Tropical forests are under continual threat due to deforestation and forest fragmentation processes which are driven by the economic activities growth, mainly agriculture. Replacing forest with other land uses can cause severe impacts on river water quality, altering its physical, chemical and biological characteristics. The Atlantic Forest, in particular, had its original vegetation cover reduced to about 11%, wherein the crop lands expansion and urban sprawl still threatening this important ecosystem and the ecosystem services that it provides. In this sense, the main objective of this study was to investigate the relation between forest cover and water quality of tropical agricultural watersheds. For that, six experimental watersheds with different percentage of forest cover were selected in the Sarapuí River watershed, State of São Paulo, Brazil. Water samples were collected during a hydrologic year to obtain water quality parameters that represent impacts induced by anthropic activities. According to the percentage of forest cover, the watersheds were denominated as \"forested\", when they presented more than 55% of forest cover, and \"degraded\", with less than 35%. Multivariate statistical models were applied to identify differences between these two groups. In a second moment, the relation of land use/land cover within the watershed and within its respective riparian zone, represented in this study by the Permanent Preservation Areas (PPA), with water quality was compared through mixed models and redundancy analysis to identify the main factors that influenced water quality variability. Lastly, a watershed simulation modeling was applied to verify the impact of riparian forest restoration on water quality of the Sarapuí River watershed, wherein each experimental watershed was represented by a sub-watershed in the model. The results showed that the degraded watersheds presented higher values of solids, turbidity, nutrients and coliforms, besides presenting greater temporal data variability compared to forested watersheds. This variation is associated with the stream flow changes during the year. In general, forest cover was related to good water quality, while agriculture and urban areas were responsible for the water quality degradation. Pasture presented mixed impacts, but it was not generally correlated with poor water quality. The water quality parameters responded differently to the influence of land-use/land-cover patterns in the watershed and riparian zone, but the overall water quality is better explained by the landscape composition within the watershed. Nevertheless, the watershed simulation indicated that PPA restoration reduces the sediment and nutrients loading into the river. Thus, it is possible to conclude that tropical forest plays a fundamental role in the water resources conservation, reducing impacts of human activities in watersheds and the watershed management with forest restoration strategies for the entire watershed is critical for the maintenance of water quality to water supply, despite the importance of the riparian zone. / As florestas tropicais estão sob constante ameaça devido ao processo de desmatamento e fragmentação florestal impulsionado pelo crescimento das atividades econômicas, em especial, a agricultura. A substituição de áreas florestadas por outros usos do solo pode causar impactos severos na qualidade da água de rios, alterando suas características físicas, químicas e biológicas. A Mata Atlântica, em especial, teve sua cobertura original reduzida a cerca de 11%, sendo que a expansão de terras cultiváveis e urbanização ainda ameaçam esse importante ecossistema e os serviços ecossistêmicos prestados por ele. Nesse sentido, este estudo propôs investigar a relação da cobertura florestal com a qualidade da água de microbacias agrícolas tropicais. Para tanto, foram selecionadas seis microbacias experimentais com diferentes porcentagens de cobertura florestal na bacia do rio Sarapuí, Estado de São Paulo, Brasil, onde foram feitas coletas de amostras de água por um ano hidrológico para a obtenção de parâmetros que representassem alterações na água induzidas por atividades antrópicas. Inicialmente as microbacias foram classificadas em \"florestadas\" e \"degradadas\", e modelos estatísticos multivariados foram aplicados para identificar diferenças entre os grupos. Em um segundo momento comparou-se a relação do uso e cobertura do solo na microbacia e na Área de Preservação Permanente (APP) com a qualidade da água utilizando-se modelos mistos e análise de redundância para identificar os principais fatores que influenciam a variabilidade da qualidade da água. Por