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Thesis (MEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: A dam can have a significant impact on the downstream river morphology by altering both the flow regime and the sediment load. The effect of a dam is dependent on factors such as the storage capacity relative to the mean annual runoff (MAR), the operation of the reservoir and the sediment yield of the catchment. Changes in the river morphology include the degradation and coarsening of the riverbed, generally closer to the dam, and aggradation further downstream where the sediment delivered by tributaries cannot be carried through because of the reduced sediment transport capacity of the river. The impact of a dam can stretch over several hundreds of kilometres. The main objective of this thesis was to gain a better understanding of the impacts that dams can have on the downstream river morphology. This was done by developing equations that can describe the channel geometry, investigating the effect of the presence of clay and silt on the sediment transport behaviour of sediments, as well as detailed evaluation of simulations carried out with a one-dimensional mathematical river model (MIKE 11). The calibrated regime equations were found to be comparable to other internationally developed regime equations and to be suitable for natural rivers. It was found, however, that these regime equations are not applicable to rivers downstream of dams that have highly unnatural release patterns. Further research is needed in this regard. By investigating the effect of cohesive sediments on the sediment transport behaviour of mixed sediments it was found that as little as 7% clay and silt in the bed could affect their sediment transport characteristics. A methodology was also developed by which the critical conditions for mass erosion of cohesive sediments can be described in terms of the applied stream power. Sediment transport equations were calibrated and verified in terms of the unit input stream power for fine and non-cohesivesediments. The sediment transport equation for fine sediments was implemented in MIKE 11. The simulations over a 40 km reach of the Pongola River downstream of Pongolapoort Dam, have shown that even when a large demand is placed on the stored water, and most of the smaller floods are therefore absorbed by the dam, the downstream impact can still be considerable, with as much as 5 m deep erosion in places. The sediment loads are generally reduced (by as much as 35%), but the effective catchment area downstream of the dam has been reduced by as much as 90%, indicating that substantial erosion had to have taken place in the river. Coarsening of the riverbed was also observed during the simulations. / AFRIKAANSE OPSOMMING: 'n Dam kan 'n aansienlike impak he op die riviermorfologie stroomaf daarvan, deurdat dit beide die vloei en sedimentlading drasties kan verander. Die effek van 'n dam hang van verskeie faktore af, soos die opgaarkapasiteit in vergelyking met die gemiddelde jaarlikse afloop (GJA), die bestuur van die dam en die sedimentlewering van die opvanggebied. Veranderings in die riviermorfologie behels die degradering van die rivierbed, sowel as die uitspoel van fyn materiaal uit die rivierbed, veral nader aan die dam. Deponering vind verder stroomaf van die dam plaas, waar die sediment wat deur die sytakke ingevoer word nie deurgevoer kan word nie, weens die verlaagde sedimentdravermoe van die rivier. Sodoende kan rivierlope oor honderde kilometers deur 'n dam bemvloed word. Die hoofdoel van die tesis was om meer insig te verkry oor die impak wat damme op die stroomaf riviermorfologie kan he. Derhalwe is vergelykings ontwikkel wat die riviermorfologie kan beskryf. Die effek van die teenwoordigheid van klei en slik op die sedimentvervoer-eienskappe is ondersoek, en gedetaileerde ontledings is met 'n een-dimensionele wiskundige riviermodel (MIKE 11) is gedoen. Daar is bevind dat die regime-formules goed vergelyk met ander intemasionaalontwikkelde formules en dat hulle geskik is vir toepassing op natuurlike riviere. Daar is egter gevind dat die formules nie geskik is vir riviere wat stroomaf Ie van damme wat hoogs onnatuurlike loslatings het nie. Verdere navorsing is op hierdie gebied nodig. Ondersoek na die effek wat klei en slik op die sedimentdravermoe het, het getoon dat slegs 7% klei en slik in die rivierbed die sedimentvervoer-eienskappe van mengsels van fyn en growwe materiaal kan bemvloed. 