The Region of Waterloo relies mainly (75 %) on local groundwater resources for its drinking water supply. The water demand is increasing with the growth of the population and there is a need to enhance the present water supplies. The Regional Municipality of Waterloo (RMOW), which is the governing body in charge of providing the drinking water supply, is conducting an extensive program to protect the groundwater resources of the Waterloo Moraine aquifer. The focus of that work is defining the wellhead protection areas of the existing production wells as well as the investigation of potential further water supply. The main goal of the work presented here is to delineate the capture zones for the major well fields of the Region. To achieve that goal, the flow for the expected pumping conditions is simulated using a fully 3D finite element model (WATFLOW) which has been proven to be highly flexible to represent the natural boundaries and the highly irregular stratigraphy by previous researchers and scholars. The modified version of this model which includes a pseudo-unsaturated module is used for the solution of flow equation. For the delineation of capture zones, a new particle tracking code (WATRAC) as well as two advective-dispersive transport models are used by using a probabilistic approach presented by Neupauer and Wilson [1999]. For the probabilistic approach (Wilson's method), two transport models, a conventional time-marching code (WTC) and a time-continuous code (LTG) are usedand their results are compared. The LTG is computationally more efficient than the WTC, but it gives oscillatory results close to the steady state condition. A combined used of LTG and WTC istherefore recommended to obtain the steady state capture zones. The 0. 25 probability contour agrees very well with the particle tracks, except for somewhat greater transverse spreading due tothe dispersion which is not considered by the particle tracking algorithm. Both methods, backward particle tracking and probabilistic advective-dispersive modelling are clearly more informative and give better insight when considered together than each by itself.

No description available.

No description available.

This PhD thesis investigates the transport and distribution of short-lived halogenated organic substances in the tropical tropopause layer (TTL) in the Pacific Ocean. Short-lived halocarbons are one of the major groups of the ozone depleting substances as they provide a source for the active halogens which decrease ozone in the atmosphere. The TTL serves as the primary gateway of tropospheric air to enter the stratosphere. The air which enters the stratosphere is distributed all over the globe. Thus, the research on which tropospheric air masses go into the TTL, its structure and composition and the transport within is crucial. This thesis uses the UK Meteorological Office Lagrangian particle dispersion model NAME to (i) support the flight planning activities and achieve the multi aircraft coordination in CAST, CONTRAST, ATTREX 2014 campaigns, and (ii) quantify the amount and distribution of short-lived halocarbons in the TTL, and explain differences in these vertical distributions and transport characteristics. The halocarbons of interest are methyl iodide (CH3I), bromoform (CHBr3) and dibromomethane (CH2Br2). A new NAME procedure was developed and operated successfully to provide routine simulations and near real-time products suitable for guiding the CAST, CONTRAST and ATTREX aircraft in order to achieve their mission scientific objectives, and to make coordinated measurements. NAME was used post-campaign to analyse distribution of short-lived halocarbons in the TTL, identify their source regions and transport timescales. A new approach is proposed to investigate the TTL composition in terms of the boundary layer air influence, and subsequently quantify CH3I, CHBr3 and CH2Br2 by estimating their boundary layer and background contribution. The sums of these modelled estimates are in good agreement with the ATTREX 2014 and 2013 CH3I, CHBr3 and CH2Br2 observations. The quantification of the contribution of short-lived bromocarbons to the active bromine in the TTL was achieved, and the results lie within the range of the recent literature studies. The final focus of this thesis is on how well NAME represents the particle displacement via convection. Convection is the major transport pathway for the short-lived halocarbons to reach the TTL. The role of convection in transporting CH3I, CHBr3 and CH2Br2 to the TTL is assessed using the new convection scheme in NAME. A validation of the performance of this scheme is provided, showing that it yields improved and more realistic representation of the particle displacement via convection.

