Dissertations / Theses on the topic 'Coastal aquifers'
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1
Park, Chan-Hee. "Saltwater Intrusion in Coastal Aquifers." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4857.
Full textAbstract:
Utilizing the analytical solution of the steady state sharp interface saltwater intrusion model in coastal aquifers, a multi-objective optimization formulation of pumping rates and well locations in a coastal aquifer is formulated to solve problems in water management practice. The proposed optimization problem uses progressive genetic algorithm technique and the method developed is applied to the previous work of Cheng et al. [2000]. Through this analysis, several other applications are provided to demonstrate the use of the model in practical applications. This work is the first to optimize pumping rates as well as well locations simultaneously in coastal aquifer management.
Known the limitation of the analytical solution, the work is expanded to cover the physics of saltwater intrusion in a more realistic way. This is variable density flow in a variably saturated porous medium. In this method, mixing between two fluids such as saltwater and freshwater can be described and the porous medium is also expanded to cover saturated and unsaturated zones together. One of the objectives is to develop a three dimensional physical model, verify the model, and apply to various applications in coastal aquifers.
The developed model, TechFlow, is used to investigate instability issues associated with the numerical solution of the Elder problem in the perspective that includes physical instability issues associated with density differences used in numerical solutions, sensitivity of the solution to idealization irregularity, and the importance of accurate estimation of the velocity field and its association to the grid density levels that is necessary to solve the problem accurately.
Saltwater intrusion hydrodynamics in a beach under the influence of tidal effects is also investigated using TechFlow. Based on the results of TechFlow with the use of various boundary conditions for the transport equation, the saltwater intrusion hydrodynamics in a beach under the influence of tidal effects shows unique dynamics. These solutions are primarily affected by density differences, tidal effects on a mild slope, variably saturated porous medium and finite domain solution condition. TechFlow is also used to investigate saltwater upconing beneath pumping wells both two- and three-dimensional applications.
2
Teo, Hhih-Ting, and h. teo@griffith edu au. "Tidal Dynamics in Coastal Aquifers." Griffith University. School of Engineering, 2003. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20030729.155028.
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The prediction of coastal groundwater movement is necessary in coastal management. However, the study in this field is still a great challenge due to the involvement of tidal-groundwater interactions and the phenomena of hydrodynamic dispersion between salt-fresh water in the coastal region. To date, numerous theories for groundwater dynamic have been made available in analytical, numerical and also experimental forms. Nevertheless, most of them are based on the zeroth-order shallow flow, i.e. Boussinesq approximation. Two main components for coastal unconfined aquifer have been completed in this Thesis: the vertical beach model and the sloping beach model. Both solutions are solved in closed-form up to higher order with shallow water parameter ([epsilon]) and tidal amplitude parameter ([alpha]). The vertical beach solution contributes to the higher-order tidal fluctuations while the sloping beach model overcomes the shortcomings in the existing solutions. From this study, higher-order components are found to be significant especially for larger value of [alpha] and [epsilon]. Other parameters such as hydraulic conductivity (K) and the thickness of aquifer (D) also affect the water table fluctuations. The new sloping solution demonstrated the significant influence of beach slope ([beta]) on the water table fluctuations. A comprehensive comparison between previous solution and the present sloping solution have been performed mathematically and numerically and the present solution has been demonstrated to provide a better prediction
3
Teo, Hhih-Ting. "Tidal Dynamics in Coastal Aquifers." Thesis, Griffith University, 2003. http://hdl.handle.net/10072/365678.
Full textAbstract:
The prediction of coastal groundwater movement is necessary in coastal management. However, the study in this field is still a great challenge due to the involvement of tidal-groundwater interactions and the phenomena of hydrodynamic dispersion between salt-fresh water in the coastal region. To date, numerous theories for groundwater dynamic have been made available in analytical, numerical and also experimental forms. Nevertheless, most of them are based on the zeroth-order shallow flow, i.e. Boussinesq approximation. Two main components for coastal unconfined aquifer have been completed in this Thesis: the vertical beach model and the sloping beach model. Both solutions are solved in closed-form up to higher order with shallow water parameter ([epsilon]) and tidal amplitude parameter ([alpha]). The vertical beach solution contributes to the higher-order tidal fluctuations while the sloping beach model overcomes the shortcomings in the existing solutions. From this study, higher-order components are found to be significant especially for larger value of [alpha] and [epsilon]. Other parameters such as hydraulic conductivity (K) and the thickness of aquifer (D) also affect the water table fluctuations. The new sloping solution demonstrated the significant influence of beach slope ([beta]) on the water table fluctuations. A comprehensive comparison between previous solution and the present sloping solution have been performed mathematically and numerically and the present solution has been demonstrated to provide a better predictionThesis (Masters)
Master of Philosophy (MPhil)
School of Engineering
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4
Costall, Alexander Ross. "Hydro-geophysics in High-Quality Coastal Aquifers." Thesis, Curtin University, 2020. http://hdl.handle.net/20.500.11937/82107.
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Electrical resistivity imaging (ERI) and groundwater solute transport modelling are developed for recovery of the hydrogeological architecture of coastal margins. ERI acquisition and processing parameters, along with the influence of hydraulic anisotropy and heterogeneity in karstic aquifers, are explored with examples selected along more than 100 km of coastline proximal to Perth Western Australia. The methods will contribute to accurate predictive groundwater modelling and sustainable management of high-quality coastal aquifers worldwide.
5
Demirbas, Korkut. "Optimal Management Of Coastal Aquifers Using Heuristic Algorithms." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613135/index.pdf.
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Excessive pumping in coastal aquifers results in seawater intrusion where optimal and efficient planning is essential. In this study, numerical solution of single potential solution by Strack is combined with genetic algorithm (GA) to find the maximum extraction amount in a coastal aquifer. Seawater intrusion is tracked with the potential value at the extraction well locations. A code is developed by combining GA and a subroutine repeatedly calling MODFLOW as a numerical solver to calculate the potential distribution for different configurations of solution (trial solutions). Potential distributions are used to evaluate the fitness values for GA. The developed model is applied to a previous work by Mantoglou. Another heuristic method, simulated annealing (SA) is utilized to compare the results of GA. Different seawater prevention methods (i.e. injection wells, canals) and decision variables related to those methods (i.e. location of the injection wells or canals) are added to model to further prevent the seawater intrusion and improve the coastal aquifer benefit. A method called &ldquoAlternating Constraints Method&rdquo
is introduced to improve the solution for the cases with variable location. The results show that both proposed method and the regular solution with GA or SA prove to be successful methods for the optimal management of coastal aquifers.
6
Karam, Hanan Nadim. "Seawater circulation in coastal aquifers : processes and impacts." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78141.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 150-154).
This thesis explores the subterranean domain of chemical cycling in coastal oceans abutting permeable aquifers, where transport through sediments is dominated by advection, rather than diffusion. We investigate the mechanisms by which seawater circulates in the subsurface over a range of spatio-temporal scales, and the chemical reactions to which this circulation is coupled. Seawater circulation in coastal aquifers is driven by salinity variations in pore water as well as by the effects of temporally variable forcings at both terrestrial (variable recharge) and marine (tides, waves and secular sea level changes) boundaries. It is coupled to the transport of biogeochemically reactive species through the subsurface and their exchange between the sediments and the water column. Our understanding of how different forcing mechanisms interact to determine spatial scales and residence times of subsurface seawater circulation, as well as temporal patterns and rates of aquifer-surface water exchange has thus far been very limited. The large range in the spatial and temporal scales of flow dynamics associated with different forcings challenges our ability to comprehensively observe and monitor their associated seafloor fluxes. In this thesis, we present a novel, homemade instrument for high-resolution, long-term monitoring of seafloor fluxes, designed to address this challenge. Two-year deployments of several such instruments at Waquoit Bay, MA, produced the most comprehensive datasets on seafloor fluxes available to date, multiplying the length of published time series by tenfold. The length and integrity of the datasets permit the use of spectral analysis to investigate distinct frequency components of seafloor fluxes and quantify their relationship to various forcing mechanisms. The temporal and areal coverage of the datasets allow us to distinguish the contributions of different forcings to observed fluxes, as a function of distance from shore and season. Furthermore, we discuss new insight derived from the data into the physics underlying observed seafloor fluxes and their associated subsurface circulation processes. Additionally, we describe results from an independent but related project to characterize chemical dynamics associated with seawater circulation in beach sand at Waquoit Bay. We present evidence for the important contribution of this circulation to the nitrogen budget of the Bay.
by Hanan Nadim Karam.
Ph.D.
7
Mary, Makokha. "Seawater intrusion and contaminant transport in coastal aquifers." Kyoto University, 2008. http://hdl.handle.net/2433/136601.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第13874号
農博第1689号
新制||農||953(附属図書館)
学位論文||H20||N4341(農学部図書室)
UT51-2008-C790
京都大学大学院農学研究科地域環境科学専攻
(主査)准教授 小林 晃, 教授 河地 利彦, 教授 川島茂人
学位規則第4条第1項該当
8
Sun, Dongmin. "Aquitard control of stream-aquifer interaction and flow to a horizontal well in coastal aquifers." Diss., Texas A&M University, 2005. http://hdl.handle.net/1969.1/4740.
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This dissertation is composed of three parts of major contributions: In Chapter II, we developed a new conceptual model and derived a new semi-analytical model for flow to a horizontal well beneath a water reservoir. Instead of treating the leakage from aquitard as a source term inside the aquifer which is called HantushâÂÂs assumption (1964), we linked flows in aquitard and aquifer by the idea of continuity of flux and drawdown. The result in this chapter is compared with that of Zhan and Park in 2003 which HantushâÂÂs assumption is adopted at various hydraulic and well configurations. It shows that HantushâÂÂs assumption becomes inaccurate in regions where vertical velocity components are significant. In Chapter III, we deal with the interaction of an aquifer with two parallel surface water bodies such as two streams or canals. In this chapter, new closed-form analytical and semi-analytical solutions are acquired for the pumping induced dynamic interaction between two streams and ground water for two different cases. In the first case, the sediment layers separating the streams from the aquifer ground water do not exist. In the second case, the two low permeable layers are considered. The effect of aquitard and water right competition is addressed in this chapter. This model can be used for interpreting and deriving hydrologic parameters of aquitard and aquifer when pumping occurs between two channels. It can also be used to predict stream depletion which is essential for water management and ecology conservation. In Chapter IV, we investigated the three dimensional upconing due to a finite-length of horizontal well and its critical conditions. The results are compared with those of vertical wells. The critical condition which includes the critical rise and the critical time at a certain pumping rate depends on the well length, the initial interface location, the well location, and the pumping rate. Our results show that horizontal well might be a better tool for coastal groundwater resources development. In real field applications, installing long wells as shallow as possible is always desirable for sustaining long periods of pumping with significant rates.
9
Ayutthaya, Sarinya Sanitwong-Na. "Impacts of climate change on groundwater levels in coastal aquifers." Thesis, University of Dundee, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.505624.
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10
Cumming, Benjamin Donald. "Modelling sea water intrusion in coastal aquifers using heterogeneous computing." Thesis, Queensland University of Technology, 2012. https://eprints.qut.edu.au/61038/1/Benjamin_Cumming_Thesis.pdf.
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The objective of this PhD research program is to investigate numerical methods for simulating variably-saturated flow and sea water intrusion in coastal aquifers in a high-performance computing environment. The work is divided into three overlapping tasks: to develop an accurate and stable finite volume discretisation and numerical solution strategy for the variably-saturated flow and salt transport equations; to implement the chosen approach in a high performance computing environment that may have multiple GPUs or CPU cores; and to verify and test the implementation.