último foi gerado um modelo hidrológico para simular o impacto da restauração da floresta ripária na qualidade da água da bacia do rio Sarapuí onde cada microbacia experimental desse estudo foi representada por uma sub-bacia do modelo. Os resultados mostram que as microbacias degradadas apresentam valores maiores de sólidos, turbidez, nutrientes e coliformes. Além disso, apresentam maior variabilidade temporal dos dados em relação às microbacias florestadas associada às alterações da vazão do rio. Em geral, a cobertura florestal foi relacionada à boa qualidade da água, enquanto que agricultura e ocupação urbana foram os usos do solo responsáveis pela degradação da qualidade da água. O uso pastagem apresentou impactos mistos, porém no geral não foi correlacionado à qualidade da água ruim. Os parâmetros de qualidade da água responderam de forma diferente quanto à influência dos padrões de uso e cobertura do solo na microbacia e na APP, porém, considerando-se todos parâmetros em conjunto, a qualidade da água é melhor explicada pela composição da paisagem da microbacia. Ainda assim, a simulação do modelo indicou que a restauração das APPs reduz a carga de sedimentos e nutrientes para o rio. Com isso, conclui-se que a floresta tropical tem papel fundamental na conservação dos recursos hídricos, reduzindo impactos das atividades humanas exercidas nas microbacias e que, apesar da importância das APPs na redução de poluentes para o rio, o manejo de bacias com estratégias de restauração florestal para toda a microbacia é extremamente importante para a manutenção da qualidade da água para abastecimento.

Paysages emblématiques des campagnes de l’Ouest, les bocages ont connu une série de transformations rapides et importantes ces quarante dernières années : érosion du linéaire de haies, changements des usages du sol, rationalisation et agrandissement du parcellaire, banalisation et massification des bâtiments agricoles, enfrichement des secteurs les plus difficiles à exploiter. L’ampleur des ajustements observés souligne le décalage entre ces formes paysagères héritées d’une longue histoire agraire, et l’évolution des systèmes agricoles qui contribuent à les produire.Si la transformation des paysages de bocage est généralement attribuée au tournant « productiviste » du modèle agricole français, les processus socio-techniques à l’origine de ces évolutions sont plus rarement explicités. L’objet de ce travail est d’évaluer plus spécifiquement la contribution de l’agrandissement des exploitations agricoles à la dynamique d’évolution des paysages bocagers de l’Ouest de la France.Ce travail de géographie s’appuie dans un premier temps sur une analyse statistique à l’échelle du grand Ouest de la France, visant à étudier l’effet des transformations foncières sur les structures spatiales agricoles (assolements, parcellaire, linéaires boisés…). Dans un second temps, les dynamiques paysagères et foncières de quatre espaces d’étude (Bessin, Bocage Virois, Sud Manche, Pays d’Auge), situés en domaine laitier et bocager mais présentant des configurations agricoles variées, ont été étudiées entre 2003 et 2016. Ce travail s’appuie notamment sur un dispositif méthodologique original, articulant au sein d’un système d’information géographique à échelle parcellaire (1) la construction d’un suivi à échelle spatio-temporelle fine des dynamiques paysagères (évolution du maillage bocager, de la trame parcellaire et de l’occupation du sol) et (2) la reconstitution de l’évolution de la mosaïque des parcellaires d’exploitations par appariement de plusieurs millésimes du registre parcellaire graphique. L’exploitation de cette base de données spatio-temporelle a permis de mieux comprendre le rôle de la transformation foncière des exploitations agricoles dans la dynamique des paysages bocagers. Enfin, une enquête de terrain a été réalisée auprès de 150 agriculteurs équitablement répartis dans les quatre espaces d’étude, afin d’appréhender les conséquences sociales, techniques et productives de l’agrandissement à l’échelle des exploitations agricoles, qui diffèrent singulièrement selon le type de trajectoire foncière suivie. / Symbolic landscapes of the countryside of the West of France, the bocage landscapes have undergone a series of transformations these last forty years : decrease in hedgerow density, land uses changes, plots extension, normalization and enlargement of farm buildings, spatial extension of wilderness… The intensity of landscape transformations highlights the contradiction between these landscape forms produced by a long agrarian history and the contemporary evolutions of farming systems. The transformation of hedgerow