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1
Ropp, David L. "Numerical study of shallow water models with variable topography". Diss., The University of Arizona, 2000. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_2000_165_sip1_w.pdf&type=application/pdf.
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Koçyigit, Müsteyde Baduna. "Numerical modelling of wind-induced circulation in lakes and reservoirs". Thesis, Cardiff University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412516.
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Arnold, Robert John. "Mathematical modelling of wind effects on closed lakes /". Title page, contents and summary only, 1985. http://web4.library.adelaide.edu.au/theses/09PH/09pha758.pdf.
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McInerney, David J. "A triangular grid finite-difference model for wind-induced circulation in shallow lakes /". Title page, table of contents and abstract only, 2005. http://web4.library.adelaide.edu.au/theses/09PH/09phm4790.pdf.
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Jung, Kyung Tae. "On three-dimensional hydrodynamic numerical modelling of wind induced flows in stably stratified waters : a Galerkin-finite difference approach". Title page, contents and summary only, 1989. http://web4.library.adelaide.edu.au/theses/09PH/09phj95.pdf.
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Shimizu, Kenji. "Application of modal analysis to strongly stratified lakes". University of Western Australia. Faculty of Engineering, Computing and Mathematics, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0079.
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Modal analysis for strongly stratified lakes was extended to obtain a better understanding of the dynamics of the basin-scale motions. By viewing the basin-scale motions as a superposition of modes, that have distinct periods and three-dimensional structures, the method provides a conceptual understanding for the excitation, evolution, and damping of the basin-scale motions. Once the motion has been decomposed into modes, their evolution and energetics may be extracted from hydrodynamic simulation results and field data. The method was applied to Lake Biwa, Japan, and Lake Kinneret, Israel, and used for a theoretical study. The real lake applications showed that winds excited basin-scale motions that had a surface layer velocity structure similar to the wind stress pattern. Three-dimensional hydrodynamics simulations of Lake Biwa indicated that most of the energy input from winds was partitioned into the internal waves that decayed within a few days. The gyres, on the other hand, received much less energy but dominated the dynamics during calm periods due to their slow damping. Analyses of field data from Lake Kinneret suggested that the internal waves, excited by the strong winds every afternoon, were damped over a few days primarily due to bottom friction. Theoretical investigations of damping mechanisms of internal waves revealed that bottom friction induced a velocity anomaly at the top of the boundary layer that drained energy from the nearly inviscid interior by a combination of internal wave cancelling and spin-down. These results indicate that gyres induce long-term horizontal transport near the surface and internal waves transfer energy from winds to near-bottom mixing. Modal structure of dominant basin-scale internal waves can induce large heterogeneity of nearbottom mass transfer processes. The method presented here provides a tool to determine how basin-scale motions impact on biogeochemical processes in stratified lakes.
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Yeates, Peter Stafford. "Deep mixing in stratified lakes and reservoirs". University of Western Australia. Centre for Water Research, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0046.
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The onset of summer stratification in temperate lakes and reservoirs forces a decoupling of the hypolimnion from the epilimnion that is sustained by strong density gradients in the metalimnion. These strong gradients act as a barrier to the vertical transport of mass and scalars leading to bottom anoxia and subsequent nutrient release from the sediments. The stratification is intermittently overcome by turbulent mixing events that redistribute mass, heat, dissolved parameters and particulates in the vertical. The redistribution of ecological parameters then exerts some control over the ecological response of the lake. This dissertation is focused on the physics of deep vertical mixing that occurs beneath the well-mixed surface layer in stratified lakes and reservoirs. The overall aim is to improve the ability of numerical models to reproduce deep vertical mixing, thus providing better tools for water quality prediction and management. In the first part of this research the framework of a one-dimensional mixed-layer hydrodynamic model was used to construct a pseudo two-dimensional model that computes vertical fluxes generated by deep mixing processes. The parameterisations developed for the model were based on the relationship found between lake-wide vertical buoyancy flux and the first-order internal wave response of the lake to surface wind forcing. The ability of the model to reproduce the observed thermal structure in a range of lakes and reservoirs was greatly improved by incorporating an explicit turbulent benthic boundary layer routine. Although laterally-integrated models reproduce the net effect of turbulent mixing in a vertical sense, they fail to resolve the transient distribution of turbulent mixing events triggered by local flow properties defined at far smaller scales. Importantly, the distribution of events may promote tertiary motions and ecological niches. In the second part of the study a large body of microstructure data collected in Lake Kinneret, Israel, was used to show that the nature of turbulent mixing events varied considerably between the epilimnion, metalimnion, hypolimnion and benthic boundary layer, yet the turbulent scales of the events and the buoyancy flux they produced collapsed into functions of the local gradient Richardson number. It was found that the most intense events in the metalimnion were triggered by high-frequency waves generated near the surface that grew and imparted a strain on the metalimnion density field, which led to secondary instabilities with low gradient Richardson numbers. The microstructure observations suggest that the local gradient Richardson number could be used to parameterise vertical mixing in coarse-grid numerical models of lakes and reservoirs. However, any effort to incorporate such parameterisations becomes meaningless without measures to reduce numerical diffusion, which often dominates over parameterised physical mixing. As a third part of the research, an explicit filtering tool was developed to negate numerical diffusion in a threedimensional hydrodynamic model. The adaptive filter ensured that temperature gradients in the metalimnion remained within bounds of the measured values and so the computation preserved the spectrum of internal wave motions that trigger diapycnal mixing events in the deeper reaches of a lake. The results showed that the ratio of physical to numerical diffusion is dictated by the character of the dominant internal wave motions.
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Kerimoglu, Onur. "Influence Of Large Scale Atmospheric Systems On Hydorology And Ecology Of Turkish Lakes". Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609272/index.pdf.
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Impacts of climatic changes on in-land waters of Turkey is a topic that has not been sufficiently investigated yet. In this study, some exploratory work have been performed to form the core of further studies on the subject. EOF (Empirical Orthogonal Function) analysis has been applied to SLP (Sea Level Pressure) field with a wide coverage (20-70N, 50W-70E). The dominant sources of variability in this atmospheric system have been shown to be driven by 3 circulation indices, NAO (North Atlantic Oscillation), EAWR (East Atlantic - West Russia) and EA (East Atlantic) patterns. Linkages between this atmospheric system and the hydro-meteorological properties (data compiled from governmental organizations) of major Turkish lake ecosystems has been investigated with use of ordinary correlation analysis and CCA (Canonical Correlation Analysis). The results revealed the heavy forcing of large scale SLP field on regional temperature and E--P (evaporation minus precipitation) fields. The 15-year data set of Lake Mogan, as the longest available found, was used to exemplify the approaches and methodologies that can be employed for understanding the influence of climate variability on biological properties of lakes. It was suggested that temperature and salinity, being effective on phytoplankton and zooplankton groups, mediate the climatic impacts in Lake Mogan.
9
Wallace, Helen Mary. "Application of layered models to the coastal dynamics of lakes and islands and to large-scale ocean circulation". Thesis, University of Exeter, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278303.
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Marti, Clelia Luisa. "Exchange processes between littoral and pelagic waters in a stratified lake". University of Western Australia. Centre for Water Research, 2004. http://theses.library.uwa.edu.au/adt-WU2005.0005.
