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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Varying flux controls on timescales of autogenic storage and release processes in fluvio-deltaic environments : tank experiments

Powell, Erica Janette 15 July 2011 (has links)
Changes in external forcing having traditionally been the main area of interest in trying to understand paleo-depositional environments in sedimentary systems; however, autogenic variability has been rising in importance, while autogenic behavior has been thought of as a “noise” generator. Recently, autogenic variability has been rising in attention because decoupling allogenic signatures (externally driven) from the stratigraphic record requires robust understanding of autogenic variations (internally generated). This study aims to quantitatively measure autogenic processes under a range of flux conditions and to show that autogenic processes generate distinct signatures rather than random noise. We present data from a matrix of nine different tank experiments in order to systematically evaluate the effects of sediment flux and water discharge variations on the autogenic timescale of fluvial sediment storage and release processes and the implications of this data to the stratigraphic record. The sediment flux tow ater discharge ratio and the absolute values of these two discharges control the autogenic timescale. Variations in sediment supply yield two competing effects on the autogenic timescale. The primary sediment flux control causes a reduction in the autogenic timescale as an increase in sediment supply yields an increased rate of filling the “fluvial envelope” (the space between the maximum and minimum fluvial slopes obtained during storage and release events). In contrast, the secondary sediment flux control increases the size of the fluvial envelope and works against the primary sediment flux control. Increasing the water discharge increases the autogenic timescale by widening the fluvial envelope during the organization of the fluvial system and more importantly, diminishes the functionality of the secondary sediment control. A competition exists between these factors, causing a non-linear range of autogenic timescales for a given sediment flux to water discharge ratio. In the nine experiments here, as the ratio decreases, the secondary effects of variations in sediment supply are suppressed by the relatively high water discharge, and the timescale is more predictable using the primary sediment control. As the ratio increases, the secondary effects from sediment supply are enhanced by a poorly organized fluvial system, and the timescale converges to a narrow range. This suggests significant implications for autogenic sediment delivery and stratigraphic development in a wide range of discharge conditions in field cases. / text
2

Land Use Impact Assessment on the Nutrient Transport in the lake Mälaren.

Mir Rigau, Xavier January 2015 (has links)
Stockholm and its surroundings are facing strong urban changes and it is forecasted that the increase of population will be the principal driver for the urban regions surrounding the lake Mälaren in the next decades. A thorough regional and urban planning is needed in order to build a sustainable society and protect the environment. In this sense Coupled Human and Natural Systems (CHANS) are useful tools for the creation of future scenarios of how urbanization and landuse changes will impact the ecosystems and the water resources. This master thesis is focused on how population growth and landuse changes impact both the surface water discharges and the nutrient transport in the Norrström Drainage Basin. In this regard the different comprehensive plans of 26 municipalities in the Stockholm-Mälardalen region were studied in order to create a landuse evolution model until 2040. The impacts of the changes of urbanization on the surface waters and the nutrient transport were obtained using the PCRaster environmental modelling tool following the guidelines of the PolFlow model. The results show an increase of the built-up urban areas of a 25% by 2040. Regarding the increase of flow in the surface waters, the results show a very small increase in the flow, due to the large scale of the study area. Finally the results for the nutrient transport show an increase of the nutrient loads at the outlet of the lake Mälaren of 20% in the case of nitrogen and 15% for phosphorus. / Stockholm regionen står inför kraftiga urbana förändringar och det förutses att befolkningsökningen kommer att bli den främsta drivkraften för storstadsregionerna kring Mälaren under de kommande årtiondena. En grundlig regional- och stadsplanering behövs för att bygga ett hållbart samhälle och skydda miljön. I detta sammanhang är Coupled Human and Natural Systems (CHANS) användbara verktyg för att skapa framtidsscenarier för hur urbanisering och markanvändningar kommer att påverka ekosystem och vattenresurser. CHANS verktyg möjliggör analys av komplexa mönster och processer som inte framgår tydligt vid separata sociala och naturvetenskapliga studier. Inom CHANS ramverk fokuserar detta examensarbete på hur befolkningstillväxt och markanvändning och de ändringear de medför påverkar ytvattenutsläpp samt näringstransport i Norrström avrinningsområden. I detta avseende studerades olika översiktsplaner av 26 kommuner i Stockholm-Mälardalen regionen för att bygga en markanvändning evolutionmodell fram till 2040. Det studerade scenariot utvärderade konsekvenser av förändringarna i urbaniseringen som beskrivs i de omfattande översiktplanerna på ytvatten och näringsämne transport. Verktyget som användes för att utföra detta examensarbete var PCRaster. Det är ett miljömodelleringsverktyg som tillåter behandling av stora distribuerade data och kan skapa spatiotemporala miljömodeller. I detta avseende fördelades modellen i tre delar. Först erhölls den temporala markanvändningsevolutionen efter uppgifter från kommunala översiktplaner. Därefter beräknades ytvattenutsläppen med CN-metoden. Slutligen byggdes den näringstransportmodellen med hjälp av riktlinjerna från PolFlow modellen och näringsbelastningen från HELCOM och TRK-projektet. Resultaten visar en ökning av de bebyggda stadsområdena från 3,3 % bebyggda under år 2005 till 4,2 % år 2040 för hela Norrström avrinningsområde, som innebär en ökning med 25 % av de bebyggda områdena. Beträffande flödet i ytvattnet visar resultaten en jätteliten ökning av flödet på grund av att det studerade området har en stor skala. Slutligen visar resultaten för näringsämnenstransport en ökning av näringsbelastningen vid utloppet av sjön Mälaren med 20 % kväve och 15 % fosfor.
3

