Dissertations / Theses on the topic 'Parana Basin, Numerical modeling'

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Na avaliação da maturidade de horizontes geradores e da história térmica de uma bacia com registro de atividade magmática é preciso considerar o efeito térmico imposto pela intrusão de corpos ígneos, como diques e soleiras. Dessa maneira, foi realizada a análise numérica transiente, pelo método de diferenças finitas, do fluxo térmico por condução provocado pela intrusão das soleiras básicas cretáceas nos horizontes geradores do Membro Assistência, Formação Irati, Bacia do Paraná. Esta análise, por sua vez, viabilizou a modelagem do parâmetro de reflectância da vitrinita nos estratos de folhelhos adjacentes às soleiras. Para tanto, foram utilizados os dados de seção de três poços, os quais registram espessuras de soleiras de até 4 m, e um poço com uma soleira de 27 m de espessura. Os poços localizam-se na porção sudeste da bacia. Na simulação numérica, foi considerado o processo de solidificação do magma ou de cristalização das suas fases minerais. A modelagem de reflectância da vitrinita baseou-se em um modelo pré-concebido da história térmica da Formação Irati, sendo os resultados desta simulação de maturidade do querogênio obtidos através do uso do programa EASY%Ro. Considerando-se os erros embutidos no modelo numérico e na discretização da história térmica dos estratos estudados, foram obtidos valores modelados de reflectância da vitrinita similares aos valores medidos nos poços pelo método tradicional. Somente no caso da seção com a soleira de 27 m de espessura houve uma grande diferença entre estes valores. Contudo, o alto coeficiente de correlação (0,95) entre estes possibilita a correção do efeito da espessura da soleira em análises futuras. Assim, a análise numérica simulou o halo térmico da soleira, caracterizado, segundo os dados de modelagem de refletância da vitrinita, por uma faixa acima e abaixo da soleira com espessura equivalente à espessura da soleira encaixada nos estratos geradores da Formação Irati. Essa metodologia de avaliação propicia um estudo preditivo das condições de maturidade de horizontes geradores em bacias ou áreas com magmatismo intrusivo, nas quais as análises do parâmetro de reflectância da vitrinita sejam ausentes ou escassas.
To evaluate the thermal maturity and thermal history of source rocks in basins with magmatic activity it is important to consider the thermal effects imposed by igneous intrusions, such as sills and dykes. This work uses the finite difference method for such evaluation, with the transient numerical analysis of heat conduction from Cretaceous diabase sills intruded into the source rocks of the Assistência Member, Irati Formation, Paraná Basin. This analysis has permitted modeling vitrinite reflectance of the shale strata adjacent to the sills. The data of four wells are used from the southeastern portion of the basin, with diabase thicknesses, respectively, of 1m, 2 m, 4 m and 27 m. The numerical simulation includes the process of magma solidification or mineral phase crystallization. The vitrinite reflectance modeling followed a pre-established thermal history of the Irati Formation, using the EASY%Ro program to simulate kerogen maturity levels. Considering the errors built into the numerical model and the thermal history discretisation of studied strata, the acquired values of modeled vitrinite reflectance closely resembled well data analyzed by the traditional method. Major discrepancies were observed in the case of the well containing a sill 27 m thick, but even in this case the high correlation coefficient (0,95) between the measured and calculated values is expected to permit correction of the sill thickness effect in future studies. The numerical analysis correctly simulated the thermal halo induced by sill emplacement, enabling vitrinite reflectance modeling to characterize it as a zone extending both above and below the sill with thicknesses similar to that of the sills. This evaluation methodology contributes to a predictive study of the maturity conditions of source rocks within basins or areas with intrusive magmatism where analysis of the vitrinite reflectance parameter are sporadic or absent.

Increasing dependence on groundwater in the Wakal River basin, India, jeopardizes water supply sustainability. A numerical groundwater model was developed to better understand the aquifer system and to evaluate its potential in terms of quantity and replenishment. Potential artificial recharge areas were delineated using landscape and hydrogeologic parameters, Geographic Information System (GIS), and remote sensing. Groundwater models are powerful tools for recharge estimation when transmissivity is known. Proper recharge must be applied to reproduce field-measured heads. The model showed that groundwater levels could decline significantly if there are two drought years in every four years that result in reduced recharge, and groundwater withdrawal is increased by 15%. The effect of such drought is currently uncertain however, because runoff from the basin is unknown. Remote sensing and GIS revealed areas with slopes less than 5%, forest cover, and Normalized Difference Vegetative Index greater than 0.5 that are suitable recharge sites.

Seawater-fresh groundwater natural equilibrium conditions in the aquifers of the Selç
uk sub-basin may be disturbed by the discharge occurred during the past 30 years in order to supply water for irrigation and domestic purpose usage. Two dimensional density dependent cross sectional saturated flow and solute transport simulations were carried out to determine whether seawater intrusion has occurred in the Selç
uk sub-basin due to the imposed discharge or the determined salt-water in the western section of the aquifers represents natural interface equilibrium conditions. The numerical simulation model was calibrated using field measurements. The results of the simulations suggest that the seawater intrusion has occurred in the study area since the pumping activity increased in the region. Five scenarios were simulated for future predictions: (1) Present recharge and discharge conditions are maintained, (2) Discharge increases at a rate of the municipality need as a result of increasing population, (3) Discharge decreases by 12% from the present value, (4) Discharge decreases by 25% from the present value, and (5) No discharge occurs or recharge amount equals to the present discharge amount condition supplied to the aquifer. These scenario results suggest that seawater intrusion in the Selç
uk sub-basin would progress in the following years unless proper management measures are taken into consideration. KEYWORDS: seawater intrusion, density dependent groundwater flow, solute transport, contamination, Selç
uk sub-basin.

