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As many dams were built around 1950, the expected life span of these dams are about tobe reached. With this, the need for monitoring and increased understanding of the damsstructural integrity increases. In order to prevent failures, two warning signals are defined;alert and alarm. The main difference being that the first indicates an unexpected changein behavior that needs to be addressed and evaluated in the near future, while the otherrequires that immediate action must be taken to ensure the safety of the dam.This report aims to evaluate the applicability of different models for designing alert values.In order to achieve this goal, two case studies have been performed. The first being onSchlegeis, an arch dam in Austria, and the second Storfinnforsen, a concrete buttress damin Sweden. The methods used are finite element modelling as well as data-based models.Data-based models work on the presumption that the dam behaviour is governed by variationsin environmental conditions such as temperature and water level. The report hasevaluated two commonly used data-based models, hydrostatic thermal time (HTT) and hydrostaticseasonal time (HST), as well as two machine learning based models artificial neuralnetworks (ANN) and boosted regression trees (BRT).The programs used in this report are BRIGADE plus for finite element method and MATLABfor the multi-linear regression analyses HTT and HST, as well as boosted regressiontrees. The neural networks were constructed in Python using TensorFlow and Keras API.The result from the case studies is that the commonly used data-based models HST andHTT perform well enough for creating predictions and alert levels when given a sufficientamount of historical data, approximately 3-5 years. Machine learning such as artificial neuralnetworks while comparable in prediction quality does not further increase the understandingof the dam behaviour and can due to the complexity of designing an appropriate networkstructure be less suited for this type of analysis. Finite element models can also capturethe behavior of the dam rather well. It is however not as accurate as data-based modelswhen sufficient data is available. An FE-model should be used for definition of alert valueswhen insufficient data exists after the dam conditions have been significantly altered, orwhen newly constructed. The main advantage that machine learning provides is that theyperform better for non-linear behavior than multi-linear regression.

Dammar har använts till många saker genom århundrandena, bland annat energiutvinning, reglering av vattennivå och transport av timmer. När dammar inte längre är i bruk och inte är ekonomiskt gynnsamma är dammutrivning en vanlig restaureringsmetod för att återställa ekosystemen. Dammar påverkar generellt ekosystemen negativt då det blir en begränsad konnektivitet inom och mellan vattendragen och sjöarna. Fiskars migration av och spridning av fröer från växter hindras av dammarna. Genom att riva ut dammar öppnas vägar för organismer att förflytta sig. Med utrivning av dammarna sker även en vattennivåsänkning som leder till att undervattensväxter kan bli mer utsatta. Undervattensväxter (makrofyter) som lever i det grunda vattnet bidrar med skydd och habitat för både fisk och bentisk fauna, samt zooplankton. Syftet med min undersökning är att undersöka om täckningsgraden av makrofyter förändras av dammutrivning. Även koncentrationen av fosfor i vattnet samt ljustillgången (mätt som siktdjup) förväntades ha en påverkan på täckningsgraden av makrofyter i sjöarna. Resultaten visade att det inte fanns ett signifikant samband mellan täckningsgraden och dammutrivning. Ett samband mellan täckningsgrad och siktdjup kunde inte heller bevisas. Däremot fanns ett positivt samband mellan täckningsgrad och koncentration fosfor i vattnet. Den här studien visar att makrofyter inte påverkas negativt av dammutrivning vilket är positivt då makrofyter har en viktig roll i ekosystemen. / Dams have been used for many things throughout history, such as an energy source, for regulation of water levels and timber transport. When dams are no longer economically viable, dam removal is a common method of restoring the ecosystem. Dams generally effect the ecosystems negatively, as they limit the connectivity in and between rivers, streams, and lakes. For example, fish migration and the spread of seeds are typically disrupted by the dams. When dams are removed, the water levels are normally reduced, which can lead to aquatic plants becoming more vulnerable. Aquatic plants (macrophytes) that grow in shallow parts of a lake provide habitat for fish, bentic invertebrate fauna and zooplankton and they thus form an important part of the limnic ecosystems. The purpose of my study was to investigate if the coverage of macrophytes changes after dam removal in lakes. Also, the concentration of phosphorus in the water and the light availability (measured with Secchi depth) were predicted to influence the coverage of macrophytes. The results showed that there was not a significant effect of dam removal or Secchi depth on the coverage of macrophytes. The concentration of phosphors had a positive significant effect of on macrophyte coverage. My study indicates that dam removal does not affect macrophytes negatively, which may be important due to macrophytes’ important role in the ecosystem.