A finite element model of submarine ground water discharge to tidal estuarine waters

Robinson, Michael A. 06 June 2008 (has links)
In the research presented here, a new ground water model, FEMCoast, was developed to simulate ground water discharge to the intertidal zone of estuarine systems. This research may be the first attempt to model the ground water discharge process in a tidal estaurine system. The development of FEM Coast was undertaken as no existing ground model was capable of directly simulating the dynamic boundary conditions along the sediment water interface of the intertidal zone. Reproducing the dynamic tidal boundary conditions along the sediment water interface was determined to be essential to replicating the complex salinity gradients observed in the ground water within the intertidal zone. Field data and model results confirmed the presence of a region of ground water where an inverted salinity gradient existed. In this region the concentration of salinity decreased with depth from the ground surface. FEMCoast was also able to reproduce field data on the movement of the near shore water table and ground water discharge rates and patterns. However, the model was not able to replicate the short-term fluctuation in the concentration of salinity within the aquifer due to changes in the concentration of salinity within Cherrystone Inlet. It is believed that the inability to account for the wave action of the tides within the intertidal zone is responsible for this difficulty. The use of FEMCoast integrated with field studies provided a new method to investigate ground water discharge to tidal estuarine systems. / Ph. D.
4

Mälarens vattennivå i ett framtida klimat / Water levels in Lake Mälaren in future climate scenarios

