Sharp crested rectangular weirs used for discharge measurement purposes in open channel hydraulics are investigated experimentally. A series of experiments were conducted by measuring discharge and head over the weir for different weir heights for full width weir. It is seen that after a certain weir height, head and discharge relation does not change. Hence a constant weir height is determined. For that height / discharge and head over the weir are measured for variable weir width, starting from the full width weir to slit weir. Description of the discharge coefficient valid for the full range of weir widths and an empirical expression involving dimensionless flow variables is aimed. Experimental data obtained for this purpose and the results of the regression analysis performed are represented.

Abstract Fishways are hydraulic structures designed to dissipate the energy of flowing water in order to decrease water velocities and increase water depths. The history of fishways is long, the first written remarks date back to the 17th century. Fishway hydraulics, however, have been intensively studied only starting since the 1980's. Fishways have been classified into three main categories according to their hydraulic characteristics: pool-and-weir, vertical slot, and Denil fishways. Fishways are hydraulically complex structures, and thus designing tools for different fishway types have been developed. In this report, a new designing procedure has been established, and equations for each main fishway type have been suggested. In addition, flow conditions below different fishway types have been examined, and velocity distributions at weirs with V-shaped crests in both pool-and-weir fishways and at a single weir have been compared in different discharges and drops. Fishway flows have been compared with flows over single weirs.

Dams and weirs are widely implicated in large-scale declines in both the range and abundance of aquatic fauna. Although many factors are involved, such declines are commonly attributed to the prevention or reduction of migration, reductions in available habitat, alteration of natural flow regimes and changes to physicochemical characteristics. In Australia, studies into the ecological effects of these impacts are limited, and have concentrated mainly on species of recreational and commercial importance. Subsequently, the adverse effects of dams and weirs, and suitable methods of mitigation, remain largely unknown for many other taxa. Therefore, the major aim of this thesis is to investigate the ecological effects of dam and weir construction on previously unstudied migratory assemblages of fish and macroinvertebrates in the Murray-Darling Basin. It is anticipated that the results of these studies will feed back into improved management strategies that help arrest the previously observed declines of aquatic fauna. Initially, fish communities were sampled, by boat electrofishing, from both reference sites and downstream of Balranald and Redbank weirs on the lower reaches of the Murrumbidgee River, Australia. Sampling was stratified over large spatial and temporal scales to gain a comprehensive understanding of species most affected by the presence of these two barriers. In general, the weirs obstructed fish migrations during summer and autumn and many species of small-bodied fish such as Australian smelt, western carp gudgeon, fly-specked hardyhead and crimson-spotted rainbowfish accumulated downstream of Balranald Weir. In addition, downstream accumulations of juveniles of larger-bodied species such as bony herring, common carp and goldfish were also detected. Although many previous studies had either documented or hypothesised that upstream migrating fish accumulate downstream of migration barriers, none attempted to quantify the size of such populations. Therefore, a simple but efficient method to estimate the size of migratory populations was assessed at the Balranald Weir site. The application of two commonly used estimation techniques yielded relatively reliable results for seven species that accumulated downstream of the weir. Population size estimates were greatest for most species during summer and autumn, where accumulations as high as 800 fish per day were detected. The largest calculated population size estimates, in addition to the greatest temporal variation, of any individual species was observed in bony herring. Given the simplicity of the technique and the relative accuracy of population estimates, it was concluded that these methods could easily be applied to other weirs where the size of migratory populations is of particular interest. A study investigating the effects of Yanco Weir on the diets of three migratory percichthyid species, Murray cod, trout cod and golden perch was also conducted. Observed spatial variation in a number of trophic processes strongly implicated Yanco Weir as a major contributor to increased competition among percichthyid species on the Murrumbidgee River. The greater relative abundance of percichthyids from downstream samples, combined with increases in dietary overlap and a greater percentage of empty stomachs, also suggested percichthyids may be significantly affecting the relative abundance of potential prey items such as freshwater prawns and Australian smelt. These significant changes in dietary composition were likely related to migratory behaviour, as these species accumulated downstream of the weir, and could be readily expected at other sites where passage is obstructed. It was suggested that the construction of suitable fish passage facilities would effectively reduce the probability of migratory fish accumulating and, subsequently, potential effects of dams and weirs on trophic processes. Since it was established that dams and weirs of the Murrumbidgee River were significantly affecting migratory fish communities, an innovative but relatively inexpensive fishway design, the Deelder fish lock (after Deelder, 1958), was constructed and assessed for wider application throughout the Murray-Darling Basin. The Deelder lock was effective at mitigating the effects of Balranald Weir by providing passage for a wide range of size classes and species of fish; but importantly, the structure enabled the passage of most species previously observed to accumulate downstream of the structure. Most significant was the ability of the fish lock to pass substantial numbers of small-bodied fish, which were previously not considered migratory, suggesting that these species should be considered when developing options to mitigate the effects of other dams and weirs throughout the Murray-Darling Basin. A significant finding of this study was the realisation that substantially more species and size classes of Australian native fish are migratory than previously thought. Subsequently, it is recommended that, when designing facilities to mitigate the effects of a dam or weir, the structure of the entire migratory community is considered when developing operating parameters. Various options for mitigating the effects of dams and weirs are discussed, but it was concluded that the construction of effective fishways would be the most appropriate means of restoring migration pathways to Australian native fish. A strategic approach for assessing and adaptively mitigating the effects of dams and weirs is presented and discussed.