'n Metode is ontwikkel waarmee die kritiese toestande vir massa-erosie van kohesiewe sediment beskryfkan word in terme van die aangewende stroomdrywing teen die bed. 'n Sedimentvervoer-vergelyking in terme van die eenheids-insetstroomdrywing vir fyn en nie-kohesiewe sedimente is gekalibreer en geverifieer. Die nuwe sedimentvervoer-vergelyking vir fyn sedimente is gebruik in die MIKE 11 simulasies. Hierdie simulasies oor 'n 40 km loop van die Pongolarivier stroomaf van Pongolapoort Dam, het getoon dat selfs as daar 'n groot aanvraag op 'n dam se water geplaas word, en gevolglik meeste van die kleiner vloede deur die dam geabsorbeer word, die impak van die dam nogs steeds aansienlik kan wees, met soveel as 5 m diep uitskuring in plekke. Die sedimentladings het gewoonlik verminder (met soveel as 35%), maar die die effektiewe opvanggebiedarea stroomafvan die dam het met meer as 90% verminder, wat daarop dui dat daar aansienlike erodering in die rivier plaasgevind het. Die simulasies het ook getoon dat die hoeveelheid fyn materiaal in die rivierbed verminder het.

<p>A lot of mine waste rock and tailings arise from all mining processes and have to be stored in an appropriate way. Tailings are deposited in impoundments retained by tailings dams. The objective of tailings dams is to retain the slurry from the mining process and in that way prevent spill into the surroundings that might be harmful for the environment. Tailings dams are often constructed as staged embankments so that construction costs and demand of materials are spread more evenly over the period of deposition.</p><p>The objective of this thesis has been to compile information about and evaluate events at Swedish tailings dams and also to develop a collective database for all Swedish mining companies for all tailings dams and all events that occur at tailings dams.</p><p>Information about 60 events at Swedish tailings dams has been gathered and evaluated. The evaluation has been performed by comparison between and analysis of individual parameters and also by use of a multivariate statistical method called PLS. The statistical analysis shows a decrease in the numbers of events during the last five years, which indicates improved dam safety within the mining industry. The analysis also shows that severe events and the human factor might be related when it comes to the initiating cause of the event. Further relations between the parameters and the severity of the events can be seen from the PLS-analysis, for example that low and short tailings dams to a greater extent are subjected to severe events. To be able to draw more reliable conclusions further studies with a more complete basic data are needed.</p><p>This work has shown a need of a collective database within the Swedish mining industry for tailings dams and occurring events at tailings dams so that more complete basic data could be obtained for future studies. A structure for such a database has been developed in Microsoft Access 2000. The aim of the database is to facilitate feedback within the mining industry and to gather comprehensive data for future statistical evaluations.</p> / <p>Vid alla gruvprocesser skapas stora mängder restprodukter i form av gråberg och anrikningssand som måste tas om hand på lämpligt sätt. Anrikningssanden deponeras tillsammans med vatten från gruvprocessen i magasin omgärdade av dammvallar, s.k. gruvdammar. Gruvdammar har som syfte att hålla kvar anrikningssand och vatten och måste vara stabila så att de skyddar omgivningen från utsläpp av anrikningssand som skulle kunna vara skadligt för miljön. En gruvdamm byggs ofta upp i etapper eftersom byggkostnaderna och behovet av dammfyllnadsmaterial då sprids över tiden.