Reservoir sediment flushing is increasingly considered beneficial to reduce sedimentation of reservoirs and maintain sediment supply downstream of impounded rivers. Nevertheless, flushing of the accumulated sediments downstream of the dam also bears numerous negative impacts. In this study, first the most important downstream impacts of fine sediment releases of flushing were identified based on previously published research of twenty case studies in eleven countries. The results showed that the long-term as well as short term biological and physical impacts decreased with distance from the dam. The temporal scale of impacts on macro-invertebrates could span from few weeks or a month to several months while the effect on fish could last for a number of years. The impacts on downstream vegetation dynamics is driven by many years of flushing activities. The study also enabled proposing generic management strategies aimed to reduce the impacts. Second, fine sediment transport in coarse immobile bed, which is a common phenomenon downstream of dams during flushing releases, dam removal and also in many mountain and canyon rivers, was investigated. Particularly, the dynamics of the downstream erosion and transport of fine sediments released during sediment flushing was investigated based on a series of flume experiments that were carried out in immobile gravel bed and using a one-dimensional (1-D) suspended sediment transport model developed in the present study. In the framework of the flume experiment, firstly gravel bed roughness, porosity and roughness density were exclusively extracted from gravel surface elevation data in which developing a spatial filter to overcome elevation errors was carried out. Secondly a new technique to acquire fine sediment erosion in immobile coarse bed in running water condition was developed. The method proved to be the back bone of all fine sediment erosion experiments conducted in the present study and could be used for similar studies. This study presents a first work of direct measurement of erosion rate and characterizing its spatial heterogeneity in gravel bed. The experimental data of erosion rate of fine sediments showed that it varied spatially with high erosion rate on the stoss side of gravels and less on the lee side conforming to sweeps and ejections characteristics in coherent flow structure of gravel bed flows. Erosion rate was significantly affected by increase in roughness of immobile gravel bed with high erosion rate noticed when sand level was reduced although the effect on stream-wise velocity was not significant. The vertical profile of erosion rate was found to decrease linearly and showed an exponential decay in time in the gravel matrix. Third, a new non-equilibrium erosion rate relation is proposed. Drag force profile in the interfacial sublayer of clean gravel bed was found to be scaled well with roughness density and allowed predicting the effective shear stress distribution available for fine sediment entrainment with an empirical equation. vi The new relation is a modified version of the pick-up rate function of van Rijn (1984b) in which the predicted shear stress in the roughness layer was implemented. The most important finding was that if the shear stress distribution in the interfacial sublayer is predicted, a relation for sand bed condition can be applied to predict fine sediment erosion rate in immobile gravel bed. This approach is conceptually superior to previous approaches where erosion rate in sand bed condition was scaled empirically for various fine sediment bed level within the interfacial sublayer. Finally, the effect of the interaction between hydrodynamic and sediment wave dynamics of sediment flushing on spatial pattern of sediment deposition was investigated. The 1-D model was developed to include major processes observed in sediment flushing: sediment wave celerity correction, variable bed roughness, bed exchange in immobile bed, hindered settling velocity and rough bed porosity. The proposed erosion rate relation showed encouraging results when implemented in the 1-D model. The wave celerity factor did not show significant effect on the spatial lag in immobile bed condition although was significant in sand bed condition. Variable bed roughness modified both the flow field and sediment deposition in which larger length of sediment deposit was noted. The immobile bed porosity allowed modelling clogged depth of fine sediments. The model was also found to be very valuable to investigate flushing scenarios that reduce significant deposition through the analysis of the dependence of deposition on peak-to-base flow and intermittence of releases. The highest peak-to-base flows produced the longest and thickest region of deposition while those with the lowest ratio produced the shortest and thinnest. A single flushing release followed by clear water release reduced area or length of sediment deposition more than intermittent flushing followed by inter- and post-flushing clear water releases. In the latter case, the peak of concentration reduced but remained higher for longer duration than the former, which suggests that a large quantity of clear water release has to be available. Overall, the present research represents a step forward in understanding relevant processes involved in the downstream transport of fine sediments released during sediment flushing and the associated impacts that can help the development of better management strategies and predictive tools.

