The Experts below are selected from a list of 5961 Experts worldwide ranked by ideXlab platform
Benoît Dewandel - One of the best experts on this subject based on the ideXlab platform.
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A methodology for regionalizing 3-D Effective Porosity at watershed scale in crystalline aquifers
Hydrological Processes, 2017Co-Authors: Benoît Dewandel, Yvan Caballero, Jérôme Perrin, Alexandre Boisson, Fabrice Dazin, Sylvain Ferrant, Subash Chandra, Jean-christophe MaréchalAbstract:13 An innovative approach for regionalizing the 3-D Effective-Porosity field is presented and 14 applied to two large, overexploited and deeply weathered crystalline aquifers located in 15 southern India. The method derives from earlier work on regionalizing a 2-D Effective-16 Porosity field in that part of an aquifer where the water table fluctuates, which is now 17 extended over the entire aquifer using a 3-D approach. A method based on geological and 18 geophysical surveys has also been developed for mapping the weathering profile layers 19 (saprolite and fractured layers). The method for regionalizing 3-D Effective Porosity 20 combines: water-table fluctuation and groundwater budget techniques at various cell sizes 21 with the use of satellite based data (for groundwater abstraction), the structure of the 22 weathering profile and geostatistical techniques. The approach is presented in detail for the 23 Kudaliar watershed (983 km 2), and tested on the 730 km 2 Anantapur watershed. At watershed 24 scale, the Effective Porosity of the aquifer ranges from 0.5% to 2% in Kudaliar and between 25 0.3% and 1% in Anantapur, which agrees with earlier works. Results show that: i) depending 26 on the geology and on the structure of the weathering profile, the vertical distribution of 27 Effective Porosity can be very different, and that the fractured layers in crystalline aquifers are 28 not necessarily characterized by a rapid decrease in Effective Porosity; and ii) that the lateral 29 variations in Effective Porosity can be larger than the vertical ones. These variations suggest 30 that within a same weathering profile the density of open fractures and/or degree of 31 weathering in the fractured zone may significantly varies from a place to another. 32 The proposed method provides information on the spatial distribution of Effective Porosity 33 which is of prime interest in terms of flux and contaminant transport in crystalline aquifers. 34 Implications for mapping groundwater storage and scarcity are also discussed, which should 35 help in improving groundwater resource management strategies. 36 37
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Upscaling and regionalizing hydraulic conductivity and Effective Porosity at watershed scale in deeply weathered crystalline aquifers
Journal of Hydrology, 2012Co-Authors: Benoît Dewandel, Subash Chandra, Jean-christophe Maréchal, O. Bour, B. Ladouche, S. Ahmed, H. PauwelsAbstract:International audienceTwo innovative approaches for upscaling and regionalizing hydraulic conductivity and Effective Porosity at watershed scale are proposed. They are based on the concept that large-scale variations in hydraulic head may characterize large-scale properties and were tested on an unconfined granitic aquifer exposed to deep weathering, located in South India (Maheshwaram watershed, 53 km2). Both methods are based on field data such as water levels, discharge rates of irrigation wells, geological observations and the results of small-scale hydraulic tests. The resulting hydraulic-conductivity map uses the statistical empirical relationship between log-normal distributions of hydraulic conductivity from small-scale tests and linear discharge rates from exploited wells, i.e. the ratio between discharge rate and the saturated aquifer thickness. The empirical relationship agrees with Thiem-Dupuit's assumption for unconfined aquifers. The performance of the method was compared to the values of local hydraulic-conductivity estimates deduced from small-scale tests (not used for drawing the map). About 90% of simulated values varies less than 20% from local measurements (LogK ± 0.4 on average), which is reasonable considering the complexity of the studied fractured aquifer. The regionalization of the Effective Porosity was based on a method that combines both water-table fluctuation and groundwater-budget techniques in the absence of recharge from rainfall. However, the use of these techniques at cell scale requires a good knowledge of groundwater flux to and from the cells, which here is unknown. To avoid this difficulty a coarse-graining method was used, assuming that increasing the cell size for such computations leads to a negligible contribution of these flux compared to net groundwater abstraction from the cell. Our results show that cell sizes over 520*520 m achieve a negligible balance. In addition, Porosity maps provide average values of around 1.5% that are almost identical to the ones previously found at watershed scale. The proposed methods for regionalizing hydraulic conductivity and Porosity fields provide access not only to the average large-scale values, but also to their spatial distribution, which is of prime interest in terms of flux and contaminant transport in a hard-rock environment. The uncertainty introduced by field data, the choice of the computation scale as the impact of cell size on the calculated Effective Porosity value and the possible meaning of their spatial variations are also discussed
