Browsing by Author "Bentley, Laurence R."

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    Characterization of water fluxes at a trench & gate groundwater remediation site
    (1999) Thomas, David Andrew; Bentley, Laurence R.
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    Cuantificacion de la recarga por inundaciones en el sistema acuifero de la comunidad de Cliza
    (2015) Huarita, Mario; Bentley, Laurence R.; Hernández Oña, Ing. Corina
    Las aguas subterráneas son una fuente imprescindible para el abastecimiento de agua en zonas donde existe escases de agua superficial. Es un elemento clave para el desarrollo de las actividades sociales y económicas como la agricultura e industria en zonas urbanas y rurales. Los acuíferos son un factor importante en el estudio de la hidrogeología. La determinación de cuánta agua ingresa al acuífero es crucial para un buen uso del agua subterránea en el futuro. El proyecto describe el proceso para la obtención del valor de recarga existente en el acuífero de Cliza por las inundaciones existentes, al no contar el municipio con este parámetro importante para el correcto uso del agua subterránea y así evitar su desperdicio. Se determinaron cinco zonas inundadas(A1, A2, A3, A4, y A5) cada una con diferentes características. Primeramente con la facilitación de registros de la estación de Cliza. Se determinaron valores de precipitaciones medias mensuales que se tomaron como aportes a la zona inundada. Posteriormente con la facilitación de datos de GPS para la delimitación de las zonas inundadas se determinaron las áreas y volúmenes de las zonas para obtener el aporte existente por el río Siches. De esta manera se determinó que las zonas inundadas eran abastecidas por precipitación y por desborde de río. Una vez determinados los aportes, se obtuvieron valores de parámetros que no aportan al abastecimiento de la zona inundada ni a la recarga del acuífero refiriéndonos más propiamente a la Evapotranspiración Potencial Real existente en la zona, definida por el método de Thornwaite y Mather. También a la Escorrentía de la zona, parámetro muy importante el cual necesita para su determinación los datos de tasas de infiltración del terreno, los cuales fueron obtenidos en campo por los métodos del Permeámetro de Guelph y las Anillas de infiltración. Por último se estableció el cambio de almacenamiento en la zona no saturada. La obtención de estos datos tenía como fin utilizar el método del Balance Hídrico propuesto por Thornwaite y Mather para hallar los valores de recarga en el acuífero de Cliza. Se llegó a la conclusión que el aporte de las cinco zonas inundadas al acuífero es mínimo, esto debido a las características del terreno y su alto grado de impermeabilidad. Cada una de las zonas demostró tener un terreno franco arcillo arenoso el cual evita que el agua de inundación ingrese al acuífero.
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    Electrical Imaging of a Shallow Free-Phase Stray Gas Plume from an Abandoned Exploration Well
    (2021-11-22) Lagasca, Patrick A.; Ryan, M. Cathryn; Bentley, Laurence R.
    Geophysical imaging of free-phase gas (FPG) within aquifers is an emerging method for understanding the mechanisms controlling stray gas migration from oil and gas wells. Crystal Geyser is an unsealed and partially cased well that transports stray CO2 gas to the shallow subsurface. Accumulations of subsurface CO2 FPG near Crystal Geyser have been inferred, but the actual location and dimensions remained unclear. Here, the subsurface FPG distribution surrounding Crystal Geyser was characterized by interpreting 2D electrical resistivity images with previous drilling records and field mapping. An approximately 70-metre-wide FPG plume was located laterally between Crystal Geyser’s conduit and the Little Grand Wash Fault. The FPG plume spanned the vertical extent of approximately 20 to 55 metres below the ground surface, located within the Slick Rock Member sandstone with the relatively low permeability Earthy Member silty sandstone acting as a caprock. The FPG plume was identified from an anomalously high resistivity zone within the Slick Rock Member that was not caused by lateral lithofacies changes or fault displacement. The conceptual FPG migration pathways beneath Crystal Geyser are presented, based on the interpreted FPG distribution from the electrical resistivity images combined with previous site characterization and the principles of buoyant FPG migration. FPG accumulates within the Slick Rock Member by buoyant up-dip migration beneath siltstone capillary barriers of the Earthy Member. FPG leaks to the ground surface within high permeability preferential pathways along the Little Grand Wash Fault and the conduit of Crystal Geyser.