Orientador: José Eduardo Zaine / Banca: Antonio Roberto Saad / Banca: Edson Gomes de Oliveira / Banca: José Luiz Albuquerque Filho / Banca: Fábio Augusto Vieira Reis / Resumo: O mapeamento geológico-geotécnico em áreas urbanas foi utilizado na análise das características do meio físico e processos geológicos, avaliando suas limitações e potencialidades como subsídio à gestão e ao planejamento municipal. A Bacia do Rio Bacanga, localizada na Ilha do Maranhão, no município de São Luis-Maranhão (Brasil), apresenta uma área de 106 km2 que através dos tempos vem passando por um dinâmico processo de ocupação de forma não planejadas, provocando diversos impactos ambientais como assoreamento dos mangues, desmatamentos, aterramentos, impermeabilizações do solo, erosão, contaminação da água, inundações e outros. Os recursos hídricos genuinamente luduvicense são estratégicos para a Ilha oceânica, como reservas que precisam ser preservadas por se tratar de um ecossistema frágil. O estudo foi realizado através do método do detalhamento progressivo (análise do geral para o particular) para determinação e avaliação de áreas vulneráveis a contaminação do solo e da água no Reservatório Batatã. Na etapa geral do método foi elaborado o mapa geológico-geotécnico na escala 1:20.000 onde foram individualizada 6 unidades no terreno. Na etapa de semi-detalhe a pesquisa se direcionou para o estudo da vulnerabilidade natural à contaminação do solo e aqüífero do Reservatório Batatã e entorno. Nesta etapa, os estudos enfocaram uma área de 6,6 km2, para a qual foram geradas cartas na escala de 1:10.000: de declividade, de profundidade do nível de água subterrânea, de superfície potenciométrica do aqüífero livre Barreiras, de material inconsolidado e de uso e ocupação do solo. Nesta etapa, utilizou-se o método de avaliação da vulnerabilidade natural GOD utilizando-se as informações das cartas de unidades de material inconsolidado e da profundidade do nível de água subterrânea sendo gerado o mapa de vulnerabilidade... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The geological-geotechnical mapping in urban areas was used in the analysis of the environment characteristics and geological processes, evaluating its limitations and potentialities as subsidy to the municipal management and planning. The Basin of the river Bacanga is located in the Maranhão lsland, in the city of São Luis - Maranhão (northeast of Brazil) and presents an area of 106 km2. lt has been passing through a dynamic process of non-planned human occupation which has caused many impacts as mangroves landfill environmental in region, deforestation, ground waterproofing, erosion, water contamination, flooding and others. Local water resources constitute a fragile ecosystem but a strategic one for such an oceanic island. Therefore, it must be preserved. The study was done through the method of the gradual detailing (it analyzes first the general aspects and afterwards the specific ones) for determination in the Batatã Reservoir. On Lhe first and most general step, a 1:20.000 scale geologic-geotechnical map was made, on where six land units were set up. The semi-detailed step studied the natural vulnerability to ground and aquifer contaminaton of the Batatã Reservoir and its surroundings. Such stage focused a 6.6 km2 area for which 1:10.000 scale charts were generated: declivity, underground water level depth, potentiometric surface, unconsolidated material and ground occupation. At this phase, the GOD natural vulnerability evaluation approach was used, and then information from the land unit charts of unconsolidated material and underground water level depth was utilized, resulting a map of natural vulnerability concerned to the contamination of ground and aquifer. The map of ground occupation was overlapped on the natural vulnerability map, resulting a map of natural vulnerability and potential contamination of the ground and aquifer of the Batatã Reservoir... (Complete abstract, click electronic address below) / Doutor

