Made available in DSpace on 2015-04-22T22:02:17Z (GMT). No. of bitstreams: 1 ana karolina.pdf: 4541487 bytes, checksum: d0e6cad6293572a6e9b57e1920b64f33 (MD5) Previous issue date: 2008-08-22 / The hydrological cycle of the rivers is the main source of the renewal of the fertility on floodplains and has a great influence on the limnological characteristics of Amazonian waters. The extraction of petroleum in the headwaters of the Urucu River and the construction of the Urucu-Coari-Manaus gas pipeline are sources of possible anthropic impacts in the region. The seasonal and spatial variation of temperature, pH, electrical conductivity and dissolved oxygen were studied in the water column of the Urucu, Solimões and Negro rivers. Also, major cations (Na, K, Ca and Mg) and the trace elements (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb e Zn) were studied in the sub-surface waters of the same rivers during the rising water period, peak high water period, falling water period and peak low water period during the hydrological cycle of the year 2006. The variables in the water column were measured with digital probes. For all other parameters water samples were collected just below the surface with a Ruttner sampler, filtered and preserved. The alkali metals were analyzed by Flame Photometry and the alkaline-earth metals and trace elements by Flame Atomic Absorption Spectroscopy. The data were evaluated with ANOVA to establish the existence of the variation of the chemical elements between the different periods of the hydrological cycle and between rivers. In order to recognize patterns in the behavior of the variables a Principal Components (PCA) and a Hierarchical Cluster (HCA) analysis were applied. In general there are hidrochemical similarities between the Urucu and Negro rivers, in the Solimões River the concentration of the elements is greater, especially calcium and there is variability depending on the phase of the hydrological cycle. In the Urucu River the limnological variables increased from the rising water period to the peak low water period. In the Solimões River pH and dissolved oxygen increased from the rising water period to the falling water period while temperature and electrical conductivity decreased from the rising water period to the peak high water period and increased thereafter up to the peak low water period. In the Negro River pH and oxygen increased during the peak high water period and peak low water period. Temperature decreased from the rising water period to peak high water period and increased from the high water period to peak low water period, conductivity was constant during the hydrological cycle with a small increase at the peak high water period and lower values during the peak low water period. In all three rivers the greatest temperatures were registered during the low water period. Considering the entire hydrological cycle the dominance of the major elements was K+>Ca2+>Na+>Mg2+ for the Urucu and Negro Rivers and Ca2+>Mg2+>Na+>K+ for the Solimões River. Throughout the hydrological cycle the mean sum of all the major elements in the Solimões River (14,003mg/L) was about 5.3 times greater than that of the Urucu River and 14 times greater than the Negro river, with emphasis on calcium which was 10 times greater than the greatest element in the other two rivers. According to the ANOVA there was no significant variation between the different periods of the hydrological cycle in the Urucu River for the concentrations of Cd, Cr e Ni; in the Solimões River for the concentrations of Na, Cd, Co e Cu; and in the Negro River of K, Ca, Mg, Cu, Ni e Pb. Between the rivers, for the major part of the hydrological cycle, principally during the rising water period, there was no significant variation between the Urucu and Negro rivers. The PCA and the HCA lend support to the similarities between the Urucu and Negro rivers, the differences between these rivers and the Solimões River and the significant correlations between all the trace elements and the major elements with the exception of Fe which had no correlation with any element. Therefore this study shows that there are seasonal and spatial variations in the concentrations of major and trace elements between the three rivers. The data should be looked upon as those of a practically unaltered equatorial ecosystem and in this manner become part of a basic data base for posterior comparisons and subsidize research with respect to nutrient fluxes in the drainage basins of the three rivers for the evaluation of an eventual anthropogenic impact. / O ciclo hidrológico dos rios é a principal fonte de renovação da fertilidade das áreas inundáveis e exerce influência marcante nas características limnológicas das águas amazônicas. A extração de petróleo nas cabeceiras do rio Urucu e a construção do gasoduto Urucu-Coari-Manaus são fontes de possíveis impactos antrópicas nesse percurso. Foram