderately vulnerable to groundwater contamination, and 13% of the area is exposed to high groundwater contamination risk. The findings of this study can facilitate decision-making regarding the location of future built-up areas properly in order to mitigate the nitrate contamination that can further reduce the associated health risks. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. **Please note that there are multiple authors for this article therefore only the name of the first 5 including Federation University Australia affiliate “Muhammad Imran” is provided in this record*

    Modeling of soil weathering on hillslopes : coping with nonlinearity and coupled processes using a data-driven approach

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    Orientadores: Carlos Roberto de Souza Filho, Michael James FriedelTese (doutorado) - Universidade Estadual de Campinas, Instituto de GeociênciasResumo: Esta tese de doutorado tem como objetivo aprofundar o conhecimento sobre as relações das propriedades físico-quimicas do solo com a morfometria do relevo, buscando quantificar essas relações para a construção de modelos conceituais e preditivos. Mapas auto-organizáveis e modelos de sistemas de informação geográfica foram utilizados para investigar as relações não lineares associadas ao intemperismo químico e físico, fatores associados a fenômenos hidrológicos e à evolução dos solos. Três estudos de caso são apresentados: o intemperismo químico de solo no estado do Paraná (22 variáveis e 304 amostras), o transporte físico de sedimentos em Poços de Caldas (9 variáveis e 29 amostras), e hidroquímica de aqüíferos na Formação Serra Geral no Estado do Paraná (27 variáveis e 976 amostras). O método combinando simulação estocástica e mineração de dados permitiu explorar as relações entre relevo, granulometria e geoquímica dos solos. Regiões mais elevadas e com morfometria convexa apresentaram alta denudação de elementos móveis (e.g., Ca) e baixa de elementos pouco móveis (e.g., Al). O mesmo padrão foi observado para granulometria de solos, ou seja, alta proporção de areia em áreas altas e convexas da bacia e altos teores de argila, com baixa condutividade hidráulica, em regiões convexas próximas aos canais de drenagem. O comportamento espacial da hidroquímica das águas do aqüífero Serra Geral apontou áreas de potencial conectividade entre aqüíferos, áreas de recarga recente e de alto tempo de residência. Foram construídos modelos preditivos não tendenciosos das propriedades do solo em subsuperfície partindo da premissa de que o intemperismo e a morfometria se relacionam através de um processo duplamente dependente, onde a denudação física e química atua no delineamento do relevo e a morfometria do terreno é um fator que caracteriza as condições físico-químicas do soloAbstract: This Doctoral thesis aims to explore the relationship between soil physical-chemical properties and relief morphometry, and quantifying these relationships to build conceptual and predictive models. Self-organizing maps and Geographic Information Systems modeling are here used to investigate nonlinear correlations associated with chemical and physical denudation; which are factors connected with hydrological phenomena and soil evolution. Three study cases are presented: soil chemical weathering within the limits of the Parana State, southern Brazil (22 variables and 304 samples), physical transport of sediments in the alkaline intrusive complex of Poços de Caldas, southeastern Brazil (9 variables and 29 samples), and hydrochemistry of Serra Geral aquifers also in the Parana State (27 variables and 976 samples). The method combining stochastic simulation and data mining allows exploring the relationships between topography, soil texture and soil geochemistry. In the Parana State, higher regions and areas with convex morphometry shows, respectively, higher and lower denudation rates of mobile (e.g., Ca) and less mobile (e.g., Al) elements. The same pattern is observed for soil particle size. In this case, high proportion of sand is found in highlands and convex areas inside the basin, and high clay content, with low hydraulic conductivity, occurs in convex regions, near drainage channels. The spatial behavior of the Serra Geral aquifer?s hydrochemistry pointed out to areas with potential connectivity with the Guarani aquifer system, recent recharge areas, and long-standing waters. Predictive, unbiased models are built for soil properties on the premise that weathering and morphology are related through a two-way dependent process, where the physical and chemical denudation delineates the elevations of the land surface, and terrain morphometry is a factor that characterizes the physical-chemical conditions of the soilDoutoradoGeologia e Recursos NaturaisDoutor em Ciência

    INTEGRATED AQUIFER VULNERABILITY ASSESSMENT OF NITRATE CONTAMINATION IN CENTRAL INDIANA

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    Groundwater is not easily contaminated, but it is difficult to restore once contaminated. Therefore, groundwater management is important to prevent pollutants from reaching groundwater. A common step in developing groundwater management plans is assessment of aquifer risk using computational models. Groundwater modeling with a geographic information system (GIS) for efficient groundwater management can provide maps of regions where groundwater is contaminated or may be vulnerable and also can help select the optimal number of groundwater monitoring locations