landscapes is generally attributed to the "productivist" turn of the French agricultural model. However, the socio-technical processes behind these changes are more rarely explained.The first purpose of this geography work is to study the effects of changing agricultural systems on agricultural spatial structures, based on a statistical analysis at the scale of the West of France. In a second step, the landscape and land dynamics of four study areas (Bessin, Bocage Virois, Sud Manche, Pays d'Auge), located in the dairy and bocage domain, have been studied between 2003 and 2016. This work is based on an original methodological device, set up in a geographical information system. This structuration of geographic information makes possible to (1) monitor the landscape dynamics (evolution of the hedgerow density, land cover and plot morphology changes) at a fine spatial and temporal scale and (2) to reconstruct the evolution of the mosaic of farm plots, by matching land-parcell identification systems across the time (2007, 2011, 2013). From this spatio-temporal database, we characterized the coevolution of landscape structures and farm territories across the time, in order to better understand the landscape consequences of farm enlargment.Finally, a field survey was carried out among 150 farmers equitably distributed in the four study areas, in order to apprehend the social, technical and productive consequences of the farms enlargment, which differ singularly according to the type of land trajectory followed.

[pt] A região do Médio São Francisco, no interior da Bahia, no trecho do rio entre os municípios de Bom Jesus da Lapa e Serra do Ramalho é uma região onde diferentes tipos de ocupação têm sido alocados, sendo, portanto, um recorte espacial com grande potencial para compreender como as diferentes relações entre a sociedade e a natureza podem impactar na diferenciação das paisagens, sobretudo na distribuição da cobertura vegetal. A forte presença de comunidade quilombolas vazanteira, assim como o assentamento da população atingida pela construção da barragem de Sobradinho no Projeto Especial de Colonização de Serra do Ramalho na década de 70 tornaram a região do médio São Francisco uma área de ação de diferentes práticas etnoambientais. Dessa forma, o presente estudo tem o objetivo de, a partir da utilização de geotecnologias, produzir uma análise do recorte espacial sob a ótica das mudanças de uso e cobertura do solo, de modo a comparar a trajetória a evolutiva das paisagens das comunidades quilombolas e o assentamento da população reassentada. As métricas das paisagens apontaram uma forte diferenciação do comportamento das distribuição da cobertura vegetal, variando momentos de tendencia de perdas e ganhos de área vegetal e na presença dos tipos de fitofisionomia, sobretudo uma grande distinção entre a intensidade dos processos nos territórios das comunidades tradicionais e assentamento de Serra do Ramalho, em relação ao seus arredores. / [en] The region of the Middle São Francisco, in the interior of Bahia, in the stretch of river between the municipalities of Bom Jesus da Lapa and Serra do Ramalho is a region where different types of occupation have been allocated, being, therefore, a spatial cut with great potential to understand how the different relationships between society and nature can impact the differentiation of landscapes, especially the distribution of vegetation cover. The strong presence of the vazanteiras quilombola community, as well as the settlement of the population affected by the construction of the Sobradinho dam in the Serra do Ramalho Special Colonization Project in the 70s, made the middle São Francisco region an area of action for different ethno-environmental practices. Thus, this study aims to, from the use of geotechnologies, produce an analysis of the spatial cut from the perspective of changes in land use and land cover, in order to compare the evolutionary trajectory of the landscapes of quilombola and the settlement of the resettled population. The change detection analysis was developed using images from the Landsat collection, using geotechnology tools to produce data on the distribution of vegetation cover in different spatial contexts and monitoring of temporal series. The landscape metrics showed a strong differentiation in the behavior of the distribution of vegetation cover, varying moments of trend of losses and gains of vegetation area and in the presence of types of phytophysiomy, especially a great distinction between the intensity of processes in the territories of traditional and settlement of Serra do Ramalho, in relation to its surroundings.

