Dissertationen zum Thema „Hydrological change“

Most documented investigations of the effects of land-use change on hydrological systems have considered the modification of forest areas. In this thesis, a headwater area in the North York Moors is used to examine the consequences of maintaining a land management regime which has received comparatively little observation in this context: controlled heather burning (muirburn). The effects of coniferous afforestation are also evaluated for selected variables. Particular attention is given to the responses of soil, moisture and evapotranspiration and the relationship between these two components.Simulated soil moisture deficits derived from empirical models are tested against measured values. Predictions based on Penman-Monteith evapotranspiration and 'layer' moisture deficits, along with an optimised soil-drying parameter, were found to simulate observed conditions most closely. A land-use change from open heather moorland to burnt ground promoted reductions both in evapotranspiration levels, especially at potential demando and in moisture deficits. In contrast, following afforestation, deficits were maintained or enhanced throughout the year, with higher moisture losses to interception than found under heather, due to the higher aerodynamic resistance of the latter. Predictions of actual evapotranspiration, determined from soil moisture models, were generally found to be reliable estimates of those 'observed' from the moorland water balance.Antecedent catchment conditions and storm characteristics were used in analysis of runoff distribution over time, quantified in terms of 'unit hydrographs' and linear regression models. Land-use effects were manifested most significantly in a doubling of hydrograph peak discharge following muirburn, the lower measured soil moisture deficits under a burnt catchment rendering more water available for storm runoff. A secondary, underlying control, that of a slower response from a wet catchment, lent 'support to evidence for the existence of variable source areas.

Anthropogenic emissions of greenhouse gases and aerosols have led to climate change including changes in surface temperature and precipitation. The surface temperature response is better understood than the precipitation response as a result of observed data availability and the complexity of the physics governing hydrological cycle changes. The complex general climate models (GeMs) are computationally demanding and include many physical processes that contribute to the changing water cycle. It remains necessary to understand the main drivers of this change. In this thesis, the main aim is to understand the water cycle changes by examining the degree to which simple models can simulate global-average results emerging from GeMs. For this purpose, a simple atmospheric energy budget model is used to calculate the global mean precipitation changes for the historical period and future scenarios. The results are then compared with GeMs to understand the physical processes affecting the global precipitation changes. The original form of the simple atmospheric energy budget model does not take into account many different factors included in GeMs, such as regional temperature and precipitation changes, fast surface sensible heat flux changes, fast precipitation response of volcanic aerosols and inter-annual variability. This work examines whether it is possible to extend the simple model to include some of these factors or compare the idealised experiments with the results of complex models (Wu et al. 2010). The simple model does well in producing the total global precipitation anomalies compared with GeMs multi-model mean consistent with earlier studies. The results of the simple model for individual GeMs are in less good agreement and different reasons for this disagreement have been investigated. Substituting the temperature changes from each GeM and also normalising the radiative forcings of simple model to the adjusted GeM RFs lead to an increase in compatibility between the simple model and GeMs, indicating that the main differences are related to the temperature equation and RFs. Adding the fast response of volcanic aerosols also increased the correlation between the simple model and GeMs particularly in volcanic years. Using new results from (Precipitation Driver Response Model Intercomparison Project) PDRMIP, the effect of fast surface sensible heat changes has been investigated which shows a considerable contribution to atmospheric energy budget changes particularly for aerosols. The simple model has been modified by adding the fast sensible heat changes which leads to a small improvement in the simple model; however it is not possible to be certain how robust this improvement is. More data and more work is still required but generally it is concluded that the simple model performs well compared with complex models.

During a three year field study (1997-2000) vegetation assemblages, collective vegetation variables, traits of dominant populations and hydrological and hydrochemical variables were repeat-sampled within seven wetland sites across Scotland and northern England. These ranged from the Irish Marshes, Inverness-shire in the north, to Tarn Moss, Cumbria at the southern extreme. Sampling was conducted at a total of fifty-six permanent sample stations located along a total of eleven transects. Vegetation groupings were defined using multivariate analyses, and were classified as various fen, mire, and swamp NVC community types. The various groups were characterised by the values for the range of variables measured, and significant differences were seen between a number of these variables for different groupings. In addition, certain separate groupings with the same community classification were also seen to have significant variations between them in terms of trophic status, and canopy height and biomass values. Collective vegetation variables and dominant population trait values were successfully predicted from physical and chemical variables measured within the groundwater and substrate during 1999. A number of specific models incorporating relatively large numbers of predictor variables were proposed alongside more general models incorporating fewer predictor variables. The greatest predictive power with R2 = 0.67 (p<0.001) for a model predicting stem density (m-2). Conversely, vegetation variables proved useful for predicting characteristics of the groundwater environment, for which specific and general models were against proposed. In this instance, the greatest predictive power was R2 = 0.79 (p<0.001) for a model predicting minimum water table level (i.e. maximum level of drawdown). The models were tested using data collected during 2000 from repeat sites and independent sites. Whilst some of the variables were predicted within noisy limits, predicted values generally corresponded well to observed values.

In order to effectively manage river basin systems, a full understanding of the effects of land use change on hydrological processes, as well as knowledge on spatial heterogeneity of surface runoff with associated catchment characteristics, is required. This thesis employed the SWAT2009 model and SUFI-2 tool to understand the hydrological response to land use change in the Daning River catchment, Three Gorges Reservoir area, China. Firstly, appropriate landscape representations for the SWAT-based hydrological modelling were examined. DEM spatial resolution, catchment delineation scale and HRU definition were identified so that the inputs uncertainty could be reduced to a minimal level. Secondly, a consistent underestimation of discharge using station-based climatic records disclosed there was insufficient precipitation due to the location of the rain gauge at relatively low altitude. Considering the orographic effects on precipitation, Daning hydrological models were well calibrated and validated with the sparse climate observations. The model prediction uncertainty was also quantified. Thirdly, using the calibrated hydrological models of the Daning River catchment, this study quantified the effects of land use change (1990 and 2004) on the hydrological processes in the whole basin and sub-catchment levels. In 1982-1993, the change of land use pattern from 1990 to 2004 resulted in an increase of surface runoff, whereas, in 1996-2007 reverting the land use from 2004 to 1990 caused a slight decrease of river flows. Increased forest cover decreased surface runoff at the sub-catchment level. A concurrent increase of agricultural land, which brought about more surface runoff, weakened the forest‘s ecological function of water retention at the catchment scale. This thesis highlights that the strategy of land use exploration for human use along with the afforestation is not always effective in ecological protection. With the changing land use in future, composition of forests and agricultural land is a significant element being considered.

Climate models have anticipated higher future extreme precipitations and streamflows for various regions. Urban stormwater facilities are vulnerable to these changes as the design assumes stationarity. However, recent climate change studies have argued about the existence of non-stationarity of the climate. Distribution method adopted on extreme precipitation varies spatially and may not always follow same distribution method. In this research, two different natural extremities were analyzed for two separate study areas. First, the future design storm depth based on the stationarity of climate and GEV distribution method was examined with non-stationarity and best fit distribution. Second, future design flood was analyzed and routed on a river to estimate the future flooding. Climate models from North American Regional Climate Change Assessment Program (NARCCAP) and Coupled Model Intercomparison Project phase 5 (CMIP5) were fitted to 27 different distribution using Chi-square and Kolmogorov Smirnov goodness of fit. The best fit distribution method was used to calculate design storm depth as well as design flood. Climate change scenarios were adopted as delta change factor, a downscaling approach to transfer historical design value to the climate adopted future design value. Most of the delta change factor calculated were higher than one, representing strong climate change impact on future. HEC-HMS and HEC-RAS models were used to simulate the stormwater infrastructures and river flow. The result shows an adverse effect on stormwater infrastructure in the future. The research highlights the importance of available climate information and suggests a possible approach for climate change adaptation on stormwater design practice.

Current global population growth and economic development accelerates the land cover conversion in many parts of the world and compromises the natural environment. However, the impacts of this land cover change on the hydrologic cycle at local to regional scales are poorly understood. The thesis presented here investigates the hydrologic implications of land use conversion in two different settings using two different approaches. The first study focuses in Southeast Asia and the expansion of rubber monocultures in a middle-sized basin. Field measurements suggest rubber has distinct dynamics compared to the area's native vegetation, depleting and exhausting the local water balance more than native vegetation. A phenology based evapotranspiration function is developed and used in a hillslope based hydrologic model to predict the implications of rubber expansion at a basin scale. The second study is centered in the semi-arid southwestern United States. This study challenges the traditional assumption that deforestation increases water yield at regional scales. Observations of water yield in basins affected by a regional piñon pine die-off show a decline in water yield during several years after die-off. These results suggest an increase in landscape sensitivity to vegetation disruption in semi-arid ecosystems as scale increases. Consequences of both studies have important implications for land and water managers in these different ecosystems.

The impact of anthropogenic activities on environment, especially the effect of land-use and climate changes was investigated in a series of studies. A comprehensive study of 16 research sites in different parts of Sweden was evaluated by using one dimensional hydrological model (CoupModel) to represent water and heat dynamics in layered soil profile covered with vegetation. Simulations are based on daily values and the results are representatives of variations in daily values and changes over years. The models accuracies controlled by measured run-off and snow depth values. However, there are uncertainties in both input data and simulated parameters. The interaction between run-off and snow depth were obtained when the models constrained by both run-off and snow depth. Parameters values variations and models performances changes in different time domains indicate the changes in land-use and climate over time and the model ability to handle these changes respectively. The strong interaction between meteorological stations density and models performances were indicated by comparing results with interpolation radius used for input data preparation.

Thesis (Ph. D.)--University of Adelaide, Dept. of Geography, 1997.
"Conducted as a cross-institutional student between the University of Adelaide and the Australian National Universiity." Includes bibliographical references.

