Dissertations / Theses on the topic 'Deep groundwater'

Magister Scientiae - MSc (Earth Science)<br>The improvement in hydraulic fracturing techniques resulted in the exploitation of natural gas associated with low-permeability of organic-rich shale formations in the United States. South Africa has prospective shale gas reserves associated with the marine black shales of the lower Ecca Group's Whitehill Formation in the Karoo Basin. The marine shales development in the Karoo Basin is centred on the diversifying the primary energy mix. The Karoo is a semi-arid region whose communities solely dependent on groundwater for their development. Groundwater concerns in the Karoo Basin regarding shale gas development include water resource degradation by stray gas migration and also flowback or produced water from deeper formations. The main aim of this study was to improve understanding on the risks posed by shale gas extraction on shallow aquifers in order to propose mitigation measures for groundwater protection in the main Karoo Basin. This study employed a conceptual qualitative design to understand aquifer behaviour from the informants' perspective. The perspectives in the study area were informed by two pre-existing conceptual models used as schools of thought in order to create a site specific conceptual model for the current study. Also, the study also made use of Groundwater Model Multi Criteria Analysis, a risk based assessment to explain potential subsurface risks to groundwater resources. A site specific conceptual model of local, intermediate and deep groundwater flow systems was developed based on the two models to investigate shallow and deep aquifer systems and their interactions which might lead to potential shallow aquifer contamination. The study found shallow aquifer systems exist at depths <300m, such aquifers were not locally recharged, but recharged by hilltops containing large number of vertical fractures. These aquifer systems are associated with dolerite intrusion. Due to thermal effects, dykes caused fracturing of adjacent rocks such as sandstone/ mudstone significant increase in yields of adjacent boreholes. The intermediate aquifer systems are mostly associated with fractures, with deep burial fracture systems with fault systems. These systems are normally expressed to the surface as springs to an order of 100-1000 meters. These saline aquifer systems are poorly understood and unknown if they are widespread.<br>2019-04-30

Quantifying recharge to the mountain block from headwater catchments in snowmelt dominated upland mountainous regions is an important aspect of hydrologic studies. This study contributes to understanding of the interaction between surface water, soil water and deep groundwater flow in headwater catchments. A novel approach was developed for estimating the bedrock hydraulic conductivity of a regional-scale fractured bedrock aquifer using discrete fracture network (DFN) modeling. The methodology was tested in the mountainous Okanagan Basin, British Columbia, Canada. Discrete fractures were mapped in outcrops, and larger-scale fracture zones (corresponding to lineaments) were mapped from orthophotos and LANDSAT imagery. Outcrop fracture data were used to generate DFN models for estimating hydraulic conductivity for the fractured matrix (Km). The mountain block hydraulic conductivity (Kmb) was estimated using larger-scale DFN models. Simulated Km and Kmb values range from 10⁻⁸ to 10⁻⁷ m/s, are consistent with estimates from regional modeling studies, and are greatest in a N-S direction, coinciding with the main strike direction of Okanagan Valley Fault Zone. Kmb values also decrease away from the fault, consistent with the decrease in lineament density. Simulated hydraulic conductivity values also compare well with those estimated from pumping tests. The estimates of Kmb were then used to represent the deep bedrock in a coupled surface water - groundwater model using MIKE SHE for the Upper Penticton Creek 241 headwater catchment in the Okanagan Basin. Although highly uncertain due to parameter uncertainty and calibration error, recharge to deep groundwater was ~4% of the annual water budget. An specified outward flux from the catchment boundary, representing ~6% of annual water budget, did not significantly impact streamflow calibration, indicating that such deep groundwater losses from the catchment can be accommodated in a model. This outflow may contribute to cross-catchment flow and, ultimately, to groundwater inflow to lower elevation catchments in the mountain block. The modeling exercise is one of the first in catchment hydrology modeling within steep mountainous terrain in which the lower boundary of the model is not treated as impermeable, and in which recharge to the deep bedrock and discharge to the surrounding mountain block were estimated.

The UK has a large and growing inventory of higher activity radioactive waste awaiting safe long term disposal. The international consensus is to dispose of this radioactive and toxic waste within a deep geological repository, situated 200-1,000 metres beneath the ground surface. The deep geological disposal facility is designed to be a series of engineered and natural barriers. Groundwater forms an integral component of the natural barrier because it 1) controls the flux of reactive components towards the engineered repository, and 2) forms one of the primary transport mechanism through which released radionuclides can be transported away from the repository. The timescale of protection provided by the natural barrier exceeds those provided by the engineered barriers. Knowledge of the regional hydrogeology is a vital step towards predicting the long term performance of any potential repository site. Topically, a UK government decision in 2017 to re-open a nation-wide repository location search has now created a renewed mandate for site exploration. This research aims to determine the regional groundwater characteristics of three UK settings, selected to be hydrogeologically distinct, in order to determine which, if any, offers natural long term hydrogeological containment potential. The settings selected for analysis include Sellafield in West Cumbria, the Tynwald Basin within the East Irish Sea Basin, and Thetford within East Anglia. Site selection is based on diverse groundwater characteristics, and on previous research suggesting potential hydrogeological suitability at these locations. This research is novel in that it provides, for the first time, a direct comparison between the characteristics and qualities of different regional groundwater settings to contain and isolate radioactive waste, based on UK site specific data. Large and detailed numerical models for the three sites, covering areas of 30 km length by 2- 4 km depth have been developed using the open source finite element code 'OpenGeoSys'. The models couple the physical processes of liquid flow and heat transport, in order to replicate regional scale groundwater flow patterns. Models are calibrated to measured rock properties, and predict groundwater behaviour 10,000 years into the future. Uncertain parameter ranges of lithological and fault permeabilities, and peak repository temperatures are tested to determine the possible range of groundwater outcomes. Geochemical retention is assessed separately and validated using the finite difference modelling software 'GoldSim'. Worst case groundwater characteristics for containment and isolation at each site are compared to an 'ideal' benchmark far-field hydrogeological outflow scenario, and scored accordingly using a newly proposed method of assessment. Results show that the Tynwald Basin offers the best potential of the three sites for natural radionuclide containment, performing between 3.5 and 4 times better than Sellafield, and between 1.7 and 4 times better than Thetford. The Tynwald Basin is characterised by 1) long and deep groundwater pathways, and 2) slow local and regional groundwater movement. Furthermore, the Tynwald Basin is located at a feasible tunnelling distance from the coast, adjacent to the UK's current nuclear stockpile at Sellafield, and thus could provide a simple solution to the current waste legacy problem. Results from the Sellafield model indicate that this location cannot be considered to exhibit beneficial characteristics due to short and predictable groundwater pathways which ascend, from the repository, towards surface aquifers. Finally, Thetford within East Anglia has never been drilled to depth so that sub-surface rock properties of basement, located beneath layered sediments, are based on evidence inferred from around the UK. Uncertainties in rock properties has produced a wide range of groundwater characteristic possibilities, with results indicting prospective performance to range from 0 to 2.4 times better than Sellafield. As such, the hydrogeological suitability to host a potential deep geological repository is promising when modelled with most-likely permeability values, but cannot be accurately determined at present. Consideration of decaying heat from the heat emitting waste packages at the three sites reveal that the natural groundwater flow patterns can be distorted up to as much as 7 km away from the theoretical repository, depending on setting. This thus changes the use of the term 'near-field' for safety assessments, as implying an area within the immediate vicinity of the excavated repository site. The overarching findings from this research are that: 1) some locations have greater long term radionuclide containment and isolation prospectivity than others, due to variable quality far-field geological and hydrogeological characteristics; 2) the effect of radiogenic heat emission on the natural groundwater flow pattern is dependent on the site specific geological and hydrogeological characteristics, and therefore so is the area defined as the 'near-field'; and 3) a simple method of site comparison is possible for regional groundwater system under steadystate conditions. Recommendations are for scoping models of regional groundwater settings to be used as a comparative tool, such as undertaken as part of this research, to differentiate between potential sites at an early stage of the current UK site selection programme.

<p>The Table Mountain Group (TMG) Aquifer is the second largest aquifer system in South Africa, after dolomites. This aquifer has the potential to be a signinficant source of water for the people of the Western Cape. The occurrence of hot water springs in the TMG in relation with the main geological fault systems in SOuth Africa shows that deep flow systmes do exist. Little is known about these deep aquifer systems in South Africa (i.e. flow mechanisms). To close the above-mentioned knowledge gap, this study was initiated. The current study gave a review of some of the aspects that needs to be considered when distinguishing deep groundwater from shallow groundwater.</p>

Deep, fresh groundwater (typically >150 m below ground) provides a vital source of drinking water across the Indo-Gangetic Basin, and is being increasingly developed. Current understanding of the sustainability and vulnerability of this resource is largely based on model estimates and there is a paucity of in-situ observations with which to inform current debate on their vulnerability and on-going exploitation. This thesis applies a suite of environmental tracers (CFCs, SF6, stable isotopes, hydrochemistry, micro-organics) to enable, for the first time, a detailed assessment of age-depth and water quality profiles in three case study areas across the Indo-Gangetic Basin. Specifically, the thesis assesses depth profiles (0 to 360 m) of: i) mean residence times (MRT), ii) sources of recharge/contaminants and iii) key water quality parameters (e.g. arsenic, fluoride, and salinity). These tracers are also used to explore evidence of local by-pass flow at borehole-scales and the vertical migration of younger groundwater. Tracers reveal the general resilience of the Bengal Aquifer System, and highlight the relative vulnerability of the upper Indus and mid Ganges aquifer systems to the vertical ingress of shallow groundwater as well as the ingress of anthropogenic contaminants to depth within these aquifer systems. MRT distributions at depth in the upper Indus and mid-Ganges are comparable, between 20 to 60 years, and contrast sharply with MRTs in the BAS that are found to be 5,000 to 10,000 years. Pumped wells in all three aquifer systems show evidence of rapid by-pass flow to deep boreholes. In the upper Indus and mid Ganges aquifer systems, evidence is presented of local, vertical, pumping-induced migration of shallow groundwater. In order to ensure the protection of deep groundwater supplies in the Indo-Gangetic Basin for future generations, it is argued that continued exploitation of deep groundwater requires long-term monitoring to enable early detection of water quality deterioration.