There are hundreds of existing dams within the State of Virginia, and even thousands more specifically within the United States. A large portion of these dams do not meet the current safety standard of passing the Probable Maximum Flood. Likewise, many of the dams have reached or surpassed the original design lives, and are in need of rehabilitation. A standard protocol will assist dam owners in completing a dam rehabilitation analysis. The protocol provides the methods to complete the hydrologic, hydraulic, and economic analysis. Additionally, alternative augmentation techniques are discussed including the integration of GIS applications and linear programming optimization techniques. The standard protocol and alternative techniques are applied to a case study. The case study includes a set of flood control dams located in the headwaters of the South River watershed in Augusta County, VA. The downstream impacts of the flood control dams on the city of Waynesboro are demonstrated through the hydrologic and hydraulic analysis. / Master of Science

Yes / The present study attempts to predict the reservoir sedimentation in 32 km region of the Tenryu River between the Hiraoka and Sakuma Dams in Japan. For numerical simulations of the reservoir sedimentation, the one-dimensional model of the Hydrologic Engineering Centre-River Analysis System (HEC-RAS) is used together with the inclusion of channel geometry, bed gradation curve, Exner-5 bed sorting mechanisms, fall velocity of the particle, and flow and sediment boundary conditions pertaining to modeling region. The modeling region of the Tenryu River is divided into 48 river stations with 47 reaches in the numerical simulations. The numerical model is calibrated using the available data for 48 years from 1957 to 2004. The formulae of sediment transport function, Manning’s roughness coefficient, computational increment and fall velocity have been identified for getting the best estimation of the Sakuma Dam reservoir sedimentation. Combination of obtained sensitive parameters and erodible limits of 2 m gave the best comparison with the measured bed profile. The computed results follow the trend of measured data with a small underestimation. Although Manning’s roughness coefficient has an effect on the sedimentation, no direct relation is found between the Manning’s roughness coefficient and reservoir sedimentation. It is found that the temperature of water has no effect on the reservoir sedimentation.

M.Sc. (Zoology) / The world’s ever increasing human population has lead to an almost unimaginable amount of waste being released in to the aquatic environment every day. Aquatic systems are faced with the greatest risk due to the fact that water is an indispensable resource required for industrial and agricultural processes. In recent years there has been a dire need for the monitoring and rehabilitation of aquatic systems. As a result many biological monitoring programmes were set into place in an attempt to manage this problem. The use of aquatic organisms as sentinels for biomonitoring studies has been wildly accepted with the majority of biomonitoring research focusing on the use of various fish and invertebrate species as aquatic sentinel organisms. However, the use of parasites as sentinel organisms is a relatively new field and as a result there has been little published work on the use of monogenean ectoparasites parasites as such sentinels. The bioaccumulation and subsequent biomagnification of metals by certain parasite species is well known, with bulk of the published work focusing on endoparasites (cestodes, acanthocephalans & nematodes), these published studies indicate that some species of endoparasites exhibit a remarkable ability to biomagnify metals in concentrations that far exceed that of their respective hosts as well as the ambient environment. Thus this project aims to assess the bioaccumulation and biomagnification of metals by the ectoparasitic diplozoon. The study site that was chosen for this project was the Vaal Dam; this site was deemed appropriate due to its near pristine condition and major economic importance. This meant that this particular site is ideal for the testing of a new biomonitoring system. All field sampling was performed around UJ Island (26°52.249’S; 20°10.249’E) from February 2011 to April 2011. A total of 29 Labeo umbratus (Smith, 1841) were collected with the aid of gill nets and three sediment samples were also taken using a grab sampler. Water quality data was obtained from the Rand Water Analytical Facility in Vereeniging as this organisation routinely monitors of the water quality parameters and the metal concentrations within the surface waters of the Vaal Dam, this information was obtained with the aid of data loggers situated in the dam...

As part of a vegetation survey program for the newly acquired farms incorporated into the Loskop Dam Nature Reserve, the vegetation of the Hondekraal Section was investigated. The study provides an ecological basis for establishing an efficient wildlife management plan for the Reserve. From a TWINSPAN classification, refined by Braun-Blanquet procedures, 12 plant communities, which can be grouped into eight major plant communities, were identified. A classification and description of the major plant communities are presented as well as a management plan. Descriptions of the plant communities include characteristic species as well as prominent and less conspicuous species of the tree, shrub, herb and grass strata. This study proves that the extended land incorporated into the Reserve contributes to the biological diversity of the Reserve. / Environmental Sciences / M. Tech. (Nature Conservation)