Une prédiction de la réponse sismique des structures de génie civil (telles que les centrales nucléaires ou les barrages), doit faire face à plusieurs difficultés majeures compte tenu de la complexité du problème traité. Pour cela, la simulation de la source, la propagation des ondes sismique et les effets de site, ont été étudiés par différentes approches dernièrement. Récemment, des méthodes combinées avec des ordinateurs massivement parallèles se sont avérées très efficaces pour modéliser la propagation des ondes sismiques depuis la source jusqu’au site, dans des environnements géologiques tridimensionnels complexes. Cependant, la précision reste limitée en raison du caractère multi-échelle du problème et des grandes incertitudes sur les données à introduire dans le modèle (i.e. la caractérisation géométrique et cinématique de la source sismique, le modèle géologique et numérique du chemin de propagation). Pour cela, l’utilisation d'un modèle numérique régional capable de simuler le phénomène sismique de la source au site permettrait de mieux comprendre et de classer l'origine de ces incertitudes.Ce travail vise à étudier numériquement l'effet de la géologie locale et régionale sur la réponse sismique d’un bassin et plus particulièrement le site d’Argostoli situé sur l'île de Céphalonie (Grèce). Dans un premier temps, le code numérique utilisé dans ce travail (SEM3D) est vérifié à l'aide de trois cas canoniques. Les résultats obtenus montrent un bon accord avec les solutions de référence. Dans les cas d’un modèle numérique avec diverses échelles ou avec des géologies complexes, l’un des points clefs est la conformité du maillage numérique avec les interfaces géologiques, ce qui se traduit par l’augmentation du coût numérique. Grâce aux caractéristiques de la méthode numérique utilisée, pour contourner cette difficulté, une approche possible est l’utilisation des maillages “non-conformes” ou “not-honouring”. Une étude paramétrique sur la faisabilité de cette approche est ainsi réalisée afin de mettre en évidence l'influence de certains paramètres numériques sur les résultats obtenus.Par la suite, des études paramétriques de plusieurs scénarii sismiques sur le site d'Argostoli ont été réalisées. Concernant le chargement sismique, deux types de sources ont été étudiés : des sources ponctuelles et des failles étendues. L’étude avec les sources ponctuelles révèle un phénomène d'amplification et de piégeage des ondes dans le bassin, conduisant à un signal complexe et allongé, avec une énergie importante par rapport à une étude avec une géologie simplifiée. Pour le second type de source, la faille modélisée est proche de la surface. Cela permet d'étudier l’effets du bassin et du champ-proche sur la réponse sismique du site. En effet, le mouvement du sol à proximité d'une faille peut être différent du mouvement du sol observé loin de la source sismique. D’après les résultats obtenus, l'effet du bassin est plus marqué mais avec une amplification plus forte et des fréquences de résonance différentes. De plus, l'effet du champ-proche a été mis en évidence, marqué par de fortes impulsions de vitesse à certains endroits du bassin. L’ordre de grandeur des spectres de réponses obtenues est comparable à ceux obtenus lors des séismes de magnitude semblable qui ont eu lieu en 2014 au même endroit.Dans la dernière partie, une étude paramétrique sur des aspects numériques liées à la précision du calcul a été réalisée. Cette étude a permis d’augmenter la résolution fréquentielle de 7 Hz à 10 Hz avec des caractéristiques mécaniques de sols mous avec la même taille de domaine. Ces simulations ouvrent plus de questions sur l’interdépendance de la finesse de la résolution des données physiques et des maillages pour les calculs numériques. En conclusion, cette thèse correspond à une première étape dans la caractérisation numérique de la réponse sismique du bassin d’Argostoli et les effets dus au bassin, au type de source et à leurs interactions
A prediction of the seismic response of civil engineering structures that requires a high level of safety (i.e. nuclear power plants or dams) faces several major difficulties given the complexity of the problem being treated. To this end, the source simulation, seismic wave propagation and site effects have been studied by different approaches over the last two decades. Recently, numerical methods, such as the spectral element, combined with massively parallel computers have proved a good efficiency in modelling the seismic wave propagation from source to site in complex three-dimensional geological environments. However, the accuracy of these predictions remains limited due to the multi-scale nature of the problem and the large uncertainties in the data to be introduced into the model (i.e. the geometric and kinematic characterization of the seismic source, the detailed geological and numerical model of the source-to-site propagation path). Therefore, the use of a regional numerical model able to simulate the seismic phenomenon from source to site would allow a better analysis and classification of the origin of the associated uncertainties.This work aims to study numerically the effect of local and regional geology on the seismic response of a basin and precisely the Argostoli site located on the island of Kefalonia (Greece). Firstly, the numerical code used in this work (SEM3D) is verified using three canonical cases. The simulated results showed a good agreement with the reference solutions. In the cases of a numerical model with different scales or with complex geologies, one of the important difficulties is the conformity of the numerical meshes with the geological interfaces, that will result an increase in the numerical cost. Because of the characteristics of the used numerical method, one possible approach was to use the “non-conforming” or “not-honoring” meshes to overcome this difficulty. A parametric study on the applicability of this approach was then carried out in order to highlight the influence of some numerical parameters on the obtained results.Thereafter, parametric studies on several seismic scenarios in the Argostoli site were conducted. Concerning seismic loading, two types of source have been studied: point sources and extended faults. The study with point sources clearly revealed a phenomenon of amplification and trapping of waves in the basin, leading to a complex and elongated signal, with significant energy compared to a study with a simplified geology. For the second type of source, the modeled fault is close to the surface. It allows to study, in addition to the influence of the basin, the effect of the near-field on the seismic response of the site. Indeed, near-fault ground motion can be significantly different from ground motion observed far from the seismic source. Based on the results obtained, the basin effect is even more pronounced but with higher amplification and different resonance frequencies. In addition, the near-field effect has been highlighted, marked by strong velocity pulses at some locations in the basin. The order of magnitude of the obtained response spectra is comparable to the ones obtained during the earthquake sequence of similar magnitude that took place in 2014.In the last part, a parametric study (allowed by the development of computing power) on the numerical aspects related to the computational accuracy was carried out. With this study, it is possible to increase the frequency resolution from 7 Hz to 10 Hz with soft soil mechanical characteristics while keeping the same domain size. These simulations open even more questions on the interdependence of the fineness of resolution of physical data and meshes for numerical simulations. In conclusion, this thesis corresponds to a first step in the numerical characterization of the seismic response of the Argostoli basin and the effects due to the basin, the type of source and their interactions