Os vertedores são estruturas hidráulicas de suma importância no controle de escoamento e também para medição de vazões. Estas estruturas são amplamente utilizadas em aproveitamento múltiplos principalmente como controle de vazão. Neste trabalho é apresentado um histórico dos estudos elaborados para vertedores, demonstrando as principais características entre cada estudo.Também são apresentados os resultados obtidos através dos cálculos de linha d\'água é pressão utilizando as equações para superfícies de fundo curvo para um perfil segundo o equacionamento de Creager e o perfil Cossenoidal proposto por este trabalho. O escoamento realizado em um perfil Cossenoidal apresenta um comportamento muito semelhante ao escoamento realizado em um perfil do tipo Creager. Com a utilização do perfil Cossenoidal foi possível realizar a coincidência de raio de curvatura no trecho da crista onde o raio de curvatura do perfil Cossenoidal ajustado a um perfil do tipo Creager, apresentou o mesmo valor para o raio de curvatura para uma elipse proposta por Maynord modificado por este trabalho. Os resultados de linha d\'água e pressão foram bons e satisfatórios muito semelhantes aos valores já apresentados pelas soleiras convencionais (Creager e Maynord). / The spillways are hydraulic structures very important in the control flow and for measuring flow rates. These structures are widely used mainly for multiple use flow control. This work presents a history of the studies prepared for spillways, showing the main features of each study. It is intended to study a cosinusoidal profile through a mathematical model seeking to obtain satisfactory answers to the water lines and pressure for the studied profile. Showing the results obtained through the water level and pressure calculations, using the equations for curve surface for a Creager\'s profile and Cossenoidal\'s profile suggest in this work. The flow realized in a Cossenoidal\'s profile show a behavior similar at the flow realized in a Creager\'s profile. The utilization of the Cossenoidal\'s profile was possible to realize the coincidence of the curvature radius in the crest between Cossenoidal\'s profile and Maynord Modified ellipse, and this profile was adjusted with a Creager\'s profile and Maynord\'s ellipse. The results of water level and pressure showed goods and satisfactory, very similar with the values showed in other studies for a conventional weirs (Creager and Maynord).

Os vertedores são estruturas hidráulicas de suma importância no controle de escoamento e também para medição de vazões. Estas estruturas são amplamente utilizadas em aproveitamento múltiplos principalmente como controle de vazão. Neste trabalho é apresentado um histórico dos estudos elaborados para vertedores, demonstrando as principais características entre cada estudo.Também são apresentados os resultados obtidos através dos cálculos de linha d\'água é pressão utilizando as equações para superfícies de fundo curvo para um perfil segundo o equacionamento de Creager e o perfil Cossenoidal proposto por este trabalho. O escoamento realizado em um perfil Cossenoidal apresenta um comportamento muito semelhante ao escoamento realizado em um perfil do tipo Creager. Com a utilização do perfil Cossenoidal foi possível realizar a coincidência de raio de curvatura no trecho da crista onde o raio de curvatura do perfil Cossenoidal ajustado a um perfil do tipo Creager, apresentou o mesmo valor para o raio de curvatura para uma elipse proposta por Maynord modificado por este trabalho. Os resultados de linha d\'água e pressão foram bons e satisfatórios muito semelhantes aos valores já apresentados pelas soleiras convencionais (Creager e Maynord). / The spillways are hydraulic structures very important in the control flow and for measuring flow rates. These structures are widely used mainly for multiple use flow control. This work presents a history of the studies prepared for spillways, showing the main features of each study. It is intended to study a cosinusoidal profile through a mathematical model seeking to obtain satisfactory answers to the water lines and pressure for the studied profile. Showing the results obtained through the water level and pressure calculations, using the equations for curve surface for a Creager\'s profile and Cossenoidal\'s profile suggest in this work. The flow realized in a Cossenoidal\'s profile show a behavior similar at the flow realized in a Creager\'s profile. The utilization of the Cossenoidal\'s profile was possible to realize the coincidence of the curvature radius in the crest between Cossenoidal\'s profile and Maynord Modified ellipse, and this profile was adjusted with a Creager\'s profile and Maynord\'s ellipse. The results of water level and pressure showed goods and satisfactory, very similar with the values showed in other studies for a conventional weirs (Creager and Maynord).

