[EN] Climate change has occurred in Indonesia, for example, increasing the surface air temperature, including in the Upper Citarum watershed. This phenomenon leads to a lack of water in the dry season, which lowers agriculture production and remains a great obstacle for agricultural activity. Meanwhile, human activity has produced severe LULC changes within the Upper Citarum watershed. This occurs due to the demands of the ever-increasing population growth in the region. As a result, rice field and forested areas have been sacrificed to compensate the urban increment. The general objective of this dissertation is to understand and analyze the impact of climate and LULC changes on the hydrological process and their relationship with historical and future changes by using spatially distributed modeling on the Upper Citarum tropical catchment. The distributed model TETIS has been implemented to obtain the results of past and future scenarios on the water and sediment cycles. Annual historical bathymetries in the reservoir were used to calibrate and validate the sediment sub-model involving Miller's density evolution and trap efficiency of Brune's equation. Climate change has been considered under RCP 45 and RCP 85 trajectories. Meanwhile, to overcome the LULC problem, historical and future LULCs have been studied. LCM model was used to forecast the LULC in 2029. The forecasted results of LCM model show, on one hand, a continuation in the expansion of urban areas at the expense of the contiguous rice fields. The results determined that deforestation and urbanization were the most influential factors for the alteration of the hydrological and sedimentological processes in the Upper Citarum Catchment. Thus, it decreases evapotranspiration, increases water yield by increasing all its components; overland flow, interflow and baseflow. The changes in LULC are currently producing and will produce in the future, a relatively small increment of erosion rates, increasing the area exceeds Tsl erosion. Sediment yield will increase in 2029 as the result of erosion increment. Other LULC scenarios such as conservation, government plan and natural vegetation scenarios are expected to have an increment in total evapotranspiration, the water yield is expected to decrease. Flood regime, erosion and sedimentation are reduced dramatically. Hence, it leads to a massive increment of reservoir and hydropower lifetime signed by a very long period of the lifetime. Climate change alters the magnitude of water balance and can be identified from the shift of infiltration, overland flow, interflow, baseflow and water yield. Those increments finally change the flood regime, catchment erosion. RCP 85 trajectory gives a bigger impact compared to RCP 45 trajectory on hydrological and sediment cycle. . LULC change results a bigger impact on water balance, flood regime, erosion and sedimientation. The combination of climate and LULC change give a bigger impact on the flows of water balance, erosion, flood, sedimentation and will be catastrophic for the hydropower operation of the Saguling Dam. / [ES] El cambio climático ha afectado a Indonesia, por ejemplo, incrementando la temperatura del aire en la superficie, incluso en la cuenca del Upper Citarum. Este fenómeno conduce a la falta de agua en la estación seca, reduciendo la producción agrícola lo que es un gran obstáculo para su actividad. Además, la actividad humana ha producido cambios severos en LULC en la cuenca del Upper Citarum, Indonesia. Esto se debe al elevado crecimiento de la población en la región, por el que se han convertido campos de arroz y áreas boscosas en suelo urbano. De esta forma, el objetivo general de esta tesis es comprender y analizar el impacto de los cambios climáticos y LULC en el proceso hidrológico y su relación con los cambios históricos y futuros mediante el uso de modelos distribuidos espacialmente en la cuenca tropical del Upper Citarum. El modelo distribuido TETIS se ha implementado para obtener los resultados de escenarios pasados y futuros en los ciclos de agua y sedimentos. Se usaron batimetrías históricas anuales en el embalse para calibrar y validar el submodelo de sedimentos que involucra la evolución de la densidad de Miller