estudadas a variação sazonal e espacial de temperatura, pH, condutividade e oxigênio dissolvido nos Urucu, Solimões e Negro; e de elementos majoritários (Na, K, Ca e Mg) e elementos-traço (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb e Zn) na camada sub-superficial dos mesmos rios na enchente, cheia, vazante e seca do ciclo hidrológico de 2006. As variáveis na coluna de água foram medidas com potenciômetros digitais. Para as outras determinações foram coletadas amostras de água na sub-superfície com garrafa de Ruttner, filtradas e preservadas. Os metais alcalinos foram analisados por Fotometria de Chama e os alcalinos terrosos e elementos-traço por Espectrometria de Absorção Atômica de Chama. Os dados obtidos foram avaliados por ANOVA, para estabelecer a existência de variação dos elementos químicos entre fases do ciclo hidrológico e entre os rios. Para o reconhecimento de padrões no comportamento das variáveis foram utilizadas a análise de Componentes Principais (PCA) e de Agrupamentos Hierárquicos (HCA). De modo geral, destaca-se que há semelhanças hidroquímicas entre os rios Urucu e Negro; que no Solimões as concentrações dos elementos químicos são freqüentemente maiores, especialmente o cálcio; e que há variação de acordo com a fase do ciclo hidrológico. As variáveis limnológicas no rio Urucu apresentaram maiores valores no sentido enchente-cheia-vazante-seca. No rio Solimões os valores de pH e oxigênio dissolvido aumentaram da enchente para a vazante, enquanto que a temperatura e a condutividade elétrica diminuíram da enchente para a cheia e aumentaram da cheia para aseca. No rio Negro o pH e o oxigênio aumentaram na cheia e na seca, a temperatura diminui da enchente para a cheia e aumentou da cheia para a seca; a condutividade permaneceu praticamente inalterada com discreto aumento na cheia e menores valores na seca. Em todos os ambientes as maiores temperaturas foram registradas no período de águas baixas. Considerando todo o ciclo hidrológico a relação de dominância para os elementos majoritários ficou estabelecida em: K+>Ca2+>Na+>Mg2+ para os rios Urucu e Negro e, Ca2+>Mg2+>Na+>K+ para o Solimões. Para o mesmo período a soma média de todos os 10 majoritários no Solimões (14,003 mg/L) foi cerca de 5,3 vezes maior do que no Urucu e 14 vezes maior do que no rio Negro, destacando-se o cálcio com teor até 10 vezes maior que o elemento em maior concentração nos outros dois rios. De acordo com a ANOVA, entre as fases não houve variação significativa no rio Urucu para as concentrações de Cd, Cr e Ni; no rio Solimões, para os teores de Na, Cd, Co e Cu; e no rio Negro para as concentrações de K, Ca, Mg, Cu, Ni e Pb. Entre os rios, na maior parte do ciclo hidrológico, principalmente na enchente, não houve variação significativa entre Urucu e Negro. A PCA e a HCA corroboraram as semelhanças entre Urucu e Negro, as diferenças entre estes rios e o Solimões e as correlações significativas entre todos os elementos-traço e majoritários, com exceção do Fe, sem correlação com qualquer elemento. Portanto, este estudo comprova que há variação sazonal e espacial das concentrações de elementos majoritários e elementos-traço entre os três rios estudados. Os dados apresentados devem ser vistos como os de um ecossistema equatorial praticamente inalterado podendo, desta forma, tornarem-se parte de um banco básico de dados para comparações posteriores e subsidiar pesquisas quanto ao fluxo de nutrientes na área de drenagem nestas bacias para avaliação de atividades antropogênicas nesses rios no futuro.

This diploma thesis deals with the analysis of the factors which influence the direct drainage from the drainage area. The thesis specifically deals with the drainage area of the Kopaninský brook. Drainage is always influenced by several factors at the same time. These factors are above all climate, anthropogenic impact, underdrainage, shape and extent of a drainage area, land use, geologic structure, location and altitude of a drainage area. The direct drainage can be separated by different methods (modificated semi-graphical method, GROUND method, method of hydrogram separation, method of digitals filtres) or CN- curves can be used for calculation. This thesis used the method of CN curves to process the results of a given drainage area. In the methodical part of the thesis I reached to the creation of direct drainage maps with the utilisation of the BPEJ maps together with the input data gained by the method of CN curves. These outputs were created at different values of design rains repetition time N= 2, 10, 50 and 100 years. The volume of a direct drainage was calculated by a classic method and by a method using the ArcMap programme. Another part of the thesis was simulation of different area utilisation situations (real condition versus grassing of ploughland) and saturation of drainage area, or more precisely water content in soil (dry soil, middle dry soil, wet soil).