No Brasil, cerca de dois terços da capacidade total instalada de geração de energia elétrica e, em média nos últimos quinze anos, aproximadamente 90% da geração efetiva provêm das hidrelétricas. Este sistema inclui 170 usinas hidrelétricas de médio e grande porte existentes ou previstas até 2023, aproximadamente dois terços delas com capacidade de regularizar vazões e todas operando de maneira interligada. Restrições ambientais, técnicas, sociais e econômicas tem dificultado cada vez mais a implantação de empreendimentos hidráulicos contendo reservatórios de grande porte, tornando a maioria dos novos empreendimentos a fio d´água. Para compreender melhor o processo, este trabalho apresenta um levantamento da evolução anual da capacidade instalada e de armazenamento do sistema desde 1950 até a expansão prevista nos próximos 8 anos, em 2023. Os dados da década de 2000 e a previsão até 2023 de forma ainda mais acentuada indicam uma redução continua e significativa da capacidade relativa de regularização, com impacto direto nas decisões de operação e de expansão do sistema térmico complementar. A fim de avaliar as possíveis consequências da redução da capacidade de regularização, simulações foram realizadas no modelo HIDROTERM (ZAMBON et al. 2012); os resultados apontam para uma necessidade de ser complementar continuamente a energia hídrica, não só em períodos hidrologicamente desfavoráveis. / In Brazil, about two-thirds of electricity installed capacity and over the last fifteen years, on average 90% of energy consumed has come from hydropower generation. The hydro system includes 170 medium and large hydropower plants in integrated operation today or planned to be operational by the end of 2023, about two-thirds of them have large storage capacities to regulate flows. Environmental, technical, social and economic constraints have made it increasingly difficult to project and build new reservoirs with large storage capacities. As a result, newly built hydropower plants are mostly the run-of-river type. To better understand the process, this paper presents a historical survey of the installed capacity of hydropower and storage capacity of the system since 1950 and extends to the planned expansion over the next eight years, through 2023. Data from 2000 and projections through 2023 indicate a significant reduction of relative regulating capacity, which has a direct impact on decisions regarding operation and expansion of the complementary thermal system. In order to assess the possible consequences of the reduction in regulating capacity, simulations were performed on HIDROTERM model (ZAMBON et al. 2012); the simulation results point to a continuous need for complementing the hydropower generation, not only on hydrologically unfavorable years.

Micropores can constitute up to 100% of the total porosity within carbonate hosted hydrocarbon reservoirs, usually existing within micritic fabrics. There is, however, only a rudimentary understanding of the contribution that these pores make to reservoir performance and hydrocarbon recovery. To further our understanding, a flexible, object-based algorithm has been developed to produce 3D computational representations of end-point micritic fabrics. By methodically altering model parameters, the state-space of microporous carbonates is explored. Flow properties are quantified using lattice-Boltzmann and network modelling methods. In purely micritic fabrics, it has been observed that average pore radius has a positive correlation with single-phase permeability and results in decreasing residual oil saturations under both water-wet and 50% fractionally oil-wet states. Similarly, permeability increases by an order of magnitude (from 0.6md to 7.5md) within fabrics of varying total matrix porosity (from 18% to 35%) due to increasing pore size, but this has minimal effect on multi-phase flow. Increased pore size due to micrite rounding notably increases permeability in comparison to original rhombic fabrics with the same porosity, but again, multi-phase flow properties are unaffected. The wetting state of these fabrics, however, can strongly influence multi-phase flow; residual oil saturations vary from 30% for a water-wet state and up to 50% for an 80% oil wet fraction. flow when directly connected. Otherwise, micropores control single-phase permeability magnitude. Importantly in these fabrics, recovery is dependent on both wetting scenario and pore-network homogeneity; under water-wet imbibition, increasing proportions of microporosity yield lower residual oil saturations. Finally, in grain-based fabrics where mesopores form an independently connected pore network, micropores do not affect permeability, even when they constitute up to 50% of the total porosity. Through examination of these three styles of microporous carbonates, it is apparent that micropores can have a significant impact on flow and sweep characteristics in such fabrics.

The dissertation thesis is focused on pelagic fish distribution in the large freshwater bodies and the main factors affecting it. Paper 1 describes fish behaviour in a mouth of a midwater trawl during different day time periods as fish activity may importantly affect abundance estimates of the sampled fish stock. Acoustically recorded avoidance behaviour in a vertical direction is described. The second part of the thesis refers to the diel distribution and behaviour of the pelagic fry communities with a particular focus on the vertically migrating bathypelagic percid fry that occupy open water during early ontogeny. Paper 2 shows that the vertically migrating community can create a dominant part of fry assemblages in the reservoir, which is in contrast to many previous observations of an usually prevailing non-migrating epipelagic community. At their day refuge, bathypelagic percid fry (BPF) created dense shoals whose physical parameters are described. Paper 3 for the first time demonstrates that vertical shifts of BPF were under direct light control, hence were not a genetically fixed behaviour. A unique large-scale field experiment with the simultaneously operating up-looking and down looking transducers was carried out under artificially controlled light regime. Moreover effect of predation as the main ultimate cause of vertical shifts is discussed. The introductory part of the thesis opens with the current possibilities of assessing distribution and behaviour of fish in the open water. Benefits of shoaling/schooling behaviour during defence against predators, foraging and learning abilities of fish are mentioned and some implications of fish behaviour on the fish capture process are pointed out. The second chapter deals with the diel shifts between habitats that belong among the most common activities of fish. However, distribution of fish varies also over the long temporal scale and currently has been strongly affected by changing climate. Therefore, the main affects of climate change on the world´s fish populations are introduced using examples from both freshwater and marine environment.