Larsson, Karin January 2005 (has links)
<p>The discharge from Lake Mälaren is regulated to keep the lake water level within limits set by a water decree. Despite this, in the year 2000 the lake water level rose above the upper limit. Studies conducted at the climate modeling unit Rossby Centre at the Swedish Meteorological and Hydrological Institute (SMHI) indicate that the inflow to the lake may increase in the future. A flood in the area will, among other things, strike infrastructure and residential districts.</p><p>The aim of this study was to investigate the water levels of Lake Mälaren in future climates. In addition to this possible future expansion of the lake discharge though the sluice gates in order to keep water levels below limits set by the water decree and to prevent flooding of the shoreline were discussed. This was done by examining past lake and sea water level data and by using a discharge model to simulate future lake water levels resulting from high future inflow. The study was commissioned by SMHI.</p><p>High lake water levels were reproduced fairly well by the discharge model, whereas it was more difficult to draw any coclusions concerning low lake water levels. The examination of data on past lake water levels demonstrated that the regulation of the lake discharge caused a reduction of the highest lake water levels, but above all an increase of low lake water levels. Data on past sea levels in the Baltic Sea showed high values during wintertime. In combination with future high inflow to Lake Mälaren during this season, this indicates that the greatest future flood risk may prevail during wintertime. The conclusion from the simulated future lake water levels was that the lake discharge needs to be expanded to prevent flood in the area. In all scenarios examined in this study, the lake water level will not rise above the upper limit set by the water decree if the discharge is increased to 1 370 m3/s, which almost corresponds to a doubling of the existing discharge of 710 m3/s.</p> / <p>Mälarens utlopp är reglerat för att kunna hålla vattenståndet inom acceptabla gränser. Trots regleringen översteg vattenståndet under vintern 2000/01 den högsta föreskrivna nivån i regleringsbestämmelserna. Studier som bedrivs på klimatforskningsavdelningen Rossby Centre på SMHI pekar på att det framtida inflödet till Mälaren kan komma att bli högre än vad det är idag, något som skulle innebära ännu högre vattennivåer i Mälaren.</p><p>En omfattande översvämning av Mälarens stränder går bland annat ut över infrastruktur och bostäder. Problemet idag är att avbördningen genom sjöns utskov är för liten för att förhindra att översvämning uppstår. Att försöka skydda Stockholm mot vattnet med hjälp av skyddsmurar och invallning skulle bli alltför kostsamt. Ett bättre alternativ är istället att öka avtappningskapaciteten genom slussarna.</p><p>Syftet med det här arbetet var att undersöka hur vattennivån i Mälaren kan komma att bli i ett framtida förändrat klimat. I samband med detta gavs ett underlag för diskussioner om kommande utbyggnader av Mälarens utlopp för att kunna hålla vattennivån under vattendomens högsta föreskrivna nivå även vid ett högre framtida inflöde. Detta uppnåddes genom att genomföra analyser med historiska vattenståndsdata och genom att använda en beräkningsmodell för avtappning, Mälarmodellen, för simulering av ett antal framtida inflödessituationer. Arbetet har genomförts på uppdrag av SMHI.</p><p>Avtappningsmodellen återskapade de höga vattenstånden förhållandevis väl, medan det var svårare att bedöma hur precist den beräknade de allra lägsta vattennivåerna. Ett viktigt resultat från analysen med historiska data var att införandet av regleringen av Mälarens utlopp bidrog till att sänka de höga vattenstånden, men framförallt till att höja de låga. Ett annat resultat från studierna av historiska data var att vattenståndet i Östersjön antar högst nivåer under vintern. Detta i kombination med ett framtida högre inflöde till Mälaren under denna årstid indikerar att störst risk för översvämning kan komma att föreligga under vintern. För att säkert kunna hålla Mälarens vattennivå inom acceptabla gränser måste sjöns utlopp byggas ut. I alla scenarier som har undersökts i det här arbetet kan vattennivån hållas under den högsta föreskrivna nivån om avbördningen utökas till 1 370 m3/s. Det krävs alltså nästan en fördubbling av dagens avbördningskapacitet på 710 m3/s.</p>
5

Características da hidrografia, circulação e transporte de sal: Barra de Cananéia, Sul do Mar de Cananéia e Baía do Trapandé / Characteristics of hydrography, circulation and salt transport:Cananéia Bar, south of Cananéia Sea and Trapandé Bay.