This thesis describes a short study to examine the behaviour of submerged flow over a thin plate weir with differing upstream and downstream bed levels i.e. an unequal bed weir as opposed to an equal bed weir where the upstream and downstream beds are at the same level. As submerged weir flow is a function of downstream conditions, it was thought that a lower downstream bed would make submerged flow over the weir easier, This is turn suggested that; The shape of the upstream head (Hu) vs downstream head (Hd) graph would change, being initially more steep in the unequal bed case. The Froude Number of the approaching flow would be lower for the unequal bed weir than for an equal bed weir at the same submergence. Using one of the existing submerged flow formula would lead to an erroneous calculated value. A series of measurements was done on two model weirs of different sizes subject to successive levels of submergence. Analysis of the readings of upstream and downstream heads indicated that the difference in bed levels was significant and the three effects above were noted. The work also suggested a new form of equation to calculate flow over a submerged weir. This was looked at briefly.

In 2001 the World Commission of Dams concluded that the economic, social and environmental cost of dams has been unacceptably high. As a result, dam removal is emerging as a promising option in addressing these concerns. However, dam removal is a contentious issue sharply divided between biophysical and socioeconomic interests. The purpose of this thesis is to conduct an explanatory case study of Eden Mills, Ontario to investigate the process of dam removal consideration. It was determined that i) safety ii) economics iii) social value and iv) environmental impact were critical variables influencing the decision-making process. Following site analysis, key-informant interviews and a design vignette survey it was determined that Eden Mills pursue dam removal as the social value of the millpond no longer justified the sustained economic and biophysical costs associated with the dam. This process theory can be applied to other dam removal scenarios to facilitate the decision making process.

Changes in the bed of Geum River (L=130 km from Daechung regulation dam to Geum River estuarial bank) in South Korea were predicted using the 1-D HEC-RAS model and the 2-D CCHE2D model. Three movable weirs have been installed and dredging has been carried out in Geum River under the Four Major Rivers Restoration Project (2009-2012). Inflow data of sub basins were calibrated with daily runoff data generated by PRMS based on a hydrologic unit map. To determine the gate opening height for maintaining the management water level, unsteady analysis was performed using HEC-RAS. Thereafter, long-term riverbed changes through quasi-unsteady analysis were simulated for 20 years. In order to investigate the effect of movable weirs, sediment analysis was done for three cases of gate opening: case 1 is fully close, case 2 is fully open, and case 3 is regulating gates by the operating rule. Also, short-term riverbed changes were predicted with CCHE2D for 11 days in the problem area, depending on the results of 1-D model, and the effect of dikes was examined. In future, gate operation and structural methods such as dikes must be in step with each other in order to manage sediment and rivers in an ecofriendly manner.

Judith Weir (b. 1954) composed King Harald’s Saga: Grand Opera in Three Acts for Unaccompanied Solo Soprano Singing Eight Rôles (1979) for radio broadcast. She wrote the libretto for the opera based on Snorri Sturluson’s book, King Harald’s Saga. This opera illustrates Weir’s remarkable compositional style, including her treatment of the libretto in narrative style and her representation of multiple characters by one singer. Despite Weir’s fame as an opera composer, King Harald’s Saga is rarely performed owing to three major musical and performing challenges. These challenges are performer’s ability to delineate eight separate characters (dramatic challenges), to sing wide leaps and long melismas (vocal challenges), and to perform a cappella with wide leaps and complex rhythms (musical challenges). This dissertation presents a performance guide for the soprano addressing these three challenges and suggesting possible solutions. Such a guide will assist the soprano in preparing and performing this grand opera, which thus far has not received the due attention and appreciation of either performers or audiences.

Please read the abstract in the dissertation. / Dissertation (MEng)--University of Pretoria, 2013. / gm2014 / Civil Engineering / Unrestricted