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[Truncated abstract] The lake boundaries are an important source of sediment, nutrients and chemicals. For life inside the lake, the exchange between the lake boundaries (littoral) and lake interior (pelagic) is of central importance to Limnology as the net flux of nutrients into the water column is both the driving force and limiting factor for most algae blooms found during the stratification period. Consequently, the understanding of the relevant processes defining such an exchange is a further step toward a sound basis for future decisions by lake managers in order to ensure high water quality. The objective of this research was to investigate the physical processes responsible for the exchange of water and particles between the lake boundaries and the lake interior. An integrated approach using field experiments and 3D modelling as applied to Lake Kinneret (Israel) is presented. The field data revealed large-scale metalimnion oscillations with amplitudes up to 10 m in response to westerly diurnal winds, the existence of a well-defined suspended particle intrusion into the metalimnion of the lake, characterized by high concentrations of organic matter, and a well-mixed benthic boundary layer (BBL). The changes in the thermal structure explained the observed vertical and horizontal movements of the suspended particle intrusion. The horizontal advective transport via the metalimnion, associated with the velocities induced by the basin-scale mode-two Poincare wave, controlled the exchange between the lake boundaries and lake interior on daily time scales. The observed BBL over the lake slope varied markedly with time and space. Detailed comparison of simulation results with field data revealed that the model captured the lake hydrodynamics for time scales from hours to days. The model could then be used to extract the residual motions in the various regions of the lake. The residual motions below the surface layer were predominantly forced by the basin-scale internal wave motions, but the residual motion in the surface layer was found to be very sensitive to the curl of the wind field. The residual circulation was responsible for redistributing mass throughout the lake basin on time scales from days to weeks. A clear connection of dynamics of the BBL with the large-scale features of the flow was addressed. The time history of the mixing in the BBL and the resulting cross-shore flux was shown to vary with the phase of the basin-scale internal waves.
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Amadori, Marina. "On the physical drivers of transport processes in Lake Garda: A combined analytical, numerical and observational investigation". Doctoral thesis, Università degli studi di Trento, 2020. http://hdl.handle.net/11572/260790.
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This doctoral thesis provides the first comprehensive study on the physical processes controlling hydrodynamics and transport in Lake Garda. The investigation is carried out in parallel on three different levels: data collection and analysis, three-dimensional numerical modeling and theoretical study.
On the first level, data are collected by building up a network of research institutes and local administrations in the lake area. New data are acquired through traditional field campaigns (CTD, thermistor chains, satellite imagery), while a citizen-science approach, based on local knowledge harvesting, is successfully tested to gather qualitative data on surface circulation.
On the second level, a three-dimensional modeling chain is set up, by coupling one-way a mesoscale atmospheric model to a hydrodynamic model. Both models are validated on multiple temporal and spatial scales, allowing to identify the main interactions between the weather forcing and the hydrodynamic response of the lake.
Circulations in Lake Garda are found to be very sensitive to the thermal stratification, to the spatial distribution of the wind forcing and to the Earth’s rotation. Surface cyclonic gyre patterns develop in the lake as a residual outcome of alternating wind forcing of local breezes and differential acceleration induced by Earth’s rotation, whereas unidirectional currents flow under a nearly uniform and constant wind. Both model and observations evidences show that, under weak thermal stratification, Ekman transport activates a secondary circulations in the northern part of the lake, driving surface water to the deep layers and possibly preconditioning the lake for subsequent buoyancy-driven deep mixing events.
On the third level, the relevance of the Coriolis term in the equations of motion for relatively narrow closed basins is analytically addressed. The classical Ekman problem is solved by including the presence of lateral boundaries and a new analytical solution is formulated. The validity of the new solution is proved by numerical tests of idealized domains of different size, geographical location and turbulent regime, and on Lake Garda as a real test case. The meaningful length scales are discussed, and the significance of Rossby radious as a reference horizontal scale is disproved for steady-state circulations driven by wind and planetary rotation.
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Hall, Phillip. "Numerical modelling of wind-induced lake circulation". Thesis, University of Birmingham, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511642.
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The main objective of this study was to develop a stable numerical model capable of simulating the three-dimensional steady-state wind-driven circulation in a lake. Firstly, the relevant differential equations were derived from the Navier-Stokes equations by making certain simplifying assumptions. After comparing some standard finite difference schemes the decision was made to base the method of solution upon the alternating direction implicit technique. The depth- and layer-averaged equations were then expressed in a finite difference form before proceeding to solve the resulting sets of simultaneous equations by Gaussian elimination and back substitution. A step-like finite difference grid representation of the lake bed was used initially, before a more refined approach was adopted. The model also developed from a two-dimensional, vertical cross-section of the lake, to three dimensions, thus simulating the circulation throughout the entire lake. A field measurement programme was undertaken on Esthwaite Water, a small lake in the Lake District, and these measurements were used in comparisons with the numerically predicted results, to assess the models performance. Finally, the sensitivity of the results to some of the main model parameters was investigated by several series of simulations of the circulation in Esthwaite Water under various conditions.
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Callister, Eric V. "A Three-Dimensional, Time-Dependent Circulation Model of Utah Lake". DigitalCommons@USU, 2008. https://digitalcommons.usu.edu/etd/86.
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Spatial and temporal variations of Utah Lake’s flow field were modeled using the Estuary Lake and Computer Model from the Centre for Water Research (CWR-ELCOM) at the University of Western Australia as part of an effort to increase understanding of the lake’s natural processes in order to restore the lake to its pristine, clear-water state and preserve the habitat of the June sucker, an endangered species. The model was validated using temperature measurements taken by sensors in 2007. The water temperature was a strong function of air temperature and incident short wave radiation, and was influenced to a lesser degree by wind speed, wind direction, relative humidity, and cloud cover. The water currents were affected most strongly by wind speed and wind direction. The model also predicted the free drifting paths of June sucker larvae entering Utah Lake through the Provo and Spanish Fork Rivers between mid-April and July.
14
Graves, Kelly Elise. "Under-ice circulation in an Arctic lake : observations from two field seasons in Lake Kilpisjärvi, Finland". Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/52683.
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High spatial resolution CTD profiles and Acoustic Doppler Current Profiler velocity measurements show significant rotational basin-wide, under-ice circulation in May of 2013 and 2014 at Lake Kilpisjärvi, Finland (69°01'N, 20°49'E), a seasonally ice-covered, Arctic lake with negligible through-flow.
In 2013, a high-pressure horizontal density anomaly with vertically paired rotating circulations was observed. The estimated maximum cyclonic and anti-cyclonic azimuthal velocities magnitudes were 0.03 and 0.02 m s-¹. The Rossby radius (Rri), horizontal length scale at which rotational effects become as important as pressure effects, was estimated to be ∼ 160 m and the Rossby number(R⃘⃘⃘⃘⃘ ), the ratio of the centripetal acceleration to the Coriolis acceleration, ∼ 0.2. It is hypothesized that this circulation was driven by heat flux at the shorelines from warm incoming streams causing a density flow down the slopes to the centre of the lake where the flow converged. This flow was balanced with a shoreward flow beneath the ice. These flows were modified by the earth's rotation, which resulted in the rotational circulation observed.
In 2014, a cyclonic, low-pressure horizontal density anomaly was observed near the centre of the lake and was vertically paired with a weak anti-cyclonic anomaly in the top 10 m (mean depth of the lake is 19.5 m). The estimated azimuthal velocities had maximum cyclonic and anti-cyclonic magnitudes of 0.006 and 0.003 m s-¹. The anomaly was estimated to have Rri ∼ 240 m, with R⃘⃘ ∼ 0.12. It is hypothesized that this circulation was driven by sediment release of heat to the overlying water causing a tilt in the isopycnals near the shores of the lake that caused an inward pressure force that was balanced by the Coriolis force and, to a lesser extent, the centripetal acceleration force.
The 2013 observations were made immediately prior to ice-off, and the 2014 observations were 12 days prior to ice-off. This time difference allowed for significantly different ice and snow conditions, and the addition of warm inflows, which forced the circulation closer to the ice-off date. These observations add to the growing understanding of the relationship between thermal distribution and circulation under ice.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
15
Norris, Nathaniel. "The Mystery Interval: hydrological changes and circulation pattern changes?" University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin156206011280431.