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Upscaling and regionalizing hydraulic conductivity and Effective Porosity at watershed scale in deeply weathered crystalline aquifers
Journal of Hydrology, 2011Co-Authors: Benoît Dewandel, Subash Chandra, Jean-christophe Maréchal, O. Bour, B. Ladouche, S. Ahmed, H. PauwelsAbstract:Two innovative approaches for upscaling and regionalizing hydraulic conductivity and Effective Porosity at watershed scale are proposed. They are based on the concept that large-scale variations in hydraulic head may characterize large-scale properties and were tested on an unconfined granitic aquifer exposed to deep weathering, located in South India (Maheshwaram watershed, 53 km2). Both methods are based on field data such as water levels, discharge rates of irrigation wells, geological observations and the results of small-scale hydraulic tests. The resulting hydraulic-conductivity map uses the statistical empirical relationship between log-normal distributions of hydraulic conductivity from small-scale tests and linear discharge rates from exploited wells, i.e. the ratio between discharge rate and the saturated aquifer thickness. The empirical relationship agrees with Thiem-Dupuit's assumption for unconfined aquifers. The performance of the method was compared to the values of local hydraulic-conductivity estimates deduced from small-scale tests (not used for drawing the map). About 90% of simulated values varies less than 20% from local measurements (LogK ± 0.4 on average), which is reasonable considering the complexity of the studied fractured aquifer. The regionalization of the Effective Porosity was based on a method that combines both water-table fluctuation and groundwater-budget techniques in the absence of recharge from rainfall. However, the use of these techniques at cell scale requires a good knowledge of groundwater flux to and from the cells, which here is unknown. To avoid this difficulty a coarse-graining method was used, assuming that increasing the cell size for such computations leads to a negligible contribution of these flux compared to net groundwater abstraction from the cell. Our results show that cell sizes over 520*520 m achieve a negligible balance. In addition, Porosity maps provide average values of around 1.5% that are almost identical to the ones previously found at watershed scale. The proposed methods for regionalizing hydraulic conductivity and Porosity fields provide access not only to the average large-scale values, but also to their spatial distribution, which is of prime interest in terms of flux and contaminant transport in a hard-rock environment. The uncertainty introduced by field data, the choice of the computation scale as the impact of cell size on the calculated Effective Porosity value and the possible meaning of their spatial variations are also discussed.
Jean-christophe Maréchal - One of the best experts on this subject based on the ideXlab platform.
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A methodology for regionalizing 3-D Effective Porosity at watershed scale in crystalline aquifers
Hydrological Processes, 2017Co-Authors: Benoît Dewandel, Yvan Caballero, Jérôme Perrin, Alexandre Boisson, Fabrice Dazin, Sylvain Ferrant, Subash Chandra, Jean-christophe MaréchalAbstract:13 An innovative approach for regionalizing the 3-D Effective-Porosity field is presented and 14 applied to two large, overexploited and deeply weathered crystalline aquifers located in 15 southern India. The method derives from earlier work on regionalizing a 2-D Effective-16 Porosity field in that part of an aquifer where the water table fluctuates, which is now 17 extended over the entire aquifer using a 3-D approach. A method based on geological and 18 geophysical surveys has also been developed for mapping the weathering profile layers 19 (saprolite and fractured layers). The method for regionalizing 3-D Effective Porosity 20 combines: water-table fluctuation and groundwater budget techniques at various cell sizes 21 with the use of satellite based data (for groundwater abstraction), the structure of the 22 weathering profile and geostatistical techniques. The approach is presented in detail for the 23 Kudaliar watershed (983 km 2), and tested on the 730 km 2 Anantapur watershed. At watershed 24 scale, the Effective Porosity of the aquifer ranges from 0.5% to 2% in Kudaliar and between 25 0.3% and 1% in Anantapur, which agrees with earlier works. Results show that: i) depending 26 on the geology and on the structure of the weathering profile, the vertical distribution of 27 Effective Porosity can be very different, and that the fractured layers in crystalline aquifers are 28 not necessarily characterized by a rapid decrease in Effective Porosity; and ii) that the lateral 29 variations in Effective Porosity can be larger than the vertical ones. These variations suggest 30 that within a same weathering profile the density of open fractures and/or degree of 31 weathering in the fractured zone may significantly varies from a place to another. 32 The proposed method provides information on the spatial distribution of Effective Porosity 33 which is of prime interest in terms of flux and contaminant transport in crystalline aquifers. 34 Implications for mapping groundwater storage and scarcity are also discussed, which should 35 help in improving groundwater resource management strategies. 36 37
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Upscaling and regionalizing hydraulic conductivity and Effective Porosity at watershed scale in deeply weathered crystalline aquifers