[pt] Este trabalho propõe a comparação entre os dados do TerraClass 2004 e o Censo Agropecuário 2006 para analisar o uso de um na ausência do outro, para compreender o uso e cobertura do solo pela agropecuária na área de estudo. Através dos dados de uso e cobertura do solo do TerraClass 2004 e do Censo Agropecuário 2006, foi feita uma análise das áreas de cada classe que se enquadram como atividade agropecuária e uma comparação dessas áreas nas duas classificações. A análise utilizou o Sistema de Informação Geográfica (SIG) com imagens de satélite Landsat/TM 5 para auxiliar na análise visual qualitativa das classes e obter respostas sobre o uso e ocupação do solo no município de Lábrea. Foram escolhidos 16 setores censitários sobre os quais se tinha dados de classes referentes a agropecuária, analisando e percebendo uma variação percentual considerável em relação as duas classificações. A metodologia de comparação serviu para verificar que os métodos de aquisição dos dados do TerraClass 2004 e do Censo Agropecuário 2006 apresentam diferenças consideráveis nos resultados. Foram encontradas na classificação do TerraClass, através da análise qualitativa utilizando a imagem de satélite, dúvidas quanto a algumas classes sem vegetação, mas que não foram classificadas como atividade agropecuária, como desflorestamento, e essas consideradas duvidosas. Por fim, o presente trabalho conclui que não é adequado utilizar os dados do TerraClass na ausência do Censo Agropecuário, ou vice-versa, tendo em vista a disparidade encontrada em alguns dos setores censitários analisados. Sugere-se para trabalhos futuros um estudo específico para saber as causas das áreas desmatadas das classes consideradas duvidosas. / [en] This work proposes comparing data provided by 2004 s TerraClass and 2006 s Agribusiness Census, analyzing the validity of using one absent the other to comprehend the land cover in relation to said business within the studied area. The areas of the classes related to agribusiness were compared through the land cover reported in each classification. This analysis took place in a GIS environment with the use of Landsat/TM 5 to aid in the visual qualitative comparison of the data. The region of interest was the municipality of the Labrea district in the southern region of the Amazonas state. Sixteen census sector that showed agribusiness information were chose for the comparison of the percentages of area attributed to that business type. The variation of such areas was noteworthy and it was deemed that one should not use the two sources compared interchangeably as the information does not match. Moreover, some classes of the TerraClass classification stood out and regarded as uncertain – such as generic deflorestation and not forest – as, knowing the regions historical occupation and recent expansion of agribusiness, one would suspect that those are indeed related to the agents studied in this work.

Land surfaces have changed as a result of human and natural processes, such asdeforestation, urbanization, desertification and natural disasters like wildfires. Land use and landcover change impacts local and regional climates through various bio geophysical processes acrossmany time scales. More realistic representation of land surface parameters within the land surfacemodels are essential to for climate models to accurately simulate the effects of past, current andfuture land surface processes. In this study, we evaluated the sensitivity and accuracy of theWeather Research and Forecasting (WRF) model though the default MODIS land cover data andannually updated land cover data over southeast of United States. Findings of this study indicatedthat the land surface fluxes, and moisture simulations are more sensitive to the surfacecharacteristics over the southeast US. Consequently, we evaluated the WRF temperature andprecipitation simulations with more accurate observations of land surface parameters over thestudy area. We evaluate the model performance for the default and updated land cover simulationsagainst observational datasets. Results of the study showed that updating land cover resulted insubstantial variations in surface heat fluxes and moisture balances. Despite updated land use andland cover data provided more representative land surface characteristics, the WRF simulated 2- m temperature and precipitation did not improved due to use of updated land cover data. Further,we conducted machine learning experiments to post-process the Noah-MP land surface modelsimulations to determine if post processing the model outputs can improve the land surfaceparameters. The results indicate that the Noah-MP simulations using machine learning remarkablyimproved simulation accuracy and gradient boosting, and random forest model had smaller meanerror bias values and larger coefficient of determination over the majority of stations. Moreover,the findings of the current study showed that the accuracy of surface heat flux simulations byNoah-MP are influenced by land cover and vegetation type.

