The Tropical savannas of central Brazil (cerrado) and the Everglades wetland (Florida) ecosystems are ideal systems to study landscape spatial mosaics and their interactions. Both ecosystems show a variety of plant physiognomies distributed within small spatial scales and elevation gradients. Such variety of plant physiognomies provide an opportunity to investigate the roles of climate, topography, nutrient availability and water table dynamics as determinants of plant physiognomic distributions, and their role in shaping regional systems. South Florida Wetlands and the tropical savannas of central Brazil are examples of hydrologically-controlled ecosystems. In hydrologically-controlled ecosystems water sources, the availability of nutrients, and the patterns of water movement play important roles in determining vegetation structure and function. The main objective of this study was to understand ecosystem level processes that shape different physiognomies in two hydrologically-controlled ecosystems. I conducted field work at the IBGE ecological reserve, a field experimental station located in Brasilia, Brazil. I also worked at the Everglades National Park in an area located near the south entrance of the Park in Homestead, Florida. I carried out three interconnected studies investigating water and nutrient dynamics: (1) In a Brazilian savanna I manipulated levels of litter input and measured changes to soil properties, organic matter decomposition and tree growth. I found that changes in litter input affect soil physicochemical properties and soil biochemical processes. I also found that litter dynamics influence tree growth through their effects on soil physicochemical properties. (2) I also studied the effect of water table depth and its temporal variation on spatial patterns of vegetation distribution in the cerrado landscape. I monitored diurnal and seasonal changes in water table depth along two tree-density and topographic gradients. In addition, I measured woody species composition, growth rates of four tree species, litter production, soil nutrients, and nutrient resorption efficiency along those two gradients. I found that water table depth has an important role in determining the spatial distribution of cerrado physiognomies; it also affects tree growth, species composition and nutrient resorption efficiency. (3) In the Everglades I studied patterns of underground water uptake by two vegetation types. I monitored seasonal and diurnal changes in water table depth in a Hammock forest, in a stand dominated by the invasive woody species Schinus terebinthifolius, as well as the water level in an adjacent lake. I estimated stand level transpiration using two different approaches: with sap flow measurements and diurnal oscillations in water table levels. Then, I calculated the total quantity of groundwater withdrawn by evapotranspiration for the wet and dry seasons in the Hammocks and in the exotic invaded site and then compared the results. I found that water uptake by Everglades trees is well coupled to diurnal changes in water table depth and that the amount of water withdrawn from the groundwater was larger during the wet season than during the dry season. Finally, I detected hydrological feedbacks between different vegetation types and nearby bodies of water. Results of this study contributes to the current knowledge of ecosystem level processes in tropical and subtropical ecosystems where water circulation and water availability play a dominant role in shaping vegetation structure and function.

The scope of this study is to investigate the environmental change in the German part of the Elbe river basin, whereby the focus is on two water related problems: having too little water and having water of poor quality. <br><br> The Elbe region is representative of humid to semi-humid landscapes in central Europe, where water availability during the summer season is the limiting factor for plant growth and crop yields, especially in the loess areas, where the annual precipitation is lower than 500 mm. It is most likely that water quantity problems will accelerate in future, because both the observed and the projected climate trend show an increase in temperature and a decrease in annual precipitation, especially in the summer. Another problem is nutrient pollution of rivers and lakes. In the early 1990s, the Elbe was one of the most heavily polluted rivers in Europe. Even though nutrient emissions from point sources have notably decreased in the basin due to reduction of industrial sources and introduction of new and improved sewage treatment facilities, the diffuse sources of pollution are still not sufficiently controlled. <br><br> The investigations have been done using the eco-hydrological model SWIM (Soil and Water Integrated Model), which has been embedded in a model framework of climate and agro-economic models. A global scenario of climate and agro-economic change has been regionalized to generate transient climate forcing data and land use boundary conditions for the model. The model was used to