Master of Science<br>Department of Geology<br>Saugata Datta<br>Domestic and irrigation well water quality in south-central Kansas is threatened by multiple sources of contamination including CO₂-EOR activities, evaporite dissolution and oilfield brine release. This research identifies potential groundwater flow paths for contaminant migration in a concentrated area mixed with oil, injection, irrigation and domestic wells. Groundwater (GW) sampling took place before and after CO₂ injections into the Mississippian in to assess temporal changes in water quality in a ~2 mile radius around injection well KGS 2-32. Samples were analyzed for stable isotopes, rare earth elements (REE), major and trace ions, dissolved organic carbon (DOC) with a select few analyzed for dissolved CO₂ and hydrocarbons. Results of major ion chemistry reveal an evaporite control on geochemistry in wells screened within the paleoterrace as opposed to the incised valley. Bedrock channeling due to erosional scouring of the paleovalley is speculated to have led to secondary porosity thereby increasing GW flow. Similar stable isotopic and Br/Cl mass ratios between SW-3, Shepherd and Zehr indicate water is similarly sourced; lower total dissolved solids within incised valley could result from dilution from infiltration through overburden sediments. Br/Cl, SO₄/Cl, Na/Cl and (Ca+Mg)/Na ratios indicate Shepherd, Zehr and SW-3 are possibly impacted by a recent salt plume movement through this portion of the shallow aquifer. An increase in total dissolved solids and Mg/Ca ratios with temperatures less than 25°C over a 25 to 200 ft. depth interval into the Permian Shale of the uplands could have resulted from increasing calcitization and reduction in effective porosity. Dissolved REEs showed most domestic and surface waters contain similar signatures, indicating similarly sourced water. Additionally, there was no CO₂ leakage found within the sampling timeframe and a future leaked plume may be impeded by decreasing porosity from current secondary mineralization processes taking place in the Permian Shale.

Passive capillary wick samplers (PCAPs) are primarily used to sample water from the vadose zone. PCAPs use fiberglass wicks to form a hanging water column that exerts suction on the surrounding soil. Although PCAPs have been used to estimate soil water flux, the accuracy with which PCAPs can estimate flux comes into question due to over/undersampling caused by this applied flux. I used numerical models to explore the effects of a PCAP on flow through the vadose zone. Specifically, I used a two-dimensional axisymmetric flow model of a PCAP embedded in a medium based on HYDRUS. Both steady-state and transient conditions were simulated through the application of various precipitation rates and periods across several soil textures. In this study, I examine soil hydraulic properties, across the soil texture triangle, subject to a range of precipitation events. Results show that the PCAP does over/underestimate water flux. The degree of error is quantified by defining a capture efficiency, which is the ratio of the flux into the plate and the flux that would occur at the same depth with no PCAP present. Higher fluxes and longer time periods resulted in increased convergence of flux into the PCAP, while lower fluxes and shorter durations resulted in divergence of flux from the PCAP. The goal of the study is to understand the behavior of PCAPs under different conditions and to use that knowledge to interpret field measurements in the Jemez River Basin Critical Zone Observatory.

The interaction between earthquakes and crustal fluids is a very complex topic due to several mechanisms that are involved and which influence each other. Some phenomena, like the alterations of springs discharge rates and fluid flow, liquefaction and changing of the water levels in phreatic wells are largely documented in the literature, but their explanation is not yet fully clear. Furthermore, these phenomena can greatly change with the rock type, the earthquake magnitude and the observation distance from the fault. Within a distance of a few fault lengths from the epicenter, an earthquake can alter both the regional stress field and the hydraulic properties of the rocks, influencing the underground fluid distribution. In this thesis, I apply the numerical simulator TOUGH2 to represent the changes in water level of some wells after the ML 5.9 earthquake that took place in Italy in 2012. The model shows that the wells response to the seismic event can be represented imposing a static stress change and highlights the role of the soil stratigraphy. This zone is also well known for localized methane seepages associated with anomalous soil temperatures. I simulate the process and draw some conclusions on the nature of this phenomenon and on the possible interactions with the local seismicity. Finally, I study the earthquake-fluid interaction from the opposite point of view: looking at how fluids can promote seismicity. I present the results obtained by coupling the TOUGH2 geothermal simulator with a stochastic seed model of seismicity. The coupled simulation could capture the main characteristics of the seismicity induced by the fluid injection in a seismically active area.<br>L'interazione tra terremoti e fluidi crostali è un argomento molto complesso per via dei numerosi meccanismi che sono coinvolti e che si influenzano a vicenda. Alcuni fenomeni, come l'alterazione delle sorgenti e del flusso di fluidi, la liquefazione e il cambiamento del livello d'acqua nei pozzi freatici, sono largamente documentati in letteratura, tuttavia la loro spiegazione non è ancora del tutto chiara. Oltretutto, questi fenomeni possono cambiare sensibilmente in base al tipo di roccia, alla magnitudo del terremoto e alla distanza dalla faglia. Entro una distanza di poche lunghezze di faglia dall'epicentro, un terremoto può modificare sia il campo di sforzo regionale che le proprietà idrauliche della roccia, influenzando la distribuzione dei fluidi nel sottosuolo. In questa tesi utilizzo il simulatore numerico TOUGH2 per rappresentare la variazione del livello d'acqua di alcuni pozzi successivamente al terremoto di magnitudo ML5.9 che avvenne in Italia nel 2012. Il modello mostra che la risposta dei pozzi al terremoto può essere rappresentata imponendo una variazione di stress statico ed evidenzia l'importanza della stratigrafia del sottosuolo. Questa zona è ben nota anche per emissioni di metano localizzate, associate a riscaldamenti anomali del sottosuolo. In questa tesi presento delle simulazioni per rappresentare questo processo e traggo alcune conclusioni circa la natura di questo fenomeno e sulle sue possibili interazioni con la sismicità locale. In ultimo, studio la relazione tra fluidi e terremoto dal punto di vista opposto: come I fluidi possono facilitare la sismicità. Presento i risultati ottenuti accoppiando il simulatore geotermico TOUGH2 con un modello sismico, stocastico, a “seed”. La simulazione accoppiata è in grado di catturare le caratteristiche principali della sismicità indotta dall'iniezione di fluidi in un'area sismicamente attiva.

The interaction between earthquakes and crustal fluids is a very complex topic due to several mechanisms that are involved and which influence each other. Some phenomena, like the alterations of springs discharge rates and fluid flow, liquefaction and changing of the water levels in phreatic wells are largely documented in the literature, but their explanation is not yet fully clear. Furthermore, these phenomena can greatly change with the rock type, the earthquake magnitude and the observation distance from the fault. Within a distance of a few fault lengths from the epicenter, an earthquake can alter both the regional stress field and the hydraulic properties of the rocks, influencing the underground fluid distribution. In this thesis, I apply the numerical simulator TOUGH2 to represent the changes in water level of some wells after the ML 5.9 earthquake that took place in Italy in 2012. The model shows that the wells response to the seismic event can be represented imposing a static stress change and highlights the role of the soil stratigraphy. This zone is also well known for localized methane seepages associated with anomalous soil temperatures. I simulate the process and draw some conclusions on the nature of this phenomenon and on the possible interactions with the local seismicity. Finally, I study the earthquake-fluid interaction from the opposite point of view: looking at how fluids can promote seismicity. I present the results obtained by coupling the TOUGH2 geothermal simulator with a stochastic seed model of seismicity. The coupled simulation could capture the main characteristics of the seismicity induced by the fluid injection in a seismically active area.<br>L'interazione tra terremoti e fluidi crostali è un argomento molto complesso per via dei numerosi meccanismi che sono coinvolti e che si influenzano a vicenda. Alcuni fenomeni, come l'alterazione delle sorgenti e del flusso di fluidi, la liquefazione e il cambiamento del livello d'acqua nei pozzi freatici, sono largamente documentati in letteratura, tuttavia la loro spiegazione non è ancora del tutto chiara. Oltretutto, questi fenomeni possono cambiare sensibilmente in base al tipo di roccia, alla magnitudo del terremoto e alla distanza dalla faglia. Entro una distanza di poche lunghezze di faglia dall'epicentro, un terremoto può modificare sia il campo di sforzo regionale che le proprietà idrauliche della roccia, influenzando la distribuzione dei fluidi nel sottosuolo. In questa tesi utilizzo il simulatore numerico TOUGH2 per rappresentare la variazione del livello d'acqua di alcuni pozzi successivamente al terremoto di magnitudo ML5.9 che avvenne in Italia nel 2012. Il modello mostra che la risposta dei pozzi al terremoto può essere rappresentata imponendo una variazione di stress statico ed evidenzia l'importanza della stratigrafia del sottosuolo. Questa zona è ben nota anche per emissioni di metano localizzate, associate a riscaldamenti anomali del sottosuolo. In questa tesi presento delle simulazioni per rappresentare questo processo e traggo alcune conclusioni circa la natura di questo fenomeno e sulle sue possibili interazioni con la sismicità locale. In ultimo, studio la relazione tra fluidi e terremoto dal punto di vista opposto: come I fluidi possono facilitare la sismicità. Presento i risultati ottenuti accoppiando il simulatore geotermico TOUGH2 con un modello sismico, stocastico, a “seed”. La simulazione accoppiata è in grado di catturare le caratteristiche principali della sismicità indotta dall'iniezione di fluidi in un'area sismicamente attiva.

Thesis (Ph.D.)--Indiana University, Dept. of Geological Sciences, 2004.<br>Title from PDF t.p. (viewed Dec. 1, 2008). Source: Dissertation Abstracts International, Volume: 66-01, Section: B, page: 0161. Chair: Lisa M. Pratt.

Dissolved noble gas geochemistry provides insight on origin of saline groundwaters in two Canadian Shield mines, the Lupin and Con mines in Northern Canada. Within the Con major ion and isotope geochemistry indicate groundwaters from the deepest levels sampled remain relatively undisturbed by mining. Estimates of residence time for the Con mine brines, based on radiogenically produced helium and argon, indicate a Paleozoic age, consistent with recharge during the presence of Devonian seawater in this region. This is largely corroborated by krypton and xenon concentrations which reflect concentrated brine that has equilibrated with air before infiltration. Saline waters in the Lupin mine have an age of at least 130 Ma. At the Lupin mine, neon, krypton and xenon concentrations indicate degassing has occurred, likely caused by depressurization during mining along the V1 fault/fracture zone.

