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.

1. Realigning rivers is becoming common as a solution to conflicting needs of land development and ecosystem preservation. Although an increasing number of projects are monitored, exactly how these channels develop as functional stream ecosystems is still poorly understood. Mining in the upper catchment of the River Nith (Scotland) required the realignment of 3km (approx.) of river. The engineered channel was designed around sound geomorphological principles of sediment transport and supply with a sinuous planform and pool-riffle sequences along the installed gravel-bed. 2. A comprehensive survey covering biotic and abiotic development was devised and implemented to test models and hypotheses relating to the development riverine habitats over the first three years. 2. Physical habitat development at the reach scale was investigated using fixed-point photography and differential GPS surveys of the thalweg and of cross-sectional form every 100m. This revealed the development of a relatively diverse streambed habitat in response to both the channel slope and planform. However, other than at meander bends where asymmetry developed over several years, little change was observed to the form of the engineered riverbanks. 3. Kick-net surveys of benthic invertebrate communities at 10 sites showed a negative relationship between specific measures of diversity and downstream distance during the early stages of development. (e.g. Richness with chainage at the 6 month stage) but the relationship degrades rapidly and is likely in part to appear as a result of low population densities. 4. Survey of transects through the riparian zone perpendicular to the river indicated that colonisation by vegetation is also related to distance along the realignment but physical habitat and geographical factors play a more dominant role over development (Canonical correspondence analysis of vegetation data in 2007) 5. Many of the indices of diversity for both biotic and abiotic elements of the ecosystem proved ineffective at detecting development at the reach scale. This may be because significant changes occur at a smaller scale than was detected by the surveys. It is likely that greater resolution is required to detect more ecologically meaningful relationships and patterns. 6. Overall study shows constructed realignments can rapidly develop a diverse streambed community within 24 months. Riparian communities are slower to develop because of the slow development of riverbank habitat diversity. Other ecosystem properties such as resilience and connectivity may take much longer.

Thesis (M.L.A.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 54-57).

The demand of electric power has rapidly increased in China along with the financial development. High pollution rates have pushed the development towards more renewable energy generating alternatives. In recent years larger investments of hydropower- generated electricity have been to satisfy the increased demand. Hydropower can cause non-energy related problems when implemented in a large scale. In this project the Nanjing Reach of Yangtze River was investigated through a hydrodynamic and sediment transport perspective. Nanjing Reach consists of two river branches and the upstream construction of the Three Gorges Dam has caused an imbalance of sediment composition that leads to an increasing difference of the diversion ratio between the branches. This is causing a problematic navigational situation for larger vessels along the north branch. In this project non-submerged water diverting dykes were modelled using two-dimensional depth averaged finite element method to estimate the impact on the hydrodynamic and sediment transport conditions. The examination showed that engineering measures at the downstream part of the reach were more effective than structures at the front, when taking both hydrodynamic and the more long-term impacts from sediment transport into account. Although the results of the sediment transportation are uncertain, the long- term consequences with investigated engineering measures can be concluded to have negative impact on the sustainability of the reach, however short-term improvements can be achieved. Other factors such as stability, material use, economics and marine conditions were not treated in this project but are vital for a reliable solution.

Thesis (M.L.A.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 54-57) Also available in print.