This thesis deals with the event-based rainfall-runoff modelling of the selected river basin. This thesis is based on my previous work "Factors affecting the water discharge from the river basin during rainfall-runoff events". In that work I described factors, which have effect on water runoff from the river basin. This thesis was solved on basin of Jílecký stream. Water runoff from basin is affected with a number of factors, the most significant are slope of the terrain, soil saturation, geological and pedological conditions, vegetation cover and anthropogenic influence. Calculations of direct runoff were realised with method of CN curves, with using BPEJ map, land use map gained from Corine Land Cover 2006 and maximum daily precipitation sums with 2, 10, 20, 50 and 100 years probabilities recurrence obtained from the rainfall station Netřebice. Calculations were performed in a numerical method using vector data and a raster method performed in ArcMap. In the next step I performed simulations of various scenarios of change in river basic characteristics such as soil saturation change, grassing of arable land with a slope greater than 12°, grassing of all arable land and enlargement the built-up area in the river basin.

Dans un contexte de changement climatique dont les projections régionales sont incertaines, de forte variabilité inter-annuelle du cycle hydrologique, de forte croissance démographique et de changement d'occupation des sols, les questions relatives au cycle hydrologique et à la ressource en eau actuels et à venir sont cruciales. Dans un tel contexte, ce travail de thèse approfondit la connaissance du fonctionnement hydrologique du bassin versant de l'Ouémé supérieur (situé en climat soudanien au Bénin), en considérant l'ensemble des termes et des processus du cycle hydrologique.Dans un premier temps, le fonctionnement hydrologique de l'Ouémé supérieur est analysé à l'échelle d'un versant grâce au modèle Hydrus 2D. Cette analyse de processus s'appuie sur un ensemble complet de mesures (précipitations, évapotranspiration, humidité du sol, niveau piézométrique, débit en rivière) obtenues dans le cadre de l'observatoire hydrométéorologique AMMA-CATCH. Les simulations montrent que la forêt ripisylve vidange la nappe profonde et la déconnecte ainsi du réseau hydrographique. L'apport d'eau de la nappe profonde permet une transpiration de la forêt ripisylve toute l'année, y compris en saison sèche. Les écoulements en rivière ne sont pas produits uniquement par exfiltration d'écoulements latéraux de subsurface non saturés, les bas-fonds jouent probablement un rôle.À méso-échelle, nous cherchons à quantifier l'impact de la variabilité spatiale de la conductivité hydraulique à saturation sur le bilan hydrologique et l'évapotranspiration. Le modèle numérique utilisé est nTopAMMA, formalisme dérivé de TopMODEL. À partir de mesures de terrain, nous avons mis en évidence que la variabilité spatiale de la conductivité hydraulique à saturation est corrélée à l'occupation du sol du bassin d'étude. La prise en compte de cette variabilité spatiale dans le modèle nTopAMMA montre que l'état hydrique et l'évapotranspiration simulés localement par le modèle dépendent aux trois-quarts de la topographie et pour un quart de la conductivité hydraulique à saturation.Adoptant une approche ascendante, nous confrontons la représentation élaborée à l'échelle du versant à la modélisation hydrologique à méso-échelle. Nous analysons les processus et flux verticaux du modèle nTopAMMA. L'amélioration de la modélisation du cycle hydrologique de l'Ouémé supérieur par le modèle nTopAMMA nécessite (i) la prise en compte des hétérogénéités du bassin versant, (ii) la modification du formalisme de l'évapotranspiration, (iii) la diversification des sources de prélèvements évapotranspiratoires et (iv) l'intégration de la nappe d'altérites. / Understanding how the hydrological cycle and water resources availability evolve in the current context of global change (which encompass climate, environmental and population changes) is a critical issue, particularly in West Africa, where at regional scale, strong interannual and seasonal variabilities overlap with highly uncertain climate predictions. Within this framework, this work aims at improving our knowledge of the behavior of the Upper Oueme catchment in Benin (Sudanian climate), with an analysis of all the hydrological processes and terms of the terrestrial hydrological cycle.First, the hillslope scale is considered by using the Hydrus 2D software and field observations from the hydrometeorological observing system AMMA-CATCH: rainfall, actual evapotranspiration, soil moisture, groundwater level and river runoff. The principal result of this analysis is that the riparian forest transpiration depletes the deep groundwater and disconnects it from the river network. Water supply by the deep groundwater enables the riparian forest transpiration all year long and particularly during the dry season. Seepage of unsaturated subsurface lateral flows contributes to river runoff, but the "bas-fonds" seem to be other important contributors.Then, at mesoscale, we quantify the impact of the spatial variability of hydraulic conductivity on the simulated water balance, with focus on the evapotranspiration term. The numerical model nTopAMMA, especially derived from the TopMODEL hydrological model for the Upper Oueme catchment, is used here. Measurements from a specific field mission evidence the correlation between the hydraulic conductivity spatial variability and the land use one. By taking into account this variability, the simulation results show that evapotranspiration and water storage simulated on the Upper Oueme catchment at local (pixel) scale depend essentially on the topography (75 %) and to a lesser extent on the hydraulic conductivity (25 %).Finally, a bottom-up approach is adopted to analyse the hydrological modelling results at mesoscale, taking advantage of the modelling results at the hillslope scale. Vertical processes and fluxes simulated by nTopAMMA are analyzed. It is shown that an improvement of the Upper Oueme hydrological cycle modelling, with nTopAMMA, requires: (i) the consideration of the catchment heterogeneities, (ii) the modification of the evapotranspiration module, (iii) the diversification of the evapotranspiration sources and (iv) the integration of the deep groundwater reservoir.