Des simulations précises du niveau des eaux souterraines (GWL) sont indispensables pour générer les reconstructions et les projections servant à analyser les tendances et la variabilité historiques et futures des eaux souterraines à long terme. Dans cette thèse, nous étudions l'utilisation d'approches d'apprentissage profond (DL) pour les simulations, reconstructions et projections du niveau des eaux souterraines, en mettant l'accent sur les questions liées à la représentation de la variabilité à basse fréquence interannuelle à décennale, et en utilisant divers produits de réanalyses climatiques et sorties de GCM. Une approche de pré-traitement par ondelettes assistant les modèles DL a été développée, en particulier à partir de transformée en ondelettes discrète à chevauchement maximal (MODWT) en une étape de décomposition les signaux d'entrée. Les modèles récurrents à mémoire long- et court- terme (LSTM) et leurs développements plus récents (unité récurrente à porte GRU et LSTM bidirectionnels BiLSTM) ont été plus spécifiquement utilisés et évalués, pour développer des approches d’apprentissage à station unique et à stations multiples. Les résultats de l'approche à station unique ont indiqué que les modèles GRU assistés par MODWT permettaient d'extraire des informations à basse fréquence et surpassaient considérablement les modèles « simples » (i.e. sans pré-traitement) dans la simulation des GWL, en particulier pour les GWL de type inertiel. La méthode SHAP a été utilisée pour appréhender l’interprétabilité des résultats des modèles et le fonctionnement des modèles eux-mêmes, mettant ainsi notamment en évidence les caractéristiques d'entrée les plus importantes. Pour les reconstructions GWL à long terme, les modèles DL ont été construits en utilisant les ensembles de données de réanalyse climatique ERA5 et ERA20C du centre européen de prévisions météorologiques à moyen terme (ECMWF), permettant des reconstructions jusqu'en 1940 et 1900, respectivement. Ces modèles basés ont pu capturer avec succès la variabilité multidécennale dans tous les niveaux de nappe reconstruits, un enjeu important en contexte de changement climatique dans la mesure où la variabilité multidécennale peut fortement interférer avec les effets du changement climatique. Plusieurs approches d’apprentissage multi-stations et de clustering ont été utilisées pour les simulations GWL à grande échelle, intégrant des variables climatiques dynamiques et des caractéristiques statiques des aquifères. Les modèles spécifiquement entraînés sur différents types de GWL, regroupés sur la base de leurs propriétés spectrales, ont obtenu des résultats significativement meilleurs que ceux entraînés sur l'ensemble des données. Enfin, un modèle GRU multi-stations entraîné pour chaque type de GWL avec un prétraitement MODWT avec correction des effets de bord (BC-MODWT) a été utilisé pour générer des projections jusqu'en 2100. Les changements futurs indiquent des tendances à la baisse des niveaux et de la variabilité des eaux souterraines, s'intensifiant de SSP2-4.5 à SSP5-8.5, malgré des niveaux des eaux souterraines projetés plus élevés en moyenne par rapport à la période historique dans tous les scénarios. Nous expliquons ce résultat apparemment contre-intuitif par le fait que les niveaux projetés sont systématiquement bien plus élevés en début de période future (jusqu’à ~2050) par rapport à la période historique. Nos résultats indiquent enfin que la variabilité des aquifères de type annuel a augmenté pour tous les scénarios d’émission<br>Accurate groundwater level (GWL) simulations facilitate reconstructions and projections for analysing historical and future groundwater trends and variability at the decadal scale. In this thesis, we investigate the use of deep learning (DL) approaches for GWL simulations, reconstructions, and projections, with a focus on capturing low-frequency variability and leveraging climate reanalysis and GCM model outputs. A wavelet-assisted DL framework was developed, using the Maximal Overlap Discrete Wavelet Transform (MODWT) as a pre-processing step to decompose input signals. We specifically evaluated advanced DL models, including Long Short-Term Memory (LSTM), Gated Recurrent Unit (GRU), and Bidirectional LSTM (BiLSTM), for single-station and multi-station approaches. The single station approach results indicated that MODWT-assisted GRU models allowed for extracting low-frequency information and significantly outperformed standalone models in simulating GWLs, particularly for inertial-type GWL. The Shapley Additive Explanations (SHAP) technique was used to interpret model outputs and highlight important input features. For long-term GWL reconstructions, DL models were trained on ERA5 and ERA20C climate reanalysis datasets, enabling reconstructions up to 1900 and 1940, respectively. These DL-based models were able to capture multi-decadal variability in all reconstructed GWLs. Several multi-station training approaches and clustering were used for large-scale GWL simulations, incorporating dynamic climatic variables and static aquifer characteristics. Models specifically trained on different GWL types, clustered by spectral properties, performed significantly better than those trained on the whole dataset. Finally, A multi-station GRU model trained for each GWL type with boundary-corrected MODWT (BC-MODWT) pre-processing was used to generate projections until 2100. Future changes show decreasing trends in groundwater levels and variability, intensifying from SSP2-4.5 to SSP5-8.5, despite projected groundwater levels being higher on average compared to the historical period in all scenarios. We explain this seemingly counter-intuitive result by the fact that projected levels are systematically much higher at the beginning of the future period (up to ~2050) compared to the historical period. Finally, our results indicate that the variability of annual-type aquifers has increased for all emission scenarios

This study evaluated the impacts of shallow and deep open drains on groundwater levels and drain performance under varying climate scenarios and irrigation application rates. The MIKE SHE model used for this study is an advanced and fully spatially distributed hydrological model. Three drain depths, climates and irrigation application rates were considered. The drains depths included 0, 1 and 2 m deep drains. The annual rainfall and meteorological data were collected from study area from 1976 to 2004 and analysed to identify the typical wet, average and dry years within the record. Similarly three irrigation application rates included 0, 10 and 16 ML/ha-annum. All together twenty seven scenarios (3 drains depths, 3 climates and 3 irrigation application rates) were simulated. The observed soil physical and hydrological data were used to calibrate and validate the model. Mean square error (R[superscript]2) of the simulated and observed water table data varied from 0.7 to 0.87. Once validated the MIKE SHE model was used to evaluate the effectiveness of 1 and 2 metre deep drains. The simulated water table depth, unsaturated zone deficit, exchange between unsaturated and saturated zones, drain outflow and overland flow were used to analyse their performance. The modeling results showed that the waterlogging was extensive and prolonged during winter months under the no drainage and no irrigation scenario. In the wet climate scenario, the duration of water logging was longer than in the average climate scenario during the winter months. In the dry climate scenario no waterlogging occurred during the high rainfall period. The water table reached soil surface during the winter season in the case of wet and average climate. For the dry climate, the water table was about 0.9 metres below soil surface during winter.One and 2 metre deep drains lowered the water table up to 0.9 and 1.8 metres in winter for the wet climate when there was no irrigation application. One metre deep drains proved effective in controlling water table during wet and average climate without application of irrigation water. One metre deep drains were more effective in controlling waterlogging a in wet, average and dry years when the irrigation application rate was 10 ML/ha-annum. With 16 ML/ha-annum irrigation application, 1 metre deep drains did not perform as efficiently as 2 metre deep drains in controlling the water table and waterlogging. In the dry climate scenario, without irrigation application, 1 metre deep drains were not required as there was not enough flux from rainfall and irrigation to raise the water table and create waterlogging risks. Two metre deep drains lowered the water table to greater depths in the wet, average and dry climate scenarios respectively when no irrigation was applied. They managed water table better in wet and average climate with 10 and 16 ML/ha-annum irrigation application rate. Again in the dry climate, without irrigation application 2 metre deep drains were not required as there was a minimal risk of waterlogging. The recharge to the groundwater table in the no drainage case was far greater than for the 1 and 2 metre deep drainage scenarios. The recharge was higher in case of 1 metre deep drains than 2 metre deep drains in wet and average climate during winter season.There was no recharge to ground water with 1 and 2 metre deep drains under the dry climate scenarios and summer season without irrigation application as there was not enough water to move from the ground surface to the unsaturated and saturated zones. When 10 ML/ha-annum irrigation rate was applied during wet, average and dry climate respectively, 1 metre deep drains proved enough drainage to manage the recharge into the groundwater table with a dry climate. For the wet and average climate scenarios, given a 10 ML/ha-annum irrigation application rate, 2 metre deep drains managed recharge better than 1 metre deep drains. Two metres deep drains with a 10 ML/ha-annum irrigation application rate led to excessive drainage of water from the saturated zone in the dry climate scenario. Two metres deep drains managed recharge better with a 16 ML/ha-annum irrigation application rate in the wet and average climate scenarios than the 1 metre deep drains. Two metres deep drains again led to excessive drainage of water from the saturated zone in dry climate. In brief, 1 metre deep drains performed efficiently in the wet and average climate scenarios with and without a 10 ML/ha-annum irrigation application rate. One metre deep drains are not required for the dry climate scenario. Two metre deep drains performed efficiently in the wet and average climate scenarios with 16 ML/ha-annum irrigation application rate. Two metre deep drains are not required for the dry climate scenario.

