Submitted in fulfilment of the requirements of the degree of Master of Engineering , Durban University of Technology, Durban, South Africa, 2016. / Reservoirs are designed to specific volume called the dead storage to be able to withstand the quantity of particles in the rivers flowing into it during its design period called its economic life. Therefore, accurate calculation of the quantities of sediment being transported is of great significance in environment engineering, hydroelectric equipment longevity, river aesthetics, pollution and channel navigability. In this study different input combination of monthly upstream suspended sediment concentration and upstream flow dataset for Inanda Dam for 15 years was used to develop a model for each month of the year. The predictive abilities of each of the developed model to predict the quantity of suspended sediment flowing into Inanda Dam were also compared with those of the corresponding developed Sediment Rating Curves using two evaluation criteria - Determination of Coefficient (R2) and Root-Mean-Square Error (RMSE). The results from this study show that a genetic programming approach can be used to accurately predict the relationship between the streamflow and the suspended sediment load flowing into Inanda Dam. The twelve developed monthly genetic programming (GP) models produced a significantly low difference when the observed suspended sediment load was compared with the predicted suspended sediment load. The average R2 values and RMS error for the twelve developed models were 0.9996 and 0.3566 respectively during the validation phase. The Genetic Programming models were also able to replicate extreme hydrological events like predicting low and high suspended sediment load flowing into the dam. Moreover, the study also produced accurate sediment rating curve models with low RMSE values of between 0.3971 and 11.8852 and high R2 values of between 0.9833 and 0.9962. This shows that sediment rating curves can be used to predict historical missing data of the quantity of suspended sediment flowing into Inanda Dam using existing streamflow datasets. The results from this study further show that the predictions from the Genetic Programming models are better than the predictions from the Sediment Raring Curve models, especially in predicting large quantities of suspended sediment load during high streamflow such as during flood events. This proves that Genetic Programming technique is a better predictive tool than Sediment Raring Curve technique. In conclusion, the results from this study are very promising and support the use of Genetic Programming in predicting the nonlinear and complex relationship between suspended sediment load and streamflow at the inlet of Inanda Dam in KwaZulu-Natal. This will help planners and managers of the dam to understand the system better in terms of its problems and to find alternative ways to address them.

Thesis (MScEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The designs of pump intake structures are generally verified by means of a hydraulic model study to ensure the structure will operate without large air or swirl entraining vortices. This is an expensive and time consuming process. The popularity of Computational Fluid Dynamics (CFD) is ever increasing in the engineering world and the use thereof in the modelling of flows in pump intake structures is just one of the many areas of focus. The use of a validated CFD model in the design phase of pump intakes would be beneficial, and ideally would reduce the frequency of requiring hydraulic model studies. This study investigates the applicability of using a 3 dimensional CFD model as a design tool by validation with a physical model. A physical model of a simple pump intake was available and with a few modifications the flow conditions were significantly improved. The quantitative validation of the CFD model was carried out by means of comparing corresponding point velocity magnitudes. An Acoustic Doppler Velocimeter (ADV) was used in the physical model. The data obtained were successfully filtered to remove noise and other disturbances. The qualitative validation was done by means of photographs and observations. The photographs made use of illuminated tracer particles to identify flow patterns. The CFD model compares well qualitatively, but the velocity magnitudes are not yet sufficiently reliable. It is recommended that the CFD model can be used for qualitative studies, but future research should focus on the accuracy of the CFD model. Using higher resolution velocity measurements in the physical model by means of other types of instruments, a better comparison can be made, as well as enabling validation of the ADV readings. / AFRIKAANSE OPSOMMING: Die ontwerpe van die pomp inname strukture word gewoonlik bevestig deur middel van 'n hidrouliese model studie om lug-intrekking te minimeer. Dit is 'n duur en tydrowende proses . Die gebruik van Computational Fluid Dynamics ( CFD ), ‘n tipe numeriese modelle neem toe in die ingenieurswese wêreld. Die gebruik daarvan in die modellering van vloei in pomp inname strukture is net een van die vele areas van toepassing . Die gebruik van 'n betroubare CFD model in die ontwerp fase van pomp innames sal voordelig wees , en ideaal sou die noodaaklikheid van fisiese hidrouliese model studies verminder. Hierdie studie ondersoek die toepaslikheid van die gebruik van 'n 3 -dimensionele model CFD model as 'n ontwerp instrument deur bevestiging met 'n fisiese model . 'n Eenvoudige pomp-inname model was beskikbaar en het met ‘n paar veranderinge die vloei toestande aansienlik verbeter . Die kwantitatiewe bevestiging van die CFD model is uitgevoer deur middel van vergelyking van korresponderende punt snelheid groottes. In die fisiese model is die snelhede met 'n Akoestiese Doppler Velocimeter (ADV) gemeet. Die data wat verkry is suksesvol gefiltreer om geraas en ander versteurings te verwyder . Die kwalitatiewe bevestiging is gedoen deur middel van foto's en waarnemings. In die foto's is gebruik gemaak van verligte spoor deeltjies om vloei patrone te identifiseer. Die CFD model vergelyk kwalitatief goed, maar die snelheid groottes is nog nie voldoende betroubaar nie. Dit word aanbeveel dat die CFD model gebruik kan word vir kwalitatiewe studies, maar toekomstige navorsing behoort te fokus op die verbeteringe van dieakkuraatheid van die CFD model. Met behulp van 'n hoër resolusie snelheid metings van die fisiese model, deur middel van ander tipe instrumente, kan 'n beter vergelyking gemaak word , sowel as die geldigheid van die ADV lesings in staat te stel.