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Aleksa, Matthew D. "The effects of teleconnection patterns on lake-effect snowfall in the Lake Erie snowbelt, 1951-2007". Virtual Press, 2008. http://liblink.bsu.edu/uhtbin/catkey/1391471.
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The relationships between teleconnection patterns the Pacific/North American (PNA) index, North Atlantic Oscillation (NAO) and the El Nino/Southern Oscillation (ENSO)—and lake-effect snowfall are examined. Bivariate and partial correlations are used over seasonal and semi-seasonal periods for stations within the Lake Erie snowbelt to link teleconnection phases to snowfall increases. Significant negative correlations were seen throughout the entire winter between NAO and snowfall. Relationships between PNA and ENSO on snowfall were less evident, with significant correlations during the mid-winter months between a positive PNA and snowfall and significant correlations during the late winter in the western zone between a negative ENSO and snowfall.Department of Geography
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Kuan, Chihfeng. "Quantitative Skill Assessment of the Princeton Coastal Ocean Circulation Model for Lake Erie /". The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu148793030468528.
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Andradóttir, Hrund ÓlÅ f. 1972. "Circulation and mixing in the upper forebay of the Mystic Lake system, Winchester, Masshachusetts". Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10361.
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Ihuel, Ewen. "De la circulation des lames à la circulation des poignards : mutation des productions lithiques spécialisées dans l’Ouest de la France du Ve au IIIe millénaire". Paris 10, 2009. http://www.theses.fr/2008PA100203.
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Une diversité de production laminaire circule dans l'Ouest de la France, entre le milieu du Ve et la fin du IIIe millénaire. A partir des modalités de production jusqu'à celles de leur utilisation, ce travail s'intéresse à l'évolution des productions spécialisées et à leurs motivations. Au Néolithique moyen, les dolmens à couloirs livrent des grandes lames brutes, interprétés comme des objets socialement valorisés, fruit de productions spécialisées. Au début du Néolithique récent, de telles productions n'existent plus. Il faut attendre les derniers siècles du IIIe millénaire pour observer à hauteur de la Loire, des petites lames conçues pour l'échange à l'échelle régionale. Ce sont sur ces supports que s'observent les lames appointées entre 3100 et 3000 av. J. -C. Deux phases de productions de poignards s'observent en Touraine. La phase ancienne est située entre 3050 et de 2850 av. J. -C. Les poignards sont réalisés sur des lames larges et courtes (jusqu'à 20-22 cm) produites à partir de nucléus NaCAL et ils sont retouchés par pression. La circulation de ces pièces prend une ampleur extrarégionale. Les poignards anciens sont majoritairement retrouvés en sépultures à l'état neuf. Lors de la deuxième phase, dite classique, datée entre 2850 et 2450 av. J. -C. , les poignards sont réalisés sur des lames de livres de beurre, ils mesurent alors entre 25 et 34 cm. La production s'élargie à plusieurs sous-produits (scies à encoches, éclats). La circulation s'étale de l'Allemagne du Nord, jusqu'aux Alpes et aux Pyrénées. Les poignards sont désormais majoritairement retrouvés en habitat, abandonnés en état d'exhaustion. Dans les sépultures, le matériel est rencontré dans des états variés, neufs ou très usés, entiers ou fragments. Les apprêts se développent (polissage, retouche en écharpe). La disparition des poignards de silex vers 2450 av. J. -C. Reste encore mal compriseDiverse blade productions circulated in western France from the middle of the Sth to the end of the 3rd millennia. Through the study of production and use strategies, this research explores the evolution of specialized productions and their motivations. Middle Neolithic gallery graves yield large unworked blades interpreted as socially valuable objects resulting from specialized productions. At the beginning of the Late Neolithic, these productions no longer exist. It is not until the last centuries of the 3`d millennium that we observe in the Loire region, small blades destined for exchange on a regional scale. Between 3,100 and 3,000 BC, these blades serve as blanks for pointed blades. Two dagger production phases are known in Touraine. The earliest occurs between 3,050 and 2,850 BC. The daggers are realized on avide, short blades (up te, 20-22 cm) produced from NaCAL tores and finished with pressure retouch. The circulation of these objects becomes extraregional. Môst of these early daggers are found in burials in an unused state. During the second "classic" phase, dated te, between 2,850 and 2,450 BC, daggers are realized on blades originating from "livre de beurre" tores, and measure between 25 and 34 cm. The production includes several sub-products such as notched saws and flakes. Their circulation extends from northern Germany to the Alps and Pyrenees. The majority of these daggers are found in habitat sites, abandoned in an exhausted state. In burials, they are found in varied states, new or very used, whole or fragmented. Différent preparations are developed (polishing, oblique-parallel retouch). The reasons for the disappearance of Oint daggers at around 2,450 BC remains poorly understood
20
Rabeau, Olivier. "Distribution de l'or de type orogénique le long de grands couloirs de déformation archéens : modélisation numérique sur l'exemple de la ceinture de l'Abitibi". Thesis, Vandoeuvre-les-Nancy, INPL, 2009. http://www.theses.fr/2009INPL073N/document.
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Cette thèse visait à mieux définir les méthodes de ciblage et apporter des éléments de réponse sur la genèse des gisements d’or de type orogénique en périphérie des grands couloirs de déformation archéens. Cette thèse est présentée sous forme de trois articles. Le premier article traite de la distribution mathématique des gisements aurifères de type orogénique le long des grands couloirs de déformation. Une approche permettant de d’établir que la localisation des gisements se situant le long de structure de premier ordre n’est pas indépendante de la localisation de ses voisins a été développée. Cette approche permet de donner des éléments de réponse sur la formation de ces gisements et de générer des probabilités de découvertes à l’échelle régionale. La deuxième partie de cette présente une méthode l’évaluation du potentiel minéral sous couverture sédimentaire en 3D. Les teneurs aurifères compilées dans le secteur ont permis d’évaluer et de quantifier les relations spatiales existantes entre certaines entités géologiques et les emplacements minéralisés afin de cibler les endroits à haut potentiel. Enfin, les travaux présentés dans le dernier chapitre visent à délimiter les zones possédant une perméabilité structurale accrue lors de l’épisode de déformation contemporain à la mise en place de gisements aurifères de type orogénique. Une modélisation géomécanique 3D qui tient compte des propriétés physiques des roches a été effectuée sur un segment de faille choisi en utilisant un code d’élément fini. La déformation s’effectue en attribuant sur chaque discontinuité structurale des vecteurs ou des champs de déplacement en fonction des observations de terrainThis thesis had the objective to define targeting methods adapted to orogenic gold deposits hosted in greenstone belts and to better understand the formation mechanism of these deposits. The work accomplished is presented in three distinct articles. The first article aimed to determine if a mathematical relation can characterize the spatial distribution of orogenic gold deposits along a crustal scale fault zone within or if the localization of a deposit is independent of the position of each other. A uniform law was fitted between the frequency and the curvilinear inter-distance between successive orogenic gold occurrences along the CLLF for distances ranging from 315 to 5600 m. This approach gave insights on the formation mechanism and allowed the generation of a probability map for undiscovered deposits at a regional scale. The second chapter of this thesis focuses on a sector of the Cadillac Larder Lake Fault that was considered as having a high potential for discovery using the methodology presented in the last chapter. Compiled assays allowed the evaluation of the spatial association of certain geological features with orogenic gold mineralizations to allow targeting high potential areas. Finally, the work presented in the last chapter aimed at identifying dilatant zones during the deformation that is contemporaneous to the orogenic gold deposit formation. A 3D geomechanical modelling which takes rock properties into account was performed on a chosen segment of a fault zone using a finite element code. The deformation was induced using displacement vectors or fields interpreted from field data
21
Seker-Elci, Sebnem. "Modeling of Hydrodynamic Circulation and Cohesive Sediment Transport and Prediction of Shoreline Erosion in Hartwell Lake, SC/GA". Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5081.