Surface air pressure differentials that occur over reservoirs, canals, and water-catchment aprons in high-wind conditions were determined by the use of models in a wind tunnel. Such information was needed concerning the magnitude and location of destructive wind forces on water barriers constructed of exposed flexible membrane liners. Rigid models, without a membrane, were used to measure airpressure differentials. Air-pressure differentials were dependent on geometric configuration and were independent of viccous forces above the critical Reynolds number which was determined experimentally. The geometric factors studied with respect to reservoirs and canals included approach slope, approach slope length, leeward slope, and breadth-depth ratio. Those pertaining to water-catchment aprons included breadth-berm height ratio and berm shape. On the leeward slope of reservoirs, favorable (positive) differential pressures were more apt to occur as the approach and leeward slopes decreased (became less steep), but extreme adverse (negative) pressures occurred under the same conditions near the top edge of the slope. As the leeward slope increased the pressure coefficient values were essentially constant over the entire surface. On the reservoir bottom, adverse pressures did not exist when approach and leeward slopes were at the minimum evaluated (1:4). When the leeward and approach slopes increased the average pressure on the bottom became less favorable. The most adverse pressure coefficients generally occurred at the toe of the leeward slope, while maximum favorable pressures on the reservoir bottom generally occurred at the toe of the downwind slope. In most instances, the pressure on the downwind slope was favorable; however, adverse pressures were recorded near the top edge of the slope. These adverse or negative pressure conditions were more apt to occur as the breadth-depth ratio increased and the leeward slope decreased. Average pressure values on the interior surface of canals were generally less adverse than for reservoirs. Similar to the reservoirs, the most adverse pressures on the leeward slope of the canals were found immediately over the upper edge of the slope. Extreme adverse pressures on the canal bottom were associated with long and steep approach slope conditions. One exception was the occurrence of the most favorable pressure over the canal bottom when the approach slope was short but still steep. In addition to measurement of adverse pressures near the top edge of the downwind slope, adverse pressures were found near the toe of the slope in some instances. The portion of the downwind slope under an adverse pressure influence decreased as the breadth-depth ratio increased. Generally, pressures over a canal were more responsive to the approach slope and approach slope height than to leeward slope arid breadth-depth ratio. For a reservoir, however, pressures were responsive to all geometric factors, depending on which section of the reservoir was being considered. Pressure distributions over water-catchment aprons were independent of breadth-berm height ratios of 50 or greater. Negative pressures were lower over gradual sloped catchment berms by a factor of three than over sine-shaped berms. Each berm shape, on the leeward side of the upwind berm, had a pressure distribution associated with it that was the same as far as shape but was different in magnitude depending on the shape of the windward side of the berm. Pressures were less adverse on the leeward side of the berm, if the windward side were gradually sloped. Pressures were near zero to slightly favorable over a large portion of the water-catchment apron between the berm toes. This near stable favorable condition might change significantly, if site conditions were to change.

"March 2004" / Bibliography: leaves 221-234. / xxiv, 249 leaves : ill. (some col.), maps, photos (col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This research is part of the SA Water and Cooperative Centre for Water Quality and Treatment project entitled Destratification for control of phyloplankton. The major objective of this project was to assess a novel method of destratification and control of cyanobacteria, in particular Anabaena circinalis Rabenh. ex Born. et Flah, with the use of raft-mounted mechanical surface mixers with draft-tubes. / Thesis (Ph.D.)--University of Adelaide, School of Civil and Environmental Engineering, 2004

Thesis (Ph. D.)--University of Wyoming, 2006. / Title from PDF title page (viewed on Dec. 20, 2007). Includes bibliographical references (p. 208-216).

Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains xx, 159 p. : ill. (some col.), map. Includes abstract. Includes bibliographical references (p. 64-65).

Thesis (M.S.)--Brigham Young University. Dept. of Chemical Engineering, 2005. / Includes bibliographical references (p. 159-161).