[ES] Actualmente, el 54% de la población mundial vive en ciudades y se espera que en 2050 este porcentaje aumente al 68% (UNDESA, 2019). Una parte importante de esta población urbana se concentra en megaciudades, definidas como áreas urba-nas con más de 10 millones de habitantes. En América Latina, las principales megaciudades son Sao Paulo y Ciudad de México, con más de 20 millones de habitantes en cada una. Buenos Aires, Río de Janeiro, Lima y Bogotá son mega-ciudades aún en desarrollo (Cepal, 2013). La presente tesis doctoral tiene como objetivo identificar y analizar los impactos que la dinámica de crecimiento urbano de una megaciudad induce sobre el com-portamiento de las componentes del ciclo hidrológico. La investigación desarro-llada incorpora el efecto del cambio climático de forma conjunta con el efecto del cambio de uso de suelo urbano. Para ello, se ha planteado una metodología de agregación de parámetros hidrológicos en superficies urbanas que se ha aplicado a la megaciudad de Bogotá, utilizando el modelo hidrológico TETIS y el modelo de cambios de uso de suelo LCM, bajo los escenarios oficiales de cambio climático vigentes en Colombia. Los resultados obtenidos muestran que el análisis conjunto de cambio de uso de suelo y cambio climático proporciona herramientas valiosas para comprender el comportamiento hidrológico de la cuenca en la que se sitúan las megaciudades y predecir su evolución futura. En el caso de la megaciudad de Bogotá se ha obser-vado que el mayor efecto en las componentes del ciclo hidrológico se produce por el cambio de usos de suelo, el cual se ve incrementado por las acciones inducidas por el cambio climático. La utilización de modelos numéricos que consideren todos estos aspectos es de especial relevancia a la hora de definir los planes, políti-cas y programas de desarrollo en entornos densamente urbanizados. / [CA] Actualment, el 54% de la població mundial viu a ciutats i s'espera que el 2050 aquest percentatge augmenti al 68% (UNDESA, 2019). Una part important d'a-questa població urbana es concentra en megaciutats, definides com a àrees urba-nes amb més de 10 milions d'habitants. A Amèrica Llatina, les principals mega-ciutats són Sao Paulo i Ciutat de Mèxic, amb més de 20 milions d'habitants a cadascuna. Buenos Aires, Rio de Janeiro, Lima i Bogotá són megaciutats encara en desenvolupament (Cepal, 2013). Aquesta tesi doctoral té com a objectiu identificar i analitzar els impactes que la dinàmica de creixement urbà d'una megaciutat indueix sobre el comportament dels components del cicle hidrològic. La investigació desenvolupada incorpora l'efecte del canvi climàtic de forma conjunta amb l'efecte del canvi d'ús de sòl urbà. Per això, s'ha plantejat una metodologia d'agregació de paràmetres hidrolò-gics en superfícies urbanes que s'ha aplicat a la megaciutat de Bogotà, utilitzant el model hidrològic TETIS i el model de canvis d'ús de sòl LCM, sota els escenaris oficials de canvi climàtic vigents a Colòmbia. Els resultats obtinguts mostren que l'anàlisi conjunta de canvi d'ús de sòl i canvi climàtic proporciona eines valuoses per comprendre el comportament hidrològic de la conca on se situen les megaciutats i predir-ne l'evolució futura. En el cas de la megaciutat de Bogotà s'ha observat que l'efecte més gran en les components del cicle hidrològic es produeix pel canvi d'usos de sòl, el qual es veu incrementat per les accions induïdes pel canvi climàtic. La utilització de models numèrics que considerin tots aquests aspectes és especialment rellevant a l'hora de definir els plans, polítiques i programes de desenvolupament en entorns densament urbanit-zats / [EN] Currently 54% of the world population lives in cities and it is expected that by 2050 this percentage will increase to 68% (UNDESA, 2019). An important part of this urban population is concentrated in megacities, defined as urban areas with more than 10 million inhabitants. In Latin America, the main megacities are Sao Paulo and Mexico City, with more than 20 million inhabitants. Buenos Aires, Rio de Janeiro, Lima and Bogotá are megacities still in development (Cepal, 2013). This doctoral thesis aims to identify and analyse the impacts that the dynamics of urban growth of a megacity induce on the behaviour of of the hydrological cycle components. The research carried out incorporates the effect of climate change together with the effect of urban land use change. To do this, a methodology for aggregating hydrological parameters in urban areas has been proposed. This methodology has been applied to the megacity of Bogotá, using the TETIS hydro-logical model and the LCM land use change model, under the official climate change scenarios in force in Colombia. Results obtained show that the joint analysis of land use change and climate change provides valuable tools to understand the hydrological behaviour of the basin in which the megacities are located and predict their future evolution. In the case of the megacity of Bogotá, it has been observed that the greatest effect on the components of the hydrological cycle is produced by the land use change, which is increased by the actions induced by climate change. The use of numeri-cal models that consider all these aspects is of special relevance when defining development plans, policies and programs in densely urbanized environments. / Romero Hernández, CP. (2022). Análisis del impacto del crecimiento de las megaciudades sobre el ciclo hidrológico bajo escenarios de cambio climático. Aplicación a la cuenca del río Bogotá (Colombia) [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/191025

This study addresses flood risk assessment in the Catalpa Creek watershed, located in northeast Mississippi, USA. Employing the Hydrological Modeling System (HEC-HMS) and the River Analysis System (HEC-RAS), integrated models were developed and calibrated, to predict flood behavior within the watershed. The study conducted flood frequency analyses for return periods ranging from 2 to 100 years and generated flood inundation maps, pinpointing flood-prone areas. Mitigation measures for flood risk management were recommended. The results underscore the effectiveness of the integrated modeling approach for simulating and understanding the complex dynamics of flood events. The research identified critical flood-prone zones, emphasizing the importance of proactive flood risk management. The calibrated hydrological model serves as a valuable tool for stormwater management, water resource planning, and watershed assessment. The study provides insights into flood risk in the Catalpa Creek watershed, offering valuable guidance to regional decision-makers. This study lays the foundation for future investigations in floodplain encroachment, sediment transport, stream restoration, and flood inundation hazard mapping.