The geological description of aquifers is often complex, with porous materials possessing highly variable properties, that are best described using unstructured meshes. The finite volume method is a popular method for the solution of the conservation laws that describe sea water intrusion, and is well-suited to unstructured meshes. In this work we apply a control volume-finite element (CV-FE) method to an extension of a recently proposed formulation (Kees and Miller, 2002) for variably saturated groundwater flow. The CV-FE method evaluates fluxes at points where material properties and gradients in pressure and concentration are consistently defined, making it both suitable for heterogeneous media and mass conservative. Using the method of lines, the CV-FE discretisation gives a set of differential algebraic equations (DAEs) amenable to solution using higher-order implicit solvers.
Heterogeneous computer systems that use a combination of computational hardware such as CPUs and GPUs, are attractive for scientific computing due to the potential advantages offered by GPUs for accelerating data-parallel operations. We present a C++ library that implements data-parallel methods on both CPU and GPUs. The finite volume discretisation is expressed in terms of these data-parallel operations, which gives an efficient implementation of the nonlinear residual function. This makes the implicit solution of the DAE system possible on the GPU, because the inexact Newton-Krylov method used by the implicit time stepping scheme can approximate the action of a matrix on a vector using residual evaluations. We also propose preconditioning strategies that are amenable to GPU implementation, so that all computationally-intensive aspects of the implicit time stepping scheme are implemented on the GPU.
Results are presented that demonstrate the efficiency and accuracy of the proposed numeric methods and formulation. The formulation offers excellent conservation of mass, and higher-order temporal integration increases both numeric efficiency and accuracy of the solutions. Flux limiting produces accurate, oscillation-free solutions on coarse meshes, where much finer meshes are required to obtain solutions with equivalent accuracy using upstream weighting. The computational efficiency of the software is investigated using CPUs and GPUs on a high-performance workstation. The GPU version offers considerable speedup over the CPU version, with one GPU giving speedup factor of 3 over the eight-core CPU implementation.
11
Felisa, Giada <1983>. "Dynamics of coastal aquifers: data-driven forecasting and risk analysis." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/7177/1/felisa_giada_tesi.pdf.
Full textAbstract:
This work is focused on the study of saltwater intrusion in coastal aquifers, and in particular on the realization of conceptual schemes to evaluate the risk associated with it.
Saltwater intrusion depends on different natural and anthropic factors, both presenting a strong aleatory behaviour, that should be considered for an optimal management of the territory and water resources. Given the uncertainty of problem parameters, the risk associated with salinization needs to be cast in a probabilistic framework. On the basis of a widely adopted sharp interface formulation, key hydrogeological problem parameters are modeled as random variables, and global sensitivity analysis is used to determine their influence on the position of saltwater interface. The analyses presented in this work rely on an efficient model reduction technique, based on Polynomial Chaos Expansion, able to combine the best description of the model without great computational burden.
When the assumptions of classical analytical models are not respected, and this occurs several times in the applications to real cases of study, as in the area analyzed in the present work, one can adopt data-driven techniques, based on the analysis of the data characterizing the system under study. It follows that a model can be defined on the basis of connections between the system state variables, with only a limited number of assumptions about the "physical" behaviour of the system.
12
Felisa, Giada <1983>. "Dynamics of coastal aquifers: data-driven forecasting and risk analysis." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/7177/.
Full textAbstract:
This work is focused on the study of saltwater intrusion in coastal aquifers, and in particular on the realization of conceptual schemes to evaluate the risk associated with it.
Saltwater intrusion depends on different natural and anthropic factors, both presenting a strong aleatory behaviour, that should be considered for an optimal management of the territory and water resources. Given the uncertainty of problem parameters, the risk associated with salinization needs to be cast in a probabilistic framework. On the basis of a widely adopted sharp interface formulation, key hydrogeological problem parameters are modeled as random variables, and global sensitivity analysis is used to determine their influence on the position of saltwater interface. The analyses presented in this work rely on an efficient model reduction technique, based on Polynomial Chaos Expansion, able to combine the best description of the model without great computational burden.
When the assumptions of classical analytical models are not respected, and this occurs several times in the applications to real cases of study, as in the area analyzed in the present work, one can adopt data-driven techniques, based on the analysis of the data characterizing the system under study. It follows that a model can be defined on the basis of connections between the system state variables, with only a limited number of assumptions about the "physical" behaviour of the system.
13
Batista, Filho Job Jesus. "A dinamica das aguas subterraneas no estuario do Rio Itanhaem, litoral sul do Estado de São Paulo." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/287665.
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Orientador: Sueli Yoshinaga PereiraDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociencias
Made available in DSpace on 2018-08-07T09:50:38Z (GMT). No. of bitstreams: 1 BatistaFilho_JobJesus_M.pdf: 4294081 bytes, checksum: 28f487525ec460febd41ef1f05e36218 (MD5) Previous issue date: 2006
Resumo: O presente trabalho estuda a interferência da maré nos aqüíferos costeiros, identificando alterações hidrodinâmicas e químicas em suas águas. A pesquisa foi realizada no estuário do rio Itanhaém, em duas localidades: no Sitio de Pesquisa, com 7 poços instalados, situados às margens do rio Acima, a 3,5 km do oceano, e no CePeRio - Centro de Pesquisa do Estuário do rio Itanhaém, com 1 poço, localizado a aproximadamente 1 km do oceano. O estudo foi executado em 3 etapas, buscando-se conhecer: a geologia dos aqüíferos, suas características físicas, químicas e geométricas. Para os aspectos hidrodinâmicos, englobaram-se o monitoramento do nível d'água superficial e subterrâneo e os cálculos dos parâmetros hidrodinâmicos, como: condutividade hidráulica, velocidade média linear e transmissividade. Para a hidroquímíca foram executadas coletas periódicas, a cada 45 minutos, análise dos parâmetros físicoquímicos: temperatura, pR, Eh, condutividade elétrica (CE), sólidos totais dissolvidos (STD) e salinidade. Foram coletadas amostras em cada etapa para se an$l.lisar a composição química das águas estudadas, quantificando-se os seguintes íons: Na, K, Si, Mg, Ca, Sr, Co, Mn, Cu, P, Zn, Pb, AI, Ba, Cd, N~, Fe, Cr, RC03-, F- ,cr ,Br- ,N ,S042- e PO/- . Os aqüíferos estudados, um livre e um confmado, são compostos de sedimentos arenosos de granulometria fina. O aqüífero confinado é composto de areia com lente df. conchas calcáreas, à profundidade de 20 metros. As águas superficiais monitoradas foram: as dos rios Acima, Itanhaém e do ribeirão Campininha, que margeiam as áreas estudadas. O aqüífero livre, formado por areia fina, e o rio Acima apresentam águas sulfatadas ou cloretadas sódicas. No aqüífero, o STD varia de 40 a 70 mg/L e o pH é ácido (entre 4 e 5); no rio, o STD varia de 90 a 5.900 mgIL e o pH de 6 a 7. O aqüífero confinado, com argila siltosa na sua base e conchas calcáreas na sua estrutura, apresenta águas bicarbonatadas sódicas, com STD variando de 310 a 2.000 mg/L e pH neutro (entre 6 e 7,5). O aqüífero livre, com condutividade hidráulica (10 de 10-4 m/s, possui influência direta das oscilações da maré, com uma variação de amplitude do nível d'água (NA) 5 vezes menor que a da maré; o aqüífero confinado, com K igual a 10-6 m/s, oscila 11 vezes menos que a maré, com maior variação de 1,4 m. A direção do fluxo hidrodinâmico no aqüífero livre é para NW e a do confinado é para WSW, ambos com descarga no rio Acima. O aqüífero livre tem velocidade média linear da ordem de 10-6 m/s e transmissividade de 205 m2/dia, e o confinado 10-8 m/s e 13 m2/dia. Apenas no aqüífero livre, durante subidas fortes da maré, o fluxo hidrodinâmico se altera, derivando para o norte. Hidroquimicamente, as águas subterrâneas variam pouco com a intrusão salina. No inverno, as águas superficiais são mais salobras que em outras épocas do ano, o que está associado a fatores como: a maré mafs alta e a pluviometria reduzida
Abstract: The present work studied the influence of the tide in the coastal aquifers by identifying hydrodynamic and chemical alterations in the aquifiers. The research was carried out in the Itanhaém river estuary in two localities: in the Sitio de Pesquisa with 7 installed wells situated on the banks of the Acima river, 3,5 km from the ocean, and in the CePeRio - Center of Research ofthe ltanhaém river estuary with 1 well located approximately 1 km from the oceano The study was executed in 3 stages that studied the geologic formations of the aquifers and their physical, chemical and geometric characteristics. The hydrodynamic aspects were studied by monitoring of the superficial and underground water leveI, and hydrodynamic parameters such as hydraulical condutivity, linear average velocity and transmissivity were determined. The hydrochemical part of the research was executed with periodic collections of samples every 45 minutes and analyzed for the physical chemical parameters of temperature, pH, Eh, electric condutivity (EC), total dissolved solids (TDS) and salinity. AIso, samples were collected for each stage of the study and analyzed for the following íons: Na, K; Si, Mg, Ca, Sr, Co, Mo, Cu, P, Zn, Pb, AI, Ba, Cd, Ni, Fe, Cr, HC03-, F- ,cr ,Br- ,N ,sot e P043- . The aquifers, one phreatic and one confined,rare both composites of fine sand sediments. The confined one is a sand layer with presences of limestone shells and has a depth of 20 meters. The surface waters were also monitored in the Acima river, the Campininha brook and the Itanhaém river, which border the study area. The phreatic aquifer is formed of fine sand and with the Acima river has sodium sulfated or chlorinated and sodium bicarbonated water. In the aquifer, the TDS varied between 40 and 70 mg/L and pH was acidic (between 4 and 5). In the river, the TDS varied from 90 to 5,900 mg/L and pH was 6 to 7. The confined aquifer, with silt clay and limestone shell, had sodic bicarbonated waters with the TDS varying from 310 to 2,000 mg/L and pH neutral (between 6 and 7,5). The phreatic aquifer with hydraulical condutivity (K) 10-4 m/s had a direct influence from tidal oscillations with a variation of phreatic leveI amplitude 5 times lesser than that of the tide. The confined aquifer with K of 10-6 m/s, oscillated 11 times less than the tide for variations of larger than 1,4 m. The hydrodynamic flow direction for the phreatic aquifer was to NW and for the confined one it was for WSW, both with discharges in the Acima river. The phreatic aquifer had linear average velocity of the order of 10-6 m/s with a transmissivity of 205 m2/day and for the confined the values were 10-8 m/s and 13 m2/day. In the phreatic aquifer the hydrodynamic flow was modified during strong flows of the tide northward. Hydrochemically, the groundwater varied slightly with saline intrusion. In the winter, the river had the biggest ionic concentrations in comparison to the other seasons which were associated with factors such as the tide being higher in and the low precipitation at that time of year
Mestrado
Geologia e Recursos Naturais
Mestre em Geociências
14
Hussain, Mohammed Salih. "Numerical simulation and effective management of saltwater intrusion in coastal aquifers." Thesis, University of Exeter, 2015. http://hdl.handle.net/10871/19239.
