L'application de la Directive Cadre sur l'Eau et l'obligation de surveillance de la qualité d'eau pour la consommation humaine et les activités récréatives ou industrielles, telles que la production d'eau potable, entraînent une forte demande pour des systèmes d'évaluation et de suivi de la qualité de l'eau. Le projet de recherche MIGR'HYCAR (http://www.migrhycar.com) a donc été mis en place pour répondre à un besoin opérationnel et à un défaut d'outils d'aide à la décision adaptés face aux déversements d'hydrocarbures en eaux continentales (rivières, lacs et estuaires) qui représente plus de 50% des déversements accidentels en France. Au cours du projet de recherche MIGR'HYCAR, un modèle mathématique de dérive de nappe d'hydrocarbures, composé d'un modèle lagrangien couplé à un modèle eulérien, a été développé dans la plate-forme hydro-informatique TELEMAC (http://www.opentelemac.org). Le modèle lagrangien décrit le mouvement de la nappe en surface en considérant celle-ci comme un ensemble de particules. Ainsi le modèle développé est capable de modéliser les principaux phénomènes agissant sur une nappe d'hydrocarbures une fois celle-ci déversée : convection, diffusion, échouage, re-largage, étalement, évaporation, dissolution et volatilisation. Bien que le phénomène de dissolution ne concerne qu'un très faible volume d'hydrocarbures, ce processus peut avoir des conséquences importantes du point de vue de la toxicité. Afin de suivre l'évolution du pétrole dissous, un modèle eulérien de suivi de traceurs a été adopté. La quantité de traceur dépend directement de la masse dissoute des particules lagrangiennes. Cette approche permet le suivi des hydrocarbures dissous dans la colonne d'eau. Des cinétiques effectuées en laboratoire ont pour but la calibration du modèle numérique. En complément de cas tests issus de la littérature et de cas réels, des résultats expérimentaux issus d'expérimentations effectuées en canal d'essai doivent permettre de vérifier et valider la qualité des simulations numériques sur des situations où les conditions ne sont que partiellement contrôlées / The application of the European Water Framework Directive on water quality for human consumption and industrial activities creates a need for water quality assessment and monitoring systems. The MIGR'HYCAR research project (http://www.migrhycar.com) was initiated to provide decisional tools for risks connected to oil spills in continental waters (rivers, lakes and estuaries), which represent more than 50% of accidental spills in France. Within the framework of this project, a new numerical oil spill model has been developed, as part of the Telemac hydro-informatics system (see: (http://www.opentelemac.org), by combining Lagrangian and Eulerian methods. The Lagrangian model describes the transport of an oil spill near the free surface. The oil spill model enables to simulate the main processes driving oil plumes: advection, diffusion, oil beaching, oil re-floating, evaporation, dissolution, spreading and volatilization. Though generally considered as a minor process, dissolution is important from the point of view of toxicity. To model dissolved oil in water, an Eulerian advection-diffusion model is used. The fraction of dissolved oil is represented by a passive tracer. This approach is able to follow dissolved hydrocarbons in the water column. Laboratory experiments were conducted to characterise the numerous kinetics of the processes listed above. In addition, meso-scale dynamic experiments in artificial channels and test cases derived from the literature are used to validate the numerical model

L’application de la Directive Cadre sur l’Eau et l’obligation de surveillance de la qualité de l'eau pour la consommation humaine et les activités industrielles entraînent une forte demande pour des systèmes d’évaluation et de suivi de la qualité de l’eau. Le projet de recherche MIGR'HYCAR (http://www.migrhycar.com) a donc été mis en place pour répondre à un besoin opérationnel et à un défaut d'outils d'aide à la décision adaptés face aux déversements d'hydrocarbures en eaux continentales (rivières, lacs et estuaires) qui représentent plus de 50% des déversements accidentels en France. Ce travail de thèse s'inscrit dans le cadre de ce projet et a pour but l’étude du comportement des nappes d'hydrocarbures en milieu contrôlé pour les eaux continentales. A cet effet, il propose une approche expérimentale à l’échelle laboratoire pour étudier les phénomènes agissant sur une nappe d'hydrocarbures déversée : dissolution, étalement, évaporation et volatilisation. Les données expérimentales réunis ont permis de constituer une base de données de référence, qui servira de support aux outils de modélisation mathématique de dérive de nappe d'hydrocarbures développés dans le cadre de ce projet. / The application of the European Water Framework Directive on water quality for human consumption and industrial activities creates a need for water quality assessment and monitoring systems. The MIGR'HYCAR research project (http://www.migrhycar.com) was initiated to provide decisional tools for risks connected to oil spills in continental waters (rivers, lakes and estuaries), which represent more than 50% of accidental spills in France. This work joins within the framework of this project and aims at the study of the behavior of hydrocarbons in a controlled environment for continental waters. For that purpose, the work proposes an experimental approach at laboratory scale to study the phenomena acting in oil spill: dissolution, spreading, evaporation and volatilization. The experimental data allowed establishing a reference database, which will serve as support in tools of oil spill modeling within the framework of this project.