Thesis (MScConsEcol (Conservation Ecology and Entomology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Riparian ecosystems of the Mediterranean south-western Cape region are projected to experience significant decreases in streamflow due to climate change and increased demands for water associated with human demographic trends and increasing living standards. Aggravating this problem are woody invasive alien plants, such as Acacia mearnsii, whose impacts, including those on catchment water yields, have justified extensive eradication programmes such as Working for Water (WfW). WfW has been highly successful in managing invasive alien species in some areas, while at the same time enhancing the quality of life of poor South Africans. Unfortunately, the managers of these eradication initiatives often experience a lack of information on the species- and site-specific ecological properties that may aid in prioritising sites more prone to invasion, essentially inhibiting accurate management output. Knowledge, such as that associated with the possible future distribution of invasive species in a changing environment, may help to optimise eradication initiatives. I therefore determined whether woody plants portray different physiological (vulnerability to cavitation) and wood anatomical traits (wood density, vessel resistance to implosion, vessel lumen and wall diameters) across three prominent riparian zones in the south-western Cape that each differ in streamflow quantity – to gain a mechanistic understanding of how woody species, especially invasive species, adapt their hydraulic strategy across this proxy for water availability. Using factorial ANOVA’s, to distinguish any differences in plant physiological and wood anatomical responses to water availability within and between species, showed Acacia mearnsii having consistently higher drought-tolerance (lower P50 values and denser wood) compared to native species under reduced water availability. These results supported the significant variation in drought-tolerance strategies that exist within and between taxonomically different species across different environments. Water availability thus has a strong selective effect on functional traits of species; however, minimum water potentials were more useful in describing in situ hydrological conditions than streamflow. Additionally, a non-causal relationship between wood anatomical traits and drought-induced cavitation was observed. Therefore, using only wood anatomical measurements to assess drought-tolerance of species might not be accurate across all species. This mechanistic approach to assess the invasive potential of species under projected drier conditions has great practical value. It can be used to improve species selection for restoration initiatives, and is of great value for future use in prioritizing eradication programmes. / AFRIKAANSE OPSOMMING: Rivieroewer ekosisteme in die Mediterreense Suidwes-Kaap streek kan groot afnames in stroomvloei verwag, wat meestal toegeskryf kan word aan klimaatsverandering en die verhoogde aanvraag na water geassosieerd met stygende populasiegrootte. Uitheemse indringerplante soos Acacia mearnsii vererger hierdie probleem. Laasgenoemde spesies plaas groot druk op opvanggebiede se water opbrengs, en vorm grootliks die rede waarom uitroeiing programme soos Werk vir Water (WfW) gestig is. WfW het al groot suksesse behaal in die bestuur van uitheemse indringerplante, en terselfdertyd die lewenskwaliteit van arm Suid-Afrikaners verhoog. Ongelukkig sukkel hierdie indringer uitroeiing inisiatiewe telkens met ongenoegsame bewyse wat kan help om leiding te verskaf by die prioritisering van areas meer geneig tot indringing. Die gevolg is dat onvoldoende bestuurs besluite gemaak kan word. Gevolglik sal kennis geassosieerd met die moontlike toekomstige verspreiding van hierdie indringerplant in ʼn veranderlike omgewing help om uitroeiing programme meer akkuraat te stel en gevolglik waardevol wees t.o.v. prioritisering van kwesbare areas. Die doel van hierdie studie was om die kwesbaarheid van sleutel inheemse houtagtige rivier spesies en veral die dreigende indringerplant Acacia mearnsii, te bestudeer in terme van verlaagde stroomvloei soos voorspel vir die Wes-Kaap