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
A avaliação da recarga subterrânea e de sua variação temporal e espacial, em bacias hidrográficas, é essencial para estudos de sustentabilidade de recursos hídricos e requer, na maior parte das vezes, o uso de um modelo numérico de fluxo 3D. Geralmente, dados como mapas geológicos e pedológicos estão disponíveis, a localização e geometria das principais feições estruturais podem ser identificadas a partir de imagens de satélite, em ambiente SIG, e dados de hidrologia superficial e de elevação de terreno são fáceis de conseguir. No entanto, para se utilizar um modelo numérico que forneça uma primeira avaliação da sustentabilidade de uma explotação, é necessário alimentá-lo com dados de propriedades hidráulicas consistentes com a faixa de valores representativos dos tipos de rocha que compõe a bacia. Uma revisão de dados hidrogeológicos de uma série de localidades mostra que, enquanto as propriedades hidráulicas das rochas fraturadas apresentam uma grande variação em seus valores, quando analisadas de forma indiscriminada, ao serem agrupadas por tipo litológico, apresentam uma faixa de variação mais restrita (i.e. granito fraturado vs. gabro fraturado). Há um grande volume de dados relativos a projetos de disposição de lixo radioativo, mineração e engenharia civil, em diversos sítios ao redor do mundo, em que foram feitas investigações detalhadas do meio fraturado. Dados de um determinado maciço fraturado podem ser usados em outro, não investigado, como uma primeira aproximação, desde que possuam o mesmo tipo litológico e pertençam a ambientes tectônicos semelhantes. Este tratamento foi utilizado para modelar a vazão sustentável de uma pequena bacia de drenagem no Noroeste Fluminense. Dados relativos às estruturas dominantes e aos sistemas de fraturas foram extraídos de imagens de satélite, fotos aéreas e de afloramentos, e tratados em ambiente SIG. O modelo de fluxo subterrâneo foi construído com dados de elevação do terreno, mapas geológicos, registros hidrológicos históricos bem como mapas pedológicos e de uso da terra. O programa FEFLOW (Diersch, 1998) foi usado para simular a distribuição espacial e temporal da recarga subterrânea na bacia e diferentes cenários de explotação de água subterrânea. O modelo mostrouse capaz de fornecer uma primeira aproximação das reservas subterrâneas da bacia e de avaliar a relação entre o fluxo subterrâneo e dos cursos d’água superficiais, em condições naturais e nos cenários de explotação, sendo assim uma ferramenta útil para análises de sustentabilidade de exploração destes recursos.
The estimation of groundwater recharge and its spatial and temporal variability in a drainage basin is essential for sustainability assessments and requires, in most cases, the use of an appropriate 3D numerical flow and transport model. For most drainage basins, the bedrock and overburden geology maps exist, the location and geometry of major structural features can be identified using available GIS databases, and surface water and terrain elevation data at an appropriate scale are readily available. In order to use 3D models to provide an initial assessment of the sustainability of the groundwater resource extraction of a specific drainage basin, the 3D model has to be populated with hydraulic properties that are consistent with the range of values that are representative of the rock types that underlie the drainage basin. A review of hydrogeological data from a number of sites shows that while there is a wide range in the hydraulic properties of fractured rocks in general, the range for individual rock types is more constrained, (i.e. fractured granite versus fractured gabbro). There is a great amount of hydrogeological data from fractured rock masses that have been investigated in detail as part of nuclear waste, mining and civil engineering projects around the world. Data from a specific site can be used as a first approach in another one, not investigated, once they have the same geologic characteristics and tectonic environment. This approach was used to model the sustainable groundwater yield of a small drainage basin in Southeast Brazil. Data on major structures and fracture systems were extracted from satellite images, aerial photos and outcrop expositions using GIS environment. The groundwater flow model was constructed using terrain elevation data, geology maps, hydrological records, as well as soil type and land use maps. FEFLOW (Diersch, 1988) was used to simulate the spatial and temporal distribution of groundwater recharge in the basin, using different pumping scenarios. The model was capable to yield a good estimation of groundwater resources in the watershed, as a first approach, and to assess groundwater and surface water relations in natural conditions and in stress scenarios being a useful tool for sustainability analysis of groundwater exploitation.