<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>

Orientador: Thiago Sanna Freire Silva / Resumo: As paisagens são a expressão da interação dinâmica entre processos naturais e atividades humanas. A região do Litoral Norte do Estado de São Paulo apresenta uma grande diversidade de fitofisionomias do bioma Mata Atlântica, e um rico patrimônio material e imaterial, em função da histórica interação do homem com a natureza. São inúmeros os vetores que agem simultaneamente sobre essa paisagem, resultando em efeitos cumulativos que transformam sua multifuncionalidade e multidimensionalidade. Este estudo objetivou a compreensão dos vetores de mudanças na paisagem do Litoral Norte do Estado de São Paulo. A transformação histórica da paisagem na área de estudo foi investigada buscando compreender a modificações dos cenários paisagísticos na sua integridade desde o início da colonização europeia na região de estudo. Através desta revisão histórica, demonstramos que a política econômica impulsionou investimentos em instalações tecnológicas e de acesso a região, que influenciaram no aumento das taxas de crescimento populacional, resultando num rápido crescimento das áreas urbanas após meados do século XX. O segundo capítulo quantificou as mudanças físicas da paisagem, através de séries históricas de imagens da série de satélites Landsat, utilizando o algoritmo Random Forests para classificação supervisionada do uso e cobertura da terra. Pudemos então, demonstrar que a região apresenta tendência a uma dicotomia no uso da terra, entre o uso urbano e a conservação ambiental. Entre 1985 e... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Landscapes are an expression of the dynamic interaction between natural environments and human activities. The Northern Coast of São Paulo State has a high diversity of Atlantic Forest vegetation types, and the Serra do Mar mountain range has a rich material and immaterial heritage due to ancient human-nature interactions. There are several different driving forces of change acting together over these landscapes, resulting in a cumulative effect over time. Our study sought to understand the causes and consequences of landscape change in the Northern Coast of São Paulo state, from 1985 to present. We described the land use history and landscape changes since the Europeans arrived in the region, during the XVI century. We identified that national economic policies and interests have led to investment in improved access and technological development, which in turn influenced migration to the region and resulted in fast urban expansion. In the second chapter, we have shown that land use change in the Northern Coast of São Paulo poses a dichotomy between two main land cover change trajectories over 30 years: forest persistence and fast urban growth. We found only 100 km² (8%) of forest disturbance within the State Parks, while dense urban settlements grew 167% outside the park, replacing mainly rural land uses. To identify and understand the driving forces of change in the region, we used Partial Least Squares - Path Modelling to model the relation between driving forces and lands... (Complete abstract click electronic access below) / Doutor

Le paludisme est un des maladies vectorielles les plus communes qui est situé principalement dans les régions tropicales. La zone étudiée est la région transfrontière Guyane française-Brésil. Le niveau et la dynamique intra-annuelle de la transmission y sont variables, avec un taux d’incidence qui est relativement élevé dans l’Amérique du Sud. Les facteurs environnementaux, en particulier l'occupation et l'usage du sol, influent significativement sur la présence, la densité et la distribution spatiale des moustiques du genre Anophèles, vecteurs de la maladie. Les données sur l'environnement, la population et les systèmes de santé sont rarement comparables de part et d’autre de la frontière Guyane-Brésil, excluant une vision bilatérale homogène. La télédétection permet de caractériser spatialement l’environnement de manière quasi continue et complète. L’objectif de ce travail est de caractériser par télédétection des milieux favorables au développement des vecteurs et les interactions hommes-vecteurs pour la zone transfrontalière Guyane-Brésil. Un indicateur spatialisé d’aléa de transmission du paludisme a été développé à l’échelle locale. Il permet de spatialiser la contribution de l'interaction entre milieux forestiers et non-forestiers sur la transmission du paludisme. Ce modèle a été mis en œuvre à l’échelle de la région amazonienne. Cet indice permet de quantifier et d’expliquer l’influence du paysage dans les interrelations homme - vecteurs adultes. L’identification des gîtes larvaires potentiels a été testée à une échelle régionale, à partir de la fusion d’images satellites optiques et radar, afin de mettre en évidence la distribution spatiale de zones humides pérennes et