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Academic literature on the topic 'Aquitard'

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Published: 4 June 2021
Last updated: 29 January 2023

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Journal articles on the topic "Aquitard"

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Wang, Quanrong, Junxia Wang, Hongbin Zhan, and Wenguang Shi. "New model of reactive transport in a single-well push–pull test with aquitard effect and wellbore storage." Hydrology and Earth System Sciences 24, no. 8 (August 18, 2020): 3983–4000. http://dx.doi.org/10.5194/hess-24-3983-2020.

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Abstract. The model of single-well push–pull (SWPP) test has been widely used to investigate reactive radial dispersion in remediation or parameter estimation of in situ aquifers. Previous analytical solutions only focused on a completely isolated aquifer for the SWPP test, excluding any influence of aquitards bounding the tested aquifer, and ignored the wellbore storage of the chaser and rest phases in the SWPP test. Such simplification might be questionable in field applications when test durations are relatively long because solute transport in or out of the bounding aquitards is inevitable due to molecular diffusion and cross-formational advective transport. Here, a new SWPP model is developed in an aquifer–aquitard system with wellbore storage, and the analytical solution in the Laplace domain is derived. Four phases of the test are included: the injection phase, the chaser phase, the rest phase and the extraction phase. As the permeability of the aquitard is much smaller than the permeability of the aquifer, the flow is assumed to be perpendicular to the aquitard; thus only vertical dispersive and advective transports are considered for the aquitard. The validity of this treatment is tested against results grounded in numerical simulations. The global sensitivity analysis indicates that the results of the SWPP test are largely sensitive (i.e., influenced by) to the parameters of porosity and radial dispersion of the aquifer, whereas the influence of the aquitard on results could not be ignored. In the injection phase, the larger radial dispersivity of the aquifer could result in the smaller values of breakthrough curves (BTCs), while there are greater BTC values in the chaser and rest phases. In the extraction phase, it could lead to the smaller peak values of BTCs. The new model of this study is a generalization of several previous studies, and it performs better than previous studies ignoring the aquitard effect and wellbore storage for interpreting data of the field SWPP test reported by Yang et al. (2014).
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Shaw, R. Joel, and M. Jim Hendry. "Hydrogeology of a thick clay till and Cretaceous clay sequence, Saskatchewan, Canada." Canadian Geotechnical Journal 35, no. 6 (December 1, 1998): 1041–52. http://dx.doi.org/10.1139/t98-060.

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Clay-rich glacial till and Cretaceous clay are common throughout the Interior Plains of North America. Quantifying groundwater flow through these aquitards has implications for solute transport in aquitards and protection of underlying aquifers. Groundwater flow through a two-tiered aquitard system was investigated using laboratory and field methods at a test site in Saskatchewan, Canada. The aquitard system consists of 80 m of uniform, plastic clay-rich Battleford till (deposited 12-18 ka BP) disconformably overlying 77 m of late Cretaceous plastic marine clay (Snakebite Member, deposited 70-72 Ma BP). The upper 3-4 m of till is oxidized and fractured whereas the remainder is unoxidized. For the scales investigated, results suggested that hydraulic conductivity, K, is independent of scale for relatively thick till and clay bedrock deposits. Analysis of slug tests in the unoxidized till and laboratory tests on cores of unoxidized till yielded geometric mean K values of 5.4 × 10-11 and 2.7 × 10-11 m/s, respectively. Laboratory K tests of clay samples yielded a geometric mean K of 4.3 × 10-12 m/s. Bulk K of the clay was estimated to be 2.3 × 10-12 m/s assuming steady-state flow through the till and clay. The present-day groundwater velocity through the aquitard system was estimated to be between 0.5 and 0.8 m/10 ka downward based on the measured K values, measured hydraulic gradients, and measured porosities. Results suggested that pore water in much of the till was introduced during or shortly after glaciation.Key words: hydrogeology, aquitards, Cretaceous clay, Battleford till, hydrogeologic properties, geotechnical properties.
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Trieu, Duc Huy, Ngoc Thanh Tong, Van Lam Nguyen, Ba Quyen Pham, Dai Phuc Hoang, and Hoai Thu Trinh. "Classification of hydrogeological structure along the Red River in the Hanoi area." Tạp chí Khoa học và Công nghệ Biển 21, no. 3 (September 30, 2021): 299–310. http://dx.doi.org/10.15625/1859-3097/16431.

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Hanoi city has abundant groundwater, supplemented by the surface water (mainly Red River) all year round, and the extensive shallow aquifers, which are easily exploited by large-diameter wells. There always exists some open hydrogeological windows in the Red River area with an open structure; therefore, the groundwater has a strained hydraulic relationship with the Red River water system Along the Red River from Ba Vi to the end of Phu Xuyen district, there are nine regions with three types and four sub-types of different hydrogeological structures. In particular, the sub-type I-A of the groundwater has a tight hydraulic correlation with the Red River since the hydrogeological structure of the Red River bottom includes three aquifers: Holocene (qh), upper Pleistocene (qp2), and lower Pleistocene (qp1) that constructs a hydraulic system. The sub-type I-B is characterized by the hydrogeological structure at the Red River bottom, including the aquitard in Vinh Phuc and two aquifers qp2 and qp1, which form a hydraulic system. The sub-type II-A is distinguished by the fact that the Red River crosses the aquifer qh; there are no aquitards between the aquifer qh and qp2 to form a hydraulic system; the aquitard separates the aquifer qp1. The sub-type II-B is identified by the fact that the Red River crossing the aquifer qh; there is an aquitard between the aquifer qh and qp2; there are no aquitards between the aquifer qp2 and qp1 so that can create a hydraulic system. Type III has a solid existence of both aquifers and aquitards; thus, the hydraulic relationship between the Red River and the aquifers qp2 versus qp1 is inferior.
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Murray, Titus A., and William L. Power. "A framework for inclusion of faults in coal seam gas risk assessments." APPEA Journal 61, no. 2 (2021): 695. http://dx.doi.org/10.1071/aj20066.