Journal of Hydrology, 2012Co-Authors: Benoît Dewandel, Subash Chandra, Jean-christophe Maréchal, O. Bour, B. Ladouche, S. Ahmed, H. PauwelsAbstract:International audienceTwo innovative approaches for upscaling and regionalizing hydraulic conductivity and Effective Porosity at watershed scale are proposed. They are based on the concept that large-scale variations in hydraulic head may characterize large-scale properties and were tested on an unconfined granitic aquifer exposed to deep weathering, located in South India (Maheshwaram watershed, 53 km2). Both methods are based on field data such as water levels, discharge rates of irrigation wells, geological observations and the results of small-scale hydraulic tests. The resulting hydraulic-conductivity map uses the statistical empirical relationship between log-normal distributions of hydraulic conductivity from small-scale tests and linear discharge rates from exploited wells, i.e. the ratio between discharge rate and the saturated aquifer thickness. The empirical relationship agrees with Thiem-Dupuit's assumption for unconfined aquifers. The performance of the method was compared to the values of local hydraulic-conductivity estimates deduced from small-scale tests (not used for drawing the map). About 90% of simulated values varies less than 20% from local measurements (LogK ± 0.4 on average), which is reasonable considering the complexity of the studied fractured aquifer. The regionalization of the Effective Porosity was based on a method that combines both water-table fluctuation and groundwater-budget techniques in the absence of recharge from rainfall. However, the use of these techniques at cell scale requires a good knowledge of groundwater flux to and from the cells, which here is unknown. To avoid this difficulty a coarse-graining method was used, assuming that increasing the cell size for such computations leads to a negligible contribution of these flux compared to net groundwater abstraction from the cell. Our results show that cell sizes over 520*520 m achieve a negligible balance. In addition, Porosity maps provide average values of around 1.5% that are almost identical to the ones previously found at watershed scale. The proposed methods for regionalizing hydraulic conductivity and Porosity fields provide access not only to the average large-scale values, but also to their spatial distribution, which is of prime interest in terms of flux and contaminant transport in a hard-rock environment. The uncertainty introduced by field data, the choice of the computation scale as the impact of cell size on the calculated Effective Porosity value and the possible meaning of their spatial variations are also discussed
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Upscaling and regionalizing hydraulic conductivity and Effective Porosity at watershed scale in deeply weathered crystalline aquifers
Journal of Hydrology, 2011Co-Authors: Benoît Dewandel, Subash Chandra, Jean-christophe Maréchal, O. Bour, B. Ladouche, S. Ahmed, H. PauwelsAbstract:Two innovative approaches for upscaling and regionalizing hydraulic conductivity and Effective Porosity at watershed scale are proposed. They are based on the concept that large-scale variations in hydraulic head may characterize large-scale properties and were tested on an unconfined granitic aquifer exposed to deep weathering, located in South India (Maheshwaram watershed, 53 km2). Both methods are based on field data such as water levels, discharge rates of irrigation wells, geological observations and the results of small-scale hydraulic tests. The resulting hydraulic-conductivity map uses the statistical empirical relationship between log-normal distributions of hydraulic conductivity from small-scale tests and linear discharge rates from exploited wells, i.e. the ratio between discharge rate and the saturated aquifer thickness. The empirical relationship agrees with Thiem-Dupuit's assumption for unconfined aquifers. The performance of the method was compared to the values of local hydraulic-conductivity estimates deduced from small-scale tests (not used for drawing the map). About 90% of simulated values varies less than 20% from local measurements (LogK ± 0.4 on average), which is reasonable considering the complexity of the studied fractured aquifer. The regionalization of the Effective Porosity was based on a method that combines both water-table fluctuation and groundwater-budget techniques in the absence of recharge from rainfall. However, the use of these techniques at cell scale requires a good knowledge of groundwater flux to and from the cells, which here is unknown. To avoid this difficulty a coarse-graining method was used, assuming that increasing the cell size for such computations leads to a negligible contribution of these flux compared to net groundwater abstraction from the cell. Our results show that cell sizes over 520*520 m achieve a negligible balance. In addition, Porosity maps provide average values of around 1.5% that are almost identical to the ones previously found at watershed scale. The proposed methods for regionalizing hydraulic conductivity and Porosity fields provide access not only to the average large-scale values, but also to their spatial distribution, which is of prime interest in terms of flux and contaminant transport in a hard-rock environment. The uncertainty introduced by field data, the choice of the computation scale as the impact of cell size on the calculated Effective Porosity value and the possible meaning of their spatial variations are also discussed.
