The main objective of this study is an assessment of the potential of applying land use optimization methods for minimizing the sediment yield from catchments. The study area is the Siran watershed, a subwatershed of the Tarbela watershed in Pakistan which drains directly into the Tarbela reservoir. It has an area of 4Ub sq. miles and receives 47.82 inches annual average precipitation. The main land use practices on the Siran Watershed are agriculture, rangeland grazing and forestry. A stochastic model for simulating daily precipitation and another for simulating daily maximum temperatures are developed for the area. The synthetic daily precipitation events are transformed into daily streamflows by the soil moisture counting streamflow model using the synthetic daily maximum temperatures as input. The streamtlow model, called the Generalized Streamflow Simulation System, is modified and used for simulating baseflow recessions. The stochastic precipitation model, the stochastic temperature model and the deterministic streamflow models were combined with the deterministic sediment yield model for simulating sediment yield from the watershed. The modified Universal Soil Loss Equation was used for simulating sediment yield. Parameters at these models were determined from data taken on the Siran Watershed. A linear program was used for land use optimization to minimize sediment yield and maximize watershed production. Both optimization processes ended up with the same land use areas allocating the Maximum area for forests. The expected sediment yield was reduced by 2.5 times and production of watershed was doubled. Optimization of crops was accomplished by maximizing the production of agriculture lands. This resulted in the allocation of major agriculture land areas for apple orchards. By adopting the final optimized land use practices, the sediment yield can be reduced to half and watershed production can be increased six times. The results of the present study are encouraging and indicate that application of land use optimization methods for reducing sediment yields nave great potential on the study area and on other subwatersheds of the Tarbela and Manyla Watersheds. The methodology developed in this study can provide a useful tool for watershed managers to reduce sediment yields and increase the income of the local inhabitants by maximizing the agriculture production in other parts of the country.

On average, one percent of reservoir storage capacity is lost annually to sediment deposition in reservoirs. Several methods for sediment removal do exist, but most are inefficient and costly in terms of money or water usage. One method known as siphoning has been shown to adequately remove sediment, but present knowledge is lacking to optimize this method for removal. Three relationships for sediment transport in a pipe were compared against data collected from a physical model resembling a reservoir siphoning system. None of the three accurately predicted the physical model results. However, some trends among the relationships were observed, indicating that with additional modification to the relationships, parameters could possibly be developed to design a prototype system.

The central objective of the study was to fractionate sedimenting organic materials according to their source (allochthonous or autochthonous) and ultimately to determine the degree of biodegradability of contributions from either source with particular reference to activities at the mud-water interface.

Thesis advisor: Noah P. Snyder / Thesis advisor: Gabrielle C. David / The Reservoir Sedimentation Database (ResSed), a catalogue of reservoirs and depositional data that has recently become publicly available, allows for rapid calculation of sedimentation and capacity-loss rates over short (annual to decadal) timescales. This study is a statistical investigation of factors controlling average sediment yield (Y) in eastern United States watersheds. I develop an ArcGIS-based model that delineates watersheds upstream of ResSed dams and calculate drainage areas to determine Y for 191 eastern US watersheds. Geomorphic, geologic, regional, climatic, and land use variables are quantified within study watersheds using GIS. Sediment yield exhibits a large amount of scatter, ranging from 4.7 to 3336 tonnes1km 2year-1. A weak inverse power law relationship between drainage area (A) and Y (R2 = 0.09) is evident, similar to other studies (e.g., Koppes and Montgomery, 2009). Linear regressions reveal no relationship between mean watershed slope (S) and Y, possibly due to the relatively low relief of the region (mean S for all watersheds is 6°). Analysis of variance shows that watersheds in formerly glaciated regions exhibit a statistically significant lower mean Y (159 tonnes1km-2year-1) than watersheds in unglaciated regions (318 tonnes1km-2year-1), while watersheds with different dam purposes show no significant differences in mean Y. Linear regressions reveal no relationships between land use parameters like percent agricultural, and percent impervious surfaces (I) and Y, but classification and regression trees indicate a threshold in highly developed regions (I > 34%) above which the mean Y (965 tonnes1km-2year-1) is four times higher than watersheds in less developed (I < 34%) regions (237 tonnes1km 2year-1). Further, interactions between land use variables emerge in formerly glaciated regions, where increased agricultural land results in higher rates of annual capacity loss in reservoirs (R2 = 0.56). Plots of Y versus timescale of measurement (e.g., Sadler and Jerolmack, 2014) show that nearly the full range of observed Y, including the highest values, are seen over short survey intervals (< 20 years), suggesting that whether or not large sedimentation events (such as floods) occur between two surveys may explain the high degree of variability in measured rates. / Thesis (MS) — Boston College, 2014. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