L'étude des impacts du changement climatique demande souvent de mettre en place de longues chaînes de modélisation. Du modèle qui servira à estimer les concentrations futures en gaz à effet de serre jusqu'au modèle d'impact. Tout au long de cette chaîne de modélisation, les sources d'incertitudes s'accumulent et compliquent l'exploitation des résultats pour l'élaboration de stratégies d'adaptation. Il est proposé ici d'évaluer les impacts du changement climatique sur le cycle hydrologique en France ainsi que les incertitudes qui y sont associées. La contribution de chacune des sources d'incertitudes n'est pas abordée, principalement celle associée aux scénarios d'émission de gaz à effet de serre, aux modèles climatiques et à la variabilité interne. Nous proposons dans ce travail une approche pour évaluer la transférabilité dans un climat futur de la méthode statistique de régionalisation des simulations climatiques. La vérification de l'hypothèse de transférabilité effectuée est l'une des principales sources d'incertitudes des méthodes statistiques de régionalisation. L'évaluation proposée ici s'appuie sur l'utilisation de modèles régionaux, dans un cadre dit de modèle parfait, et permet de montrer que l'utilisation de certain prédicteurs s'avèrent utile à assurer la transférabilité de la méthode de régionalisation dans un climat futur. Cette approche proposée pour une méthode de désagrégation statistique est également applicable à des méthodes de correction des biais des modèles régionaux. Les récentes réanalyses atmosphériques sur l'ensemble du XXème siècle, régionalisées avec la méthode développée dans ce travail, et associées aux observations de température et précipitations permettent de caractériser le cycle hydrologique en France. Elles permettent notamment de montrer que la variabilité multi-décennale des débits observés pendant le XXème siècle est généralisée à l'ensemble du pays et est liée à la variabilité des conditions atmosphériques. Cette variabilité multi-décennale des débits est généralement plus faible dans les simulations hydrologiques réalisées avec les simulations historiques des modèles climatiques. Les projections climatiques ont été régionalisées avec la méthode développée dans ce travail. La température sur l'ensemble du pays, en moyenne sur les modèles climatiques, augmente jusqu'à 3,5°C en hiver et 6,5°C en été d'ici la fin du siècle. Les précipitations vont diminuer sur l'ensemble du pays en été, de presque moitié sur le sud du pays pour le scénario le plus sévère. En hiver, elles augmentent sur la moitié nord du pays et diminuent légèrement sur la partie sud. Dès les prochaines décennies, la diminution des précipitations est importante en été, l'évolution est moins marquée pour les autres saisons. Enfin, les résultats des projections hydrologiques réalisées avec un modèle hydrologique et un ensemble de modèles climatiques sont présentés pour les prochaines décennies et également pour la fin du XXIème siècle. Sur la Seine, les résultats sont différents en hiver de ceux présentés dans de précédentes études. Ici, les précipitations et les débits augmentent en hiver et diminuent en été sur ce bassin versant. Ailleurs en France, les résultats convergent avec les études précédentes, à savoir une augmentation de l'évapotranspiration, une diminution généralisée des débits et un assèchement des sols. L'incertitude due aux modèles climatiques et à la variabilité interne sur les changements relatifs de débits augmente systématiquement pendant le XXIème siècle, jusqu'à atteindre plus de 20% en hiver pour le scénario le plus sévère. Dans les prochaines décennies, l'incertitude due uniquement à la variabilité interne sur les changements de débits est aussi forte que l'incertitude due aux modèles climatiques et à la variabilité interne. Dès les prochaines décennies, les changements de débits annuels sont plus forts sur la Loire, la Garonne et le Rhône que les changements maximaux observés pendant le XXème siècle. / The assessment of the impact of climate change often requires to set up long chains of modeling, from the model to estimate the future concentration of greenhouse gases to the impact model. Throughout the modeling chain, sources of uncertainty accumulate making the exploitation of results for the development of adaptation strategies difficult. It is proposed here to assess impacts of climate change on the hydrological cycle over France and associated uncertainties. The contribution of each sources of uncertainty is not addressed, mainly that associated with greenhouse gases emission scenario, climate models and internal variability. In the context of impacts of climate change on the hydrological cycle over France, it is possible to ask what is the contribution of each sources of uncertainty to the total uncertainty associated with mean changes. Is it possible to reduce, and if so how, the contribution of one source or another ? We propose in this work an approach to assess the transferability in the future climate of a statistical method