H. Pauwels - One of the best experts on this subject based on the ideXlab platform.
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Upscaling and regionalizing hydraulic conductivity and Effective Porosity at watershed scale in deeply weathered crystalline aquifers
Journal of Hydrology, 2012Co-Authors: Benoît Dewandel, Subash Chandra, Jean-christophe Maréchal, O. Bour, B. Ladouche, S. Ahmed, H. PauwelsAbstract:International audienceTwo innovative approaches for upscaling and regionalizing hydraulic conductivity and Effective Porosity at watershed scale are proposed. They are based on the concept that large-scale variations in hydraulic head may characterize large-scale properties and were tested on an unconfined granitic aquifer exposed to deep weathering, located in South India (Maheshwaram watershed, 53 km2). Both methods are based on field data such as water levels, discharge rates of irrigation wells, geological observations and the results of small-scale hydraulic tests. The resulting hydraulic-conductivity map uses the statistical empirical relationship between log-normal distributions of hydraulic conductivity from small-scale tests and linear discharge rates from exploited wells, i.e. the ratio between discharge rate and the saturated aquifer thickness. The empirical relationship agrees with Thiem-Dupuit's assumption for unconfined aquifers. The performance of the method was compared to the values of local hydraulic-conductivity estimates deduced from small-scale tests (not used for drawing the map). About 90% of simulated values varies less than 20% from local measurements (LogK ± 0.4 on average), which is reasonable considering the complexity of the studied fractured aquifer. The regionalization of the Effective Porosity was based on a method that combines both water-table fluctuation and groundwater-budget techniques in the absence of recharge from rainfall. However, the use of these techniques at cell scale requires a good knowledge of groundwater flux to and from the cells, which here is unknown. To avoid this difficulty a coarse-graining method was used, assuming that increasing the cell size for such computations leads to a negligible contribution of these flux compared to net groundwater abstraction from the cell. Our results show that cell sizes over 520*520 m achieve a negligible balance. In addition, Porosity maps provide average values of around 1.5% that are almost identical to the ones previously found at watershed scale. The proposed methods for regionalizing hydraulic conductivity and Porosity fields provide access not only to the average large-scale values, but also to their spatial distribution, which is of prime interest in terms of flux and contaminant transport in a hard-rock environment. The uncertainty introduced by field data, the choice of the computation scale as the impact of cell size on the calculated Effective Porosity value and the possible meaning of their spatial variations are also discussed
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Upscaling and regionalizing hydraulic conductivity and Effective Porosity at watershed scale in deeply weathered crystalline aquifers
Journal of Hydrology, 2011Co-Authors: Benoît Dewandel, Subash Chandra, Jean-christophe Maréchal, O. Bour, B. Ladouche, S. Ahmed, H. PauwelsAbstract:Two innovative approaches for upscaling and regionalizing hydraulic conductivity and Effective Porosity at watershed scale are proposed. They are based on the concept that large-scale variations in hydraulic head may characterize large-scale properties and were tested on an unconfined granitic aquifer exposed to deep weathering, located in South India (Maheshwaram watershed, 53 km2). Both methods are based on field data such as water levels, discharge rates of irrigation wells, geological observations and the results of small-scale hydraulic tests. The resulting hydraulic-conductivity map uses the statistical empirical relationship between log-normal distributions of hydraulic conductivity from small-scale tests and linear discharge rates from exploited wells, i.e. the ratio between discharge rate and the saturated aquifer thickness. The empirical relationship agrees with Thiem-Dupuit's assumption for unconfined aquifers. The performance of the method was compared to the values of local hydraulic-conductivity estimates deduced from small-scale tests (not used for drawing the map). About 90% of simulated values varies less than 20% from local measurements (LogK ± 0.4 on average), which is reasonable considering the complexity of the studied fractured aquifer. The regionalization of the Effective Porosity was based on a method that combines both water-table fluctuation and groundwater-budget techniques in the absence of recharge from rainfall. However, the use of these techniques at cell scale requires a good knowledge of groundwater flux to and from the cells, which here is unknown. To avoid this difficulty a coarse-graining method was used, assuming that increasing the cell size for such computations leads to a negligible contribution of these flux compared to net groundwater abstraction from the cell. Our results show that cell sizes over 520*520 m achieve a negligible balance. In addition, Porosity maps provide average values of around 1.5% that are almost identical to the ones previously found at watershed scale. The proposed methods for regionalizing hydraulic conductivity and Porosity fields provide access not only to the average large-scale values, but also to their spatial distribution, which is of prime interest in terms of flux and contaminant transport in a hard-rock environment. The uncertainty introduced by field data, the choice of the computation scale as the impact of cell size on the calculated Effective Porosity value and the possible meaning of their spatial variations are also discussed.