y la eficiencia de retención de la ecuación de Brune. Con el fin de arrojar más luz sobre estos problemas, el escenario de cambio climático se ha implementado en base al modelo de cambio climático bajo las trayectorias RCP 45 y RCP 85. Además, para intentar resolver el problema LULC, también se ha implementado el LULC histórico y futuro. El modelo LCM se usó para pronosticar el LULC en 2029 y los resultados muestran, por un lado, una continuación en la expansión de las áreas urbanas a expensas de los arrozales contiguos. Los resultados determinaron que la deforestación y la urbanización fueron los factores más influyentes para la alteración de los procesos hidrológicos y sedimentológicos en la cuenca del Upper Citarum. Por lo tanto, disminuye la evapotranspiración, aumenta la producción de agua al aumentar todos sus componentes; escorrentía, interflujo y flujo base. Los cambios en LULC están produciendo y producirán, un incremento relativamente pequeño de las tasas de erosión, aumentando el área excede la erosión de Tsl. La producción de sedimentos aumentará en 2029 como resultado del incremento de la erosión. Se espera que otros escenarios de LULC como la conservación, el plan gubernamental y los escenarios de vegetación natural tengan un incremento en la evapotranspiración total, y se espera que la producción de agua disminuya. El régimen de inundación, la erosión y la sedimentación se reducen drásticamente. Por lo tanto, habrá un incremento de la vida útil del embalse y la energía hidroeléctrica. El cambio climático altera la magnitud del equilibrio hídrico y puede identificarse a partir del cambio de infiltración, escorrentía, interflujo, flujo base y producción de agua. Esos incrementos finalmente cambian el régimen de inundación y erosión de la cuenca. La trayectoria RCP 85 tiene un mayor impacto en comparación con la trayectoria RCP 45 en el ciclo hidrológico y de sedimentos. El cambio de LULC tiene un mayor impacto en el balance hídrico, el régimen de inundación, la erosión y la sedimentación. La combinación del cambio climático y LULC tiene un mayor impacto en los flujos de equilibrio hídrico, erosión, inundación, sedimentación y será catastrófico para la operación hidroeléctrica de la presa Saguling. / [CA] El canvi climàtic ha afectat Indonèsia, per exemple, incrementant la temperatura de l'aire en la superfície, inclús en la conca de l'Upper Citarum. Aquest fenomen conduïx a la falta d'aigua en l'estació seca, reduint la producció agrícola, el que és un gran obstacle per a la seua activitat. A més, l'activitat humana ha produït canvis severs en LULC en la conca de l'Upper Citarum, Indonèsia. Açò es deu a l'elevat creixement de la població en la regió, motiu pel qual s'han anat convertint camps d'arròs i àrees boscoses en sòl urbà. D'aquesta manera, l'objectiu general d'aquesta tesi és comprendre i analitzar l'impacte dels canvis climàtics i LULC en el procés hidrològic i la seua relació amb els canvis històrics i futurs per mitjà de l'ús de models distribuïts espacialment en la conca tropical de l'Upper Citarum. El model distribuït TETIS s'ha implementat per a obtindre els resultats d'escenaris passats i futurs en els cicles de l'aigua i sediments. Es van usar batimetries històriques anuals en l'embassament per a calibrar i validar el submodel de sediments que involucra l'evolució de la densitat de Miller i l'eficiència de retenció de l'equació de Brune. Amb la finalitat de donar més llum a aquests problemes, l'escenari de canvi climàtic s'ha implementat basant-se en el model de canvi climàtic davall les trajectòries RCP 45 i RCP 85. A més, per a intentar resoldre el problema LULC, també s'ha implementat el LULC històric i futur. El model LCM es va usar per a pronosticar el LULC en 2029 i els resultats mostren, d'una banda, una continuació en l'expansió de les àrees urbanes a costa dels arrossars contigus. Els resultats van determinar que la desforestació i la urbanització van ser els factors més influents per a l'alteració dels processos hidrològics i sedimentològics en la conca de l'Upper Citarum. Per tant, disminuïx l'evapotranspiració, augmenta la producció d'aigua en augmentar tots els seus components; escorrentia, interflux i flux base. Els canvis en LULC estan