fynbos ekosisteem. Deur te bepaal of houtagtige plante verskillende fisiologiese (kwesbaarheid teen xileem blokkasie) en anatomiese (hout digtheid, vat weerstandbiedendheid teen inmekaarkolking, vat holte en wand deursnee) hidrologiese eienskappe tentoonstel gemeet tussen drie prominente rivieroewer sones in die suidwes Kaap wat variëer in stroomvloei kwantiteit, verskaf ʼn meganistiese begrip van hoe spesies, veral die indringerplante, hul hidrologiese strategieë ten opsigte van droogtes kan aanpas. Faktoriële ANOVAS’s tussen spesies en liggings het getoon dat beide plant fisiologiese en hout anatomiese data beduidend variëer tussen taksonomies verskillende spesies. Veral Acacia mearnsii het deurgaans laer P50 waardes asook hoër houtdigtheid getoon, ‘n teken van hierdie spesies se verhoogde droogte toleransie in vergelyking met die inheemse spesies. Wat beduidend is is dat spesies-spesifieke lewensstrategieë ten opsigte van droogte toleransie in hierdie rivieroewer sones voorkom. Resultate het bevestig dat water beskikbaarheid ʼn groot rol speel in die seleksie van funksionele karaktereienskappe in plante, maar, dat minimum water potensiaal meer akkuraat was om in situ hidrologiese toestande te beskryf as wat stroomvloei kon. Die verhouding tussen plant fisiologiese en hout anatomiese karaktereienskappe was indirek as gevolg van spesies-spesifieke lewensstrategieë. Gevolglik sal die allenige gebruik van hout anatomiese eienskappe om droogte toleransie in plante te assesseer onakkuraat wees omdat daar ʼn swak verhouding tussen hout anatomie en droogte-geïnduseerde xileem blokkasie bestaan. ʼn Meganistiese benadering om die indringing potensiaal van spesies onder voorspelde droër kondisies te assesseer, asook om spesies seleksie vir restourasie doeleindes op te skerp, is prakties uitvoerbaar, en van groot waarde vir toekomstige gebruik in uitroeiing en restourasie inisiatiewe.

Relationships between thunderstorm and watershed variables and runoff from or within semiarid watersheds at Walnut Gulch, Arizona were examined. Variables showing greater sensitivity to basin and storm size were better flow predictors. Stepwise regression with three increasingly nonlinear algebraic models showed mean storm depth was the best simple predictor of runoff. Predictions improved using storm volume, a product of storm depth and areal extent. Initial runoff to streams was best described as a highly nonlinear function of storm and watershed variables. Runoff from a basin was a more linearized function of similar variables. The above differences were ascribed to channel transmission losses, reductions in runoff moving down initially dry channels. For a given basin and small storms, loss to runoff ratios exceeded 10:1 and were highly variable. Ratios were similar and less than 0.5:1 for storms centrally located over a basin and generating sufficient initial runoff to minimize flow variation due to losses. Losses increased disproportionately with basin size. Antecedent rainfall and first summer flows also affected rainfall runoff relationships in a differential manner. Wet conditions enhanced runoff more from larger versus smaller storms. First summer flows were less than expected probably because of higher soil infiltration and channel losses at the onset of summer storms. Overall, as storm size decreased or basin area increased, initial runoff was more often a localized phenomenon and downstream flow more dependent on storm depth, extent, location, and seasonal timing and basin channel losses, but less dependent on antecedent rainfall. Consequently, storm depth accounted for only 60% to 70% of the variation in flows while storm volume, antecedent rainfall, channel losses, and first summer flows explained 80% to 90%. Finally, oversimplifying storm or watershed variables or analytical methods led to errors in assessing their affect on runoff. It was also determined that current arguments supporting a recommendation to delete smaller, frequent annual floods to better fit remaining data to flood frequency curves were oversimplified. Distributed rainfall - runoff models with channel losses and regional storm depth - area - frequency data may be the way to develope flood curves for semiarid basins with short runoff records.