Considering the potential for natural wetlands to store and retain water in the landscape,restored and constructed wetlands are increasingly implemented as Nature‐BasedSolutions (NBS) to mitigate downstream flooding. However, there is a frequent lack ofknowledge of the performance of NBS, and particularly wetlands, and how to best selectperformance indicators to measure their effectiveness. The aim of this study was to assessthe flood regulation services of multiple constructed wetlands at catchment scale. TheSWAT+ model was used to assess the impacts of 35 constructed wetlands in the 193 km2Råån catchment in southwest Sweden. The assessment was based on a paired simulationscenario, with and without wetlands, and performance was evaluated based on impacts onthe downstream river hydrograph (peak flow rate, time-to-peak, recession curve shape,daily streamflow average) as well as event-based (daily average streamflow for differentprecipitation ranges), descriptive (average wetland storage capacity), consequential(overbank flooding) and social (social acceptance) indicators. The results implied that theflow regulating capability of the modeled wetlands was directly related to their outflowmechanisms. The wetlands had an average storage capacity of 0.38 m3 per m2 area butbecause the wetlands seemed to frequently exceed their maximum storage capacity duringhigh flow events, and the excess water was immediately spilled downstream, the wetlandsprovided limited flood regulation services. There were no visible impacts on thehydrograph-related indicators and the daily streamflow average was reduced by anegligible 0.02%. Furthermore, there were no significant differences in wetlandperformance between small and heavy rainfall events and the model output showed nosigns of overbank flooding for either wetland scenario. In terms of social acceptance, recentwetland projects in Råån catchment seem to have been well-received by farmers andlandowners in the area. However, lack of wetland-specific data, such as volume and dailyinflow and outflow data, as well as other model uncertainties, motivated a low confidencegrade for the indicators. In fact, if indicator values are to be useful tools in the futureintegration of wetlands as nature-based solutions, in-situ monitoring data of wetland waterbalance components are required. To support future policies and decision-making, adaptedtools and further research are needed to assess the impact of NBS on upstream-downstream processes. / Naturliga våtmarkers förmåga att hålla kvar och lagra vatten i landskapet gör attrestaurerade och anlagda våtmarker alltmer implementeras som naturbaserade lösningarför att mildra översvämningar i nedströms belägna områden. Det råder dock brist påkunskap om hur effektiva naturbaserade lösningar är och hur nyckelindikatorer bäst kanväljas för att mäta hur väl dessa system fungerar. Syftet med denna studie var att utvärderaanlagda våtmarkers förmåga att mildra översvämningar i ett avrinningsområde. SWAT+modellen användes för att bedöma påverkan av 35 anlagda våtmarker i Råånsavrinningsområde (193 km2) utanför Helsingborg. Bedömningen baserades på ettsimuleringspar, med och utan våtmarker, och effektiviteten utvärderades baserat påhydrografens egenskaper (flödestopp, stegringsfasen, recessionsfasen, daglig medel-vattenföring) samt med en nederbördsbaserad (daglig medelvattenföring för olikanederbördsintervall), beskrivande (genomsnittlig lagringskapacitet), konsekvensbaserad(översvämmad mark) och social (social acceptans) indikator. Resultatet antydde att denflödesreglerande förmågan hos de modellerade våtmarkerna var direkt kopplad till derasutflödesmekanismer. Våtmarkerna hade en genomsnittlig lagringskapacitet på 0.38 m3 perm2 yta men eftersom de ofta verkade överskrida sina maximala lagringskapaciteter underhögflöden, och överskottsvattnet omedelbart släpptes igenom nedströms, tillhandahöllvåtmarkerna en mycket begränsad flödesdämpande funktion. Det fanns inga synligaeffekter på de hydrografrelaterade indikatorerna och den dagliga medelvattenföringenminskade med försumbara 0.02%. Dessutom sågs inga signifikanta skillnader mellan småoch kraftiga nederbördshändelser och modellen visade inga tecken på översvämmad markför något av våtmarksscenarierna. Vad gäller social acceptans tycks de senastevåtmarksprojekten i Rååns avrinningsområde ha tagits emot väl av lantbrukare ochmarkägare i området. Bristen på våtmarksspecifika data, såsom volym och dagliga in- ochutflödesdata, samt andra modellosäkerheter medförde dock ett lågt förtroende förindikatorerna. Om indikatorvärden ska vara användbara verktyg i den framtida integ-reringen av våtmarker krävs uppmätta data över våtmarkernas vattenbalanskomponenter.För att stödja framtida beslutsfattande behövs även anpassade verktyg och ytterligareforskning för att bedöma påverkan av naturbaserade lösningar på uppströms-nedströmsprocesser.

Alors que certains mécanismes pourtant jugés cruciaux pour la transformation de la pluie en débit restent peu ou mal compris, le concept de connectivité hydrologique a récemment été proposé pour expliquer pourquoi certains processus sont déclenchés de manière épisodique en fonction des caractéristiques des événements de pluie et de la teneur en eau des sols avant l’événement. L’adoption de ce nouveau concept en hydrologie reste cependant difficile puisqu’il n’y a pas de consensus sur la définition de la connectivité, sa mesure, son intégration dans les modèles hydrologiques et son comportement lors des transferts d’échelles spatiales et temporelles. Le but de ce travail doctoral est donc de préciser la définition, la mesure, l’agrégation et la prédiction des processus liés à la connectivité hydrologique en s’attardant aux questions suivantes : 1) Quel cadre méthodologique adopter pour une étude sur la connectivité hydrologique ?, 2) Comment évaluer le degré de connectivité hydrologique des bassins versants à partir de données de terrain ?, et 3) Dans quelle mesure nos connaissances sur la connectivité hydrologique doivent-elles conduire à la modification des postulats de modélisation hydrologique ? Trois approches d’étude sont différenciées, soit i) une approche de type « boite noire », basée uniquement sur l’exploitation des données de pluie et de débits sans examiner le fonctionnement interne du bassin versant ; ii) une approche de type « boite grise » reposant sur l’étude de données géochimiques ponctuelles illustrant la dynamique interne du bassin versant ; et iii) une approche de type « boite blanche » axée sur l’analyse de patrons spatiaux exhaustifs de la topographie de surface, la topographie de subsurface et l’humidité du sol. Ces trois approches sont ensuite validées expérimentalement dans le bassin versant de l’Hermine (Basses Laurentides, Québec). Quatre types de réponses hydrologiques sont distingués en fonction de leur magnitude et de leur synchronisme, sachant que leur présence relative dépend des conditions antécédentes. Les forts débits enregistrés à l’exutoire du bassin versant sont associés à une contribution accrue de certaines sources de ruissellement, ce qui témoigne d’un lien hydraulique accru et donc d’un fort degré de connectivité hydrologique entre les sources concernées et le cours d’eau. Les aires saturées couvrant des superficies supérieures à 0,85 ha sont jugées critiques pour la genèse de forts débits de crue. La preuve est aussi faite que les propriétés statistiques des patrons d’humidité du sol en milieu forestier tempéré humide sont nettement différentes de celles observées en milieu de prairie tempéré sec, d’où la nécessité d’utiliser des méthodes de calcul différentes pour dériver des métriques spatiales de connectivité dans les deux types de milieux. Enfin, la double existence de sources contributives « linéaires » et « non linéaires » est mise en évidence à l’Hermine. Ces résultats suggèrent la révision de concepts qui sous-tendent l’élaboration et l’exécution des modèles hydrologiques. L’originalité de cette thèse est le fait même de son sujet. En effet, les objectifs de recherche poursuivis sont conformes à la théorie hydrologique renouvelée qui prône l’arrêt des études de particularismes de petite échelle au profit de l’examen des propriétés émergentes des bassins versants telles que la connectivité hydrologique. La contribution majeure de cette thèse consiste ainsi en la proposition d’une définition unifiée de la connectivité, d’un cadre méthodologique, d’approches de mesure sur le terrain, d’outils techniques et de pistes de solution pour la modélisation des systèmes hydrologiques. / As core processes