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Assessments for coal seam gas (CSG) projects may be required to consider the potential hydrological impacts of faults on surface and near-surface groundwater assets. This study presents three distinct end-member geological scenarios and outlines methods for characterising fault-related groundwater flow within a risk assessment context. Scenario 1: a regional aquitard isolates the water assets from the coal seams. There is little risk of leakage across the aquitard because there are no faults, or because the faults have maximum displacements less than the thickness of the aquitard. Scenario 2: a region-wide aquitard is not present, and the seams and the groundwater assets are located within the same groundwater system. In this scenario, CSG development may cause pressure changes to propagate parallel to the strike and dip of the fault in the fault damage zones. Scenario 3: regional aquitard(s) are present, but larger displacement faults breach the aquitards, allowing for possible combinations of across-fault connections between the different aquifers, and between aquifers and the coal seams. In this scenario, potential flow pathways between the groundwater and the CSG field need to be characterised using Allan Maps (fault plane profiles). It is essential to compare calculated flow rates of any new or potentially new flow pathways with the predevelopment flow regime. It is also important to recognise that flow estimates are best made using a Darcy’s law treatment for flow across fault zones and within the aquifers, and a Snow’s law treatment (discrete fracture network) for flow through fractures in fault damage zones.
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Burbey, Thomas J. "Parameter estimation of a multiple aquifer-aquitard system from a single extensometer record: Las Vegas, Nevada, USA." Proceedings of the International Association of Hydrological Sciences 382 (April 22, 2020): 51–56. http://dx.doi.org/10.5194/piahs-382-51-2020.

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Abstract. The purpose of this investigation is to develop a semi-analytical procedure for quantifying aquifer and aquitard properties from a single extensometer record in lieu of the time-consuming development of more complex numerical models to quantify and constrain these parameter values. Despite a limited 12-year record and the fact that water levels both decline and increase on an annual basis, estimates of both aquifer and aquitard parameters have been reasonably estimated at the Lorenzi extensometer site in Las Vegas Valley, Nevada when compared to the estimates developed numerically. The key factors that allow for accurate estimates of elastic and inelastic skeletal specific storage and hydraulic conductivity of the aquitards and elastic specific storage and hydraulic conductivity of the intervening aquifers is the presence of pumping cycles at multiple frequencies, and measured heads at all the aquifer units covered in the extensometer record and the inherent assumption that the aquitards have identical hydrologic characteristics and are homogeneous and isotropic. This latter assumption is also a usual limitation in numerical modelling of these settings because of the complex temporal head relationships occurring within the aquitards that are rarely, if ever, measured.
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Chuang, M. H., C. S. Huang, G. H. Li, and H. D. Yeh. "Groundwater fluctuations in heterogeneous coastal leaky aquifer systems." Hydrology and Earth System Sciences Discussions 7, no. 4 (July 9, 2010): 4473–99. http://dx.doi.org/10.5194/hessd-7-4473-2010.

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Abstract. In the past, the coastal leaky aquifer system, including an unconfined aquifer on the top, a confined aquifer at the bottom, and an aquitard in between, was commonly assumed to be homogeneous and of an infinite extent in the horizontal direction. The leaky aquifer system may however be nonhomogeneous and of a finite extent due to variations in depositional and post depositional processes. Thus, in the paper, the leaky aquifer system is divided into several horizontal regions for simulating the heterogeneity involved in both the confined aquifer and aquitard. A one-dimensional analytical model is developed for describing the head fluctuation in such a heterogeneous leaky aquifer system. The head of the upper unconfined aquifer is assumed to remain constant. It is found that both the length and location of the discontinuous aquitards presented in the coastal area have significant effects on the amplitude and phase shift of the head fluctuation in the confined aquifer. In addition, the influences of both the heterogeneous aquifer and aquitard on the spatial head distribution are investigated.
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Burt, Abigail. "Three-dimensional hydrostratigraphy of the Orangeville Moraine area, southwestern Ontario, Canada." Canadian Journal of Earth Sciences 55, no. 7 (July 2018): 802–28. http://dx.doi.org/10.1139/cjes-2017-0077.

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Regional-scale three-dimensional modelling of Quaternary sediments in the Orangeville Moraine area of southwestern Ontario has been completed as part of the Ontario Geological Survey groundwater initiative and provides an improved understanding of the glacial history and conceptual hydrostratigraphic framework for that region. Older (Marine Isotope Stage (MIS) 3–5) diamicton, glaciolacustrine, glaciofluvial, and rare nonglacial deposits forming regional aquitards and local aquifers are found in the northwestern part of the area. Catfish Creek Till, deposited during the Last Glacial Maximum (LGM) (MIS 2), forms a key aquitard and stratigraphic marker at depth. Diamicton, fine-textured glaciolacustrine sediments, and the gravel, sand, and silt conduit and subaqueous fan sediments that constitute the overlying Orangeville Moraine were deposited in an ice-walled lake formed between ice lobes during retreat from the LGM. Diamicton deposited during late-glacial ice margin fluctuations forms the upper aquitard unit and buries the edges of the moraine. The Orangeville Moraine is the largest aquifer in the area, and is partially confined by the upper tills. Thick fine-textured glaciolacustrine deposits, Catfish Creek Till, and older aquitards separate the moraine from bedrock aquifers across most of the area. Depending on hydraulic gradients, buried bedrock valleys with gravel and sand fills have the potential to recharge the bedrock aquifer.
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Chuang, M. H., C. S. Huang, G. H. Li, and H. D. Yeh. "Groundwater fluctuations in heterogeneous coastal leaky aquifer systems." Hydrology and Earth System Sciences 14, no. 10 (October 11, 2010): 1819–26. http://dx.doi.org/10.5194/hess-14-1819-2010.