Water resources, in terms of quantity and quality, are significantly influenced by environmental changes, especially by climate and land use changes. The main objective of the present study is to project climate change impacts on the seasonal dynamics of water fluxes, spatial changes in water balance components as well as the future flood and low flow conditions in Germany. This study is based on the modeling results of the process-based eco-hydrological model SWIM (Soil and Water Integrated Model) driven by various regional climate scenarios on one hand. On the other hand, it is supported by statistical analysis on long-term trends of observed and simulated time series. In addition, this study evaluates the impacts of potential land use changes on water quality in terms of NO3-N load in selected sub-regions of the Elbe basin. In the context of climate change, the actual evapotransipration is likely to increase in most parts of Germany, while total runoff generation may decrease in south and east regions in the scenario period 2051-2060. Water discharge in all six studied large rivers (Ems, Weser, Saale, Danube, Main and Neckar) would be 8 – 30% lower in summer and autumn compared to the reference period (1961 – 1990), and the strongest decline is expected for the Saale, Danube and Neckar. The 50-year low flow is likely to occur more frequently in western, southern and central Germany after 2061 as suggested by more than 80% of the model runs. The current low flow period (from August to September) may be extended until the late autumn at the end of this century. Higher winter flow is expected in all of these rivers, and the increase is most significant for the Ems (about 18%). No general pattern of changes in flood directions can be concluded according to the results driven by different RCMs, emission scenarios and multi-realizations. An optimal agricultural land use and management are essential for the reduction in nutrient loads and improvement of water quality. In the Weiße Elster and Unstrut sub-basins (Elbe), an increase of 10% in the winter rape area can result in 12-19% more NO3-N load in rivers. In contrast, another energy plant, maize, has a moderate effect on the water environment. Mineral fertilizers have a much stronger effect on the NO3-N load than organic fertilizers. Cover crops, which play an important role in the reduction of nitrate losses from fields, should be maintained on cropland. The uncertainty in estimating future high flows and, in particular, extreme floods remain high due to different RCM structures, emission scenarios and multi-realizations. In contrast, the projection of low flows under warmer climate conditions appears to be more pronounced and consistent. The largest source of uncertainty related to NO3-N modelling originates from the input data on the agricultural management.
Wasserressourcen werden in Quantität und Qualität von Veränderungen in der Umwelt, insbesondere von Änderungen des Klimas und der Landnutzung, in signifikantem Maße beeinflusst. In dieser Arbeit wurden die Auswirkungen von Klimavariabilität und Klimawandel auf die Wasserressourcen und Extremereignisse wie Hoch- und Niedrigwasser in Deutschland untersucht. Die Analyse erfolgte auf der einen Seite modellgestützt, wobei die Ergebnisse aus verschiedenen regionalen Klimamodellen durch ein ökohydrologisches Modell in Änderungen in den hydrologischen Prozessen transformiert wurden, zum anderen aber auch datengestützt, z.B. durch die statistische Interpretation von beobachteten und simulierten Zeitreihen. Zusätzlich wurden die Auswirkungen von Landnutzungsänderungen auf Umsatz von Stickstoff in der Landschaft und im Wasser untersucht, wobei dasselbe ökohydrologische Modell zum Einsatz kam. Im Rahmen des Klimawandels wird zur Mitte dieses Jahrhunderts die aktuelle Evapotranspiration in den meisten Teilen Deutschlands mit großer Wahrscheinlichkeit zunehmen. Die täglichen Abflussmengen der fünf größten Flussgebiete in Deutschland (Ems, Weser, Elbe, Obere Donau und Rhein) werden dieser Untersuchung zur Folge im Sommer und Herbst um 8%-30% geringer sein als in der Referenzperiode (1961-1990). 80% der Szenariensimulationen stimmen darin überein, dass die 50-jährigen Niedrigwasserereignisse zum Ende dieses Jahrhunderts mit großer Wahrscheinlichkeit häufiger in den westlichen, den südlichen und den zentralen Teilen Deutschlands auftreten werden. Die gegenwärtige Niedrigwasserperiode (August-September) könnte sich zudem dann bis in den späten Herbst ausweiten. Für alle Flüsse werden höhere Winterabflüsse erwartet, wobei diese Zunahme für die Ems am stärksten ausfällt (ca. 18%). Mit größerer Unsicherheit sind dagegen die Aussagen zur Entwicklung der Hochwasser behaftet. Aus den Ergebnissen, die durch unterschiedliche regionale Klimamodelle und Szenarien getrieben wurden, kann jedoch kein allgemeingültiges Muster für die Änderungen der 50-jährigen Hochwässer ausgemacht werden. Eine optimierte Landnutzung und ein optimiertes Landmanagement sind für die Reduzierung der NO3-Einträge in die Oberflächengewässer essentiell. In den Einzusgebieten der Weißen Elster und der Unstrut (Elbe) kann eine Zunahme von 10% in der Anbaufläche von Winterraps zu einer 12-19% höheren NO3 Fracht führen. Mais, eine weitere Energiepflanze, hat hingegen einen mäßigeren Effekt auf die Oberflächengewässer. Die Höhe der Gabe von mineralischen Düngern beeinflußt zudem in starkem Maße die Nitratbelastung von Flüssen. Zwischenfrüchte können den NO3-Austrag im Sommer zusätzlich erheblich verringern. Insgesamt bleibt die Unsicherheit in der Vorhersage von Spitzenabflüssen und im Besonderen von Extrem-Hochwässern als Folge unterschiedlicher regionaler Klimamodelle, Emissionsszenarien und Realisationen sehr hoch. Im Gegensatz dazu erscheinen die Projektionen zu den Niedrigwasserereignissen unter wärmeren Bedingungen sehr viel deutlicher und einheitlicher. Die größte Unsicherheit in der Modellierung von NO3 dagegen sind die Eingangsdaten z.B. für das lokale landwirtschaftliche Management.

Large explosive volcanic eruptions inject SO2 into the stratosphere where it is oxidised to sulphate aerosols which reflect sunlight. This causes a reduction in global temperature and precipitation lasting a few years. Here the robust features of this precipitation response are investigated, using superposed epoch analysis that combines results from multiple eruptions. The precipitation response is first analysed using the climate model HadCM3 compared to two gauge based land precipitation datasets. The analysis is then extended to a large suite of state-of-the art climate models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5). This is the first multi-model study focusing on the precipitation response to volcanoes. The large ensemble allows analysis of a short satellite based dataset which includes ocean coverage. Finally the response of major world rivers to eruptions is examined using historical records. Whilst previous studies focus on the response of just a few rivers or global discharge to single eruptions, here the response of 50 major world rivers is averaged across multiple eruptions. Results are applicable in predicting the precipitation response to future eruptions and to geoengineering schemes that seek to counteract global warming through reducing incoming solar radiation. The main model-simulated features of the precipitation response include a significant global drying over both land and ocean, which is dominated by the wet tropical regions, whilst the dry tropical ocean regions get significantly wetter following eruptions. Monsoon rainfall decreases, whilst in response to individual eruptions the Intertropical Convergence Zone shifts away from the hemisphere with the greater concentration of volcanic aerosols. The ocean precipitation response is longer lived than that over land and correlates with near surface air temperature, whilst the land response correlates with aerosol optical depth and a reduction in land-ocean temperature gradient Many of these modelled features are also seen in observational data, including the decrease in global mean and wet tropical regions precipitation over land and the increase of precipitation over dry tropical ocean regions, all of which are significant in the boreal cold season. The land precipitation response features were robust to choice of dataset. Removing the influence of the El Nino Southern Oscillation (ENSO) reduces the magnitude of the volcanic response, as several recent eruptions coincided with El Nino events. However, results generally remain significant after subtraction of ENSO, at least in the cold season. Over ocean, observed results only match model expectations in the cold season, whilst data are noisy in the warm season. Results are too noisy in both seasons to confirm whether a long ocean precipitation response occurs. Spatial patterns of precipitation response agree well between observational datasets, including a decrease in precipitation over most monsoon regions. A positive North Atlantic Oscillation-like precipitation response can be seen in all datasets in boreal winter, but this is not captured by the models. A detection analysis is performed that builds on previous detection studies by focusing specifically on the influence of volcanoes. The influence of volcanism on precipitation is detectable using all three observational datasets in boreal winter, including for the first time in a dataset with ocean coverage, and marginally detectable in summer. However, the models underestimate the size of the winter response, with the discrepancy originating in the wet tropics. Finally, the number of major rivers that undergo a significant change in discharge following eruptions is slightly higher than expected by chance, including decreased flow in the Amazon, Congo, Nile, Orange, Ob and Yenisey. This proportion increases when only large or less humanly influenced basins are considered. Results are clearer when neighbouring basins are combined that undergo the same sign of CMIP5 simulated precipitation response. In this way a significant reduction in flow is detected for northern South American, central African and less robustly for high-latitude Asian rivers, along with a significant increase for southern South American and SW North American rivers, as expected from the model simulated precipitation response.