of the transformation of rainfall into runoff are not fully understood, the concept of hydrologic connectivity has been put forward to explain why some processes occur episodically, in a very discrete short-lived manner, as a response to intermittent atmospheric water input, storm characteristics and soil moisture storage. Even though emerging as a very powerful tool for explaining the growing numbers of nonlinear hydrologic behaviours documented around the world, the hydrologic connectivity concept raises major issues for future research in catchment hydrology in terms of its definition, its measure, its integration into hydrological models and its scaling in the space and the time domains. The aim of this doctoral work is to precise the definition, the measure, the scaling and the prediction of processes underlying hydrologic connectivity while focusing on the following research questions: (1) What methodological framework should guide investigations of hydrologic connectivity?, (2) How to assess hydrologic connectivity from field data?, and (3) To what extent can the ongoing knowledge acquisition on hydrologic connectivity be used to improve success with hydrological modeling? Three study approaches are discriminated, namely: (i) a black box approach that only relies on rainfall and runoff data without examining the internal catchment behaviour; (ii) a grey box approach based on punctual geochemical data illustrating the catchment internal state; and (iii) a white box approach involving exhaustive spatial patterns of surface and subsurface topographic variables and soil moisture. These three approaches are then tested against field data from the Hermine catchment (Lower Laurentians, Quebec). It is possible to classify the Hermine catchment hydrological responses with regards to their magnitude and their timing, the switching from one response type to another depending on antecedent conditions. It is revealed that high discharge values monitored at the catchment outlet are produced by increased contributions from specific runoff sources, thus hinting towards a reinforced hydraulic linkage and an enhanced degree of connectivity between runoff sources and the stream channel. It is established that saturated areas whose spatial extent exceeds 0.85 ha are critical for high runoff generation. Soil moisture spatial patterns in temperate humid forested catchments are shown to have statistical properties that are very different from those encountered in temperate rangelands; hence the necessity of using different spatial connectivity metrics in these contrasted environments. The co-existence of “linear” and “nonlinear” contributing sources is also illustrated in the Hermine catchment. These results suggest that some concepts should be revised for hydrological modeling purposes. The originality of the present thesis is mainly inherited from its prime focus. The pursued research objectives are in accordance with the future trend in catchment hydrology, especially as hydrologists are urged to move from site-specific experiments and results to more easily generalizable concepts that favour the study of emergent catchment properties such as connectivity. Thus, the major contribution of this thesis is the proposal of a unified definition of connectivity, a comprehensive methodological framework, technical tools and operational ideas for the better performance of hydrological models.

Esta pesquisa tem como finalidade discutir os impactos da variabilidade espacial e temporal de precipitações intensas nas vazões de cursos d\'água em bacias urbanizadas mediante a análise de dados históricos da pluviometria obtidos durante eventos críticos. A bacia hidrográfica do rio Tietê, em sua porção mais urbanizada, é a área objeto deste estudo. Após uma revisão sobre o tema na literatura específica, foram desenvolvidas chuvas de projeto com os padrões observados e com padrões teóricos, frequentemente utilizados na geração das tormentas sintéticas. O volume total precipitado foi associado ao período de retorno (TR) de 100 anos, a partir da análise estatística de chuvas pontuais e pela aplicação de fatores de redução de área (FRA) observados na área em estudo e de outras regiões, que vêm sendo utilizados em projetos de drenagem, sem qualquer estudo de validação; o intuito foi o de demonstrar a importância da definição de FRA específicos, a fim de evitar superdimensionamentos e otimizar as soluções. As chuvas de projeto foram aplicadas num modelo matemático de transformação chuva-vazão, devidamente calibrado, para obtenção das vazões de projeto resultantes no limite de jusante da bacia hidrográfica, frente aos diferentes padrões de solicitações hidrológicas. Para auxiliar a calibração do modelo estavam disponíveis dados dos postos telemétricos do Sistema de Alerta a Inundações de São Paulo - SAISP, curvas-chave e, para melhor representação dos eventos de precipitação observados, pode-se contar com as imagens do radar de Ponte Nova, em complementação às informações da rede de superfície. A comparação dos resultados obtidos no modelo hidrológico mostrou que os efeitos dos parâmetros variáveis (volume, distribuição espacial e temporal) são expressivos na composição dos hidrogramas de projeto. Dos testes realizados, identificaram-se as situações mais e menos críticas para a bacia, em termos de distribuição espacial e temporal e duração da chuva de projeto, além de estabelecer as diferenças no dimensionamento do sistema de drenagem pela adoção de FRA específico. Concluiu-se que, pela metodologia proposta, é possível chegar a vazões máximas de projeto apenas pela simulação de tormentas sintéticas, com diferenças de 10% a 20% das tormentas observadas maximizadas. Há, no entanto, a necessidade de realização de estudos adicionais, tanto para definição dos valores de FRA específicos, quanto de simulação de quantidade maior de padrões críticos observados, para a aplicação prática das indicações desse estudo com maior confiabilidade. / This research aims to discuss the impact of the spatial and temporal variability of heavy rainfall in the river flows in urbanized catchments by the historical rainfall data analysis obtained during critical events. The Tiete River catchment, in its most urbanized portion, is the subject of study of this research. After a review of the subject in the specific literature, design rainfall was developed along with the observed and theoretical patterns, often used in the generation of synthetic storms. The total volume precipitated was associated with the 100 years return period (RP), from the statistical analysis of point rainfall and for the application of areal reduction factors (ARF) observed in the study area and in other regions, which have been used in drainage projects without any validation study; the intention was to demonstrate the importance of the definition of specific ARF, in order to avoid oversizing and optimizing solutions. The design precipitation was applied on rainfall-runoff mathematical model, properly calibrated, so as to obtain the resulting design flow at the downstream boundary of the catchment, facing the different patterns of hydrological solicitations. In order to assist the calibration of the model, available data has been used from telemetric stations of the Sistema de Alerta a Inundações de São Paulo (São Paulo Flooding Alert System) - SAISP, discharge curves, and for better representation of the observed precipitation events, can be counted on the images taken from the Ponte Nova radar, as a complement to the information from the surface network. The comparison of the results of the hydrological model has shown that the effects of the variable parameters (volume, spatial and temporal distributions) are significant in the composition of the design hydrograph. Out of the performed tests, the most and the least critical situations were identified concerning the catchment in terms of both spatial and temporal distribution as well as the duration of the design storm. Also, the differences in the dimensions of the of the drainage system design were established by the adoption of specific ARF. Thus, it has been concluded, according to the proposed methodology, that it is possible to reach maximum design flow just by simulating synthetic storms, with differences ranging from 10% to 20% of the observed storms maximized. However, there is a need for additional studies, either to set up setting specific values of ARF or to simulate a larger quantity of critical patterns observed, in order to apply the indications of this study with higher reliability.