Full textAbstract:
Seawater intrusion (SWI) is a widespread environmental problem, particularly in arid and semi-arid coastal areas. Unplanned prolonged over-pumping of groundwater is the most important factor in SWI that could result in severe deterioration of groundwater quality. Therefore, appropriate management strategies should be implemented in coastal aquifers to control SWI with acceptable limits of economic and environmental costs. This PhD project presents the development and application of a simulation-optimization (S/O) model to assess different management methods of controlling saltwater intrusion while satisfying water demands, and with acceptable limits of economic and environmental costs, in confined and unconfined coastal aquifers. The first S/O model (FE-GA) is developed by direct linking of an FE simulation model with a multi-objective Genetic Algorithm (GA) to optimize the efficiency of a wide range of SWI management scenarios. However, in this S/O framework, several multiple calls of the simulation model by the population-based optimization model, evaluating best individual candidate solutions resulted in a considerable computational burden. To solve this problem the numerical simulation model is replaced by an Evolutionary Polynomial Regression (EPR)-based surrogate model in the next S/O model (EPR-GA). Through these S/O approaches (FE-GA and EPR-GA) the optimal coordinates and rates of the both abstraction and recharge barriers are determined in the studied management scenarios. As a result, a new combined methodology, so far called ADRTWW, is proposed to control SWI. The ADRTWW model consists of deep Abstraction of saline water near the coast followed by Desalination of the abstracted water to a potable level for public uses and simultaneously Recharging the aquifer using a more economic source of water such as treated wastewater (TWW). In accordance to the available recharge options (injection through well or infiltration from surface pond), the general performance of ADRTWW is evaluated in different hydro-geological settings of the aquifers indicating that it offers the least cost and least salinity in comparison with other scenarios. The great capabilities of both developed S/O models in identification of the best management solutions and the optimal coordinates and rates of the abstraction well and recharge well/pond are discussed. Both FE-GA and EPR-GA can be successfully employed by a robust decision support system. In the next phase of the study, the general impacts of sea level rise (SLR), associated with its transgression nature along the coastline surface on the saltwater intrusion mechanism are investigated in different hypothetical and real case studies of coastal aquifer systems. The results show that the rate and the amount of SWI are considerably greater in aquifers with flat shoreline slopes compared with those with steep slopes. The SWI process is followed by a significant depletion in quantity of freshwater resources at the end of the century. The situation is exacerbated with combined action of SLR and groundwater withdrawals. This finding is also confirmed by 3D simulation of SWI in a regional coastal aquifer (Wadi Ham aquifer) in the UAE subjected to the coupled actions of SLR and pumping.
15
Schultz, Gregory Michael. "Hydrologic and geophysical characterization of spatial and temporal variations in coastal aquifer systems." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/27071.
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16
Matengu, Brian Munihango. "Groundwater assessment and sustainable management of the coastal alluvial aquifers in Namib Desert, Namibia: Omdel Aquifer as case study." University of Western Cape, 2020. http://hdl.handle.net/11394/7852.
Full textAbstract:
Philosophiae Doctor - PhDThe study addressed the groundwater assessment and sustainable management of the coastal alluvial aquifers in Namib Desert, the Omaruru River Delta Aquifer (Omdel Aquifer) was used as a case study. Sustainable utilization of groundwater in parts of hyper-arid Sub-Saharan Africa, like the Namib Desert, is always a challenge due to lack of resources and data. Understanding of hydrogeological characteristics of the Omaruru Delta Aquifer System is a pre-requisite for the management of groundwater supply in the Central Namib area (Namib Desert). For the Omdel Aquifer in the Omaruru catchment, Namibia, issues to investigate include the lack of information on the geology and hydrogeological setting, the hydraulic properties and geometry of the aquifer at the inflow and outflow sections, groundwater recharge conditions upstream of the aquifer, and the impact of artificial recharge.
17
Basdurak, Berkay Nuvit. "Analysis Of Saltwater Intrusion And Investigations On Prevention Techniques In Coastal Aquifers." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12604734/index.pdf.
Full textAbstract:
In this study the saltwater intrusion in coastal aquifers is briefly described and the prevention techniques are discussed. By using two computer models SWI and SHARP, the movement of freshwater and saltwater is analyzed on hypothetical cases and on one real aquifer in Marmaris in the coast of Mediterranean Region. Artificial recharge and subsurface barrier techniques are applied to hypothetical cases as means of controling the saltwater intrusion. The performance of strip recharge and subsurface barrier in reducing the salt water intrusion is analyzed by simulation of the groundwater flow with the codes mentioned above. The results obtained are compared with each other. The results of hypothetical cases are relatively in good agreement. For the real aquifer the results show discrepancy that cannot be ignored.
18
RAMLI, MUHAMMAD. "NUMERICAL MODELING OF GROUNDWATER FLOW IN MULTI-LAYER AQUIFERS AT COASTAL ENVIRONMENT." 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/77971.
Full textAbstract:
Kyoto University (京都大学)0048
新制・課程博士
博士(工学)
甲第14599号
工博第3067号
新制||工||1456(附属図書館)
26951
UT51-2009-D311
京都大学大学院工学研究科都市環境工学専攻
(主査)教授 大西 有三, 教授 間瀬 肇, 准教授 西山 哲
学位規則第4条第1項該当
19
Manyama, Kinsley. "Hydrogeophysical characterisation of shallow coastal aquifers in the Western Cape, South Africa." University of the Western Cape, 2017. http://hdl.handle.net/11394/5972.
Full textAbstract:
Magister Scientiae - MSc (Environ & Water Science)Coastal aquifers present a key groundwater resource for freshwater supply in many coastal zones of Africa, and its availability is largely driven by the physical hydrogeological properties. An understanding of the aquifer properties in coastal areas is fundamental in that these aquifers present unique resource largely controlled to a very large extent by its geological and hydrological features and process. This study thus analysed information of resistivity variation of formations, drilling samples, water levels and slug test data, in an attempt to characterise aquifers in the coastal region of the Heuningnes Catchment, Western Cape. This was in an effort to address the issue of limited knowledge on key hydrogeological properties of aquifers in coastal regions. Resistivity survey results indicated that the shallow aquifers in the study area were limited in extent, had a poor potential, with resistant layers occurring below shallow, high conductive formations. The long profile of the wellpoints revealed that the area is underlain by various layers of material of consolidated to unconsolidated form. The hard rocks formations are overlain by sandy materials of fluvial origin, and clay material with marine deposits (mollusc shells). This findings were in agreement with the results of the resistivity models. In addition, the findings indicated that the saturation thickness of the aquifers was also small. The findings of the study on aquifer properties indicated that, hydraulic conductivity (K), transmissivity (T) and borehole yields were generally poor and small. Estimates of K and T ranged from 0.0030 to 0.2856 m/day and from 0.0008 to10.993 m2/day accordingly, while average borehole yields were at 0.55 l/s, with productivity of the aquifers classified as low to moderate. These were indicative of a low permeability environment, with low yielding formations. An updated conceptual groundwater flow model developed in this study, revealed a rather compacted groundwater flow systems, in which local and intermediate flows were dominant. These findings in this study support the view that aquifers in coastal regions were predominantly characterised by shallow depth, patchy distribution and low potential.
2019-04-30
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Ryan, Joseph Nolte. "Groundwater colloids in two Atlantic coastal plain aquifers : colloid formation and stability." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14560.
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Kriyo, Sambodho. "The Dynamics of Groundwater Flow and Salinity Transport in Unconfined Coastal Aquifers." 京都大学 (Kyoto University), 2010. http://hdl.handle.net/2433/97967.
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Nguyen, Bach Thao. "Coupling geophysical and isotopic approaches to better simulate saltwater intrusion into coastal aquifers : a case study in the Crau aquifer." Thesis, Avignon, 2016. http://www.theses.fr/2016AVIG0052/document.
Full textAbstract:
La recherche a porté sur les contraintes reliées à la modélisation des écoulements des eaux souterraines en aquifère côtier. Dans ces aquifères, la présence concomitante d’eaux douces et d’eaux salées modifient les patrons d’écoulement classiquement représentés par l’équation de Darcy. L’influence de la salinité de l’eau sur ses propriétés (densité) et sur la perméabilité du milieu complexifie la représentation mathématique des équations d’écoulement et la résolution des systèmes d’équations. Par ailleurs, l’influence des hétérogénéités du milieu rend plus difficile et hasardeux le paramétrage des modèles et leur calibration. Pour ce faire, nous avons proposé d’utiliser les résultats d’investigations géophysiques et isotopiques des eaux. Une meilleure description du milieu souterrain et l’imagerie de l’interface eau douce/eau salée peut en effet aider à un meilleur paramétrage et à une validation accrue de la simulation des écoulements des nappes côtières. Les mesures géochimiques telles celles des isotopes du radium ont aidé à la validation des flux et concentrations simulés. Notre approche a été appliquée sur la partie aval de la nappe de la Crau. La comparaison des résultats simulés par le modèle aux données de terrain résultant des suivis réalisés ont montré l’intérêt et l’applicabilité et la validation de notre approche méthodologiqueThe research has focused on the constraints related to the modeling of groundwater in coastal aquifer. In these aquifers, the concomitant presence of freshwater and saltwater alters the flow patterns typically represented by the Darcy equation. The influence of salinity on density and permeability complex the mathematical resolution of flow equations. Moreover, the influence of heterogeneities of aquifer makes it more difficult and risky the model parameterization and its calibration. We propose to use fort that the results of both geophysical and isotopic investigations. Thus, we hypothesize that the description of the subsurface and the imaging of the freshwater/saltwater can help to setup and validate the simulation of groundwater in coastal aquifers. Also we have shown that geochemical measurements such as radon may help to validate the simulated flow. Our approach was applied on the downstream part of the Crau aquifer. The comparison of simulated results to data resulting from monitoring has shown the usefulness and applicability of our approach
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Ezzy, Timothy Robert. "Integrated Approach to Characterisation of Coastal Plain Aquifers and Groundwater Flow Processes: Bells Creek Catchment, Southeast Queensland." Thesis, Queensland University of Technology, 2005. https://eprints.qut.edu.au/16166/1/Tim_Ezzy_Thesis.pdf.
Full textAbstract:
Low-lying coastal plains comprised of unconsolidated infill are internally complex
hydrogeological settings, due to the high level of heterogeneity in the infill material.
In order to resolve the hydrogeological processes active in these complex settings, an
integrated multi-disciplinary, geoscientific approach is required. This research
determines quantitatively, the effects of sedimentary aquifer heterogeneity on
groundwater flowpaths and groundwater processes within a heavily laterised, coastal
plain setting. The study site is the Bells Creek catchment in southeast Queensland,
Australia. The methodology developed in this study provides a new approach to
enable the determination of groundwater flowpaths and groundwater processes at
macroscale resolution within other shallow alluvial and coastal plain aquifers. The
multi-disciplinary approach utilises sedimentological, geophysical, chronological and
hydrogeological techniques (including hydrochemistry and groundwater flow
modelling) to develop a high-resolution aquifer framework, and to determine
accurately, both groundwater flowpaths and relative flow rates.
Sedimentary framework is confirmed to be the principal factor controlling the
distribution of aquifer permeability pathways in any given setting, and is therefore,
the dominant control over groundwater flow and processes. For the Bells Creek
catchment, interpretation of stratigraphic and sedimentary data allowed the
compilation of a detailed sedimentary framework. This interpretation demonstrated
that weathering of the low-lying arkose sandstone bedrock has developed thick
lateritic profiles. Within the weathering profiles, cemented, iron-rich horizons have
resisted erosion and developed raised and elongated ridges in the modern landscape,
while other clay-rich weathered layers have submitted to erosion and downgraded
around those iron-rich ridges. Consequently, alluvial deposition throughout the Late
Quaternary has been restricted to narrow, and relatively deep valleys containing sandrich
channels, and thin floodplains at shallow depth.
From a hydrogeological perspective, there is significant macroscopic aquifer
heterogeneity between fine-grained lateritic mixed clay layers, floodplain clays, ironcemented
ferricrete horizons, and permeable sand-rich alluvial aquifers. This
variability of aquifer material has created a complex subsurface arrangement of
permeability pathways. Application of Ground Penetrating Radar (GPR) in this setting enabled accurate definition of alluvial channel boundaries and the high degree
of connectedness within the channels themselves. Interpretation of a comprehensive
GPR dataset (that covered the entire catchment) allowed refinement of the
sedimentary framework previously established to develop a detailed threedimensional
aquifer framework.