Kyoto University (京都大学)
0048
新制・課程博士
博士(地球環境学)
甲第14885号
地環博第62号
新制||地環||12(附属図書館)
27307
UT51-2009-K681
京都大学大学院地球環境学舎地球環境学専攻
(主査)教授 松岡 譲, 教授 藤井 滋穂, 准教授 倉田 学児
学位規則第4条第1項該当

Changes in stratospheric ozone have previously been linked to Southern Hemisphere (SH) circulation changes. This study examines output from coupled climate models participating in the Climate Model Intercomparison Project 3 (CMIP3) for trends in precipitation and evaporation in the 20th and 21st centuries to assess whether stratospheric ozone influences the hydrological cycle and extreme precipitation in the SH extratropics, particularly during austral summer. Nineteen models are used, of which 10 incorporated ozone depletion (recovery) in the 20th (21st) century, whilst nine simply prescribed climatological ozone in both past and future climates. Trends in seasonal-mean precipitation are found to dominate overall changes in precipitation minus evaporation. For the 20th century, models with ozone depletion show a significant increase (decrease) in summer precipitation in high latitudes (mid-latitudes) compared to models without ozone depletion. In contrast, for the 21st century, models without ozone recovery show significantly larger changes in summer precipitation in these regions compared to models with ozone recovery. No significant differences, however, are found in the two sets of models during austral winter when stratospheric ozone is inactive. These results suggest that Antarctic ozone depletion and recovery significantly modulates hydrological climate change in the SH extratropics, in agreement with findings of previous studies. It is further found that stratospheric ozone primarily affects the frequency of light precipitation events (1–10 mm day^−1 ), indicating that an increase in mean precipitation over the Southern Ocean corresponds to an increase in the number of light precipitation days rather than extreme events. Implications of this finding to the SH surface climate and Southern Ocean circulation changes are discussed.
Les changements de concentration d'ozone stratosphérique ont été déjà reliés aux changements de la circulation dans l'hémisphère sud (HS). Ce travail examine les tendances dans la précipitation et l'évaporation pendant les 20ième et 21ième siècles, dans des simulations produites par des modèles climatique couplés qui participent au Climate Model Intercomparison Project 3 (CMIP3). Le but est de déterminer si l'ozone stratosphérique influence le cycle hydrologique et la précipitation extrême aux latitudes extra-tropicales de l'HS, pendant l'été austral en particulier. Dix-neuf modèles sont utilisés, où 10 d'entre eux incorporent l'épuisement (le rétablissement) d'ozone au 20ième (21ième) siècle et les neuf autres prescrivent simplement l'ozone climatologique (du 20ième siècle) pendant le passé et le futur. Les tendances des moyennes saisonnières de précipitation dominent les changements de l'évaporation moins la précipitation, alors c'est cette variable qui est examinée plus en détail. Pour le 20ième siècle, il y a une augmentation (diminution) de précipitation significative en été aux latitudes subarctique (latitudes moyennes) dans les modèles avec l'épuisement d'ozone comparé à ceux avec l'ozone climatologique. En contraste, pour le 21ième siècle, les changements de précipitation sont considérablement plus grands dans les modèles sans le rétablissement d'ozone que dans les modèles avec le rétablissement d`ozone. Pour l'hiver austral, quand l'ozone est inactif, il n'y a pas de différences entre les deux groupes de modèles. Ces résultats suggèrent que la diminution et rétablissement d'ozone dans l'Antarctique a des implications considérables pour le changement de climat hydrologique dans l'HS hors tropique, une conclusion atteinte dans d'autres travaux. En plus, on trouve que l'ozone stratosphérique affecte principalement la fréquence des évènements de précipitation légère (1–10 mm jour^-1), ce qui indique qu'une augmentation de la précipitation moyenne correspond à une augmentation du nombre de jours de précipitation légère, plutôt que d'évènements extrêmes. Les implications de ces conclusions pour le climat à la surface ainsi que pour les changements de circulation dans l'océan de l'HS sont discutés.

Many forested catchments in northern Pakistan have undergone land cover change during the last few decades. Extreme floods and extended droughts observed in these areas have lead to the question: How do human influences affect the water balance of a montane catchment. The underlying socio-political factors that have lead to the changes in forest cover and catchment hydrology are well documented, but there have been very few efforts to spatially correlate the cover changes with the catchment water balance. A deterministic model based on high resolution spatial and temporal data offers the ability to simulate the hydrological impacts of changes in land cover in a spatial context. In an attempt to assess the impacts of changing forest covers on individual hydrological processes, a GIS-based model Siran_HYDMAPS has been developed for the Siran Basin, Pakistan. This model integrates the spatial databases with the well-known hydrological process algorithms (e.g. Penman-Monteith evpotranspiration and Green-Ampt infiltration models). Spatially distributed static (topographic and soil) parameters for this model are extracted from a regional GIS developed specifically for the project. The dynamic (vegetation-related) parameters are estimated from the land cover maps, derived by digital processing of multi-resolution, multi-temporal Landsat MSS (5.3.1979) and TM (10.7.1989). Relative relief and shadowing in rugged terrain of the Himalayan foothills, that cause major problems in image processing, have been given particular attention. A rule-based approach was adopted to refine land cover maps with the integration of GIS for mapping the level II forest classes. Mapping of forest cover changes was carried out by post-classification change detection techniques. The Siran_HYDMAPS predicts a decrease in radiation balance and interception capacity, and an increase in evapotranspiration and catchment response of the Siran Basin, as a result of land cover changes. It was concluded that the water imbalances in this catchment, observed during the last two decades, were caused by the integrated effects of land cover changes and climatic factors.

Doutoramento em Ciências e Engenharia do Ambiente
As áreas peri-urbanas representam uma das formas mais importantes de desenvolvimento urbano. Aprofundar o conhecimento dos impactes destas áreas ao nível dos processos hidrológicos e a sua influência na qualidade da água superficial, constitui o principal objetivo deste estudo. O trabalho foi desenvolvido numa bacia hidrográfica Portuguesa, com características periurbanas (Ribeira dos Covões), sob a influência do clima Mediterrâneo. O estudo considera uma abordagem a várias escalas espaciais e temporais, envolvendo a realização de medições ao nível das propriedades do solo, ensaios em parcelas experimentais e a monitorização à escala da bacia hidrográfica e sub-bacias. Solos associados a diferentes usos apresentam distintas propriedades físicas que determinam a capacidades de infiltração de água, bem como os mecanismos de geração de escoamento superficial ao longo do ano. Durante períodos secos, a natureza hidrofóbica dos solos florestais e dos campos agrícolas abandonados, localizados na zona de calcários, promove uma baixa capacidade de infiltração da matriz do solo, induzindo a suscetibilidade para a geração de escoamento do tipo Hortoniano. Contudo, a reduzida repelência nas áreas agrícolas (em zona de arenitos) e as características hidrófilas dos solos urbanos promovem uma maior capacidade de infiltração, o que revela o potencial destes solos para a infiltração do escoamento gerado em áreas a montante. Por outro lado, ao longo do período húmido, a repelência do solo vai desaparecendo, o que promove o aumento da capacidade de infiltração, principalmente nas áreas florestais. No entanto, o aumento da humidade do solo restringe a capacidade de infiltração nos solos agrícolas e urbanos, favorecendo a geração de escoamento superficial por saturação, principalmente em locais de fundo de vale e em encostas calcárias de solos pouco profundos. As áreas florestais apresentam uma elevada capacidade de infiltração de água, mesmo quando a matriz do solo apresenta um elevado carácter hidrofóbico, promovida pela presença de macroporos. Todavia, densas plantações de eucaliptal são menos favoráveis à infiltração de água do que áreas de regeneração natural de eucalipto e zonas de carvalhos, devido à maior repelência do solo. O padrão climático, nomeadamente a precipitação, determina o regime hidrológico das bacias hidrográficas e a qualidade da água superficial. As características físicas da bacia, tais como a litologia, também afetam os processos hidrológicos, uma vez que determinam a permeabilidade dos solos e o regime hídrico das linhas de água ao longo do ano. Durante o verão, o escoamento de base representa uma componente relevante das linhas de água, mas o reduzido caudal promove uma baixa capacidade de diluição de poluentes, podendo colocar em causa a qualidade da água durante eventos de precipitação, principalmente devido a concentrações elevadas de carência química de oxigénio e nutrientes. Ao longo da época de chuvas, o aumento da conetividade hidrológica entre as fontes de escoamento superficial e de poluentes, origina maiores contribuições para as linhas de água. Elevadas cargas de poluentes, nomeadamente sólidos em suspensão, metais pesados e azoto, podem colocar em causa a qualidade da água superficial durante maiores eventos de precipitação. De um modo geral, a expansão das áreas urbanas, e particularmente das superfícies impermeáveis, promove o aumento dos coeficientes de escorrência e origina concentrações médias elevadas de alguns parâmetros que afetam a qualidade da água, tais como nitratos e carência química de oxigénio. No entanto, os impactes nos recursos hídricos são determinados pela localização das fontes dentro da bacia hidrográfica. Fontes de escoamento superficial e poluentes localizadas em posições mais elevadas das encostas podem ter um efeito negligenciável nas linhas de água, devido às oportunidades de infiltração e retenção superficial promovidas pela passagem ao longo da encosta. Por outro lado, fontes de escoamento e de poluentes localizadas nas imediações das linhas de água originam maiores impactes nos ecossistemas ribeirinhos. A presença de sistemas de drenagem de águas pluviais aumenta de forma eficiente a conetividade hidrológica dentro da bacia. Os agentes responsáveis pelo ordenamento do território e o planeamento urbano devem considerar a utilização de um mosaico paisagístico constituído por diversos usos do solo, de modo a maximizar a infiltração de água e limitar a conetividade hidrológica entre as fontes de escoamento e as linhas de água. A preservação de um regime hídrico mais aproximado ao de características naturais é importante para a minimização do risco de cheia e a degradação da qualidade da água.
Peri-urban areas represent one of the most important development forms. The aim of this study is to contribute for an improved knowledge about the impact of peri-urban areas on catchment hydrology and surface water quality. The research focus on a Portuguese peri-urban catchment (Ribeira dos Covões), under Mediterranean climate. The study is based on a spatio-temporal multi-scale approach, involving the measurement of soil properties, runoff plot experiments as well as catchment and subcatchments monitoring. Land-uses have distinct soil properties which provides different infiltration capacities and mechanisms for generating overland flow over the year. During the summer, the hydrophobic nature of woodland and abandoned agriculturallimestone fields exhibit low soil matrix infiltration capacity, being prone to induce infiltration-excess overland flow. However, wettable urban soils and low hydrophobic agricultural fields (overlaying sandstone) have greater matrix infiltration capacity, and can provide infiltration opportunities for uphill overland flow. On the other hand, throughout wet season, hydrophobicity switches off and matrix infiltration capacity increases under woodland soils. But increasing soil moisture limit the infiltration capacity of agricultural and urban land-uses, favouring saturation-excess overland flow, particularly in valley bottoms and hillslope shallow soils overlaying limestone. Even under widespread hydrophobic conditions in driest settings, woodland areas can provide high infiltration through macropores. Nevertheless, dense eucalypt plantations are less suitable than open eucalypt stands and woodland areas, due to most severe hydrophobicity. Climate pattern, and particularly rainfall, is the most important parameter affecting stream flow and surface water quality. Physical characteristics of the catchment, such as lithology are also important in determining soil permeability and the temporal stream flow regime. During the summer, base flow represents a larger percentage of the stream discharge, but the limited flow provide minor pollutants dilution during rainfall events, mainly chemical oxygen demand and nutrients, which may threaten water quality standards. Over the wet season, increasing hydrological connectivity of overland flow and pollutant sources provide greatest stream flow inputs. Enhanced pollutant loads, particularly of suspended sediments, heavy metals and nitrogen, can hinder surface water quality during wettest conditions. Generally, increasing urban land-use extent, and particularly impervious surfaces, leaded to enhanced runoff coefficients and high mean concentrations of few pollutants, specifically chemical oxygen demand and nitric oxide. However, impacts on stream flow are largely dependent on the source position across the landscape. Overland flow and pollutant sources located upslope may have a minor impact on riverine ecosystems, due to greater infiltration and surface retention opportunities provided by downslope areas. Contrary, source areas with greater proximity to the stream network would have major impacts. The presence of urban drainage system can efficiently favour flow connectivity, enhancing the impacts on aquatic ecosystems. Landscape managers and urban planners should employ a mosaic of different land-uses, in order to maximize infiltration and disrupt the flow connectivity between sources and stream network. The maintenance of a more natural hydrological regime would be important to minimize flood hazard and preserve water quality.