A comprehensive assessment of water security incorporates a range of water-related concepts, since water policy issues to specific technical aspects of hydrological conditions and their interactions with societal needs and ecosystem functioning. This doctoral thesis is organized into three chapters that address such range of water security-related topics, aiming to establish a conceptual baseline and propose deterministic and stochastic accounting frameworks for a river basin water security evaluation. Specific assumptions and research questions are defined in each chapter, and are related to the management of \'Cantareira water supply system\' (located in Southeastern Brazil), focusing on different scales and on its political and hydrological aspects as well. The first chapter acts as a conceptual baseline for water security assessment, by examining general aspects of the Brazilian water policy and water allocation system. This study contrasts Brazilian and American water management systems applied to water transfer projects, discussing experiences from the \'Cantareira system\' and Colorado river basin. A deterministic accounting framework is presented in the second chapter, which is based on management of blue and green water kinds (defined in accordance with hydrological processes and storage types), and demonstrates how a quantitative analysis of provisioning and use (abstraction and consumption) of both water kinds can be conducted. An agricultural basin (291 km²) within the Cantareira water supply system (located upstream of the Cachoeira reservoir) was used to illustrate this approach. The impact of blue and green water use on median water resources conditions is accounted by the scarcity indicator, while the vulnerability indicator considers the probability of low availability of water resources. In the third chapter quantifies and discusses the impacts of uncertainties on water security indicators (proposed in the chapter 2), based on a multi-model and resampling framework, that considers several uncertainty sources including those related to: i) observed streamflow data; ii) hydrological model structure; iii) residual analysis; iv) Environmental Flow Requirement methods; v) the definition of critical conditions for water provision; and vi) the critical demand imposed by human activities. Then, the uncertainty is propagated through different methodological arrangements applied to the same study basin of chapter 2. In brief, the first chapter indicates that both Brazilian and American water management system can potentially contribute to each other. In the second chapter, the Blue/Green water-based accounting framework reveal clear spatial and temporal patterns of water scarcity and vulnerability levels within the basin, thereby improving our understanding of how and where water-related threats to human and aquatic ecosystem security can arise (so called hot-spots). The third chapter provide a general method that can form basis for meaningful support to end-users facing water resource challenges by enabling them to incorporate a viable uncertainty analysis into a robust decision making process. Further investigation are proposed in each research step of this doctoral thesis. / A avaliação da segurança hídrica pode incorporar vários conceitos relacionados à água, desde aspectos da política de recursos hídricos até questões hidrológicas específicas e suas interações com a sociedade e ecossistemas. Esta tese de doutorado busca estabelecer uma base conceitual e propor esquemas metodológicos com base determinística e estocástica para avaliação da segurança hídrica de bacias hidrográficas. Objetivos específicos são definidos em cada capítulo e relacionam-se à gestão do \'Sistema Cantareira de abastecimento de água\' (localizado no Sudeste do Brasil), com foco em diferentes escalas, bem como aspectos políticos e hidrológicos. O primeiro capítulo é apresentado como baseline conceitual, examinando aspectos gerais da política de recursos hídricos e sistemas alocação de água. Este estudo compara sistemas de gestão aplicados a projetos de transposição de água inter/intra-bacias no Brasil e Estados Unidos, discutindo experiências do Sistema Cantareira e da bacia do rio Colorado. O segundo capítulo, por sua vez, propõe e analisa um esquema metodológico determinístico baseado na gestão das águas azul e verde (definidas de acordo com processos hidrológicos e unidades de armazenamento). Este estudo demonstra como uma análise quantitativa da provisão e utilização de ambos os tipos de água pode ser conduzida, propondo indicadores de escassez e vulnerabilidade hídrica. Esta abordagem foi aplicada em uma bacia agrícola (291 km²), localizada a montante do reservatório Cachoeira, que é integrante do Sistema Cantareira. O terceiro capítulo quantifica e analisa os impactos das incertezas sobre os indicadores de segurança hídrica propostos no capítulo 2, utilizando um esquema metodológico estocástico baseado em múltiplos modelos e reamostragem, que incorpora variadas fontes de incerteza, tais como: i) dados observados de vazão; ii) estrutura do modelo hidrológico; iii) análise de resíduos do modelo hidrológico; iv) estimativa de vazão ambiental; v) definição de condições críticas de provisão e vi) demanda hídrica. Em seguida, as incertezas são propagadas através de diferentes arranjos metodológicos aplicados na mesma bacia estudo do capítulo 2. Em conclusão, o primeiro capítulo sugere uma potencial troca de contribuições provenientes de ambos os sistemas de gestão brasileiro e americano. O segundo capítulo revela padrões espaciais e temporais dos resultados dos indicadores de escassez e vulnerabilidade, melhorando assim a compreensão de como e onde ameaças à segurança hídrica podem surgir. Por sua vez, a análise de incertezas desenvolvida no terceiro capítulo é capaz de gerar suporte a gestores de recursos hídricos e processo de tomada de decisões robustas. Recomendações específicas são geradas em cada capítulo da presente tese de doutorado.

