Application of Environmental Tracers in the Memphis Aquifer and Implication for Sustainability of Groundwater Resources in the Memphis Metropolitan Area, Tennessee

Larsen, Daniel; Waldron, Brian; Schoefernacker, Scott; Gallo, Haley Grace; Koban, John; Bradshaw, Elizabeth Ann

doi:10.1111/j.1936-704x.2016.03231.x

Cited by 13 publications

(56 citation statements)

References 32 publications

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“…Traditionally, the public water supply authority in the Memphis area assumed that the UCCU could fully protect the water in the Memphis aquifer from downward leakage of the contaminated or poor-quality groundwater from the overlying Shallow aquifer. However, recent studies show that at some locations, the UCCU is thin or absent, which leads to the contribution of water from the Shallow aquifer to the Memphis aquifer [9][10][11]14]. Hence, sustainable water management in the Memphis area requires the locations of breaches in the UCCU to ensure the protection of water pumped from the production wells.…”

Section: Discussionmentioning

confidence: 99%

“…So far, two different approaches have been employed to answer this question. The first approach is the "geochemical investigation" [7][8][9][10][11][12][13] where groundwater samples are analyzed to identify geochemical signatures that are attributed to surface water within the groundwater. Within the Memphis area, age-dating of groundwater by using tritium-helium-3 and sulfur hexafluoride support geochemical data, and reflects the influence of modern water (<50 years) in the Memphis aquifer.…”

Section: Introductionmentioning

confidence: 99%

“…Within the Memphis area, age-dating of groundwater by using tritium-helium-3 and sulfur hexafluoride support geochemical data, and reflects the influence of modern water (<50 years) in the Memphis aquifer. Subsequent studies have shown that modern water contributes up to 40% of groundwater withdrawn from production wells-in one case, production water contains as much as 75% modern water [9][10][11]. The second approach is the "geological investigation", in which techniques, such as surveying stratigraphic thickness and water table elevation, electrical resistivity surveys, shear-wave seismic reflection, and other geophysical analyses are used to identify gaps in impermeable layers [5,[14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

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Application of Numerical Tools to Investigate a Leaky Aquitard beneath Urban Well Fields

Jazaei

Waldron

Schoefernacker

et al. 2018

Water

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Memphis aquifer is the primary drinking water source in Shelby County (Tennessee, USA), and it supplies industrial, commercial, and residential water. Memphis aquifer is separated from the Shallow aquifer by a clayey layer known as the Upper Claiborne confining unit (UCCU). All of the production wells in the Memphis area are screened in the Memphis aquifer, or even deeper in the Fort Pillow aquifer. Traditionally, it was assumed that the UCCU could fully protect the Memphis aquifer from the contaminated Shallow aquifer groundwater. However, recent studies show that at some locations, the UCCU is thin or absent, which possibly leads to the contribution of Shallow aquifer to the Memphis aquifer. Accurately locating the breaches demands expensive and difficult geological or geochemical investigations, especially within an urban area. Hence, a pre-field investigation to identify the locations where the presence of breaches is likely can significantly reduce the cost of field investigations and improve their results. In this study, to identify the locations where the presence of breaches in the UCCU is likely, we develop a reliable MODFLOW-based numerical model, and use three different analyses: (1) pilot-point calibration (PPC), (2) velocity and flow budget (VFB), and (3) particle tracking (PT), to post-process the developed groundwater model results. These pre-field numerical investigations provide relevant and defensible explanations for groundwater flow anomalies in an aquifer system for informed decision-making and future field investigations. In this study, we identify five specific zones within the broad study area which are reasonable candidates for the future field investigations. Finally, we test the results of each analysis against other evidence for breaches, to demonstrate that the results of the numerical analyses are reliable and supported by previous studies.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Application of Numerical Tools to Investigate a Leaky Aquitard beneath Urban Well Fields

Jazaei

Waldron

Schoefernacker

et al. 2018

Water

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“…So far, two different approaches are employed to answer this question. The first approach is the "geochemical investigation" (Neretnieks, 1981;Busenberg et al, 1993;Larsen et al, 2003Larsen et al, , 2013Larsen et al, , 2016Ivey et al, 2008;Majidzadeh et al, 2017) where groundwater samples are analyzed to identify geochemical signatures attributed to surface water within the Memphis aquifer water. Within the Memphis area, age-dating of groundwater using tritium-helium-3 and sulfur hexafluoride support 6 geochemical data and reflects the influence of modern water (< 50 years) in the Memphis aquifer.…”