Anthropogenic activities including urbanization, rapid industrialization, deforestation and burning of fossil fuels are broadly agreed on as primary causes for ongoing climate change. Scientists agree that climate change over the next century will continue to impact water resources with serious implications including storm surge flooding and a sea level rise projected for North America. To date, the majority of climate change studies conducted across the globe have been for large-sized watersheds; more attention is required to assess the impact of climate change on smaller watersheds, which can help to better frame sustainable water management strategies. In the first of three studies described in this dissertation, trends in annual precipitation and air-temperature across the Commonwealth of Kentucky were evaluated using the non-parametric Mann-Kendall test considering meteorological time series data from 84 weather stations. Results indicated that while annual precipitation and mean annual temperature have been stable for most of Kentucky over the period 1950-2010, there is evidence of increases (averages of 4.1 mm/year increase in annual precipitation and 0.01 °C/year in mean annual temperature) along the borders of the Kentucky. Considered in its totality, available information indicates that climate change will occur – indeed, it is occurring – and while much of the state might not clearly indicate it at present, Kentucky will almost certainly not be exempt from its effects. Spatial analysis of the trend results indicated that eastern part of the state, which is characterized by relatively high elevations, has been experiencing decreasing trends in precipitation. In the second study, trends and variability of seven extreme precipitation indices (total precipitation on wet days, PRCPTOT; maximum length of dry and wet periods, CDD and CWD, respectively; number of days with precipitation depth ≥20 mm, R20mm; maximum five-day precipitation depth, RX5day; simple daily precipitation intensity, SDII; and standardized precipitation index, SPI were analyzed for the Kentucky River Basin for both baseline period of 1986-2015 and the late-century time frame of 2070-2099. For the baseline period, the majority of the indices demonstrated increasing trends; however, statistically significant trends were found for only ~11% of station-index combinations of the 16 weather stations considered. Projected magnitudes for PRCPTOT, CDD, CWD, RX5day and SPI, indices associated with the macroweather regime, demonstrated general consistency with trends previously identified and indicated modest increases in PRCPTOT and CWD, slight decreases in CDD, mixed results for RX5day, and increased non-drought years in the late century relative to the baseline period. The study’s findings indicate that future conditions might be characterized by more rainy days but fewer large rainfall events; this might lead to a scenario of increased average annual rainfall but, at the same time, increased water scarcity during times of maximum demand. In the third and final study, the potential impact of climate change on hydrologic processes and droughts over the Kentucky River basin was studied using the watershed model Soil and Water Assessment Tool (SWAT). The SWAT model was successfully calibrated and validated and then forced with forecasted precipitation and temperature outputs from a suite of CMIP5 global climate model (GCMs) corresponding to two different representative concentration pathways (RCP 4.5 and 8.5) for two time periods: 2036-2065 and 2070-2099, referred to as mid-century and late-century, respectively. Climate projections indicate that there will be modest increases in average annual precipitation and temperature in the future compared to the baseline (1976-2005) period. Monthly variations of water yield and surface runoff demonstrated an increasing trend in spring and autumn, while winter months are projected as having decreasing trends. In general, maximum drought length is expected to increase, while drought intensity might decrease under future climatic conditions. Hydrological droughts (reflective of water availability), however, are predicted to be less intense but more persistent than meteorological droughts (which are more reflective of only meteorological variables). Results of this study could be helpful for preparing any climate change adaptation plan to ensure sustainable water resources in the Kentucky River Basin.

Published Article
A functioning ecological system results in ecosystem goods and services which are of direct value to human beings. Ecosystem services are the conditions and processes which sustain and fulfill human life, and maintain biodiversity and the production of ecosystem goods. However, human actions affect ecological systems and the services they provide through various activities, such as land use, water use, pollution and climate change. Climate change is perhaps one of the most important sustainable development challenges that threaten to undo many of the development efforts being made to reach the targets set for the Millennium Development Goals. Understanding the provision of ecosystem services and how they change under different scenarios of climate and biophysical conditions could assist in bringing the issue of ecosystem services into decision making process. Similarly, the impacts of land use change on ecosystems and biodiversity have received considerable attention from ecologists and hydrologists alike. Land use change in a catchment can impact on water supply by altering hydrological processes, such as infiltration, groundwater recharge, base flow and direct runoff. In the past a variety of models were used for predicting land-use changes. Recently the focus has shifted away from using mathematically oriented models to agent-based modelling (ABM) approach to simulate land use scenarios. The agent-based perspective, with regard to land-use cover change, is centred on the general nature and rules of land-use decision making by individuals. A conceptual framework is being developed to investigate the possibility of incorporating the human dimension of land use decision and climate change model into a hydrological model in order to assess the impact of future land use scenario and climate change on the ecological system in general and water resources in particular.

In 2015-2016 Kwa-Zulu Natal (KZN) and other provinces in South Africa suffered from drought conditions. Drought can have negative impacts on the environment, society and the economy. Climate change is predicted to exacerbate extreme events such as droughts that would adversely affect already vulnerable regions such as KZN. The main aim of this study is to implement the attribution procedure, to determine if climate change has contributed to the 2015-2016 hydrological drought in selected KZN catchments. Methodology of the study followed a general framework of implementation of hydrological attribution experiments with climate data obtained from attribution simulations with HadAM3p global climate model. Prior to simulations in attribution mode, QSWAT model was set up for the study area and calibrated using SWAT-CUP and SUFI-2. Calibration results were poor but the model could be applied in the context of this study, under certain constraints. Results of attribution experiments revealed that for all 3 subbasins studied no increase of risk was observed and hence no influence of climate change on the 2015-2016 magnitude of drought for selected catchments was concluded by this study. These results are limited, as they are based on climate attribution experiments with only one climate model, rather than with a multi-model ensemble. Also, QSWAT model, in its implementation with generic climate data is of limited use in attribution (or hydrological) simulations as even after calibration the model performs poorly.

Tropical precipitation is linked through the moist static energy (MSE) budget to the global distribution of sea surface temperatures (SSTs), and large deviations from the present-day SST distribution have been inferred for past climates and projected for global warming. We use idealized SST perturbation experiments in multiple atmospheric general circulation models (AGCMs) to examine the hydrologic and energetic responses in the zonal mean and in the African Sahel to SST perturbations. We also use observational data to assess the prospects for emergent constraints on future rainfall in the Sahel.

The tropical zonal mean anomalous MSE fluxes in the NOAA Geophysical Fluid Dynamics Laboratory (GFDL) AM2.1 AGCM due to SST anomalies caused by either historical greenhouse gas or aerosol forcing primarily occur through the time-mean, zonal mean (Hadley) circulation. Away from the Intertropical Convergence Zone (ITCZ), this largely stems from altered efficiency of the Hadley circulation energy transport, i.e. the gross moist stability (GMS). A thermodynamic scaling-based estimate that relates GMS change to the local climatological moisture and temperature change relative to the ITCZ captures most of the qualitative GMS responses. It also yields a heuristic explanation for the well known correlation between low-latitude MSE fluxes and the ITCZ latitude.

Severe Sahelian drying with uniform SST warming in AM2.1 is eliminated when the default convective parameterization is replaced with an alternate. The drying is commensurate with MSE convergence due to suppressed ascent balanced by MSE divergence due to increased dry advection from the Sahara. These qualitative energetic responses to uniform warming are shared by five other GFDL models and ten CMIP5 models, although they do not translate into quantitative predictors of the Sahel rainfall response. Climatological values and interannual variability in observations and reanalyses suggest that drying in AM2.1 is exacerbated by an overly top-heavy ascent profile and positive feedbacks through cloud radiative properties. Simulations with patterned SST anomalies suggest a major role for mean SST variations in discrepancies among models and potentially in observed decadal variations of Sahelian precipitation.