Depuis le développement des mesures satellites de nombreuses missions spatiales sont dédiées au suivi de l'atmosphère et de la surface terrestre. Ces travaux de thèse s'inscrivent dans le cadre de la mission Megha-Tropiques dédiée au cycle de l'eau et de l'énergie en zone tropicale. L'objectif est d'évaluer le potentiel des estimations de précipitation par satellite pour des applications hydrologiques en zone tropicale. Les Tropiques réunissent les plus grands fleuves du globe, mais ne bénéficient pas de réseaux d'observation in-situ denses et continus permettant une gestion intégrée efficace de la ressource et des systèmes d'alertes. Les estimations des précipitations issues des systèmes d'observation satellite offrent une alternative pour ces bassins peu ou pas instrumentés et souvent exposés aux extrêmes climatiques. C'est le cas du fleuve Niger, qui a subi une grande variabilité climatique depuis les années 1950, mais aussi d'importants changements environnementaux et hydrologiques. Depuis les années 2000, le Niger moyen connaît une recrudescence des inondations pendant la période de crue Rouge (engendrée par ses affluents sahéliens pendant la mousson). A Niamey, des niveaux record de hauteur d'eau et de période d'inondation ont été enregistrés en 2003, 2010, 2012 et 2013, engendrant de nombreuses pertes humaines et matérielles. Ces travaux analysent l'influence du forçage pluviométrique sur les inondations liées à la crue Rouge à Niamey. Une gamme de produits pluviométriques (in situ et satellite) et la modélisation hydrologique (ISBA-TRIP) sont combinés pour étudier : (i) l'apport des produits satellite pour diagnostiquer la crue Rouge récente, (ii) l'impact des caractéristiques des produits et de leurs incertitudes sur les simulations et enfin (iii) l'évaluation du rôle des précipitations, face aux changements de conditions de surface, dans l'évolution de la crue Rouge à Niamey depuis les années 1950. L'étude a mis en évidence l'impact des caractéristiques des estimations des précipitations (cumul, intensité et distribution spatio-temporelle) sur la modélisation hydrologique et le potentiel des produits satellites pour le suivi des inondations. Les caractéristiques des précipitations se propageant dans la modélisation, la détection des inondations est plus efficace avec une approche relative à chaque produit plutôt qu'avec un seuil absolu. Ainsi des produits présentant des biais peuvent être envisagés pour la simulation hydrologique et la détection des inondations. Le nouveau produit TAPEER de la mission MT présente un fort potentiel hydrologique, en 2012 et pour la zone d'étude. D'autre part, l'étude de la propagation de l'erreur associée à ces précipitations a mis en évidence, la nécessité de déterminer la structure du champ d'erreur pour l'utilisation d'une telle information en hydrologie. Enfin la modélisation a été utilisée comme levier pour décomposer les sensibilités de la crue Rouge aux variations des précipitations et des conditions de surface. Pour simuler les changements hydrologiques entre les périodes 1953-1982 et 1983-2012, les changements d'occupation du sol et d'aire de drainage doivent être pris en compte. Puis les variations des précipitations peuvent expliquer les changements majeurs décennaux et annuels entre les années 1983 et 2012. / Since the development of satellite based remote sensing in the 1970s, many missions have been dedicated to monitoring the terrestrial atmosphere and surfaces. Some of these satellites are dedicated to the Tropics with specific orbits. Megha-Tropiques (MT) is devoted to the water and energy cycle in the tropical atmosphere and provides an enhanced sampling for rainfall estimation in the tropical region. This PhD work was initiated within MT hydro-meteorological activities, with the objective of assessing the hydrological potential of satellite rainfall products in the Tropics. The world most important rivers lay in tropical areas where the in situ observation networks are deficient. Alternative information is therefore needed for water resource management and alert systems. The present work focuses on the Niger River a basin which has undergone drastic climatic variations leading to disasters such as droughts and floods. Since 1950, the Niger has been through 3 main climatic periods: a wet period (1950-1960), a long and intense drought period (1970-1980) and since 1990 a partial recovery of the rainfall. These climatic variations and the anthropic pressure, have modified the hydrological behaviour of the basin. Since 2000, the middle Niger River has been hit by an increase of floods hazards during the so-called Red flood period. In Niamey city, the highest river levels and the longest flooded period were recorded in 2003, 2010, 2012 and 2013, leading to heavy casualties and property damage. This study combines hydrological modelling and a variety of rainfall estimation products (satellite and in-situ) to meet several objectives: (i) the simulation of the Niamey Red flood and the detection of floods (during the recent period 2000-2013) (ii) the study of the propagation of satellite rainfall errors in hydrological modelling (iii) the evaluation of the role of rainfall variability, and surface conditions, in the changes of the Red flood in Niamey since the 50s. The global model ISBA-TRIP, is run with a resolution of 0.5° and 3h, and several rainfall products were used as forcing. Products derived from gauges (KRIG, CPC), pure satellite products (TAPEER, 3B42RT, CMORPH, PERSIANN) and mixed satellite products adjusted by rain gauges (3B42v7, RFE2, PERSIANN-CDR). This work confirms the hydrological potential of satellite rainfall products and proposes an original approach to overcome their biases. It highlights the need for documenting the errors associated with the rainfall products and the error structure. Finally, the hydrological modelling results since the 1950s have given a new understanding of the relative role of rainfall and surface conditions in the drastic increase of flood risk in Niamey.

Esta pesquisa tem como finalidade discutir os impactos da variabilidade espacial e temporal de precipitações intensas nas vazões de cursos d\'água em bacias urbanizadas mediante a análise de dados históricos da pluviometria obtidos durante eventos críticos. A bacia hidrográfica do rio Tietê, em sua porção mais urbanizada, é a área objeto deste estudo. Após uma revisão sobre o tema na literatura específica, foram desenvolvidas chuvas de projeto com os padrões observados e com padrões teóricos, frequentemente utilizados na geração das tormentas sintéticas. O volume total precipitado foi associado ao período de retorno (TR) de 100 anos, a partir da análise estatística de chuvas pontuais e pela aplicação de fatores de redução de área (FRA) observados na área em estudo e de outras regiões, que vêm sendo utilizados em projetos de drenagem, sem qualquer estudo de validação; o intuito foi o de demonstrar a importância da definição de FRA específicos, a fim de evitar superdimensionamentos e otimizar as soluções. As chuvas de projeto foram aplicadas num modelo matemático de transformação chuva-vazão, devidamente calibrado, para obtenção das vazões de projeto resultantes no limite de jusante da bacia hidrográfica, frente aos diferentes padrões de solicitações hidrológicas. Para auxiliar a calibração do modelo estavam disponíveis dados dos postos telemétricos do Sistema de Alerta a Inundações de São Paulo - SAISP, curvas-chave e, para melhor representação dos eventos de precipitação observados, pode-se contar com as imagens do radar de Ponte Nova, em complementação às informações da rede de superfície. A comparação dos resultados obtidos no modelo hidrológico mostrou que os efeitos dos parâmetros variáveis (volume, distribuição espacial e temporal) são expressivos na composição dos hidrogramas de projeto. Dos testes realizados, identificaram-se as situações mais e menos críticas para a bacia, em termos de distribuição espacial e temporal e duração da chuva de projeto, além de estabelecer as diferenças no dimensionamento do sistema de drenagem pela adoção de FRA específico. Concluiu-se que, pela metodologia proposta, é possível chegar a vazões máximas de projeto apenas pela simulação de tormentas sintéticas, com diferenças de 10% a 20% das tormentas observadas maximizadas. Há, no entanto, a necessidade de realização de estudos adicionais, tanto para definição dos valores de FRA específicos, quanto de simulação de quantidade maior de padrões críticos observados, para a aplicação prática das indicações desse estudo com maior confiabilidade. / This research aims to discuss the impact of the spatial and temporal variability of heavy rainfall in the river flows in urbanized catchments by the historical rainfall data analysis obtained during critical events. The Tiete River catchment, in its most urbanized portion, is the subject of study of this research. After a review of the subject in the specific literature, design rainfall was developed along with the observed and theoretical patterns, often used in the generation of synthetic storms. The total volume precipitated was associated with the 100 years return period (RP), from the statistical analysis of point rainfall and for the application of areal reduction factors (ARF) observed in the study area and in other regions, which have been used in drainage projects without any validation study; the intention was to demonstrate the importance of the definition of specific ARF, in order to avoid oversizing and optimizing solutions. The design precipitation was applied on rainfall-runoff mathematical model, properly calibrated, so as to obtain the resulting design flow at the downstream boundary of the catchment, facing the different patterns of hydrological solicitations. In order to assist the calibration of the model, available data has been used from telemetric stations of the Sistema de Alerta a Inundações de São Paulo (São Paulo Flooding Alert System) - SAISP, discharge curves, and for better representation of the observed precipitation events, can be counted on the images taken from the Ponte Nova radar, as a complement to the information from the surface network. The comparison of the results of the hydrological model has shown that the effects of the variable parameters (volume, spatial and temporal distributions) are significant in the composition of the design hydrograph. Out of the performed tests, the most and the least critical situations were identified concerning the catchment in terms of both spatial and temporal distribution as well as the duration of the design storm. Also, the differences in the dimensions of the of the drainage system design were established by the adoption of specific ARF. Thus, it has been concluded, according to the proposed methodology, that it is possible to reach maximum design flow just by simulating synthetic storms, with differences ranging from 10% to 20% of the observed storms maximized. However, there is a need for additional studies, either to set up setting specific values of ARF or to simulate a larger quantity of critical patterns observed, in order to apply the indications of this study with higher reliability.