The assessment of change in river systems requires reference conditions. However, most large navigable waterways in the United States and elsewhere around the world have a wealth of archival data because of past engineering projects and flood control efforts. For example, in the United States, large quantities of archival data are available for the Mississippi River System which can be used to assess historical baseline conditions and change. Maps, charts, surveys, structure-history databases, and other quantitative measurements stretch back 100 to as much as ~200 years. The purpose of his dissertation was to develop a robust methodology from which to use these archival data to establish historic reference conditions in order to quantify and assess the causes of change in flood levels. Since the early 19th century, the Middle and Lower Mississippi River (MMR and LMR) have been intensively modified for flood protection and commercial navigation. In order to quantify the effects of levee expansion, channel modification, and land-cover change upon flood stages, a 1-D unsteady flow model was developed for multiple historical reference conditions ("retro-models") for three large study reaches (225-315 km each): one along the MMR and two reaches along the LMR. For each reference condition, four 1-D unsteady-flow models were developed. These models include a calibrated model of actual conditions and three "scenario" models: 1) a model with levees of the next time step, 2) a model with the channel geometry of the next time step, and 3) a model with floodplain roughness (i.e., land cover) of the next time step. Comparison of the model for actual conditions and the scenario models provide a quantitative assessment of levee expansion, channel modification, and land-cover change on stage. Comparison of the modeling results for this investigation showed significant changes in stage for equal discharges between each of the modeled time steps. Changes in stage for the three modeled reaches ranged from -3.1 to 4.4 m. The largest changes in flood stage were found along the MMR. The largest decreases in flood levels were found along the LMR between Obion and Memphis, TN. These results confirm previous hydrologic analyses, but show stage-changes as continuous longitudinal profile and not just at gaging stations. Scenario modeling suggests that the majority (38 to 70%) of the changes in flood stage on the LMR and MMR study reaches can be attributed to changes in channel geometry and hydraulic roughness. Levees were the next largest contributor to changes in flood stage. For time steps with significant levee expansion, these structures increase stage up to 1.0 m. Observed changes in floodplain land cover were associated with little (or none) of the increase in flood stage. These result show changes in channel geometry and roughness related to river engineering tools employed for the facilitation of navigation and flood conveyance are the principal drivers of historic changes in flood stages along the LMR and MMR. The results from the 1-D scenario model assessment suggest wing dikes may broadly affect flow conveyance in two ways: (1) through direct interaction with flow and (2) indirectly by their effects on channel geometry and roughness. Direct effects of wing dikes on flood stage were assessed by constructing two 2-D hydrodynamic models: (1) a calibrated model of actual conditions (i.e., with wing dikes) and (2) a scenario model without wing dikes, for a heavily modified reach of the MMR. Comparison of the model of actual conditions and model without wing dikes revealed that direct effects of wing dikes increase stage, modestly by only 0.1 to 0.5 m, depending on discharge and location. Wing dikes also were shown to increase and decrease channel velocities. Local increases in flow velocities of up to 0.4 m/s were found along portions of the main channel. Decreases in flow velocity by as much as -2.0 m/s were found along the edge of the channel within the wing dike fields. The direct effects of wing dikes on flow conveyance also were observed to decrease with an increase in flow, a result that runs contrary to the total cumulative effects of wing dikes observed empirically. These results suggest that the indirect effects are the likely cause of the historic decreased in flood flow conveyance and large-scale increases in flood stages along portions of the MMR.

This dissertation is a history of efforts to develop the Litani River in Lebanon. Under French rule (1920–43), development projects shaped an unequal distribution of infrastructure that privileged Christian and urban regions. A cohort of nationalist Lebanese engineers advocated developing the Litani River, in Lebanon’s Shi‘a-majority southwest, as a means to foster national unity by resolving inequalities among Lebanon’s religious communities. The resulting Litani project (1955–65) was Lebanon’s first grand-scale hydroelectric project. The United States, France, and the World Bank made the project central to their respective strategies in the decolonizing Middle East. Lebanese engineers competed and collaborated with European and American experts to design infrastructure that connected the Litani, and Lebanon’s hinterland, with the capital, Beirut. Economists, religious leaders, farmers, and communists debated infrastructure designs in Beirut’s bourgeoning public sphere. The completed infrastructure generated electricity for Beirut’s consumers by extracting water from the impoverished rural margins. The World Bank deemed the project a qualified success as an investment. But most in Lebanon considered it a monumental failure because the infrastructure did not meet urgent needs. Rather, the infrastructure materialized preexisting inequalities between Beirut and its peripheries, which provided a visible injustice that a rural Shi‘i political-religious movement mobilized to demand equal rights. Unlike familiar histories of development in which rural communities resist state intrusion, in Lebanon, rural actors and engineers sought to build a larger and more equitable state by constructing socially just infrastructure.