Finite-difference groundwater modelling and particle tracking analysis (using
MODFLOW and MODPATH) has clearly demonstrated that the macroscopic
heterogeneity within the various aquifer materials of the plain has marked impacts on
groundwater pathways, and especially groundwater travel times. The variability
between a maximum residence time of 18 months for groundwater within the
alluvium, compared to hundreds of years for groundwater within the mixed clay
layers of the laterite, clearly demonstrates the importance of accurately defining the
spatial distribution of the various aquifer materials in a groundwater flow
investigation. In this setting, the interconnection of the narrow alluvial channels
feeding into a deeper alluvial delta has provided an effective conduit for shallow
groundwater flow. The role of the alluvial delta in discharging the bulk of fresh
groundwater from the central plain into the coastal and estuarine aquifers to the east,
is certainly critical in preventing saline intrusion from encroaching further west.
Hydrochemical and isotopic indicators have identified the dominant recharge
processes and groundwater flowpaths within the plain, and indicated that the
processes are strongly related to sub-surface permeability distributions determined in
the aquifer framework (and groundwater modelling), as well as seasonal fluctuations
in rainfall. In the northwest of the plain, sandstone hills provide a delayed and
slightly mineralized component of groundwater recharge into adjacent highly
permeable, unconfined alluvial aquifers; these aquifers also recharge directly via
precipitation. Aluminosilicate weathering in the bedrock hills and eastern peripheries
of the laterised bedrock are a source of excess Na, SiO2, and HCO3 to the alluvial
groundwater. As this groundwater flows down-gradient to the east, however, its
chemical composition evolves by sulfate reduction, silica equilibrium and ion
exchange processes into a more mature Na-Cl type.
Within the shallow coastal aquifers proximal to the eastern shoreline, sulfate
enrichment is occurring (associated with increases in Ca, HCO3, Fe and Al) resulting
in major deterioration in groundwater quality. The deterioration is produced by saline
intrusion from the adjacent estuary coupled with oxidation of sulfide materials in
shallow marine and estuarine clays. Reverses in salinity in those coastal aquifers have
been correlated with surges in fresh recharge waters from unconfined coastal dunes
and semi-confined landward alluvium, following significant rainfall events.
The multi-disciplinary methodology developed, provides an effective approach for
accurately defining the three-dimensional distribution of shallow aquifer material of
varying permeability via detailed stratigraphic interpretation and GPR analysis.
Utilising this aquifer framework, finite-difference groundwater modelling aided by
hydrogeological data and hydrochemical analysis, allows accurate determination of
groundwater flowpaths and groundwater processes. This research provides a new
hydrogeological analogue for alluvial channel aquifers within a laterised coastal plain
setting.
Key Words:
groundwater flow, aquifer heterogeneity, numerical modelling, hydrochemistry,
recharge, ground penetrating radar, coastal plain aquifers, weathering, alluvial
channels.
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Ezzy, Timothy Robert. "Integrated Approach to Characterisation of Coastal Plain Aquifers and Groundwater Flow Processes: Bells Creek Catchment, Southeast Queensland." Queensland University of Technology, 2005. http://eprints.qut.edu.au/16166/.
Full textAbstract:
Low-lying coastal plains comprised of unconsolidated infill are internally complex hydrogeological settings, due to the high level of heterogeneity in the infill material. In order to resolve the hydrogeological processes active in these complex settings, an integrated multi-disciplinary, geoscientific approach is required. This research determines quantitatively, the effects of sedimentary aquifer heterogeneity on groundwater flowpaths and groundwater processes within a heavily laterised, coastal plain setting. The study site is the Bells Creek catchment in southeast Queensland, Australia. The methodology developed in this study provides a new approach to enable the determination of groundwater flowpaths and groundwater processes at macroscale resolution within other shallow alluvial and coastal plain aquifers. The multi-disciplinary approach utilises sedimentological, geophysical, chronological and hydrogeological techniques (including hydrochemistry and groundwater flow modelling) to develop a high-resolution aquifer framework, and to determine accurately, both groundwater flowpaths and relative flow rates. Sedimentary framework is confirmed to be the principal factor controlling the distribution of aquifer permeability pathways in any given setting, and is therefore, the dominant control over groundwater flow and processes. For the Bells Creek catchment, interpretation of stratigraphic and sedimentary data allowed the compilation of a detailed sedimentary framework. This interpretation demonstrated that weathering of the low-lying arkose sandstone bedrock has developed thick lateritic profiles. Within the weathering profiles, cemented, iron-rich horizons have resisted erosion and developed raised and elongated ridges in the modern landscape, while other clay-rich weathered layers have submitted to erosion and downgraded around those iron-rich ridges. Consequently, alluvial deposition throughout the Late Quaternary has been restricted to narrow, and relatively deep valleys containing sandrich channels, and thin floodplains at shallow depth. From a hydrogeological perspective, there is significant macroscopic aquifer heterogeneity between fine-grained lateritic mixed clay layers, floodplain clays, ironcemented ferricrete horizons, and permeable sand-rich alluvial aquifers. This variability of aquifer material has created a complex subsurface arrangement of permeability pathways. Application of Ground Penetrating Radar (GPR) in this setting enabled accurate definition of alluvial channel boundaries and the high degree of connectedness within the channels themselves. Interpretation of a comprehensive GPR dataset (that covered the entire catchment) allowed refinement of the sedimentary framework previously established to develop a detailed threedimensional aquifer framework. Finite-difference groundwater modelling and particle tracking analysis (using MODFLOW and MODPATH) has clearly demonstrated that the macroscopic heterogeneity within the various aquifer materials of the plain has marked impacts on groundwater pathways, and especially groundwater travel times. The variability between a maximum residence time of 18 months for groundwater within the alluvium, compared to hundreds of years for groundwater within the mixed clay layers of the laterite, clearly demonstrates the importance of accurately defining the spatial distribution of the various aquifer materials in a groundwater flow investigation. In this setting, the interconnection of the narrow alluvial channels feeding into a deeper alluvial delta has provided an effective conduit for shallow groundwater flow. The role of the alluvial delta in discharging the bulk of fresh groundwater from the central plain into the coastal and estuarine aquifers to the east, is certainly critical in preventing saline intrusion from encroaching further west. Hydrochemical and isotopic indicators have identified the dominant recharge processes and groundwater flowpaths within the plain, and indicated that the processes are strongly related to sub-surface permeability distributions determined in the aquifer framework (and groundwater modelling), as well as seasonal fluctuations in rainfall. In the northwest of the plain, sandstone hills provide a delayed and slightly mineralized component of groundwater recharge into adjacent highly permeable, unconfined alluvial aquifers; these aquifers also recharge directly via precipitation. Aluminosilicate weathering in the bedrock hills and eastern peripheries of the laterised bedrock are a source of excess Na, SiO2, and HCO3 to the alluvial groundwater. As this groundwater flows down-gradient to the east, however, its chemical composition evolves by sulfate reduction, silica equilibrium and ion exchange processes into a more mature Na-Cl type. Within the shallow coastal aquifers proximal to the eastern shoreline, sulfate enrichment is occurring (associated with increases in Ca, HCO3, Fe and Al) resulting in major deterioration in groundwater quality. The deterioration is produced by saline intrusion from the adjacent estuary coupled with oxidation of sulfide materials in shallow marine and estuarine clays. Reverses in salinity in those coastal aquifers have been correlated with surges in fresh recharge waters from unconfined coastal dunes and semi-confined landward alluvium, following significant rainfall events. The multi-disciplinary methodology developed, provides an effective approach for accurately defining the three-dimensional distribution of shallow aquifer material of varying permeability via detailed stratigraphic interpretation and GPR analysis. Utilising this aquifer framework, finite-difference groundwater modelling aided by hydrogeological data and hydrochemical analysis, allows accurate determination of groundwater flowpaths and groundwater processes. This research provides a new hydrogeological analogue for alluvial channel aquifers within a laterised coastal plain setting. Key Words: groundwater flow, aquifer heterogeneity, numerical modelling, hydrochemistry, recharge, ground penetrating radar, coastal plain aquifers, weathering, alluvial channels.
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Sanz, Escudé Esteban. "Brackish springs in coastal aquifers and the role of calcite dissolution by mixing waters." Doctoral thesis, Universitat Politècnica de Catalunya, 2007. http://hdl.handle.net/10803/6251.
Full textAbstract:
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).
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Kennedy, Casey David. "Pilot project on groundwater dating in confined aquifers of the North Carolina Coastal Plain." NCSU, 2004. http://www.lib.ncsu.edu/theses/available/etd-04162004-145829/.
Full textAbstract:
This pilot project presents 14C groundwater ages in the Black Creek and Upper Cape Fear aquifers of the Coastal Plain of North Carolina, an evaluation of the relationship between He concentration and groundwater age, and 3H concentrations in groundwater. Groundwater samples were collected with a Bennett pump from 7 wells that lie along a trend roughly parallel to groundwater flow (at least, predevelopment groundwater flow). 14C, 13C, DIC, DOC, He, Ne, Ar, N2, O2, CO2, CH4, H2, 3H, S, Fe, Al, Mn, Si, Na+, K+, Ca2+, Mg2+, Cl-, SO4-, and NO3- were measured in all samples. Estimation of groundwater age involved inverse mass balance modeling with NETPATH to account for geochemical reactions (calcite dissolution, organic matter oxidation, and cation exchange) affecting 14C activity in groundwater, as well as a separate correction to account for loss of 14C by diffusion into contiguous aquitards. 14C groundwater ages were 580, 10700, 19100, and greater than 35300 years old at four wells in the Black Creek aquifer, and 15100, 26900, and 31100 years old at three wells in the Upper Cape Fear aquifer. These groundwater ages, together with falling heads, suggest that groundwater withdrawals in these aquifers represent a sort of ?mining.? He concentration in groundwater increased with 14C groundwater age with one exception (a sample very high in He concentration from the Upper Cape Fear where it directly overlies crystalline basement rocks). Groundwater from 6 of the wells had 3H concentrations that are consistent with the presence of young water, but it is uncertain whether the 3H in these wells is from relict drilling fluid, downward leakage along the well casings, or a more broadly distributed downward leakage.
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Hogan, Matthew Brooks Clement Thangadurai Prabhakar. "Understanding the flow and mixing dynamics of saline water discharged into coastal freshwater aquifers." Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Fall/Theses/HOGAN_MATTHEW_43.pdf.
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Abd-Elhamid, Hany Farhat. "A simulation-optimization model to study the control of seawater intrusion in coastal aquifers." Thesis, University of Exeter, 2010. http://hdl.handle.net/10036/3054.
Full textAbstract:
Groundwater contamination is a very serious problem as it leads to the depletion of water resources. Seawater intrusion is a special category of groundwater contamination that threatens the health and possibly lives of many people living in coastal areas. The focus of this work is to develop a numerical model to study seawater intrusion and its effects on groundwater quality and develop a control method to effectively control seawater intrusion. Two major approaches are used in this study: the first approach is the development of a finite element model to simulate seawater intrusion; the second is the development of a simulation-optimization model to study the control of seawater intrusion in coastal aquifers using different management scenarios. The simulation-optimization model is based on the integration of a genetic algorithm optimization technique with the transient density-dependent finite element model developed in this research. The finite element model considers the coupled flow of air and water and solute transport in saturated and unsaturated soils. The governing differential equations include two mass balance equations of water and air phases and the energy balance equation for heat transfer, together with a balance equation for miscible solute transport. The nonlinear governing differential equations are solved using the finite element method in the space domain and a finite difference scheme in the time domain. A two dimensional finite element model is developed to solve the governing equations and provide values of solute concentration, pore water pressure, pore air pressure and temperature at different points within the region at different times. The mathematical formulation and numerical implementation of the model are presented. The numerical model is validated by application to standard examples from literature followed by application to a number of case studies involving seawater intrusion problems. The results show good agreement with previous results reported in the literature. The model is then used to predict seawater intrusion for a number of real world case studies. The developed model is capable of predicting, with a good accuracy, the intrusion of seawater in coastal aquifers. In the second approach, a simulation-optimization model is developed to study the control of seawater intrusion using three management scenarios: abstraction of brackish water, recharge of fresh water and combination of abstraction and recharge. The objectives of these management scenarios include minimizing the total costs for construction and operation, minimizing salt concentrations in the aquifer and determining the optimal depths, locations and abstraction/recharge rates for the wells. Also, a new methodology is presented to control seawater intrusion in coastal aquifers. In the proposed methodology ADR (abstraction, desalination and recharge), seawater intrusion is controlled by abstracting brackish water, desalinating it using a small scale reverse osmosis plant and recharging to the aquifer. The simulation-optimization model is applied to a number of case studies. The efficiencies of three different scenarios are examined and compared. Results show that all the three scenarios could be effective in controlling seawater intrusion. However, ADR methodology can result in the lowest cost and salt concentration in aquifers and maximum movement of the transition zone towards the sea. The results also show that for the case studies considered in this work, the amount of abstracted and treated water is about three times the amount required for recharge; therefore the remaining treated water can be used directly for different proposes. The application of ADR methodology is shown to be more efficient and more practical, since it is a cost-effective method to control seawater intrusion in coastal aquifers. This technology can be used for sustainable development of water resources in coastal areas where it provides a new source of treated water. The developed method is regard as an effective tool to control seawater intrusion in coastal aquifers and can be applied in areas where there is a risk of seawater intrusion. Finally, the developed FE model is applied to study the effects of likely climate change and sea level rise on seawater intrusion in coastal aquifers. The results show that the developed model is capable of predicting the movement of the transition zone considering the effects of sea level rise and over-abstraction. The results also indicate that the change of water level in the sea side has a significant effect on the position of the transition zone especially if the effect of sea level rise is combined with the effect of increasing abstraction from the aquifer.