transform the climate and land use changes into altered evapotranspiration, groundwater recharge, crop yields and river discharge, and to investigate the development of water quality in the river basin. Particular emphasis was given to assessing the significance of the impacts on the hydrology, taking into account in the analysis the inherent uncertainty of the regional climate change as well as the uncertainty in the results of the model. <br><br> The average trend of the regional climate change scenario indicates a decrease in mean annual precipitation up to 2055 of about 1.5 %, but with high uncertainty (covering the range from -15.3 % to +14.8 %), and a less uncertain increase in temperature of approximately 1.4 K. The relatively small change in precipitation in conjunction with the change in temperature leads to severe impacts on groundwater recharge and river flow. Increasing temperature induces longer vegetation periods, and the seasonality of the flow regime changes towards longer low flow spells in summer. As a results the water availability will decrease on average of the scenario simulations by approximately 15 %. The increase in temperatures will improve the growth conditions for temperature limited crops like maize. The uncertainty of the climate trend is particularly high in regions where the change is the highest. <br><br> The simulation results for the Nuthe subbasin of the Elbe indicate that retention processes in groundwater, wetlands and riparian zones have a high potential to reduce the nitrate concentrations of rivers and lakes in the basin, because they are located at the interface between catchment area and surface water bodies, where they are controlling the diffuse nutrient inputs. The relatively high retention of nitrate in the Nuthe basin is due to the long residence time of water in the subsurface (about 40 years), with good conditions for denitrification, and due to nitrate retention and plant uptake in wetlands and riparian zones. <br><br> The concluding result of the study is that the natural environment and communities in parts of Central Europe will have considerably lower water resources under scenario conditions. The water quality will improve, but due to the long residence time of water and nutrients in the subsurface, this improvement will be slower in areas where the conditions for nutrient turn-over in the subsurface are poor. / Ziel der vorliegenden Arbeit ist die Untersuchung der Auswirkungen des Globalen Wandels auf den Wasserkreislauf im deutschen Teil des Elbeeinzugsgebietes. Der Fokus liegt dabei auf Wassermengen- und Wasserqualitätsproblemen. <br><br> Die Elbe liegt im Zentrum Europas im Übergangsbereich zwischen ozeanischen und kontinentalen Klimaten, wo die Wasserverfügbarkeit in den Sommermonaten den limitierenden Faktor für das Pflanzenwachstum und die landwirtschaftlichen Erträge bildet. Dies gilt insbesondere für die Lössgebiete im Lee des Harzes, wo die jährlichen Niederschläge unter 500 mm liegen. Es ist sehr wahrscheinlich, dass sich die Wassermengenprobleme in Zukunft noch verstärken werden, denn sowohl das beobachtete als auch das für die Zukunft projizierte Klima in der Region zeigen höhere Temperaturen und fallende Niederschläge, besonders im Sommer. Ein weiteres Problem ist die hohe Nährstoffbelastung der Flüsse und Seen im Elbeeinzugsgebiet. Anfang der neunziger Jahre war die Elbe eine der am stärksten belasteten Flüsse in Europa. Obwohl die Einträge besonders aus Punktquellen durch den Rückgang der Industrie und den Bau von neuen Kläranlagen seitdem gefallen sind, gelangen trotzdem noch große Nährstoffmengen aus diffusen Quellen in die Gewässer. <br><br> Die Untersuchungen wurden unter Anwendung des ökohydrologischen Modells SWIM (Soil and Water Integrated Model) durchgeführt, welches über Schnittstellen mit Klimamodellen und agroökonomischen Modellen verbunden wurde. Ein globales Szenario des Klimawandels und des landwirtschaftlichen Wandels wurde regionalisiert, um so die geänderten Randbedingungen für den Szenarienzeitraum zu erhalten. Simulationen mit SWIM dienten dann dazu, die geänderten Randbedingungen in Änderungen im Wasserhaushalt und in den landwirtschaftlichen Erträgen zu transformieren. Außerdem wurde das Langzeitverhalten von Nährstoffen im Untersuchungsgebiet modelliert. Besonderer Wert wurde dabei darauf gelegt, die Unsicherheit der Szenarienergebnisse zu quantifizieren. <br><br> Der mittlere Szenarientrend zeigt eine Reduzierung der mittleren jährlichen Niederschläge bis zum Jahre 2055 um ungefähr 1.5 %, wobei die Ergebnisse mit einer großen Unsicherheit behaftet sind: die Spannweite der Niederschläge in den Szenarienrealisationen liegt zwischen -15.3 % und +14.8 %. Die Erwärmung unter Szenarienbedingungen mit ungefähr 1.4 K ist weniger unsicher. Diese relativ geringen Änderungen habe starke Auswirkungen auf den Wasserhaushalt im Elbegebiet: durch die steigenden Temperaturen wird die Vegetationszeit verlängert, und die Niedrigabflussperiode im Sommer wird sich in den Herbst ausdehnen. Insgesamt wird unter dem mittleren Szenarientrend