The aim of this report is to contribute to the base of knowledge on environmental monitoring by increasing understanding of how eDNA, electrofishing and sampling fishing may be used to examine fish biodiversity. It also aims at understanding if fish indexes developed within the Water Framework Directive reflect biodiversity, as well as the potential of eDNA data to serve as input to these indexes. This was done by using three different approaches. Firstly, in order to establish which of the methods eDNA, electrofishing and sampling fishing is more suitable to measure the different dimensions of biodiversity (species richness, species evenness and genetic diversity), a literature review comparing the different methods was carried out. It was found that eDNA yields a more detailed results for species richness, electrofishing yields better results for species evenness and sampling fishing is outperformed by eDNA and electrofishing alike. Both electrofishing and sampling fishing may collect data for genetic diversity analysis, however electrofishing outperforms sampling fishing with regards to amount of species caught, making electrofishing a more suitable data collection method. Secondly, in order to gain insight on practical usage of eDNA, a case study of Spjutmo (Dalarna county) was reviewed. It was established that eDNA generated more detailed information of species richness in the case of Spjutmo (as compared to electrofishing). The relative abundance data generated by the eDNA study might be seen as a measure of species evenness. However, electrofishing yielded data which may serve as input to species evenness indices. To the best knowledge of the author, none of the methods generated data on genetic diversity in this specific case. Officials from the energy company Fortum and the county board of Dalarna were also interviewed in order to get insight on what potential they see for eDNA to contribute to environmental monitoring. Both officials point at the ability to estimate abundance as a desired feature, hence a better understanding of what the relative abundance results indicates is wanted. The two interviews indicate that this understanding is an important feature to develop in order to make metabarcoding studies effective in current environmental monitoring. Thirdly, in order to understand if fish indexes developed within the Water Framework Directive reflect biodiversity, a literature review was performed. It was found that, all but one of the compared indexes incorporates or somewhat incorporates species richness. However, only five indexes are indicative or somewhat indicative of species richness. Species evenness is incorporated or somewhat incorporated by two indexes, which are also indicative or somewhat indicative of species evenness. None of the indexes incorporate or indicate genetic diversity. Within the third literature review, the potential of eDNA data to serve as input to current fish-based indexes developed within the Water Framework Directive, was studied. It was found that eDNA data may serve as input to only one index in its present form. However, five indexes also use proportional information (e.g. proportion of tolerant species), which possibly could be provided by eDNA data. The index where usage of eDNA data is currently possible uses presence-absence information. / Målet med denna rapport är att bidra till kunskapsläget kring miljöövervakning genom att öka förståelsen för hur eDNA, elfiske och provfiske kan användas för att undersöka fisk biodiversitet. Målet är också att förstå om fisk-index utvecklade inom ramen för det Europeiska vattendirektivet reflekterar biodiversitet samt om data från eDNA kan utgöra input till dessa index. För att uppfylla dessa mål användes tre metoder. För att etablera vilken av metoderna eDNA, elfiske och provfiske är mer lämpad att mäta de olika dimensionerna av biodiversitet (artrikedom, distribution av arter och genetisk diversitet), genomfördes en litteraturstudie. Slutsatsen kunde dras att eDNA mäter artrikedom med högst noggrannhet, elfiske mäter distribution av arter mer detaljerat och att provfiske överträffas av både eDNA och elfiske i alla dimensioner. Både elfiske och provfiske kan samla data för analys av genetisk diversitet, men elfiske överträffar provfiske gällande hur många arter som fångas, vilket gör elfiske mer lämpligt som metod att samla in data för genetisk analys. För att få praktisk insikt i ett fall där eDNA använts, granskades en fallstudie från Spjutmo (i Dalarnas län). eDNA genererade mer detaljerad information om artrikedom än elfiske i detta fall. Datan genererad av eDNA kring relativ abundans mellan arter skulle kunna tolkas som ett mått på distribution av arter. Data genererad av elfiske kan å andra sidan användas som input till olika index för distribution av arter. Författaren veterligen, genererade varken eDNA eller elfiske mått på genetisk diversitet i detta specifika fall. Två personer, en från Fortum och en från länsstyrelsen Dalarna intervjuades också för att få insikt i deras syn på potentialen av att använda eDNA som ett miljöövervakningsverktyg. Båda intervjupersonerna pekade på att en bättre förståelse av de relativa abundansvärdena indikerar är önskad. Båda intervjupersonerna pekade på att det är en viktig aspekt för att metabarcoding studier ska vara effektiva i nuvarande miljöövervakning. För att förstå om fisk-index utvecklade för EU’s vattendirektiv reflekterar biodiversitet, genomfördes en komparativ litteraturstudie av index. Alla index förutom ett inkorporerar eller delvis inkorporerar artrikedom. Bara fem indikerar eller delvis indikerar artrikedom. Distribution av arter inkorporeras eller delvis inkorporeras av två index som också indikerar eller delvis indikerar distribution av arter. Inom den komparativa litteraturstudien av index, studerades även potential att fungera som input av data genererad av eDNA till indexen. Data genererad av eDNA kan i dagsläget fungera som input till ett av indexen. Fem index använder någon form av proportionell data (t.ex. proportion av toleranta arter), som möjligen skulle kunna ges av eDNA. Indexet till vilket det är möjligt att använda eDNA data använder närvarande-ej närvarande information som input.