This study evaluated the impacts of shallow and deep open drains on groundwater levels and drain performance under varying climate scenarios and irrigation application rates. The MIKE SHE model used for this study is an advanced and fully spatially distributed hydrological model. Three drain depths, climates and irrigation application rates were considered. The drains depths included 0, 1 and 2 m deep drains. The annual rainfall and meteorological data were collected from study area from 1976 to 2004 and analysed to identify the typical wet, average and dry years within the record. Similarly three irrigation application rates included 0, 10 and 16 ML/ha-annum. All together twenty seven scenarios (3 drains depths, 3 climates and 3 irrigation application rates) were simulated. The observed soil physical and hydrological data were used to calibrate and validate the model. Mean square error (R[superscript]2) of the simulated and observed water table data varied from 0.7 to 0.87. Once validated the MIKE SHE model was used to evaluate the effectiveness of 1 and 2 metre deep drains. The simulated water table depth, unsaturated zone deficit, exchange between unsaturated and saturated zones, drain outflow and overland flow were used to analyse their performance. The modeling results showed that the waterlogging was extensive and prolonged during winter months under the no drainage and no irrigation scenario. In the wet climate scenario, the duration of water logging was longer than in the average climate scenario during the winter months. In the dry climate scenario no waterlogging occurred during the high rainfall period. The water table reached soil surface during the winter season in the case of wet and average climate. For the dry climate, the water table was about 0.9 metres below soil surface during winter.<br>One and 2 metre deep drains lowered the water table up to 0.9 and 1.8 metres in winter for the wet climate when there was no irrigation application. One metre deep drains proved effective in controlling water table during wet and average climate without application of irrigation water. One metre deep drains were more effective in controlling waterlogging a in wet, average and dry years when the irrigation application rate was 10 ML/ha-annum. With 16 ML/ha-annum irrigation application, 1 metre deep drains did not perform as efficiently as 2 metre deep drains in controlling the water table and waterlogging. In the dry climate scenario, without irrigation application, 1 metre deep drains were not required as there was not enough flux from rainfall and irrigation to raise the water table and create waterlogging risks. Two metre deep drains lowered the water table to greater depths in the wet, average and dry climate scenarios respectively when no irrigation was applied. They managed water table better in wet and average climate with 10 and 16 ML/ha-annum irrigation application rate. Again in the dry climate, without irrigation application 2 metre deep drains were not required as there was a minimal risk of waterlogging. The recharge to the groundwater table in the no drainage case was far greater than for the 1 and 2 metre deep drainage scenarios. The recharge was higher in case of 1 metre deep drains than 2 metre deep drains in wet and average climate during winter season.<br>There was no recharge to ground water with 1 and 2 metre deep drains under the dry climate scenarios and summer season without irrigation application as there was not enough water to move from the ground surface to the unsaturated and saturated zones. When 10 ML/ha-annum irrigation rate was applied during wet, average and dry climate respectively, 1 metre deep drains proved enough drainage to manage the recharge into the groundwater table with a dry climate. For the wet and average climate scenarios, given a 10 ML/ha-annum irrigation application rate, 2 metre deep drains managed recharge better than 1 metre deep drains. Two metres deep drains with a 10 ML/ha-annum irrigation application rate led to excessive drainage of water from the saturated zone in the dry climate scenario. Two metres deep drains managed recharge better with a 16 ML/ha-annum irrigation application rate in the wet and average climate scenarios than the 1 metre deep drains. Two metres deep drains again led to excessive drainage of water from the saturated zone in dry climate. In brief, 1 metre deep drains performed efficiently in the wet and average climate scenarios with and without a 10 ML/ha-annum irrigation application rate. One metre deep drains are not required for the dry climate scenario. Two metre deep drains performed efficiently in the wet and average climate scenarios with 16 ML/ha-annum irrigation application rate. Two metre deep drains are not required for the dry climate scenario.

Les études isotopiques couplées avec des informations géothermiques peuvent constituer des outils pertinents pour l’exploration des eaux souterraines en tant que ressources en eau potable ou géothermiques. Ce travail combine les deux approches, isotopes de l’environnement et radioactifs associés à des données de température sur des aquifères profonds, dans l’objectif d’enrichir et d’améliorer la connaissance des mécanismes de recharge (Bassin d’Aquitaine, France) ainsi que des mécanismes de recharge et du potentiel géothermique (Bassin Crétacé de Bohème, République Tchèque).Les isotopes stables (18O, 2H, 13C) utilisés conjointement avec des radioisotopes (14C, 3H) sont utilisés pour estimer l’époque de la recharge ainsi que les conditions climatiques qui prévalaient lors de l’infiltration depuis la fin de Pléistocène jusqu’à nos jours. Définir le type de recharge et les conditions d’écoulement est nécessaire pour parvenir à modéliser de façon satisfaisante et fiable les grands systèmes aquifères profonds. Trois types de recharge ont été définis en Europe - (i) continue, (ii) interrompue lors du dernier maximum glaciaire (LGM) – un troisième type (iii) correspond à des situations particulières de recharge.Les conditions géographiques et climatiques très différentes rencontrées en France et en République Tchèque ont engendrées une importante hétérogénéité des conditions et processus de recharge. Le sud de la France, avec un climat relativement doux depuis les derniers 40 ka BP, n’a pas enregistré d’interruption de la recharge. Le temps de séjour des eaux souterraines en Bohème est estimé à environ 11 ka BP au maximum. Cependant, l’appauvrissement des teneurs en isotopes stables enregistré suggère une recharge liée à la fonte de la calotte glaciaire Nord Européenne après le dernier maximum glaciaire (LGM), autour de 18-20 ka BP. Des investigations sur les isotopes du carbone minéral dissous des eaux souterraines du bassin de Bohème ont montrées d’importantes interactions avec différentes sources de carbone qui ont été identifiées.Pour le site d’étude tchèque, les informations apportées par la géochimie ont été complétées par des données géothermiques afin d’améliorer la connaissance des flux et de la dynamique des eaux souterraines. Plus d’une centaine d’enregistrements diagraphiques de température ont été utilisés pour estimer le gradient géothermique. Plusieurs phénomènes viennent perturber le gradient géothermique de la région. Les flux d’eau souterraine verticaux et les variations lithologiques et topographiques sont à l’origine d’une distribution complexe du flux de chaleur, étant majoritairement conditionné par les écoulements souterraines. Les discontinuités peu profondes et les nombreux pointements volcaniques exercent aussi une influence importante sur l’écoulement souterrain et donc aussi sur le potentiel géothermique du réservoir. Les investigations sur la géothermie ont ainsi fourni des informations fondamentales sur le potentiel géothermique mais aussi sur les conditions d’écoulement des eaux souterraines. La prise en compte de ces informations s’avère nécessaire afin de proposer des modèles mathématiques d’écoulement réalistes<br>Isotopic investigations combined with geothermal applications represent powerful tools for the exploration of groundwater potential as a drinking or geothermal resource. This Ph.D. thesis combines both approaches, environmental and radioactive isotopes together with temperature data in deep aquifers, in order to enrich and update the knowledge concerning the aquifer recharge processes in the Aquitaine Basin (France) and the aquifer recharge processes and geothermal potential in the Bohemian Cretaceous Basin (Czech Republic).Stable isotopes (18O, 2H, 13C) combined with radioisotope data (14C, 3H) are used to estimate the recharge timing and climatic conditions prevailing during the infiltration from the Late Pleistocene up to modern time. The character of groundwater recharge and regime are necessary to generate relevant source data for the accurate modelling of complex groundwater systems. Three groups of groundwater recharge types can be distinguished throughout Europe – (i) continuous recharge and (ii) interrupted recharge during Last Glacial Maximum and (iii) a group corresponding to particular recharge conditions.The contrasted geographic and climate conditions at both study sites in France and Czech Republic have entailed a great heterogeneity of the recharge conditions and processes. Southern France, with generally mild climatic conditions during the last 40 ka BP, did not experienced considerable hiatus in groundwater recharge. The residence time of groundwater in the Bohemian aquifers is estimated about 11 ka BP at the maximum but the depletion in the stable isotopes suggests that this groundwater originates in the melting of the north European ice sheets after the Last Glacial Maximum period, i.e. 18-20 ka BP. Further investigations on both stable and radioactive carbon isotopes indicated numerous groundwater interactions within the reservoir that were used to delineate the carbon origin within the Bohemian aquifers.Information on groundwater geochemistry was supplemented in the Czech case study by geothermal data in order to improve our knowledge of groundwater flow and dynamics. More than a hundred of temperature records from well-logging measurements were used to assess the geothermal gradient in the Bohemian Cretaceous Basin which is the most promising heat accumulation within the country. Many phenomena can affect the thermal field in the region. Vertical groundwater flow and variations in the lithology and the topography lead to a complicated areal distribution of the geothermal gradient and the heat flux which is dominantly controlled by groundwater. Shallow tectonic structures and numerous volcanic rocks exercise an influence on groundwater flow and therefore exert a secondary effect on the thermal field. The geothermal investigation provided useful information on the geothermal resources within the region but also represents an important tool for understanding groundwater flow, and for constructing realistic hydrogeological models in such a complex geological, tectonic and geothermal context

Este trabalho objetivou a investigação hidrogeológica do município de Monções (cidade do noroeste paulista) onde se estimou existir um total de 61 poços tubulares profundos que exploram dois aqüíferos com porosidades distintas, o Aqüífero Adamantina (granular) e o Aqüífero Serra Geral (fraturado). Ambos são responsáveis por 100% do abastecimento do município, daí o interesse em investigá-los melhor. O aqüífero superior (sedimentar), localmente de pequena espessura, responde por aproximadamente 60% das captações existentes e apenas 20% da vazão total extraída, o que não o torna menos importante e sim mais vulnerável. No inferior, concentra-se a minoria dos poços da área e a maior parte do volume disponível. A metodologia adotada teve por base o reconhecimento geológico preliminar da área e o cadastramento de pontos considerados referências importantes dentro da proposta deste estudo, como poços tubulares profundos, contato geológico das formações presentes na área, locais de depósito e despejo de resíduos urbanos, indústria, áreas de plantio, pontos de degradação fisiográfica, cemitério, entre outros. Em seguida, realizou-se a coleta pontual das informações de interesse que consistiu no registro fotográfico digital das situações consideradas de maior relevância, levantamento de coordenadas e cotas topográficas destes pontos e, por fim, a coleta de água de poços que melhor representassem o contexto da área investigada. Para o tratamento destes dados os pontos foram inicialmente locados na Planta Topográfica de Gastão Vidigal (Instituto Brasileiro de Geografia e Estatística ? 1:50.000), uma vez que a área investigada está inserida na referida Folha, e, posteriormente, conferidos e plotados através da etapa de georreferenciamento. O levantamento realizado propiciou a elaboração de um banco de dados para o município e a confecção de mapas de contorno estrutural (topo da Formação Serra Geral) e de isoespessura (Formação Adamantina), facilitando estimativas de reservas hídricas. Possibilitou ainda uma avaliação crítica dos atuais sistemas de captação, assim como viabilizou a confecção de mapas simplificados (geológico e hidrogeológico) em escala até então não disponível (1:50.000), elaborados com o auxílio do software de georreferenciamento ArcView GIS 3.3. Complementarmente, através da investigação do comportamento químico das águas dos aqüíferos locais, foi possível uma proposta de classificação quanto às zonas produtoras.<br>This work aims the hydrogeologic investigation of Monções municipality (city in the NW São Paulo State - Brazil) where it has been estimated to exist an amount of 61 deep wells exploring two aquifers with different porosity, the Adamantina Aquifer (granular) and Serra Geral Aquifer (fractured). The reason of better investigation is both are responsible by 100% of the municipality water supply. The top aquifer (sedimentary) has locally a small thickness and presents around 60% of the wells on the area and provides only 20% of the total flow exploited. This situation doesn\'t make the aquifer less important but more vulnerable. On the other hand, the bottom aquifer represents the minority of the wells and most of the available flow. The methodology applied was based in preliminary geologic inspection (field work) and register of points that were considered important in this work proposal, like deep wells, formations geologic contact that occur in the study area, urbane residues deposits and launching places (realeasing places), industry, plantation field, physiographic degradation points, cemetery, among others. After that, a punctual collection information of interest was performed, including digital photographic register of the more relevant situations, survey of coordinates and topographic quote of these points and, at last, water collect from representative wells located in the area. For the treatment of these informations, the points were at first located in the Gastão Vidigal topographic map (Brazilian Institute of Geography and Statistic ? 1:50.000), as the study area is included in this chart, and, subsequently, ratified and plothed using the georreference software. The survey developed made possible the elaboration of a database to the investigated municipality and of a structural contour map (Serra Geral Formation\'s Top), as well as a map of isothickness (Adamantina Formation) making easier the estimation of groundwater reserves. Moreover, this information permitted a critical evaluation of the current collection systems as well as made possible the confection of simple maps (geology and hydrogeology), in a better scale that the available one (1:50.000) using the ArcView 3.3 software. Supplementary, through the description the chemical characteristics of waters from local aquifers, made possible a proposal for classification with regard to production areas.