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k Menderes River Basin located in western Turkey has been facing continuous groundwater level decreases for the past 30 years. In dry periods, irrigation demand is completely met by pumping from groundwater system, which reduces water levels significantly. This provides enough storage to be recharged in wet seasons when streams are running. However, increased runoff in wet season are not utilized neither for irrigation nor for recharge and lost to the Aegean Sea without being infiltrated. Hence, surface artificial recharge methods can be useful to collect excess water in recharge basins, thus allowing infiltration to increase groundwater storage in wet seasons to be later utilized in dry seasons. A 2-D groundwater model is set up by using SEEP/W software. The material functions and parameters used in the model for saturated/ unsaturated conditions are taken from previous studies. Calibration was done to check the accuracy of input data and to control the validity of model. The amount of excess water that will be collected in recharge basins was estimated from flood frequency analysis. Concerning different probabilities, different scenarios were simulated to observe the increase in groundwater levels. Simulation results suggest that significant increase in groundwater storage could be achieved by applying artificial recharge methods. In addition to recharge basins, to reinforce the effect of artificial recharge, simulations were repeated with the addition of an underground dam at downstream side of the basin. Simulation results indicate that the increase in groundwater storage is not sufficient to warrant construction of the underground dam.

Snowmelt runoff in the mountainous eastern part of Turkey is of great importance as it constitutes 60-70% in volume of the total yearly runoff during spring and early summer months. Therefore, forecasting the amount and timing of snowmelt runoff especially in the Euphrates Basin, where large dams are located, is an important task in order to use the water resources of the country in an optimum manner. The HBV model, being one of the well-known conceptual hydrological models used more than 45 countries over the world, is applied for the first time in Turkey to a small basin of 242 km2 on the headwaters of Euphrates River for 2002-2004 water years. The input data are provided from the automatic snow-meteorological stations installed at various locations and altitudes in Upper Euphrates Basin operating in real-time. Since ground based observations can only represent a small part of the region of interest, spatially and temporally distributed snow cover data are acquired through the use of MODIS optical satellite. Automatic model parameter estimation methods, GML and SCE_UA, are utilized to calibrate the HBV model parameters with a multi-objective criteria using runoff as well as snow covered area to ensure the internal validity of the model and to generate a Pareto front. Model simulations show that the choice of study years and timing of satellite images affect the results and further suggest that more study catchments and years should be included to achieve more comprehensible conclusions. In the second part of the study, the calibrated HBV model is applied to forecast runoff with a 1-day lead time using gridded input data from numerical weather prediction models of ECMWF and MM5 for the 2004 snowmelt period. Promising results indicate the possible operational use of runoff forecasting using numerical weather prediction models in order to prevent or at least take precautions before flooding ahead of time.

The complexity of the interplay between tectonics and sedimentation increases when salt tectonics is involved because of the ductility of salt and its ability to flow. Discrimination between extensional tectonics and salt-related processes is problematic; especially where salt-related rift basins were inverted as occurred in the Central High Atlas in Morocco. The aim of the present work was to analyse and understand the dynamics of the Central High Atlas diapiric basin during the Early Jurassic rift and subsequent post-rift periods using a multidisciplinary workflow integrating fieldwork, analogue models and subsidence and thermal numerical modelling. Two regions were examined to assess the effects of salt tectonics in the evolution of the basin; the Djebel Bou Dahar platform-basin system represented the fault domain of the rift basin where diapiric activity was not described and the Tazoult-Amezraï area and Imilchil diapiric province corresponding to the unstable domain of the basin characterised by the presence of diapiric salt ridges and minibasins. Results from analogue models highlighted the intrinsic interrelation between extension, diapirism and sedimentation that characterised the diapiric domain of the Central High Atlas. Longitudinal and transverse sedimentary progradations and their timing had a strong impact in the migration of ductile layers, in the growth of diapirs and in their lateral structural variations; triggering well-developed passive diapirs in the proximal domains and incipient reactive diapirs or poorly developed roller-like and passive diapirs in the distal domains of the sediment source. Analogue models including post-diapiric compression fairly reproduced the observed structure in the studied areas. Modelling with 6% and 10% of shortening, slightly lower than the Atlas one, produced the progressive close-up of the two flanks of salt walls and their final welding as well as the steepening of their outward flanks, with dips increasing from 8o-17o prior to compression to 30o-50o after compression. Subsidence curves varied depending on the analysed localities of the rift basin. Djebel Bou Dahar showed long-term and low-rate tectonic and total subsidence (0.06 and 0.08 mm yr-1, respectively). The roughly parallel evolution of both total and tectonic subsidence curves indicates the main extensional tectonic influence on subsidence pattern, as corroborated by the syndepositional activity of the outcropping Sinemurian-Pliensbachian normal faults. In the unstable domain, Amezraï minibasin centre showed tectonic and total subsidence rates between 0.06-0.32 and 0.19-0.98 mm yr-1, rates one order of magnitude higher than in the Djebel Bou Dahar. These subsidence rates were up to two-fold their equivalent rates in the Tazoult salt wall (0.01-0.27 and 0.09-0.74 mm yr-1). In the Imilchil diapiric province lateral shifts of the main subsiding depocenters were recorded during Toarcian to Callovian times (tectonic and total subsidence rates up to 0.23 and 0.90 mm yr-1). The subsidence of the unstable domain was caused by the combination of normal fault extension and salt withdrawal from beneath the minibasins during rifting, being the salt-related subsidence predominant during the post-rift and masking the expected subsidence pattern for a rift-post rift transition. For the first time, 27 new vitrinite reflectance data were used to build the thermal evolution and associated geohistory of the Central High Atlas. Thermal models, with heat flows of 105 mW/m2 (from 189 to 140 Ma) followed by 60 mW/m2 and 70 mW/m2 (from 189 to 182.7 Ma) followed by 60 mW/m2, pointed to a post-Middle Jurassic evolution characterised by long-term and low-rate subsidence and an overburden between 1200-2400 m on the Tazoult-Amezraï area. The comparison of subsidence curves from this study with Saharan Atlas and Tunisian Atlas showed that peak of subsidence in these salt-related domains became younger to the east.
La discriminació entre processos associats a tectònica extensiva i a tectònica salina es problemàtica; especialment en conques diapíriques extensives invertides com és el cas del Alt Atles Central de Marroc (CHA). L’objectiu d’aquesta tesis és analitzar i entendre els processos que interaccionaren a la conca diapírica del CHA durant el rift Juràssic i el subseqüent període post rift, utilitzant una metodologia multidisciplinària que integra treball de camp, models analògics i models numèrics. S’han estudiat dos dominis de la conca: no diapiric i diapiric (diapirisme durant el Juràssic Inferior i Mitjà). Els models analògics mostren que progradacions longitudinals i transversals i el moment quan s’inicien tenen un gran impacte en la migració dels nivells dúctils, en el mode de creixement diapiric i les seves variacions laterals. Els models amb compressió post-diapírica mostren que dita compressió produeix la reducció progressiva de l’amplada de les estructures diapíriques fins al seu tancament complet, així com a un increment dels cabussaments dels flancs com s’ha observat a les zones d’estudi. Les corbes de subsidència varien segons el domini analitzat. El domini no diapiric es caracteritza per un període llarg de baixes taxes de subsidència tectònica i total (0.06 i 0.08 mma-1). El domini diapiric registra taxes de subsidència tectònica i total fins a un ordre de magnitud majors que en el domini no diapiric (0.23 i 0.90 mma-1) i una migració dels depocentres subsidents. La subsidència del domini diapiric s’interpreta, durant el rift Juràssic Inferior, com una combinació d’activitat de falles normals i migració salina, sent aquesta darrera la predominant durant la fase post-extensiva i emmascarant el patró de subsidència esperat en un estadi de transició rift-post rift. Per primera vegada, es presenta la geohistòria de la part central del CHA. Els models tèrmics emprats per a la seva construcció, avaluats amb 27 noves dades de reflectància de vitrinites de la zona d’estudi, suggereixen una evolució post-Juràssic Mitjà caracteritzada per un període llarg de baixa subsidència que hauria enterrat la regió entre 1200-2400 m, en comptes de una complexa historia que inclouria diversos esdeveniments d’exhumació com s’ha enregistrat en altres zones del Alt Atles Marroquí.