de grandes tailles (lacs, rivières, étangs, etc.) et les interfaces avec les milieux urbaines et forestiers. La distribution et la densité des vecteurs sont affectées par les propriétés physiques et chimiques des gîtes larvaires potentiels qui sont liées à la typologie des sols. Un modèle conceptuel de l’évaluation des sols adapté à la zone amazonienne présente que les caractéristiques géomorphologiques (altitude, courbure, etc.) sont indicateurs de l’évolution des sols. Une typologie des sols a été réalisée à l’échelle régionale à partir de données altimétriques et de ce modèle conceptuel. Les méthodologies, les cartes d’occupation et d’usage du sol, les cartes d’aléa du paludisme mises en place dans le cadre de cette thèse seront intégrés à l’Observatoire transfrontalier (Guyane-Brésil) qui est en cours de création. Ce travail de thèse contribue ainsi à l’exploitation des nouvelles connaissances sur le mécanisme de transmission du paludisme qui peuvent être utilisées pour définir les nouvelles stratégies de prévention aux échelles locale et régionale. / Malaria remains one of the most common vector-borne diseases what is predominantly located in the tropics. The study area is the cross-border area between French Guiana and Brazil where the level and intra-annuel dynamic of malaria transmission are variable, with the incidence rates which are relatively high in South America. The environmental risk factors, in particular, land use and land cover, significantly influence the presence, density and spatial distribution of disease vectors, Anopheles mosquitoes. Environmental information, population data and health systems database are rarely comparable on both sides of the Guyana-Brazil border which exclude the homogeneous and bilateral vision. Remote sensing permits to spatially characterize the environment on both sides of the border in an almost continuous and complete manner. The objective of this study is to characterize the favorable environment for the development of vectors and the vector-human interaction in the cross-border area between French Guiana and Brazil using remote sensing. A spatial landscape-based hazard index of malaria transmission was developed at the local scale. Such index allows spatializing the contribution of interaction between forest and non-forest areas on malaria transmission which was then implemented in the entire Amazon region. It quantifies and explains the influence of landscape on the interaction between human population and adult vectors. The identification of potential breeding sites of vectors was tested on a regional scale using the optical and SAR fusion for highlighting the spatial distribution of perennial and large wetlands (lakes, rivers, ponds etc.) and the interfaces with urban and forest environments. The distribution of vectors’ density is affected by physical and chemical properties of potential breeding sites which are related to soil typology. A conceptual model of soil evolution adapted to the Amazon region presents that geomorphological characteristics (altitude, curvature, etc.) are indicators of soil evolution. A soil classification was realized at the regional scale using altimetry data and the conceptual model. The methods, land use and land cover and malaria hazard maps established in this thesis will be integrated in the Observatory Sentinel of cross-border which is being built. This study also contributes to the exploitation of new knowledge about malaria transmission mechanism which can be used to define novel prevention strategies at the local and regional scales.

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. 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. 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).

Since 1971, a number of flood frequency models have been developed for river basins in Malawi for use in the design of hydraulic structures, but the varied nature of their results have most often given a dilemma to the design engineer due to differences in magnitudes of calculated floods for given return periods. All the known methods for flood frequency analysis developed in country so far have not used a homogeneity test for the river basins from which the hydrological data has been obtained. This study was thus conducted with a view to resolving this problem and hence improve the design of hydraulic structures such as culverts, bridges, water intake points for irrigation schemes, and flood protection dykes. In light of the above, during the course of this study the applicability of existing methods in the design of hydraulic structures was assessed. Also, the study investigated how land use and land cover change influence the frequency and magnitude of floods in the study area, and how their deleterious impacts on the socio-economic and natural environment in the river basins could be mitigated / Environmental Sciences / M. Sc. (Environmental Management)