Hydropower is a more environmental friendly way of producing electric power than many other alternatives today. Though, the effects of constructing mega dams are much tangible for the local eco systems in addition to changing many people’s lives forever. In order to prevent floods, riverbank erosions or landslides, proper investigations of the environmental impact from dam constructions must be performed. One of the key parameters in such investigations is the flow discharge velocity. This master thesis treats experimental measurements and numerical simulations of the velocity downstream a model of Xiluodu dam. The Xiluodu dam is a mega dam under construction in China and will have a total capacity of 12 600 MW when completed. The model is in scale 1:100 and the experiments have been performed at Department of Hydraulic Engineering, Tsinghua University, Beijing, China. The velocity profile shows that the velocity in the middle of the river is larger than the velocity at the surface and near the riverbank. The comparison between the measured and the simulated velocities shows a difference of less than 20 percent in almost all points which can be considered as a good result. In those points where the difference is more than 20 percent, this is believed to be due to the position of these points. Some of them were located near a vortex and others very close to the bottom. This is a problem when sparsely measured topography in combination with linear interpolation makes the boundaries of the simulations incorrect. In order to perform better simulations, more densely topography data and better flow boundary conditions should be used. More measuring points of the velocity could also improve the result.

Made available in DSpace on 2014-07-29T15:01:40Z (GMT). No. of bitstreams: 1 Viniciu Fagundes Barbara em PDF.pdf: 2483097 bytes, checksum: 5b34f64b65562b6c494035ae3e2630ee (MD5) Previous issue date: 2006-12-12 / The current investigation presents a characterization of the hydraulics and water quality of the medium course of the Araguari River, State of Amapá, Brazil, which has an approximate extension of 120 km. The Araguari River is the main water resource of the State of Amapá, located in the domains of the Amazon (the greatest tropical forest of the planet) in a region with great hydropower potential. In the studied river stretch, there is a hydropower generation station called Coaracy Nunes (UHECN), the first barrage build in the Amazon for electrical generation. A model for DO and BOD has been built with the help of the QUAL2E modeling system, developed by the United States Environmental Protection Agency. For this purpose, during one and a half year, field trips have been conducted with the intent of characterizing spacially and seasonally the hydraulics, kinetics and water quality of the Araguari River. The modeling stages involved model construction, sensitivity analisys and calibration. After model calibration, three hypothetic cenarios were simulated: (1) the introduction of a new barrage upstream of the UHECN; (2) municipal untreated wastewater inflow from Porto Grande and Ferreira Gomes into the waterbody, including populational growth, during the high flow period; (3) the same cenario as before but during the low flow period. The carbonaceous organic matter present in water hás shown to decompose, in average, in the first five days of incubation. The values obtained for the BOD first order reaction coefficient layed between 0,13 d-1 and 0,90 d-1. The reaeration coefficient, K2, estimated based on hydraulic characteristics, layed between 0,01 d-1 and 1,40 d-1. The results of the sample collections in the river stretch has shown that, amongst the parameters measured, the following were mostly altered: pH, electric conductivity, total solids, suspended solids, fecal coliforms, ammonium, nitrate, BOD and DO. Fecal coliforms, pH, nitrate and BOD were in disagreement with limits defined by Brazilian Legislation on water quality (CONAMA 357/2005). The river impoundment has shown not to significantly alter the DO and BOD concentrations, however, the same statement can not be made for other water characteristics. The water characteristics mostly altered by the UHECN were: hydraulic (flow, velocity, breadth, cross-sectional