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: In South Africa a large number of dams owned by the Department of Water Affairs (DWA) need to be rehabilitated. This study investigated the decision process involved in the prioritisation of dams for rehabilitation. DWA developed a risk analysis methodology for defining the risks associated with dam safety, expressed as the combination of the probability and consequences of dam failure. These risks are evaluated usingmultiple acceptability criteria to assess risk to human life and the economic, social, socio-economic and environmental impacts of dam failure. In this study, the criteria used in the decision process to evaluate the acceptability of life safety risks were evaluated by comparing to international best practice methods, where the acceptability of risk to human life is commonly assessed as the expected number of fatalities against life safety criteria presented as FN-criteria on an FN-diagram. Damrehabilitation should reduce the probability of dam failure, thereby reducing the risk to society in terms of the expected lives lost. However, the rehabilitation works come at a cost and the level of these investments are usually large. In addition, the rehabilitation of South African government owned dams are financed by society and these financial resources are limited. Thus investments into dam rehabilitation works should be worthwhile for society. Society’s Willingness to Pay (SWTP) for safety was applied to South African dam safety to determine the acceptable level of expenditure into life safety that is required by society. Investments into improved safety levels are not always dictated by society, but could also be driven by the decision maker or owner requiring an economically optimal solution for the rehabilitation. Economic optimisation accounts for considerations additional to life safety, including economic motivations, damage costs of dam failure as well as compensation costs for lives lost. Often economic optimisation would govern the decision problem. Also, the DWA current evaluation does not take the cost of rehabilitation into account in any way. Thus, FN-criteria that primarily evaluates life safety, but also incorporates a measure of economic efficiency, were suggested in this study. / AFRIKAANSE OPSOMMING: In Suid-Afrika moet ’n groot aantal dammewat deur dieDepartement vanWaterwese (DWA) besit word gerehabiliteer word. Hierdie studie het die besluitnemingsproses ondersoekwat toegepasword om damme te prioritiseer vir rehabilitasiewerke. DWA het ’n bestaande metodologie wat gebaseer is op risiko-analise. Die risikos wat verband hou met damveiligheid word deur die metode bepaal en word uitgedruk as die kombinasie van waarskynlikheid en die beraamde gevolge van damfaling. Hierdie risikosword geëvalueer teenoor verskeie kriteriawat die aanvaarbaarheid van risikos teenoor menselewens en die ekonomiese, sosiale, sosio-ekonomiese en omgewingsimpakte van damfalings assesseer. In hierdie studie word die kriteria wat gebruik word in die besluitnemingsproses om die aanvaarbaarheid van risikos teenoor menselewens te bepaal geëvalueer deur die kriteria te vergelyk met metodes wat internasionaal as beste praktyk beskou word. Internasionaal word die aanvaarbaarheid van risikos teenoor menselewens oor die algemeen as die verwagte aantal sterftes teenoor lewensveiligheidskriteria FN-kriteria op ’n FN-diagram geassesseer. Dam rehabilitasiewerke behoort die waarskynlikheid van damfaling te verminder, sodoende verminder die risiko teenoor die samelewing in terme van verwagte sterftes. Die rehabilitasiewerke vereis finansiële beleggings, en hierdie beleggings is gewoonlik groot. Verder word die rehabilitasie van Suid-Afrikaanse damme wat deur DWA besit word deur samelewing gefinansier en hierdie finasiële hulpbronne is beperk. Dus moet hierdie beleggings die moeite werd wees vir die samelewing. Die samelewing se bereidwilligheidomte betaal ("SWTP") vir veiligheid word toegepas in Suid- Afrikaanse damveiligheidomdie aanvaarbare vlak van beleggings vir ’n verbeterde veiligheid teenoor menselewens wat deur die samelewing vereis word te bepaal. Beleggings in verbeterde damveiligheidsvlakke word egter nie altyd bepaal deur die samelewing nie,maar kan ook gedryf word deur die besluitnemer of eienaar wat ’n ekonomies optimale oplossing vir die rehabilitatiesewerke vereis. Ekonomiese optimering neem oorwegings addisioneel tot lewensveiligheid in ag, insluitend ekonomiese motiverings, skade kostes as die dam faal, sowel as vergoedingskostes vir die verwagte sterftes. Ekonomiese optimering beheer dikwels die besluitnemingsprobleem. Verder neem die huidige DWA besluitnemingssproses in geen manier die kostes van rehabilitasie in ag nie. Dus word FN-kriteria wat hoofsaaklik veiligheid teenoor menselewens evalueer,maar wat ook ’n mate van ekonomiese doeltreffendheid insluit, voorgestel in hierdie studie.