to downscale climate simulations. The transferability assumption is one the main sources of uncertainty in statistical downscaling method. The assessment suggested here relies on the use of regional climate models, in a perfect model framework, and shows that some predictors are useful to ensure the transferability of the downscaling method in the future climate. This framework, proposed for a statistical downscaling method, is also applicable to bias correction methods in regional climate models. Recent atmospheric reanalyses of the 20th century are downscaled with the method developed in this work, associated with observations of temperature and precipitation. The hydrological cycle over France is characterized with these reconstructions. We show that the multi-decadal variability of observed streamflows during the 20th century is generalized to the whole country and is partly due to atmospheric variability. This multi-decadal variability of streamflows is generally weaker in hydrological simulations done with historical simulations from climate models. The climate projections have been downscaled with the method developed in this work. The temperature on the country, on average over climate models, could increased by 3,5°C in winter and 6,5°C in summer in the course of this century. Precipitations will decrease all over the country in summer, nearly by half on southern part of France for the most severe scenario. In winter, precipitations will increase in the northern part of the country and will decrease slightly in the southern part. In the next few decades, the decrease in precipitation is important in summer, and changes are less pronounced for other seasons. Results of hydrological projections done with one hydrological model and an ensemble of climate models are presented for the coming decades and for the end of the century. On the Seine river, results slightly differ in winter from those presented in previous studies. Here, precipitations and streamflow increase in winter and decrease in summer on that river basin. Elsewhere in France, results are consistent with previous studies, namely an increase in evapotranspiration, a decrease in streamflow and much drier soil. The uncertainty due to both climate models and internal variability on relative changes in streamflows always increase during the 21st century, to over 20% in winter for the most severe scenario. In the coming decades, the uncertainty due to internal variability only on streamflow changes is as strong as the uncertainty due to both climate models and internal variability. In the coming decades, annual streamflow changes of the Loire, Garonne and Rhône rivers are stronger than the maximum changes observed during the 20th century.

Stable isotope ratios in rainwater and water vapor act as a tracers of the hydrological cycle. The data on stable isotopic composition in rainwater and water vapor are limited due to the lack of observational studies across the Indian subcontinent and over the ocean. These present day observations are important database to deduce the paleo-climatic condition from geological archives. In majority of the cases, isotopic records are translated into physical factors with the present background knowledge where relationships with physical variables are well established. In case of tropical region, the primary controlling factor identified behind the stable isotopic variations is the amount of rainfall. However recent observations contradict such relationships challenging the role of amount effect and identified source moisture effect on stable isotope ratios in rainwater at Indian stations. The thesis investigated the amount effect relationship of isotopes at seasonal time scales. The long period observation covering 4 years, where daily time interval rainwater samples collected were used for our study. We used two different station locations; Thiruvananthapuram and Bangalore, where monsoonal rainfall is received for Southwest and Northeast periods. The role of mesoscale and synoptic convection and rainout along the transport pathways were found responsible for the isotopic variance. The role of moisture source regions, rainout over the advection pathways, high rainfall producing systems such as depression and cyclones, and continental recycling of water on rainwater and water isotopes ratios were major findings of the thesis work which are detailed in the chapters. Upon knowing the atmospheric and oceanic condition at the moisture source region based on satellite data and reanalysis data set we modeled our observations using the governing equations of isotope fractionation and well accepted Rayliegh’s distillation model. The observations on rainwater and water vapor isotope ratios in oceanic region are extremely limited due to difficulties in conducting sampling. Water vapor and rainwater observations over the Southern Ocean during the expedition of 2013 and estimation of the moisture recycling across the latitudes over the oceanic regions is a novel work in this thesis.