die Wasserverfügbarkeit um ca. 15 % abnehmen. Außerdem werden sich durch die steigenden Temperaturen die Anbaubedingungen für wärmeliebende Ackerfrüchte in der Landwirtschaft verbessern. Die Unsicherheit des Klimatrends ist dort am größten, wo auch die lokalen Änderungen am größten sind. <br><br> Die Simulationsergebnisse für das Nuthe-Teileinzugsgebiet der Elbe zeigen, das Retentionsprozesse im Untergrund und in den Feucht- und Auengebieten einen starken Einfluss auf die Wasserqualität und die Nitratkonzentration der Oberflächengewässer haben, da sie durch ihre Lage im Einzugsgebiet eine Schnittstelle zwischen dem umliegenden Einzugsgebiet und den Flüssen und Seen bilden. Die relativ hohe Umsetzung von Nitrat im Einzugsgebiet der Nuthe kann dadurch erklärt werden, dass Nitrat eine relativ lange Aufenthaltszeit im Grundwasser (im Mittel 40 Jahre) mit einer hohen Nitratumsetzungsrate hat, und durch die guten Denitrifizierungsbedingungen in den Feucht- und Auengebieten. Dazu kommt noch, dass große Nitratmengen durch die Pflanzen in den Feuchtgebieten aus dem Grundwasser aufgenommen werden. <br><br> Zusammenfassend kann man sagen, das sich die Ökosysteme und die Gesellschaft im Elbeeinzugsgebiet unter Szenarienbedingungen auf niedrigere Wasserverfügbarkeit einstellen müssen. Die Wasserqualität wird sich grundsätzlich zwar weiter verbessern, aber aufgrund der langen Verweilzeit der Nährstoffe im Grundwasser wird dies insbesondere in den Teileinzugsgebieten, in denen die geochemischen Bedingungen für einen hohen Nährstoffumsatz nicht gegeben sind, noch relativ lange dauern.

The Bridge River drains the east slope of the Coast Mountain Range and is a major tributary of the Fraser River in southwestern British Columbia. The lower Bridge River has been regulated since the installation of Terzaghi Dam in 1948, which left a section of dry riverbed for an interval of 52 years prior to 2000. An out-of-court settlement between BC Hydro and Federal and Provincial Fisheries regulatory agencies resulted in the required experimental discharge of 3 m3/s below Terzaghi Dam in 2000. This study investigated growth of black cottonwood (Populus trichocarpa) trees in response to the experimental discharges. Mature trees did not show a significant response in radial trunk growth or branch elongation. In contrast, the juvenile trees displayed an increased growth response, and the successful establishment of saplings provided a dramatic response to the new flow regime. Thus, I conclude that cottonwoods have benefited from the experimental flow regime of the lower Bridge River. / xii, 89 leaves : ill. (some col.) ; 29 cm

Water scarce countries such as South Africa are subject to various hydrological constraints, particularly within resource poor farming communities that are reliant on rainfed agriculture. Recent initiatives to address this issue have shifted focus to explore more efficient alternatives to water supply. Adoption of water system innovations through the use of runoff harvesting is one such alternative that provides a means to supplement water use for increased food production. However, increasing the implementation of runoff harvesting, without encountering unintended impacts on downstream hydrological and ecological systems, requires better understanding of the hydrologic and environmental impacts at catchment scale. The objective of this dissertation was to gain knowledge to the ecohydrological impacts that are likely to occur with the adoption of water system innovations as a means for upgrading rainfed smallholder farming systems. To fulfil this objective, a research component was developed whereby tools were utilised to facilitate this process on the basis of two broad aims. The first aim entailed developing a method for locating areas that are most suitable for the adoption of runoff harvesting using Geographical Information Systems (GIS). This was achieved by spatially modelling physical properties of the landscape which influence runoff response. Combining potential runoff with socio-economic factors produced a runoff harvesting map of sites with low, medium and high suitability. This is illustrated by a case study at the Potshini catchment, a small sub-catchment in the Thukela River basin, South Africa. The second aim involved modelling the impacts that runoff harvesting would have on the downstream hydrology and ecology based on the alteration of the flow regimes. To accomplish this, the ACRU Agrohydrological model which was configured to represent runoff harvesting, was used to simulate streamflow for quaternary catchments within the headwaters of the Thukela River basin. Simulated streamflows from ACRU was input into the IHA model to generate ecologically relevant hydrological parameters. Alteration of the flow regime due to runoff harvesting was mostly a reduction in high and low flows however the impacts were insignificant. This suggests that, depending on the intensity of runoff harvesting, downstream ecological impacts are insignificant. / Thesis (M.Sc.) - University of KwaZulu-Natal, Pietermaritzburg, 2009.