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This dissertation addresses hydrodynamics, sediment transport and shoreline erosion within the main pool of Hartwell Lake, a U.S. Army Corps of Engineers reservoir built on the Savannah River, between Anderson, South Carolina, and Hartwell, Georgia, USA. A U.S. Environmental Protection Agency (EPA) Superfund site is located on a tributary of Hartwell Lake because of high concentrations of polychlorinated biphenyls (PCBs) in the lake sediments. PCBs are hydrophobic and typically bond to fine-grained sediments, such as silts and clays. The primary goal of the study was to document, through field measurements, and model, using a 3-D numerical model of flow and sediment transport, the fate of sediments within the main pool of Hartwell Lake.
To document forty years of sedimentation within the reservoir, bathymetric survey data were collected in Hartwell Lake during the period, February 10-14, 2003. The bathymetric surveys revealed that deposition was, in places, up to two meters thickness in forty years. During the field campaign, flow velocity measurements were made primarily to provide a check on the magnitude of the velocities predicted by the numerical model used in the study. Shoreline surveys provided data for the modeling procedure for shoreline change. This in turn facilitated specification of the sediment flux into the domain via shoreline erosion.
Hartwell Lake is located near the southern terminus of the Appalachian mountain chain in the Piedmont region. Sediments contain high fractions of silt and clay. Hartwell Lake has a shoreline length of 1548 km, and erosion of lake shorelines has been a significant problem for many homeowners. As of September 2002, there were 1123 permitted riprap installations, and 393 permitted retaining walls, for a total of 1516 erosion control structures along the lakeshores (source: USACE Hartwell Office), an indication of the magnitude of the erosion problem.
To quantify the erosion rate of the shorelines, an approach that relates erosion rates to wind wave forces was developed. A simplified representation of the shape of beach profiles is employed. Historical shoreline change rates were quantified by comparing available digital aerial photos taken in different years, and the erosion prediction model was calibrated using these computed erosion rates.
Sediments derived from shoreline erosion were introduced to the model as an additional source along the model boundary, and the fate of the eroding sediments was investigated via numerical modeling.
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Svensson, Martin. "An Investigation of the Relation between Sea Breeze Circulation and Diurnal Variation of Methane at a Swedish Lake". Thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-253626.
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Methane measurements over lake Tämnaren show a pronounced diurnal variation with high values at night and low values during daytime. The atmosphere over the lake and its surroundings is simulated with two different settings and resolutions of the WRF model during a period of eight days in May 2011 to investigate if a lake/land breeze circulation could be the cause of the observed methane variation. A night time land breeze can give rise to convergence over Tämnaren of the natural methane emissions from the lake which possibly could explain the diurnal variation. Analysis show that although Tämnaren is large enough to initiate a fully closed circulation these events are likely going to be rare because of the strong dependence of the background wind speed and cannot therefore be the cause of the pronounced diurnal variation. A fairly moderate wind speed will dominate over the thermodynamical forcing necessary to create a lake breeze. Even so, it is possible that a closed or nearly closed circulation could enhance the diurnal pattern with an increase of methane concentration at night and a decrease during the day. The reason for the high night time methane concentration is more likely due to the accumulation in a shallow internal boundary layer that develops over the lake combined with high night time methane flux caused by waterside convection.Mätningar av metankoncentrationen över Tämnaren visar en tydlig dygnsvariation med höga värden på natten och låga under dagtid. Atmosfären över sjön med omgivning modelleras med två olika inställningar och upplösningar av WRF modellen under en åttadagarsperiod i Maj 2011 för att undersöka om en sjö- och landbriscirkulation kan vara orsaken till den observerade metanvariationen. På natten kan en landbris ge upphov till konvergens över Tämnaren av de naturliga metanutsläppen vilket skulle kunna vara en möjlig förklaring till dygnsvariationen. Vidare analys visar att Tämnaren är tillräckligt stor för att initiera en sluten cirkulation men dessa händelser är troligtvis sällsynta på grund av det starka inflytandet av bakgrundsvinden och kan därför inte vara orsaken till den uttalade metanvariationen. En relativt måttlig vind kommer dominera över den termodynamiska effekt som är drivande för skapandet av sjö- och landbris. Trots detta är det möjligt att en sluten eller nästan sluten cirkulation kan förstärka metanhaltens dygnsvariation med en ökning på natten och minskning under dagen. Orsaken till den observerade höga metankoncentrationen på natten är troligare en ackumulering i ett grunt internt ytskikt som bildas över Tämnaren kombinerat med höga nattliga metanflöden till följd av konvektion i sjön.
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Hudson, Adam Michael. "Regional Precipitation Response to Enhanced Monsoon Circulation through the Holocene Using Closed-Basin Paleolakes on the Tibetan Plateau". Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/560803.
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The history of climatic changes in the Asian Summer Monsoon system over the Tibetan Plateau during the Holocene has been the subject of significant research due to the importance of the plateau as the headwaters for many major rivers providing water resources to the surrounding large, populous countries. In general, previous research has concluded that monsoon rainfall and summer temperatures peaked during the early Holocene (9-11 ka BP) in Tibet, coincident with peak Northern Hemisphere summer insolation. Atmospheric teleconnections with upstream Northern Hemisphere westerly circulation patterns influenced by North Atlantic sea surface temperature changes have also been noted at millennial and centennial timescales. However, recent studies have noted that the timing of peak monsoon warmth and wetness during the Holocene are not synchronous across the entirety of the Tibetan Plateau, and studies of modern precipitation indicate several distinct regions of monsoon precipitation variability at interannual scales, suggesting the monsoon response to past and future climate change may be regionally heterogeneous for the plateau. Clear assessment of this regionality within the monsoon climate region is a topic of continuing research, but it has been hindered by lack of climate records in remote areas, dating difficulties, and concerns over the comparability of interpreted climate-proxy relationships between the many different biological, hydrological, and geochemical proxies applied. The first part of this dissertation uses ¹⁴C and U-Th series geochronology, sedimentology, and GIS analysis of exposed lake shoreline sediments surrounding the numerous closed-basin lake systems of the central and western Tibetan Plateau to investigate regional heterogeneity in monsoon rainfall, and to develop a new well-dated lake level record from the Ngangla Ring Tso lake system in the poorly studied southwestern region. The major conclusions are: 1) peak early Holocene monsoon rainfall, recorded by the highest paleoshorelines surrounding 130 lake systems, intensified more relative to today in the western part (west of 86°E longitude) of the Tibetan Plateau when compared to eastern regions, closely following regions of modern rainfall variability; 2) monsoon rainfall in the Ngangla Ring Tso region peaked during the early Holocene insolation maximum, consistent with other records, remained significantly higher than modern until ~6.0 ka BP, but with abrupt reductions in monsoon rainfall associated with North Atlantic ice-rafted debris peaks. The warm and wet period of the early and middle Holocene was also likely coincident with the first major colonization of the Tibetan Plateau by prehistoric humans. Current research suggests early foragers employing stone tools first forayed into the middle elevation areas above 3,000 m elevation on the northeastern fringe of the plateau as early as 14.8 ka BP, and therefore the dominant hypothesis suggests plateau colonization proceeded from this direction, heading westward through the Holocene. However, well studied and dated archaeological sites from the high plateau are exceedingly rare, requiring further investigation. The second part of this dissertation presents new age controls for the Holocene Zhongba microlithic site in the southwestern Tibetan Plateau, using ¹⁴C dating of organic and carbonate-rich paleo-wetlands sediments hosting in situ stone artifacts. The major conclusions of this study are: 1) artifacts at the Zhongba site, which are typologically similar to microlithics across the plateau, can be no older than 6.5 ka BP, consistent with the prevailing east-to-west colonization hypothesis, and 2) microlithic tools continued to be important as late as 1.3 ka BP at the site, even though metal is found in sites of similar age elsewhere in Tibet.