The need for more inclusive and integrated cities has resulted in a paradigm shift in the South African transport and land use policy environment where transport and land use planning are viewed as a continuum as opposed to isolated planning aspects. Issues such as residential segregation, social exclusion, spatial inefficiencies, inequality, residential informality, marginalisation of the low-income cohort continue to form part of the current planning discourse. While policy acknowledges the need to redress these issues, the urban spatial patterns in South African cities continue to trace the historical planning trajectory. Recently, congestion has become an issue in some of South Africa’s cities with Johannesburg and Cape Town appearing in the list of the top hundred most congested cities in the world. It is thus essential to understand how South African cities can address urban accessibility and mobility issues along with redressing apartheid spatial planning to attain sustainable cities that allow for inclusivity of all population groups. Like most South African cities, Cape Town is a relic of apartheid planning where the urban spatial patterns reinforce social exclusion among other issues. Urban and transport planning in Cape Town focuses on addressing issues of spatial inefficiencies, social exclusion, congestion due to rapid motorisation and the proliferation of informal settlements. It is against this backdrop that the central concern of this research is to understand urban dynamics linked to the spatiotemporal interaction of transport and land use in Cape Town to aid in the formulation of proactive urban policies. There is compelling evidence in the literature that dynamic integrated land use transport models provide an avenue through which the urban change process can be understood to aid in the development of adaptive land use and transport strategies. METRONAMICA, a dynamic land use transport model, is applied in this research to simulate and understand land use and transport change in Cape Town. A sequential stage-wise procedure was implemented to calibrate the model for the period 1995- 2005 and an independent validation was carried out from 2005 to 2010 to evaluate the model. Kappa statistic and its associated variants were applied to assess the ability of the land use model block to reproduce land use patterns while the EMME model and previous transport studies for Cape Town were used to evaluate the transport model. The results from the calibration and validation exercise show that the model can reproduce historical land use and transport patterns. The integration of the transport and land use model through accessibility improved the Kappa Simulation and Fuzzy Kappa Simulation. This showed that the model explained urban change better when land use and transport interacted compared to an independent land use model. This shows that accessibility can be employed in the Cape Town context to enhance the understanding of the urban change process. In addition to the Kappa statistics, the fractal dimension which measures the landscape complexity was used to assess the predictive accuracy of the model. The model performance revealed that the landscape patterns simulated by the model resemble observed land use patterns signifying a good calibration of the model. The calibrated land use transport model for the Cape Town Metropolitan region (CTMRLUT) was applied for policy scenarios. Three scenarios were simulated, specifically the business as usual (BAU), redressing social exclusion and the potential for in situ upgrading of informal settlements. The study found that intensive land use development along the Metro South East Integration Zone (MSEIZ) was linked to a reduction in commuting distances to economic activities which is in contrast to the BAU scenario. While these scenarios looked at the urban spatial patterns, the effect of land use patterns on congestion was also explored. The findings from the scenario simulations suggest that despite the reduction in distance to economic centres, the congestion condition in Cape Town will continue to deteriorate. Further, the findings indicate that interventions that only target land use developments are not sufficient to address congestion issues in Cape Town. Instead, to address the congestion problem in Cape Town, mixed land use and compact growth strategies need to be complemented with travel demand management strategies that target private car usage and intensive investment in transport infrastructure, especially rail, to facilitate the use of alternative modes. With regards to informal settlements, the study found that in situ upgrading could be a viable option to tackle some informal settlements. However, for proper inclusionary informal settlement policy, an approach that resonates with contextual realities would be more suitable to assess the viability of in situ upgrading based on the location of informal settlements relative to centres of economic activities. Additionally, the study revealed that instead of informal settlements locating as stand-alone settlements, some of them located adjacent to low-income housing which might be indicative of a growth in backyard shacks which is an existing housing trend in some lowincome suburbs in Cape Town. While this research has shown that integrating land use and transport in policy is potentially useful in solving urban issues, it has also revealed the value of urban modelling as a platform on which to assess the potential impacts of policies before their implementation. This is a strong case for the utilisation of decision support tools in land use and transport planning in contemporary South African cities.