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Van, Der Schyff Malikah. "Using hydrogeochemistry and geophysical techniques to determine the extent of connectivity between Langerban road and Elandsfontein aquifer system, West Coast, South Africa." University of Western Cape, 2020. http://hdl.handle.net/11394/7308.
Full textAbstract:
Magister Scientiae (Integrated Water Resource Management)The heterogeneity in groundwater systems suggest that not all aquifers are connected in groundwater systems. This study is about the interaction between aquifers within groundwater system. Langebaan Road and Elandsfontein aquifers in the West Coast groundwater aquifer system were chosen as case studies. These units were chosen because the previous studies on groundwater excluded the aspect of connectivity between aquifers from methods perspective which is the focus on the current study. The second reason for the study area was the present of human activities and ecosystems which are proved to be groundwater dependents. Aquifer-aquifer interaction refers to hydraulic connection between two aquifers. The interaction is influenced by hydraulic pressure and lithology of geological strata, their integrity and spatial continuity. While factors for such connectivity are well known, appropriate techniques to establish the extent of connectivity remain poorly understood and hence the need to employ various techniques so that the extent of connectivity between the two aquifers is established. Understanding the connectivity between aquifers is important because such connectivity explains the pathways for the availability of groundwater in each aquifer unit and the associated groundwater quality in each unit that supports human activities and sustain ecological systems.
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Kalisperi, Despina. "Assessment of groundwater resources in the north-central coast of Crete, Greece using geophysical and geochemical methods." Thesis, Brunel University, 2009. http://bura.brunel.ac.uk/handle/2438/4241.
Full textAbstract:
The Geropotamos aquifer on the north‐central coast of Crete, Greece, is invaded in some places by salt water from the Aegean Sea, with impact on freshwater supplies for domestic and business uses, including agriculture. The geological setting of the study area is considered complex, as Miocene biogenic limestones, marls, clays and conglomerates crop out in the central and the western part and clastic limestones and dolomites of the Tripolis and Plattenkalk nappe (the bedrock) in the eastern part of the study area. The phyllitequartzite nappe (which forms the oldest rock of the study area) lays on the northern part of Geropotamos basin. The local tectonic regime of the study area is characterized by faults of NW‐SE and NE‐SW directions. Investigation of the aquifer using Transient ElectroMagnetic method (TEM) and Vertical Electrical Resistivity (VES) measurement technique has resulted in 1D models and 2D/3D imaging of geoelectric structures, depicting the zones of salination of groundwater in the aquifer. 1179 TEM soundings in 372 sites have been carried out in a detailed survey grid (about 200m in X and Y dimension) and 3 VES soundings were acquired in three different sites (different geological conditions). For the 2 of them, multidirectional measurements were also acquired since the structure is more complex than a 1D model that VES technique is able to model. Moreover, 3 water samplings carried out. At each sampling, samples from 22 boreholes and 2 springs were analysed and 16 chemical parameters were determined. Detailed geochemical analysis, including Piper, Durov, Ternary, Stiff, Wilcox, Dispersion diagrams and Factors controlling the groundwater quality, was accomplished showing very good results and the relationship with the geophysical methods. All data were inserted in GIS environment and Groundwater Quality Maps were produced. Furthermore, Remote Sensing application, geological mapping and hydro‐lithological data showed that the physical characteristics of geomorphology and geology are in great relationship with the chemical and geophysical properties as well. Suggestions that Miocene evaporites led to groundwater salination are unconfirmed, and seawater intrusion is the most probable cause, supported by the results of this research. It is indicated that saline intrusion is likely to occur along fractures in a fault zone through otherwise low‐permeability phyllite‐quartzite bedrock, and it is emphasized the critical role of fracture pathways in salination problems of coastal aquifers.
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Chen, Kouping. "Impact of land reclamation on hydrogeochemical processes in coastal aquifer systems : a case study in Shenzhen, China /." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/HKUTO/record/B39558940.
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Guo, Haipeng, and 郭海朋. "Groundwater movement and subsurface air flow induced by land reclamation and tidal fluctuation in coastal aquifers." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B40987735.
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Guo, Haipeng. "Groundwater movement and subsurface air flow induced by land reclamation and tidal fluctuation in coastal aquifers." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B40987735.
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李海龍 and Hailong Li. "Tide-induced periodic groundwater and air flows in coastal aquifer systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B31244452.
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Martínez, Pérez Laura. "Characterization of seawater intrusion and submarine groundwater discharge in al luvial coastal aquifers: field and laboratory approach." Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/671052.
Full textAbstract:
Seawater intrusion (SWI) causes not only salinization of coastal aquifers, but also a reduction submarine groundwater discharge (SGD) and nutrient fluxes to marine ecosystems. We have developed a small scale experimental field site to gain insights into both SWI and SGD. The site is located in a coastal alluvial aquifer at the mouth of an ephemeral stream in the Maresme coastline (Barcelona, Spain). Here, we describe our attempts for a detailed site characterization, which was based on the four pillars of hydrogeology: geology (Lithological description and geochemical analysis of core), geophysics
(borehole logs, Electrical Resistivity Tomography and thermal monitoring), hydraulics (pumping and tidal response tests) and hydrochemistry (major and minor elements, stable isotopes and Radium isotopes for SGD assessment). As it turned out, all four pillars yielded some surprise. The aquifer consists of alluvial sediments, rather than coastal plain deposits. Tidal loading, rather than hydraulic connection to the sea, appears to drive tidal response, in spite of the aquifer being unconfined.
Hydrochemistry suggests an unusually reactive layer, with all cations reflecting some mineral dissolution process, beyond the expected cation exchange. Radium increased with salinity, but the correlation was poor, partly blurred by pH, which was low in the deep portions of the aquifer. These observations were largely explained with the help of geophysics. Both borehole logs and cross-hole ERT helped in identifying silt layers that are frequent in alluvial deposits but proved to play a critical role here. The integration of the different techniques allowed to characterize the different distribution of salt- and freshgroundwater, that in fact yielded an inverse disposition to what is expected in coastal hydrogeology. To improve SGD quantification, we also characterized radium behavior within the aquifer. The recovered sediment during borehole drilling was used to perform both batch and column laboratory experiments. We performed constant salted fluid injections but we also vary the salinity (SWI and SGD simulation) to infer adsorbed Ra from its mobilization. Column experimens were later simulated using a 0D model to interpret the results. We have observed that heterogeneous flux through preferential flow paths occurs in the columns. Variations in these flow paths may explain the observed fluctuations. Such variations may also occur during the freshening and salinization experiments, but the changes in sorption are so dominant that overcome the impact of changes in porosity structure.La intrusión de agua de mar causa no solo la salinización de los acuíferos costeros, sino también una reducción en la descarga submarina de agua subterránea y en los flujos de nutrientes a los ecosistemas marinos. Para poder entender los efectos que provoca la coexistencia de ambos procesos en acuíferos costeros aluviales, hemos desarrollado un campo experimental a pequeña escala. La zona de campo está ubicada en la desembocadura de una riera efímera en la costa del Maresme (Barcelona, España), en un acuífero aluvial costero. En la presente tesis, se describen los intentos de caracterización detallada del sitio, basada en los cuatro pilares de la hidrogeología: geología (descripción litológica y análisis geoquímico de sedimentos), geofísica (registros de pozos, tomografía de resistividad eléctrica y monitoreo térmico), hidráulica (bombeo y pruebas de respuesta de marea) e hidroquímica (elementos mayores y menores, isótopos estables e isótopos de radio para la evaluación de la descarga de agua submarina). La implementación de los diferentes tipos de técnicas supuso la reconsideración de algunas de las preconcepciones establecidas a priori: la parte del acuífero analizada está constituida por sedimentos aluviales, en lugar de depósitos de llanura costera. A pesar de que el acuífero es libre, parece que la respuesta del acuífero a las mareas está causada por la carga mecánica impuesta por el mar, en lugar de evidenciar la conexión hidráulica con el mismo. La hidroquímica sugiere una capa inusualmente reactiva, con todos los cationes que reflejan algún proceso de disolución mineral, más allá del intercambio catiónico esperado. El radio aumenta con la salinidad, pero no de una manera evidente, debido a que el pH es expecialmente ácido en la zona más profunda del acuífero considerado. La integración de las diferentes técnicas permitió caracterizar la distribución diferentes masas de agua subterránea salada y dulce, que de hecho presentaban una disposición inversa a lo que se espera en zonas costeras. Tanto los registros de pozo como la tomografía eléctrica de resistividad realizada entre los pozos, ayudaron a identificar capas de limo, frecuentes en los depósitos aluviales, pero que demostraron desempeñar un papel fundamental aquí. Para mejorar la cuantificación de los flujos de SGD, también se caracterizó el comportamiento del radio dentro del acuífero. El sedimento recuperado durante la perforación de los pozos se utilizó para realizar experimentos batch y en columna en el laboratorio. Para ello, realizamos lavados consecutivos a salinidad constante, pero también variando la salinidad (simulando eventos de SWI y SGD), para inferir el Ra adsorbido a partir de su movilización. Posteriormente se modelaron los experimentos de columna utilizando un modelo 0D para interpretar los resultados. En las columnas hemos observado flujo heterogéneo a través de caminos preferentes. Las variaciones en estos caminos podrían explicar las fluctuaciones observadas en los experimentos realizados a salinidad constante. Dichas variaciones tambi én pueden ocurrir durante los experimentos de descarga de agua dulce y salinización, pero los cambios en la sorción del radio con la salinidad son tan dominantes que superan el impacto de los cambios en la estructura de la porosidad.
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Del, Val Alonso Laura. "Advancing in the characterization of coastal aquifers : a multimethodological approach based on fiber optics distributed temperature sensing." Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/672709.
Full textAbstract:
Detailed characterization of coastal aquifers is essential for proper management of coastal groundwater resources, and coastal areas in general. Still, there is a general lack of systematic monitoring and detailed characterization of the seawater intrusion (SWI). Part of this lack is related to the limitations of traditional tools and methodologies. In this thesis we aim to provide new approaches and methodologies for the characterization of coastal aquifers, and in particular for the SWI dynamics.
At a first stage, three relatively new monitoring systems were tested to characterise the SWI: Cross-Hole Electric Resistivity Tomography (CHERT), Time Laps Induction Logging (TLIL) and Fiber Optics Distribute Temperature Sensing (FO-DTS). We did that by installing the fiber optic cable and CHERT electrodes outside the borehole casing, and allowing to deploy additional tools through the borehole. This multipurpose approach allowed to deploy multiple tools in parallel, decreasing installation costs and improving characterization by combining complementary information. In fact the combination of the three methods allowed to discern different levels of SWI and multiple dynamics.