area) and water quality (pH, electric conductivity, water temperature, total solids, suspended solids, fecal coliforms, nitrate, chloride, BOD and DO). The simulated scenario with municipal untreated wastewater inflow from Porto Grande and Ferreira Gomes (including population growth) into the waterbody during low flow period showed the most critical results in terms of the water quality. The worst simulated situation happened in the dry period in which the river flows decreased significantly and so did the river dilution capacity. In this period the greatest OD depletion occurred and achieved concentrations bellow 4.0 mg/L, in disagreement with Brazilian Water Quality Legislation (CONAMA 357/2005). / A presente investigação apresenta uma caracterização hidráulica e da qualidade da água do médio curso do Rio Araguari (AP), em uma extensão de aproximadamente 120 km. O Rio Araguari, principal corpo hídrico do Estado do Amapá, está situado dentro dos domínios da Amazônia (a maior floresta tropical do planeta), em uma região com grande potencial hidrelétrico. No trecho em estudo, encontra-se implantada a Usina Hidrelétrica de Coaracy Nunes (UHECN), a primeira barragem edificada na Amazônia com fins de geração de energia elétrica. Foi desenvolvido um modelo de oxigênio dissolvido (OD) e de demanda bioquímica de oxigênio (DBO) com o auxílio do sistema de modelagem QUAL2E, desenvolvido pela Agência de Proteção Ambiental dos Estados Unidos (USEPA). Para isso, procedeu-se, durante um ano e meio, com expedições de campo que objetivaram caracterizar, espacialmente e sazonalmente, os parâmetros hidráulicos, cinéticos e de qualidade da água do Rio Araguari. As etapas da modelagem envolveram a construção, análise de sensibilidade e a calibração do modelo. Posteriormente efetuou-se, com o modelo calibrado, a simulação de três cenários hipotéticos na bacia: (1) a introdução de uma nova barragem a montante da UHECN; (2) o descarte de efluentes in natura oriundos dos municípios de Porto Grande e Ferreira Gomes (com crescimento populacional) nas águas do corpo hídrico (período de alta vazão); e (3) o mesmo cenário anterior, porém para a condição de baixas vazões. A matéria orgânica carbonácea presente na água desse rio decompõe-se, em média, nos primeiros cinco dias de incubação. Os valores obtidos experimentalmente para o coeficiente de deoxigenação, K1, ficaram compreendidos entre 0,13 d-1 e 0,90 d-1. O coeficiente de reaeração, K2, obtido com base nas características hidráulicas, ficaram compreendidos entre 0,01 d-1 a 1,40 d-1. Os resultados das campanhas amostrais mostraram que os parâmetros de qualidade da água que se apresentaram mais alterados no trecho em estudo foram: potencial hidrogeniônico, condutividade, sólidos totais, sólidos suspensos, coliformes termotolerantes, amônia, nitrato, demanda bioquímica de oxigênio e oxigênio dissolvido. Quando comparados com a Resolução 357/2005 do Conselho Nacional de Meio Ambiente (CONAMA), os parâmetros que mais infringiram esse instrumento jurídico foram: potencial hidrogeniônico, coliformes termotolerantes, nitrato e demanda bioquímica de oxigênio. A nova barragem não interfere significativamente as concentrações de OD e DBO do Rio Araguari, não se podendo fazer a mesma afirmação para os demais parâmetros de qualidade da água. As características que mais se alteraram devido à obra da UHECN foram: hidráulicas (vazão, velocidade, largura e área da seção transversal), e de qualidade da água (potencial hidrogeniônico, condutividade, temperatura da água, sólidos totais, sólidos suspensos, coliformes termotolerantes, nitrato, cloreto, demanda bioquímica de oxigênio e oxigênio dissolvido). O cenário simulado com o descarte nas águas do manancial de efluentes in natura dos municípios de Porto Grande e Ferreira Gomes, com o crescimento populacional, no período das baixas vazões, foi o mais desfavorável dentre os cenários investigados com relação à qualidade da água. A pior situação aconteceu na época das estiagens, em que as vazões do curso d água diminuem consideravelmente e, consequentemente, sua capacidade de diluição também. Neste período, ocorreu uma maior depleção do oxigênio dissolvido presente na água, que alcançou concentrações abaixo de 4,00 mg/L, vindo a infringir a Resolução 357/2005 do CONAMA.