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Abstract. In the past, the coastal leaky aquifer system, including two aquifers and an aquitard between them, was commonly assumed to be homogeneous and of infinite extent in the horizontal direction. The leaky aquifer system may however be heterogeneous and of finite extent due to variations in depositional and post depositional processes. In this paper, the leaky aquifer system is divided into several horizontal regions for the heterogeneous aquitard and underlying aquifer. A one-dimensional analytical model is developed for describing the head fluctuation in such a heterogeneous leaky aquifer system. The hydraulic head of the upper unconfined aquifer is assumed constant. It is found that both the length and location of the discontinuous aquitards presented in the coastal area have significant effects on the amplitude and phase shift of the head fluctuation in the lower aquifer. In addition, the influence of the formation heterogeneity on the spatial head distribution is also investigated.
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Burbey, Thomas J. "Extensometer forensics: what can the data really tell us?" Hydrogeology Journal 28, no. 2 (December 7, 2019): 637–55. http://dx.doi.org/10.1007/s10040-019-02060-6.

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AbstractExtensometer data have an advantage over satellite-based data for monitoring land subsidence in that extensometer data provide continuous measurements (hourly or better temporal resolution) at very high precision (several tens of microns) over a known depth interval; the latter is important for isolating groundwater pumping from other causes of land subsidence attributed to tectonics or eustatic adjustments in the Earth’s crust. This investigation aims to identify a semi-analytical procedure for quantifying aquifer and aquitard properties from a single extensometer record in lieu of the time-consuming development of more complex numerical models to quantify and constrain these parameter values. In spite of a limited 12-year record and the fact that water levels both decline and increase on an annual basis, this study successfully and reasonably estimated both aquifer and aquitard parameters at the Lorenzi extensometer site in Las Vegas Valley, Nevada (USA), when compared to the estimates developed numerically. The key factors that allow for estimates of elastic and inelastic skeletal-specific storage and hydraulic conductivity of the aquitards and elastic specific storage and hydraulic conductivity of the intervening aquifers is the presence of pumping cycles at multiple frequencies, and measured heads at all the aquifer units covered in the extensometer record. There is an inherent assumption that the aquitards possess the same hydrologic characteristics and are homogeneous and isotropic. This assumption is also a usual limitation in numerical modeling of these settings because of the complex temporal head relationships occurring within the aquitards that are rarely, if ever, measured.
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Husain, Muin M., John A. Cherry, Scott Fidler, and Shaun K. Frape. "On the long-term hydraulic gradient in the thick clayey aquitard in the Sarnia region, Ontario." Canadian Geotechnical Journal 35, no. 6 (December 1, 1998): 986–1003. http://dx.doi.org/10.1139/t98-057.

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Much of the southwestern part of Ontario between Lake Huron and Lake Erie has a thin freshwater aquifer overlain by an aquitard of Late Pleistocene clayey glaciolacustrine deposits and underlain by a thick Devonian shale aquitard. In a large area east of the St. Clair River, where the Quaternary aquitard is 30-50 m thick, groundwater of Pleistocene origin (identified by 18O and 2H signature) occurs in the aquifer and in the bottom part of the Quaternary aquitard. Numerous piezometer nests in the aquitard show a downward hydraulic gradient with depth. In some areas, the aquitard has downward gradients only in the upper part and upward gradient in the lower part, indicating a transient condition. The piezometer nests in the clayey aquitard also show an increase in Cl- concentration with depth. Long-term piezometer monitoring at two sites show a major shift in the aquitard hydraulic gradient since 1983 and a large rise in head in the underlying aquifer. Analyses of initial aquifer water levels, reported in well drilling records, indicate a large decline in the potentiometric surface of the aquifer between the 1940's and the 1970's followed by a recent rise in the surface in part of the region. This pattern is consistent with well drilling and water use records indicating that 7000 wells were installed in the aquifer in the three decades since 1940 and that groundwater use has greatly diminished in the past 10-15 years due to rural pipeline distribution of lake and river water. The hydraulic gradient in the aquitard is slowly adjusting to the rise in the aquifer potentiometric surface. One-dimensional solute transport modelling provides close matches to the vertical profiles of Cl- migrating upward from the aquifer since deglaciation, 15 000 - 18 000 years before present, by diffusion with little or no advection. The lack of advection indicates a near-neutral long-term hydraulic gradient. As the withdrawal rate of water from the aquifer continues to decline, it is expected that the hydraulic head in the aquitard in much of the area westward of the recharge area will continue to adjust for many decades.Key words: clay, aquitard, aquifer, water use, hydraulic gradient.
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Dissertations / Theses on the topic "Aquitard"

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Rashtchi, Ramina. "Assessing Aquitard Integrity: the Newmarket Till (Southern Ontario)." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/40439.

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The Newmarket Till is a regional aquitard in southern Ontario that overlies the Illinoian to Middle Wisconsinan Lower Sediments and is overlain by the Oak Ridges Moraine (ORM). Geological investigations have mapped the distribution of the till and it is understood that erosional channels, subsequently infilled with fluvial material, breach the till and may create enhanced hydraulic connection between overlying and underlying aquifers. However, little is known about the protective capability of the Newmarket Till where it is intact. This study used natural tracers to assess the extent of transport in the aquitard-aquifer system. Stable isotopes of water (δ18O and δ2H) showed a depletion trend versus depth. In the Newmarket Till most of the samples had isotope ratios similar to meteoric water data from the nearest location (Egbert, ON). The depleted values of δ18O in the Thorncliffe Formation suggest a remnant signature of early-Holocene precipitation (-16‰ at the depth of 60 m). Elevated levels of NO3- and Cl- were detected near the surface and because of the low permeability aquitard (Newmarket Till), they could not migrate to depth. Total extractable ammonium concentrations are ranging from 4.09 ppm from near the surface to 60 ppm in the lowest part of the Newmarket and then gradually increase to 514 ppm in the bottom of the Thorncliffe Formation. The combination of high NH4+ values and organic carbon content in the Thorncliffe Formation suggests a natural source from mineralization of organic N. The fractionation which happened between δ15Nsediment and δ15N-NH4 may have three explanations: (1) lighter isotopes diffuse faster than heavier ones, so the higher rate of diffusion can cause fractionation; (2) heavier isotopes partition to exchange sites, causing fractionation along the transport pathway; (3) dissociation of NH4+ to NH3 under anaerobic condition. Positive values for δ13C in groundwater in the Thorncliffe Formation are likely due to i) a contribution of carbonate mineral dissolution, and ii) methanogenesis - the Archea favor the lighter isotope of C (12C). Methanogenesis, therefore, enriches the δ13C-DIC was enriched; however, the δ13C in dissolved organic carbon (DOC) is depleted. These geochemical characteristics demonstrate a long residence time for the porewater in the system and indicate that the Newmarket till inhibits recharge of recent precipitation, thereby providing protection to the underlying aquifers from surface-derived contaminants.
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Sun, Dongmin. "Aquitard control of stream-aquifer interaction and flow to a horizontal well in coastal aquifers." Diss., Texas A&M University, 2005. http://hdl.handle.net/1969.1/4740.