produint i produiran, un increment relativament xicotet de les taxes d'erosió, augmentant l'àrea excedix l'erosió de Tsl. La producció de sediments augmentarà en 2029 com a resultat de l'increment de l'erosió. S'espera que altres escenaris de LULC com la conservació, el pla governamental i els escenaris de vegetació natural tinguen un increment en l'evapotranspiració total, i s'espera que la producció d'aigua disminuïsca. El règim d'inundació, l'erosió i la sedimentació es reduïxen dràsticament. Per tant, hi haurà un increment de la vida útil de l'embassament i l'energia hidroelèctrica. El canvi climàtic altera la magnitud de l'equilibri hídric i pot identificar-se a partir del canvi d'infiltració, escorrentia, interflux, flux base i producció d'aigua. Eixos increments finalment canvien el règim d'inundació i erosió de la conca. La trajectòria RCP 85 té un major impacte en comparació amb la trajectòria RCP 45 en el cicle hidrològic i de sediments. El canvi de LULC té un major impacte en el balanç hídric, el règim d'inundació, l'erosió i la sedimentació. La combinació del canvi climàtic i LULC té un major impacte en els fluxos d'equilibri hídric, erosió, inundació, sedimentació i serà catastròfic per a l'operació hidroelèctrica de la presa Saguling. / thank the Directorate General of Higher Education of Indonesia (DIKTI), for granting me the opportunity to pursue PhD study and adventure in Europe. The authors are also thankful to the Spanish Ministry of Economy and Competitiveness through the research projects TETISMED (CGL2014-58127-C3-3-R) and TETISCHANGE (RTI2018-093717-B-I00). / Siswanto, SY. (2020). Impact Evaluation of Future Climate and Land Use Scenarios on Water and Sediment Regime using Distributed Hydrological Modelling in a Tropical Rainforest Catchment in West Java (Indonesia) [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/153152 / TESIS

Coastal areas around the world have been recognized as largely impacted by anthropogenic activities resulting in pollution of marine sediments. In Sweden, surveys conducted along the coastline of the Bothnian Bay have identified a total area of about 29 km2 as fiber rich sediments. In the Bureå sea area near Skellefteå vicinity, Västerbotten county, elevated levels of mercury (Hg), methyl-Hg, arsenic (As), copper (Cu), lead (Pb), cadmium (Cd), zinc (Zn) and polycyclic aromatic hydrocarbons (PAH) have been classified and believed to be mainly affected by emissions from a pulp and paper industry formerly active on a nearby headland.  Contaminants in sediments are of concern as continuous dispersion can adversely affect the benthic community. To isolate contaminants and reduce their bioavailability, in-situ thin-layer capping using an active material is one suitable approach. This type of remediation method, using biochar mixed with bentonite clay will be implemented on a pilot scale in the sea area outside of Bureå in the spring of 2021. However, bentonite is a relatively expensive material yielding a need to further develop the selection of capping materials suitable to aid in the deposition of biochar in an active thin-layer cap. In this thesis, biochar-based thin layer caps mixed with bentonite clay, rock dust of two grain sizes and a concrete-based slurry was evaluated on their physicochemical properties and efficiency for preventing release of trace elements from sediment to the overlying water. This was conducted by a laboratory column experiment where four set ups were performed: (1) no capping for sediment control, (2) only capping material for material control, (3) sediment mixed with biochar and (4) sediment capped with each material mixed with biochar. Three times during an 8-week test period, 60 mL of the overlying water in the columns was extracted and sent for trace element analysis.  The experimental set up revealed that the capping layers effectively prevent release of trace elements trough the sediment to the overlying water. The concrete slurry showed suitable settling properties and negligible loss of biochar in the set-up of the columns. Also, the biochar+concrete slurry thin-layer cap displayed the highest efficiency for preventing and/or delaying release of As, P, Cu, Fe, Mn and SO4.

No description available.