From these techniques we were interested in further exploring the use of FO-DTS. However, before that we had to study the use of temperature as a tracer of the SWI. Although the fundamentals of heat transport in groundwater are well known, the use of temperature as a natural tracer for SWI is limited. Numerical modelling was used to explore the potential of temperature for studying SWI dynamics at field scale. The results were used to propose a framework for the interpretation of thermal data at the SWI. The framework gives guidelines to identify preferential paths of the SWI, flow direction and even roughly estimate groundwater flux rates, in multilayered coastal aquifers. We concluded that temperature has a potential for SWI motorisation largely unexplored.
Based on the promising results from the modelling exercise, we tested the FO-DTS for monitoring of the SWI continuously during one year and a half. This is commonly called a passive application of the FO-DTS. We were able to identify different levels of the SWI, flow directions and short and long term dynamics. The interpretation confirmed the framework proposed previously.
FO-DTS can also be used actively, thus by heating the fiber optic cable and measuring the evolution of the heating and cooling of the cable. An active FO-DTS application was designed to measure groundwater fluxes and thermal properties of the media. The obtained flux rates are in agreement with independent estimates. Further research is needed to adapt the analytical approach used for the interpretation of the heating curves to account for the effect of the heat storage in the cable material and surrounding elements. Still, the method shows great potential for its application in quantifying discharge fluxes towards the sea, and in general to quantify groundwater fluxes in porous media.
Additionally, traditional methods for the interpretation of pumping testing data were revised. A new approach to extract drawdowns from measured heads during pumping in coastal aquifers is proposed. This approach ease and reinforce the use of this traditional hydraulic characterization technique in coastal aquifers.
Many questions remain unanswered, and many others arise from the exploration of these new and traditional techniques. The wide range of information that can be obtained with FO-DTS well deserves more research, in order to facilitate its general use. The revision of traditional methods, such as the classic pumping test, or well-known theories, like the use of temperature as a natural tracer, may be necessary for their application in coastal aquifers. Still, the set of methods proposed in this document expands the tools and the resolution available to characterise the SWI, contributing to expand the available knowledge about coastal aquifers.Una caracterización detallada de los acuíferos costeros es esencial para la gestión de los recursos hídricos costeros, y en general de las zonas costeras. A pesar de su importancia, en general no existe un monitoreo sistemático de la zona de intrusión salina (SWI). Parte de esta carencia se debe a limitaciones en las herramientas y metodologías tradicionalmente empleadas. El objetivo de esta tesis es proporcionar nuevos enfoques y herramientas para la caracterización de los acuíferos costeros, y en particular de la SWI. Inicialmente, tres sistemas de monitoreo fueron testados en campo para caracterizar la SWI: Cross-Hole Electric Resistivity Tomography (CHERT), Time Laps Induction Logging (TLIL) and Fiber Optics Distribute Temperature Sensing (FO-DTS). Para poder operar las tres herramientas en paralelo, el cable de fibra óptica y los electrodos de la CHERT se instalaron entre el entubado y el sedimento. De este modo redujimos costes de instalación y mejoramos el proceso de caracterización con la combinación de información complementarias. De hecho, la combinación de las tres permitió´ detectar diferentes niveles y dinámicas de la SWI. De estas tres técnicas, nos hemos querido concentrar en explorar el uso de la FO-DTS para el monitoreo de acuíferos costeros. Sin embargo, antes de todo tuvimos que estudiar el uso de la temperatura como trazador de la SWI. A pesar de que los fundamentos del transporte de calor en agua subterránea están establecidos, el uso de la temperatura como trazador natural de la SWI es limitado. Para estudiar la SWI se han hecho dos modelos numéricos. De los resultados obtenidos surge un posible marco teórico para la interpretación de datos térmicos de la SWI. Usando la distribución vertical de temperaturas podríamos diferenciar niveles de SWI, la dirección de flujo, e incluso aproximar la velocidad del mismo. Con estos resultados llegamos a la conclusión de que el uso de la temperatura para el seguimiento de la SWI tiene todavía un gran potencial sin explorar. Basándonos en estos resultados testamos la FO-DTS para el monitoreo de la SWI en nuestro emplazamiento experimental durante un año y medio. Los datos obtenidos con la FO_DTS permitieron identificar la respuesta de la SWI a eventos a distintas escala temporales. De este modo, los datos confirmaron las conclusiones obtenidas con los modelos numéricos. La FO-DTS puede ser usada también de forma activa, es decir, calentando el cable de fibra óptica y midiendo el calentamiento y posterior enfriamiento. En la tesis proponemos una metodología activa de la FO-DTS para medir la velocidad del flujo de agua subterránea y estimar las propiedades térmicas del medio teniendo en cuenta el efecto del almacenamiento de calor en el cable. Los valores obtenidos concuerdan con estimaciones independientes. El método puede ser aplicado tanto para la caracterización del flujo de descarga al mar en acuíferos costeros, como en cualquier medio poroso saturado. Finalmente, se revisa la interpretación de los tradicionales ensayos de bombeo. De esta revisión surge proponer una alternativa para separar los descensos de los niveles medidos durante el bombeo, y filtrar el ruido. Esta metodología facilita y refuerza el uso de este tipo de ensayos en acuíferos costeros. La FO-DTS proporciona diferentes tipos de información sobre la SWI, lo que bien justifica profundizar en su estudio para poder generalizar su uso. Por otro lado, la revisión de métodos tradicionales, como los ensayos de bombeo, o de metodologías establecidas, como el uso de la temperatura como trazador, podrían beneficiarse de cierta revisión para adaptarlas a las condiciones especificas de los acuíferos costeros. En cualquier caso, el conjunto de métodos presentados en este documento expande las herramientas y resolución disponibles para la caracterización de la SWI en acuíferos costeros.
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Mokoena, Portia Leah. "Novel approach of using Hydrogeochemistry, Hydrogeologic and Hydrostratigraphic techniques in evaluating coastal aquifers in Heuningnes catchment, South Africa." University of the Western Cape, 2019. http://hdl.handle.net/11394/7960.
Full textAbstract:
Philosophiae Doctor - PhDThe increasing population in search for better social and economic development in coastal areas puts groundwater resources under pressure because of the high fresh water demand for domestic and agriculture use. Seawater intrusion is widely recognised as major concern in coastal aquifers across the globe and is influenced by multiple factors, being climate variation which is projected to adjust recharge of groundwater because of decreased precipitation patterns and to increase sea level variations and over-abstraction due to high freshwater demand as a result of increased population and agricultural practices, thereby inducing salinization in groundwater. The coastal aquifer in Heuningnes Catchment is not exempted from these issues and salinization is a major concern in the area affecting groundwater quality. In Heuningnes Catchment and South Africa in general there is limited knowledge on the application of integrated approach for assessing groundwater quality especially salinization mechanism in coastal aquifers. The main goal of this research is to test and demonstrate the viability of using joint interpretation approach of geophysics, geochemical and geological information to investigate groundwater quality in coastal aquifers thus improving on the understanding of using such approach. This work offers the initial thorough assessment of groundwater quality and understanding of the salinity sources and hydro-geochemical processes governing the chemical composition of groundwater in the region. Thus provide advice on the fitness of this water for consumption and irrigation purposes. Thirty-two groundwater samples were collected and analysed for (Mg2+), (Ca2+), (Na+), (K+), (Cl-), (SO42), (HCO3-), (pH, TDS and EC). To estimate fitness of groundwater quality for consumption purposes WHO (2011) and SANS241 guideline were used and for irrigation utilization the water quality indices (EC), (Na+%), (SAR), (RSC), (KR) and (MR) were used. Statistics approaches were employed to ascertain the primary geochemical processes governing the chemical composition of groundwater in the research region. Lastly, the spatial distribution maps were created by means of ArcGIS. Electrical resistivity method was used to map the extent of saline distribution within the subsurface. The findings of this study revealed that groundwater in the region is alkaline type and TDS, EC, Na+, Cl- exceeded WHO and SANS241 guidelines for consumption water. The geophysical investigation revealed that the sandy clay/clayey sand, fine sand and fractured sandstone units make up the coastal aquifer systems within the area. Further, revealed that these aquifers were saturated with fresh, saline or brackish water depending on the subsurface layer. The presence of saline and brackish was confirmed by the chemical results which indicated a Na+-Cl- type as a dominant water type. Also classifying groundwater based on EC and TDS supports these findings. The foremost hydro-geochemical processes that controls the salinity and quality of groundwater in the study region as indicated by Gibbs plot are water-rock interaction followed by evaporation process. Furthermore, analysis of hydrochemical data also proposes that weathering of silicate minerals, ion-exchange and dissolution of carbonate minerals amended ion concentration in groundwater thus influencing salinisation in certain parts of the study region. Also assessment of ionic-ratios displays influences of marine sprays as well as seawater, on the chemical structure of groundwater within the Heuningnes Catchment aquifer. Valuation of groundwater quality and its fitness for ingestion and irrigation purposes, the results indicated that shallow groundwater in the area is not suitable for any use; however, groundwater from deeper boreholes was found fresh and appropriate for irrigation and household purposes. Findings of this study indicated that salinity is the major groundwater quality issue for this area and that monitoring of groundwater quality in Heuningnes Catchment is limited. The absence of consistent monitoring program on groundwater quality makes it difficult to ascertain long term trends on groundwater quality parameters. Therefore, this study emphasizes the need for regular groundwater quality monitoring to assess the trends of these parameters in order to make an informed decision as to what can be done for mitigation purposes.
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O???Shea, Bethany Megan School of Biological Earth & Environmental Science UNSW. "Delineating the source, geochemical sinks and aqueous mobilisation processes of naturally occurring arsenic in a coastal sandy aquifer." Awarded by:University of New South Wales. School of Biological, Earth and Environmental Science, 2006. http://handle.unsw.edu.au/1959.4/25179.
Full textAbstract:
Elevated arsenic concentrations have been reported in a drinking water and irrigation-supply aquifer of Stuarts Point, New South Wales, Australia. Arsenic occurrence in such aquifers is potentially a major issue due to their common use for high yield domestic and irrigation water supplies. Ten multi-level piezometers were installed to depths of approximately 30 m in the sand and clay aquifer. Sediment samples were collected at specific depths during drilling and analysed for chemical and mineralogical composition, grain size characteristics, potential for arsenic release from solid phase and detailed microscopic features. From this data, a full geomorphic reconstruction allowed the determination of source provenance for the aquifer sediments. The model proposed herein provides evidence that the bulk of the aquifer was deposited under intermittent fluvial and estuarine conditions; and that all sediments derive from the regional arsenicmineralised hinterland. More than 200 groundwater samples were collected and analysed for over 50 variables. The heterogeneity of the aquifer sediments causes redox stratification to occur, which in turn governs arsenic mobility in the groundwater. The bulk of the aquifer is composed of fluvial sand deposits undergoing reductive dissolution of iron oxides. Arsenic adsorbed to iron oxide minerals is released during dissolution but re-adsorbs to other iron oxides present in this part of the aquifer. The deeper, more reducing fluvial sand and estuarine clay groundwaters have undergone complete reductive dissolution of iron oxides resulting in the subsequent mobilisation of arsenic into groundwater. Some of this arsenic has been incorporated into iron sulfide mineral precipitates, forming current arsenian pyrite sinks within the aquifer. The extraction of groundwater from the aquifer for irrigation and drinking water supply induces seawater intrusion of arsenic-rich estuarine water, bringing further dissolved arsenic into the aquifer. A greater understanding of the source, sinks and mobilisation of arsenic in this aquifer contributes to our broad understanding of arsenic in the environment; and allows aquifer specific management procedures and research recommendations to be made. Any coastal or unconsolidated aquifer that has sediments derived from mineralised provenances should consider monitoring for arsenic, and other potentially toxic trace elements, in their groundwater systems.