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This dissertation is composed of three parts of major contributions: In Chapter II, we developed a new conceptual model and derived a new semi-analytical model for flow to a horizontal well beneath a water reservoir. Instead of treating the leakage from aquitard as a source term inside the aquifer which is called Hantush’s assumption (1964), we linked flows in aquitard and aquifer by the idea of continuity of flux and drawdown. The result in this chapter is compared with that of Zhan and Park in 2003 which Hantush’s assumption is adopted at various hydraulic and well configurations. It shows that Hantush’s assumption becomes inaccurate in regions where vertical velocity components are significant. In Chapter III, we deal with the interaction of an aquifer with two parallel surface water bodies such as two streams or canals. In this chapter, new closed-form analytical and semi-analytical solutions are acquired for the pumping induced dynamic interaction between two streams and ground water for two different cases. In the first case, the sediment layers separating the streams from the aquifer ground water do not exist. In the second case, the two low permeable layers are considered. The effect of aquitard and water right competition is addressed in this chapter. This model can be used for interpreting and deriving hydrologic parameters of aquitard and aquifer when pumping occurs between two channels. It can also be used to predict stream depletion which is essential for water management and ecology conservation. In Chapter IV, we investigated the three dimensional upconing due to a finite-length of horizontal well and its critical conditions. The results are compared with those of vertical wells. The critical condition which includes the critical rise and the critical time at a certain pumping rate depends on the well length, the initial interface location, the well location, and the pumping rate. Our results show that horizontal well might be a better tool for coastal groundwater resources development. In real field applications, installing long wells as shallow as possible is always desirable for sustaining long periods of pumping with significant rates.
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Bian, Aiguo. "On the solute transport in an aquifer-aquitard system." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1319.

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Gerber, Richard. "Hydrogeologic behaviour of the Northern till aquitard near Toronto, Ontario." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0016/NQ41156.pdf.

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White, Rachel A. "Organic contaminant transport through a thin clay aquitard influenced by palaeo-heterogeneities." Thesis, University of Birmingham, 2007. http://etheses.bham.ac.uk//id/eprint/104/.

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Processes controlling the transport of dissolved-phase organic solutes through clay aquitards have been investigated. The study was centred upon a former UK industrial facility at which dissolved-phase aromatic solutes contaminated, and in areas penetrated, a discrete clay bed underlying the site. The lacustrine clay stratum (1-2 m thick) at 6 m bgs located in a sand aquifer was cored in 13 locations and intensively sampled with depth (primarily benzene, ethylbenzene, toluene and styrene). Two types of hydrocarbon invasion profiles were identified; (i) diffusion-based invasion and (ii) advection-dominated invasion. The latter has been shown from extensive physicochemical analysis of the clay cores in the laboratory to be primarily through connected “palaeo-root” holes. Root connectivity has been shown at various scales (serial sectioning, x-ray tomography). The hydraulic conductivity in the case of the advection-based profiles was ~0.04 m/d, whereas in the case of the diffusion-based profiles it was much lower at approximately 3 x 10-5 m/d. Sorption characteristics of the clay have been investigated yielding Kd over 2.98 – 6.95 l/kg and Kf over 2.27- 6.89 μgkg-1/ μgl-1 for PCE and Kd over 0.49 l/kg and Kf over 0.57 μgkg-1/ μgl-1 for benzene. Freundlich isotherms over 3-4 orders of magnitude concentration were found to be near-linear, a phenomenon likely attributed to the occurrence of modern organic matter within the sediments. A 2-D (Fractran) numerical model confirmed that where the clay deposits are homogeneous or contain partially penetrating root holes, slow diffusion dominated invasion will offer significant protection to the lower aquifer with breakthrough times through 1 m of clay of 40 years. Conversely, where the clays contain fully penetrating root holes, advection through the root holes causes much faster contaminant penetration. Matrix diffusion from preferential flowpaths causes contaminant to become distributed completely through the clay stratum. Discharge from the bottom of the clay stratum through root holes will be associated with a significant flux of dissolved-phase contaminant (where 30% of clay is rooted with 7.5 cm spaced root holes, ~0.25 mm aperture, contaminant flux is 0.134 g/m2/d) causing contamination of the lower aquifer. The accumulation of mass in the clay stratum is likely to cause prolonged contamination of the adjacent aquifers should the original source concentrations decrease. Indeed, evidence for such reverse diffusion at this site has been observed in one of the profiles. A 3-D code using high resolution data from x-ray tomography was developed to enable modelling of contaminant transport in finely characterised root holes.
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Timms, Wendy Amanda Civil &amp Environmental Engineering Faculty of Engineering UNSW. "The importance of aquitard windows in the development of alluvial groundwater systems : Lower Murrumbidgee, Australia." Awarded by:University of New South Wales. School of Civil and Environmental Engineering, 2001. http://handle.unsw.edu.au/1959.4/18671.