Thesis advisor: Gail C. Kineke / An observational study was conducted from 2013 to 2016 to investigate suspended-sediment transport processes in the stratified Connecticut River estuary. Time-series measurements of velocity and suspended-sediment concentration from the upper estuary were analyzed to determine the relative importance of different processes driving sediment flux under highly-variable river discharge. Results indicate that under high discharge the salt intrusion is forced towards the mouth causing large seaward sediment fluxes throughout the water column. Seaward fluxes are dominated by mean advection, with some contribution due to tidal pumping. Under low discharge the salt intrusion extends to the upper estuary, advancing as a bottom salinity front during each flood tide. Stratification and strong velocity shear during the ebb tide cause the upper and lower water column to become dynamically decoupled. Sediment flux near the bed is landward throughout the tidal cycle despite the net seaward depth-integrated flux, and is almost fully attributed to the mean estuarine circulation. River discharge is the primary factor affecting the magnitude and direction of sediment flux because of its high variability and direct connection to the salt-wedge dynamics. A generalized three-phase conceptual model describes suspended-sediment transport in shallow, stratified estuaries with low trapping efficiencies. First, fine sediment bypasses the estuary during high river flows and exports to the coastal ocean where a portion of this sediment is temporarily deposited outside the mouth. Second, during low discharge offshore mud deposits are reworked by wave- and tidally-driven currents and some sediment is advected back into the estuary with the advancing salt intrusion that transports sediment landward. Third, spatial salinity gradients facilitate sediment transport from the main channel to channel margins, marshes and off-river coves where it is retained and deposited long-term, as demonstrated in prior studies. This re-introduction and trapping of recycled sediment under low-discharge conditions can have important implications for pollutant transport, shoaling of navigation channels and harbors, and salt marsh accretion in the face of rising sea levels. / Thesis (MS) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

Accumulation of sediments in fishponds is a serious problem for today's aquaculture. High economical, organizational and time-consuming requirements are often the limit factor for many fish farmers. One of the available solutions has recently emerged bacterial-enzymatic mixtures, which thanks to modified bacteria cultures, have been able to reduce organic matter from sediment and improve overall physical and chemical water parameters. The aim of this diploma thesis was to verify the effect of the bacterial - enzymatic mixture PTP plus in laboratory and field conditions. For the laboratory experiment, was chosen a method with different concentrations of the PTP plus, under the controlled conditions of the glass containers. However, the results of the laboratory test did not confirmed significant effect of this bioenzymatic mixture on the reduction of the organic component of the sediment nor on the changes in the physical and chemical parameters of the water. But the influence at the visual properties of the water was confirmed in container with several times higher dose. Three small ponds near Bohuslavice near Konice, with a total area of approximately 2.5 hectares were chosen for the field experiment. The results of the field experiment also did not confirm the significant effect of the bio-enzymatic blend on the physical and chemical parameters of the water in the monitored localities. However, in the lowest location of the fishpond cascade, BOH I, was recorded slight reduction of sediment organic component.

Sediment erosion is one of the key challenges in hydraulic turbines from a design and maintenanceperspective in Himalayas and Andes. Past research works have shown that the optimization of theFrancis turbine runner blade shapes can decrease erosion by a signicant amount. This study conductedas a Master's Thesis has taken the proposed designs from past works and conducted a CFDanalysis on a single passage of a Francis runner blade to choose an optimized design in terms of erosionand eciency. Structural analyses have been performed on the selected design through one-way andtwo-way FSI to compare the structural integrity of the designs.Two types of cases have been considered in this thesis work to dene the boundary condition of thestructural model. In the rst case, a runner blade is considered to have no in uence of the joint andother stier components. In the second case, a sector of the whole runner has been modeled withnecessary boundary conditions. Both one-way and two-way FSI have been performed on the casesfor the designs. Mesh independent studies have been performed for the designs, but only for the rstcase, whereas in the second case, a ne mesh has been used to make the analysis appropriate.The loads have been imported into the structural domain from the uid on the interfaces for one-wayFSI. In the case of two-way FSI, the Multi-Field Solver (MFX) supported by ANSYS has been usedto solve the coupled eld analysis. A fully coupled FSI in ANSYS works by writing an input le inthe structural solver containing the information about the interfaces in the structural domain, whichis imported in the uid solver. The interaction between the two domains is dened in ANSYS-CFX,including the mesh deformation and solver setups. The results have been post-processed in CFX-Post,where the results from both the elds are included. It has been found that the structural integrity ofthe optimized design is better than the reference design in terms of the maximum stress induced inthe runner. The two-way FSI analysis has been found as an inevitable part of the numerical analysis.However, with the advancement of the computational capability in the future, there could be a greatscope in the research eld to carry out a fully-coupled transient simulation for the whole runner toget a more accurate solution.