Le Sahel est particulièrement exposé à la variabilité de la mousson Ouest-Africaine dont les répercussions socio-économiques peuvent prendre un caractère dramatique. Cette région est en outre confrontée à l'une des plus fortes croissances démographiques jamais observées, se traduisant par une pression toujours plus forte sur de faibles ressources naturelles et un environnement fragile. Dans ce contexte, un enjeu important se situe dans notre capacité à proposer des outils aidant au suivi des ressources hydriques et végétales, et permettant d'anticiper les impacts climatiques et anthropiques à moyen terme sur ces ressources. Pour cela, il est indispensable d'étudier et mieux comprendre les processus d'échanges d'énergie et de matière à l'interface terre-atmosphère, qui contribuent à la régulation de la mousson d'une part et gouvernent le cycle hydrologique local et le développement végétal d'autre part. Les travaux réalisés s'inscrivent dans cette problématique, portant précisément sur l'analyse des cycles de l'eau et de l'énergie en région sahélienne sous les effets combinés du climat et de l'activité humaine. La démarche s'appuie sur une méthodologie alliant observations in situ et modélisation à base physique. L'étude a été réalisée dans la région centrale du Sahel, dont le système agricole traditionnel associe pastoralisme et cultures pluviales en alternance avec la jachère. Elle s'est appuyée sur le réseau d'observations éco-hydrologiques et énergétiques acquises en continu durant 7 années (2005-2012) par l'Observatoire AMMA CATCH au Sud-Ouest Niger. La qualité et la cohérence de ces observations ont permis de dresser des grands traits du fonctionnement éco-hydrologique des deux couverts végétaux les plus répandus dans la région : cultures de mil et jachères arbustives. Les observations ne permettent cependant pas à elles seules d'établir des bilans complets aux différentes échelles temporelles d'intérêt (infra-journalière à interannuelle). Une modélisation couplée détaillée des cycles de l'énergie et de l'eau a par conséquent été élaborée pour ces deux couverts, à l'aide du modèle de transferts sol-plante-atmosphère SiSPAT. Etalonné sur une période de 2 ans, le modèle a ensuite été validé sur les 5 autres années d'observation, en contraignant les paramètres du modèle à des valeurs physiquement réalistes. En bon accord avec les observations, cette modélisation pluriannuelle s'est révélée être un outil d'analyse précieux, intégrant toute la pertinence, la richesse et la cohérence du jeu de données. La représentativité de la période étudiée a permis d'en exploiter les résultats pour (1) analyser l'impact de la variabilité climatique sur les bilans d'eau et d'énergie aux différentes échelles temporelles et (2) fournir une première climatologie des flux et stocks d'eau et d'énergie à l'interface sol-végétation-atmosphère, à ces mêmes échelles. Les similitudes et différences de fonctionnement éco-hydrologique et énergétique entre écosystèmes ont été mises en évidence. Par exemple, l'évapotranspiration représente plus de 80% des précipitations annuelles et près de la moitié du rayonnement global au cœur de la mousson pour les deux sites. Sa distribution saisonnière et son partitionnement en évaporation du sol et transpiration des plantes diffèrent néanmoins entre les deux écosystèmes, tout comme le ruissellement, et le drainage sous la zone racinaire. Ce dernier apparaît significatif pour le champ de mil mais pas pour la jachère. Une analyse de sensibilité des processus aux caractéristiques du sol et du couvert a été réalisée. La robustesse des résultats produits devrait leur permettre de servir de référence pour les études des processus hydrologiques et énergétiques dans cette région. La modélisation ainsi construite présente un potentiel évident pour des études prospectives, relatives notamment au changement climatique ou à une évolution des pratiques agricoles. / The Sahel region is particularly exposed to the variability of the West African Monsoon, which may lead to dramatic socio-economical consequences. This region also has one of the highest demographic growth rates, resulting in an ever-increasing pressure on the scarce natural resources and fragile environment. In this context, a major challenge lies in our ability to provide appropriate tools for the monitoring of hydrological and vegetation resources. These tools should also be suitable for the prediction of climatic and anthropogenic impacts in the medium term. This requires a better understanding of energy and matter transfer processes at the earth-atmosphere interface. Indeed, the latter both play a role in the regulation of the monsoon and also drive the local hydrological cycle and vegetation development. The present research follows such a framework and consists specifically in analyzing the water and energy cycles in the Sahel region under the combined effects of climate and human activity. This is undertaken by developing a methodology combining the use of in situ observations and physically-based modelling. The study was conducted in the central Sahel, where traditional agricultural systems are formed by the association of pastoralism and rain-fed crops in rotation with fallow cycles. This study was based on the network of eco-hydrological and energy data acquired continuously during 7 years (2005-2012) by the South-West Niger AMMA-CATCH