Section: Introductionmentioning

confidence: 99%

“…Subsequent studies have shown that modern water contributes up to 40% of groundwater withdrawn from production wells -in one case production water contains as much as 75% modern water (Larsen et al, 2003(Larsen et al, , 2013(Larsen et al, , 2016. The second approach is the "geological investigation" in which techniques such as surveying stratigraphic thickness and water table elevation, electrical resistivity surveys, shear-wave seismic reflection, and other geophysical analyses are used to identify gaps in impermeable layers (Parks, 1990;Sutinen, 1992;Besson et al, 2004;Waldron et al, 2009;Schoefernacker, 2018).…”

Section: Introductionmentioning

confidence: 99%

Application of Numerical Tools to Investigate a Leaky Aquitard beneath Urban Well Fields

Jazaei¹,

Waldron²,

Schoefernacker³

et al. 2018

Preprint

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Memphis aquifer is the primary drinking water source in Shelby County (Tennessee, USA) and supplies industrial, commercial, and residential water. Memphis aquifer is separated from the Shallow aquifer by a clayey layer known as Upper Claiborne Confining Unit (UCCU). All of the production wells in the Memphis area are screened in the Memphis aquifer or even deeper in the Fort Pillow aquifer. Traditionally, it was assumed that the UCCU could fully protect the Memphis aquifer from the contaminated Shallow aquifer groundwater. However, recent studies show that at some locations the UCCU is thin or absent which possibly leads to the contribution of Shallow aquifer to the Memphis aquifer. Accurately locating the breaches demands expensive and difficult geological or geochemical investigations, especially within an urban area. Hence, a pre-field investigation to identify the locations where the presence of breaches is likely can significantly reduce the cost of field investigations and improve the their results. In this study, to identify the locations where the presence of breaches in the UCCU is likely we use three different analyses: (1) pilot point calibration (PPC), (2) velocity and flow budget (VFB), and (3) particle tracking (PT) to post-process the developed groundwater results. These pre-field numerical investigations provide relevant and defensible explanations for groundwater flow anomalies in an aquifer system for informed decision-making and future field investigations. In this study, we identify five specific zones within the broad study area which are reasonable candidates for the future field investigations. Finally, we test the results of each analysis against other evidence for breaches to demonstrate that the results of the numerical analyses are reliable and supported by previous studies.

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Stories of a water-table: anomalous depressions, aquitard breaches and seasonal implications, Shelby County, Tennessee, USA

Lozano-Medina

Waldron

Schoefernacker

et al. 2023

Environ Monit Assess

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An extensive water level survey of the water-table aquifer (i.e., shallow aquifer) within Shelby County, Tennessee, was conducted in the dry (fall 2020) and wet (spring 2021) seasons. Water-table surfaces were generated using cokriging to observe seasonal differences to identify anomalous water-table depressions, indicative of an underlying aquitard breach. Seasonal differences were attributed to non-coincident control and timing between the surveys and when optimum dry (fall) and wet (spring) conditions existed, as observed through comparisons with continuous historical water levels from 12 shallow monitoring wells. Additionally, data from fall 2020 were compared to previous studies in 2005 and 2015 to determine decadal changes in levels and shape of the water-table surface which were mostly attributed to changes in data control and potential climate variations. A prediction error map was generated from the 2020 dataset to identify areas of the county with high-prediction error (>7.0 m) to offer guidance on where future well control would be optimal.

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Application of Environmental Tracers in the Memphis Aquifer and Implication for Sustainability of Groundwater Resources in the Memphis Metropolitan Area, Tennessee

Cited by 13 publications

References 32 publications

Application of Numerical Tools to Investigate a Leaky Aquitard beneath Urban Well Fields

Application of Numerical Tools to Investigate a Leaky Aquitard beneath Urban Well Fields

Application of Numerical Tools to Investigate a Leaky Aquitard beneath Urban Well Fields

Stories of a water-table: anomalous depressions, aquitard breaches and seasonal implications, Shelby County, Tennessee, USA

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