The Klein Berg River catchment is intensely cultivated with orchards, vineyards and wheat, while also ensuring a water supply to the main urban center, Tulbagh, and the two conservation areas (Waterval and Groot Winterhoek). The primary objective of this thesis is to determine channel change over a long and short time period, and to relate these changes to landuse change within the catchment. <br /> <br /> Assessing stability of a selected reach within the catchment was done on a short term basis with the use of erosion pins and cross<br /> profiles, while aerial photographs of over 55 years (acquired during 1942, 1967, 1987 and 1997) which were analysed using Geographic Informations Systems. Rainfall and discharge data, which were available for a period of 49-years were statistically analysed and used to determine trends. Vegetation characteristics were assessed by means of transects within the study reach. The results over the short time period (18 months) indicate noticeable channel change in the form of erosion and deposition within the channel. Bank material composition and riparian invasive alien vegetation play an important role in bank stability. Sand was the dominant grain size of the bank material, and fluvial entrainment occurred during periods of high flow. Woody alien trees prevent the growth of protective ground vegetation, and thus the soil is prone to erosion. Undercutting was also observed with the invasive woody trees, resulting in treefall. Debris dams were also common in the channel and depending on their position in the channel, either cause or prevent bank erosion. Landuse change over the 55-year period illustrated its effects on channel stability. Shrublands within the catchment has been replaced with invasive alien vegetation along the riparian zone, while shrublands along the Obiekwa Mountains, were replaced with cultivated lands. The patterns (shape and size) of lateral and point bars within the study area changed significantly within the 55-year period, which indicates a change in the discharge and sediment dynamics within the catchment. The change in sediment dynamics may be due to agricultural activities and urbanization. The increased trend in rainfall, especially during the winter season within the catchment is also an important catchment control. The study has revealed the integrated nature of variables within the catchment. It is thus recommended that a holistic and integrated approach at a catchment scale is required in the assessment of channel change of a river.

Climate change and introduced species are among the top five threats to freshwater systems face. Tropical regions are considered to be especially sensitive to the effects of climate change, while island systems are more susceptible to species introductions. Climate-driven changes in rainfall are predicted to decrease streamflow and increase flash flooding in many tropical streams. In addition, guppies (Poecilia reticulata), an invasive fish, have been introduced to many tropical freshwater ecosystems, either intentionally for mosquito population control, or accidentally because of the aquarium trade. This dissertation examines the effects of climate-driven change in rainfall and introduced guppies on stream structure (resource and invertebrate biomass and composition) and function (nutrient recycling) in Trinidad and Hawaii. In the first data chapter we used a time series to examine how nutrient recycling of guppies changes in the first 6 years after introduction to a new habitat and to examine drivers of these changes. We found that when guppy populations establish in a new environment, they show considerable variation in nutrient recycling through time. This resulted from changes in guppy density in the first two years of introductions, and changes in individual excretion in subsequent stages. In the following chapter we utilized a rainfall gradient that mimics forecasted, climate-driven changes in precipitation and resulting changes in streamflow to examine the effects of climate change on stream food resources and macroinvertebrates. We found that the drying of streams across the gradient was associated with a decrease in resource quality and a 35-fold decline in macroinvertebrate biomass. Invertebrate composition also switched to taxa with faster turnover rates. In the third data chapter we used this same space-for-time substitution approach to determine if climate-driven changes in stream structure also affected stream function. We showed that population nutrient recycling rates declined at the drier end of our rainfall gradient as a result of drops in population densities. We also found that under the current climate scenario, community excretion supplied up to 70% of the nutrient demand, which was ten-fold lower with projected climate changes in streamflow. Lastly, since freshwater ecosystems often face multiple human impacts, including climate change and invasive species, we wanted to understand how climate-driven changes in flow might alter the impact of introduced guppies on stream ecosystems. We selected several streams with guppies and several without guppies along the Hawaii rainfall gradient to examine if the effect of guppies changed with differences in streamflow. We found that the two stressors had synergistic effects on macroinvertebrate biomass and nutrient recycling rates. We concluded that climate change appeared to enhance effects of guppies, through direct and indirect effects. Overall, this dissertation shows that both climate change and species invasion can affect stream ecosystems at multiple levels of organization. This dissertation demonstrates that the effects of anthropogenic stressors are not static through time, and emphasizes the need and utility of using several methodological approaches when measuring the temporal effects of stressors. We also underline the significance of assessing multiple stressor interactions, as more than one stressor often impacts ecosystems. / Graduate / 2019-09-01