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Phoon, Syin Yi. "Application of global circulation model results on hydrological conceptual models that simulate future river flows feeding Lake Victoria, East Africa". Thesis, University of Birmingham, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443641.
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Jonsson, Christina E. "Holocene climate and atmospheric circulation changes in northern Fennoscandia interpretations from lacustrine oxygen isotope records /". Doctoral thesis, Stockholm : Department of physical geography and quaternary geology, Stockholm University, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-29343.
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Diss. (sammanfattning) Stockholm : Stockholms universitet, 2009.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: In press. Paper 2: Submitted. Paper 5: In progress.
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Charraud, François. "Espaces interculturels et évolution des systèmes techniques au Néolithique dans le Nord-Ouest de la France : productions, usages et circulation des outillages en silex jurassiques de Normandie". Thesis, Nice, 2013. http://www.theses.fr/2013NICE2007/document.
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Cette thèse porte sur la Néolithisation du Nord-Ouest de la France, abordée à travers l’analyse des industries en silex jurassiques de Normandie. Objet de plusieurs influences environnementales et culturelles, cette région essentielle pour comprendre les dynamiques et les comportements socio-économiques de la Néolithisation de l’Ouest se caractérise par un environnement géologique riche en silex d’excellente qualité exploités durant toute la Préhistoire, utilisés ici comme marqueurs de ces comportements et de leur évolution sur la longue durée. L’objectif est de caractériser les productions liées à ces ressources et leur diffusion, de préciser les contextes chronoculturels dans lesquels elles évoluent, en prenant en compte tous les processus de la chaîne opératoire, depuis l’acquisition des matériaux jusqu’à l’abandon des outils. Restituer une vision cohérente de ces processus suppose un protocole qui croise les approches typo-morphologique, technologique et fonctionnelle des industries pour respecter le lien structurel qui existe entre l’économie des matières premières, la gestion des productions et de l’outillage. L’étude sur la longue durée de l’utilisation d’un type de ressources particulières offre un point de vue spécifique sur la Néolithisation de l’Ouest. Les continuités et les ruptures, la permanence ou la disparition de chaînes opératoires, procédés techniques, ou voies de distribution restituent un pan de l’évolution technique et culturelle de ces sociétés néolithiques. L’analyse critique des sites a permis de dépasser l’hétérogénéité de la documentation pour parvenir à ce butThis thesis addresses the question of the Neolithisation of the Northwest of France, throught the analysis of the industries based on Jurassic flint from the Neolithic sequence in Normandy. Subject of several environmental and cultural influences, this region is essential for understanding the dynamics and socio-economic behaviors in the Neolithisation process. Normandy is characterized by a geological environment with excellent flint sources used throughout Prehistory, used here as markers of these behaviors and their evolution over the long term. The aim is to characterize the productions related to these sources and their distribution, the chronological and cultural sequence in which they operate, taking into account all the processes of chaîne opératoire, from flints procurement to the abandonment contexts. Restore a coherent vision of the process involves a protocol that melts typo-morphological, functional and technological approaches, to meet the structural link between the economies of raw materials, production and tools management. The study on the long-term use of a particular type of resource gives a specific point of view about Neolithisation of the Northwest of France. Continuities and ruptures, permanence or extinction of chaînes opératoires, technical processes and distribution channels restore a piece of technical evolution and cultural significance of the Neolithic societies
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Martz, Pierre. "Caractéristiques, chronologie et rôles des circulations fluides dans le bassin d'Athabasca et son socle : implications dans la formation et l'évolution du gisement d'uranium de Cigar Lake". Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0221/document.
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Les principales cibles d'exploration pour les gisements d’uranium de type discordance du bassin d’Athabasca (Canada) sont les structures graphiteuses du socle. Toutes ces structures ne sont pourtant pas fertiles et elles présentent des histoires plus ou moins complexes de circulations fluides successives. Cette thèse propose de déconvoluer les caractéristiques propres à chaque évènement de circulations fluides par une étude multidisciplinaire focalisée sur l’exemple de l’environnement proche du gisement de Cigar Lake. Au cours de l’exhumation tardi-orogénique du socle, la formation de failles ductile-cassantes associées à une circulation intense de fluides à C-O-H-N a permis des enrichissements en graphite et une première évolution pétrophysique des zones endommagées. Ces structures du socle particulièrement fragilisées par la déformation cassante fini-Hudsonienne ont pu être réactivées après dépôt du bassin et devenir des lieux favorables à la convection de saumures sédimentaires. La circulation de saumures sodiques dans le socle a favorisé des interactions fluides-roches à l’origine de la solubilisation de l’uranium, d’altérations K-Mg et d’évolution de composition du fluide vers un pôle plus calcique de plus forte salinité. Enfin une méthodologie d’analyse intégrée des compositions élémentaires majeures, traces et isotopiques U-Pb-O sur oxydes d’uranium est proposée, permettant de déconvoluer les effets des évènements fluides ultérieurs sur la minéralisation primaire. Cinq évènements ont ainsi contribué aux caractéristiques actuelles du gisement de Cigar Lake : Un évènement primaire de circulation de saumures à 1290-1380 Ma, à l’origine de l’ensemble du stock d’uranium ; un événement de circulations fluides à ca. 900 Ma à l’échelle régionale qui n’est pas associé à une reprécipitation d’uranium mais a brechifié et perturbé la chimie des oxydes primaires ; deux évènements tardifs de circulations fluides à ca. 340 et 220 Ma qui ont significativement remobilisé le stock primaire d’uranium. Enfin un dernier épisode récent de circulation d’eaux météoriques est à nouveau à l’origine d’un changement de chimie des oxydes antérieurs et d’une remise à zéro des systèmes isotopiquesThe main exploration targets for unconformity-related U deposits of the Athabasca Basin are the graphite-rich structures in the basement. But these are not necessarily fertile. They show distinct features expressing specific events of fluid circulations. This study aims, through a multidisciplinary approach, at unravelling the complex history of fluid flow events recorded in the vicinity of the Cigar Lake deposit. During the basement uplift, at the end of the Trans-Hudson Orogeny, the formation of ductile-brittle shear zones associated to the circulation of C-O-H-N fluids led to hydrothermal graphite enrichments and a petrophysical evolution of damages zones. These graphite-rich shear zones that were specifically weakened by the ante-Athabasca brittle reactivation have been reactivated once more after basin deposition allowing the formation of a developed damage zone especially favorable for sedimentary brine convection. Circulations of NaCl-rich brines in the basement led to brine-rock interactions, and subsequent uptake of uranium and other metals from the basement rocks. The latter have subsequently undergone strong K-Mg alteration whereas the NaCl dominated brines evolved toward a CaCl2-dominated composition with higher salinities. Finally, this thesis sets out an integrated methodology allowing to decipher the complex superimposed geochemical signatures of distinct fluid flow events on the primary uranium oxides. Five fluid flow events contributed to the present day state of the Cigar Lake deposit: a primary event of brine circulation occurred at 1290-1380 Ma and is at the origin of the main U stock; a second basin-scale event of fluid flow occurred at ca. 900 Ma, it brecciated and strongly disturbed the deposit; two later events of fluid flow strongly remobilized the deposit at ca. 340 and 220 Ma and greatly contributed to the actual state of the deposit. Finally a last, rather recent event of fluid flow was at the origin of strong chemical changes in the uranium oxides compositions and strong isotopic resetting
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Matos, Branco Lelia Maria Lages Nunes de [Verfasser], Dierk [Akademischer Betreuer] [Gutachter] Hebbeln e Rooij David [Gutachter] Van. "Temporal distribution of cold-water corals in the northwest Atlantic through the Late Quaternary : footprint of intermediate water mass circulation / Lelia Maria Lages Nunes de Matos Branco ; Gutachter: Dierk Hebbeln, David van Rooij ; Betreuer: Dierk Hebbeln". Bremen : Staats- und Universitätsbibliothek Bremen, 2017. http://d-nb.info/1141277670/34.