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Variable groundwater quality in complex aquifer-aquitard systems presents a challenge for sustainable groundwater development. In the Lower Murrumbidgee alluvial fan of the Murray-Darling Basin in semi arid inland Australia, shallow groundwater is saline (12000 µ S/cm) and locally contaminated by nitrate. Deep fresh aquifers (150 µ S/cm), developed as an irrigation water supply, were thought to be protected from downwards leakage by laterally extensive aquitards. However, hydrochemical sampling, augmented by historic data, revealed that aquifer salinisation (400 to 4000 µ S/cm) had occurred at some sites to 50 m depth since the mid 1980s. Aquitard windows, landscape depositional features at a scale of 10s to 100s of metres which are rarely detected by conventional investigations, were proposed as conduits for rapid downwards leakage in stressed systems. Intensive research was conducted at the Tubbo site where downhole geophysical logging and minimally disturbed cores were used to describe a saline clayey silt to 15m depth, an indurated clayey sand and 2 deep deposits of hard clayey silt. Fracturing was inferred by the scale dependency of aquitard permeability (Kv 10E-11 to 10E-6 m/s). Lithological variation near the surface was delineated by electrical imaging which revealed a 40m wide aquitard window beneath a veneer of smectite clay. Intensive monitoring of groundwater pressures in six piezometers (23-96 m depth) near the Tubbo irrigation bore and two other peizometers upgradient, indicated that the indurated clayey sand formed an effective hydraulic barrier but the deep silty deposits were spatially discontinuous. Groundwater samples were collected before, three times during, and after the 1998-99 irrigation season. A large, but delayed TDS increase occurred in the shallow aquifer and small pulses of saline water were sustained in the middle aquifer but shortlived in the deep aquifer. Hydrochemical and isotopic data dC-13, dH-2, dO-18, C-14 and H-3) showed the middle aquifer mixing with the deep aquifer, though retaining the signature of a palaeowater. Hydrochemical changes were accounted for with PHREEQC inverse mass balance models for the shallow aquifer. Mixing of aquifer water with 20-70% saline porewater from the upper aquitard occurred, together with ion exchange and NaCl dissolution. Based on an axisymmetric radial FEFLOW model, 5-30% of the volume pumped was accounted for by vertical leakage from the middle aquifer. Leakage from the shallow aquifer was small but significant, as it allowed high salinity water to migrate. Permeability and compressible storage measurements (Ss 10E-5 to 10E-4 /m) were used to constrain model calibration, and to show that direct mixing occurred mainly via aquitard windows at depth, and between the shallow and middle aquifers via leaky boreholes. Fracture flow and aquifer-aquitard interaction by diffusion were of secondary importance.
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Wang, Ya, and 王亚. "Isotopic and hydrogeochemical studies of the coast aquifer-aquitard system in the Pearl River Delta, China." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B46593597.

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Liu, Kun, and 刘琨. "Geochemical and geomicrobiological studies of the ammonium-rich aquifer-aquitard system in the Pearl River Delta, China." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/196494.

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An aquitard is not only a confining layer in the aquifer-aquitard system, but also a functional complex for nutrient reservation and microorganism inhabitation. Geochemical characteristics and geomicrobial processes in aquitards play an important role in groundwater quality, and should be well studied. The Pearl River Delta is dominated by clay-rich aquitards and was intensively influenced by Holocene transgression. In this thesis, the aquifer-aquitard system in the PRD was studied from various perspectives including geophysics, geochemistry and geomicrobiology. Sediment and groundwater samples were taken from representative locations in the PRD at different lithological units. Particle size distribution, computed axial tomography, optically stimulated luminescence dating and scanning electron microscopy were analyzed to understand the geophysical properties. Concentrations of major ions and abundances of environmental isotopes were measured for geochemical analysis. Bacterial 16S rRNA gene clone libraries were constructed to analyze microbial identifications and community structures in different strata. Gene abundances of anammox 16S and bacteria amoA in both sediment and groundwater samples were quantitatively analyzed with 15N isotope at the same depth. The mixing process of seawater and river water was the dominant factor controlling the isotopic and chemical characterizes of groundwater in the system. Isotopic fractionation in the aquitards was majorly controlled by chemical and biological reactions other than diffusion. Chemical pattern in this system was mainly controlled by topography and sea level in the Holocene. Independent sedimentary centers of strong reducing environment were located in the depressions controlled by fault zones, and generated massive amount of pyrite minerals in the sediment and NH4+ in the groundwater. The sea level and depositional environment in the Holocene determined the physical structures of the sediment and seawater/river-water ratio in the estuary. Isotopic research also demonstrated that South Asia Monsoon was the major source of atmospheric precipitation in the PRD. Bacterial species in the PRD sediment were identified. Canonical correspondence analysis between bacterial linages and environment factors showed that community structures were significantly modified by geological conditions. High bacterial diversity was observed in samples from the Holocene aquitard M1 and aquifer T1, while in the older aquitard M2 and basal aquifer T2, the bacterial diversity was much lower. Chloroflexi, γ-proteobacteria and δ-proteobacteria were the dominant phyla in the aquitard sediment. β-proteobacteria was the dominant phylum in sediment which was strongly influenced by fresh water. Anammox was the controlling biochemical process in microbial-derived ammonium loss, as demonstrated by gene abundance coupling with 15N isotope and ammonium concentration. The 16S gene abundance of anammox bacteria ranged from approximately 105 to 106 copies/g in the aquitard sediment, and ranged from 104 to 105 copies/g in aquifers. amoA gene abundance was 1-2 orders lower than anammox bacteria 16S in aquitard sediment, but in aquifers, the gene abundances of amoA and anammox 16S were similar. Interface between aquifer and aquitard was demonstrated as biochemically enhanced zone. The results of this study significantly benefited the understanding of geochemistry and microbiology in the aquifer-aquitard system, and showed directions for future work on geomicrobiology in aquitards.
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Cabaret, Olivier. "Caractérisation physique et approche numérique du rôle des aquitards dans les systèmes aquifères multicouches - Application au complexe tertiaire nord-aquitain." Phd thesis, Université Michel de Montaigne - Bordeaux III, 2011. http://tel.archives-ouvertes.fr/tel-00626915.