Human interventions in the hydrologic cycle have intensified to the extent that water resources cannot be managed and understood in isolation from anthropogenic influences. New approaches are needed to understand the effects of humans on hydrology, especially in regions of the world with limited hydrologic records. This dissertation focuses on a case study of the Arkavathy watershed adjacent to Bangalore, India, which has been transformed by rapid urbanization, intensification of agriculture, and over-exploitation of water resources over the last 50 years. During this time, the disappearance of streamflow in the watershed was largely overlooked as Bangalore shifted from Arkavathy-sourced water supply to imported water and farmers from surface water to groundwater irrigation. With Bangalore continuing to expand its water footprint and local groundwater resources drying up, moving towards sustainable water resources management in the Arkavathy requires overcoming the general absence of local hydrological records to develop an understanding of the changing hydrology of the watershed. To this end, a multifaceted research approach is developed and applied to the Arkavathy watershed to identify the dominant hydrologic dynamics within the watershed and understand the conditions under which hydrologic change occurred. This research reveals a number of important findings. First, humans are the primary drivers of change in this watershed, as neither precipitation variability nor increases in temperature can explain the observed changes in hydrology. Second, hydrologic change within the watershed is spatially heterogeneous, with drying occurring in the northern part of the watershed and increased surface water availability downstream of Bangalore. Third, streamflow decline in the northern Arkavathy has most likely been caused by extensive groundwater depletion driven by groundwater irrigated agriculture. And finally, management strategies designed to reverse groundwater depletion by constructing check dams within the surface water network are unlikely to succeed on the scales pertinent to watershed management. In addition to understanding water resources within the Arkavathy, this work serves as a foundation for understanding the trajectory of water resources in the region. This research also presents an approach for investigating historical hydrologic change in a poorly monitored watershed, understanding human-water interactions, and supporting long-term predictions for sustainable water management.

Facing the urgency of taking actions to guarantee the water supply to Brazil's Capital, the project called IWAS/ÁguaDF aims to provide scientific knowledge for the development of an Integrated Water Resources Management (IWRM) concept. The project is organized in multiple working groups wherein climate is considered as one of the main drivers. The water supply system of Distrito Federal (DF) is mainly dependent on three major complexes: river basins, waste water and drinking water. Anthropogenic climate change has the potential to affect these water complexes in a number of ways such as by losing storage capacity due to erosion and sedimentation, through altered persistency of dry events and due to increasing water demand. As a contribution to the IWAS/ÁguaDF project, this study focuses on the development of climate change projections for hydrological impact assessments at local/regional scale. The development of proper climate information is a challenging task. The level of complexity corresponds directly to the issues that concern impact modellers as well as technical aspects such as available observational data, human and computational resources. The identification of the needs for water-related issues gives the foundation for deriving proper climate projections. Before making projections, it is necessary to assess the current climate conditions, or baseline climate. Despite a better understanding of the regional aspects of the climate and the ongoing changes, the baseline climate provides the foundation for calibrating and validating climate models and downscaling methods. The General Circulation Models (GCMs) are the most preferred tools in simulating the response of the climate system to anthropogenic activities, like increasing greenhouse gases and aerosol emissions. However, the climate information required for regional impact studies, such as water resources management in DF, is of a spatial scale much finer than that provided by GCMs and therefore often demands a downscaling procedure. Hydrological models are usually sensitive to the temporal variability of precipitation at scales that are not well represented by GCMs. Statistical downscaling methods have the potential to bridge the mismatch between GCMs and impact models by adding local variability that is consistent with both the large-scale signal and local observations. The tool used (i.e., Statistical DownScaling Model - SDSM) is described as a hybrid of regression-based and stochastic weather generator. The systematic calibration adopted provides the appropriated predictors and model parameterization. The validation procedure takes into account the metrics relevant to the requirements of hydrological studies. Moreover, the downscaling approach considers several climate models (i.e., 18 GCMs) and emission scenarios (i.e., SRES A1B, A2, B1) in order to sample the widest sources of uncertainties available. In spite of the elevated level of uncertainties in the magnitude of change, most of the downscaled projections agree with positive changes in temperature and precipitation for the period of 2046-2065 when compared to the reference period (i.e., 1980-1999). Large ensembles are preferable but are often associated with massive amount of data which have limited application in hydrological impact studies. An alternative is to identify subsets of projections that are most likely and projections that have lower likelihood but higher impact. A set of representative climate projections is suggested for hydrological impact assessments. Although high resolution information is preferable, it relies on limited assumptions inherent to observations and coarse-resolution projections and, therefore, its use alone is not recommended. The combination of the baseline climate with large- and local-scale projections achieved in this study provides a wide envelope of climate information for assessing the sensitivity of hydrological systems in DF. A better understanding of the vulnerability of hydrological systems through the application of multiple sources of climate information and appropriate sampling of known uncertainties is perhaps the best way to contribute to the development of robust adaptation strategies
Starkes Bevölkerungswachstum sowie Landnutzungs- und Klimawandel gefährden die Wasserversorgung der Metropolregion Brasília. Vor diesem Hintergrund soll das Projekt IWAS/ÁguaDF die wissenschaftlichen Grundlagen für ein Integriertes Wasserressourcen-Management (IWRM) im Distrito Federal (DF) erarbeiten. Das Projekt gliedert sich in drei klimasensitive Bereiche: Einzugsgebietsmanagement, Abwasseraufbereitung und Trinkwasserversorgung. Klimaänderungen können die Wasserversorgung im DF vielfältig beeinflussen, durch Veränderung der speicherbaren Wassermenge (Wasserdargebot, Speicherkapazität von Talsperren durch Sedimentation), der Dauer von Dürreperioden und des Wasserbedarfs (z.B. für Bewässerung). Klimaprojektionen für regionale hydrologische Impaktstudien stellen jedoch eine große Heraus-forderung dar. Ihre Komplexität richtet sich nach dem Bedarf des Impaktmodellierers und hängt zudem von technischen Voraussetzungen ab, wie der Verfügbarkeit von Beobachtungsdaten sowie von Personal- und Rechenressourcen. Die Ableitung geeigneter Maßnahmen für ein nachhaltiges Wasserressourcenmanagement im DF stellt hohe Ansprüche an die Qualität der zu entwickelnden Klimaprojektionen. Noch vor der Projektion müssen die gegenwärtigen klimatischen Bedingungen (Referenzklima) analysiert und bewertet werden. Die Analyse des Referenzklimas ermöglicht ein besseres Verständnis regionaler Unterschiede und aktueller Tendenzen und bildet die Grundlage für die Kalibrierung und Validierung von Klimamodellen und Downscaling-Methoden. Globale Klimamodelle (GCM) simulieren die Reaktion des Klimasystems auf anthropogene Treibhausgas- und Aerosolemissionen. Ihre räumliche Auflösung ist jedoch meist zu grob für regionale Klimaimpaktstudien. Zudem reagieren hydrologische Modelle meist sehr sensitiv auf zeitlich variable Niederschläge, welche in hoher zeitlicher Auflösung (Tagesschritte) ebenfalls nur unzureichend in GCM abgebildet werden. Statistische Downscaling-Verfahren können diese Inkohärenz zwischen GCM und Impaktmodellen reduzieren, indem sie das projizierte Klimasignal um lokale Variabilität (konsistent gegenüber den Beobachtungen) erweitern. Das in der vorliegenden Arbeit verwendete Tool, Statistical DownScaling Model - SDSM, vereint regressionsbasierte und stochastische Methoden der Wettergenerierung. Geeignete Prädiktoren und Modelparameter wurden durch systematische Kalibrierung bestimmt und anschließend validiert, wobei unter anderem auch hydrologisch relevante Gütekriterien verwendet wurden. Der gewählte Downscaling-Ansatz berücksichtigt zudem eine Vielzahl verschiedener Globalmodelle (18 GCM) und Emissionsszenarien (SRES A1B, A2 und B1) um die mit Klimaprojektionen verbundene hohe Unsicherheit möglichst breit abzudecken. Die Mehrheit der regionalen Projektionen weist auf eine Zunahme von Temperatur und Niederschlag hin (Zeitraum 2046 bis 2065 gegenüber Referenz-zeitraum, 1980 bis 1999), wenngleich die Stärke des Änderungssignals stark über das Ensemble variiert. Große Modellensemble sind zwar von Vorteil, sie sind jedoch auch mit einer erheblichen Datenmenge verbunden, welche für hydrologische Impaktstudien nur begrenzt nutzbar ist. Alternativ können einzelne „wahrscheinliche“ Projektionen verwendet werden sowie Projektionen, die weniger wahrscheinlich, aber mit einem starken Impakt verbunden sind. Ein solcher Satz repräsentativer Klimaprojektionen wurde für weitergehende Impaktstudien ausgewählt. Auch wenn in der Regel hochaufgelöste Klimaprojektionen angestrebt werden, ihr alleiniger Einsatz in Impaktstudien ist nicht zu empfehlen, aufgrund der vereinfachten Annahmen über die statistische Beziehung zwischen Beobachtungsdaten und den Modellergebnissen grob aufgelöster Globalmodelle. Der Vergleich des Referenzklimas mit großräumigen und lokalen Projektionen, wie er in dieser Arbeit durchgeführt wurde, liefert ein breites Spektrum an Klimainformationen zur Bewertung der Vulnerabilität hydrologischer Systeme im DF. Die Einbeziehung einer Vielzahl vorhandener Klimamodelle und die gezielte, den ermittelten Unsicherheitsbereich vollständig abdeckende Auswahl an Projektionen sollte die Entwicklung robuster Anpassungsstrategien bestmöglich unterstützen
Diante do desafio de garantir o abastecimento de água potável da capital federal do Brasil, o projeto denominado IWAS/ÁguaDF tem como objetivo prover conhecimento científico para o desenvolvimento de um conceito de Gestão Integrada dos Recursos Hídricos (PGIRH). Afim de atingir esta proposta, o projeto é organizado em multiplos grupos de trabalho entre os quais o clima é considerado um dos principais fatores de influência. O sistema de abastecimento de água do Distrito Federal (DF) depende praticamente de três complexos: bacias hidrográficas, águas residuais e água potável. Mudanças climáticas causadas por ações antropogênicas apresentam um enorme potencial de impacto a estes complexos, por exemplo através de alterações no regime de chuvas, perda de volume dos reservatórios por assoriamento e aumento na demanda de água. Como contribuição ao projeto IWAS/ÁguaDF, este estudo tem como foco o desenvolvimento de projeções de mudanças climáticas para estudo de impacto nos recursos hídricos na escala local/regional. O nível de complexidade corresponde diretamente às questões levantadas pelos modeladores de impacto, bem como aspecto técnicos como a disponibilidade de dados observados e recursos humanos e computacionais. A identificação das necessidades de questões relacionadas à água no DF dão a base para derivar projeções climáticas adequadas. Antes de qualquer projeção futura, é indispensável avaliar as condições atuais do clima, também chamado de linha de base do clima. Além de fornecer a compreenção dos aspectos regionais do clima e mudaças em curso, a linha de base provê dados para a calibração e validação de modelos globais de clima e técnicas de regionalização (downscaling). Os Modelos de Circulação Geral (GCM) são as ferramentas mais adotadas na simulação da resposta do sistema climático às atividades antropogênicas, tais como aumento de emissões de gases do efeito estufa e aerosóis. No entanto, a informação necessária para estudos regionais de impacto, tais como gestão de recursos hídricos, é de escala espacial mais refinada do que a resolução espacial fornecida pelos GCMs e, dessa forma, técnicas de regionalização são frequentemente demandadas. Modelos hidrológicos são geralmente sensitivos à variabilidade temporal de precipitação em escalas não representadas pelos modelos globais. Métodos estatísticos de ‘downscaling’ apresentam um potencial para auxiliar no descompasso entre GCMs e modelos de impacto através da adição de variabilidade local consistente com o sinal de larga escala e as observações locais. A ferramenta utilizada (Statistical DownScaling Model - SDSM) é descrita como um híbrido entre regressão linear e gerador de tempo estocástico. A calibração sistemática adotada fornece apropriados preditores e uma parameterização consistente. O procedimento de validação do modelo leva em conta as métricas relevantes aos requerimentos dos estudos hidrológicos. Ainda, a abordagem aqui utilizada considera diversos modelos globais (isto é, 18 GCMs) e cenários de emissões (isto é, SRES A1B, A2 e B1) afim de contemplar as mais abrangentes fontes de incertezas disponíveis. Embora o elevado nível de incertezas na magnitude das mudançãs de clima, a grande maioria das projeções regionalizadas concordam com o aumento de temperatura e precipiatação para o período de 2046-2065 quando comparado com o período de referência (isto é, 1980-1999). Grandes conjuntos de projeções são preferíveis, mas são frequentement associados com uma quantidade exorbitante de dados os quais são de aplicação limiatada nos estudos de impacto. Uma alternativa é identificar sub-conjuntos de projeções que são as mais prováveis e projeções que são menos prováveis, porém apresentam maior impacto. Embora altas resoluções são preferíveis, estas baseiam-se em hipóteses inerentes às observações e projeções de larga escala e, dessa forma, não é recomendável o seu uso sozinho. A combinação do clima de base com projeções de resoluções baixas e altas fornece um amplo envelope de imformações climáticas para avaliar a sensitividade dos sistemas hidrológicos no DF. Um compreendimento mais apurado da vunerabilidade dos sistemas hidrológicos através da aplicação de multiplas fontes de informação e apropriada abordagem das incertezas conhecidas é talvez a melhor maneira para contribuir para o desenvolvimento de estratégias robustas de adaptação