Observatory. Quality and consistency of these observations allowed analyzing the main features of the eco-hydrological functioning of the two main land-covers in the region: millet and fallow savannah. However, observations alone were not sufficient to compute comprehensive water and energy budgets at all the different time scales of interest (sub-daily to inter-annual). A detailed modelling of coupled water and energy cycles was therefore undertaken for these two land-covers, using the soil-vegetation-atmosphere transfer model SiSPAT. The model was first calibrated on a 2-year period, and further validated on the remaining 5-year observations, by constraining model parameters to physically realistic values. This multi-year modelling was in good agreement with the observations, and provided a precious analysis tool that integrated the relevance, richness and consistency of the dataset. Thanks to the representativeness of the studied period, results served at the different temporal scales to (1) analyze the impact of climatic variability on water and energy budgets and (2) produce a preliminary climatology for the water and energy fluxes and storages at the soil-vegetation-atmosphere interface. Similarities and differences in eco-hydrological and energy functioning between ecosystems were evidenced. For instance, evapotranspiration represented more than 80% of annual precipitations and close to half of the global radiation at the heart of the monsoon for both sites. Seasonal distribution and partitioning of evapotranspiration between soil evaporation and plants transpiration differed between the two ecosystems, as well as the runoff, and the drainage below the root zone which appeared significant for the millet field but not for the fallow site. A sensitivity analysis of the energy and water budgets to soil and vegetation characteristics was conducted. Robustness of the produced results should enable them to serve as reference for studies of water and energy processes in this region. The resulting calibrated model showed an obvious potential for prospective studies, such as those on climate change or on the evolution of agricultural practices.

Le climat du Quaternaire est défini par une succession de périodes glaciaires et interglaciaires enregistrées dans les archives climatiques à différentes latitudes. La carotte de glace d’EPICA Dome C fournit un enregistrement haute résolution sur les derniers 800 ka du δ18Oatm (i.e. δ18O de la molécule d’oxygène de l’air) qui combine les variations passées du cycle hydrologique des basses latitudes et de la productivité de la biosphère. En l’absence du comptage des couches annuelles, ce proxy peut être utilisé comme méthode de datation orbitale des carottes de glace, en lien avec l’insolation au 21 juin à 65°N. Cependant, un décalage de 6 ka entre le δ18Oatm et l’insolation, généralement observé lors des terminaisons glaciaires-interglaciaires, est appliqué sur l’ensemble de l’enregistrement lors de la construction de l’échelle d’âge. Ce décalage et la complexité du signal du δ18Oatm expliquent l’incertitude élevée de 6 ka des carottes de glace, ce qui limite leur interprétation en termes de variations climatiques et environnementales conjointement à d’autres archives. J’ai donc développé une nouvelle chronologie pour les carottes de glace, basée sur le lien entre le δ18Oatm et le δ18Ocalcite des spéléothèmes est-asiatiques, à partir de nouvelles mesures isotopiques permettant d’avoir pour la première fois un enregistrement complet sur les derniers 800 ka à Dome C. Cette nouvelle chronologie permet de réduire les incertitudes par rapport à la chronologie actuelle et d’avoir une meilleure séquence des évènements entre les hautes et basses latitudes. J’ai ensuite développé un modèle simulant la composition isotopique de l’oxygène atmosphérique afin de répondre au manque d’interprétations quantitatives de ce proxy ainsi que pour vérifier son lien avec le δ18Ocalcite sur plusieurs cycles climatiques. Pour modéliser le δ18Oatm nous avons dû coupler le modèle climatique de complexité intermédiaire iLOVECLIM avec le modèle de végétation CARAIB. Le δ18Oatm simulé par le modèle couplé sur plusieurs dizaines de milliers d’années confirme que ses variations sont en phase avec celles de l’insolation de l’hémisphère Nord (hormis lors d’évènements de Heinrich) et avec celles du δ18Ocalcite via des modifications du cycle hydrologique des basses latitudes, impactant la composition isotopique de l’eau de pluie utilisée par la biosphère terrestre lors de la photosynthèse. / Quaternary glacial-interglacial cycles are recorded in various climatic archives from high to low latitudes. The EPICA Dome C ice core provides a high-resolution record over the last 800 ka of δ18Oatm (i.e. δ18O of atmospheric O2) which combines past variations of the low latitude water cycle and of the biosphere productivity. In absence of annual layer counting, this proxy can be used for orbital dating in association with the June 21st insolation at 65°N to build an ice core chronology. However a lag of 6 ka between the δ18Oatm and the insolation, classically observed during glacial-interglacial terminations, is applied to the entire record during the chronology construction. This lag and the complexity of the δ18Oatm signal are the main reasons why the ice core chronology presents a high 6 ka uncertainty which limits their