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Martinsson, Erik, Emil Martinsson e Sören Säf. "IWESS, an integrated water, energy and sanitation solution : A holistic approach to reach sustainability trough organic waste management for the Lake Victoria Basin, Kenya". Thesis, University of Skövde, School of Technology and Society, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-566.
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The process of allocating necessary resources like clean water, fuel/energy and food have resulted in an unsustainable use of natural resources causing problems with Soil erosion, soil fertility, desertification, deforestation, eutrophication and global warming. The purpose of this study was to gain information on the functional design of a waste management system enabling the organic components of domestic waste to be processed as useful resources while at the same time allow them to be re-circulated. The main part of this study was carried out at the Kendu SDA Hospital in the Rachyonyo district in western Kenya. For the case of this study two main objectives where chosen. The first was to develop a principal technological solution using three classed “appropriate technologies” found suitable for the purpose namely biogas, ecological water treatment systems and slow sand filtration. The second was to further analyse each included technology to further develop their potential to fit the concept. Results from the pilot facilities where then to be retrieved from the actual component selection and construction process itself, with performance analysis left for future studies.
The main purpose of the biogas system study has been to evaluate the original ideas of overall concept, details, materials and construction methods. The 1 m3 biogas system has improved significantly during the development process and is today not far from an implementation, i.e. construction on a slightly larger scale. The biogas system developed during the project has proven to have potential for digestion of both latrine and kitchen waste. Using the two as fuel for the process does not only remove a problem – it grants several benefits.
The ecological waste water treatment system main objective was to design and construct a pilot SSF-wetland. Results show that the construction process for smaller scaled SSF systems is simple and does not require trained personnel or specialized equipment and that significant cost reduction can be made by using locally available materials.
The slow sand filtration sub system concept is called PT SCX and though still in the stage of development proved to have great potential concerning both efficiency and sustainability. The PT SCX comprises the advantages of slow sand filtration with further development of individual system solutions. It was adapted to enable both integration to the IWESS solution and stand alone installations purifying even highly turbid surface water sources to drinking water quality.
The result from the study confirms the suitability of the three included technologies, ecological waste water treatment, biogas and slow sand filtration to work in an integrated system called IWESS- Integrated Water Energy and Sanitation Solution. The combined subsystems can together with source separated sewage offer full resource recovery enabling recirculation of both nutrients and water. In addition the system can be designed as a net producer of renewable and emission free energy.
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Ksontini, Feirouz. "Modèle d'agent fondé sur les affordances : application à la simulation de trafic routier". Thesis, Valenciennes, 2013. http://www.theses.fr/2013VALE0027/document.
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Les travaux conduits dans le cadre de cette thèse ont pour but d’étendre le champ de validité des simulations de trafic en milieu urbain et péri-urbain, avec notamment une meilleure prise en compte du contexte de conduite, de l’hétérogénéité des véhicules (deux-roues motorisés, véhicule léger, poids lourd, etc.) et des comportements des conducteurs en termes d’occupation de l’espace au sol. Le but est de produire en simulation des comportements observés en situation réelle tels que les phénomènes de faufilement (deux-roues, véhicules d’urgence, cas des intersections). Nous abordons, la simulation du trafic routier en considérant une approche comportementale fondée sur les systèmes multi-agents. Des travaux précédents ont proposé des solutions non génériques, notamment pour le cas particulier des deux-roues motorisés. Nous proposons un nouveau modèle d’agent permettant de mieux prendre en compte le contexte de conduite et les comportements des conducteurs en termes d’occupation de l’espace. Nous dotons l’agent d’une représentation ego-centrée de l’environnement fondée sur le concept d’affordance. Nous utilisons ainsi les affordances pour identifier les actions possibles, en termes d’occupation de l’espace, offertes par l’environnement. Nous les utilisons en- suite pour construire une représentation ego-centrée de la situation. Le modèle d’agent proposé a été implémenté avec Archisim. Cette implémentation a permis de reproduire une situation de trafic réelle et de comparer les données simulées avec celles recueillies sur le terrain. Différentes expérimentations ont été menées afin d’évaluer la qualité de la solution proposéeThe work described in this thesis aims to improve the validity of traffic simulations in urban and suburban areas. We propose to consider the driving context, the heterogeneity of vehicles (motorized two-wheelers, vehicle, truck, etc.) and the driver behavior in terms of space occupation. The purpose is to produce in simulation the observed real world phenomena such as faufilement behavior (two-wheelers, emergency vehicles, cases of intersections). We address the traffic simulation byconsidering a behavioral approach based on multi-agent systems. Previous work have proposed non- generic solutions, for the particular case of motorized two-wheelers. We propose a new agent model to better take into account the context of driving and driver behavior in terms of space occupation. We endow agent driver with an ego-centered representation of the environment based on the concept of affordances. We use the affordances to identify the possible actions, in terms of space occupation, afforded by environment. The proposed agent model was implemented with ArchiSim. This implementation has allowed to reproduce a real traffic situation and to compare the results to real data. Different experiments were conducted to assess the quality of the proposed solution
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Oliveira, Débora Nunes de. "Circulação de crianças e adolescentes em Vargem Grande Paulista-SP". Pontifícia Universidade Católica de São Paulo, 2009. https://tede2.pucsp.br/handle/handle/18010.