Este trabalho é parte integrante do Projeto de Caracterização Regional da bacia Sergipe-Alagoas, realizado em convênio entre a Petrobras e o Laboratório de Hidrodinâmica Costeira do Instituto Oceanográfico da Universidade de São Paulo, que visou caracterizar a circulação da bacia Sergipe-Alagoas em escala regional. Foram coletados dados meteo-oceanográficos no período entre 2012 e 2015. Foram analisados dados de três fundeios correntográficos, duas estações meteorológicas e vinte estações hidrográficas. Esta análise incluiu: análise por Funções Empí¬ricas Ortogonais, análise espectral, análise harmônica e correlação. Ainda, foram realizadas simulações numéricas, onde se considerou um oceano homogêneo, que contemplaram o vento, a maré e o aporte fluvial como forçantes do domí¬nio. Os resultados mostraram uma plataforma continental praticamente homogênea, onde há um forte ciclo sazonal para as correntes e para o vento, com menores intensidades durante o verão e o outono e maiores intensidades durante o inverno e a primavera. Quanto à hidrodinâmica, determinou-se que o modo barotrópico é dominante, seguido pelos 1º e 2º modos baroclí¬nicos, nesta ordem. Quanto às forçantes, constatou-se que a maré é a menos significativa para a circulação residual da região, onde a componente semidiurna M2 se destaca como mais energética. Ainda, detectou-se o predomí¬nio do vento sobre a circulação da PCSEAL durante o inverno e a primavera. Nas demais estações, supõe-se uma competição entre as descargas fluviais e a tensão de cisalhamento do vento sobre a circulação da PCSEAL.
This work is part of the project \"Caracterização Regional da bacia de Sergipe-Alagoas\" supported by PETROBRAS in association with the Coastal Hydrodynamic Laboratory (LHiCo) of the University of Sao Paulo. This project aimed to characterize the Sergipe-Alagoas basin circulation on a regional scale. Meteo and ocean datas were colected from 2012 to 2015, including three current meter moorings, two meteorological stations and twenty hidrographic stations. The analysis includes Empirical Ortogonal Functions, spectral, harmonic and correlations analysis. The Numerical simulations are also developed, employing a homogenous ocean with wind, tides and river discharges forcings. The results show a homogeneous continetal shelf with a significant seasonal cycle for the currents and winds, with minimum values in the summer and fall, and maximum values in the winter and spring. It is show from the Empirical Ortogonal Function analysis, that the barotropic mode is dominant over the Sergipe-Alagoas shelf circulation, followed by the first and second baroclinic modes, in this order. About the forcings, the wind stress drives the shelf circulation in winter and spring. The other seasons has a supposed dispute between river discharges and wind stress. The tide is dominated by the component M2 and it is the least significant for the residual circulation over the Sergipe-Alagoas shelf.