Sabe-se que a formação de reservatórios altera a qualidade e a quantidade da água de montante e jusante e que a direção e a magnitude das alterações dependem de suas características construtivas, operacionais, morfométricas, bem como do regime hidrológico e climático da região. Porém, a maior parte deste conhecimento foi fundamentada em pesquisas de reservatórios com grande capacidade de regularização, que fazem parte da realidade do Pantanal, uma região que vem sendo impactada por um número cada vez maior de reservatórios com pequena capacidade de regularização, levantando questionamentos sobre seus possíveis efeitos no funcionamento da planície de inundação. Sendo assim, este trabalho procurou (i) identificar qual o fator chave determinante no processo de estratificação e mistura vertical do reservatório e se este pode influenciar na qualidade da água; (ii) avaliar os efeitos da formação e operação do reservatório na alteração da qualidade da água de montante e jusante e (iii) avaliar os efeitos da operação do reservatório na alteração do regime hidrológico de jusante, além de propor os limites preventivos para a sustentabilidade. O estudo foi desenvolvido no reservatório de Ponte de Pedra, localizado no rio Correntes, divisa dos estados de Mato Grasso e Mato Grosso do Sul (Centro Oeste do Brail), na fronteira entre o Pantanal e o Planalto. O reservatório apresentou prolongado período de estratificação vertical (mistura no inverno) dos parâmetros físicos e químicos da água nas partes médias e profundas, mantendo-se homogêneo na parte superior, onde se encontra a captação, não alterando as características da água de jusante. Entre os fatores analisados, o vento foi o único fator que influenciou significativamente a estrutura vertical da qualidade da água sendo beneficiada pelas características morfométricas e construtivas do reservatório. Longitudinalmente, a formação do reservatório alterou significativamente quatro dos dez parâmetros analisados, com redução média de 38% da turbidez, 28% do fósforo total, 23% dos sólidos totais e 14% do nitrato. Destes, apenas a turbidez e o nitrato foram afetados pelo controle operacional do tempo de retenção hidráulica. Em relação à alteração dos parâmetros do regime hidrológico anual, dos 31 analisados, os parâmetros de vazões mínimas de curta duração (1, 3 e 7 dias), vazões máximas de 90 dias e o número de pulsos baixos e altos foram significativamente alterados pela operação do reservatório. Destes, a vazão máxima de 90 dias e o número de pulsos altos resumem os impactos, e podem ser utilizados como parâmetros alvos para restauração e conservação do regime hidrológico. As vazões sazonais também foram significativamente alteradas, com maior impacto na estação seca (inverno). Com base na variabilidade natural do rio, foram propostos os limites preventivos para a sustentabilidade, com alterações diárias permitidas de ±18% no inverno, ±24% na primavera e ±22% no verão e outono, aplicados sobre a vazão natural. De maneira geral, as alterações na qualidade da água e no regime hidrológico provocado pela formação e operação do reservatório foram consideradas baixas, tanto em número de parâmetros alterados quanto nas magnitudes das alterações, e estas foram atribuídas às baixas concentrações de partículas e nutrientes na bacia, ao sistema de captação superficial, o curto tempo de retenção hidráulica, pequena capacidade de regularização associadas à sazonalidade no regime de chuvas e ventos na região, que limitam manobras operacionais para a maximização da eficiência energética. / The formation of reservoirs changes the quality and quantity of water, both upstream and downstream, and the direction and magnitude of such changes depend on their characteristics of construction, operation, morphometry, as well as hydrological regime and climate of the region. However, much of this knowledge was based on large reservoirs, which is not the reality of the Pantanal, an area that is being impacted by a growing number of reservoirs with low capacity for regularization, raising questions about possible effects on the floodplain functioning. In this way, this study aimed (i) to identify the key factor in the process of stratification and vertical mixing of the reservoir, and whether this can influence the water quality, (ii) to evaluate the effects of the reservoir formation and operation on the quality of water upstream and downstream of the reservoir, and (iii) to examine the effects of the reservoir operation on the downstream hydrological regime, in addition to propose preventive limits for sustainability. The study was conducted at Ponte de Pedra Reservoir, located on the Correntes river, the motto between the states of Mato Grasso and Mato Grosso do Sul (Central West Brazil), on the border between the Plateau and the Pantanal. The reservoir had an extended period of vertical stratification (mixture in the winter) of physical and chemical water parameters in the medium and deep parts of the water column, being homogeneous in the upper part where the water is capitation, without changing the characteristics of the downstream water. Among the factors analyzed, the wind was the only factor that significantly influenced the vertical structure of the water quality, favored by morphometric and constructive characteristics of the reservoir. Along the longitudinal axis, the reservoir formation significantly altered the turbidity and