This thesis focuses on solutions of reactive transport problems in porous media. The principle mechanisms of flow and reactive mass transport in porous media are investigated. Global implicit approach (GIA), where transport and reaction are fully coupled, and sequential noniterative approach (SNIA) are implemented into the software OpenGeoSys (OGS6) to couple chemical reaction and mass transport. The reduction scheme proposed by Kräutle is used in GIA to reduce the number of coupled nonlinear differential equations. The reduction scheme takes linear combinations within mobile species and immobile species and effectively separates the reaction-independent linear differential equations from coupled nonlinear ones (i.e. reducing the number of primary variables in the nonlinear system). A chemical solver is implemented using semi-smooth Newton iteration which employs complementarity condition to solve for equilibrium mineral reactions. The results of three benchmarks are used for code verification. Based on the solutions of these benchmarks, it is shown that GIA with the reduction scheme is faster (ca. 6.7 times) than SNIA in simulating homogeneous equilibrium reactions and (ca. 24 times) in simulating kinetic reaction. In simulating heterogeneous equilibrium mineral reactions, SNIA outperforms GIA with the reduction scheme by 4.7 times.:Declaration of Authorship iii Acknowledgements iv Abstract v List of Figures viii Symbols ix 1 Introduction 1 1.1 State of the Art 1 1.2 Thesis Objectives 3 1.3 Thesis Outline 4 2 Mathematical Models 5 2.1 Introduction 5 2.2 Mass Balance Equations 5 2.2.1 Groundwater Flow 6 2.2.2 Mass Transport 7 2.2.3 Chemical Reaction 8 2.2.3.1 Equilibrium Reaction 8 2.2.3.2 Kinetic Reaction 10 2.3 Reactive Mass Transport 10 2.4 Initial and Boundary Conditions 11 3 Numerical Solutions 12 3.1 Introduction 12 3.2 Coupling Schemes 12 3.2.1 Operator Splitting 13 3.2.2 Global Implicit 13 3.2.2.1 Standard Reduction Schemes 14 3.2.2.2 Kräutle’s Reduction Scheme 14 3.2.2.3 Local Chemical Solver 21 3.3 Space and Time Discretization 23 3.3.1 Finite Element Method 23 3.3.2 Time Discretization 25 3.3.3 Jacobian Matrix 26 3.4 Code Implementation 29 4 Benchmarks 30 4.1 Introduction 30 4.2 Cation Exchange 30 4.3 Dissolution and Precipitation 32 4.4 Mixing Controlled Biodegradation 33 5 Conclusions and Outlooks 38 5.1 Conclusions 38 5.2 Outlooks 39 / Diese Arbeit konzentriert sich auf die numerische Berechnung reaktiver Transportprobleme in porösen Medien. Es werden prinzipielle Mechanismen von Fluidströmung und reaktive Stofftransport in porösen Medien untersucht. Um chemische Reaktionen und Stofftransport zu koppeln, wurden die Ansätze Global Implicit Approach (GIA) sowie Sequential Non-Iterative Approach (SNIA) in die Software OpenGeoSys (OGS6) implementiert. Das von Kräutle vorgeschlagene Reduzierungsschema wird in GIA verwendet, um die Anzahl der gekoppelten nichtlinearen Differentialgleichungen zu reduzieren. Das Reduzierungsschema verwendet Linearkombinationen von mobilen und immobile Spezies und trennt die reaktionsunabhngigen linearen Differentialgleichungen von den gekoppelten nichtlinearen Gleichungen (dh Verringerung der Anzahl der Primärvariablen des nicht-linearen Gleichungssystems). Um die Gleichgewichtsreaktionen der Mineralien zu berechnen, wurde ein chemischer Gleichungslaser auf Basis von ”semi-smooth Newton-Iterations” implementiert. Ergebnisse von drei Benchmarks wurden zur Code-Verifikation verwendet. Diese Ergebnisse zeigen, dass die Simulation homogener Equilibriumreaktionen mit GIA 6,7 mal schneller und bei kinetischen Reaktionen 24 mal schneller als SNIA sind. Bei Simulationen heterogener Equilibriumreaktionen ist SNIA 4,7 mal schneller als der GIA Ansatz.:Declaration of Authorship iii Acknowledgements iv Abstract v List of Figures viii Symbols ix 1 Introduction 1 1.1 State of the Art 1 1.2 Thesis Objectives 3 1.3 Thesis Outline 4 2 Mathematical Models 5 2.1 Introduction 5 2.2 Mass Balance Equations 5 2.2.1 Groundwater Flow 6 2.2.2 Mass Transport 7 2.2.3 Chemical Reaction 8 2.2.3.1 Equilibrium Reaction 8 2.2.3.2 Kinetic Reaction 10 2.3 Reactive Mass Transport 10 2.4 Initial and Boundary Conditions 11 3 Numerical Solutions 12 3.1 Introduction 12 3.2 Coupling Schemes 12 3.2.1 Operator Splitting 13 3.2.2 Global Implicit 13 3.2.2.1 Standard Reduction Schemes 14 3.2.2.2 Kräutle’s Reduction Scheme 14 3.2.2.3 Local Chemical Solver 21 3.3 Space and Time Discretization 23 3.3.1 Finite Element Method 23 3.3.2 Time Discretization 25 3.3.3 Jacobian Matrix 26 3.4 Code Implementation 29 4 Benchmarks 30 4.1 Introduction 30 4.2 Cation Exchange 30 4.3 Dissolution and Precipitation 32 4.4 Mixing Controlled Biodegradation 33 5 Conclusions and Outlooks 38 5.1 Conclusions 38 5.2 Outlooks 39

No description available.