The content of this diploma thesis is a feasibility study of a small hydropower station within the navigation lock Přelouč II. This work builds on the framework proposal of one variation of layout arragement of the navigation lock. In this variant is considered to build a lock, which also includes a small hydropower station. At the beginning, the location of individual building objects is resolved with respect to the conditions in the locality. This is followed by a more detailed development of the building and technological part of a small hydropower plant. Part of the thesis is accompanying and technical report, drawing documentation, hydrotechnical and hydroenergetic calculations and photographic documentation.

Sediment-related issues in reservoirs can often pose significant challenges to their operational effectiveness, sustainability, and environmental impact. Sustainable sediment management can help resolve these issues and extend the lifespan of dams. The reservoir in Andakílsá river in west Iceland is one out of many reservoirs that has experienced sediment-related problems, and in this study, it was evaluated whether a particular sediment management solution called SediCon Sluicer could be a suitable solution for the site. More specifically, evaluate whether the river transport capacity is sufficient to transport the sediments released from the SediCon Sluicer outlet pipe, so they don’t settle and form thick deposit layers in the river bottom. A hydraulic model of the river was set up in a two-dimensional HEC-RAS model (version 6.3.1) and the Manning’s roughness coefficient in the channel calibrated using water level data. The Manning’s value 0.025 was found to best describe the channel roughness. A HEC-RAS 2D Sediment Transport model was then used to simulate different amount of sediments being released into the river for different flow scenarios. A flood event with 95% confidence level to occur once a year was found to have a peak flow of 50 m3/s and have a duration of around 18 hours. However, the average peak flow from the biggest flood events during a 14-year period was found to be 118 m3/s, and that type of flood events can have a duration up to 70 hours. The results from the sediment simulation scenarios showed that for flood events with long duration and high discharge, the yearly accumulated sediments could most likely all be flushed once a year without too much deposit in the river. A shorter flood event, that is almost certain to occur once a year, is not likely to be able to flush out all the yearly accumulated sediments all at once. Perhaps the SediCon sluicer could be operated several times a year, but a more detailed flow frequency analysis must reveal what smaller floods can be expected yearly. This solution could be a suitable option for the river, but more research and analysis need to be performed for a better certainty on the optimal operational range. / Sedimentrelaterade problem i reservoarer kan ofta utgöra betydande utmaningar för vattensystemets effektivitet, hållbarhet och miljöpåverkan. Hållbar sedimenthantering kan hjälpa till att lösa dessa problem och förlänga dammarnas livslängd. Reservoaren i Andakílsá-floden på västra Island är en av många reservoarer som har upplevt sedimentrelaterade problem, och i denna studie utvärderades om en specifik sedimenthanteringslösning kallad SediCon Sluicer kunde vara en lämplig lösning för platsen. Mer specifikt, utvärdera om flodens transportkapacitet på nedströmssidan om reservoaren är tillräcklig för att transportera sedimenten som frigörs från SediCon Sluicers utloppsrör, så att de inte sätter sig och bildar tjocka avlagringslager i flod-botten. En modell över hydraulik och sedimenttransport i floden sattes upp i en tvådimensionell HEC-RAS-modell (version 6.3.1) och Mannings friktionskoefficient i kanalen kalibrerades med hjälp av vattennivådata. Manning-värdet 0,025 visade sig bäst beskriva kanalens grovhet. En HEC-RAS 2D Sediment Transport-modell användes sedan för att simulera olika mängder sediment som släpps ut i floden för olika flödesscenarier. Resultaten från sedimentsimuleringen visade att om sediment släpptes ut en gång om året så krävs en tillräckligt varaktigt högflödesscenario för att få acceptabel transport, medan sedimenten kan avsättas i floden vid kortare händelser. SediCon Sluicer kanske skulle kunna köras flera gånger per år, men en mer detaljerad flödesfrekvensanalys måste i så fall visa vilka sekvenser av mindre översvämningar som kan förväntas årligen. Denna lösning skulle kunna vara ett lämpligt alternativ för floden, men mer forskning och analys behöver göras för att få en bättre säkerhet om det optimala driftområdet.