concentrations of total phosphorus, total solids, and nitrate, with mean reduction of 38, 28, 23 and 14% of their values. Among these, only turbidity and nitrate were affected by the operational control of the hydraulic retention time. In relation to the change in parameters of the annual hydrological regime, parameters of short-term minimum flows (1, 3 and 7 days), maximum flows of 90 days and the number of low and high pulses were significantly modified by the reservoir operation. Of these, the maximum flow of 90 days and the number of high pulses have summarized the impacts, and can be used as target parameters for restoration and conservation of the hydrological regime. Seasonal flows were also significantly altered, with the greatest impact in the dry season (winter). Based on the natural variability of the river, it was proposed preventive limits for sustainability, with permitted daily changes of ±18% in winter, ±24% in spring and ±22% in summer and autumn applied on the natural flow. In general, changes in water quality and hydrological regime caused by the reservoir formation and operation were considered low, both in number of altered parameters as magnitudes of such changes, and these characteristics were ascribed to low concentrations of particles and nutrients in the basin, to the surface capitation system, short hydraulic retention time, low capacity of regularization associated with the seasonality of the regime of rainfall and wind in the region, limiting operational maneuvers for maximizing the energy efficiency.

The Matlabas mire, an actively peat accumulating wetland, is located in the headwaters of the Matlabas River, Marakele National Park, Limpopo Province, South Africa. Various seepage zones and artesian peat domes are contained in this peatland that consists of two tributaries of which the western one is partially channelled. The occurrence of decaying peat domes and desiccated areas with terrestrial vegetation, as well as the apparent erosion on the western tributary, have raised concerns on the health of this wetland. A network of piezometers was installed in the mire and results confirm that the system is fed primarily from seepage from the slopes of the catchment. Chemical analysis and temperature recorded indicate an isolated groundwater source of which the water does not mix with surface water. This is linked with isotope analysis of the age of peat in various sections of the mire. Erosion was attributed to anthropogenic changes in the catchment. Management recommendations include rehabilitation and reinstating the driving forces that support the mire. / Environmental Sciences / M. Sc. (Environmental Management)

Rivers and their catchments are under mounting pressure from direct channel modification, intensification of land use, and from a legacy of decades of channelisation. Recent legislation, in the form of the EU Water Framework Directive, places a greater emphasis on the management of water bodies as holistic systems, and includes the explicit consideration of hydromorphological quality, which describes the hydrologic and geomorphic elements of river habitats. These are defined specifically as hydrological regime, river continuity and river morphology. This appreciates that sediment and flow regimes, along with the channel structure, provides the 'template' on which stream ecological structure and function is built. Invertebrate fauna contribute significantly to the biodiversity of rivers, and often form the basis of monitoring river health. However much of the fundamental ecological knowledge base on the response of invertebrates to hydromorphological change needed to make informed decisions and accurate predictions, is either lacking, inadequate or contradictory. This thesis addresses some of the key potential shortcomings in recent bio-assessment that others have alluded to, but which have rarely been explored in the context of direct channel manipulations. By using two case studies of, realignment in a natural upland catchment, and flood protection engineering in an urban stream, this study investigates the sensitivity of hydromorphological impact assessment methods that rely on biodiversity patterns of benthic riverfly (Ephemeroptera, Plecoptera and Trichoptera) larva. This work employed widely used biomonitoring indices of benthic riverfly larva abundance, species richness, alpha and beta diversity, and community composition, applied over a range of spatial scales, in combination with spatially contemporaneous physical habitat data, to describe and explain community changes in response to disturbance, and patterns of natural variation. The effects of restoration were investigated using a high degree of sample replication within channels and across the wider catchment, as well as contrasting spring and autumn seasons. To assess change in a small urban channel, approaches that explicitly consider spatial elements of community data, using spatial eigenvectors analysis, were applied to spatially detrend community data and directly investigate spatial patterns. Restoration of the Rottal Burn was found to be successful in restoring habitat diversity and geomorphic processes, and in turn increasing reach scale species richness and beta diversity through the gradual arrival of rare and specialist taxa into novel habitats. Catchment scale replication revealed high variation in diversity indices of modified and undisturbed