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Pope, Jason Philip. "Characterization and modeling of land subsidence due to groundwater withdrawals from the confined aquifers of the Virginia Coastal Plain." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/42812.
Full textAbstract:
Measurement and analysis of aquifer-system compaction have been used to
characterize aquifer and confining unit properties when other techniques such as flow
modeling have been ineffective at adequately quantifying storage properties or matching
historical water levels in environments experiencing land subsidence. In the southeastern
Coastal Plain of Virginia, high-sensitivity borehole pipe extensometers were used to
measure 24.2 mm of total compaction at Franklin from 1979 to 1995 (an average of 1.5
mm/yr) and 50.2 mm of total compaction at Suffolk from 1982 to 1995 (an average of 3.7
mm/yr). Analysis of the extensometer data reveals that the small rates of aquifer-system
compaction appear to be correlated with withdrawals of water from confined aquifers.
One-dimensional vertical compaction modeling indicates that the measured compaction
is the result of nonrecoverable hydrodynamic consolidation of the fine-grained confining
units and interbeds as well as recoverable compaction and expansion of coarse-grained
aquifer units. The modeling results also provide useful information about specific storage
and vertical hydraulic conductivity of individual hydrogeologic units. The results of this
study enhance the understanding of the complex Coastal Plain aquifer system and will be
useful in future modeling and management of ground water in this region.Master of Science
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Gámez, Torrent Desiré. "Sequence Stratigraphy as a tool for water resources management in alluvial coastal aquifers: application to the Llobregat delta (Barcelona, Spain)." Doctoral thesis, Universitat Politècnica de Catalunya, 2007. http://hdl.handle.net/10803/6255.
Full textAbstract:
Most coastal aquifers undergo seawater intrusion. Mitigating this risk depends on a sound knowledge of flow mechanisms, well located and constructed wells, an effective management, suitable policies and the desire to conserve the aquifer. To this end, a comprehensive geological model is essential. The single most important question that the geological model should address is the degree and nature of the connection of the aquifer to the sea. Differences in the connection explain why apparently similar coastal aquifers display very different salinitzation behavior. Some aquifers salinize with moderate pumping (eg. Tordera and Llobregat deltas) whereas others sustain large extractions with lower vulnerability to seawater intrusion (eg. Ter delta). However, the characterization of such a connection is not easy given the lack of onshore-offshore geological mapping potential pathways for seawater contamination. This thesis is focused on sequence stratigraphy, which is necessary to understand the onshore-offshore aquifer connection, thus modifying the classical hydrogeological conceptual models. The methodology of sequence stratigraphy offers a perspective of delta architecture based on geological controls and processes. Sequence stratigraphic concepts are used in Western Mediterranean deltas in addition to local factors, such as subsidence, uplift and the rate of sediment supply to account for differences in Pleistocene stratigraphic patterns and aquifer preservation. These local factors exert an influence over the shape, slope and thickness of aquifers. Together with the width of the continental shelf, the presence of submarine canyons, faults and thin prodelta layers conditions vulnerability to seawater intrusion.
The Quaternary Mediterranean shelf is characterized by high-frequency depositional sequences mainly composed of large-scale regressive wedges with poor or poorly preserved transgressive to highstand intervals. Although the Llobregat delta is an anomaly, it serves as a paradigm of deltaic architecture because of its well preserved transgressive and highstand intervals. The well preserved coarse transgressive deposits are important from hydrogeological point of view. They act as aquifers with high lateral continuity from onshore to offshore providing paths for seawater intrusion.
The excellent preservation in the Llobregat delta may be a consequence of Quaternary growth faults, which caused high accommodation space, limiting the action of wave and storm events. The identification of different seismic units and deformation features along the coast makes it possible to distinguish two main morpho-structural sectors. These sectors can be influenced by tectonic movements, which may be intensified by sediment supply changes.
Detailed sedimentological, age and paleontological (foraminifera and ostracods) data display a cyclic vertical pattern of facies, including a high degree of reworked sediments. Available ages together with high sediment preservation due to constant subsidence and sediment supply during sea level rises allow us to establish a chronostratigraphic framework. The most significant and widespread erosion were interpreted as occurring during gradual sea-level falls with a frequency of 100 Kyr. glacial-interglacial cycles. However, most of the regressive deposits display complex internal architectures, which suggest the imprint of higher-frequency cycles.
The stacking pattern of the modern Holocene delta is controlled by changes in the relative sea-level and in the sediment supply. Paleofloods frequencies controlled by climatic changes and intensified by anthropic activity caused an important progradational pulses in the Llobregat delta and the channel switching with the rapid abandonment of the delta lobes.
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Mizuno, Jun. "Numerical Analyses of Potential Losses of Freshwater Resources in Coastal Aquifers Caused by Global Climate Change Using an Appropriate Boundary Condition." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1213328150.
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Pechstein, Armin [Verfasser], Sabine [Gutachter] Attinger, and Nadim K. [Gutachter] Copty. "Innovative techniques for the characterization and interpretation of coastal aquifers : pumping test interpretation by means of the drawdown derivative to estimate aquifer heterogeneity / Armin Pechstein ; Gutachter: Sabine Attinger, Nadim K. Copty." Jena : Friedrich-Schiller-Universität Jena, 2017. http://d-nb.info/1177603160/34.
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Kowlesser, Akshay. "Sustainable Aquifer Management in Small Island Developing States : A case study of Mauritius." Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-227316.
Full textAbstract:
Small Island Developing States (SIDS) are amongst the most vulnerable states in the world. They are subject to a number of stresses including economical, climatic and spatial restraints. This thesis investigates the effects that certain critical ‘stresses’ will have on the groundwater reserves of SIDS. Mauritius was chosen as the case study for this project because of three main reasons, which were that 1) islands of the Indian Ocean are the least studied compared to the pacific and Caribbean islands, 2) there is no actual groundwater model for the aquifers of Mauritius and finally 3) information and background knowledge was more accessible to the author. Two critical aquifers of Mauritius were chosen according to their respective vulnerability (extraction rates of groundwater, geological features, and rainfall patterns), Aquifers II and V. The aquifers were calibrated using data that was published by the Mauritian local authorities and through an extensive literature review. Aquifer II and Aquifer V were modelled using the software ModelMUSE and a steady state model (with a time series of 100 years) was used to calibrate the models using limited data that was obtained through the literature review. Aquifer V was successfully modelled while Aquifer II gave inconsistent results. A transient model using four scenarios inspired by the IPCC scenario analysis was used to investigate the salt water intrusion as well as the piezometric levels in both aquifers. The scenarios (run for a period of 100 years, i.e. until 2100) were of varying degrees of severity and included the main drivers of change that were believed to affect the groundwater consumption of Mauritius. The attributes that were targeted in this thesis were: economy, demography, technology and climate. These were then converted into quantifies inputs that were used in the model to assess the migration of the saltwater/freshwater interface in the aquifers. Scenario 4 which involved low recharge rate of the aquifer, high sea level rise, low GDP growth and increasing population subjected the aquifer to a reduced water table, and consequential sea water intrusion of the order 1.5 km across the cross section analysed. Scenario 3, which consisted of investment in green technology, increase in recharge of the aquifers on the other hand gave the more optimistic results with the salt water - fresh water interface moving seawards. Scenario 4 rendered unusable around 50 % of the wells in the aquifer while Scenario 3 on the other had the effects of increasing the freshwater lens of the Aquifer V. Measures such as sustainable urban drainage systems, managed aquifer recharge and Seepcat (a method which involves placing a series of pipes around coastal aquifers to prevent the intrusion of salt water) were recommended to decrease the salt water intrusion risk and eventually increase the fresh water lens of the island on various spatial and time scales. It is suggested that the coarse groundwater model developed for Aquifer V of Mauritius be refined and applied to different aquifers of the island. Moreover it is also recommended for future work that discontinuities in the geology be integrated in the groundwater model. A more detailed and nuanced water balance is also recommended to get more accurate initial conditions for the model. This thesis, by providing a coarse model to tackle the impending challenges that await Mauritius, can support a more sustainable water management of the country.Small Island Developing States (SIDS), små önationer under utveckling, är bland de mest sårbara staterna i världen. De är utsatta för ett antal stressfaktorer inklusive ekonomiska, klimatrelaterade och rumsliga restriktioner. Detta examensarbete undersöker effekterna av några kritiska stressfaktorer på grundvattenreserverna i dessa önationer. Mauritius valdes som fallstudie för detta projekt på grund av tre huvudsakliga orsaker. Dessa var att öar i Indiska Oceanen är de minst studerade jämfört med atlantiska och karibiska öar, att det inte finns någon riktig grundvattenmodell för akvifererna på Mauritius och slutligen att information och bakgrundskunskap var mer lättåtkomligt för författaren. Två kritiska akviferer på Mauritius valdes utifrån deras respektive sårbarheter (uttagshastighet av grundvatten, geologiska egenskaper och nederbördsmönster). Baserat på detta valdes Akvifer II och Akvifer V. Akvifererna kalibrerades med hjälp av data publicerat av mauritiska lokala myndigheter och genom en omfattande litteraturstudie. Akvifer II och Akvifer V modellerades i programmet ModelMUSE och en steady state-modell (med en tidsserie på 100 år) användes för att kalibrera modellerna med hjälp av begränsad data som erhölls under litteraturstudien. Inmatningsvärdena erhölls från vattenresursenheten på Mauritius, från vilka genomsnittliga värden över en tidsperiod om 15 år togs fram och användes som begynnelsevillkor för steady state-modellen. Akvifer V kalibrerades med framgång medan Akvifer II gav inkonsekventa resultat. Detta hänfördes till de stora skillnaderna i topografin i Akvifer II, vilka bidrog till att fel uppstod under uträkningen. En tidsberoende modell med fyra scenarios inspirerade av FN:s klimatpanels scenarioanalys användes för att undersöka saltvatteninträngningen samt grundvattennivån i båda akvifererna. Scenarierna (körda över en period om 100 år, d.v.s. till 2100) var av varierande viktighetsgrad och inkluderade de främsta drivkrafterna som ansågs påverka Mauritius grundvattenförbrukning. De attribut som fokuserades på i denna avhandling var: ekonomi, demografi, teknik och klimat. Dessa omvandlades sedan till indata som användes i modellen för att bedöma migrationen av saltvatten/sötvattengränsen i akvifererna. Scenario 4 som innebar liten grundvattenbildning i akviferen, hög havsnivåstigning, låg BNP-tillväxt och ökande befolkning utsatte akviferen för en reducerad vattennivå, och påföljande havsvatteninträngning av ordningen 1,5 km över den analyserade tvärsektionen. Scenario 3 gav å andra sidan mer optimistiska resultat då saltvatten/sötvattengränsen rörde sig mot havet. Scenario 4 medförde att ungefär 50 % av brunnarna i akviferen blev oanvändbara. Åtgärder såsom hållbara stadsdräneringssystem, kontrollerad grundvattenbildning och Seepcat (en metod som innebär att man placerar en serie rör runt kustområden för att förhindra saltvattenintrång) rekommenderas för att minska saltvatteninträngningen och så småningom öka öns färskvattenlins på olika rumsliga och tidsrelaterade skalor. Det föreslås att den grova grundvattenmodellen som utvecklats för Akvifer V i Mauritius förfinas och appliceras på olika akviferer på ön. Därtill rekommenderas att diskontinuiteter i geologin integreras i grundvattenmodellen i framtida arbete. Genom att applicera modellen kan viktig information användas för en hållbar vattenförvaltning på Mauritius i framtiden.
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Smith, James V. S. School of Biological Earth & Environmental Sciences UNSW. "Inorganic hydrogeochemistry, hydrogeology and geology of the Stuarts Point aquifer system : a process analysis of the natural occurrences of enriched As(III) and As(V) in an Australian coastal groundwater system." Awarded by:University of New South Wales. School of Biological, Earth and Environmental Sciences, 2005. http://handle.unsw.edu.au/1959.4/22349.