Die vorliegende Arbeit 'Abflu&szlig;entwicklung in Teileinzugsgebieten des Rheins - Simulationen f&uuml;r den Ist-Zustand und f&uuml;r Klimaszenarien' untersucht Auswirkungen m&ouml;glicher zuk&uuml;nftiger Klima&auml;nderungen auf das Abflu&szlig;geschehen in ausgew&auml;hlten, durch Mittelgebirge gepr&auml;gten Teileinzugsgebieten des Rheins: Mosel (bis Pegel Cochem); Sieg (bis Pegel Menden 1) und Main (bis Pegel Kemmern).<br><br>In einem ersten Schritt werden unter Verwendung des hydrologischen Modells HBV-D wichtige Modellprozesse entsprechend der Einzugsgebietscharakteristik parametrisiert und ein Abbild der Gebietshydrologie erzeugt, das mit Zeitreihen gemessener Tageswerte (Temperatur, Niederschlag) eine Zeitreihe der Pegeldurchfl&uuml;sse simulieren kann. Die G&uuml;te der Simulation des Ist-Zustandes (Standard-Me&szlig;zeitraum 1.1.1961-31.12.1999) ist f&uuml;r die Kalibrierungs- und Validierungszeitr&auml;ume in allen Untersuchungsgebieten gut bis sehr gut.<br>Zur Erleichterung der umfangreichen, zeitaufwendigen einzugsgebietsbezogenen Datenaufbereitung f&uuml;r das hydrologische Modell HBV-D wurde eine Arbeitsumgebung auf Basis von Programmerweiterungen des Geoinformationssystems ArcView und zus&auml;tzlichen Hilfsprogrammen entwickelt. Die Arbeitsumgebung HBV-Params enth&auml;lt eine graphische Benutzeroberfl&auml;che und r&auml;umt sowohl erfahrenen Hydrologen als auch hydrologisch geschulten Anwendern, z.B. Studenten der Vertiefungsrichtung Hydrologie, Flexibilit&auml;t und vollst&auml;ndige Kontrolle bei der Ableitung von Parameterwerten und der Editierung von Parameter- und Steuerdateien ein. Somit ist HBV-D im Gegensatz zu Vorl&auml;uferversionen mit rudiment&auml;ren Arbeitsumgebungen auch au&szlig;erhalb der Forschung f&uuml;r Lehr- und &Uuml;bungszwecke einsetzbar.<br><br>In einem zweiten Schritt werden Gebietsniederschlagssummen, Gebietstemperaturen und simulierte Mittelwerte des Durchflusses (MQ) des Ist-Zustandes mit den Zust&auml;nden zweier Klimaszenarien f&uuml;r den Szenarienzeitraum 100 Jahre sp&auml;ter (2061-2099) verglichen. Die Klimaszenarien beruhen auf simulierten Zirkulationsmustern je eines Modellaufes zweier Globaler Zirkulationsmodelle (GCM), die mit einem statistischen Regionalisierungsverfahren in Tageswertszenarien (Temperatur, Niederschlag) an Me&szlig;stationen in den Untersuchungsgebieten &uuml;berf&uuml;hrt wurden und als Eingangsdaten des hydrologischen Modells verwendet werden.<br>F&uuml;r die zweite H&auml;lfte des 21. Jahrhunderts weisen beide regionalisierten Klimaszenarien eine Zunahme der Jahresmittel der Gebietstemperatur sowie eine Zunahme der Jahressummen der Gebietsniederschl&auml;ge auf, die mit einer hohen Variabilit&auml;t einhergeht. Eine Betrachtung der saisonalen (monatlichen) &Auml;nderungsbetr&auml;ge von Temperatur, Niederschlag und mittlerem Durchflu&szlig; zwischen Szenarienzeitraum (2061-2099) und Ist-Zustand ergibt in allen Untersuchungsgebieten eine Temperaturzunahme (h&ouml;her im Sommer als im Winter) und eine generelle Zunahme der Niederschlagssummen (mit starken Schwankungen zwischen den Einzelmonaten), die bei der hydrologischen Simulation zu deutlich h&ouml;heren mittleren Durchfl&uuml;ssen von November bis M&auml;rz und leicht erh&ouml;hten mittleren Durchfl&uuml;ssen in den restlichen Monaten f&uuml;hren. Die St&auml;rke der Durchflu&szlig;erh&ouml;hung ist nach den individuellen Klimaszenarien unterschiedlich und im Sommer- bzw. Winterhalbjahr gegenl&auml;ufig ausgepr&auml;gt. Hauptursache f&uuml;r die simulierte starke Zunahme der mittleren Durchfl&uuml;sse im Winterhalbjahr ist die trotz Temperaturerh&ouml;hung der Klimaszenarien winterlich niedrige Evapotranspiration, so da&szlig; erh&ouml;hte Niederschl&auml;ge direkt in erh&ouml;hten Durchflu&szlig; transformiert werden k&ouml;nnen.<br>Der Vergleich der Untersuchungsgebiete zeigt in Einzelmonaten von West nach Ost abnehmende &Auml;nderungsbetr&auml;ge der Niederschlagssummen, die als Hinweis auf die Bedeutung der Kontinentalit&auml;tseinfl&uuml;sse auch unter ge&auml;nderten klimatischen Bedingungen in S&uuml;dwestdeutschland aufgefa&szlig;t werden k&ouml;nnten.<br>Aus den regionalisierten Klimaszenarien werden &Auml;nderungsbetr&auml;ge f&uuml;r die Modulation gemessener Zeitreihen mittels synthetischer Szenarien abgeleitet, die mit einem geringen Rechenaufwand in hydrologische Modellantworten &uuml;berf&uuml;hrt werden k&ouml;nnen. Die direkte Ableitung synthetischer Szenarien aus GCM-Ergebniswerten (bodennahe Temperatur und Gesamtniederschlag) an einzelnen GCM-Gitterpunkten erbrachte unbefriedigende Ergebnisse.<br>Ob, in welcher H&ouml;he und zeitlichen Verteilung die in den (synthetischen) Szenarien verwendeten Niederschlags- und Temperatur&auml;nderungen eintreten werden, kann nur die Zukunft zeigen. Eine Absch&auml;tzung, wie sich die Abflu&szlig;verh&auml;ltnisse und insbesondere die mittleren Durchfl&uuml;sse der Untersuchungsgebiete bei m&ouml;glichen &Auml;nderungen entwickeln w&uuml;rden, kann jedoch heute schon vorgenommen werden. <br><br>Simulationen auf Szenariogrundlagen sind ein Weg, unbekannte zuk&uuml;nftige Randbedingungen sowie regionale Auswirkungen m&ouml;glicher &Auml;nderungen des Klimasystems ausschnittsweise abzusch&auml;tzen und entsprechende Risikominderungsstrategien zu entwickeln. Jegliche Modellierung und Simulation nat&uuml;rlicher Systeme ist jedoch mit betr&auml;chtlichen Unsicherheiten verkn&uuml;pft. Vergleichsweise gro&szlig;e Unsicherheiten sind mit der zuk&uuml;nftigen Entwicklung des sozio&ouml;konomischen Systems und der Komplexit&auml;t des Klimasystems verbunden. Weiterhin haben Unsicherheiten der einzelnen Modellbausteine der Modellkette Emissionsszenarien/Gaszyklusmodelle - Globale Zirkulationsmodelle/Regionalisierung - hydrologisches Modell, die eine Kaskade der Unsicherheiten ergeben, neben Datenunsicherheiten bei der Erfassung hydrometeorologischer Me&szlig;gr&ouml;&szlig;en einen erheblichen Einflu&szlig; auf die Vertrauensw&uuml;rdigkeit der Simulationsergebnisse, die als ein dargestellter Wert eines Ergebnisbandes zu interpretieren sind.