interpretation, jointly with other paleoclimate archives, in terms of past climate and environmental variations. To solve this issue I have developed a new ice core chronology based on the relation between the δ18Oatm and the δ18Ocalcite of east-asian speleothems, using new isotope measurements allowing for the first time a complete record over the last 800 ka at Dome C. This new chronology reduces the uncertainties compared to the actual ice core chronology strongly based on δ18Oatm and shows a better sequence of events between the high and low latitudes records. Then, I have developed a model to reproduce the isotopic composition of atmospheric O2 to address the lack of quantitative interpretations of this proxy and to check our assumption of synchronicity with the δ18Ocalcite over several climatic cycles. To reproduce the variations of the δ18Oatm, it was necessary to couple the intermediate complexity climate model iLOVECLIM and the vegetation model CARAIB. Finally, the δ18Oatm variations simulated with the new coupled model over several thousand years are in phase with the insolation of the Northern hemisphere (except during Heinrich events) and with low latitudes δ18Ocalcite variations. This can be explained by changes in the low latitude water cycle related to changes in the isotopic composition of meteoric water used by the terrestrial biosphere during photosynthesis.

This study has looked at two separate locations, Malmö in Sweden, and Medellin in Colombia, and what the possibilities of rainwater harvesting are in those locations. The paper investigated data gathered by low-cost sensors in Malmö region, as well as sampling and measurements of rainwater collected in Malmö and Medellin, analysed by laboratories in both countries. Important data for the paper are quantity, quality, as well as environmental benefits and the economical perspective of rainwater harvesting. There are several steps that can be taken towards a more sustainable use of the Earth’s resources, and rainwater harvesting is included in the possibilities already at hand. But there is need for further development of monitoring and ways to qualify water for different purposes. It is possible to utilize rainwater for many things, and with that, ease the pressure on the local water supply infrastructure. This study has shown some important parts of that process, and that even low-cost sensors can help in gathering essential data for further evaluation of the usability of the rainwater. By collecting parts of the rainwater, flooding due to extensive downpour can be mitigated to some extent. Moreover, considering the low price of the sensors tested in this study, it is possible to use several low-cost sensors to determine the usability to some extent. Had the measurements rendered in values being too low compared to the laboratory results, the risk would have been greater. The consequence is that usable water could be regarded as not usable since the sensors returned an overall higher value compared to the laboratory results. Furthermore, the research found that the environmental benefit can be substantial. But there are more positive implications when gathering water for usage locally. For example, the water supply can become more distributed and with that, less prone to cause events such as water leaks, polluted water, and extreme events that have rendered an unserviceable infrastructure.

<p>The purpose of this thesis is to analyse interactions between freshwater flows, terrestrial ecosystems and human well-being. Freshwater management and policy has mainly focused on the liquid water part (surface and ground water run off) of the hydrological cycle including aquatic ecosystems. Although of great significance, this thesis shows that such a focus will not be sufficient for coping with freshwater related social-ecological vulnerability. The thesis illustrates that the terrestrial component of the hydrological cycle, reflected in vapour flows (or evapotranspiration), serves multiple functions in the human life-support system. A broader understanding of the interactions between terrestrial systems and freshwater flows is particularly important in light of present widespread land cover change in terrestrial ecosystems. </p><p>The water vapour flows from continental ecosystems were quantified at a global scale in Paper I of the thesis. It was estimated that in order to sustain the majority of global terrestrial ecosystem services on which humanity depends, an annual water vapour flow of 63 000 km3/yr is needed, including 6800 km3/yr for crop production. In comparison, the annual human withdrawal of liquid water amounts to roughly 4000 km3/yr. A potential conflict between freshwater for future food production and for terrestrial ecosystem services was identified. </p><p>Human redistribution of water vapour flows as a consequence of long-term land cover change was addressed at both continental (Australia) (Paper II) and global scales (Paper III). It was estimated that the annual vapour flow had decreased by 10% in Australia during the last 200 years. This is due to a decrease in woody vegetation for agricultural production. The reduction in vapour flows has caused severe problems with salinity of soils and rivers. The human-induced alteration of vapour flows was estimated at more than 15 times the volume of human-induced change in liquid water (Paper II). </p>