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    Evaluating tile drainage systems as a method of salt remediation in Alberta
    (2008) Smith, Amanda Dawn; Bentley, Laurence R.
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    Geosystem modeling with Markov chains and simulated annealing
    (1997) Parks, Kevin; Bentley, Laurence R.
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    Groundwater recharge in the Canadian Prairies: mechanisms, constraints, and rates
    (2019-01-08) Pavlovskii, Igor; Hayashi, Masaki; Bentley, Laurence R.; Sjogren, Darren Boyd; Cey, Edwin E.; Ireson, Andrew M.
    A combination of dry climate and extensive cover of low-permeability sediments reduces groundwater recharge in the Canadian Prairies to just a few percent of annual precipitation. Such recharge scarcity increases the importance of knowing recharge rates for adequate management of water resources and, simultaneously, complicates recharge rate evaluation. The present study addresses this problem by using a combination of surface conditions monitoring, geochemical methods, and remote sensing to identify recharge mechanisms and physiographic constraints on recharge, and to quantify recharge rates. The analysis of stable-isotopic data shows that groundwater recharge in the Canadian Prairies is dominated by the snow-melt-driven depression-focussed recharge pathway. The potential recharge through this pathway is limited by the volume of snow-melt that is retained within topographic depressions and, thus, is mostly constrained by just two factors: runoff generation and the available depression storage capacity. The latter is shown to be generally comparable in magnitude with typical runoff values and, thus, serves as a hard upper limit on recharge rates. The identified link between depression storage capacity values and specific types of surficial sediments allows to estimate limit on groundwater recharge rate based on the surficial geology maps. Unlike depression storage capacity, the limit on recharge rate associated with runoff volume varies over time and is sensitive to the atmospheric forcing with mid-winter melts, which are shown to be an important factor affecting both volume of snow-melt runoff and timing of groundwater recharge. The regional recharge rates are consistent with identified limiting factors and are estimated to be 8─14 mm per year in the parkland ecoregion and 3.5─6 mm per year in the grassland ecoregion.
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    Improving groundwater flow model parametrization techniques
    (2020-11-13) Abdrakhimova, Polina; Bentley, Laurence R.; Hayashi, Masaki; Cey, Edwin E.; Hassanzadeh, Hassan; Ferguson, Grant A. G.
    Numerical modeling of groundwater flow is a powerful tool that can assist in hydrogeological analysis and understanding of groundwater system behavior. However, its results are highly dependent on the proper model parameterization (often, at least partially achieved through calibration). The situation is further complicated in transient groundwater models requiring calibration of the additional parameters such as specific storage in addition to standard hydraulic conductivity. Another complication of the transient modelling is a need to define transient boundary conditions. In settings with seasonal recharge variations, the spatial and temporal variation in the recharge boundary conditions becomes an important part of the problem setting. Simultaneous calibration of hydrogeological properties (hydraulic conductivity, specific storage) and recharge is a challenging problem prone to non-uniqueness: similar model results achieved by different combinations of recharge, specific storage and transmissivity. The objective of this study is to improve hydrogeological model parametrization, with the focus on hydrogeological properties governing groundwater system response to transient forcing. It highlights multiple ways of estimating specific storage, which allows to provide better constraints for the calibration problem. In particular, it proposes a new method of specific storage estimation using seismic velocities and compares it with the results of conventional pumping test analysis and analysis of a water level response to atmospheric pressure fluctuations and Earth tides. The resulting values of specific storage have shown reasonable agreement between methods for a sandstone unit of the Paskapoo Formation: the estimates from seismic velocity and water level analyses ranged from 1.25∙10-5 1/m to 1.6∙10-5 1/m, while the specific storage estimate from pumping test was 4.6∙10-5 1/m. This finding suggests that seismic velocity method can be used to evaluate spatial variation of specific storage or to augment the inversion as a part of parameter constraints or regularization term. This study also identified multiple avenues of extracting additional information about aquifers from conventional datasets in order to further reduce the uncertainty. The proposed new framework uses integration of multiple methods for inversion of pumping test in a heterogeneous aquifer. Its application at the study site has shown that the flow from the aquitards bounding the aquifer are a major component of a flow budget during even multi-day pumping test highlighting the limitations of extrapolating pumping test results to long-term transient response without accounting for aquifer geometry and properties of the bounding units. In addition, this study investigated sensitivity of modeled groundwater levels to transient recharge properties. The spatially-variable transient recharge was generated by Versatile Soil Moisture Budget (VSMB) model based on atmospheric forcing and was applied as a specified flux to the upper boundary of a watershed-scale 3-D groundwater model. The model reasonably replicated both observed groundwater level dynamics and 10-year mean baseflow of 20.54 mm/a (modeled recharge value was 23.84 mm/a). It was demonstrated that both seasonal groundwater level rise and long-term trends simultaneously reflect magnitude and timing of the recharge; seasonal propagation of a recharge pulse through the aquifer was dependent on hydraulic diffusivity (a ratio of hydraulic conductivity to specific storage). These findings imply that a detailed transient recharge signal is needed for both forward and inverse groundwater modeling.