    Continental hydrosystem modelling: the concept of nested stream–aquifer interfaces

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    International audienceCoupled hydrological-hydrogeological models, emphasising the importance of the stream–aquifer interface, are more and more used in hydrological sciences for pluri-disciplinary studies aiming at investigating environmental is-sues. Based on an extensive literature review, stream–aquifer interfaces are described at five different scales: local [10 cm– ∼ 10 m], intermediate [∼ 10 m–∼ 1 km], watershed [10 km 2 – ∼ 1000 km 2 ], regional [10 000 km 2 –∼ 1 M km 2 ] and conti-nental scales [> 10 M km 2 ]. This led us to develop the con-cept of nested stream–aquifer interfaces, which extends the well-known vision of nested groundwater pathways towards the surface, where the mixing of low frequency processes and high frequency processes coupled with the complexity of geomorphological features and heterogeneities creates hy-drological spiralling. This conceptual framework allows the identification of a hierarchical order of the multi-scale con-trol factors of stream–aquifer hydrological exchanges, from the larger scale to the finer scale. The hyporheic corridor, which couples the river to its 3-D hyporheic zone, is then identified as the key component for scaling hydrological pro-cesses occurring at the interface. The identification of the hy-porheic corridor as the support of the hydrological processes scaling is an important step for the development of regional studies, which is one of the main concerns for water practi-tioners and resources managers. In a second part, the modelling of the stream–aquifer in-terface at various scales is investigated with the help of the conductance model. Although the usage of the temperature as a tracer of the flow is a robust method for the assess-ment of stream–aquifer exchanges at the local scale, there is a crucial need to develop innovative methodologies for as-sessing stream–aquifer exchanges at the regional scale. After formulating the conductance model at the regional and inter-mediate scales, we address this challenging issue with the de-velopment of an iterative modelling methodology, which en-sures the consistency of stream–aquifer exchanges between the intermediate and regional scales. Finally, practical recommendations are provided for the study of the interface using the innovative methodology MIM (Measurements–Interpolation–Modelling), which is graphi-cally developed, scaling in space the three pools of methods needed to fully understand stream–aquifer interfaces at vari-ous scales. In the MIM space, stream–aquifer interfaces that can be studied by a given approach are localised. The ef-ficiency of the method is demonstrated with two examples. The first one proposes an upscaling framework, structured around river reaches of ∼ 10–100 m, from the local to the wa-tershed scale. The second example highlights the usefulness of space borne data to improve the assessment of stream– aquifer exchanges at the regional and continental scales. We conclude that further developments in modelling and field measurements have to be undertaken at the regional scale to enable a proper modelling of stream–aquifer exchanges from the local to the continental scale

    A regional-scale conceptual and numerical groundwater flow model in fluvio-glacial sediments for the Milan Metropolitan area (Northern Italy)

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    Study region: The Milan metropolitan area lies on one of the most important aquifer in Italy, heavily exploited for public and industrial water supply. The area, covering 3135 km2 in the Po Plain (Northern Italy) with a continental climate, is bounded by the Po, the Adda and the Ticino rivers and by the prealpine foothills. Regional hydrology is characterised by a network of natural and man-made elements, and lowland springs. The sedimentary sequence, from bottom to top, is formed by meandering river plain deposits, the distal fringe of the glacial outwash plains and proximal braid-plain deposits. Study focus: This study proposes a general approach for aquifer geometry reconstruction and hydrodynamic parametrization of hydrofacies in fluvio-glacial deposits, and their implementation into a 3D regional groundwater flow model. This approach is based on sedimentologically-defined lithofacies/hydrofacies and their correlation in space to obtain nearly homogeneous subunits starting from available data (i.e. 8628 borehole logs, grain size distributions, well tests) and sedimentological knowledge. New hydrological insights for the region: The calibrated 3D FEM groundwater model allows quantifying the main components of the hydrogeological budget at the regional scale, and the fluxes among the different hydro-stratigraphic units. A sensitivity analysis of groundwater levels to the main recharge components suggests importance of anthropogenic disturbances with respect to natural recharge, and that land-use change may impact water resources more than climate change
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