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L'élaboration de modèles hydrodynamiques à des fins de gestion rationnelle des aquifères et des prélèvements à une échelle régionale nécessite la connaissance du fonctionnement hydrodynamique des aquitards.La caractérisation de ces formations semi-perméables implique de déterminer leurs propriétés géologiques, hydrodynamiques et leur degré d'hétérogénéité. La région de Bordeaux, soumise à d'importants prélèvements, sert ici de support d'étude pour appréhender le rôle des aquitards dans le fonctionnement hydrodynamique d'un multicouche complexe. La caractérisation de ces formations semi-perméables a été obtenue au travers d'approches directes, indirectes et numériques. L'outil diagraphique a permis une réinterprétation de la géologie et a abouti à la mise à jour de la géométrie hydro-géologique du domaine d'étude ainsi qu'à une nouvelle organisation verticale des unités aquifères et aquitards. Les propriétés hydrodynamiques des aquitards ont été approchées grâce à la réalisation d'un forage expérimental dédié à l'étude d'une éponte. Des mesures pétrophysiques et l'analyse des séries temporelles enregistrées en différents niveaux de l'aquitard ont été effectuées et ont fourni des estimations des paramètres de conductivité hydraulique et d'emmagasinement spécifique de l'aquitard. Enfin, l'approche quantitative du rôle des aquitards dans le fonctionnement hydrodynamique du système aquifère a été réalisée à l'aide d'un modèle hydrogéologique. Celui-ci prend en compte la géométrie revisitée, issue des données diagraphiques, et intègre les valeurs des paramètres hydrodynamiques obtenues par les mesures de laboratoire et in situ. Le modèle a été utilisé pour préciser les flux de drainance au sein du système multicouche ainsi que leurs proportions relatives. Les résultats démontrent l'impact et le rôle d'un horizon semi-perméable au sein d'un aquitard puissant. In fine, l'intégration des hétérogénéités d'un aquitard s'avère obligatoire dans l'élaboration d'outils de gestion raisonnée (quantitative et qualitative) à court et long terme des ressources en eau souterraines d'un système aquifère multicouche complexe.
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Li, Yanhua, and Yanhua Li. "Numerical evaluation of analytical solution for a 5-layer aquifer -aquitard system with application to the Oxnard Basin in California." Thesis, The University of Arizona, 2006. http://hdl.handle.net/10150/626928.

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In nature, a pumping aquifer is not an independent hydrological unit. The confining beds typically have some permeability rendering the aquifer leaky or slight leaky. Together they make up a multi-aquifer system. This work is an attempt to investigate transient fluid flow to a well in a 5-layer system based on former work of Neumann (1968). The latter author developed an analytical solution for drawdown in a five-layer system with three aquifers separated by two aquitards, and a well of infinitesimal radius completely penetrates one aquifer and discharges at a constant rate. Numerical evaluation has been limited to a two-aquifer system (Neuman, 1968). In this work, numerical Laplace transform inversion is utilized to evaluate the five-layer analytical solutions in terms of dimensionless variables. The numerical results are presented in graphical form and compared to those of the two-aquifer solution (Neuman, 1968). The five-layer solution is then used to reinterpret two long-term pumping tests conducted near Oxnard, California. The hydraulic properties of each aquifer and aquitard are estimated through optimization using the inverse code PEST (Doherty, 2001). The results confirm the accuracy of the ratio method of Neuman and Witherspoon (1972), which can calculate the permeability of aquitard if the specific storage of aquitard is known.
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Books on the topic "Aquitard"

1

Bradbury, K. R. Contaminant transport through aquitards: Technical guidance for aquitard assessment. Denver, Colo: Awwa Research Foundation, 2006.

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2

Kayane, Isamu. Four-dimensional response of the aquifer and aquitard system in Tokyo to groundwater withdrawal and regulation. Tsukuba, Japan: Environmental Research Center, the University of Tsukuba, 1993.

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Kayane, Isamu. Four-dimensional response of the aquifer and aquitard system in Tokyo to groundwater withdrawal and regulation. Tsukuba, Japan: Environmental Research Center, the University of Tsukuba, 1993.

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Sesto, Prete, and Desgraves Louis, eds. Ausone, humaniste aquitain. Bordeaux: Société des bibliophiles de Guyenne, 1986.

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Jornadas Euskadi-Aquitania ( 1997 Bilbao, Spain). La construcción del espacio vasco-aquitano. Edited by Borja Antón, Letamendia Francisco 1944-, and Sodupe Kepa. [Bilbao]: Universidad del País Vasco, 1998.

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Pavelko, Michael T. Estimates of hydraulic properties from a one-dimensional numerical model of vertical aquifer-system deformation, Lorenzi site, Las Vegas, Nevada. Carson City, Nev: U.S. Dept. of the Interior, U.S. Geological Survey, 2004.

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Pavelko, Michael T. Estimates of hydraulic properties from a one-dimensional numerical model of vertical aquifer-system deformation, Lorenzi site, Las Vegas, Nevada. Carson City, Nev: U.S. Dept. of the Interior, U.S. Geological Survey, 2004.

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Clus-Auby, Christine. La gestion de l'érosion des côtes: L'exemple aquitain. Pessac: Presses universitaires de Bordeaux, 2003.

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Beech, George. Le Conventum (vers 1030): Un précurseur aquitain des premières épopées. Genève: Libr. Droz, 1995.

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Glück, Denise. Dictionnaire du mobilier sud-aquitain: Gers, Hautes-Pyrénées, Landes, Pyrénées-Atlantiques. Paris: Editions Bonneton, 1995.

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Book chapters on the topic "Aquitard"

1

Guerra, Maurizio. "Aquitard." In Selective Neck Dissection for Oral Cancer, 1–2. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-12127-7_18-1.

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Guerra, Maurizio. "Aquitard." In Encyclopedia of Earth Sciences Series, 27–28. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-73568-9_18.

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Maliva, Robert G. "Evaluation of Aquifer Storage and Aquitard Properties." In Springer Hydrogeology, 445–65. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-32137-0_14.