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Made available in DSpace on 2016-04-29T14:17:56Z (GMT). No. of bitstreams: 1
Debora Nunes de Oliveira.pdf: 543657 bytes, checksum: bd1eee42af4aaa2b6da47ad436db4cbf (MD5)
Previous issue date: 2009-10-20Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
The present work, Circulation of children and teenagers at Vargem Grande Paulista city has as objective the identification os situations where children or adolecent leave their original families to be taken care of by other families, institutions or to live on the streets. It was described three cases of families who were living in conditions of high social vulnerability. It was not intended to identify the causes but to analize how did it happen the shift and its meaning. Children and teenagers were sheltered in wide families and foster families that had meaningful experiences for the formation of their relantionship networks and their history. The idea was to understand wich were the major grownd for the child leaving his own family and what would and wouldn t concur to his coming back. What were the motivations a person would have to shelter in his own family someboby with whom there was no blood lineage all the time? That presented to the teenagers the experience of sharing different life stiles not always safe. The bibliographic search allowed me to perceive that the foster of children and youths not belonging at one s own family core is a brazilian culture characteristic. And to foster somebody s child is a milenar practice that persist to this day, being through the legal way or not. The goal is usually to achieve the children or youth well being. The fieldwork has also shown that the person who experienced in his own childhood the foster home in his own family, at adulthood present the predisposition for shelter. One of the purposes of this work was to find the elements that may contribute to establish the Shelter Family Program at Vargem Grande Paulista country at São Paulo state
O presente trabalho, Circulação de crianças e adolescentes em Vargem Grande Paulista teve como objetivo identificar situações em que crianças ou adolescentes deixam sua família de origem para serem assistidos por outras famílias, instituições ou para viverem na rua. Foram descritos três casos de famílias que viveram em condição de alta vulnerabilidade social. O intuito não foi identificar as causas, mas sim analisar como se deu a circulação e seu significado. Foram crianças e adolescentes acolhidos em famílias extensas ou de acolhimento e que tiveram experiências significativas para constituição de suas redes de relações e de suas histórias. A idéia era procurar entender quais eram os determinantes para a saída de uma criança de sua família de origem e o que contribuiria ou não para seu retorno. Que motivações uma pessoa teria para acolher em sua família alguém com quem nem sempre tinha vinculação sanguínea? O que representou para os adolescentes, a experiência de estar compartilhando modos de vida diferentes, e nem sempre seguros. A pesquisa bibliográfica permitiu-me apreender que o cuidado de crianças e adolescentes não pertencentes ao próprio núcleo familiar é uma característica da cultura brasileira e que, cuidar do filho de outro, é uma prática milenar que perdura até os dias de hoje, seja pela via legal ou não. O que é buscado, geralmente, é o bem estar da criança ou do adolescente. A pesquisa de campo demonstrou, ainda, que a pessoa que experienciou em sua infância a vivência do acolhimento de outros em sua família, na idade adulta apresenta predisposição para a acolhida. Um dos objetivos dessa análise foi levantar elementos que contribuíssem para a implantação do programa família acolhedora no município de Vargem Grande Paulista/SP
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McInerney, David John. "A triangular grid finite-difference model for wind-induced circulation in shallow lakes". 2005. http://hdl.handle.net/2440/37943.
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In this study, the development and testing of a finite-difference model for wind-induced flow in shallow lakes, and, in particular, a new technique for improving the land--water boundary representation, are documented. The model solves nonlinear, as well as linear, versions of the two-dimensional depth-integrated shallow water equations. Finite-difference methods on rectangular grids are widely used in numerical models of environmental flows. In these models, land--water boundaries are usually approximated by a series of perpendicular line segments, which enable the impermeability condition to be easily implemented. A disadvantage of this approach is that the actual boundary is often poorly approximated, particularly in regions which have complicated coastlines, and, as a result, currents in these regions cannot be accurately predicted. A technique for improving the land--water boundary representation in finite-difference models is introduced. This technique permits the model boundary to contain diagonal line segments, in addition to the vertical and horizontal line segments used in traditional models. The new technique is based on a simple concept and can easily be included in existing finite-difference models. In order to test the new method, the linearised shallow water equations are solved numerically for oscillatory wind-driven flow in lakes with simple geometry. Predictions obtained using the new approach are compared with predictions from the traditional stepped boundary and known analytic solutions. A significant improvement in the accuracy of results is noticed when the new approach is used, particularly in currents close to shore. The increased accuracy obtained using the improved boundary representation can lead to a significant computational saving, when compared with running the rectangular grid model with smaller grid spacings. A second-order analytic solution to the nonlinear shallow water equations is developed for oscillatory wind-driven flow in a rectangular lake. Comparisons between this solution and numerical results, obtained using the traditional stepped boundary and the improved boundary, verify the finite-difference formulae used in these models, including the approximations used for the cross-advective terms close to shore. Once more, currents are predicted with greater accuracy when the new technique for representing the land--water boundary is implemented. The lake circulation model is applied to the Lower Murray Lakes, South Australia, and predicted water levels at Tauwitchere Barrage are shown to agree very well with observations. The model is then used to examine the effectiveness of two schemes that have been proposed to increase wind-induced circulation, and therefore potentially decrease salinity, in Lake Albert, demonstrating the model's use as an efficient and effective tool for analysing flow behaviour in lakes.Thesis (Ph.D.)--Mathematical Sciences (Applied Mathematics), 2005.
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Marshall, Natalie School of Biological Earth & Environmental Sciences UNSW. "Geomorphic controls on thermal stratification in the floodplain lakes of the Macdonald River, New South Wales". 2007. http://handle.unsw.edu.au/1959.4/40581.
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This thesis examines geomorphic processes that impact thermal stratification within floodplain lakes. Previously, thermal stratification was not thought prevalent in these numerous small water bodies, despite being found in small reservoirs. Thermal stratification leads to long term anoxia in the bottom waters and the release of metals and nutrients from the sediments. This can result in water quality problems such as algal blooms (including potentially toxic cyanobacteria), loss of fish habitat and deterioration of wetland habitat. Four floodplain lakes of the Macdonald River Valley NSW were profiled and tested over 3?? years to assess to what extent, under what conditions, and with what chemical and physical effects, they thermally stratified and destratified. The morphometry, bed facies, vegetation, hydrology and local weather patterns for each lake were also investigated. Physical and chemical analyses found elevated nutrients in all four lakes and higher concentrations of total phosphorous and total nitrogen in the bottom waters. These results were not dependant on stable thermal stratification and long-term anoxia in the bottom waters. Inflow samples had much higher concentrations of nutrients than the lake samples, so the catchment is the likely source. Samples were analysed for phytoplankton and significant populations of potentially toxic cyanobacteria were present. Stratification depended upon whether the lake was "sheltered" from wind stirring or from incident radiation, either topographically by steep slopes surrounding the lakes, or by submerged and emergent vegetation. Aquatic vegetation limits the amount of transfer of turbulent kinetic energy from wind shear and the amount of incident radiation received. At one lake, sheltered areas reached temperatures much higher than less sheltered areas. Topographic sheltering can make a difference of up to three degrees Celsius across the lake surface. Destratification depended on wind speed, wind direction and orientation of the lake to the dominant wind direction. An extension to the classification of fluvial lakes (from Timms 1992) is presented, with further subdivisions to describe the lakes as "sheltered" or "open" and the type of sheltering (vegetation or topography) present.
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Yadav, Badri Vishal. "Circulation and mixing in Lake Champlain". 2008. http://proquest.umi.com/pqdweb?did=1453214831&sid=10&Fmt=2&clientId=39334&RQT=309&VName=PQD.
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Thesis (M.S.)--State University of New York at Buffalo, 2008.Title from PDF title page (viewed on Sept. 02, 2008) Available through UMI ProQuest Digital Dissertations. Thesis adviser: Atkinson, Joseph F. Includes bibliographical references.
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North, Ryan P. "Implications of non-uniform wind stress on lake circulation : with application to Quesnel Lake, B.C". Thesis, 2006. http://hdl.handle.net/2429/17569.
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In hydrodynamic modeling of lakes, wind stress is often assumed uniform over an
entire water body. This is not always an accurate representation of the wind stress
since it does not consider wind distribution inhomogeneities or the effect of windwaves.
These factors modify wind stress at the air-water interface and mixing
induced in the surface waters. This thesis focuses on the influence of wind-waves on
wind stress distribution and discusses the implications for wind-driven circulation
in stratified water bodies.
Significant wave height throughout the basin is estimated using fetch and duration
limited equations. Wind stress is then calculated from wind speed and a
modified coefficient of drag. The latter is related to the significant wave height via
a surface roughness formulation. This accounts for variations in wind stress due
to wave fetch and duration. Wind stress estimated with and without the influence
of wind-waves is applied to an analytical solution for wind-driven circulation in a
simplified lake. The comparison demonstrates the significance of wind-waves on
lake circulation. Results indicate an increase in internal seiching and surface layer
currents with the inclusion of the surface roughness height.