Despite mounting demand for a more sustainable worldwide water supply system, available reservoir capacity is relentlessly diminishing due to sedimentation. This fact, coupled with a decrease in the rate of dam construction, indicate an impending water supply dilemma. In the future, dams should be designed following a life cycle management approach rather than the typical short-sighted design life technique.Neither sustainable reservoir lifespans nor intergenerational equity is achieved through conventional cost-benefit analyses (CBA), which render all benefits and costs projected to occur more than several decades into a project as negligible. Consequently, future expenditures, including dam decommissioning or retrofitting with sediment management facilities, are regarded as non-factors in an analysis. CBAs have also historically failed to account for the impacts of sedimentation on infrastructure and the environment over time.Alternatives to the traditional application of the CBA do exist, however. These include dam owners establishing retirement funds or insurance policies, beneficiaries paying for rehabilitation or maintenance, and economists incorporating infrastructure damages and potentially declining discount rates into their analyses.To analyze the disadvantages of not managing sediment, a case study of costs caused from sedimentation impacts at Gavins Point Dam was performed. Impacts from sedimentation at Gavins Point Dam include, among many others, upstream municipal flooding and downstream bank stabilization and sandbar construction. The financial analysis considered the time value of money and showed that the value of expenditures to resolve sedimentation impacts is equivalent to 70% of the original construction cost. Including the costs of additional impacts would amplify this result. Design and operations decisions at Gavins Point Dam could have been drastically different, leading to a more sustainable project, if these expenditures from sedimentation impacts had been included in the initial economic analyses.It is recommended that multidisciplinary discussions occur at multiagency levels to consider changes to traditional CBAs for long-term water supply projects. These discussions should investigate the creation of funding to address sediment management at existing dams. The frequency of bathymetric surveys should also be increased, which would lead to a better understanding of the condition of our infrastructure. By pursuing these recommendations and integrating the aforementioned alternatives to the CBA, economic studies for reservoirs will be more accurate, reservoir lifespans will be more sustainable, profits will be extended indefinitely, and the economic burdens passed to future generations will be lessened.