As all of Sweden's hydropower is to be re-examined within a 20-year period, methods are needed to carry out ecological investigations of dammed waterways. The first aim of this thesis is to evaluate whether methods for salmon and trout habitat mapping take all relevant indicators into account. In addition, the report aims to investigate which factors affect the results of habitat mapping based on hydraulic simulation and to investigate whether this method can be made more efficient through the use of simpler models, drone images and calculations. The work began with a literature study. A model was then built over a dammed stretch where mapping through hydraulic simulation was carried out. A mapping was then carried out on another stretch of stream based on a simpler model, drone images and shadow calculations, in parallel with a field mapping. The results of the literature study showed that the mapping methods capture the physical indicators well and indirectly link to certain chemical and ecological indicators. The method could be improved by including the water's nitrogen content and pH in the assessment.Important factors in habitat estimation with hydraulic simulation are the flow and the accuracy of the terrain model, as well as how the result is produced. The result from mapping with a simpler hydraulic model showed large deviations from the results obtained in the field, with respect above all to depth and width. Drone imagery for substrate assessment works well in shallow and clear water bodies. Shadow calculations based on how they were applied in this work to habitat mapping have not given satisfactory results, why the method needs to be developed. / Då all Sveriges vattenkraft ska omprövas inom en 20-årsperiod behövs metoder för att genomföra ekologiska utredningar av uppdämda vattendrag. Det första syftet med detta examensarbete är att utvärdera om metoder för lax- och öringhabitatkartering tar hänsyn till alla relevanta indikatorer. Därutöver syftar rapporten till att undersöka vilka faktorer som påverkar resultatet vid habitatkartering utifrån hydraulisk simulering och att undersöka om denna metod kan effektiviseras genom användning av enklare modeller, drönarbilder och beräkningar. Arbetet inleddes med en litteraturstudie. Därpå byggdes en modell upp över en indämd sträcka där kartering genom hydraulisk simulering genomfördes. En kartering genomfördes sedan på en annan strömsträcka utifrån en enklare modell, drönarbilder och skuggberäkningar, parallellt med en fältkartering. Litteraturstudiens resultat visade på att karteringsmetoderna väl fångar upp de fysikaliska indikatorerna och indirekt kopplar till vissa kemiska och ekologiska indikatorer. Metoden skulle kunna förbättras genom att ta in vattnets kvävehalt och pH i bedömningen. Viktiga faktorer vid habitatskattning med hydraulisk simulering är flödet och terrängmodellens noggrannhet, samt klassningen för vad som anses som goda habitat. Resultatet från kartering med en enklare hydraulisk modell visar på stora avvikelser mot resultaten inhämtade i fält, med avseende på framför allt djup och bredd. Drönarbilder för substratbedömning fungerar väl vid grunda och klara vattendrag. Skuggberäkningar utifrån hur de i detta arbete applicerats på habitatkartering har inte gett tillfredställande resultat, varför metoden behöver utvecklas.

Bubble curtains offer a potential solution for hindering downstream migrating fish from passing through the turbines of hydropower plants, by instead guiding them to a safe passage. Compared to the conventional method of using low-inclined bar racks close to the turbine intake, bubble curtains are considerably cheaper, especially for large scale hydropower plants. In this work bubble curtains are evaluated through an experimental parametric study, mainly regarding two quantities, defined here as the overall bubble coverage of the background, as well as the occurrence of large tears in the curtain. The examined parameters cover the design of the device that generates the bubbles, the positioning of the device, as well as the flow condition of the water. The bubble curtain was filmed with underwater cameras and image analysis was performed using image segmentation in MATLAB. Results indicate that the total air flow should be chosen high, around 200-500 nl/min/m. The number of holes the air is distributed across is of little importance, except in the area closest to the air outlets, where permanent tears may occur inbetween holes if the distance is to great. Smaller holes (<1mm) are preferable to larger holes (>1 mm), but the difference is small compared to the effect of the total air flow. In flowing water, a smaller angle of attack against the current is better based on the defined quantities, but it will also result in a longer and therefore more expensive device. The bubble curtain should not be placed where mean water velocities exceed 0,75 m/s, since it will result in an inclination with the current close to that of bar racks designed to guide fish towards the surface. Furthermore, at these water velocities some fish may have difficulties following the curtain, due to their limited swimming capabilities.