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Liu, Zhong-Yu, Jin-Chao Yue, and Li-Yun Sun. "One-Dimensional Consolidation Of Aquitard Considering Non-Darcy Flow." In Advances in Environmental Geotechnics, 430–34. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-04460-1_33.

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Ball, William P., and Chongxuan Liu. "Diffusion-Limited Contamination and Decontamination in a Layered Aquitard: Forensic and Predictive Analysis of Field Data." In Resource Recovery, Confinement, and Remediation of Environmental Hazards, 179–94. New York, NY: Springer New York, 2002. http://dx.doi.org/10.1007/978-1-4613-0037-3_10.

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Dolbeau, François. "Un légendier perdu, de type aquitain." In Le légendier de Moissac et la culture hagiographique méridionale autour de l’an mil, 219–30. Turnhout, Belgium: Brepols Publishers, 2018. http://dx.doi.org/10.1484/m.hag-eb.5.116283.

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Wang, Chi-Yuen, and Michael Manga. "Groundwater and Stream Composition." In Lecture Notes in Earth System Sciences, 257–87. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-64308-9_9.

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AbstractChanges of groundwater chemistry have long been observed. We review some studies of the earthquake-induced changes of groundwater and streamflow composition. When data are relatively abundant and the hydrogeology is relatively simple, the observed changes may provide valuable insight into earthquake-induced changes of hydrogeological processes. Progress in this aspect, however, has been slow not only because systematic measurements are scare but also because of the distribution of chemical sources and sinks in the crust are often complex and unknown. Most changes are consistent with the model of earthquake-enhanced groundwater transport through basin-wide or local enhanced permeability caused by earthquake-induced breaching of hydrologic barriers such as aquitards, connecting otherwise isolated aquifers or other fluid sources, leading to fluid source switching and/or mixing. Because the interpretation of earthquake-induced groundwater and stream compositions is often under-constrained, multi-disciplinary approaches may be needed to provide a better constrained interpretation of the observed changes.
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Falta, Ronald W. "Dissolved Chemical Discharge from Fractured Clay Aquitards Contaminated by DNAPLS." In Dynamics of Fluids and Transport in Fractured Rock, 165–74. Washington, D. C.: American Geophysical Union, 2013. http://dx.doi.org/10.1029/162gm15.

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Cames, Pierre. "Eth substrat basco-aquitan en gascon. Torn d’orizont dera question e problèmas inerents." In Publications de l'Association Internationale d'Etudes Occitanes, 243–61. Turnhout, Belgium: Brepols Publishers, 2022. http://dx.doi.org/10.1484/m.paieo-eb.5.126425.

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"aquitard." In Dictionary Geotechnical Engineering/Wörterbuch GeoTechnik, 62. Berlin, Heidelberg: Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-41714-6_12415.

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Conference papers on the topic "Aquitard"

1

Murray, Titus, and William L. Power. "Conceptual Framework for Hydrologic Modelling of Faults." In PESA Symposium Qld 2022. PESA, 2022. http://dx.doi.org/10.36404/lmyz2214.

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Unconventional oil and gas developments may require considering the potential hydrological impacts of faults on near-surface groundwater assets. It is vital that faults are represented appropriately. There are several examples where faults have been invoked as part of “Straw Man” arguments to oppose development (Currell et. al. 2017 and Iverach et. al. 2020). The processes of dewatering and hydraulic fracture stimulation may generate preferential pathways for flow that impact aquifers and groundwater dependant ecosystems. As part of this, a clear framework for the assessment of the impact of faults has been provided in Murray and Power 2021. This study presents three distinct end-member geological scenarios and outlines methods for characterising faultrelated groundwater flow within a risk assessment context. 1) Regional aquitard isolates aquifer from development. Low risk of leakage across the aquitard because there are no faults, or the faults have displacements less than the thickness of the aquitard. 2) Region-wide aquitard is not present, the development and the groundwater assets are within the same groundwater system. CSG development may cause pressure to propagate parallel to the strike and dip of the fault in the fault damage zones. 3) Regional aquitard(s) are present, but larger displacement faults breach the aquitards, allowing for possible combinations of across-fault connections between the different aquifers, and between aquifers and the coal seams. In this scenario, potential flow pathways between the groundwater and the development need to be characterised using Allan Maps (fault plane profiles).
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Victor B. Ella, Stewart W. Melvin, and Rameshwar S. Kanwar. "Nitrate-nitrogen Loading Rates in a Glacial Till Aquitard." In 2002 Chicago, IL July 28-31, 2002. St. Joseph, MI: American Society of Agricultural and Biological Engineers, 2002. http://dx.doi.org/10.13031/2013.9528.

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Lightfoot, Alexandra, and Rolf Kipfer. "Aquitard constraints on degassing in an arsenic contaminated aquifer." In Goldschmidt2021. France: European Association of Geochemistry, 2021. http://dx.doi.org/10.7185/gold2021.7260.

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Young, Roger A., and Jingsheng Sun. "3‐D representation of aquitard topography using ground‐penetrating radar." In SEG Technical Program Expanded Abstracts 1995. Society of Exploration Geophysicists, 1995. http://dx.doi.org/10.1190/1.1887444.

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Cardimona, Steve, Katharine Kadinsky‐Cade, and William Clement. "Coincident ground penetrating radar and seismic imaging of an aquitard boundary." In SEG Technical Program Expanded Abstracts 1996. Society of Exploration Geophysicists, 1996. http://dx.doi.org/10.1190/1.1826781.

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Steelman, Colby M., Adam Smiarowski, Oliver Conway-White, Hernan Ugalde, Emmanuelle Arnaud, and Beth L. Parker. "ENHANCING SOURCE-WATER MANAGEMENT THROUGH AIRBORNE ELECTROMAGENTIC IMAGING OF COMPLEX AQUIFER-AQUITARD SEQUENCES." In Symposium on the Application of Geophysics to Engineering and Environmental Problems 2019. Society of Exploration Geophysicists and Environment and Engineering Geophysical Society, 2019. http://dx.doi.org/10.4133/sageep.32-028.