The need of understanding transport processes of contaminants in groundwater has grownalong with the discovering of contamination of soil and groundwater due to industrialization.Mobility of an organic contaminant in the soil is affected by its partitioning to dissolvedorganic carbon, DOC. Partitioning of hydrophobic organic contaminants, HOCs, to DOC isdescribed by the contaminant’s KDOC value. The effects of DOC on transport processes oforganic contaminants with groundwater are still relatively unexplored even though somereviews have been carried out in this particular field of research. The aim of this thesis workwas to investigate transport processes for the PAH phenanthrene and the phthalate Di(2-ethylhexyl) phthalate, DEHP, with DOC by constructing a transport model with the computerprogram FEFLOW 6.1. The thesis work was performed as part of an ongoing Research &amp;Development project investigating alternative remediation techniques at Domsjö industrialsite, located 2 km south of Örnsköldsvik. Generally, the groundwater at the site was characterized by low phenanthrene and DEHPcontent together with high DOC content. In the sampling points with highest reportedcontaminant concentration also DOC was present in highest concentrations. During theperformed literature study it was found that tabulated KDOC values for phenanthrene wasavailable but not for DEHP, which had to be calculated based on available KOC and KOWvalues. Five different modeling scenarios were developed: 1. Transport of phenanthrene with KDOC minimum value. 2. Transport of phenanthrene with KDOC maximum value. 3. Transport of phenanthrene with KDOC median value. 4. Transport of DEHP with KDOC calculated with KOC. 5. Transport of DEHP with KDOC calculated with KOW. Calculations of contaminant concentration in groundwater were made with an equation thatrequires both site and contaminant specific constants. These constants had to be estimatedduring this thesis work, which resulted in insecurities possibly affecting the model results.However, the minimum and the median value of KDOC showed best modeled phenanthreneconcentration after six years compared to measured values. Best result of modeledconcentrations of DEHP was obtained with KDOC calculated with KOC. Correlation analysis ofDOC and contaminants showed a significant correlation between DOC and phenanthrene at99% confidence level, and between DOC and DEHP at 90% confidence level.<br>I takt med ökad kännedom om industriellt förorenade områden har det också blivitbetydelsefullt att känna till de processer som påverkar transport av föroreningar medgrundvattnet. Rörligheten av en hydrofobisk organisk förorening, HOC, påverkas av dessfördelning till löst organiskt kol, DOC, och beskrivs med fördelningskoefficienten KDOC.Effekterna av DOC på föroreningstransporten är relativt okända trots att forskning harbedrivits inom området. Syftet med examensarbetet var att undersöka spridning av fenantren(ämnesklass PAH) och Di(2-etylhexyl)ftalat med DOC genom att konstruera enföroreningsspridningsmodell i datorprogrammet FEFLOW 6.1. Examensarbetet utfördes somdel i ett pågående Forsknings &amp; Utvecklingsprojekt med syfte att utreda en alternativsaneringsteknik för Domsjö industriområde, 2 km söder om Örnsköldsvik. Generellt sett karaktäriserades grundvattnet på platsen av låg fenantren- och DEHP-halttillsammans med hög DOC-halt. På samma ställen där föroreningarna förekom i högstakoncentration var också DOC-koncentrationen som högst. Vid genomförd litteraturstudieåterfanns tabellerade KDOC-värden endast för fenantren. KDOC för DEHP saknades och fickberäknas med ekvationer baserat på förhållandet mellan KDOC och KOC respektive KOW. Femolika modelleringsscenarier utvecklades: 1. Spridning av fenantren med minsta tillgängliga KDOC-värde. 2. Spridning av fenantren med högsta tillgängliga KDOC-värde. 3. Spridning av fenantren med median KDOC-värde. 4. Spridning av DEHP med KDOC beräknat med KOC. 5. Spridning av DEHP med KDOC beräknat med KOW. Beräkning av föroreningarnas koncentration i grundvattnet gjordes med en ekvation somegentligen kräver både plats- och föroreningsspecifika konstanter. Då detta inte fanns att tillgågjordes uppskattning av värdena vilket resulterar i osäkerheter som kan ha påverkan påmodellerade resultat. De bästa modellerade koncentrationerna av fenantren efter sex årssimulering jämfört med uppmätta koncentrationer uppnåddes med minsta och median-värdeav KDOC. Bästa modellerade koncentrationerna av DEHP gavs av KDOC beräknat med KOC.Korrelationstest med DOC och respektive förorening visade en signifikant korrelation mellanDOC och fenantren vid 99% konfidensnivå, och mellan DOC och DEHP vid 90% konfidensnivå.

Les réactions redox impliquant l’oxygène dissous (OD) sont les plus énergétiques et offrent une source majeure d'énergie pour la biosphère profonde. La capacité des milieux fracturés à transporter rapidement des eaux oxygénées de la surface vers la profondeur permet le maintien d’une hydrosphère oxique profonde (HOP) jusqu’à présent négligée. Cette thèse porte donc sur l’origine, la dynamique et les conséquences de cette HOP. Dans un premier temps, nous établissons un cadre conceptuel pour identifier les facteurs qui contrôlent le transport réactif de l’OD à l’échelle d’un bassin versant. Nous développons un modèle d’interactions eau-roche afin de prédire la profondeur de l’HOP. Ce modèle est ensuite utilisé pour expliquer l’occurrence d’une HOP dans les premiers 300 mètres de profondeur de l’Observatoire de la Zone Critique de Ploemeur. Nous étudions le δ18O de l'OD au sein de l'HOP afin d'identifier la distribution des processus biotiques et abiotiques qui contrôlent la réactivité de l'OD dans le bassin versant. Dans un deuxième temps, nous développons deux expériences in-situ pour explorer les conséquences de l’HOP sur le fonctionnement biogéochimique de la subsurface. Grâce à un test de traçage réactif à l'OD et une expérience d'incubation de minéraux, nous démontrons, respectivement, la réponse de la biomasse planktonique et de celle attachée aux minéraux aux dynamiques oxiques-anoxiques de la subsurface. Ces travaux mettent en lumière une HOP dans laquelle les processus biogéochimiques souterrains sont sensibles aux dynamiques hydrologiques de surface impliquant le transport de l'OD, remettant ainsi en question le paradigme de la biosphère profonde en tant que système inertiel et anoxique<br>Redox reactions involving dissolved oxygen (DO) are the most energetic and provide a major source of energy for the deep biosphere. The ability of fractured rocks to rapidly transport oxygenated waters from the surface to depth allows for the existence of a deep oxic hydrosphere (DOH), which has been historically neglected. This thesis focuses on the origin, dynamics, and consequences of this DOH. First, we establish a conceptual framework to identify the factors controlling the reactive transport of DO at the watershed scale. We develop a water-rock interaction model to predict the depth of the DOH. This model is used to explain the occurrence of a DOH within the first 300 meters of the aquifer in the Critical Zone Observatory of Ploemeur. We investigate the δ18O of DO within the DOH to identify the distribution of biotic and abiotic processes that control the reactivity of DO in the watershed. Second, we conduct two in-situ experiments to explore the consequences of the DOH on the biogeochemical functioning of the subsurface. A reactive DO tracer test and a mineral incubation experiment are developed to study the response of, respectively, the planktonic and mineral-attached biomass to oxic and anoxic dynamics in the subsurface. This work highlights a DOH in which subsurface biogeochemical processes are sensitive to surface hydrological dynamics involving the transport of DO, thus challenging the paradigm of the deep biosphere as an inert and anoxic system<br>Las reacciones redox que involucran oxígeno disuelto (OD) son las más energéticas y proporcionan una fuente importante de energía para la biosfera subterránea. La capacidad de las rocas fracturadas para transportar rápidamente aguas oxigenadas desde la superficie hasta la profundidad permite la existencia de una hidrosfera óxica profunda (HOP), que históricamente ha sido ignorada. Esta tesis se centra en el origen, la dinámica y las consecuencias de esta HOP. En primer lugar, establecemos un marco conceptual para identificar los factores que controlan el transporte reactivo del OD a escala de cuenca. Desarrollamos un modelo de interacción agua-roca para predecir la profundidad de la HOP. Este modelo se utiliza para explicar la ocurrencia de una HOP dentro de los primeros 300 metros del acuífero en el Observatorio de la Zona Crítica de Ploemeur. Investigamos el δ18O del OD dentro de la HOP para identificar la distribución de los procesos bióticos y abióticos que controlan la reactividad del OD en la cuenca. En segundo lugar, realizamos dos experimentos in-situ para explorar las consecuencias de la HOP en el funcionamiento biogeoquímico del subsuelo. Se desarrolla una prueba de trazador reactivo con OD y un experimento de incubación mineral para estudiar la respuesta de la biomasa planctónica y adherida a los minerales, respectivamente, a las dinámicas óxicas y anóxicas en el subsuelo. Este trabajo destaca una HOP en la que los procesos biogeoquímicos subterráneos son sensibles a las dinámicas hidrológicas superficiales que implican el transporte de OD, desafiando así el paradigma de la biosfera profunda como un sistema inerte y anóxico