Bio-deterioration of concrete, which is very common in sewer system and waste water treatment plant, results in significant structure degradation. Normally, the process can be described by the two following parts: 1) Biochemistry reactions producing biogenic aggressive species in biofilms which are spread on the surface of concrete. As one of the most significant biogenic acid in sewer pipes, sulfuric acid (H2SO4) is produced by sulfur oxidizing bacteria (SOB). 2) Chemical reactions between biogenic aggressive species and cement hydration products which is responsible for concrete deterioration. A reactive transport model is proposed to simulate the bio-chemical and chemical deterioration processes of cementitious materials in contact with SOB and H2S or sulfuric acid solution. This model aims at solving simultaneously transport and biochemistry/chemistry in biofilms and cementitious materials by a global coupled approach. To provide an appropriate environment for SOB to grow, the surface neutralization of concrete (i.e., the absorption of H2S and aqueous H2S corrosion) is considered. To obtain the amount of biogenic H2SO4, the bio-oxidation of H2S by the activation of bacteria is simulated via a simplified model. To provide a suitable environment for SOB to grow, the abiotic pH reduction of concrete process is introduced. The production rate of H2SO4 is governed by the pH in the biofilms and the content of H2S in gas.It is assumed that all chemical processes are in thermodynamical equilibrium. The dissolution of portlandite (CH) and calcium silicate hydrates (C-S-H) and the precipitation of gypsum (C¯S H2) and calcium sulfide are described by mass action law and threshold of ion activity products. To take into account the continuous decrease of the Ca/Si ratio during the dissolution of C-S-H a generalization of the mass action law is applied. By simplifying the precipitation process of gypsum, a damage model is introduced to characterize the deterioration of concrete due to the swelling of gypsum. Thus, the porosity evolution and deterioration depth during deterioration process are taken into account. Only diffusion of aqueous species are considered. Different diffusion coefficients are employed for various ions and Nernst-Planck equation was implemented. The effect of the microstructure change during deterioration on transport properties is considered as well. For both biofilms and cementitious materials, the balance equations of total mass of each atom (Ca, Si, S, K, Cl) are used to couple transport equations and (bio-)chemical reactions. The model is implemented within a finite-volume code, Bil. Following the introduction of principle of the finite volume method, the coupling of the bio-chemistry process in biofilms and chemistry process in cementitious materials is illustrated. By this model, some experiments reported in literature, including chemical immersion tests (statical solution condition and flow solution condition) and microbiological simulation tests, are simulated. The numerical results and the experimental observations are compared and discussed. The influence of properties of cementitious materials (initial porosity, carbonated layer, etc.) and environmental factors (concentration of H2SO4, content of H2S, etc.) are investigated by this model as well. Furthermore, a long term predictionis conducted

Appraisal methodologies for congestion mitigation projects are relatively less well developed compared to methodologies for projects reducing free flow travel times. For instance, static assignment models are incapable of representing the build-up and dissipation of traffic queues, or capturing the experienced crowding caused by uneven on-board passenger loads. Despite the availability of dynamic traffic assignment, only few model systems have been developed for cost-benefit analysis of real applications. The six included papers present approaches and tools for analysing traffic and transit projects where congestion relief is the main target. In the transit case studies, we use an agent-based simulation model to analyse congestion and crowding effects and to conduct cost-benefit analyses. In the case study of a metro extension in Stockholm, we demonstrate that congestion and crowding effects constitute more than a third of the total benefits and that a conventional static model underestimates these effects vastly. In another case study, we analyse various operational measures and find that the three main measures (boarding through all doors, headway-based holding and bus lanes) had an overall positive impact on service performance and that synergetic effects exist. For the congestion charging system in Gothenburg, we demonstrate that a hierarchal route choice model with a continuous value of time distribution gives realistic predictions of route choice effects although the assignment is static. We use the model to show that the net social benefit of the charging system in Gothenburg is positive, but that low income groups pay a larger share of their income than high income groups. To analyse congestion charges in Stockholm however, integration of dynamic traffic assignment with the demand model is necessary, and we demonstrate that this is fully possible. Models able to correctly predict these effects highlight the surprisingly large travel time savings of pricing policies and small operational measures. These measures are cheap compared to investments in new infrastructure and their implementation can therefore lead to large societal gains. / <p>QC 20160829</p>