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Meyer, Jessica R., Beth L. Parker, Lucas A. F. S. Ribeiro, Chris A. Morgan, and Anthony C. Runkel. "HIGH RESOLUTION HEAD PROFILES REVEAL NEW INSIGHTS ABOUT AQUITARD MECHANISMS IN SEDIMENTARY ROCKS." In 52nd Annual North-Central GSA Section Meeting - 2018. Geological Society of America, 2018. http://dx.doi.org/10.1130/abs/2018nc-311755.

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Mazurek, M., A. de Haller, and A. Gautschi. "Pore-water Evolution in the Shale-rich Aquitard Sequence at Mont Terri, Switzerland." In Fifth EAGE Shale Workshop. Netherlands: EAGE Publications BV, 2016. http://dx.doi.org/10.3997/2214-4609.201600417.

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Hart, David J., and Curtis L. Thomas. "Using Time‐Domain Electromagnetics to Map the Transition of an Aquifer to an Aquitard." In Symposium on the Application of Geophysics to Engineering and Environmental Problems 2005. Environment and Engineering Geophysical Society, 2005. http://dx.doi.org/10.4133/1.2923531.

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Kjarsgaard, Bruce, Ross D. Knight, H. A. J. Russell, David Sharpe, Heather Crow, and Laura Olson. "NEWMARKET TILL AQUITARD: OPTIMUM GRAIN PACKING, WITH A PORE FILLING CEMENT GENERATES PSEUDO-CONCRETE." In GSA Annual Meeting in Denver, Colorado, USA - 2016. Geological Society of America, 2016. http://dx.doi.org/10.1130/abs/2016am-285066.

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Reports on the topic "Aquitard"

1

Kjarsgaard, B. A., D. R. Sharpe, R. D. Knight, D. Stepner, and H. A J Russell. Newmarket Till aquitard: optimum grain packing with a pore-filling calcite-rich cement. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 2018. http://dx.doi.org/10.4095/306539.

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Kjarsgaard, B. A., R. D. Knight, H. A. J. Russell, D. R. Sharpe, H. Crow, and L. Olson. Newmarket Till aquitard: optimum grain packing with a pore-filling calcite-rich cement. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 2017. http://dx.doi.org/10.4095/299778.

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Desbarats, A. J., M. J. Hinton, C. E. Logan, and D. R. Sharpe. Geostatistical mapping of leakance in a regional aquitard, Oak Ridges Moraine area, Ontario. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 2000. http://dx.doi.org/10.4095/220152.

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Sharpe, D. R., H. A. J. Russell, and C. Logan. Geological characterization of a regional aquitard: Newmarket Till, Oak Ridges Moraine area, southern Ontario. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 2002. http://dx.doi.org/10.4095/216708.

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Knight, R. D., M. Moroz, and H. A. J. Russell. Geochemistry of a Champlain Sea aquitard, Kinburn, Ontario: portable XRF analysis and fusion chemistry. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 2012. http://dx.doi.org/10.4095/290969.

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Deeds, Jake, and John Bradford. CHARACTERIZATION OF AN AQUITARD AND DIRECT DETECTION OF LNAPL AT HILL AIR FORCE BASE USING GPR AVO AND MIGRATION VELOCITY ANALYSES. Office of Scientific and Technical Information (OSTI), June 2002. http://dx.doi.org/10.2172/833500.

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Hamblin, A. P. Detailed measured sections, bedrock aquifer/aquitard facies and potential bedrock aquifer systems of the Upper Cretaceous Nanaimo Group, Nanaimo Lowland, eastern Vancouver Island, British Columbia, Canada. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 2015. http://dx.doi.org/10.4095/296979.

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Carter, T. R., C. E. Logan, J K Clark, H. A. J. Russell, E. H. Priebe, and S. Sun. A three-dimensional bedrock hydrostratigraphic model of southern Ontario. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/331098.

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A hydrostratigraphic framework has been developed for southern Ontario consisting of 15 hydrostratigraphic units and 3 regional hydrochemical regimes. Using this framework, the 54 layer 3-D lithostratigraphic model has been converted into a 15 layer 3-D hydrostratigraphic model. Layers are expressed as either aquifer or aquitard based principally on hydrogeologic characteristics, in particular the permeability and the occurrence/absence of groundwater when intersected by a water well or petroleum well. Hydrostratigraphic aquifer units are sub-divided into up to three distinct hydrochemical regimes: brines (deep), brackish-saline sulphur water (intermediate), and fresh (shallow). The hydrostratigraphic unit assignment provides a standard nomenclature and definition for regional flow modelling of potable water and deeper fluids. Included in the model are: 1) 3-D hydrostratigraphic units, 2) 3-D hydrochemical fluid zones within aquifers, 3) 3-D representations of oil and natural gas reservoirs which form an integral part of the intermediate to deep groundwater regimes, 4) 3-D fluid level surfaces for deep Cambrian brines, for brines and fresh to sulphurous groundwater in the Guelph Aquifer, and the fresh to sulphurous groundwater of the Bass Islands Aquifer and Lucas-Dundee Aquifer, 5) inferred shallow karst, 6) base of fresh water, 7) Lockport Group TDS, and 8) the 3-D lithostratigraphy. The 3-D hydrostratigraphic model is derived from the lithostratigraphic layers of the published 3-D geological model. It is constructed using Leapfrog Works at 400 m grid scale and is distributed in a proprietary format with free viewer software as well as industry standard formats.
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Rashtchi, R., T. Al, J. Cornett, R. Gerber, and H. A J Russell. Assessing the integrity of aquitards: the Newmarket Till at Ajax. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 2018. http://dx.doi.org/10.4095/306570.

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Baker, Ralph S., and Uwe Hiester. Large-Scale Physical Models of Thermal Remediation of DNAPL Source Zones in Aquitards. Fort Belvoir, VA: Defense Technical Information Center, May 2009. http://dx.doi.org/10.21236/ada520587.

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