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Arsenic (As) in groundwater systems is a problem in many parts of the world owing to ever-increasing extraction of groundwater resources to meet the needs of growing populations. Surprisingly, the occurrence of elevated As concentrations in coastal sandy aquifers has only recently been published as a result of this research. Sandy aquifers are commonly used as a clean and reliable source of water for domestic, agricultural and industrial needs due to their high recharge rates and the filtering capacity of sands. Water quality monitoring in Australian sandy aquifers is usually limited to a small suite of major elements and salinity measurements to determine the quality of groundwater and to identify any potential problems from seawater intrusion as a result of over extraction. Minor and trace elements, particularly toxic elements, have largely been ignored in regular monitoring programs. Prompted by an emerging pattern of human health problems in a community reliant on groundwater, hydrogeochemical investigations of the Stuarts Point coastal sand aquifer, on the North Coast of New South Wales, Australia, identified elevated As concentrations of up to 337 ????g/L in the catchment's Pleistocene barrier sands. These concentrations are well in excess of the World Health Organisation and the Australian National Health and Medical Research Council water quality criteria of 10 and 7 ????g/L respectively. From research into the Stuarts Point geology, geochemistry, geomorphology, hydrogeology and hydrogeochemistry, and with the assistance of environmental isotopes, the spatial distribution, occurrence and mobilisation processes of As were determined. The presence and distribution of elevated As concentrations in the regional coastal aquifer system are sporadic and involve a series of complex hydrogeochemical processes. No single hydrogeochemical process can describe the release of As from solid phase to groundwater system on the regional scale. Processes of competitive exchange with PO43- and HCO3-, reductive dissolution of Fe oxyhydroxides and arsenical pyrite oxidation, though not forming dominant correlations, are still evident and influence As chemistry at this scale. Detailed investigations of the hydrogeochemistry on the vertical scale have identified two main processes as causing As to be released and mobilised. The first process is associated with the oxidation of arsenical pyrite in Acid Sulphate Soils and metal hydrolysis reactions which mobilise As in the acidic environment. In the absence of dissolved oxygen (DO), NO3- acts as the oxyanion facilitating arsenical pyrite oxidation and releasing As into solution. The second process that mobilises As from the sediments is the liberation of As from metal-oxyhydroxides in the carbon-rich environment, where HCO3- originates from the dissolution of shell material in the Pleistocene barrier sands. The marine influenced depositional history and geomorphology of the aquifer provide opportunities for As to become incorporated into the aquifers matrix in a variety of mineral forms, which is an occurrence not considered to be unique to the Stuarts Point catchment. The findings presented here are amongst the first detailed studies of naturally occurring As in an Australian groundwater system as well as in the Pleistocene coastal sand aquifer environment. The understanding of As accumulation and mobilisation identified as a result of this research emphasises the need for potential As occurrences in similar groundwater systems in other coastal environments in Australia, and globally, to be considered.
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von, Bahr Maximilian, and Bergström Ida Gomez. "Investigation of the origin of salt in coastal aquifers and assessment of metals in the aquatic environment : River Drin and River Vjosa, Albania." Thesis, KTH, Vatten- och miljöteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-235421.
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The preservation of freshwater aquifers is one important task of managing natural resources today. Intrusion of saltwater from the sea into the groundwater might occur in coastal-near areas and can affect the freshwater quality negatively. One such risk area is the Adriatic coast line of Albania, a country predominantly rich in freshwater resources due to the numerous rivers flowing from the mountains in the east towards the sea. The coastal areas are mainly used for agricultural activities were groundwater is an important resource for irrigation purposes. This study was therefore partly conducted in Albania where samples of groundwater and river waters were collected from the river deltas of Drin and Vjosa in order to investigate the origin of the salt and to assess the bioavailable metal concentrations of nickel and zinc. Both on-site tests and off-site tests, in laboratories, were conducted. In the laboratory, the samples were analysed for oxygen and deuterium isotope data. The results were used to assess the origin of the oxygen content as the method of investigating the origin of the salt uses the oxygen isotope as a tracer. Anion and cation concentrations were analysed as well as the concentrations of metals. These were used as input data to Visual Minteq, a model used to calculate the metal speciation of waters, and a Biotic Ligand Model used to calculate the bioavailable concentrations and the HC5 concentrations. The isotope analysis yielded results similar to previous studies conducted in the nearby area indicating that the salt does not have oceanic origin but meteorological. The bioavailable concentrations were in most sample sites lower than the calculated HC5 concentrations indicating that there is a sufficient buffering system present even though there are several mining activities upstream of the sample sites that could have affected the water quality. This study concludes that the origin of salt is of meteoric origin and not from seawater intrusion. The bioavailable concentrations do not pose a threat as the concentrations are under the HC5 concentrations for all sites but one. In order to deepen the understanding and knowledge of the water qualities in these areas, future studies should focus on a continuous measuring period lasting for example over the whole year minimizing any seasonal variations of the sampled data. Other methods such as geophysical measures could also contribute to a wider analysis of the groundwater condition.Grundvatten är en av de viktigaste naturresurserna vilket innebär att för att säkerställa en långvarig försörjning krävs en god förvaltning av befintliga akvifärer. I kustnära områden kan intrång av saltvatten från havet till grundvattnet påverka sötvattenkvaliteten negativt. Ett sådant riskområde är den Adriatiska kustlinjen i Albanien, ett land som är övervägande rikt på sötvattenresurser tack vare de många floder som rinner från bergen i öst mot havet i väst. Kustområdena används huvudsakligen för jordbruksverksamhet, där grundvatten är en viktig resurs vid bevattning. Denna studie genomfördes därför delvis i Albanien där prov av grundvatten och flodvatten hämtades från Drins och Vjosas floddeltan för att undersöka saltets ursprung och för att bedöma de biotillgängliga metalkoncentrationerna av nickel och zink. Vattenprover togs på ett urval av platser och testades direkt för omgivningsberoende parametrar samt analyserades vidare i laboratorier. I laboratoriet analyserades proverna med avseende på fördelning av syre- och deuteriumisotoper. Resultaten användes för att bedöma syreinnehållets ursprung, eftersom metoden för att undersöka saltets ursprung använder syreisotopen som spårämne. Anjon- och katjonkoncentrationer analyserades såväl som koncentrationerna av metaller. Dessa användes som inmatningsdata till Visual Minteq, en modell som används för att beräkna metallsammansättningen i vatten och en Biotic ligand model som användes för att beräkna de biotillgängliga koncentrationerna samt HC5-koncentrationerna. Isotopanalysen gav resultat som liknar tidigare studier utförda i det närliggande området vilket indikerar att saltet inte har oceaniskt ursprung utan meteorologiskt. De biotillgängliga koncentrationerna av nickel och zink var i de flesta fall lägre än de beräknade HC5-koncentrationerna, vilket indikerar att det finns ett buffertsystem, trots att gruvaktiviteter uppströms provplatserna skulle kunna ha påverkat vattenkvaliteten negativt. Studien slutsats är att saltet i grundvattnet och flodvattnet är av meteoriskt ursprung och inte ett resultat av saltvatteninträngning från det Adriatiska havet. De biotillgängliga halterna av nickel och zink understiger HC5 halterna i samtliga fall utom ett. För att fördjupa förståelsen och kunskapen om vattenkvaliteten i dessa områden bör framtida studier fokusera på en kontinuerlig mätperiod som till exempel sträcker sig över hela året vilket skulle minimera eventuella säsongsvariationer av insamlad data. Andra metoder så som geofysiska mätningar kan också bidra till en bredare analys av tillståndet i grundvattnet.
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陳扣平 and Kouping Chen. "Impact of land reclamation on hydrogeochemical processes in coastal aquifer systems: a case study in Shenzhen,China." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B39558940.
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Fatema, Suraiya [Verfasser], Christoph [Akademischer Betreuer] Schüth, Anwar Akademischer Betreuer] Zahid, Matthias [Akademischer Betreuer] [Hinderer, and Wilhelm [Akademischer Betreuer] Urban. "Vulnerability assessment of the coastal aquifers in the Cox’s Bazar area, Bangladesh using hydrochemical tools and the GALDIT model / Suraiya Fatema ; Christoph Schüth, Anwar Zahid, Matthias Hinderer, Wilhelm Urban." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2020. http://d-nb.info/1211088529/34.
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Fatema, Suraiya [Verfasser], Christoph [Akademischer Betreuer] Schüth, Anwar [Akademischer Betreuer] Zahid, Matthias [Akademischer Betreuer] Hinderer, and Wilhelm [Akademischer Betreuer] Urban. "Vulnerability assessment of the coastal aquifers in the Cox’s Bazar area, Bangladesh using hydrochemical tools and the GALDIT model / Suraiya Fatema ; Christoph Schüth, Anwar Zahid, Matthias Hinderer, Wilhelm Urban." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2020. http://d-nb.info/1211088529/34.
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Lu, Chunhui. "Mixing in complex coastal hydrogeologic systems." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39600.
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The mixing zone developed at freshwater-seawater interface is one of the most important features in complex coastal hydrogeologic systems, which controls subsurface flow and reactive transport dynamics. Freshwater-seawater mixing-zone development is influenced by many physical and chemical processes, such as characteristics of geologic formation, hydrodynamic fluctuations of groundwater and seawater levels, fluid-rock interactions, and others. Wide mixing zones have been found in many coastal aquifers all over the world. However, the mechanisms responsible for wide mixing zones are not well understood. In this thesis, two hypotheses were proposed to explain wide mixing zones in coastal aquifers: (1) kinetic mass transfer coupled with transient conditions, which create the movement of the mixing zone, may widen mixing zones; and (2) aquifer stratification may widen the mixing zone.
The hypotheses were tested by both multiscale numerical simulations and laboratory experiments. Numerical simulations were based on a variable-density groundwater model by varying mass transfer parameters, including immobile porosity, mobile porosity, and mass transfer coefficient, and the hydraulic conductivity contrast between aquifer layers. Laboratory experiments were conducted in a quasi-two-dimensional tank, where real beach sands were installed and foodstuff dyes were used to visualize the development of freshwater-seawater mixing zone. Major conclusions included (1) the mixing zone can be significantly widened when the mass transfer timescale and the period of transient boundary is comparable due to the nonequilibrium mass transfer effects; and (2) a thick mixing zone occurs in low-permeability layer when it overlays upon a fast flow layer. These results not only improve the understanding of the dynamics of mixing-zone development and its associated geochemical processes in coastal aquifers, but also identify hydrogeologic conditions for the model of sharp-interface approximation to be valid.
In addition to better understanding the mechanisms and dynamics of mixing zone, this thesis also investigates cost-effective management of coastal groundwater resources. To protect and conserve limited water recourses in coastal regions, interest in aquifer storage and recovery (ASR) has been growing in recent years. ASR is a promising strategy for water resources management and has been widely used in many contaminated and saline aquifers. However, its performance may be significantly constrained by mass transfer effects due to the mobilization of solutes initially residing in immobile domains. Better understanding of kinetic mass transfer effects on ASR is needed in order to aid the decision-making process. A numerical model is developed to simulate ASR performance by combining the convergent and divergent dispersion models with a first-order mass transfer model. By analyzing the concentration history at the pumping well, we obtain simple and effective relationships for investigating ASR efficiency under various mass transfer parameters, including capacity ratio and mass transfer timescales, and operational parameters. Based on such relationships, one can conveniently determine whether a site with mass transfer limitations is appropriate or not for ASR and how many ASR cycles are required for achieving a positive recovery efficiency (RE).
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Beddows, Patricia Anne. "Groundwater hydrology of a coastal conduit carbonate aquifer : Caribbean coast of the YucataÌn Peninsula, MeÌxico." Thesis, University of Bristol, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398776.
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