streams, and a strong temporal pattern related to antecedent flow conditions. Channels with greater habitat heterogeneity were able to maintain high gamma diversity during times of high flow stress by providing a number of low flow refuges along their length. The urban Brox Burn had surprisingly high riverfly richness and diversity driven by small scale hydraulic heterogeneity, created by bed roughness resulting in a range of microhabitats. Riverfly community responses to direct channel dredging could not be detected by measurements of average richness and diversity, however distinct changes were seen in gamma diversity, the identity of community members and their arrangement among sample patches. Impacts of sediment pollution release due to engineering were short lived and apparently had little detrimental impact on biodiversity. Strong spatial patterns of community assembly on the stream bed were uncovered, relating to longitudinal, edge and patchy patterns. Significant habitat drivers of community composition were confounded by high amounts of spatial autocorrelation, especially hydraulic variables. Due to the strongly physical and spatial nature of hydromorphological disturbance, turnover of species between sample locations at a range of scales, and the spatial arrangement of habitats and communities is of more use for detecting these types of subtle changes compared to mean richness or diversity. These findings have implications for the targeting of resources for monitoring of restoration, or engineering disturbances, in order to be sensitive to hydromorphological change. Efforts should target the main area of natural variability within the system, either replicating sampling in time or space to distinguish effects of impact. Spatial patterns, measures of beta diversity and species identity can be better exploited to identify systems with functioning geomorphological processes. Channel typologies proved misleading, and quantification of habitat and selection of control sites using multiple pre-defined criteria should be carried out. Studies of restoration operations and engineering impacts provide considerable opportunities for advancing our knowledge of the mechanisms that drive community response under a range of conditions to improve impact detection.

Sabe-se que a formação de reservatórios altera a qualidade e a quantidade da água de montante e jusante e que a direção e a magnitude das alterações dependem de suas características construtivas, operacionais, morfométricas, bem como do regime hidrológico e climático da região. Porém, a maior parte deste conhecimento foi fundamentada em pesquisas de reservatórios com grande capacidade de regularização, que fazem parte da realidade do Pantanal, uma região que vem sendo impactada por um número cada vez maior de reservatórios com pequena capacidade de regularização, levantando questionamentos sobre seus possíveis efeitos no funcionamento da planície de inundação. Sendo assim, este trabalho procurou (i) identificar qual o fator chave determinante no processo de estratificação e mistura vertical do reservatório e se este pode influenciar na qualidade da água; (ii) avaliar os efeitos da formação e operação do reservatório na alteração da qualidade da água de montante e jusante e (iii) avaliar os efeitos da operação do reservatório na alteração do regime hidrológico de jusante, além de propor os limites preventivos para a sustentabilidade. O estudo foi desenvolvido no reservatório de Ponte de Pedra, localizado no rio Correntes, divisa dos estados de Mato Grasso e Mato Grosso do Sul (Centro Oeste do Brail), na fronteira entre o Pantanal e o Planalto. O reservatório apresentou prolongado período de estratificação vertical (mistura no inverno) dos parâmetros físicos e químicos da água nas partes médias e profundas, mantendo-se homogêneo na parte superior, onde se encontra a captação, não alterando as características da água de jusante. Entre os fatores analisados, o vento foi o único fator que influenciou significativamente a estrutura vertical da qualidade da água sendo beneficiada pelas características morfométricas e construtivas do reservatório. Longitudinalmente, a formação do reservatório alterou significativamente quatro dos dez parâmetros analisados, com redução média de 38% da turbidez, 28% do fósforo total, 23% dos sólidos totais e 14% do nitrato. Destes, apenas a turbidez e o nitrato foram afetados pelo controle operacional do tempo de retenção hidráulica. Em relação à alteração dos parâmetros do regime hidrológico anual, dos 31 analisados, os parâmetros de vazões mínimas de curta duração (1, 3 e 7 dias), vazões máximas de 90 dias e o número de pulsos baixos e altos foram significativamente alterados pela operação do reservatório. Destes, a vazão máxima de 90 dias e o número de pulsos altos resumem os impactos, e podem ser utilizados como parâmetros alvos para restauração e conservação do regime hidrológico. As vazões sazonais também foram significativamente alteradas, com maior impacto na estação seca (inverno). Com base na variabilidade natural do rio, foram propostos os limites preventivos para a sustentabilidade, com alterações diárias permitidas de ±18% no inverno, ±24% na primavera e ±22% no verão e outono, aplicados sobre a vazão natural. De maneira geral, as alterações na qualidade da água e no regime hidrológico provocado pela formação e operação do reservatório foram consideradas baixas, tanto