Brackish springs are relatively frequent phenomena in coastal carbonate formations and their existence has been extensively reported in Mediterranean coasts. In fact, more than 300 brackish springs have been identified only in the coast of the former Yugoslavia. They essentially consist of inland or submarine karst outlets discharging waters with flow-dependent salinity. The phenomenon is particularly surprising in inland springs, where high flow rates with significant salinities (presumably coming from the sea) may be discharged several meters above sea level. In addition to its scientific interest, brackish springs hold a strategic potential as a source of water in areas with often limited water resources. In order to design their appropriate management a quantitative understanding of their controlling mechanisms both in general and at every particular spring has to be achieved.These mechanisms have been studied for many years but some controversy still remains. It is clear that they are related to deep well developed karst systems. Under these conditions, groundwater flows in a turbulent mode through a network of interconnected conduits immersed in a porous matrix with slow Darcyan flow velocities. Surprisingly, different models to explain the functioning of the system, although based on different conceptual and methodological approaches lead to similar results. This sugests that a global study on the salinitzation mechanisms of brackish springs should be undertaken. Here, we first derive the equations governing turbulent flow for density-dependent fluids and describe different mechanisms of salinization of inland brackish springs, in order to compare with the spring discharge and concentration response for those mechanisms of salinization.The insights gained in this analysis are applied to the study of S'Almadrava spring (Mallorca, Spain). This spring discharges up to 2 m3/s with salinities of 20 mS/cm at an elevation of 8 m.a.s.l. It generally displays an inverse relation between discharge rate and concentration (i.e., discharging higher salinity waters for low flow rates, and vice versa). A hypothetical but geologically feasible dual permeability model is proposed to reproduce observed salinity variations for both the dry and wet seasons but also to explain the secondary salinity peaks observed after every rainfall event. Model results agree with observations, but the lack of geological information at depth impedes model validation. Therefore, a second validation of the conceptual model is undertaken based on high-frequency geochemical observations. Due to the highly dynamic conditions of the system, the geochemical data was analyzed using fully coupled reactive transport modelling. The interpretation of geochemical data not only helps on validating conceptual models but also yields information on the water-rock interaction processes occurring at deep carbonate systems. In fact, one of the processes initially proposed to explain the occurrence of well-developed karst systems at depth, is the enlargement of tectonic fissures by carbonate dissolution due to the mixing of fresh and seawater.The theory of dissolution by mixing waters is based on the fact that when two solutions are mixed, concentrations in the mixture are volume weighted averages of the two end-members, but the thermodynamic activities of the species controlling the water-mineral reactions are non linear functions of the mixing ratio. Therefore, two end-member solutions in equilibrium with a solid phase could lead to an undersaturated mixture depending on several factors, most notably CO2 content and ionic strength. Observation of mixing and carbonate dissolution at depth has not been possible because of technical difficulties. More accessible to observation is the seawater mixing zone in coastal aquifers where calcite undersaturation and/or calcite dissolution have been reported numerous times. Yet, dissolution in coastal environments is not always clear and oversaturation or lack of dissolution in mixing zones have also been described. This apparent inconsistency on field observations around the world prompted the studies of the second part of the thesis. Flow-through laboratory experiments were performed in CO2-controlled atmosphere in order to quantify the dependence of the dissolution of calcite with the mixing ratio, and the role that CO2 variations may have on enhancing the dissolution capacity of the mixture. Results show that, although dissolution occurs, the major carbonate dissolution in aquifers must be considered only in a geological time scale. Sanford and Konikow (1989) predicted the location and magnitude of long term porosity development of coastal aquifers, based on a two step method. We compare their results with a reactive transport model approach in 1D and 2D, showing that reactive transport is required to properly understand the phenomenon because it is found that dissolution is controlled not only by geochemical factors but also by the rate at which fresh and salt water mix (i.e., by dispersion).