</p><p>Syftet med arbetet har varit att sammanställa och utvärdera händelser vid svenska gruvdammar samt att utforma ett för gruvindustrin gemensamt dammregister och felrapporteringssystem.</p><p>60 händelser vid svenska gruvdammar har sammanställts och utvärderats. Utvärderingen har genomförts dels genom att enskilda parametrar jämförts och analyserats och dels med hjälp av den multivariata analysmetoden PLS. Den statistiska analysen visar på en minskning i antal händelser under de senaste fem åren, vilket tyder på ett förbättrat dammsäkerhetsarbete inom gruvindustrin. Analysen har kunnat uppvisa ett samband mellan allvarliga händelser och den mänskliga faktorn när det gäller vad det är som initierat händelserna. Genom PLS-analysen har ytterligare samband mellan de undersökta parametrarna och allvarlighetsgraden av händelserna kunnat utläsas, bl.a. visar analysen att låga och korta dammar i större utsträckning drabbas av allvarliga händelser jämfört med höga och långa dammar. För att säkra slutsatser ska kunna dras krävs dock vidare studier med ett mer komplett statistiskt underlag.</p><p>Examensarbetet har påvisat ett behov av ett branchgemensamt damm- och felrapporteringsregister för att ett mer komplett underlag ska kunna erhållas i framtiden. En färdig databasstruktur för ett sådant dammregister och felrapporteringsregister för svenska gruvdammar har utformats. Databasen är uppbyggd i Microsoft Access 2000 och är tänkt att underlätta erfarenhetsåterföring inom branschen samt att ge ett underlag för framtida statistiska undersökningar.</p>

This study proposes the use of a pipe line system to transport the inflow sediment to a reservoir through the dam, and discharge it downstream. The system is powered by the available head at the dam. It aims at restoring the original sediment transport regime of the river (i.e. before the dam was built). The idea is fundamentally sound because of the much more efficient sediment transport characteristics of pipes compared to that of open channels. The necessary theory for the hydraulic design of such a system was simply not available and is developed in this study. The work of numerous previous investigators is summarized in the final results and in the developed equation which allows for the calculation of the capacity transport concentration of sediments in pipes. This equation, coupled with the most accepted head loss equation, and the continuity principle, allows for the hydraulic design of systems transporting grannular material. The calculation procedures were fitted into computer programs. In addition to computer programs, design charts where developed which allow for quick application as well as visualization of the developed concepts. It was concluded that the proposed system is fundamentally feasible. Although no economic analysis was conducted, indicators show that it is also economically favorable.

Mining activity is suspected of contributing sulfate and total dissolved solids (TDS) to ground water downgradient of the Pima mining district. High ionic concentrations in tailing impoundments suggest that tailings-pond recharge may be a source of the contamination. Experiments indicated that sulfate is not significantly produced by inorganic sulfide oxidation in the tailings ponds. Tailings pond water chemistries were compared with historical water quality analyses in the Pima district. The U.S.G.S. computer program PHREEQE modeled saturation indices for anhydrite, calcite, fluorite, and gypsum in water chemistries throughout the study area. Well water downgradient of the mines had lower saturation indices than tailings pond water which discredits the claim that tailings-pond recharge is acquiring salts as it percolates to the aquifer. Evidence supports the opinion that tailings pond seepage is contributing to the sulfate and TDS content in ground water downgradient of the ponds.