em número de parâmetros alterados quanto nas magnitudes das alterações, e estas foram atribuídas às baixas concentrações de partículas e nutrientes na bacia, ao sistema de captação superficial, o curto tempo de retenção hidráulica, pequena capacidade de regularização associadas à sazonalidade no regime de chuvas e ventos na região, que limitam manobras operacionais para a maximização da eficiência energética. / The formation of reservoirs changes the quality and quantity of water, both upstream and downstream, and the direction and magnitude of such changes depend on their characteristics of construction, operation, morphometry, as well as hydrological regime and climate of the region. However, much of this knowledge was based on large reservoirs, which is not the reality of the Pantanal, an area that is being impacted by a growing number of reservoirs with low capacity for regularization, raising questions about possible effects on the floodplain functioning. In this way, this study aimed (i) to identify the key factor in the process of stratification and vertical mixing of the reservoir, and whether this can influence the water quality, (ii) to evaluate the effects of the reservoir formation and operation on the quality of water upstream and downstream of the reservoir, and (iii) to examine the effects of the reservoir operation on the downstream hydrological regime, in addition to propose preventive limits for sustainability. The study was conducted at Ponte de Pedra Reservoir, located on the Correntes river, the motto between the states of Mato Grasso and Mato Grosso do Sul (Central West Brazil), on the border between the Plateau and the Pantanal. The reservoir had an extended period of vertical stratification (mixture in the winter) of physical and chemical water parameters in the medium and deep parts of the water column, being homogeneous in the upper part where the water is capitation, without changing the characteristics of the downstream water. Among the factors analyzed, the wind was the only factor that significantly influenced the vertical structure of the water quality, favored by morphometric and constructive characteristics of the reservoir. Along the longitudinal axis, the reservoir formation significantly altered the turbidity and concentrations of total phosphorus, total solids, and nitrate, with mean reduction of 38, 28, 23 and 14% of their values. Among these, only turbidity and nitrate were affected by the operational control of the hydraulic retention time. In relation to the change in parameters of the annual hydrological regime, parameters of short-term minimum flows (1, 3 and 7 days), maximum flows of 90 days and the number of low and high pulses were significantly modified by the reservoir operation. Of these, the maximum flow of 90 days and the number of high pulses have summarized the impacts, and can be used as target parameters for restoration and conservation of the hydrological regime. Seasonal flows were also significantly altered, with the greatest impact in the dry season (winter). Based on the natural variability of the river, it was proposed preventive limits for sustainability, with permitted daily changes of ±18% in winter, ±24% in spring and ±22% in summer and autumn applied on the natural flow. In general, changes in water quality and hydrological regime caused by the reservoir formation and operation were considered low, both in number of altered parameters as magnitudes of such changes, and these characteristics were ascribed to low concentrations of particles and nutrients in the basin, to the surface capitation system, short hydraulic retention time, low capacity of regularization associated with the seasonality of the regime of rainfall and wind in the region, limiting operational maneuvers for maximizing the energy efficiency.

Sabe-se que a formação de reservatórios altera a qualidade e a quantidade da água de montante e jusante e que a direção e a magnitude das alterações dependem de suas características construtivas, operacionais, morfométricas, bem como do regime hidrológico e climático da região. Porém, a maior parte deste conhecimento foi fundamentada em pesquisas de reservatórios com grande capacidade de regularização, que fazem parte da realidade do Pantanal, uma região que vem sendo impactada por um número cada vez maior de reservatórios com pequena capacidade de regularização, levantando questionamentos sobre seus possíveis efeitos no funcionamento da planície de inundação. Sendo assim, este trabalho procurou (i) identificar qual o fator chave determinante no processo de estratificação e mistura vertical do reservatório e se este pode influenciar na qualidade da água; (ii) avaliar os efeitos da formação e operação do reservatório na alteração da qualidade da água de montante e jusante e (iii) avaliar os efeitos da operação do reservatório na alteração do regime hidrológico de jusante, além de propor os limites preventivos para a sustentabilidade. O estudo foi desenvolvido no reservatório de Ponte de Pedra, localizado no rio Correntes, divisa dos estados de Mato Grasso e Mato Grosso do Sul (Centro Oeste do Brail), na fronteira entre o Pantanal e o Planalto. O reservatório apresentou prolongado período de estratificação vertical (mistura no inverno) dos parâmetros físicos e químicos da água nas partes médias e profundas, mantendo-se homogêneo na parte superior, onde se encontra a captação, não