Fluctuations in temperature and precipitation amounts due to climate change influence recharge rate of groundwater. Any variations in the amount of precipitation recharge and artificial discharge directly affect groundwater level and so the salt water intrusion rate in the aquifers, which are in contact with sea water. The purpose of this study is to determine the overall historical precipitation recharge trend in Selç
uk sub-basin and to detect whether there is a decrease or increase in recharge amounts due to climate change since 1100 BC. Besides, it covers assessing the future position of the salt water-fresh groundwater interface as a result of possible fluctuations in climate and artificial discharge. For this purpose, numerical density dependent cross sectional groundwater flow with solute transport model was conducted using finite element approach. At first, current salt water-fresh water interface and artificial discharge related head changes in the aquifer were determined. Backward modeling was utilized to obtain concentration distribution in the year 1976 representing the last stage of the undisturbed period. Then, progradation of salt water-fresh water interface since 1100 BC to 1976 was modeled using calibrated parameters and current recharge value. As a result of sea-regression model simulations (1100 BC-1976) less degree of salt water intrusion than that of currently detected in the area was obtained. The result suggests that overall recharge amount in the last 3076 years must have been less than that of 1976. Moreover, future (2010-2099) position of the interface and head changes under the influence of both climate change and increasing water demand were determined. Future model simulations indicate that salt water-fresh water interface moves farther landward. However this movement is mostly due to increasing discharge amount rather than that of climatic changes.

This doctoral thesis provides the first comprehensive study on the physical processes controlling hydrodynamics and transport in Lake Garda. The investigation is carried out in parallel on three different levels: data collection and analysis, three-dimensional numerical modeling and theoretical study. On the first level, data are collected by building up a network of research institutes and local administrations in the lake area. New data are acquired through traditional field campaigns (CTD, thermistor chains, satellite imagery), while a citizen-science approach, based on local knowledge harvesting, is successfully tested to gather qualitative data on surface circulation. On the second level, a three-dimensional modeling chain is set up, by coupling one-way a mesoscale atmospheric model to a hydrodynamic model. Both models are validated on multiple temporal and spatial scales, allowing to identify the main interactions between the weather forcing and the hydrodynamic response of the lake. Circulations in Lake Garda are found to be very sensitive to the thermal stratification, to the spatial distribution of the wind forcing and to the Earth’s rotation. Surface cyclonic gyre patterns develop in the lake as a residual outcome of alternating wind forcing of local breezes and differential acceleration induced by Earth’s rotation, whereas unidirectional currents flow under a nearly uniform and constant wind. Both model and observations evidences show that, under weak thermal stratification, Ekman transport activates a secondary circulations in the northern part of the lake, driving surface water to the deep layers and possibly preconditioning the lake for subsequent buoyancy-driven deep mixing events. On the third level, the relevance of the Coriolis term in the equations of motion for relatively narrow closed basins is analytically addressed. The classical Ekman problem is solved by including the presence of lateral boundaries and a new analytical solution is formulated. The validity of the new solution is proved by numerical tests of idealized domains of different size, geographical location and turbulent regime, and on Lake Garda as a real test case. The meaningful length scales are discussed, and the significance of Rossby radious as a reference horizontal scale is disproved for steady-state circulations driven by wind and planetary rotation.

La dynamique des courants de turbidité est fortement contrôlée par la morphologie du fond marin. Les turbidites issues de ces courants constituent des réservoirs d’hydrocarbures très importants dans les bassins sédimentaires à travers le monde. L'objectif principal de ce travail est de comprendre comment le paleorelief a contrôlé la géométrie et l'architecture des réservoirs turbiditiques, en utilisant comme zone d'étude les réservoirs du Crétacé d'un champ pétrolier du bassin de Campos (offshore du Brésil), où la tectonique a été en partie dominée par l'halocinèse. La méthodologie utilisée dans cette thèse a couplé deux approches. La première a inclus à la fois la description des séquences sédimentaires, à partir de données de sismique-réflexion et de puits, et les restaurations structurales. Six horizons régionaux et quatre unités-réservoirs ont été identifiés et cartographiés afin de construire un modèle géologique multi-2D. Ces surfaces ont ensuite été aussi restaurées. Les résultats de cette étape suggèrent que les failles liées à l'halocinèse ont contraint la paléotopographie pour le dépôt des réservoirs plus anciens et que des structures tectoniques et un canyon ont formés les contraintes paléotopographiques pour la distribution des réservoirs plus jeunes. La seconde approche a été l'analyse du rôle des paramètres des écoulements en effectuant des simulations numériques du type stratigraphique (Dionisos) et des automates cellulaires (CATS). Une surface restaurée, considérée comme référence pour le dépôt des unités-réservoirs a été utilisée comme paléotopographie pour les simulations CATS. Le modèle numérique a été contraint par les données réservoirs. Cette utilisation inédite des simulations 3D avec des automates cellulaires dans une étude de cas réel concernant des dépôts marins anciens a produit des résultats réalistes par rapport aux exemples modernes connus. Elle a également fourni des résultats plus exploitables à l'échelle de réservoir que les modèles numériques de type "stratigraphique". Ce travail met en évidence l'importance des interactions tectonique-sédimentation et de la paléotopographie pour la distribution de réservoirs turbiditiques
The dynamic of gravity-driven turbidity currents is strongly influenced by the morphology of the seafloor. The resulting turbidites constitute important hydrocarbon reservoirs in sedimentary basins throughout the world. The main objective of the present work is thus to understand the way the paleorelief controls turbidite reservoir architectures, with application in a specific study area with Cretaceous reservoirs in Campos Basin (Brazilian offshore). The tectonics in this Basin was partly controlled by halokinesis. The first approach was describing the local Cretaceous sedimentary sequence architecture, from seismic and well data, and performing structural restorations. Six regional horizons and four reservoir-scale units were identified and mapped in order to build a multi-2D geological model. Structural restorations highlighted the structural evolution and allowed the related horizon palaeotopography to be obtained. The results of this work step suggest that the halokinesis-related listric faults regulated the distribution of the basal reservoirs. Moreover, at the top of the Albian carbonates, a canyon was identified, which, in association with the tectonic structures, forms the palaeotopographic constraints for the upper reservoir geometry. The second approach was analyzing the role of flow controlling parameters by performing stratigraphic (Dionisos) and cellular automata-based (CATS) numerical simulations. The latter provided a more appropriate reservoir scale-simulation process than Dionisos. A restored surface, considered as reference for the deposition of the reservoir units, was used as the palaeotopography for CATS simulations, having as constraints the reservoir data. This pioneer use of cellular automata simulations in a real subsurface case study produced coherent results when compared with the actual reservoir distribution. This work sheds light on the importance of tectonic-sedimentation interactions and of palaeotopography for the distribution of turbidite reservoirs