Bérgamo, Alessandro Luvizon 06 October 2000 (has links)
Este trabalho tem como objetivos estudar a variabilidade das propriedades hidrográficas e da circulação durante ciclos completos de maré, classificar o sistema estuarino com o diagrama estratificação-circulação de Hansen & Rattray, calcular o transporte resultante de sal e a contribuição relativa dos termos advectivos, de difusão turbulenta e a parcela dispersiva, e estudar a influência das alterações ocorridas na descarga fluvial. Medidas de temperatura, salinidade e correntes foram realizadas no verão, outono, inverno e primavera, durante marés de sizígia e quadratura. Os perfis hidrográficos foram executados em intervalos horários durante ciclos completos de maré (13 horas), em três estações fixas (Barra de Cananéia, Baía do Trapandé e sul do Mar de Cananéia). A descarga fluvial média foi estimada através de dados climatológicos históricos da região. Os resultados sugerem mudanças no comportamento hidrodinâmico do sistema após a abertura do canal Valo Grande, com intensificação das correntes e aumento na estratificação vertical da salinidade. O aporte fluvial foi mais intenso (uma ordem de grandeza) que o obtido antes do rompimento da barragem do Valo Grande. As defasagens encontradas entre oscilações e correntes de maré, nas três estações fixas, indicam que a onda de maré se propaga pelo sistema como onda mista. A estação da Barra de Cananéia apresentou os maiores valores médios de salinidade e correntes mais intensas, sendo o oposto para a Baía do Trapandé, sugerindo que as trocas entre as águas oriundas da drenagem continental e da região costeira adjacente são mais efetivas pelo canal do Mar de Cananéia. O transporte de sal foi dominado principalmente pela parcela gerada pela descarga fluvial, seguida (com uma ordem de grandeza menor) pelas parcelas geradas pelo deslocamento da onda de maré (marés de sizígia) ou pela circulação gravitacional (marés de quadratura). As demais parcelas apresentam valores máximos inferiores a duas ordens de grandeza em relação à parcela dominante. A classificação do sistema estuarino-lagunar apresentou variações nas escalas de tempo quinzenal e sazonal, sendo sistema classificado como Tipo 2b no verão e Tipo 2a no inverno, ambos em maré de sizígia. No outono e primavera, o sistema foi classificado como Tipo 2b em marés de sizígia e Tipo 2a em marés de quadratura. / The aim of this work is to examine variations of physical water properties and estuarine circulation during complete tide cycle, to classify the estuary through Hansen and Rattray stratification-circulation diagram, to calculate salt transport and relative contribution of advection process, turbulent diffusion and dispersion, and to study the influences of alterations in fresh water discharge. Temperature, salinity and currents sampling were made in summer, autumn, winter and spring during neap and spring tides. Hydrographic profile measurements were accomplished in three fixed stations (Cananéia Bar, Trapandé Bay and south of Cananéia Sea) in hourly intervals, during a complete tidal cycle (13 hours). The medium fresh water discharge was evaluated through semi-empiric equations based on data climatological reports. The obtained results may suggest hydrodynamic system changes after the opening of the Valo Grande channel with currents intensification and increase in the salinity vertical stratification. The fresh water discharge estimative showed an increase in one order of greatness, if compared to obtained data found in recent works done when Valo Grande channel was closed. The differences found in the oscillation and tide current, in the three studied stations, indicated that the tide wave spreads in the system as a mixed wave. The station of Cananéia Bar presented the largest medium values of salinity and the most intense currents, being the opposite for the Bay of Trapandé, suggesting that the changes among the waters originating from continental drainage and adjacent coastal area are more effective for the Cananéia Sea. The transport of salt was dominated mainly by river discharge, with approximately an order of smaller greatness, followed by portions generated by tide wave displacement (in spring tides) or for the portion generated by the circulation gravitacional (in neap tides). The other portions presented inferior maximum values in two orders of greatness in relation to the dominant portion. The classification of the estuary-lagoon system showed variations in the scales of biweekly and seasonal time, being three fixed stations classified as Type 2b estuary in the summer and Type 2a estuary in the winter. In autumn and spring, during spring tides, the system changes to a Type 2b estuary, and during neap tides to a Type 2a estuary.
6

Características da hidrografia, circulação e transporte de sal: Barra de Cananéia, Sul do Mar de Cananéia e Baía do Trapandé / Characteristics of hydrography, circulation and salt transport:Cananéia Bar, south of Cananéia Sea and Trapandé Bay.