Further testing of the influence of wind-waves is conducted on Quesnel Lake,
B.C. Comparisons using an idealized wind (uniform and steady) once again indicates
an increase in the internal circulation when accounting for surface roughness. The
importance of properly quantifying the wind speed and direction is also discussed.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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St, Amour Natalie Ann. "A Multi-Proxy Study of Holocene Atmospheric Circulation Dynamics Recorded in Lake Sediments in Fennoscandia". Thesis, 2009. http://hdl.handle.net/10012/4225.
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Cellulose-inferred lake water oxygen-isotope records were obtained from five throughflow lakes situated along a north-south transect across Fennoscandia to help develop a better picture of Holocene changes in atmospheric circulation in the region. This research addresses prior evidence for the existence of non-temperature-dependent shifts in d18O of precipitation in the early Holocene attributed to changes in atmospheric circulation. The validity of this hypothesis is tested through the development of oxygen-isotope records from lake sediments and their interpretation in the context of independent reconstructions of temperature and precipitation from pollen and chironomid head-capsules collected from the same or nearby sites, and well-documented changes in vegetation composition. Records of carbon and nitrogen elemental content and isotopic composition and magnetic susceptibility are included in this multi-proxy investigation. Extensive modern isotope hydrology datasets spanning several years at four of the five sites also help to inform interpretations of the cellulose d18O records.
Key results from this research are:
1) Elevated d18O in relation to prevailing temperature occurred during the early Holocene (c. 10,000-6000 cal. BP) for sites in northern Fennoscandia (Lake Tibetanus, Lake Spåime), in harmony with previous interpretations suggesting that strong zonal atmospheric circulation led to deepening of the precipitation and isotope shadows in the lee of the Scandes Mountains.
2) Evidence from a southern site (Arbovatten) reveals a previously unrecognized negative offset in the d18O-temperature relation during the early Holocene, apparently transferred directly from the North Atlantic without the orographic effects associated with a topographic barrier.
3) The modern d18O-temperature relation appears to have been established throughout Fennoscandia by c. 6000-4000 cal. BP, probably due to generally weaker circumpolar atmospheric circulation in response to lower summer insolation.
4) Comparison of two sites (Lake Spåime, Svartkälstjärn) in a west-east transect across central Fennoscandia reveals higher-frequency variability in atmospheric circulation at submillennial scales throughout the Holocene, which appears to be analogous to contemporary variability in the North Atlantic Oscillation (NAO) at seasonal-to-decadal time-scales. Evidence of such NAO-like variability also exists at two northern sites (Lake Keitjoru, Oikojärvi) during the Holocene, likely reflecting variations in summer and winter atmospheric circulation.
5) Complex lake-specific changes in productivity occurred in response to Holocene climate change, as revealed by carbon and nitrogen elemental and isotopic data in lake sediments. A major shift in atmospheric circulation pattern occurring at c. 4000 cal. BP probably led to a reduction in soil-derived 13C-depleted nutrients in five lakes (Lake Keitjoru, Oikojärvi, Lake Spåime, Svartkälstjärn, Arbovatten) associated with changes in terrestrial vegetation. Changes in sediment nitrogen isotope composition also occurred in these lakes at c. 4000 cal. BP, possibly reflecting changing nutrient supply dynamics because of enhanced nitrogen losses during spring snowmelt.
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Lee, Jong Wook. "Numerical modelling of temperature-induced circulation in shallow water bodies and application to Torrens Lake, South Australia". 2007. http://hdl.handle.net/2440/37895.
Texto completo da fonteResumo:
Thermal stratification occurs in shallow water bodies because solar energy separates the water column into an upper warm layer, a lower cold layer, and an intermediate layer between the upper and lower layers. In general the intermediate layer exhibits a significant thermal gradient over depth. Because cold water is heavier than warm water, this temperature structure produces a stable stratification, thereby inhibiting circulation from the bottom to the surface. This stable stratification results in a deficit of dissolved oxygen in the lower layer leading to water quality problems. Hence understanding the thermal structure and vertical circulation in shallow water bodies is important for water quality and its management. In this research, a numerical code is developed to examine the three-dimensional flow structure in shallow water bodies. This numerical code is used to solve the governing equations : the Reynolds averaged Navier-Stokes equations for three velocities and pressure, the depth-averaged continuity equation for free surface movement, the equations for turbulence closure, the scalar transport equation for temperature, and the international equation of state for density variation due to temperature. These equations are solved simultaneously using a finite difference method. The mathematical equations are transformed into a generalised coordinate system which allows flexibility for irregular boundaries and the allocation of vertical grid points every time step depending on free surface movements. In order to overcome possible numerical instabilities because of the small vertical length scale in shallow water bodies, an implicit method is used in the vertical direction. Several test cases involving free surface movement are used to verify the numerical code, and numerical solutions compare favourably against analytical solutions and measured data. The numerical code has been applied to the Torrens Lake in Adelaide, South Australia, where algal blooms occur frequently in summer due to thermal stratification. Typical thermal structures have been obtained from the model and these are compared with field data. The current code has been developed to improve upon existing commercial models which may not adequately address shallow water flows because of the high computational burden required to resolve free surface movements and consequential difficulties encountered for models with a small vertical length scale.Thesis (Ph.D.)--School of Mathematical Sciences, 2007.
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Rogers, Christopher K. "Impact of an artifical circulation device on the heat budget of an ice-covered mid-latitude lake". Thesis, 1993. http://hdl.handle.net/2429/2356.
Texto completo da fonteResumo:
Two lakes located in the Southern Interior Plateau of British Columbia were selected for a field investigation in order to assess the impact of artificial circulation on the heat budget of a small mid-latitude ice-covered lake. The heat transfer algorithm developed by Patterson & Hamblin (1988) for high latitude lakes was extended to include the impacts of snowmelt due to rain, sediment heat transfer, snow-ice formation, and day today variations in snow density, snow conductivity and albedo. Since the lakes considered are nearly isothermal in winter, the new model ignores the internal hydrodynamics of the problem. This model was tested on Harmon Lake, which was selected as a control for the study. The model was further modified to include the effects of artificial circulation at nearby Menzies Lake. These effects include polynya development, and a substantial reduction in average temperature. Heat losses due to free convective evaporation and direct snowfall on open water were added to the set of standard aerodynamic formulae used to determine the net meteorological heat flux across a water surface. Turbulent heat transfer from the circulated water to the ice cover was estimated based on an empirical surface velocity relationship derived from field measurements. The size of the polynya is estimated by means of a simple heat balance which also involves the surface velocity function.
The Harmon Lake predictions agree well with the field data. All discrepancies could be accounted for by parameter uncertainties and expected observation error. It was found that sediment heat transfer may be important in early winter in preventing a net loss of heat from the lake water. Significant heat gains in the latter part of winter, however, are attributed to the penetration of solar radiation. Once calibrated, the Menzies Lake predictions are also good. It was found that, over the period in which lake temperature dropped, the average heat loss due to turbulent heat transfer between water and ice was three times that across the polynya surface. The former heat flux continued to increase as the lake warmed up again, while the latter fell, on average, over a short period until increased solar heating resulted in a reversal in the direction of heat transfer across the polynya. Discrepancies between early winter ice thickness predictions and observations, could not be accounted for. It is suspected, however, that these discrepancies are a result of the impact which the heat flux across the polynya may have on the heat flux through the ice and snow cover. In this thesis, it is assumed that these two fluxes are independent of one another.
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Gonyo, Andrew William. "An 800-year multiple-proxy record of atmospheric circulation, climate change, and aquatic productivity from Kepler Lake, South-Central Alaska". 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1463971.
Texto completo da fonte
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McCullough, Gregory Keith. "Circulation of terrestrial runoff and its suspended load in a large tropical lake : a study of processes and effects near the mouth of the Linthipe River in Lake Malawi". 2006. http://hdl.handle.net/1993/20912.
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