Fontes renováveis de energia representam alternativas para a mitigação da mudança do clima global, no entanto, são mais suscetíveis a mudanças nas condições climáticas. O sistema elétrico brasileiro (SEB) possui a peculiaridade de ter maior parte de sua energia gerada a partir de fontes renováveis, principalmente usinas hidrelétricas. Por essa razão, constitui uma amostra representativa das dificuldades de operar uma matriz energética de base predominantemente renovável. A geração predominantemente hidrelétrica de energia permite operar com baixas emissões e baixos custos operacionais, nada obstante a forte dependência dessa envolve considerável risco hidrológico, principalmente em um contexto em que as restrições à armazenagem de energia em grandes barragens são maiores. Por conseguinte, a combinação de investimentos inadequados na capacidade de geração com escassez de chuvas pode, eventualmente, levar a situações nas quais a capacidade de oferta seja inferior à demanda e até mesmo a racionamentos (2001). É evidente que a capacidade de prever com precisão o índice de chuvas e, consequentemente, as vazões disponíveis para o próximo período caracteriza-se como uma importante ferramenta para a operação do setor elétrico brasileiro. Hoje, as previsões de vazões futuras são realizadas com base na observação de vazões passadas sem incorporar nas análises as variáveis que as determinam (por exemplo, variáveis climáticas). Entretanto, existem evidências de que a variabilidade das vazões na América do Sul é cadenciada pelos sistemas acoplados do tipo oceano-atmosférico, os chamados fenômenos de grande escala como é o caso do El Niño. No entanto as técnicas tradicionais de previsão até então não utilizam de forma sistêmica as informações climáticas. A metodologia aqui apresentada incorpora informações sobre o clima para tomada de decisões envolvendo recursos hídricos, sendo demonstrada sua aplicação para a região Sudeste do Brasil. Demonstra-se que o manuseamento de variáveis climáticas (mais particularmente aquelas vinculadas ao fenômeno do El Niño) permite calcular a previsão de vazões tão bem quanto os programas oficiais, tendo como vantagem acompanhar as mudanças climáticas eminentes. A metodologia proposta é formada pelas seguintes partes: Modelo SARIMAX; Levantamento de Dados; Análise Gráfica de Correlações; Análise de Séries Temporais; Análise de Gráfica de wavelets e Análise de correlação em Mapas georreferenciados. Esses procedimentos são necessários para visualizar-se com clareza o histórico embutido nas informações analisadas e uma melhor compreensão para a fase de modelagem com o método SARIMAX. Os resultados indicam que o modelo SARIMAX, com variáveis macroclimáticas, é melhor que o NEWAVE. / Renewable energy sources represent alternatives to the mitigation of global climate change, but they are more susceptible to changing on weather conditions. The Brazilian electricity system has the peculiarity that most of its energy is generated from renewable sources, mainly by hydroelectric plants. For this reason, it provides a representative sample of the difficulties for operating a predominantly renewable basis energy matrix. On one hand, the main hydroelectric generation allows low emissions and low operating costs; on the other hand, the heavy dependence on hydropower involves considerable hydrological risks, specially in an environment where restrictions on energy storage (large dams) are high. Thus, the combination of inadequate investment in generation capacity with low rainfall may, eventually, lead to situations in which the supply capacity is less than the demand, leading even rationing (2002). It is then clear that the ability to accurately predict the rainfall index and hence flow rates available for the next period is an important tool for the operation of the Brazilian electric sector (SEB). Presently, future flows forecasting are only based on observation of past flows without incorporating the analysis of the variables that determine such flows (e.g. climate variables). However, there are evidences that the variability of flows in South America is punctuated by coupled ocean-atmosphere type systems, the so-called large-scale phenomena such as El Niño. However, the traditional forecasting techniques still do not use climate information in a systematic way. The methodology presented here incorporates weather information for decision making in water resources, and demonstrates its applicability to the Southeastern region of Brazil. It is showed that the use of climatic variables (particularly those related to the El Niño phenomenon) predicts streamflow forecasting as well as the official programs do, with the advantage of following eminent climate change. The proposed methodology is formed of the following parts, not necessarily in this order: Model SARIMAX; Data Collection; Graphic analysis of correlations; Time Series Analysis; Wavelets Graphical analysis and Correlation analysis of geo-referenced maps. These procedures are necessary to clearly see the embedded historical information of the information analyzed and better understanding of the modeling stage with SARIMAX method. The results indicate that the SARIMAX model, with large scale variables, is better than the NEWAVE.