Föroreningar till följd av mänskliga aktiviteter har pågått under åtskilliga år, i vissa fall började det­­ för flera hundra år sedan. Till en början var det synliga föroreningar som uppmärksammades, t.ex. fibrer och färgade avloppsvatten, men på 1960-talet blev man medveten om att även osynliga föroreningar i form av kemikalier kunde orsaka omfattande negativa miljöeffekter. I och med detta ställdes högre krav på att industrierna och kommunerna renade sina utsläpp, vilket medförde en betydande förbättring av den yttre miljön. Men än idag kvarstår stora problem med förorenade bottensediment. Huvuddelen av föroreningarna är oxiderat järn, sulfider, tungmetaller, karbonater och naturligt organiskt material. Vissa av dessa ämnen utgör allvarliga problem då de riskerar att spridas till ytvattnet och bioackumuleras i vattenlevande organismer. Syftet med detta arbete är att undersöka förutsättningarna för att utveckla en gemensam strategi för hållbar hantering av förorenade sediment i Östersjön. Den första insatsen var att kartlägga och presentera aktörer som arbetar med olika typer av frågeställningar som berör föroreningar i sediment. När aktörerna sedan är kartlagda återstår det att lyfta fram de frågeställningar som respektive aktörer anser vara av (största) vikt för att uppnå god balans i ekosystemet. Då de förorenade sedimenten är ett problem för alla stater runt Östersjön kommer arbetet med att sanera bottensedimenten ske över landsgränserna vilket innebär att arbetet måste uppfylla respektive lands miljölagar. Samtidigt som hanteringen och bortskaffandet av det muddrade materialet måste verka inom EU:s ramdirektiv för vatten, hav och avfall. Därför ges en inblick i hur och när EU:s miljödirektiv och Sveriges lagar skall tillämpas för denna typ av vattenverksamheter. Aktörerna som har kontaktas är allt från hamnorganisationer som muddrar för att; öka vattendjupet, utbyggnad/tillbyggnad, få bättre framkomlighet för båtar eller att ta bort förorenade sediment, till miljöorganisationer som vill bevara den biologiska mångfalden. Även myndigheter och statliga verk som arbetar för en friskare Östersjöregion kontaktades. HELCOM och EU-kommissionen har tagit fram aktionsplaner för att rädda Östersjön. Rapporten tar även upp internationella och regionala konventioner som har tillkommit för att skydda den marina miljön som också ligger till grund för EU:s miljöskydd. Slutsatsen av kartläggningen är att många av de kontaktade aktörerna, både nationella och transnationella, arbetar med att ringa in och krigsklassificera förorenade områden och rapportera förhöjda värden av farliga ämnena som ackumulerats i sedimenten. Resultatet av dessa mätningar används sedan till att spåra eventuella föroreningskällor men även för att ta fram strängare och tydligare riktlinjer för fortsatt miljöarbete. Slutsatsen av studierna av lagstiftningen visar att EU:s ramdirektiv möjliggör en viss tolkningsfrihet vilket ökar riskerna för att miljöskyddslagarna inte blir lika omfattande i respektive medlemsland. Det är inte fallet för den svenska miljölagstiftningen, den borde istället öppnas upp för möjligheten att klassa muddermassorna som naturmaterial och inte avfall. Det skulle underlätta arbetsgången för muddringsarbeten.

No description available.