Subash Chandra - One of the best experts on this subject based on the ideXlab platform.
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A methodology for regionalizing 3-D Effective Porosity at watershed scale in crystalline aquifers
Hydrological Processes, 2017Co-Authors: Benoît Dewandel, Yvan Caballero, Jérôme Perrin, Alexandre Boisson, Fabrice Dazin, Sylvain Ferrant, Subash Chandra, Jean-christophe MaréchalAbstract:13 An innovative approach for regionalizing the 3-D Effective-Porosity field is presented and 14 applied to two large, overexploited and deeply weathered crystalline aquifers located in 15 southern India. The method derives from earlier work on regionalizing a 2-D Effective-16 Porosity field in that part of an aquifer where the water table fluctuates, which is now 17 extended over the entire aquifer using a 3-D approach. A method based on geological and 18 geophysical surveys has also been developed for mapping the weathering profile layers 19 (saprolite and fractured layers). The method for regionalizing 3-D Effective Porosity 20 combines: water-table fluctuation and groundwater budget techniques at various cell sizes 21 with the use of satellite based data (for groundwater abstraction), the structure of the 22 weathering profile and geostatistical techniques. The approach is presented in detail for the 23 Kudaliar watershed (983 km 2), and tested on the 730 km 2 Anantapur watershed. At watershed 24 scale, the Effective Porosity of the aquifer ranges from 0.5% to 2% in Kudaliar and between 25 0.3% and 1% in Anantapur, which agrees with earlier works. Results show that: i) depending 26 on the geology and on the structure of the weathering profile, the vertical distribution of 27 Effective Porosity can be very different, and that the fractured layers in crystalline aquifers are 28 not necessarily characterized by a rapid decrease in Effective Porosity; and ii) that the lateral 29 variations in Effective Porosity can be larger than the vertical ones. These variations suggest 30 that within a same weathering profile the density of open fractures and/or degree of 31 weathering in the fractured zone may significantly varies from a place to another. 32 The proposed method provides information on the spatial distribution of Effective Porosity 33 which is of prime interest in terms of flux and contaminant transport in crystalline aquifers. 34 Implications for mapping groundwater storage and scarcity are also discussed, which should 35 help in improving groundwater resource management strategies. 36 37
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Upscaling and regionalizing hydraulic conductivity and Effective Porosity at watershed scale in deeply weathered crystalline aquifers
Journal of Hydrology, 2012Co-Authors: Benoît Dewandel, Subash Chandra, Jean-christophe Maréchal, O. Bour, B. Ladouche, S. Ahmed, H. PauwelsAbstract:International audienceTwo innovative approaches for upscaling and regionalizing hydraulic conductivity and Effective Porosity at watershed scale are proposed. They are based on the concept that large-scale variations in hydraulic head may characterize large-scale properties and were tested on an unconfined granitic aquifer exposed to deep weathering, located in South India (Maheshwaram watershed, 53 km2). Both methods are based on field data such as water levels, discharge rates of irrigation wells, geological observations and the results of small-scale hydraulic tests. The resulting hydraulic-conductivity map uses the statistical empirical relationship between log-normal distributions of hydraulic conductivity from small-scale tests and linear discharge rates from exploited wells, i.e. the ratio between discharge rate and the saturated aquifer thickness. The empirical relationship agrees with Thiem-Dupuit's assumption for unconfined aquifers. The performance of the method was compared to the values of local hydraulic-conductivity estimates deduced from small-scale tests (not used for drawing the map). About 90% of simulated values varies less than 20% from local measurements (LogK ± 0.4 on average), which is reasonable considering the complexity of the studied fractured aquifer. The regionalization of the