Abstract Although flow regime is a key element in determining the structure and function of lotic ecosystems, little is known about the variation of natural flow regimes and its relation to biological communities in highly seasonal northern boreal rivers. Temperature and precipitation patterns at northern latitudes are predicted to change drastically in the future causing severe effects on stream ecosystems. Interactions between climate change impacts and land use might further create unpredictable environmental stress. In this thesis, I first assessed the relationship of natural flow regimes of northern boreal rivers with taxonomic and functional structure of stream macroinvertebrates. Second, I combined hydrological, climate and biological models to study how climate change will alter northern flow and thermal regimes, how macroinvertebrates will respond to these changes and where these changes are going to be most pronounced. Third, I experimentally studied how different stream organisms are responding to flow change, sedimentation and their possible interaction. The role of hydrology in structuring macroinvertebrate assemblages was evident. Streams were predicted to lose much of the flow seasonality in the future, causing drastic changes that even exceeded the effect of future warming on macroinvertebrates. Especially communities within small seasonal streams were predicted to change, highlighting the importance of focusing conservation actions on these systems. Different organism groups exhibited highly variable responses to different stressors. For instance, aquatic fungi, which have been used less in climate change research, responded more strongly to flow change than traditionally used macroinvertebrates. The interactive effects of flow and sand were all antagonistic (i.e. less than the sum of the individual effects), which could be reassuring for management, although it means that both stressors may need to be removed to produce true ecological recovery. The results support the use of hydrological models in ecological studies for predicting current and future hydrological conditions at a site. However, as extreme events have been predicted to become more frequent, instead of modeling change in average conditions, future predictive models should be able to capture extreme fluctuations to gain more realistic view of climate change effects on stream ecosystems
Tiivistelmä Joen virtaamaolosuhteet ja niiden vaihtelu ovat tärkeimpiä jokiekosysteemien rakenteeseen ja toimintaan vaikuttavia tekijöitä. Tästä huolimatta pohjoisen havumetsävyöhykkeen jokien luonnollisia virtaamaolosuhteita ja niiden yhteyttä virtavesieliöihin on tutkittu vähän. Ilmastonmuutoksen on ennustettu aiheuttavan voimakkaita muutoksia pohjoisten alueiden ilman lämpötilassa ja sadannassa, ja nämä muutokset tulevat mitä todennäköisimmin aiheuttamaan vakavia seurauksia myös jokiekosysteemeissä. Ilmastonmuutoksen ympäristövaikutukset voivat lisäksi aiheuttaa jo olemassa olevien ihmistoiminnasta aiheutuvien ympäristövaikutusten kanssa haitallisia ja vaikeasti ennustettavia yhdysvaikutuksia. Väitöskirjassani arvioin ensin pohjoisten virtavesien luonnollisten virtaamaolosuhteiden suhdetta pohjaeläinyhteisöjen taksonomiseen ja toiminnalliseen rakenteeseen. Tämän jälkeen tarkastelin yhdistämällä erilaisia ilmastonmuutoksen skenaarioita hydrologisen ja biologisen mallin kanssa, miten ilmastonmuutos saattaa tulevaisuudessa vaikuttaa jokien virtaamaolosuhteisiin ja niissä eläviin pohjaeläinyhteisöihin. Lisäksi arvioin missä ja minkälaisissa jokityypeissä ilmastonmuutoksen vaikutukset tulevat esiin kaikkein voimakkaimmin. Lopuksi tutkin kokeellisesti, miten virtaamavaihtelu ja hienojakoinen sedimentti ja näiden mahdolliset yhdysvaikutukset vaikuttavat eri virtavesieliöihin. Tulokset osoittivat, että vuodenajasta riippuvat virtaamavaihtelut vähenevät ilmastonmuutoksen myötä, minkä seurauksena pohjaeläinyhteisöissä tapahtuu voimakkaita muutoksia. Erityisesti pienten jokien pohjaeläinyhteisöjen monimuotoisuus ja koostumus muuttuivat verrattaessa tämän päivän lajistoa tulevaisuuden ennustettuun lajistoon. Eri virtavesieliöryhmät vastasivat hyvin eri tavalla virtaamavaihtelun ja hiekoittumisen aiheuttamaan elinympäristön muutokseen. Esimerkiksi akvaattiset sienet, joita on aikaisemmin harvoin käytetty ilmastonmuutostutkimuksissa, vastasivat voimakkaammin virtaamamuutoksiin kuin tutkimuksissa perinteisesti käytetyt pohjaeläimet. Kaikki kokeessa havaitut yhdysvaikutukset olivat kuitenkin pienempiä kuin yksittäisten vaikutusten summa. Tulos on huojentava vesiensuojelun kannalta, mutta tarkoittaa toisaalta myös sitä, ettei yksittäisten ihmisvaikutusten poistaminen välttämättä takaa vesistön ekologisen tilan parantumista, jos elinympäristöön vaikuttaa yhtaikaisesti useampi tekijä. Väitöskirjani tulokset tukevat hydrologisten mallien hyödyntämistä ekologisessa tutkimuksessa. Ilmastonmuutoksen myötä eri ääri-ilmiöiden, kuten rankkasateiden, on ennustettu tulevan entistä yleisimmiksi. Ääri-ilmiöiden vaikutukset ekologisiin vasteisiin tunnetaan kuitenkin heikosti. Mallien kehittämisessä olisi tämän vuoksi jatkossa tärkeää keskittyä ääri-ilmiöihin ja niiden aiheuttamiin biologisiin muutoksiin, jotta voisimme nykyistä realistisemmin arvioida ilmastonmuutoksen vaikutuksia sisävesiekosysteemeissä