Background: Tailings dam workers are exposed to tailings dust that has a potential health risk due to the element contents in the dust. The extent of exposure of tailings dam workers is unknown. Consequently, the elements, level of exposure, the potential adverse effects to health, compliance to legislative requirements and the efficiency of the current control measures were investigated. Design and Method: During the trials, 69 personal dust samples were collected during three full production shifts from tailings dam workers in three different tailings dam environments. The field filters were weighed to calculate the total dust concentrations. Bulk samples and field filters were analysed using the 32-element and particle size distribution scans. The between-dam, between-days and between-group variances were determined to assess the changes in exposure levels. Results: The tailings dam workers were not overexposed to tailings dust. Mean exposures were below the OEL for PNOC, measuring 0,124 mg/m3 (TD 1) 0,366 mg/m3 (TD 2) and 2,956 mg/m3 (TD 3). Three outliers in the data were present in TD 3 and exceeded the action level for PNOC. A major part of the particle size distribution consisted of inhalable sizes (>I0 μm). Cyclone tailings dams have smaller particle sizes than spigot tailings dams, though 85% of the particles in all tailings dams were larger than 10 μm. Some elements identified in the dust have potential respiratory health effects. No significant differences existed between the three tailings dams regarding tailings dust concentrations (p=0,527 on 5% significant level and p=0,292 on 10% significant level). There was, however, a significant difference on a 5% significant level between the days (p=0,003 and p=0,006). The workers on the cyclone tailings dams had smaller exposures than workers on the spigot tailings dams, and the pipeline labourers were more exposed than the mudguards. The tailings dams did comply with legislative control measures. However, washing facilities for the cleaning of overalls due to elements in the dust, such as nickel, chromium and manganese need to be considered. Workers need to be educated in work practices and procedures, personal hygiene and symptoms that can be experienced after exposure. Engineering control measures such as water sprayers covering the entire tailings dam, the use of fixed or temporary windscreens in the area where work is done and covering of the roads on the tailings dam with gravel or water spray can be considered as dust suppressant controls. Conclusion: The study met the issues set out in chapter 1, hypotheses were rejected and accepted and future studies were suggested. / Thesis (M.Sc. (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2007.

Tailings is leftover material from mining industry and is produced in huge quantities approximately 70-99% of the ore production.  Tailings material is stored as impoundments by constructing tailings dams which are often constructed with tailings material itself. Tailings are artificial material and the mechanical behavior of tailings material upon loading is different as compared to natural soil materials. There are number of dam failures reported every year which has severe impact on inhabitants and environment nearby. Considering the failures of tailings dams and consequences there is a need to understand the tailings material in depth for safe existence of these dams. The confident dam design can assure the safe existence of tailings dams for long term as these dams are presumed to function for generations to come. The material properties in tailings dams can change during operation due to raising of new layer. Raised new layer can change stress level, which in turn may change the material properties in terms of strength, pore pressures, grain sizes etc. Today mostly tailings dam are designed by performing analysis for safety for existing and future rasings as well. These analyses are based upon a for certain factor of safety. Not very much can be done with design and analysis for tailings material if the material is not described very well. Understanding of tailings material in depth can provide help for detailed material parameters which later can be used in safety assessment for future raising and changed conditions in dam. This study presents the work carried out on tailings material from a Swedish tailings dam. The study is conducted on undisturbed and disturbed tailings material. The undisturbed tests are carried out to understand material properties as per in-situ conditions. Whereas disturbed materials are used to created different materials with different particles sizes. Initially in this study the basic properties of tailings materials are studied e.g. specific gravity, phase relationships, particle sizes, particle shapes and shear behavior on collected samples at various depths. During direct shear tests, the unexpected vertical height reductions were observed, these results are presented in this study. The comparison of strength parameters by direct shear and triaxial tests on material from various depths is also done and presented. Based on results from direct shear, triaxial and oedometer tests on uniform sized tailings material; the evaluation of primary and secondary deformations and particle breakage and effect of vertical loads is also carried out and presented. The study also includes the comparison of strength parameters for each particles size. The breakage of particles is analyzed by sieving the material after direct shear tests followed by a particle shape study. The effect of deposition on shear strength parameters is also studied by construction of samples with different angle of deposition of material. The strength parameters of uniform sized particles in triaxial tests are also evaluated and discussed.