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No. of bitstreams: 2 Tese - Susy Ferreira Oliveira - 2018.pdf: 9298353 bytes, checksum: 60e60c13d3a1c475932225b3ca022f41 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-05-17 / Fundação de Amparo à Pesquisa do Estado de Goiás - FAPEG / By building dams in a watercourse, the hydrosedimentometric dynamics of the water bodies changes. Due the reduction of transport energy, the particulate material transported starts being deposited, reducing the volume and the useful life of the reservoir. In order to take mitigating and preventive measures, it is necessary to diagnose the sectors with the greatest amount, volume and distribution of sediments in the area of influence. The general objective of this work was to evaluate the sedimentation stage, to detect the current depositional models and to evaluate the quality of the sediments, aiming at possible mitigation measures in relation to the sedimentation of the reservoir of the Barra dos Coqueiros hydropower plant, located on river Claro, between the municipalities of Caçu and Cachoeira Alta. In order to reach the proposed general objective, the physical characterization of the area of influence on the reservoir was carried out, from geological, geomorphological, slope, soil, climate, land use and vegetation cover aspects. And to determine the possible source areas related to erosive processes, the map of potential fragility and emergent fragility was generated. In order to understand the main sites of impact, hydrosedimentological studies were carried out through CSS, Turbidity and Water Transparency variables. The study of current depositional models was carried out from the study of facies. The quality of the sediments was evaluated by the heavy metals Cadmium, Nickel, Copper, Lead and Mercury. According to fragility analysis, 30% of the area is classified as medium and high fragility, demonstrating the need for planning and utilization of conservation practices in relation to the use and vegetation cover. By means of hydrosedimentological studies, it was noticed the reduction of CSS and Turbidity downstream, according to the velocity of water flow and depth analyzed in the bathymetric surveys, in which a reduction of 0.51% of the dead volume of the reservoir was observed. Depositional models that predominate are associated with silt/clayey facies for riverbed deposits, sandy facies for stream deposits and silt/clayey and sandy facies for delta deposits. Regarding sediment quality, it was verified that cadmium presented concentrations higher than the reference parameter determined for sediments by CONAMA Resolution 454/2012. In the soil, it was also verified that heavy metals were superior to the reference values of the resolution CONAMA 420/2009, that’s related to the natural formation of the soils and to the use and occupation of the earth. / Com a construção de barragens em um curso de água, altera-se a dinâmica hidrossedimentométrica dos corpos d’água. Com a redução da energia de transporte, o material particulado transportado passa a ser depositado, reduzindo o volume e a vida útil do reservatório. Para que medidas mitigatórias e preventivas possam ser tomadas, é preciso que sejam diagnosticados os setores com maior aporte, volume e distribuição dos sedimentos na área de influência. Neste trabalho, o objetivo geral foi avaliar o estágio de sedimentação, detectar os modelos deposicionais vigentes e avaliar a qualidade dos sedimentos, visando às possíveis tomadas de medidas mitigadoras em relação ao assoreamento do reservatório da usina hidrelétrica Barra dos Coqueiros, que se situa no rio Claro, entre os municípios de Caçu e Cachoeira Alta. Para atingir o objetivo geral proposto, foi realizada a caracterização físicas da área de influência do reservatório a partir dos aspectos geológicos, geomorfológicos, declividade, solos, clima, uso da terra e cobertura vegetal, A fim de se determinar as possíveis áreas fontes em relação aos processos erosivos, foi gerado o mapa de fragilidade potencial e fragilidade emergente. Com o intuito de se compreender os principais locais de aporte, foram realizados estudos hidrossedimentológicos. A pesquisa dos modelos deposicionais vigentes foi realizado a partir do estudo de fácies. A qualidade dos sedimentos foi avaliada quantificando os níveis dos metais pesados Cádmio, Níquel, Cobre, Chumbo e Mercúrio. De acordo com análise da fragilidade, 30% da área classifica-se em média e alta fragilidade, demonstrando a necessidade de planejamento e utilização de práticas conservacionistas em relação ao uso e cobertura vegetal. Os estudos hidrossedimentológicos demonstraram a redução das CSS e Turbidez de montante para jusante, de acordo com a velocidade de escoamento da água e profundidade analisadas nos levantamentos batimétricos, no qual foi percebida uma redução de 0,51% do volume morto do reservatório. Os modelos deposicionais que predominam são associados às fácies silte/argilosas para os depósitos de leito, fácies arenosas para os depósitos de corrente e fácies silte/argilosas e arenosas para os depósitos de delta. Quanto à qualidade dos sedimentos, verificou-se que o cádmio apresentou concentrações superior ao parâmetro de referência determinado para sedimentos pela Resolução CONAMA 454/2012. Nos solos, observou-se que os metais pesados foram superiores aos valores de referência da resolução CONAMA 420/2009, fato este relacionado à formação natural dos solos e ao uso e ocupação da terra.

>Magister Scientiae - MSc / The Bredasdorp Basin is located on the southern continental margin, off the coast of South Africa. It is mostly filled by marine Aptian to Maastrichtian deposits, overlaying pre-existing Late Jurassic to Early Cretaceous fluvial and shallow marine synrift deposits. The basin is a southeastern trending rift basin, located between the Columbine-Agulhas and Infanta arches. Its basement is made up of slates of the Bokkeveld Group (Devonian) and or quartzites of the Table Mountain Group (Ordovician-Silurian). The study area extends from X-X field to Y-Y field and encompasses only four wells for this investigation; well A, B, C and D respectively. This study was done through the interpretation; integration and juxtaposing of the results from core analysis with wireline log analysis (gamma ray) using Petrel software to display and correlate the well logs. Through core analysis which is the main source of information for this study, seven facies were identified and interpreted for the entire study. These facies alternate throughout each well and between different wells, but they are not evident in all the cores. Throughout the study, well A has been used as a reference well, since it appears (according to the interpretations) to record all seven facies and has the thickest section of zone 3. This zone reflects more accommodation space than the other studied wells at the time of deposition. Facies analysis of cores and well log correlation provide evidence that the studied USM sandstones are compatible with a wave dominated estuary/island-bar lagoon system to shoreface of a wave dominated marine shelf. It has previously been demonstrated that on the northern shelf of the Bredasdorp Basin, the USM typically has an hour-glass gamma ray log signature as a result of long-term transgression and regression and this typical log shape was also identified in this study from well A .