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    Improving Reservoir Simulation with Time-lapse Seismic Surveys
    (2010) Zhang, John Jianlin; Bentley, Laurence R.; Settari, Antonin; Krebes, Edward S.
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    Integration of seismic methods with reservoir simulation, Pikes Peak Heavy Oil Field, Saskatchewan
    (2005) Zou, Ying; Bentley, Laurence R.; Lines, Laurence R.
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    Mapping organic contaminant plumes in groundwater using spontaneous potentials
    (2011) Forté, Sarah; Bentley, Laurence R.
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    Measurement and Simulation of Preferential Flow in Frozen Soils
    (2019-11) Mohammed, Aaron A.; Cey, Edwin E.; Hayashi, Masaki; Lemieux, Jean-Michel; Bentley, Laurence R.; Wong, Ron
    The infiltrability of frozen soils strongly influences the partitioning of snowmelt and hydrological functioning of cold regions. Preferential flow in macropores may enhance infiltration into frozen soil, but flow dynamics are complicated by coupled water and heat transfer processes. Field studies were conducted in the Canadian Prairies to evaluate the dominant mechanisms controlling preferential flow in frozen soils, and the combined influence of soil freeze-thaw and preferential flow on snowmelt-driven infiltration and groundwater recharge. Results showed that preferential flow enabled relatively large amounts of snowmelt infiltration when the soil was still frozen, but that refreezing of infiltrated meltwater during winter snowmelt events progressively reduced soil infiltrability and enhanced runoff generation over subsequent events. Preferential flow allowed meltwater to bypass portions of the frozen soil and facilitated the lateral transport of meltwater between high and low topographic positions and groundwater recharge through frozen ground. Insights gained from field studies were used to develop a dual-permeability model of unsaturated flow in frozen soils that assumes two interacting pore domains (macropore and matrix) with distinct water and heat transfer regimes. This dual-permeability formulation was incorporated into the hydrological model HydroGeoSphere to account for liquid-ice phase change in macropores, such that porewater freezing in macropores is governed by macropore-matrix energy transfer. The model was tested against field and laboratory observations and used to examine the effects of preferential flow on snowmelt partitioning between surface and subsurface flow in frozen soils. Simulations were able to reproduce measured profile-scale infiltration and drainage in frozen soil due to macropores, as well as hillslope-scale partitioning of snowmelt input between runoff, infiltration and groundwater recharge. Incorporating macropore flow and freeze-thaw processes was key to simulating the hydrologic functioning of the prairie grassland landscape, and results highlighted that refreezing of infiltrated water governed by macropore-matrix heat transfer is an important subsurface process controlling runoff generation in frozen soils. This study improves our understanding of, and ability to predict, the effects of preferential flow and freeze-thaw on frozen soil infiltrability, and how these processes dictate the partitioning of snowmelt between surface runoff, soil moisture and groundwater recharge in seasonally frozen landscapes.
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    Monitoring fluid injection using seismic time-lapse analysis: a Rainbow Lake case study
    (2005) Ng, Hannah; Krebes, Edward S.; Bentley, Laurence R.
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