Made available in DSpace on 2014-07-29T15:01:44Z (GMT). No. of bitstreams: 1 DAnnyell Nogueira.pdf: 1253060 bytes, checksum: f659e9378a6f840582e2bff89b8b243e (MD5) Previous issue date: 2010-09-03<br>The research developed sought to contribute to the conservation of groundwater resources, aiming in developing a Geographic Information System (GIS) as a tool to manage the use of groundwater targeting the sustainable use, for public supply in the city of Aparecida de Goiânia/GO. In order to achieve this, a Geographic Information System (GIS) was used for the registration of deep wells, continuing the research with a study of natural vulnerability by mapping the information obtained wich relates the potential sources of contamination. Data collection took place through a consultation with the Information System for Groundwater (SIAGAS) and through the System of Statistics and Geographic Information of the State of Goiás (SIEG). Through the database development it was possible to apply the DRASTIC method adapted by Narciso and Gomes (2005) and GOD method proposed by Foster and Hirata (1988) for mapping vulnerability to contamination of groundwater resources. In order to apply the DRASTIC method adapted, maps were generated for slope, land use, geology, geomorphology, water resources and human occupation. The map resulting from this method shows four classes: low, medium, high and very high, showing that of the 288 square kilometers of this city, almost 80% were classified as having medium vulnerability fir the groundwater quality. For the GOD method, maps of the degree of hydraulic confinement, geology and depth or distance of the groundwater level were generated. The map resulting from this process had only three classes: negligible, low and high, showing that 76% of the area was classified as having a negligible vulnerability. This occurred because this method does not consider human occupation.<br>A pesquisa desenvolvida buscou contribuir para a conservação dos recursos hídricos subterrâneos, tendo como objetivo o desenvolvimento de um Sistema de Informação Geográfica (SIG) como instrumento de gestão para a utilização das águas subterrâneas visando o seu uso sustentável, para o abastecimento público na cidade de Aparecida de Goiânia/GO. Para atingí-lo utilizou-se um Sistema de Informações Geográficas (SIG) para o cadastramento dos poços tubulares profundos, procedendo assim ao estudo da vulnerabilidade natural, através do mapeamento das informações obtidas, além de relacionar as fontes potenciais de contaminação. A obtenção dos dados deu-se através da consulta ao Sistema de Informações de Águas Subterrâneas (SIAGAS) e através do Sistema Estadual de Estatística e de Informações Geográficas de Goiás (SIEG). Estes dados possibilitaram a elaboração do banco de dados e a aplicação do método DRASTIC adaptado por Narciso e Gomes (2005) e do método GOD proposto por Foster e Hirata (1988), para a geração de mapas de vulnerabilidade à contaminação dos recursos hídricos subterrâneos. Para a elaboração do método DRASTIC adaptado foram gerados os mapas de declividade, uso do solo, geologia, falhas geológicas, recursos hídricos e ocupação humana. O mapa resultante desse método apresentou quatro classes: baixa, média, alta e muito alta, sendo que dos 288 quilômetros quadrados deste município, aproximadamente 80% foi classificado como tendo vulnerabilidade média para a qualidade das águas subterrâneas. Para o método GOD foram gerados os mapas de grau de confinamento hidráulico, ocorrência do substrato litológico e profundidade ou distância do nível da água subterrânea. O mapa resultante desse processo apresentou apenas três classes: desprezível, baixa e alta, sendo que 76% da área foi classificado como vulnerabilidade desprezível, por este método não considerar a ocupação humana.

L'aquifère molassique du Bas-Dauphiné est situé le long de la vallée du Rhône, dans le Sud-Est de la France. Cet aquifère d'une superficie proche de3000 km², et d'une épaisseur moyenne de 400m renferme une eau d'excellente qualité, utilisée par de nombreuses collectivités pour l'alimentation en eau potable. Cependant certains secteurs montrent une forte vulnérabilité de la nappe aux activités agricoles. L'utilisation d'outils géochimiques etisotopiques a permis de préciser le fonctionnement hydrodynamique de l'aquifère. Dans un premier temps, nous avons montré que la stratification des écoulements décrite par De La Vaissière (2006) sur la partie drômoise de l'aquifère s'étend au secteur isérois. Les eaux les plus profondes ont des vitesses de circulation de l'ordre du mètre par an alors que les flux superficiels ont des vitesses de circulations d'une centaine de mètres par an. D'autre part, le marquage des nappes superficielles et des rivières par des teneurs faibles en tritium (de 3 à 4 UT) et forte en magnésium (jusqu'à 18 mg/L)indique un apport d'eaux anciennes, issues de l'aquifère molassique vers ces eaux superficielles. La définition de deux pôles d'eaux et l'application d'une équation de mélange couplés à la réalisation de bilans hydrogéologique a permis d'appréhender les volumes échangés. Il apparaît finalement que les réservoirs d'eaux superficiels constituent l'exutoire principal de l'aquifère molassique. L'utilisation des éléments traces a mis en avant le rôleessentiel du temps de séjour des eaux dans l'aquifère ainsi que des conditions d'oxydo-réduction dans l'acquisition de la minéralisation. L'évaluation de la qualité naturelle des eaux de la nappe a montré l'impact des activités agricoles sur l'aquifère, avec prés de 80% des échantillons ayant une teneur en nitrates supérieure à la concentration naturelle supposée. L'étude des teneurs en pesticides conforte ce constat. De plus l'étude de l'évolution des concentrations en polluants montre une dégradation de la ressource.

In Texas, landowner associations for the management of common-pool resources such as wildlife and groundwater have become increasingly popular. Successful management of white-tailed deer (Odocoileus virginianus) depends upon the collective decision-making of landowners. Likewise, aquifer reserves are a trans-boundary resource subject to the "rule of capture." Numerous factors may affect the success of common-pool associations, including property ownership and habitat characteristics, landowner demographics, and social capital. I used a mail questionnaire to explore the relationship between these factors and their effect on association activities and management practices for eight Wildlife Management Associations (WMAs) occurring within the Lower Post Oak Savannah (LPOS) and the Central Post Oak Savannah (CPOS). In addition, I compared responses of members of WMAs in CPOS to members of the Brazos Valley Water Alliance (BVWA), a groundwater association situated in the region. Compared to CPOS, members of WMAs within the LPOS belonged to much larger groups, were generally more recent landowners that met more often, raised more money using more funding methods, and tended to have longer association membership than CPOS landowners, yet they had lower social capital. CPOS landowners owned significantly more land and considered relaxation/leisure and hunting more important land uses than LPOS landowners. The smaller group size in CPOS may be the most important factor in building social capital. Intra-association trust was positively influenced by the longevity of property ownership, the number of association meetings, the percentage of males in the association, and other factors. Negative influences on trust included absentee ownership and Habitat Cover Index, which was a measure of the amount of wooded habitat present. In CPOS, members of the BVWA were part of a much larger, more heterogeneous, and more recently formed group than members of WMAs. They also placed greater importance on utilitarian aspects of their properties, as opposed to land stewardship for conservation as practiced by members of WMAs. If associations are kept small ( < 50) with more frequent meetings, greater social capital and information sharing may be achieved, which may lead to increased land stewardship practices. However, landowners may be motivated more by their shared values independent of any benefit from their association.

碩士<br>國立交通大學<br>土木工程系所<br>93<br>The excessive land subsidence induced by over-pumping of groundwater is usually explained by the consolidation of aquitards. However, some evidence from field measured data has shown that, in some cases, the compression of some aquifer (e.g., sandy layer) may be quite significant. Generally, it is difficult to obtain undisturbed sandy samples in field. Because the results of laboratory experiment using disturbed specimens were unable to express the real characteristic of in-situ layer, this study took the disturbed soils in Choshui River alluvial fan to reconstitute by pluviation and consolidation and try to examine the compressibility of deep aquifer induced by groundwater withdraw. During consolidation, shear wave velocity were measured by bender elements embedded in the upper and bottom plates of the consolidation device. The state of the reconstituted material was examined by its shear wave velocity in order to match the same wave velocity as obtained from in-situ P-S logger tests. After material reconstitution, the specimens were subjected to loading/unloading cycles to simulate that effective stress changes due to the groundwater-level fluctuation. The results of laboratory test were also compared with field data to verify the validity of the laboratory model test. Experimental results show that the stress state of in-situ layer was influenced by the soil deposition (e.g., the arrangement of soil particle), stress history and others. These factors cause the stress condition of samples were not consistent with the state in field when shear wave velocity were the same in laboratory and in field. Because the stress state were not consistent, the way that reconstituted specimens were returned to original condition by comparing shear wave velocity is not better. However, it is still acceptable. In the future, the factors should be overcome while preparing the remold specimens for laboratory experiments. A series of laboratory consolidation test for modeling the groundwater-level fluctuation were conducted in this study. The results indicated the deep aquifer of Choshui River alluvial fan was compressed by loading/unloading cycles, and the rebound of sandy layer was not clear as the stress was unloading. These findings show the compression of aquifer due to groundwater-level fluctuation is plastic. Hence, the compressibility of deep aquifer should be considered when estimating the land subsidence. This study also finds the compression of aquifer with thin clayey layers is time-dependent. Similar phenomenon was observed in field. Thus, the laboratory test may explain the land subsidence phenomenon contributed by the compression of deep aquifer.

碩士<br>國立臺灣大學<br>農業工程學系<br>82<br>The annual recharge of groundwater is about 4500 million tons but the annual pumped groundwater is 7500 million tons in Taiwan during1991.It demonstrates the seriousness that annual withdrawal is over safe yield .It is very profuse of groundwater in Cho - Shui Chi alluvium fan plain. The over pumping of the ground water for the use of agriculture , industry ,public and cultivation still causes sea water intrusion and land subsidence . The research area in this study is Cho - Shui Chi plain . According to the judgement in geology , it can distinguished into three parts : intake zone( unconfined aquifer ) , unconfined aquifer of double layer ( shallow layer ) ,confined aquifer of double layer ( deep layer ) .Because of the fluxes move from unconfined aquifer of intake zone to both shallow and deep layer , 2 - D and 3 - D groundwater model are conjunctive to simulate the withdrawal of groundwater in Cho - Shui Chi plain . The result is provided to estimate geohydraulic parameters and to investigate groundwater resource management in the furture . The result shows that the groundwater pumped during 1991 in this area is 1644 million tons . Among all 85 million tons is pumped from the unconfined intake zone (5.18%) ; 634 million tons from the shallow layer of double layer (38.56%) ;925 million tons from the deep layer of double layer (56.26%). The groundwater pumped is mainly in dry season (from January to April) and on the coast area.