Northeastern Brazil is hydrologically characterized by recurrent droughts leading to a highly vulnerable natural water resource system. The region contains the Caatinga biome, a sparsely studied ecosystem, covering an area of approximately 800,000 km2. Reduced wateravailability is projected to take place in large regions of the globe, including Northeastern Brazil. Given the strong interactions between climate and vegetation, research has addressed climate change effects on natural and agricultural ecosystems. In this context, soil hydraulic properties are essential to assess soil water flow, and thus the ability of soil to supply water to plants at potential rates under different ranges of pressure head. Based on that, the aims of this thesis are: to increase insight in water balance components for the Caatinga biome, under current and future climate scenarios; and to assess the ability of soils in supplying water to plants by the further development of an existing matric flux potential approach, followed by its application to a group of soils from two Brazilian climatic zones (semi-arid and subhumid). Both for current and future climate scenarios, hydrological simulations were performed with SWAP model parameterized for a preserved Caatinga basin of 12 km2. The validation of the simulations was performed using a dataset of daily soil-water content measurements taken at 0.2 m depth in the period from 2004 to 2012. The soil water supplying capacity was evaluated through a multilayer matric flux potential approach, coupling the soil hydraulic properties, root length density and plant transpiration. Regarding the current climate conditions, the Caatinga biome returns 75% of the annual precipitation to the atmosphere, whereas the partitioning of total evapotranspiration into its components (transpiration, evaporation and interception) on annual basis accounts for 41%, 40% and 19%, respectively. Evapotranspiration and air temperature are most sensitive to soil moisture during the periods June-September and December-January. Concerning the future climate, transpiration was enhanced by 36%, soil evaporation and interception losses reduced by 16% and 34%, respectively. The amount of precipitation returned to the atmosphere was on average 98%. For both climate scenarios, the soil-plant-atmosphere fluxes seem to be controlled by the surface soil layer (0-0.2 m) which provides, on average, 80% of the total transpiration, suggesting that the Caatinga biome may become completely soil-water pulse dominated under scenarios of reduced water availability. The matric flux potential analysis revealed that soils from the semiarid zone were able to deliver water to plants at potential rates under a wider range of bulk soil pressure head (-36 to -148 m), whereas the soils from the wetter zone showed more hydraulic restriction with limiting soil water potential above -1.5 m. For the analyzed soils, only a negligible increase in available water results from decreasing the root water potential below -150 m, therefore, in order to adapt to water-limited conditions, plant species may invest in other adaptive strategies, rather than spending energy in structures that allow a reduction of the lower suction limit in their tissues.
O Nordeste do Brasil é hidrologicamente caracterizado por secas recorrentes, tornando os recursos hídricos naturais altamente vulneráveis. Nesta região está o bioma Caatinga, ocupando uma área de aproximadamente 800.000 km2. Cenários de déficit hídrico são projetados para grandes regiões do globo, incluindo o Nordeste brasileiro. Devido às interações entre clima e vegetação, várias pesquisas têm abordado os efeitos das mudanças climáticas sobre os ecossistemas naturais e agrícolas. Neste contexto, as propriedades hidráulicas do solo são essenciais para avaliar o movimento de água, e assim a capacidade de fornecimento de água às plantas. Com base nesta contextualização, os objetivos desta tese são: simular os componentes do balanço hídrico do bioma Caatinga para cenários climáticos atuais e futuros; e avaliar a capacidade de alguns solos em fornecer água às plantas a partir de uma abordagem de potencial de fluxo matricial. Para os cenários climáticos atuais e futuros, simulações hidrológicas foram realizadas com o modelo SWAP, parametrizado para uma microbacia de 12 km2, inserida em área de Caatinga preservada. A validação das simulações foi processada a partir de medidas diárias do conteúdo de água do solo na profundidade de 0,2 m no período de 2004 a 2012. A capacidade do solo em fornecer água às plantas foi avaliada através da atualização de uma função de potencial de fluxo matricial, que acopla as propriedades hidráulicas do solo, densidade de comprimento radicular e transpiração das plantas, aplicada a um grupo de solos da zona climática semiárida e sub-úmida. Como resultados principais destacam-se: nas condições climáticas atuais, o bioma Caatinga retorna 75% da precipitação anual para a atmosfera como evapotranspiração, particionada entre seus componentes (transpiração, evaporação e intercepção) em 41%, 40% e 19%, respectivamente. Evapotranspiração e temperatura do ar foram sensíveis à umidade do solo durante os períodos de junho-setembro e dezembro-janeiro. Em relação ao cenário climático futuro, a taxa de transpiração foi acrescida em 36%. A evaporação do solo e a interceptação foram reduzidas em 16% e 34%, respectivamente. A quantidade de precipitação devolvida para a atmosfera foi em média 98%. Para ambos os cenários climáticos, é sugerido que os fluxos de água no sistema solo-planta-atmosfera são controlados pela camada superior do solo (0-0,2 m), fornecendo, em média, 80% do total transpirado, indicando que, caso os cenários de disponibilidade hídrica reduzida se confirmem, o bioma Caatinga pode se tornar completamente dependente dos pulsos de água no solo. A partir do potencial de fluxo matricial limitante revelou-se que os solos da região semiárida são capazes de manter o fluxo de água às plantas em taxas potenciais em condições de solo seco (potencial matricial limitante variando de -36 a -148 m), enquanto que, os solos da região mais úmida indicaram severa restrição hidráulica, com potencial matricial limitante maior do que -1,5 m. Ainda para os solos analisados, a atribuição de potencial na superfície da raiz inferior a -150 m não ocasionou aumento de disponibilidade hídrica, indicando que valores menores que -150 m não implicam em uma estratégia viável para suportar baixa disponibilidade hídrica.

Rapidly rising levels of atmospheric greenhouse gases including carbon dioxide and methane since the industrial revolution have drawn scientific attention to the importance of the global carbon cycle to the climate (Cubasch et al., 2013). Tropical peatlands, the majority of which are located in the Indonesian region, are a major source of uncertainty in the carbon cycle as the relationships between carbon accumulation and hydrological changes remain poorly understood (Hergoualc’h & Verchot, 2011, Page et al., 2011). An important driver of carbon emissions in tropical peatlands is fire, which in the Indonesian region is strongly influenced on interannual timescales by the El Niño/Southern Oscillation (ENSO). However, it is not clear how ENSO and fire have varied at decadal to centennial scales over the past two millennia. This thesis explores long term tropical hydrological variability and ENSO-like climate change from palaeorecords and their interactions with fire. Using a wide range of instrumental, proxy and model datasets and a novel reconstruction method, two separate reconstructions of long-term ENSO-like climate change are produced based on precipitation and temperature data. These show no evidence of a difference between the ENSO-like behaviour of precipitation and temperature. There is limited evidence for a difference in long-term ENSO-like state between the Medieval Climate Anomaly and the Little Ice Age. Reconstructions of hydrological variability and biomass burning in the Indonesian region suggest that precipitation and fire have been positively correlated over the past 2,000 years, which is contrary to the modern-day relationship on ENSO timescales. This throws up questions of long-term versus short-term interactions and feedbacks between fire, climate and vegetation. It is likely that anthropogenic activity in the Indonesian region has significantly altered the stability of the fire regime. Further research combining proxy data, climate and fire models, and using more robust statistical analysis is necessary to untangle the natural and anthropogenic driving factors at different time resolutions.

Lake Tana Basin is of significant importance to Ethiopia concerning water resources aspects and the ecological balance of the area. The growing high demands in utilizing the high potentials of water resource of the Lake to its maximal limit, pictures a disturbing future for the Lake. The objective of this study was to assess the influence of topography, soil, land use and climatic varia-bility on the hydrological and hydrodynamic processes of the Lake Tana Basin. The physically based SWAT model was successfully calibrated and validated for flow and sediment yield. Se-quential uncertainty fitting (SUFI-2), parameter solution (ParaSol) and generalized likelihood un-certainty estimation (GLUE) calibration and uncertainty analysis methods were compared and used for the set-up of the SWAT model. There is a good agreement between the measured and simulated flows and sediment yields. SWAT and GIS based decision support system that uses multi-criteria evaluation (MCE) was used to identify the most vulnerable areas to soil erosion in the basin. The results indicated that 12 to 30.5% of the watershed is high erosion potential. Pro-jected changes in precipitation and temperature in the basin for two seasons were analyzed using outputs from fifteen global climate models (GCMs). A historical-modification procedure was used to downscale large scale outputs from GCM models to watershed-scale climate data. The results showed significant changes in streamflow and other hydrological parameters in the period between 2045-2100. SWAT was combined with a three dimensional hydrodynamic model, GEMSS to investigate the flow structure, stratification, the flushing time, lake water balance and finally the Lake‘s water level response to planned water removal. We have found an alarming and dramatic fall of the water levels in Lake Tana as response to the planned water withdrawal. The combination of the two models can be used as a decision support tools to better understand and manage land and water resources in watersheds and waterbodies. The study showed that the Lake Tana Basin may experience a negative change in water balance in the forthcoming decades due to climate change as well as over abstraction of water resources.
QC 20100720

A SWAT hydrological model is developed to evaluate the individual and combined impacts of urbanization and climate change on water quantity (discharge) and quality (N and P) of the watershed of Carp River in Ontario, Canada. Seven numerical experiments (scenarios) were developed to represent the different configurations of the watershed in terms of land use (either current or projected) and climate regime (current or future, observed or simulated). The reference period is 1990-2018, and the future period is 2021-2050. The 2017 land use was used to represent the reference period. The future land use is the projected 2050 land use obtained from the City of Ottawa. The future climate was obtained by downscaling the outputs of nine (9) Regional Climate Models (RCMs) under two Representative Concentration Pathways (RCPs): RCP4.5 and RCP 8.5. The developed scenarios are the following: • S0o (baseline scenario) corresponding to the current land use map and the observed climate regime on the reference period • S0m is similar to S0o except that RCM outputs are used instead of the observed climate on the reference period • S1 corresponds to the future land use and historical climate regime on the reference period. • S0M45/S0M85 corresponds to the current land use and the future climate regime under RCP4.5 (S0M45) and RCP8.5 (S0M85) • S1M45/S1M85 corresponds to the future land use map and future climate regime under the two RCPs. The changes or impacts on quantity and quality in each scenario were estimated by comparing the results with the baseline scenarios S0o/m (reference) at two levels: globally (at the main outlet) and locally (at the outlet of an upstream sub-watershed). For a consistency purpose, S0o is used when assessing land-use change scenario while S0m was the reference in climate change and combined effects scenario. This allowed the comparison to be consistent with the same climate data frame. The results showed that climate change is likely to be the most dominant factor affecting discharge and nitrogen, while urbanization will control the quantity of phosphorus. Unsurprisingly, the combined effect had a more significant impact on water quantity and quality. However, the impact is not additive, and the relationship is not linear. Compared with S0, the annual average discharge increased by 1.57%, 5.49%, 7.52%, 6.75%, and 9.34% in S1, S0M45, S0M85, S1M45, and S1M85, respectively. In comparison, the change for annual N load was estimated at -1.88%, 29.62%, 2.03%, 24.84%, and -1.20% respectively. Change in annual average P was respectively 26.49%, 1.07%, -4.49%, 23.81% and 19.15%. Local impact assessment indicates the impact in upstream sub-watersheds may differ from the main outlet's impact in terms of magnitude and direction of change. Therefore, only considering global change may lead to a wrong interpretation of the impacts over the watershed. It is, therefore, necessary to evaluate the impacts at the local level as well.