alterando as características da água de jusante. Entre os fatores analisados, o vento foi o único fator que influenciou significativamente a estrutura vertical da qualidade da água sendo beneficiada pelas características morfométricas e construtivas do reservatório. Longitudinalmente, a formação do reservatório alterou significativamente quatro dos dez parâmetros analisados, com redução média de 38% da turbidez, 28% do fósforo total, 23% dos sólidos totais e 14% do nitrato. Destes, apenas a turbidez e o nitrato foram afetados pelo controle operacional do tempo de retenção hidráulica. Em relação à alteração dos parâmetros do regime hidrológico anual, dos 31 analisados, os parâmetros de vazões mínimas de curta duração (1, 3 e 7 dias), vazões máximas de 90 dias e o número de pulsos baixos e altos foram significativamente alterados pela operação do reservatório. Destes, a vazão máxima de 90 dias e o número de pulsos altos resumem os impactos, e podem ser utilizados como parâmetros alvos para restauração e conservação do regime hidrológico. As vazões sazonais também foram significativamente alteradas, com maior impacto na estação seca (inverno). Com base na variabilidade natural do rio, foram propostos os limites preventivos para a sustentabilidade, com alterações diárias permitidas de ±18% no inverno, ±24% na primavera e ±22% no verão e outono, aplicados sobre a vazão natural. De maneira geral, as alterações na qualidade da água e no regime hidrológico provocado pela formação e operação do reservatório foram consideradas baixas, tanto em número de parâmetros alterados quanto nas magnitudes das alterações, e estas foram atribuídas às baixas concentrações de partículas e nutrientes na bacia, ao sistema de captação superficial, o curto tempo de retenção hidráulica, pequena capacidade de regularização associadas à sazonalidade no regime de chuvas e ventos na região, que limitam manobras operacionais para a maximização da eficiência energética. / The formation of reservoirs changes the quality and quantity of water, both upstream and downstream, and the direction and magnitude of such changes depend on their characteristics of construction, operation, morphometry, as well as hydrological regime and climate of the region. However, much of this knowledge was based on large reservoirs, which is not the reality of the Pantanal, an area that is being impacted by a growing number of reservoirs with low capacity for regularization, raising questions about possible effects on the floodplain functioning. In this way, this study aimed (i) to identify the key factor in the process of stratification and vertical mixing of the reservoir, and whether this can influence the water quality, (ii) to evaluate the effects of the reservoir formation and operation on the quality of water upstream and downstream of the reservoir, and (iii) to examine the effects of the reservoir operation on the downstream hydrological regime, in addition to propose preventive limits for sustainability. The study was conducted at Ponte de Pedra Reservoir, located on the Correntes river, the motto between the states of Mato Grasso and Mato Grosso do Sul (Central West Brazil), on the border between the Plateau and the Pantanal. The reservoir had an extended period of vertical stratification (mixture in the winter) of physical and chemical water parameters in the medium and deep parts of the water column, being homogeneous in the upper part where the water is capitation, without changing the characteristics of the downstream water. Among the factors analyzed, the wind was the only factor that significantly influenced the vertical structure of the water quality, favored by morphometric and constructive characteristics of the reservoir. Along the longitudinal axis, the reservoir formation significantly altered the turbidity and concentrations of total phosphorus, total solids, and nitrate, with mean reduction of 38, 28, 23 and 14% of their values. Among these, only turbidity and nitrate were affected by the operational control of the hydraulic retention time. In relation to the change in parameters of the annual hydrological regime, parameters of short-term minimum flows (1, 3 and 7 days), maximum flows of 90 days and the number of low and high pulses were significantly modified by the reservoir operation. Of these, the maximum flow of 90 days and the number of high pulses have summarized the impacts, and can be used as target parameters for restoration and conservation of the hydrological regime. Seasonal flows were also significantly altered, with the greatest impact in the dry season (winter). Based on the natural variability of the river, it was proposed preventive limits for sustainability, with permitted daily changes of ±18% in winter, ±24% in spring and ±22% in summer and autumn applied on the natural flow. In general, changes in water quality and hydrological regime caused by the reservoir formation and operation were considered low, both in number of altered parameters as magnitudes of such changes, and these characteristics were ascribed to low concentrations of particles and nutrients in the basin, to the surface capitation system, short hydraulic retention time, low capacity of regularization associated with the seasonality of the regime of rainfall and wind in the region, limiting operational maneuvers for maximizing the energy efficiency.

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.