Effective Porosity was based on a method that combines both water-table fluctuation and groundwater-budget techniques in the absence of recharge from rainfall. However, the use of these techniques at cell scale requires a good knowledge of groundwater flux to and from the cells, which here is unknown. To avoid this difficulty a coarse-graining method was used, assuming that increasing the cell size for such computations leads to a negligible contribution of these flux compared to net groundwater abstraction from the cell. Our results show that cell sizes over 520*520 m achieve a negligible balance. In addition, Porosity maps provide average values of around 1.5% that are almost identical to the ones previously found at watershed scale. The proposed methods for regionalizing hydraulic conductivity and Porosity fields provide access not only to the average large-scale values, but also to their spatial distribution, which is of prime interest in terms of flux and contaminant transport in a hard-rock environment. The uncertainty introduced by field data, the choice of the computation scale as the impact of cell size on the calculated Effective Porosity value and the possible meaning of their spatial variations are also discussed
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Upscaling and regionalizing hydraulic conductivity and Effective Porosity at watershed scale in deeply weathered crystalline aquifers
Journal of Hydrology, 2011Co-Authors: Benoît Dewandel, Subash Chandra, Jean-christophe Maréchal, O. Bour, B. Ladouche, S. Ahmed, H. PauwelsAbstract:Two innovative approaches for upscaling and regionalizing hydraulic conductivity and Effective Porosity at watershed scale are proposed. They are based on the concept that large-scale variations in hydraulic head may characterize large-scale properties and were tested on an unconfined granitic aquifer exposed to deep weathering, located in South India (Maheshwaram watershed, 53 km2). Both methods are based on field data such as water levels, discharge rates of irrigation wells, geological observations and the results of small-scale hydraulic tests. The resulting hydraulic-conductivity map uses the statistical empirical relationship between log-normal distributions of hydraulic conductivity from small-scale tests and linear discharge rates from exploited wells, i.e. the ratio between discharge rate and the saturated aquifer thickness. The empirical relationship agrees with Thiem-Dupuit's assumption for unconfined aquifers. The performance of the method was compared to the values of local hydraulic-conductivity estimates deduced from small-scale tests (not used for drawing the map). About 90% of simulated values varies less than 20% from local measurements (LogK ± 0.4 on average), which is reasonable considering the complexity of the studied fractured aquifer. The regionalization of the Effective Porosity was based on a method that combines both water-table fluctuation and groundwater-budget techniques in the absence of recharge from rainfall. However, the use of these techniques at cell scale requires a good knowledge of groundwater flux to and from the cells, which here is unknown. To avoid this difficulty a coarse-graining method was used, assuming that increasing the cell size for such computations leads to a negligible contribution of these flux compared to net groundwater abstraction from the cell. Our results show that cell sizes over 520*520 m achieve a negligible balance. In addition, Porosity maps provide average values of around 1.5% that are almost identical to the ones previously found at watershed scale. The proposed methods for regionalizing hydraulic conductivity and Porosity fields provide access not only to the average large-scale values, but also to their spatial distribution, which is of prime interest in terms of flux and contaminant transport in a hard-rock environment. The uncertainty introduced by field data, the choice of the computation scale as the impact of cell size on the calculated Effective Porosity value and the possible meaning of their spatial variations are also discussed.
Terry C. Hazen - One of the best experts on this subject based on the ideXlab platform.