Alessandro Luvizon Bérgamo 06 October 2000 (has links)
Este trabalho tem como objetivos estudar a variabilidade das propriedades hidrográficas e da circulação durante ciclos completos de maré, classificar o sistema estuarino com o diagrama estratificação-circulação de Hansen & Rattray, calcular o transporte resultante de sal e a contribuição relativa dos termos advectivos, de difusão turbulenta e a parcela dispersiva, e estudar a influência das alterações ocorridas na descarga fluvial. Medidas de temperatura, salinidade e correntes foram realizadas no verão, outono, inverno e primavera, durante marés de sizígia e quadratura. Os perfis hidrográficos foram executados em intervalos horários durante ciclos completos de maré (13 horas), em três estações fixas (Barra de Cananéia, Baía do Trapandé e sul do Mar de Cananéia). A descarga fluvial média foi estimada através de dados climatológicos históricos da região. Os resultados sugerem mudanças no comportamento hidrodinâmico do sistema após a abertura do canal Valo Grande, com intensificação das correntes e aumento na estratificação vertical da salinidade. O aporte fluvial foi mais intenso (uma ordem de grandeza) que o obtido antes do rompimento da barragem do Valo Grande. As defasagens encontradas entre oscilações e correntes de maré, nas três estações fixas, indicam que a onda de maré se propaga pelo sistema como onda mista. A estação da Barra de Cananéia apresentou os maiores valores médios de salinidade e correntes mais intensas, sendo o oposto para a Baía do Trapandé, sugerindo que as trocas entre as águas oriundas da drenagem continental e da região costeira adjacente são mais efetivas pelo canal do Mar de Cananéia. O transporte de sal foi dominado principalmente pela parcela gerada pela descarga fluvial, seguida (com uma ordem de grandeza menor) pelas parcelas geradas pelo deslocamento da onda de maré (marés de sizígia) ou pela circulação gravitacional (marés de quadratura). As demais parcelas apresentam valores máximos inferiores a duas ordens de grandeza em relação à parcela dominante. A classificação do sistema estuarino-lagunar apresentou variações nas escalas de tempo quinzenal e sazonal, sendo sistema classificado como Tipo 2b no verão e Tipo 2a no inverno, ambos em maré de sizígia. No outono e primavera, o sistema foi classificado como Tipo 2b em marés de sizígia e Tipo 2a em marés de quadratura. / The aim of this work is to examine variations of physical water properties and estuarine circulation during complete tide cycle, to classify the estuary through Hansen and Rattray stratification-circulation diagram, to calculate salt transport and relative contribution of advection process, turbulent diffusion and dispersion, and to study the influences of alterations in fresh water discharge. Temperature, salinity and currents sampling were made in summer, autumn, winter and spring during neap and spring tides. Hydrographic profile measurements were accomplished in three fixed stations (Cananéia Bar, Trapandé Bay and south of Cananéia Sea) in hourly intervals, during a complete tidal cycle (13 hours). The medium fresh water discharge was evaluated through semi-empiric equations based on data climatological reports. The obtained results may suggest hydrodynamic system changes after the opening of the Valo Grande channel with currents intensification and increase in the salinity vertical stratification. The fresh water discharge estimative showed an increase in one order of greatness, if compared to obtained data found in recent works done when Valo Grande channel was closed. The differences found in the oscillation and tide current, in the three studied stations, indicated that the tide wave spreads in the system as a mixed wave. The station of Cananéia Bar presented the largest medium values of salinity and the most intense currents, being the opposite for the Bay of Trapandé, suggesting that the changes among the waters originating from continental drainage and adjacent coastal area are more effective for the Cananéia Sea. The transport of salt was dominated mainly by river discharge, with approximately an order of smaller greatness, followed by portions generated by tide wave displacement (in spring tides) or for the portion generated by the circulation gravitacional (in neap tides). The other portions presented inferior maximum values in two orders of greatness in relation to the dominant portion. The classification of the estuary-lagoon system showed variations in the scales of biweekly and seasonal time, being three fixed stations classified as Type 2b estuary in the summer and Type 2a estuary in the winter. In autumn and spring, during spring tides, the system changes to a Type 2b estuary, and during neap tides to a Type 2a estuary.
7

Mälarens vattennivå i ett framtida klimat / Water levels in Lake Mälaren in future climate scenarios