A bacia hidrográfica do Rio Grande de Ubatuba (26Km2) encontra-se quase que totalmente recoberta com vegetação nativa da Mata Atlântica, e grande parte está inserida no interior do Parque Estadual da Serra do Mar. O Rio Grande é um manancial estratégico para o município, pois abastece 88% da população, que recebe água tratada de serviço público. Com o propósito de conhecer a potencialidade hídrica do manancial de forma a subsidiar tecnicamente a elaboração do Plano de Manejo para a bacia, o presente estudo foi conduzido para gerar a série histórica de vazão, usando o Modelo SMAP (Soil Moisture Accounting Procedure) e analisar o balanço entre a disponibilidade e a demanda de água. Com apenas quatro anos incompletos de dados fluviométricos e com a série histórica de 67 anos de dados de precipitação, foi possível calibrar os parâmetros e validar o modelo com uma correlação de 0,838 entre as vazões estimada e observada e por último gerar a serie histórica de vazão. Com a série histórica de vazão gerada foi feita a análise temporal do balanço entre a disponibilidade e demanda que permitiram identificar a insuficiência hídrica para atender a demanda para abastecimento público ou para manutenção dos processos ecológicos do manancial, considerando três aspectos: a flutuação da população, a ocorrência de anos hídricos secos e, mesmo nos anos hídricos normais, ocorrência de períodos de meses secos prolongados. Com base na análise conjunta dos resultados, algumas ações consideradas compatíveis para a prevenção de possível escassez de água no futuro foram formuladas, visando proporcionar melhor qualidade de vida à população. / The Rio Grande Watershed of Ubatuba (26km2 ) is almost completely covered with native Atlantic Rainforest vegetation, and a large part is within the bounds of the Serra do Mar State Park. The Rio Grande is a strategic water source for the municipality, supplying 88% of the population demand with treated water via a public service. In order to analyse the water potential of the source and to acquire technical information for the preparation of the Watershed Management Plan, this study was carried generate streamflow historic data, using the SMAP (Soil Moisture Accounting Procedure) model. This, in turn, permitted to analyse the balance between demand and availability of water.With only 4 years of incomplete streamflow data and 67 years of rainfall data, it was possible to calibrate the parameters and validate the model with a correlation of 0.838 between the estimated and observed flows, and finally produce a streamflow history.To produce the streamflow history, a time analysis was carried out with the balance between availability and demand, which allowed the identification of water shortages for public supply, as well as for the maintenance of the stream ecological processes, considering the following three aspects: population fluctuations, the occurrence of drought years and, even in normal years, the occurrence of extended periods of drought.

Este trabalho aborda o problema de modelagem de séries de vazões afluentes aos aproveitamentos hidrelétricos. A previsão de vazão natural fluvial é realizada semanalmente para 158 usinas hidrelétricas do Sistema Interligado Nacional (SIN), pois trata-se de insumo fundamental para o planejamento e operação do sistema elétrico brasileiro. Diversos modelos são utilizados na determinação destas previsões, entre os quais podem ser citados os modelos físicos, os estatísticos e aqueles que aplicam sistemas inteligentes. Apesar de contínuos aprimoramentos terem sido incorporados ao processo de previsão de vazão, existem alguns aproveitamentos hidrelétricos para os quais os resultados de estimação têm apresentado grandes desvios. Neste contexto, com a motivação de se obter uma resposta acurada, investigam-se os sistemas fuzzy como modelos concorrentes aplicados à previsão de vazões semanais. O objetivo do trabalho é reduzir os erros de estimação para uma usina piloto, incorporando à previsão de vazão os dados de precipitação. Para a construção da série histórica de precipitação média da bacia hidrográfica, fez-se uma exaustiva pesquisa por estações pluviométricas, seguida por tratamento de dados de medição e método de interpolação. Ao final do trabalho, é apresentada uma análise comparativa entre os resultados obtidos com o Modelo Autorregressivo Periódico (PAR) e o sistema de inferência fuzzy. Com base no desempenho observado, superior ao modelo autorregressivo, comprova-se a adequação do modelo proposto para a modelagem do processo hidrológico. / This work addresses the modelling problem of hydropower plants reservoir streamflow series. The natural streamflow forecasting for 157 hydroelectric power plants of the National Interconnected System - NIS is updated on a weekly basis, which is an essential input for the planning and operation of the Brazilian Electric Power System. Several models are used to determine this prediction, such as physicals, statisticals and the ones that use intelligent systems. Despite the improvements to natural streamflow forecasting, substantial deviation has been found for the expected results of some hydropower plants. Highlighted the importance of this variable, fuzzy systems applied to weekly streamflows forecasts will be investigated as alternative models, in order to obtain better results. The purpose of this work is to reduce the estimation errors for a pilot hydropower plant, incorporating precipitation data into the forecast. Therefore, an exhaustive research to acquire data from hydrometeorological stations was conducted. After being treated, a variable selection method was applied to the data, defining the most relevant input variables for the prediction model. At the end, a comparative analysis shows that the fuzzy model presents a better performance than the periodic autoregressive model used by ONS to plan the operation of the electric power system.