Numerous glacial advances over the past 2 million years have covered the entire Canadian and Fennoscandian Shield outcrop. During glacial advance and retreat, permafrost is expected to form in front of the glacier. The question of how permafrost and freezing impact the formation and evolution of brines in natural systems may be vital to understanding the chemistry of groundwater in crystalline rocks. Investigations of groundwater conditions beneath thick permafrost can provide valuable information that can be applied to assessing safety of deep, underground nuclear waste repositories and understanding analogues to potential life-bearing zones on Mars. However, very little scientific investigation of cryogenic processes and hydrogeology deep within crystalline systems has been published. The purpose of this research is to evaluate the impacts of thick permafrost (>300m) formation on groundwater chemical and flow system evolution in the crystalline rock environment over geologic timescales. A field investigation was conducted at the Lupin Mine in Nunavut, Canada, to characterize the physical and hydrogeochemical conditions within and beneath a thick permafrost layer. Taliks, or unfrozen channels within the permafrost, are found beneath large lakes in the field area, and provide potential hydraulic connections through the permafrost. Rock matrix waters are dilute and do not appear to affect groundwater salinity. Permafrost waters are Na-Cl and Na-Cl-SO4 type, and have been contaminated with chloride and nitrate by mining activities. Sulfide oxidation in the permafrost may be naturally occurring or is enhanced by mining activities. Basal permafrost waters (550 to 570 mbgs) are variably affected by mining. The less contaminated basal waters have medium sulfate concentrations and are Ca-Na dominated. This is similar to deeper, uncontaminated subpermafrost waters, which are Ca-Na-Cl or Na-Ca-Cl type with a wide range of salinities (2.6 to 40 g•L-1). The lower salinity subpermafrost waters are attributed to dissociation of methane hydrate and drawdown of dilute talik waters by the hydraulic gradient created by mine dewatering. This investigation was unable to determine the influence of talik waters to the subpermafrost zone in undisturbed conditions. Pressures are also highly variable, and do not correlate with salinity. Fracture infillings are scarce and calcite δ18O and δ13C values have a large range. Microthermometry indicates a large range in salinities and homogenization temperatures as well, indicative of a boiling system. In situ freezing of fluids and methane hydrate formation may have concentrated the remaining fluids. Field activities at the Lupin mine also provided an opportunity to study the nature of gases within crystalline rocks in a permafrost environment. Gases were generally methane-dominated (64 to 87), with methane δ13C and δ2H values varying between -56 and -42‰ VPDB and -349 to -181 ‰ VSMOW, respectively. The gases sampled within the Lupin mine have unique ranges of chemical and isotopic compositions compared with other Canadian and Fennoscandian Shield gases. The gases may be of thermogenic origin, mixed with some bacteriogenic gas. The generally low δ2H-CH4 ratios are somewhat problematic to this interpretation, but the geologic history of the site, a metaturbidite sequence, supports a thermogenic gas origin. The presence of gas hydrate in the rock surrounding Lupin was inferred, based on temperature measurements and hydrostatic pressures. Evidence also suggests fractures near the mine have been depressurized, likely due to mine de-watering, resulting in dissipation of methane hydrate near the mine. Modeling results indicate methane hydrates were stable throughout the Quaternary glacial-interglacial cycles, potentially limiting subglacial recharge. The effects of deep permafrost formation and dissipation during the Pleistocene glacial/interglacial cycle to deep groundwaters in the Canadian Shield were also investigated by compiling data from thirty-nine sites at twenty-four locations across the Canadian Shield. Impacts due to glacial meltwater recharge and surficial cryogenic concentration of fluids, which had been previously considered by others, and in situ freeze-out effects due to ice and/or methane hydrate formation were considered. At some Canadian Shield sites, there are indications that fresh, brackish, and saline groundwaters have been affected by one of these processes, but the data were not sufficient to differentiate between mixed, intruded glacial meltwaters, or residual waters resulting from either permafrost or methane hydrate formation. Physical and geochemical data do not support the cryogenic formation of Canadian Shield brines from seawater in glacial marginal troughs. The origin and evolution of Canadian and Fennoscandian Shield brines was explored with a survey of chlorine and bromine stable isotope ratios. The δ37Cl and δ81Br isotopic ratios varied between -0.78 ‰ and 1.52 ‰ (SMOC) and 0.01 ‰ and 1.52 ‰ (SMOB), respectively. Variability of chlorine and bromine isotope ratios decreases with increasing depth. Fennoscandian Shield groundwaters tend to be more enriched than Canadian Shield groundwaters for both 37Cl and 81Br. Other sources and processes which may affect δ37Cl and δ81Br composition are also explored. Primary processes such as magmatic and/or hydrothermal activity are thought to be responsible for the isotopic composition of the most concentrated fluids at each site. Positive correlations between δ81Br, and δ37Cl with δ2H-CH4 and δ13C-CH4 were noted. At this time the cause of the relationship is unclear, and may be a result of changing redox, pH, temperature, and/or pressure conditions during hydrothermal, metamorphic, or volcanogenic processes. The data suggest solute sources and fluid evolution at individual sites would be better constrained utilizing a multi-tracer investigation of δ37Cl, δ81Br, and 87Sr/86Sr ratios comparing fluids, rocks, and fracture filling minerals (including fluid inclusions).

Carbon Dioxide (CO₂) Enhanced Oil Recovery (EOR) is becoming an important bridge to commercialize geologic sequestration (GS) in order to help reduce anthropogenic CO₂ emissions. Current U.S. environmental regulations require operators to monitor operational and groundwater aquifer changes within permitted bounds, depending on the injection activity type. We view one goal of monitoring as maximizing the chances of detecting adverse fluid migration signals into overlying aquifers. To maximize these chances, it is important to: (1) understand the limitations of monitoring pressure versus geochemistry in deep aquifers (i.e., >450 m) using analytical and numerical models, (2) conduct sensitivity analyses of specific model parameters to support monitoring design conclusions, and (3) compare the breakthrough time (in years) for pressure and geochemistry signals. Pressure response was assessed using an analytical model, derived from Darcy's law, which solves for diffusivity in radial coordinates and the fluid migration rate. Aqueous geochemistry response was assessed using the numerical, single-phase, reactive solute transport program PHAST that solves the advection-reaction-dispersion equation for 2-D transport. The conceptual modeling domain for both approaches included a fault that allows vertical fluid migration and one monitoring well, completed through a series of alternating confining units and distinct (brine) aquifers overlying a depleted oil reservoir, as observed in the Texas Gulf Coast, USA. Physical and operational data, including lithology, formation hydraulic parameters, and water chemistry obtained from field samples were used as input data. Uncertainty evaluation was conducted with a Monte Carlo approach by sampling the fault width (normal distribution) via Latin Hypercube and the hydraulic conductivity of each formation from a beta distribution of field data. Each model ran for 100 realizations over a 100 year modeling period. Monitoring well location was varied spatially and vertically with respect to the fault to assess arrival times of pressure signals and changes in geochemical parameters. Results indicate that the pressure-based, subsurface monitoring system provided higher probabilities of fluid migration detection in all candidate monitoring formations, especially those closest (i.e., 1300 m depth) to the possible fluid migration source. For aqueous geochemistry monitoring, formations with higher permeabilities (i.e., greater than 4 x 10⁻¹³ m²) provided better spatial distributions of chemical changes, but these changes never preceded pressure signal breakthrough, and in some cases were delayed by decades when compared to pressure. Differences in signal breakthrough indicate that pressure monitoring is a better choice for early migration signal detection. However, both pressure and geochemical parameters should be considered as part of an integrated monitoring program on a site-specific basis, depending on regulatory requirements for longer term (i.e., >50 years) monitoring. By assessing the probability of fluid migration detection using these monitoring techniques at this field site, it may be possible to extrapolate the results (or observations) to other CCUS fields with different geological environments.<br>text

Soils of 49 agricultural and 2 "native condition" sites in the Lower Umatilla Basin, Oregon were sampled for nitrate-nitrogen, ammonium-nitrogen, chloride, and pH beginning in Fall of 1992. Several sites were sampled in Spring and Fall 1993 in order to indicate movement or loss of residual soil nitrogen over time. This study was prompted by current concern over contamination of public drinking water supplies by nitrate and the designation of over 550 square miles of this region as a Ground Water Management Area. This study sought to identify links between agricultural management practices-primarily irrigation, fertilization, and crop rotation systems, and deep soil nitrate levels. Soil profiles were divided into 3 "management zones:" 0-3', 3-6', and beyond 6' in depth. These depths represent average rooting depths for the major agricultural crops of the study area. In general, the effective rooting depth of most area-crops does not extend beyond 6', therefore, it was determined that residual soil-nitrate found at this depth or beyond may be a potential source of ground water contamination if not managed correctly. Results of the study indicate that proper management of irrigation, fertilization, and cropping rotation can significantly reduce the potential for contaminating ground water. Deep soil nitrate levels under most agricultural fields were consistent with the concept that some loss of nitrate below the root zone is inevitable, however, this condition can be minimized through intensive crop management. This study concludes that responsible management of agriculture can minimize impacts on ground water, while providing quality food and fiber products to an ever-growing population. In addition, more research is needed in the area of crop physiology and response to intensively managed systems. Such research may provide insight into more efficient methods of crop production and environmental protection.<br>Graduation date: 1995

abstract: Population growth within drylands is occurring faster than growth in any other ecologic zone, putting pressure on already stressed water resources. Because the availability of surface water supplies in drylands tends to be highly variable, many of these populations rely on groundwater. A critical process contributing to groundwater recharge is the interaction between ephemeral channels and groundwater aquifers. Generally, it has been found that ephemeral channels contribute to groundwater recharge when streamflow infiltrates into the sandy bottoms of channels. This process has traditionally been studied in channels that drain large areas (10s to 100s km2). In this dissertation, I study the interactions between surface water and groundwater via ephemeral channels in a first-order watershed located on an arid piedmont slope within the Jornada Experimental Range (JER) in the Chihuahuan Desert. To achieve this, I utilize a combination of high-resolution observations and computer simulations using a modified hydrologic model to quantify groundwater recharge and shed light on the geomorphic and ecologic processes that affect the rate of recharge. Observational results indicate that runoff generated within the piedmont slope contributes significantly to deep percolation. During the short-term (6 yr) study period, we estimated 385 mm of total percolation, 62 mm/year, or a ratio of percolation to rainfall of 0.25. Based on the instrument network, we identified that percolation occurs inside channel areas when these receive overland sheetflow from hillslopes. By utilizing a modified version of the hydrologic model, TIN-based Real-time Integrated Basin Simulator (tRIBS), that was calibrated and validated using the observational dataset, I quantified the effects of changing watershed properties on groundwater recharge. Distributed model simulations quantify how deep percolation is produced during the streamflow generation process, and indicate that it plays a significant role in moderating the production of streamflow. Sensitivity analyses reveal that hillslope properties control the amount of rainfall necessary to initiate percolation while channel properties control the partitioning of hillslope runoff into streamflow and deep percolation. Synthetic vegetation experiments show that woody plant encroachment leads to increases in both deep percolation and streamflow. Further woody plant encroachment may result in the unexpected enhancement of dryland aquifer sustainability.<br>Dissertation/Thesis<br>Doctoral Dissertation Geological Sciences 2017