Reservoir sedimentation is a serious problem that threatens the water storage capacities across the world. Extending a dam's life requires adopting a new design and operational paradigm that focuses on managing the reservoir and watershed system to bring sediment inflow and outflow into balance by including reservoir sediment management facilities in dam and reservoir. However, the cost of methods that remove the sediment from reservoirs is usually prohibitive and is a serious factor preventing sustainable sediment management. This thesis considered a case study, Paonia Reservoir in Colorado, to investigate two aspects of reservoir operation, sediment management and economic assessment. The purpose is to determine how sediment management (sluicing using a low-level gate) effectively reduces sedimentation and whether this management is economically viable. The SRH-1D will be implemented to model the reservoir sedimentation, and RSEM evaluate it economically. The result comparison of current Paonia operation with hypothetical Paonia (added low-level gate) proved sluicing incoming sediment-laden flow effectively reduces sedimentation without interruption in the reservoir targeted functions like irrigating downstream. The deposited sediment volume could decrease more by monitoring the possible peak flow time and keeping the low-level gate open to pass high incoming flow downstream. This thesis applied RSEM to evaluate and compare the benefits and costs of continued sedimentation and eventual dam decommissioning (the existing Reservoir condition) to sediment management costs and benefits (hypothetical Paonia Reservoir). The results illustrated that sediment removal is advantageous because it contributed to decrease rate of decline of reservoir capacity, which made this capacity, and the associated instantaneous net benefits exceed those in the without sediment management alternative. The preserved benefits from sustainable sediment management offset the additional costs of incorporating sediment management. One of the key messages of this thesis is that incorporating sediment management into the planning and design phases of dam projects is essential for ensuring that the benefits of reservoir storage are sustained over the long term. This means fairness between current and future generations to enjoy the benefits of the facility while spreading the cost of ownership, operations, and maintenance over generations.

In this thesis, a stochastic model was utilized to predict the water content and sediment deposition characteristics in the Mazar Reservoir in Ecuador. The results obtained were compared with those reported in the project's feasibility study. The methodology used in this study was based on the assumption that annual water inflow can be taken as a random variable and annual water contents in the reservoir form an independent series of first-order, homogeneous Markov Chains. The available stream flow records indicated that normal and log-normal probability distributions would adequately characterize the annual water inflows. Using Moran's storage theory, expected values of the reservoir water contents were calculated for consecutive years until the storage probability transition matrix operation yielded a stationary condition. Annual amounts of sediment deposition in the reservoir were determined as the difference between annual sediment inflows and outflows. Two different scenarios were applied to calculate the annual sediment inflows. In the first scenario, based on the deterministic sediment rating equations, the resulting sediment rates were assigned the same probabilities as the water inflows. In the second scenario, the annual sediment rates were also considered as random variables normally distributed around the mean values. The results obtained indicated that a stochastic model, such as the one employed in this study, can be effectively used to predict sediment deposition in a reservoir to complement the predictions obtained with deterministic methods, and can even yield a more reliable spectrum of results that can be associated with various confidence levels, particularly when the data on actual sediment measurements is scarce. / M.S.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2006. / Modelling of the transport of fine cohesive sediments, as found in most South African reservoirs, has not been well developed. This is because the transport processes that are involved are complex and the theories not as implicit as the traditional equilibrium transport theories for coarse non-cohesive sediment. Advection and dispersion are found to be the processes that best describe the transport of fine sediments in turbulent flow conditions. A two-dimensional modelling tool, MIKE 21C, which simulates reservoir hydrodynamics and cohesive sediment transport processes with an advection-dispersion model, was evaluated in this thesis. The creation of such a numerical model involves the setting up of a suitable curvilinear grid and requires data on the bathymetry, recorded inflows as well as water levels. It also requires sediment characteristic parameters and transport parameters. These parameters have to be specified by the user based on previous studies and field measurement data. MIKE 21C was applied to laboratory flume tests and reservoir case studies in the field in order to determine the effects that these parameters have on the sediment transport in a series of sensitivity studies. Ranges were determined within which these parameter values should fall. A procedure was also developed through which reservoir sedimentation models can be calibrated.