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / The contamination of surface water bodies due to antropic action has made water ever more scarce. Knowledge of the water quality is essential to determine instruments for it's management . Monitoring water quality in huge areas requires a high number of saimples for water quality control. This fact, allied to the high costs of water analysis, limits the evaluation that can be made of continental waters. Even though in later years geoprocessing and remote sensing techniques have been developed with important results in water quality studies, these techniques have yet to be applied in the study of aquatic systems in semiarid regions. Therefore, it was attempted to develop a methodology based on the spectral characteristics of water as a support method for the evaluation of water quality in semiarid regions. Water samples were collected in seven points from 2008 to 2010 (every two months) and in 20 points from 2011 and 2012 (every three months) . The campaigns for radiometric data acquisition occurred in 2011 and 2012, alongside the water sampling. The determinant factors and water similarity were identified by the multivariable analysis. Data from orbital and insitu remote sensing correlated with limnologic data were used. The determinant indicators for water quality in the Oros were defined mainly by the following factors: the geologic components of the soil; sediment transport by surface flow and organic pollution. The Cluster Analysis formed three distinct groups. The water similarity was defined by natural conditions and by the land use around the reservoir and along the basin. The models developed for limnologic variables, suspended inorganic solids, turbidity, transparency and electric conductivity, showed themselves to be trustworthy, indicating that these variables can be quantified remotely through remote sensing data. The models developed for the clorophile - a fitted well, indicating that this variable can be quantified accurately through in situand orbital remote sensing data. The general three banded model presented a better efficiency to that of the two band model. According to the developed model and the image use of the MERIS sensor, the Oros waters, as far as trophic state is concerned, presented 61.15% of it's water bater classified as eutrophic for the month of February, 2010. For the MERIS image of August 2011, 95.77% of it's waters were classified as eutrophic. Therefore, through remote sensing data it is possible to elaborate a water resources management at a lower cost, generating a usefull information for decision making by managers, vital for the implementation of public policies at county, regional, state and federal levels. / Com a contaminaÃÃo de corpos hÃdricos pela aÃÃo antrÃpica, a disponibilidade de Ãgua torna-se cada vez menor. O conhecimento da qualidade das Ãguas à essencial à proposiÃÃo de instrumentos de gestÃo das mesmas. O monitoramento em Ãreas extensas requer um elevado nÃmero de amostras para o controle da qualidade da Ãgua; este fato, aliado aos altos custos das anÃlises, limita a avaliaÃÃo do processo de degradaÃÃo das Ãguas interiores. Apesar do desenvolvimento, nos Ãltimos anos, das tÃcnicas de geoprocessamento e sensoriamento remoto, com a obtenÃÃo de informaÃÃes relevantes em estudo de qualidade de Ãguas, elas nÃo tÃm sido exploradas em estudos de sistemas aquÃticos de regiÃes semiÃridas. Com isso, objetivou-se desenvolver uma metodologia baseada nas propriedades espectrais da Ãgua como suporte a avaliaÃÃo de sua qualidade em ambientes semiÃridos. As amostras de Ãgua foram coletadas em sete pontos de 2008 a 2010 (bimestralmente) e em 20 pontos de 2011 a 2012 (trimestralmente). As campanhas para aquisiÃÃo de dados radiomÃtricos ocorreram em 2011 e 2012, concomitantes Ãs coletas das amostras de Ãgua. Os fatores determinantes e a similaridade das Ãguas foram identificados pelo emprego da anÃlise multivariada. Foram usados dados de sensoriamento remoto orbital e in situ, correlacionando com os dados limnolÃgicos. Os indicadores determinantes da qualidade das Ãguas do OrÃs sÃo definidos principalmente pelos seguintes fatores: processo natural de intemperismo dos componentes geolÃgicos do solo; carreamentos dos sÃlidos suspensos atravÃs do escoamento superficial das Ãguas e poluiÃÃo orgÃnica. A anÃlise de agrupamento formou trÃs grupos distintos. A similaridade das Ãguas foi definida pelas condiÃÃes naturais e pelas atividades antrÃpicas exercidas nas proximidades do reservatÃrio e ao longo da bacia. Os modelos desenvolvidos para as variÃveis limnolÃgicas, sÃlidos inorgÃnicos suspensos, turbidez, transparÃncia e condutividade elÃtrica, mostraram-se confiÃveis, indicando que essas variÃveis podem ser quantificadas remotamente a partir dos dados de sensoriamento remoto de campo. Os modelos desenvolvidos para a variÃvel clorofila-a sÃo confiÃveis, indicando que esta variÃvel pode ser quantificada remotamente a partir dos dados de sensoriamento remoto de campo e orbital com elevado grau de confiabilidade. O modelo geral de trÃs bandas apresentou desempenho superior ao modelo de duas bandas. De acordo com o modelo desenvolvido e com uso de imagens do sensor MERIS, as Ãguas do reservatÃrio OrÃs, quanto ao estado trÃfico, apresentaram 61,15% da sua bacia hidrÃulica classificadas como eutrÃfica, para o mÃs de fevereiro de 2010. Para a imagem MERIS de agosto de 2011, 95,77% das Ãguas foram classificadas como eutrÃficas. Portanto, com o uso do sensoriamento remoto à possÃvel elaborar um gerenciamento dos recursos hÃdricos de menor custo, gerando informaÃÃes Ãteis à tomada de decisÃes pelos gestores, vital para a implantaÃÃo de polÃticas pÃblicas em Ãmbito municipal, regional, estadual e federal.