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Push-pull tests for estimating Effective Porosity: expanded analytical solution and in situ application
Hydrogeology Journal, 2018Co-Authors: Charles J. Paradis, Larry D. Mckay, Edmund Perfect, Jonathan D. Istok, Terry C. HazenAbstract:The analytical solution describing the one-dimensional displacement of the center of mass of a tracer during an injection, drift, and extraction test (push-pull test) was expanded to account for displacement during the injection phase. The solution was expanded to improve the in situ estimation of Effective Porosity. The truncated equation assumed displacement during the injection phase was negligible, which may theoretically lead to an underestimation of the true value of Effective Porosity. To experimentally compare the expanded and truncated equations, single-well push-pull tests were conducted across six test wells located in a shallow, unconfined aquifer comprised of unconsolidated and heterogeneous silty and clayey fill materials. The push-pull tests were conducted by injection of bromide tracer, followed by a non-pumping period, and subsequent extraction of groundwater. The values of Effective Porosity from the expanded equation (0.6–5.0%) were substantially greater than from the truncated equation (0.1–1.3%). The expanded and truncated equations were compared to data from previous push-pull studies in the literature and demonstrated that displacement during the injection phase may or may not be negligible, depending on the aquifer properties and the push-pull test parameters. The results presented here also demonstrated the spatial variability of Effective Porosity within a relatively small study site can be substantial, and the error-propagated uncertainty of Effective Porosity can be mitigated to a reasonable level (
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push pull tests for estimating Effective Porosity expanded analytical solution and in situ application
Hydrogeology Journal, 2018Co-Authors: Charles J. Paradis, Larry D. Mckay, Edmund Perfect, Jonathan D. Istok, Terry C. HazenAbstract:Author(s): Paradis, CJ; McKay, LD; Perfect, E; Istok, JD; Hazen, TC | Abstract: © 2017, The Author(s). The analytical solution describing the one-dimensional displacement of the center of mass of a tracer during an injection, drift, and extraction test (push-pull test) was expanded to account for displacement during the injection phase. The solution was expanded to improve the in situ estimation of Effective Porosity. The truncated equation assumed displacement during the injection phase was negligible, which may theoretically lead to an underestimation of the true value of Effective Porosity. To experimentally compare the expanded and truncated equations, single-well push-pull tests were conducted across six test wells located in a shallow, unconfined aquifer comprised of unconsolidated and heterogeneous silty and clayey fill materials. The push-pull tests were conducted by injection of bromide tracer, followed by a non-pumping period, and subsequent extraction of groundwater. The values of Effective Porosity from the expanded equation (0.6–5.0%) were substantially greater than from the truncated equation (0.1–1.3%). The expanded and truncated equations were compared to data from previous push-pull studies in the literature and demonstrated that displacement during the injection phase may or may not be negligible, depending on the aquifer properties and the push-pull test parameters. The results presented here also demonstrated the spatial variability of Effective Porosity within a relatively small study site can be substantial, and the error-propagated uncertainty of Effective Porosity can be mitigated to a reasonable level (l ± 0.5%). The tests presented here are also the first that the authors are aware of that estimate, in situ, the Effective Porosity of fine-grained fill material.
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Push-pull tests for estimating Effective Porosity: expanded analytical solution and in situ application
Hydrogeology Journal, 2017Co-Authors: Charles J. Paradis, Larry D. Mckay, Edmund Perfect, Jonathan D. Istok, Terry C. HazenAbstract:Abstract The analytical solution describing the one-dimensional displacement of the center of mass of a tracer during an injection, drift, and extraction test (push-pull test) was expanded to account for displacement during the injection phase. The solution was expanded to improve the in situ estimation of Effective Porosity. The truncated equation assumed displacement during the injection phase was negligible, which may theoretically lead to an underestimation of the true value of Effective Porosity. To experimentally compare the expanded and truncated equations, single-well push-pull tests were conducted across six test wells located in a shallow, unconfined aquifer comprised of unconsolidated and heterogeneous silty and clayey fill materials. The push-pull tests were conducted by injection of bromide tracer, followed by a non-pumping period, and subsequent extraction of groundwater. The values of Effective Porosity from the expanded equation (0.6–5.0%) were substantially greater than from the truncated equation (0.1–1.3%). The expanded and truncated equations were compared to data from previous push-pull studies in the literature and demonstrated that displacement during the injection phase may or may not be negligible, depending on the aquifer properties and the push-pull test parameters. The results presented here also demonstrated the spatial variability of Effective Porosity within a relatively small study site can be substantial, and the error-propagated uncertainty of Effective Porosity can be mitigated to a reasonable level (< ± 0.5%). The tests presented here are also the first that the authors are aware of that estimate, in situ, the Effective Porosity of fine-grained fill material.