One of the biggest upcoming challenges to the international community is the problem of a changing climate. The earth’s surface temperature is rising and associated impacts on physical and biological systems are increasingly being observed. Science tells us that climate change will bring about gradual changes, such as sea level rise, and shifts of climate zones due to increased temperatures and changes in precipitation patterns. A changing climate affects the entire world but will strike hardest against the poorest as they are the ones most dependent on agriculture which is a sector that is very vulnerable to changes in temperature and precipitation patterns. One region that will be especially vulnerable and has experienced the problems of shifting climate zones before is the Sahel region that borders to the south end of the Sahara desert where problems of desertification have occurred before. This region will in large extent be affected if the Intergovernmental Panel on Climate Change’s (IPCC) predictions of a rising temperature will become a reality. This is one of the reasons why I have chosen Burkina Faso, situated in the south end of the Sahel region, as the objective for my MFS. The question of rising temperatures will be especially important here as the region is very sensitive to differences in temperature. A crucial topic in this part of the world as well as the topic of this study is the process of adapting to the new climatic situation.

This dissertation focuses on the assessment of projected changes on water resources by the end of this century (2071-2100), considering an ensemble of high resolution future climate scenarios, the effects of hydrological parameterisation, and the bias of the hydrological model in representing different streamflow magnitudes. Quantification of the impacts of climate change on water resources will depend on the emission scenario, climate model, downscaling technique and impact model used to drive the impact study. In particular, hydrological impact studies involve important decisions (e.g., model structure, parameterisation, input data) whose effects are reflected into the final impacts. As a result, quantification of impacts of climate change have to be seen as a "cascade of uncertainty", in which decisions taken in every step of the assessment process convey uncertainties that are unavoidably propagated to subsequent levels. At the other hand, uncertainties in projections of climate models and those involved in the quantification of their hydrological response limit the understanding of those future impacts and hamper the assessment of mitigation policies. The Soil and Water Assessment Tool (SWAT) hydrological model was set up for daily simulations of the western part of the Ebro River basin (~ 42000 km2) in Spain, during the control period 01/Jan/1961 to 31/Dec/1990, and two subcatchments were selected for testing the methodology proposed in this dissertation. A sensitivity analysis with Latin Hypercube One-factor-At-a-Time (LH-OAT) was carried out in order to identify parameters with a high effect on simulated streamflows. Then, an uncertainty analysis was carried out using the Generalized Likelihood Uncertainty Estimation (GLUE) methodology, in order to select parameter sets that can be considered as acceptable simulators of the system, adopting a re-scaled Nash-Sutcliffe efficiency as "less formal" likelihood, and a cut-off threshold equal to zero to discriminate between behavioural and non-behavioural simulators. Afterwards, a Latin Hypercube (LH) sampling strategy was implemented within GLUE, in order to reduce the number of model runs required to obtain a good exploration of the parameter space. The 95% of the cumulative distribution of each predicted output, weighted by the re-scaled likelihood of each behavioural parameter set, was used to compute the predictive uncertainty bounds, both during the control and future scenarios. Bias-corrected daily time series of precipitation and air temperature, for the future period 2071-2100, were derived from an ensemble of six high-resolution climate change scenarios, selected from the EU FP5 PRUDENCE project. Long-term averages of precipitation and air temperature fields were computed for the control period, and projected anomalies for the future scenarios were computed as well, in an annual, seasonal and monthly basis, including expected changes for different elevation bands within the basin. The same bias-corrected time series were then used to drive daily hydrological simulations during the future period on the two selected catchments. For each climate scenario, a number of simulations equal to the number of behavioural parameter sets obtained during the uncertainty analysis was carried out. Resulting streamflows were used to compute daily flow duration curves (FDCs) to provide a qualitative assessment of the relative importance of uncertainties coming from the choice of the driving RCM and from hydrological parameterisation. In addition, streamflows derived from running each climate scenario with its corresponding behavioural parameter sets, were used to compute empirical cumulative density functions (ECDFs) of three selected percentiles, representing different flow magnitudes, in order to provide a quantitative assessment of the projected changes in streamflows. We observed that the hydrological parametric uncertainty was larger than the uncertainty coming from the driving RCM, during the complete future period and each one of the four seasons, for the two selected catchments. However, this result can not be generalised, because it is conditional to decisions taken during the uncertainty analysis and to the ensemble of RCMs considered. Empirical CDFs computed for projected values of low (Q5), medium (Q50) and high (Q95) flows show that there is a general projected decrease in all the streamflow magnitudes, but bias in the representation of the streamflows during the control period 1961-1990 hamper the assessment of reliable quantitative projections for low and medium flows, whereas projected decreases for high flows range from 0 to 60%, depending on the catchment and the climate scenario considered.

The majority of climate-health impacts are the result of extreme climatic events. In the Amazon region, hydrological extremes have become more frequent in recent years. Evidence exists about how these hydrological extremes affect the forest itself, yet little information is available on the impacts on human health. Hospitalisations for respiratory diseases are the leading cause of hospitalisations, excluding pregnancy related causes, for both Brazil, and the Brazilian Amazon. It has been shown elsewhere that during drought events and periods of intense fires there are statistically significant associations with respiratory health. Despite the increase in hydrological extremes and high rates of deforestation and fires observed annually in the Legal Amazon, there are limited studies linking such events and respiratory health. The lack of explicit spatial understanding about these connections restrains the ability of policymakers to plan and implement regional mitigation and adaptation policies in order to cope with predicted effects of climate change in the Amazon, one of Brazil’s poorest regions. Thus, this thesis explores the impacts of three large hydrological extremes: the 2005, and 2010 droughts and the 2009 flood, on children’s respiratory health in the Legal Amazon. The research is two-fold; firstly to establish how the extremes and associated human disturbance impact respiratory health in the region. A Geographically Weighted Poisson Regression is adopted which allows for local spatial data analysis to identify any relationships between selected variables and children’s respiratory health throughout the Legal Amazon. The second part explores local communities’ knowledge of respiratory health and the links to the environment which has assisted in creating recommendations to cope with respiratory health and environmental problems in the Legal Amazon.

Bryophytes are able to intercept atmospheric water over the entire surface of their shoot and, once intercepted, this water forms a vital part of the hydrological cycle of their surrounding ecosystems. To investigate the role of bryophytes in the hydrological cycle, our study, conducted in the biodiversity hotspot of the tropical montane cloud forest of La Réunion, focused on two leafy liverwort species, Mastigophora diclados and Bazzania decrescens. We evaluated liverwort biomass, water storage capacity, atmospheric or cloud water interception, and photosynthetic response to desiccation. We found that B. decrescens stored approximately double the mean and maximum litres of water per hectare despite occupying less than half the volume of M. diclados. Despite this decreased water storage capacity, we found that M. diclados had a greater ability to intercept atmospheric moisture than B. decrescens, which had similar interception ability to the control. These interception abilities affected water flux in the two liverwort species. We found that this variation in water flux had an effect on photosynthesis. Both species displayed a significant relationship between photosynthesis and water content. We found that both species showed a loss of photosynthesis at very low and very high water contents with the optimal water content for photosynthesis corresponding to the in situ water content of the liverworts. The abundance of both species and their cloud water interception ability together with the wide range of photosynthetic tolerance of M. diclados and the large water storage capacity and slow desiccation rate of B. decrescens make both liverwort species ecologically important in the forest's hydrological cycle. Anthropogenic climate change threatens this ecosystem as the cloud that these species are so dependent on is predicted to lift. Our findings tie the liverworts very closely to their environment and therefore show support for the idea that bryophytes are excellent early warning signals for predicted climate changes.

The application of water resources planning models to semi-arid or arid areas is expected to be particularly challenging because of the high variability of rainfall and streamflow, highly limited historic observations, sparse rain gauge and flow networks with significant periods of missing rainfall and potential data quality issues. These lead to high uncertainty in rainfall and hydrological models which need to be explicitly represented in model predictions. These uncertainties are expected to increase when considering future predictions associated with the effects of climate change. This has presented an opportunity for this thesis to develop a framework of uncertainty analysis in hydrological and water resources modelling. The framework consists of multi-site continuous time stochastic rainfall model to (1) identify suitable rainfall predictors, (2) infill the missing values in the historic rainfall data, (3) extend the limited rainfall observations, and (4) generate rainfall under climate change scenarios by downscaling global climate models outputs. The stochastically infilled rainfall data allows calibration of a hydrological model under input uncertainty. The rainfall model together with the uncertain hydrological model are then used to generate multiple realisations of reservoir inflows over a 100-year period, first assuming a stationary climate and secondly under a changed climate. This framework is applied to the upper Limpopo basin in Botswana, using 25 years of observed daily rainfall and flow data for model calibration. A Generalised Linear Model was used for the rainfall and a semi-distributed version of the IHACRES model was used for the hydrology. A proposed 382 Mm3 reservoir at the outlet of this basin, which is part of Botswana‘s national water resource strategy, is re-evaluated in light of the extended inflow data and the estimated uncertainty. Analysis within this thesis revealed that the effects of data and model parameter uncertainty on water resources planning models can be high, and thus should not be ignored. The thesis advocates a shift from deterministic to stochastic ways of infilling missing rainfall values, and for consideration of hydrological model uncertainty, climate model and climate scenario uncertainties. Given the high uncertainty in the semi arid case study, priority areas can be identified, which may include acquiring and expanding the gauge networks, building efficient and robust data collection processing and achieving to improve the existing database so as to support and enable quality research.