Theories of transboundary water politics have failed to explain the status quo in many river basins: fragile political relations between riparian states and nationalist domestic politics, as well as weak regional institutions and huge economic inefficiencies – but also an absence of wars over water. This is due to an uncritical approach to scale, power, and geopolitics. It is the purpose of this thesis to address these conceptual gaps by critically evaluating the multiple relationships between the logic of large dams and the politics of international rivers. The meaning of dams, the politics of their operation and construction, and their impact on international relations are much more ambiguous, opaque and complex than existing explanations have suggested so far. In turn, their logic influences, competes with, and contradicts the logic of river basin governance. Dams produce alternative spaces of development, energy, and state power that complement or are superimposed on existing spaces of riparian cooperation. This thesis argues that the contradictions between these spaces explains the geopolitical limbo of many international rivers in the developing world. Drawing from Foucault’s governmentality theory, the literature of critical geopolitics, and post-structural approaches to spatial scale the case-oriented research design of this thesis evaluates two geopolitical processes in contentious transboundary river basins: the construction of the Grand Ethiopian Renaissance Dam on the Nile and the operation of the Toktogul Dam in the Kyrgyz stretch of the Syr Darya River. By unpacking these processes, this thesis makes three substantial contributions to existing scholarship. Firstly, it is argued that regional river basin management is essentially a geopolitical project that contradicts the geo-economic imperatives of the dam. Secondly, power and agency in water politics is diffused far beyond the nation-state and can be understood in terms of “network effects”. Thirdly, to marry the concerns of the geopolitical and the geo-economic, I propose that the contrasting logics give rise to “geopolitical entrepreneurs” – actors who use geopolitics for wealth accumulation, legitimacy, nation-building, and other ends. While dams may provide power, wealth, and authority an allegorical Sword of Damocles is let down on the riparians.

Genetic variation and thermal tolerance were surveyed for variation attributed to nonuniform selection pressures for five populations of the red shiner, Notropis lutrensis, collected from regulated and unregulated portions of a Texas river. Populations within 30 km of a hypolimnion-release dam that experience large thermal perturbations were found to have higher levels of heterozygosity, higher levels of polymorphism, significantly depressed levels of upper thermal tolerance endpoints, and greater variances in tolerance endpoints. These populations have evolved enzyme systems differing from the unregulated populations in response to a variable and depressed thermal regime.

Water resources are frequently under inspection as pollution increases. Therefore an urgent need has arisen for sensitive bio-monitoring tools in toxicant impact assessment to indicate the effect of pollution on fish health in polluted aquatic ecosystems. Histopathological assessment of fish tissue allows for early warning signs of disease and detection of long term injury in cells, tissues or organs. Various biochemical and biological studies of fish have been used to assess the consequences of environmental toxicants on fish, but histology is able to enhance and add quality to the research carried out by identifying cellular alterations and quantifying the results. The aim of this study was to assess the degree of pollution in the Marais Dam (MD) and Rietvlei Dam (RVD) in the Rietvlei Nature Reserve (RNR) by determining the health status of the sharptooth catfish, Clarias gariepinus, using fish histology as a bio-monitoring tool.The MD and RVD situated within the Sesmyl Spruit serve to provide the area with water and are separated by a natural wetland. The dams were chosen for their elevated levels of toxicants. Four sampling surveys, two low flow and two high flow, were carried out over a period of two years. During each survey twenty fish were sampled per dam. Water and sediment were sampled for metal and endocrine disrupting chemical analysis. A standardized health assessment protocol employed to determine the effects of the toxicants included analysis of blood constituents, fish necropsy, calculation of condition factor and organosomatic indices, and a qualitative and quantitative histological assessment of three target organs: the gills, liver and gonads. These organs were removed and processed according to standard techniques for histological assessment. Histopathological alterations of each organ were identified (qualitative assessment) and subsequently quantified by means of a standard methodology of criteria to assess and compare fish health (quantitative assessment). The total index (Tot-I) values from the quantitative histological assessment were statistically analyzed using the ANOVA method. Potential endocrine disrupting chemicals and metals in the water of both dams were present at levels that could be toxic. The degree of pollution was more severe in MD than RVD. Examination of tissue from the gills, liver and gonads revealed marked histopathological alterations. The quantitative histological assessment indicated that fish collected from MD were in a significantly more severe histopathological condition than those of RVD. These results indicate that the wetland may still function as a natural filter. The qualitative and quantitative histological assessment objectively compared C. gariepinus specimens from MD and RVD and the effects of the toxicants on the health of the fish. / Dr. G.M. Pieterse