Larsson, Karin January 2005 (has links)
The discharge from Lake Mälaren is regulated to keep the lake water level within limits set by a water decree. Despite this, in the year 2000 the lake water level rose above the upper limit. Studies conducted at the climate modeling unit Rossby Centre at the Swedish Meteorological and Hydrological Institute (SMHI) indicate that the inflow to the lake may increase in the future. A flood in the area will, among other things, strike infrastructure and residential districts. The aim of this study was to investigate the water levels of Lake Mälaren in future climates. In addition to this possible future expansion of the lake discharge though the sluice gates in order to keep water levels below limits set by the water decree and to prevent flooding of the shoreline were discussed. This was done by examining past lake and sea water level data and by using a discharge model to simulate future lake water levels resulting from high future inflow. The study was commissioned by SMHI. High lake water levels were reproduced fairly well by the discharge model, whereas it was more difficult to draw any coclusions concerning low lake water levels. The examination of data on past lake water levels demonstrated that the regulation of the lake discharge caused a reduction of the highest lake water levels, but above all an increase of low lake water levels. Data on past sea levels in the Baltic Sea showed high values during wintertime. In combination with future high inflow to Lake Mälaren during this season, this indicates that the greatest future flood risk may prevail during wintertime. The conclusion from the simulated future lake water levels was that the lake discharge needs to be expanded to prevent flood in the area. In all scenarios examined in this study, the lake water level will not rise above the upper limit set by the water decree if the discharge is increased to 1 370 m3/s, which almost corresponds to a doubling of the existing discharge of 710 m3/s. / Mälarens utlopp är reglerat för att kunna hålla vattenståndet inom acceptabla gränser. Trots regleringen översteg vattenståndet under vintern 2000/01 den högsta föreskrivna nivån i regleringsbestämmelserna. Studier som bedrivs på klimatforskningsavdelningen Rossby Centre på SMHI pekar på att det framtida inflödet till Mälaren kan komma att bli högre än vad det är idag, något som skulle innebära ännu högre vattennivåer i Mälaren. En omfattande översvämning av Mälarens stränder går bland annat ut över infrastruktur och bostäder. Problemet idag är att avbördningen genom sjöns utskov är för liten för att förhindra att översvämning uppstår. Att försöka skydda Stockholm mot vattnet med hjälp av skyddsmurar och invallning skulle bli alltför kostsamt. Ett bättre alternativ är istället att öka avtappningskapaciteten genom slussarna. Syftet med det här arbetet var att undersöka hur vattennivån i Mälaren kan komma att bli i ett framtida förändrat klimat. I samband med detta gavs ett underlag för diskussioner om kommande utbyggnader av Mälarens utlopp för att kunna hålla vattennivån under vattendomens högsta föreskrivna nivå även vid ett högre framtida inflöde. Detta uppnåddes genom att genomföra analyser med historiska vattenståndsdata och genom att använda en beräkningsmodell för avtappning, Mälarmodellen, för simulering av ett antal framtida inflödessituationer. Arbetet har genomförts på uppdrag av SMHI. Avtappningsmodellen återskapade de höga vattenstånden förhållandevis väl, medan det var svårare att bedöma hur precist den beräknade de allra lägsta vattennivåerna. Ett viktigt resultat från analysen med historiska data var att införandet av regleringen av Mälarens utlopp bidrog till att sänka de höga vattenstånden, men framförallt till att höja de låga. Ett annat resultat från studierna av historiska data var att vattenståndet i Östersjön antar högst nivåer under vintern. Detta i kombination med ett framtida högre inflöde till Mälaren under denna årstid indikerar att störst risk för översvämning kan komma att föreligga under vintern. För att säkert kunna hålla Mälarens vattennivå inom acceptabla gränser måste sjöns utlopp byggas ut. I alla scenarier som har undersökts i det här arbetet kan vattennivån hållas under den högsta föreskrivna nivån om avbördningen utökas till 1 370 m3/s. Det krävs alltså nästan en fördubbling av dagens avbördningskapacitet på 710 m3/s.
8

Zdravotně technické instalace ve studentských kolejích / Sanitation installation in student dormitories

Kucharik, Miroslav January 2015 (has links)
Diploma thesis describes the design of plumbing systems in student dormitories. The theoretical part discusses the types of waste water, focusing on gray water and its subsequent use. The experimental part is focused on measurement drinking water consumption and drinking water discharge in existing buildings student dormitories and apartment building. The work also contains other variants of possible installation solutions. The project is part of the selected solutions developed a variant form of project documentation for construction.

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