Neste estudo, trata-se de avaliar fontes de precipitação baseadas em estimativas por satélite e técnicas de assimilação de dados para previsão de vazões por meio do modelo hidrológico distribuído MGB-IPH. A insuficiente representatividade espacial dos pluviômetros torna difícil a correta representação dos campos de precipitações. Por outro lado, as estimativas de satélite, embora forneçam uma descrição espacial mais consistente, são potencialmente menos acuradas. Sendo assim, procura-se utilizar métodos que combinem os dados de ambas as fontes para gerar um campo de precipitação mais consistente. Neste trabalho, implementaramse dois modelos de combinação pluviômetro-satélite, CHUVSAT e MERGEHQ, através de uma metodologia de interpolação. Por outro lado, as técnicas de assimilação de dados acoplados aos modelos de previsão hidrológica são também de interesse neste estudo, pois minimizam as incertezas associadas ao processo de calibração de parâmetros, às variáveis de estado e dados de entrada do modelo hidrológico. Para esse propósito, escolheu-se a bacia do rio Tocantins e implementou-se particularmente a técnica de assimilação de dados de tipo sequencial chamado na literatura de filtro de partículas, conjuntamente com o método de filtro Kalman por conjunto e o método de assimilação AsMGB atualmente acoplado ao modelo MGB-IPH. O estudo mostra que a precipitação combinada utilizada como dado de entrada na simulação hidrológica permitiu reproduzir adequadamente os hidrogramas observados para o período de calibração e validação. Já para o caso das vazões resultantes, durante a etapa de previsão, a precipitação combinada mostrou-se com melhor desempenho em termos estatísticos que os métodos sem combinar, sobretudo após 24 horas de antecedência. Finalmente, a técnica de assimilação de dados por filtro de partículas conseguiu absorver os erros da simulação melhorando as medidas de desempenho na etapa de previsão sendo superior ao modelo de previsão sem considerar assimilação. / The objective of this study is to evaluate precipitation sources based on satellite estimates and data assimilation techniques for prediction of flows by means of the distributed hydrological model MGB-IPH. The insufficient spatial availability of rain gauges makes difficult to represent precipitation fields appropriately. In contrast, satellite estimates, although providing a more consistent spatial description, are potentially less accurate. Thus, raingauge satellite merging methods that combine data from both sources to generate a more consistent precipitation field are used herein. For this purpose, two models namely CHUVSAT and MERGEHQ were implemented using an interpolation technique. On the other hand, data assimilation techniques coupled with hydrological forecasting models are also assessed in this study. The assimilation process minimizes the uncertainties associated with the parameter calibration procedure, variable state and hydrological input data. In this manner, the sequential data assimilation technique namely particle filter in conjunction with the Kalman filter method and the assimilation method AsMGB, which is currently coupled to the MGBIPH model, were implemented and applied to the Tocantis basin. The obtained results showed that the combined precipitation used as input data in the hydrological simulation allowed reproducing adequately the observed hydrograms for the periods of calibration and validation. In the case of the resulting flows during the forecast stage, the merging precipitation was shown to perform better in statistical terms than the uncombined methods, especially after 24 hours in advance. Finally, the data assimilation technique by particle filter was able to absorb all simulation errors, improving the performance measures in the forecasting stage, thus being superior to the forecasting model without considering assimilation.