Le bassin profond du Bas-Congo est une marge passive affectée par une forte déformation salifère. Elle présente des sorties naturelles d'hydrocarbures lourds qui ont des impacts majeurs sociétaux, biologique, écologique et économique. L'objectif de ce travail est de comprendre les modes de fonctionnement de ces systèmes, depuis la mobilisation des hydrocarbures dans les sédiments, jusqu'à l'exutoire en fond de mer, puis en surface mer. Cette étude combine des analyses de données issues de l’imagerie spatiale, de l’océanographie, de la géochimie et de la géophysique marine afin d'obtenir à une vision intégrée multi-échelle des zones d’expulsion naturelles d'hydrocarbures dans le bassin profond du Bas-Congo. L'analyse de données issues de l'imagerie spatiale montre qu'une centaine de sites sont actifs dans la zone d'étude. Un volume de 4400 m3 d’hydrocarbures est naturellement émis par an. L'intégration des données de courantométrie permet de relier les nappes d'hydrocarbures visibles à la surface de la mer avec les structures fond de mer. Celles-ci correspondent à des chapelets de dépressions localisés sur le pourtour des diapirs de sel et à des regroupements de monticules composés d'asphaltes en périphérie. Dans les sédiments, les anomalies géophysiques caractéristiques correspondent à des cheminées verticales, délimitées par le bas par le réflecteur sismique associé à la base de stabilité des hydrates de gaz. La correspondance spatiale de ces différents critères a permis d'inventorier les sites potentiellement actifs sur les données géophysiques. Seulement 40% de ces sites sont associés à des nappes d'hydrocarbures récurrentes à la surface de la mer
The Lower Congo Basin is a passive margin, affected by strong salt tectonics. Natural escapes of heavy hydrocarbons observed in the area have major impacts on the society, ecology, biology, and the economy. The aim of this work is to understand the mechanisms of these systems, from the mobilisation in the sediments towards the seafloor outlets and subsequently towards the sea surface. This study combines data analysis from spatial imagery, oceanography, geochemistry and marine geophysics in order to get a multi-scale integrated vision of the natural seepage situation in the Lower Congo Basin. The analysis of spatial imagery data shows that in the study area, the hundred active seeps sites expel a hydrocarbons volume of 4400 m3 per year, following an intermittent mechanism with miscellaneous frequencies from one site to another. We connected visible hydrocarbon slicks at the sea surface with seabed structures by integrating current measurements across the water column. Seafloor structures correspond to clustered pockmarks of high seismic amplitude located at the rim of salt diapirs and to clusters of mounds composed of highly degraded oil outwards. In sediments, geophysical anomalies form vertical chimneys, delimited by the seismic reflector associated with the base of gas hydrates stability downwards. The spatial correspondence of geophysical criteria enabled to inventory the potentially active sites on the geophysical data. Only 40% of these sites are associated with recurring oil slicks at the sea surface