<br><br>Der Einsatz <br>(1) robuster hydrologischer Modelle, die insbesondere temperaturbeeinflu&szlig;te Prozesse ad&auml;quat beschreiben,<br>(2) die Verwendung langer Zeitreihen (wenigsten 30 Jahre) von Me&szlig;werten und<br>(3) die gleichzeitige vergleichende Betrachtung von Klimaszenarien, die auf unterschiedlichen GCMs beruhen (und wenn m&ouml;glich, verschiedene Emissionsszenarien ber&uuml;cksichtigen),<br>sollte aus Gr&uuml;nden der wissenschaftlichen Sorgfalt, aber auch der besseren Vergleichbarkeit der Ergebnisse von Regionalstudien im noch jungen Forschungsfeld der Klimafolgenforschung beachtet werden. / This thesis 'Development of runoff in subcatchments of the River Rhine - simulations of the current state and for climate change scenarios' investigates the impacts of possible future climate changes on runoff and runoff regime in selected subcatchments of the River Rhine. The regional climate in the selected subcatchments Mosel (up to gauge Cochem), Sieg (gauge Menden 1) and Main (gauge Kemmern) is affected by the middle mountain ranges.<br><br>In a first step, important model processes are parameterized according to catchment characteristics. A representation of the regional hydrology is then produced by using the hydrological model HBV-D. Based on time series of daily measurements (temperature, precipitation) at stations within the catchment, this representation can be used to realistically simulate time series of runoff and discharge. <br>In all examined areas, the quality of simulations of the calibration and validation periods for the current state (standard period of measurements 01/01/1961-12/31/1999) can be regarded as good to excellent. <br>To aid the catchment-specific, extensive and time-consuming data processing, a working environment for the hydrological model HBV-D has been developed. It is based on program extensions of the geographical information system ArcView and further programs. The working environment HBV-Params contains a graphical interface that gives both experienced hydrologists and students full control and enables them to flexibly derive parameter values and edit parameter and control files. In contrast to previous versions with only rudimentary working environments, HBV-D can therefore be utilized for research as well as for educational purposes. <br><br>In a second step, the current states of areal precipitation, areal temperature and simulated mean discharge (MQ) are compared to the corresponding states for two scenarios of future climate changes (100 years later, 2061-2099). These scenarios are based on simulated global circulations of one model run for each of two global circulation models (GCM). These global circulations are regionalized (downscaled) using a statistical approach into scenario time series of daily values (temperature, precipitation - input for the hydrological model) at control stations within the individual catchments. <br>For the second half of the 21st century, both regionalized climate change scenarios indicate increases in the mean annual areal temperature and mean annual sum of precipitation, along with a high variability of the latter. The seasonal (monthly) changes in temperature, precipitation and mean discharge between scenario state (2061-2099) and current state indicate increases in temperature (higher in summer than in winter) as well as a general increase in precipitation sums (strong fluctuations between individual months). In the hydrological simulations for all investigated catchments, this results in considerably higher mean discharges from November to March and small increases in mean discharge for the other months. The magnitude of the increases in discharge depends on the individual climate change scenario, one showing higher increases than the other during the summer half-year and vice versa for the winter half-year. The main reason for the simulated strong increase in mean discharge during winter half-year is, in spite of higher temperatures, the still relatively low evapotranspiration which allows higher precipitation to be directly transformed into higher discharges. <br>The comparison of the investigated catchments shows decreasing amounts of changes in the sum of precipitation from West to East in individual months. This indicates the importance of continentality under changed climatic conditions in Southwest Germany. <br>For the modification of measured time series (temperature, precipitation), which can be easily converted as synthetic scenarios into simulated hydrological results, amounts of change are derived from regionalized (downscaled) climate change scenarios. The derivation of synthetic scenarios directly from GCM output at individual GCM gridpoints yielded unsatisfactory results. <br>Only the future itself can show whether the timing and amount of changes in temperature and precipitation used in (synthetic) climate change scenarios come close to reality. An assessment of possible developments in runoff regime and specifically mean discharge under possible changed climatic conditions in the investigated catchments is already feasible today. <br><br>Simulations based on scenarios are one way to establish unknown future boundary conditions for the estimation of regional impacts of possible changes of the climate system. Nevertheless, all types of modeling and simulation of natural systems are linked with uncertainties. Rather large uncertainties persist regarding the future development of the socio-economic system and the complexity of the climate system and earth system. Furthermore, besides data uncertainties associated with the measurement of hydro-meteorological values, uncertainties associated with individual components of the model chain emission scenarios/gas cycle model - GCM/regionalization - hydrological model, which form a cascade of uncertainty, have a great influence on the trustworthiness of the simulation results (which are understood as one shown value within a range of results). <br><br>In the young field of climate impact research the use of <br>(1) robust hydrological models that adequately describe temperature-dependent processes,<br>(2) long time series (at least 30 years long) of measurements, <br>(3) concurrent comparisons of climate change scenarios, based on different GCMs (and, if possible, different emission scenarios)<br>should be considered for reasons of scientific thoroughness and to improve comparability of regional impact studies.