<p><p>Clean water is a critical natural resource. We do not have much available: only 2.5% of water on Earth is freshwater and of that only 31% is in liquid form. 96% of the liquid fresh water is groundwater. Unfortunately that resource is subject to contamination by hazardous materials accidentally or illicitly spilled, leaked, or deposited in or on the ground. Among the methods to remediate these disasters, pump-and-treat (P&T) is the most common. The vertical circulation well (VCW) is a P&T configuration with extraction and injection sites within the same well. It can be adapted to many remediation techniques and has been gaining popularity since the 1990s and is often a better alternative to conventional P&T. Conventional P&T and VCWs are typically run with steady flow.</p></p><p><p>The major bottleneck to steady flow remediation is that contaminants become trapped in dead-end pores. In an aquifer there are two types of pores: <it>pass-through</it> pores and <it>dead-end</it> pores. The flow in former completely sweeps through the pore space while the flow does not enter the later; however, the flow through the <it>pass-through</it> pore induces a vortex in the <it>dead-end</it> pore. Under steady flow the only mechanism for contaminants to escape the <it>dead-end</it> pores is molecular diffusion.</p></p><p><p>A similar problem is encountered in the removal of surfactants in the manufacture of semiconductor and the removal of oil residue build-up in small ducts. Manufacturers discovered that pulsed flow would accelerate the mass transfer between the cavities and grooves on these surfaces and the external flow. This was because the unsteady ramp-up in flow rate initiated a deep sweep of the cavities. The unsteady ramp-down in flow rate initiated a vortex ejection where the sequestered vortex is no longer constrained and protrudes from the cavity.</p></p><p><p>We hypothesized that just as pulsed flow improves cleaning of grooved surfaces in several manufacturing procedures, rapidly pulsed pumping (with a period on the order of a second rather than weeks or months) in pump-and-treat groundwater remediation would boost the diffusion-limited removal of contaminants trapped in dead-end pores by generating transient deep sweeps and vortex ejections in these pores. These processes have not yet been exploited in groundwater remediation to any significant degree.</p></p><p><p>We tested our hypothesis in a series of numerical and laboratory experiments. We considered unwashed and washed media. For unwashed media (Chapter 1) we used as a square pore in the numerical domain and crushed glass (for its negligible sorption capacity) in laboratory column studies. For washed media (Chapter 2) we used a smooth dead-end pore constructed with two tangential quarter circles as the pore in the numerical domain and glass spheres in the laboratory column studies. In all our laboratory experiments we used a fluorescent dye, Fluorescein, as a conservative tracer. We used the same parameters in our numerical experiments. However, in some we also considered immiscible contaminants such as NAPLs (Chapter 4).</p></p><p><p>All numerical experiments were conducted with the computational fluid dynamics software, FIDAP. In numerical experiments we studied the contaminant removal from interacting dead-end pores connected to both a straight pass-through pore and a divergent pass-through pore. The latter with the flow somewhat analogous to the radial spreading encountered around a around a well in field applications (Chapter 5).</p></p><p><p>To elucidate the dead-end pore dynamics (Chapter 3), we performed numerical experiments and used a physical model to obtain a relationship between the rapidly pulsed flow frequency and length of the pore. Our dimensional analysis pointed to the change in pressure as the key component in the initiation of transient deep sweeps and vortex ejections, two new pore-cleaning mechanisms.</p></p><p><p>We conclude that the rapidly pulsed flow improves the recovery of contaminants from unwashed, or rough, porous media. In numerical experiments with a pore system consisting of just a single square dead-end pore and a single pass-through pore, at 100 pore volumes pumped the rapidly pulsed flow improved cleanup of the dead-end pore alone by approximately 40%. This translates into a 10% improvement of the cleanup of the pore system (dead-end and pass-through pore). Since the dead-end pore is the bottleneck of the current groundwater remediation, it the first measure that is relevant.</p></p><p><p>In corresponding laboratory column experiments with crushed glass, the dead-end pore volume alone is not known. The cleanup of the whole pore space was improved by roughly 10% with the rapidly pulsed pumping, which corresponds nicely to our numerical results.</p></p><p><p>Our numerical experiments demonstrate that there exists an optimal pulsed pumping frequency that is a function of the local flow velocity and the pore geometry (size and morphology).</p></p><p><p>The contaminant recovery from washed, or rounded, media was not as pronounced in the laboratory experiments and the numerical experiments showed no improvement. While both rapidly pulsed and steady flow recovered all of the contaminant in the laboratory column tests, the difference in the time between the two pumping schemes was approximately 0.9 pore volumes pumped. This improvement is likely to be amplified with sorbing contaminants.</p></p><p><p>Many contaminants are non-aqueous phase liquids (NAPLs), which do not readily dissolve in water. We showed in numerical experiments that rapidly pulsed flow can recover NAPLs with viscosity lower than water, but is not as effective with higher viscosity materials; however, these results were based on a model that did not account for interfacial tension and wetting; therefore we will require additional numerical and laboratory experiments.</p></p><p><p>In practice, a flow through porous media is significantly more complex than the one-directional dominated flows considered in our numerical and laboratory column experiments. Around a well the flow is typically three-dimensional and largely radially dominated. We constructed two numerical domains to study the interactions between the cleanup of three square pores: one in a straight channel and one in a divergent channel to study the radial spread that would be experienced around a well. For a series of three dead-end pores, there was a 35% improvement by rapidly pulsed flow over steady flow in the straight channel and a 33% improvement in the divergent domain. The optimal frequency was different in the divergent flow even though the pores were the same size as in the previous study. Since the divergent channel reduced the flow velocity, the pulses reached the pores at a decreasing rate. Due to this divergence and the range of pore-sizes in a natural aquifer, implementation of rapidly pulsed flow should likely include a range of frequencies.</p></p><p><p>We concluded that the rapidly pulsed flow on the time scale of one-second would greatly enhance the cleanup of contaminated aquifers by P&T or VCW approaches. We measured significant improvements in the time to recovery. For our preliminary VCW experiment showed that rapidly pulsed pumping recovers 50% of the contaminant four times faster than steady pumping. P&T and VCW remediation typically use a steady flow; there are some methods that change the flow rate in P&T and other configurations, such as the VCW. These periodic changes in rate are on the scale of months to years. Some VCWs and air sparging technologies pulse oxygen, surfactants, and/or nutrients into the aquifer to oxidize, mobilize, or bioremediate the contaminants. As reviewed in chapter 6 in detail, all pulsing so far applied in remediation is on the time scale of a day or longer. Such low pulsing frequency does not produce sufficiently many deep sweeps to make a significant difference in cleaning dead-end pores.</p></p><p><p>Implementation of rapidly pulsed technology will utilize the same extraction and injection wells currently used in pump-and-treat remediation but will require replacement or significant modification of the pumps.</p></p><p><p>There are public health and financial implications of this research. In the dissertation conclusions section we reinterpret our numerical experiments with the multiple interacting dead-end pores and a divergent pass-through pore and laboratory experiments with a vertical circulation well chamber by calculating and plotting the ratio of times needed to reach a specified fraction recovered (specified cleanup level) in the steady and rapidly pulsed pumping modes, \tau_{s} / \tau_{p}. This ratio represents the speedup factor, i.e., the factor by which the time needed to reach the specified cleanup level with the conventional remediation (with steady pumping) would be reduced. From our experiments it appears that with the increasing level of targeted cleanup (contaminant fraction recovered), the speedup factor increases and may even exceed an order of magnitude. As we demonstrate in the dissertation conclusions section, this could translate into tens of billions of dollars in savings. Whether or not the laboratory speedup factors would hold in the field cannot be established without field-scale experiments.</p></p><br>Dissertation

Nuclear power generation is being regarded as a solution to ever increasing demand for electricity, and concerns over global warming and climate change due to the use of fossil fuels. Although nuclear power generation is considered to be reliable, economical, clean, and safe, the wastes produced from the nuclear fuel cycle are not, and can remain hazardous for hundreds of thousands of years. An international consensus has developed over the past several decades that deep geologic disposal of low, intermediate, and high level radioactive wastes is the best option to protect the biosphere. In this thesis, both regional scale and sub-regional scale models are created to simulate groundwater flow and transport for a representative Canadian Shield setting, honouring site-specific topography and surface water features. Sub-surface characteristics and properties are derived from numerous geoscience studies. In addition, a regional scale model is developed, centred on the Bruce Nuclear Power Development (BNPD) site near Tiverton, Ontario, and located within the Michigan Basin. Ontario Power Generation (OPG) has proposed a Deep Geologic Repository (DGR) for low & intermediate level waste (L&ILW) at the BNPD site. Paleoclimate simulations using various combinations of parameters are performed for both the Canadian Shield Sub-Regional model, and the Michigan Basin Regional model. Fracture zone permeability is a very important parameter when modelling crystalline rock settings. Migration of a unit tracer representing glacial recharge water can occur to depth in fractures of high permeability. Representative rock compressibility values are necessary as compressibilities are used to calculate storage coefficients, and the one-dimensional loading efficiency; these affect the subsurface propagation of elevated pore pressures due to glacial loading at surface. Coupled density-dependent flow and transport in paleoclimate simulations affects deep flow systems and provides a measure of flow stability, as well as increasing the mean life expectancy at depth. Finally, hydromechanical coupling is a very important mechanism for reducing vertical hydraulic gradients during a glaciation event when a hydraulic boundary condition equal to the pressure at the base of an ice-sheet is applied at ground surface. Pore water velocities are reduced, thereby retarding migration of surface waters into the subsurface environment.