Ice regime plays a significant role in River hydraulics and morphology in Northern hemisphere countries such as Canada. The formation, propagation and recession of ice cover introduce a dynamic boundary layer to the top of the stream. Ice cover affects the water velocity magnitude and distribution, water level and consequently conveyance capacity. A stable ice cover also tends to reduce bed shear and associated sediment transport, but bank scour and ice jamming events can increase sediment entrainment. These effects are even more intense during the ice cover break-up period when extreme conditions such as ice-jamming and release and mechanical ice cover break-up can locally accelerate the flow, and ice can mechanically scour the river bed and banks. The presence of ice has some important implications for hydro-electrical power generation operations too. The ice cover changes the channel conveyance capacity (and therefore increases the flood risk), may increase sediment transport and causes scouring, and is likely to block water intakes and turbines. The rate of water release should, therefore, be adjusted in the presence of the ice cover to avoid unwanted consequences on the dam structure and equipments as well as on the downstream channel and the environment. Even though the influence of ice cover on rivers is widely recognized, large gaps still exist in our understanding of ice cover processes in rivers. Two main reasons for such a shortage are the difficulty and danger involved in collecting hydraulic and sediment transport data under ice cover, especially during the unstable periods of freeze-up and break-up. In the absence of sufficient data, the applicability of available formulae and theories on hydraulic processes in ice-covered rivers cannot be extensively tested and improved. The purpose of this research mainly is a) to perform a continuous, in-situ monitoring of water velocity profiles, sediment loads and ice-cover condition during several years through winter field campaigns at a section of the Lower Nelson River, Manitoba, Canada.The Lower Nelson River is a regulated river (Manitoba Hydro). It receives augmented flow from the Churchill River Diversion, and is subject to operation of many hydro-electricity facilities, one of which is currently under construction, while others are planned to be constructed in the future. Due to the geographical location of the study reach, it is covered by ice and experiences severe ice condition for several months during the year. b) Analysis of the collected data in order to study the impact of ice cover on the hydraulic properties and sediment conveyance capacity at the study reach and c) using the insight gained from the field data analysis to improve a river ice simulation model to apply in the study of Lower Nelson River ice regime. The selection of the Lower Nelson river is motivated by intention of Manitoba Hydro (MH) ,as the industrial partner in this research, to study the winter flow regime at the Lower Nelson River. Manitoba Hydro operates several dams on the Lower Nelson River and is considering more hydropower developments in the future. This study is composed of six steps as are described in the following main steps. Step 1: Selection of potential study sites and data collection techniques: The particular study site for this research is located immediately upstream of Jackfish Island, between Limestone generating station and Gillam Island in Lower Nelson River, Manitoba, Canada. River width at the study site location is about 1km. Water depth at the deployment site varies between 10-12 meters depending on both the time of year and the time of day due to hydropeaking fluctuations. Given the low accessibility to the field during winter time and considering the type of the required data, acoustic techniques were selected as the main approach for the field measurements. Two types of acoustic instruments, Acoustic Doppler Current Profiler (ADCP) and Shallow Water Ice Profiling Sonar (SWIPS) are selected for field investigations in this study. Both of them were planned to be deployed in the river for an extended period of time in order to record necessary data during the ice cover and open water periods. Step 2: Data acquisition. After the site selection and defining the appropriate techniques, data acquisition has been started through a series of annual field measurement campaigns starting from winter 2012. Measured data mainly consist of water velocity and sediment suspension during various ice cover stages, including river ice break-up. The velocity profiles are analyzed to determine dynamic changes in boundary shear stress and hydraulic resistance and stresses in the flow during the both open water and ice cover periods. Step 3: Data analysis and development/testing of roughness and sediment transport formulas. Several aspects of river-ice interactions are covered in the recorded data including ice cover condition and cover thickness variation, river hydraulic characteristics such as depth and velocity and finally information about the concentration of suspended particles. These data are analyzed to define the behavior of the ice cover and river during different ice stages. Ice effect on river conveyance capacity is also evaluated . The accuracy of common assumptions in composite roughness calculations in rivers is estimated and a new approach is developed and validated using the field observations and measurements. Ice cover influence on suspended sediment concentration is also studied as the other part of this research. Considering the type of the river sediment load (mostly bed load) available methods for sediment transport simulation are studied and applied for estimation of the sediment transport under