Les bassins d’infiltration font partie intégrante des techniques alternatives de gestion des eaux pluviales en milieu urbain. Néanmoins, la potentialité de transfert de polluants vers la nappe est accrue en cas d’écoulements préférentiels dans les sols sous-jacents. Une bonne compréhension du couplage entre processus d’écoulements préférentiels en zone vadose et mécanismes géochimiques est requise. Cette thèse s’inscrit dans le cadre du suivi d’un bassin d’infiltration depuis plusieurs dizaines d’années de fonctionnement. Le site d’étude est situé sur le dépôt fluvioglaciaire hétérogène couvrant une grande partie de la région lyonnaise. Des auscultations sur une fosse sous le bassin (section 13.5m*2.5m) ont mis en évidence une régionalisation particulière de la pollution dans le sol. Cette étude s’appuie sur une étude numérique visant à identifier l’origine de la régionalisation des polluants et à la relier aux écoulements préférentiels résultant des hétérogénéités lithologiques. En amont de l’étude numérique, les lithofaciès sont complètement caractérisés aux regards de leurs propriétés hydrodynamiques, hydrodispersives et géochimiques. La modélisation numérique permet de souligner l’établissement de cheminements préférentiels en lien avec le contraste de propriétés hydrodynamiques, notamment lorsque de faibles débits sont appliqués en surface. Le rôle de chaque lithofaciès et de l’architecture du dépôt (stratification et inclusions) est clairement identifié. Les répercussions de tels écoulements sur les transferts non réactifs sont ensuite investiguées en combinant l’influence des écoulements préférentiels et le fractionnement de l’eau en fractions mobile et immobile résultant de l’hétérogénéité intrinsèque au sein de chaque lithofaciès. Enfin, ces processus physiques sont couplés à la réactivité géochimique pour le cas d’un polluant modèle (le cuivre) en prenant en compte la réactivité différentielle des lithofaciès. Ces résultats permettent de générer un modèle conceptuel d’écoulements préférentiels et de transfert de masse en milieu fortement hétérogène
An infiltration basin is a stormwater best management practice (BMP) designed to infiltrate runoff volumes in urban areas. Nevertheless, preferential flow paths in the underlying soil may cause rapid migration of pollutants, thus contributing to groundwater contamination. Understanding the coupling between preferential flow processes in the vadose zone and geochemical mechanisms is then required. This thesis is a part of the follow-up of an infiltration basin for several decades of exploitation. The study site was settled over a highly heterogeneous glaciofluvial deposit covering much of the Lyon region. The investigation of an excavated section of the basin (13.5m long and 2.5m deep) pointed out a specific regionalization of pollution in the soil. This research is based on a numerical study to identify the origin of such a pollutant pattern and link this with preferential flow resulting from lithological heterogeneities. Different lithofacies were fully characterized regarding their hydraulic, hydrodispersive and geochemical properties. The numerical study proves that the high contrast in hydraulic properties triggers the establishment of preferential flow (capillary barriers and funneled flow). Preferential flow develops mainly for low initial water contents and low fluxes imposed at surface. The role of each lithofacies and architecture of deposit (stratification and inclusions) is clearly identified. The impact of such flows on non-reactive transfers is then investigated by combining the influence of preferential flow and pore water fractionation info into mobile and immobile fractions, resulting from the intrinsic heterogeneity within each lithofacies. Finally, these physical processes are coupled to the geochemical reactivity for a pollutant model (copper), taking into account the differential reactivity of lithofacies. These results generate a conceptual model of preferential flow and mass transfer in strongly heterogeneous media

博士
國立臺北科技大學
工程科技研究所
98
Overall dewatering along with ground treatment is widely utilized to reduce uplift failure and ingress of water during excavations for metro rapid transit (MRT) system. Thus a series of step-drawdown, single well pumping, multi-well pumping tests are performed to derive the hydraulic parameter estimates for dewatering analysis of excavation. However, well situations and geological formations such as occur in Taiwan are not ideal, and the five influences, 1) periodical fluctuation, 2) wellbore storage, 3) skin, 4) partial penetration well effect, and 5) leakage problem, may have some effect on drawdown from both the pumping well and nearby observation wells. Hence, the drawdown cannot be accommodated in theoretical well formulae. This study analyzes drawdown records derived from the pumping tests undertaken in a deep confined gravel formation at the two construction sites adjacent to the Tamshui River. The drawdowns with same amplitude are selected for removing the tidal effect from the drawdown curve by recognizing the dominant frequency of groundwater level. Wellbore storage of the pumping well vanishes at 8 min after the onset of the pumping tests, wherein the steady head drop resulting from skin remains. As the actual thickness of the pumped aquifer is unknown, all the wells installed are regarded as partial penetration wells. By shifting late-time drawdown asymptote parallelly to that induced by fully penetrating well, the storage coefficient can be derived more accurately. The calculated drawdown begins to deviate from the measured drawdown at some 30 min, implying that the leakage commences to have some effect on drawdown at 30 min and that the measured drawdown in 8−30 min can reasonably be adequate for the hydraulic parameter estimates. The estimated transmissivity and storage coefficient are of 3.50-8.03 m2/min and 0.00095-0.00160, respectively.

碩士
國立中正大學
地球與環境科學研究所
107
Environmental isotopes have been one of the most important tracers to identify the sources of groundwater recharge especially in mountain aquifers. However, the derivations based on the results of environmental isotopes is difficult to be verified and there were very rare cases trying to do it. In this study, solute transport numerical modeling, MT3DMS coupled with MODFLOW, to calculate the distribution of the proportions of different sources of groundwater recharge in Puli Basin under some presumed scenarios. The results can be used to verify derivations based on oxygen and hydrogen isotopes in the previous studies. Puli Basin is a basin in mountain area, which was filled with massive conglomerate for over 700 meters. There are three major rivers flowing through the basin. Accordingly, the conceptual model was constructed and the groundwater flow system was subsequently established. Under the groundwater flow system, five potential sources of recharge, Mei Creek, Nangang Creek, Shi Liu Dong Creek, precipitation and paleo pore water, were assumed to release different solute species, respectively; and, the simulated distribution of concentration of each species should be proportional to relative amount of each recharge source. Based on the concentration distributions of five species, the recharge contributions of five sources in the aquifer system can be subsequently estimated. The results demonstrate that, in the whole basin scale, Mei Creek and Nangang Creek recharge 55.5 % and 20.4 % of water, respectively and the others are relatively minor. However, paleo pore water is significant only in the deep aquifer, which occupies about 21.7% of basin volume. These derivations are significantly different from those resulting from environmental isotopes in the previous studies, which suggested that the Nangang Creek system is able to provide over 90% of water recharge. With the established model in this study, the groundwater resources can be efficiently protected and managed in the future.