There is ample growth in scientific evidence about climate change. Since, hydrometeorological processes are sensitive to climate variability and changes, ascertaining the linkages and feedbacks between the climate and the hydrometeorological processes becomes critical for environmental quality, economic development, social well-being etc. As the river basin integrates some of the important systems like ecological and socio-economic systems, the knowledge of plausible implications of climate change on hydrometeorology of a river basin will not only increase the awareness of how the hydrological systems may change over the coming century, but also prepare us for adapting to the impacts of climate changes on water resources for sustainable management and development. In general, quantitative climate impact studies are based on several meteorological variables and possible future climate scenarios. Among the meteorological variables, sic “cardinal” variables are identified as the most commonly used in impact studies (IPCC, 2001). These are maximum and minimum temperatures, precipitation, solar radiation, relative humidity and wind speed. The climate scenarios refer to plausible future climates, which have been constructed for explicit use for investigating the potential consequences of anthropogenic climate alterations, in addition to the natural climate variability. Among the climate scenarios adapted in impact assessments, General circulation model(GCM) projections based on marker scenarios given in Intergovernmental Panel on Climate Change’s (IPCC’s) Special Report on Emissions Scenarios(SRES) have become the standard scenarios. The GCMs are run at coarse resolutions and therefore the output climate variables for the various scenarios of these models cannot be used directly for impact assessment on a local(river basin)scale. Hence in the past, several methodologies such as downscaling and disaggregation have been developed to transfer information of atmospheric variables from the GCM scale to that of surface meteorological variables at local scale. The most commonly used downscaling approaches are based on transfer functions to represent the statistical relationships between the large scale atmospheric variables(predictors) and the local surface variables(predictands). Recently Support vector machine (SVM) is proposed, and is theoretically proved to have advantages over other techniques in use such as transfer functions. The SVM implements the structural risk minimization principle, which guarantees the global optimum solution. Further, for SVMs, the learning algorithm automatically decides the model architecture. These advantages make SVM a plausible choice for use in downscaling hydrometeorological variables. The literature review on use of transfer function for downscaling revealed that though a diverse range of transfer functions has been adopted for downscaling, only a few studies have evaluated the sensitivity of such downscaling models. Further, no studies have so far been carried out in India for downscaling hydrometeorological variables to a river basin scale, nor there was any prior work aimed at downscaling CGCM3 simulations to these variables at river basin scale for various IPCC SRES emission scenarios. The research presented in the thesis is motivated to assess the impact of climate change on streamflow at river basin scale for the various IPCC SRES scenarios (A1B, A2, B1 and COMMIT), by integrating implications of climate change on all the six cardinal variables. The catchment of Malaprabha river (upstream of Malaprabha reservoir) in India is chosen as the study area to demonstrate the effectiveness of the developed models, as it is considered to be a climatically sensitive region, because though the river originates in a region having high rainfall it feeds arid and semi-arid regions downstream. The data of the National Centers for Environmental Prediction (NCEP), the third generation Canadian Global Climate Model (CGCM3) of the Canadian Center for Climate Modeling and Analysis (CCCma), observed hydrometeorological variables, Digital Elevation model (DEM), land use/land cover map, and soil map prepared based on PAN and LISS III merged, satellite images are considered for use in the developed models. The thesis is broadly divided into four parts. The first part comprises of general introduction, data, techniques and tools used. The second part describes the process of assessment of the implications of climate change on monthly values of each of the six cardinal variables in the study region using SVM downscaling models and k-nearest neighbor (k-NN) disaggregation technique. Further, the sensitivity of the SVM downscaling models to the choice of predictors, predictand, calibration period, season and location is evaluated. The third part describes the impact assessment of climate change on streamflow in the study region using the SWAT hydrologic model, and SVM downscaling models. The fourth part presents summary of the work presented in the thesis, conclusions draws, and the scope for future research. The development of SVM downscaling model begins with the selection of probable predictors (large scale atmospheric variables). For this purpose, the cross-correlations are computed between the probable predictor variables in NCEP and GCM data sets, and the probable predictor variables in NCEP data set and the predictand. A pool of potential predictors is then stratified (which is optional and variable dependant) based on season and or location by specifying threshold values for the computed cross-correlations. The data on potential predictors are first standardized for a baseline period to reduce systemic bias (if any) in the mean and variance of predictors in GCM data, relative to those of the same in NCEP reanalysis data. The standardized NCEP predictor variables are then processed using principal component analysis (PCA) to extract principal components (PCs) which are orthogonal and which preserve more than 98% of the variance originally present in them. A feature vector is formed for each month using the PCs. The feature vector forms the input to the SVM model, and the contemporaneous value of predictand is its output. Finally, the downscaling model is calibrated to capture the relationship between NCEP data on potential predictors (i.e feature vectors) and the predictand. Grid search procedure is used to find the optimum range for each of the parameters. Subsequently, the optimum values of parameters are obtained from the selected ranges, using the stochastic search technique of genetic algorithm. The SVM model is subsequently validated, and then used to obtain projections of predictand for simulations of CGCM3. Results show that precipitation, maximum and minimum temperature, relative humidity and cloud cover are projected to increase in future for A1B, A2 and B1 scenarios, whereas no trend is discerned with theCOMMIT. The projected increase in predictands is high for A2 scenario and is least for B1 scenario. The wind speed is not projected to change in future for the study region for all the aforementioned scenarios. The solar radiation is projected to decrease in future for A1B, A2 and B1 scenarios, whereas no trend is discerned with the COMMIT. To assess the monthly streamflow responses to climate change, two methodologies are considered in this study namely (i) downscaling and disaggregating the meteorological variables for use as inputs in SWAT and (ii) directly downscaling streamflow using SVM. SWAT is a physically based, distributed, continuous time hydrological model that operates on a daily time scale. The hydrometeorologic variables obtained using SVM downscaling models are disaggregated to daily scale by using k-nearest neighbor method developed in this study. The other inputs to SWAT are DEM, land use/land cover map, soil map, which are considered to be the same for the present and future scenarios. The SWAT model has projected an increase in future streamflows for A1B, A2 andB1 scenarios, whereas no trend is discerned with the COMMIT. The monthly projections of streamflow at river basin scale are also obtained using two SVM based downscaling models. The first SVM model (called one-stage SVM model) considered feature vectors prepared based on monthly values of large scale atmospheric variables as inputs, whereas the second SVM model (called two-stage SVM model) considered feature vectors prepared from the monthly projections of cardinal variables as inputs. The trend in streamflows projected using two-stage SVM model is found to be similar to that projected by SWAT for each of the scenarios considered. The streamflow is not projected to change for any of the scenarios considered with the one-stage SVM downscaling model. The relative performance of the SWAT and the two SVM downscaling models in simulating observed streamflows is evaluated. In general, all the three models are able to simulate the streamflows well. Nevertheless, the performance of SWAT model is better. Further, among the two SVM models, the performance of one-stage streamflow downscaling model is marginally better than that of the two-stage streamflow downscaling model.