ice cover condition. According to the results, the most suitable methods were planned to be a part of the river ice numerical simulation model, developed in this study. Turbulent characteristics in ice covered flows are also studied through two years of data recordings. Acoustic Doppler Current Profiler employed in this study is programmed for appropriate recording of the water velocity for this purpose. Results are analyzed and turbulent structures in the river are studied in this research as well. Step 4: Testing of Hatch-MH’s river ice simulation model. A numerical model has been selected in order to simulate the river ice process at the study site (LNR). ICESIM, a steady state, one-dimensional river ice process model originally developed in 1973 by Acres International Limited (now Hatch), is selected for this study.ICESIM is originally developed in FORTRAN and is capable of predicting the progression and stabilization of river ice cover. Step 5: Improvement of Hatch-MH’s river ice simulation model: ICESIM model is converted to Matlab as the first step of the model improvements. A Graphical User Interface (GUI) is designed for the program which facilitates the assessment of model performance during the simulation leads to a more user-friendly model to operate. The new model, ICESIMAT is calibrated and evaluated based on the conducted field studies. Simulation capabilities of ICESIMAT are improved in the form of extended or additional subroutines to enhance its capabilities in the simulation of river ice processes and sediment transport. The current version of ICESIMAT is a steady state model, capable of simulating river ice , river hydrodynamic characteristics and sediment transport along the study reach. Though the model is restricted in the terms of the dimensions of the simulation (only one dimensional) its lower computational cost, permits a longer study reach to be simulated (in the scale of hundred kilometers instead of couple hundred meters in three dimensional simulation). ICESIM model is unable to simulate the break-up period which reduces the model capability in the simulation of the complete cycle of river ice. New subroutines are designed and added to extend the model capability to include simulation of ice processes during the ice cover break-up and finally to calculate the sediment transport under the ice cover. Step 6: As the final step, the new subroutines are adjusted and linked to the main improved code, providing a new framework for dynamic ice cover simulation, more prepared for further future improvements both in terms of conceptual and programming aspects of the river ice modeling . The new Matlab basis of the code facilitates upgrading the model to include more complicated processes like river ice jam simulations. As the general result of this thesis, we have a better understanding of hydraulics and sediment transport processes in ice covered rivers ( direct and indirect measurements of river hydraulics characteristics), improved formulas for these processes (including more involving parameters) and a better version of the river ice simulation model (capable of simulating the complete river ice processes) for the contributors to this study in the industry.

Climate change and eutrophication, accelerated by anthropogenic activities, have impacted aquatic ecosystems worldwide. These impacts have stimulated the expansion of cyanobacterial blooms which pose severe threats to ecosystem functioning, environmental health, and the economy. However, the long-term effects of environmental change on bloom-forming cyanobacteria are not well understood as traditional paleolimnological approaches are of limited use in the reconstruction of cyanobacterial dynamics through time. Here, sediment DNA (sedDNA) was used to investigate long-term cyanobacterial trends using sediments from two experimental (fertilized L227 and acidified L223) and two reference (L224 and L442) lakes in the Experimental Lakes Area, Canada. First, to determine whether taxonomic bias might arise from the cyanobacterial sediment record, I performed a 1-year incubation experiment comparing the degradation rates of selected cyanobacterial genes under contrasting environmental conditions. Based on first-order linear decay models, Synechococcus sp. (Synechococcales) decayed the slowest under cold, anoxic conditions, followed by Trichormus (Nostocales), then Microcystis (Chroococcales), suggesting differential preservation of DNA. I then compared the quantitative performance of droplet digital polymerase chain reaction (ddPCR) and high-throughput sequencing (HTS) for the analysis of sedDNA and found that the ddPCR results were more consistent with the known history of the lakes. Furthermore, ddPCR showed that cyanobacterial abundance increased over the past century in all study lakes, but the greatest increase was observed in experimentally fertilized L227. HTS revealed shifts in the cyanobacterial community towards Nostocales dominance and a decrease in alpha diversity in response to phosphorus-only additions. An increase in abundance of the mcyE gene (indicative of microcystin producing taxa) was uniquely observed in L227 when nitrogen additions ceased. Heating degree days were important in explaining variation in the cyanobacterial community composition in all lakes, but nutrients had a greater influence on the L227 community. When sediment data were compared to historical surface water phytoplankton records, moderate to strong correlations between the two archives were found, validating the use of sedDNA. This research demonstrated that sedDNA can elucidate cyanobacterial trends at the community, population, and species level over multidecadal timescales in response to environmental change.