Tracing and dating young ground water

Plummer, L. Niel; Friedman, Linda C.

doi:10.3133/fs13499

Cited by 28 publications

(17 citation statements)

References 6 publications

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“…Researchers have attempted to surmount these limitations by using preexisting environmental tracers, including chemical isotopes, that can estimate subsurface residence time by means of time‐varying input, radioactive decay, or other mechanisms. For short‐time or near‐surface problems, these may include anthropogenic species such as chlorofluorocarbons (CFCs) or tritium [e.g., Plummer and Friedman , 1999; Shapiro et al , 1999]. Studies involving longer traveltimes tend to exploit natural chemical constituents of groundwater that enter the subsurface during precipitation or through surface water bodies.…”

Section: Introductionmentioning

confidence: 99%

Potential effects of regional pumpage on groundwater age distribution

Zinn

Konikow

2007

Water Resources Research

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[1] Groundwater ages estimated from environmental tracers can help calibrate groundwater flow models. Groundwater age represents a mixture of traveltimes, with the distribution of ages determined by the detailed structure of the flow field, which can be prone to significant transient variability. Effects of pumping on age distribution were assessed using direct age simulation in a hypothetical layered aquifer system. A steady state predevelopment age distribution was computed first. A well field was then introduced, and pumpage caused leakage into the confined aquifer of older water from an overlying confining unit. Large changes in simulated groundwater ages occurred in both the aquifer and the confining unit at high pumping rates, and the effects propagated a substantial distance downgradient from the wells. The range and variance of ages contributing to the well increased substantially during pumping. The results suggest that the groundwater age distribution in developed aquifers may be affected by transient leakage from low-permeability material, such as confining units, under certain hydrogeologic conditions.

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Section: Introductionmentioning

confidence: 99%

Potential effects of regional pumpage on groundwater age distribution

Zinn

Konikow

2007

Water Resources Research

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“…Depending on the tracer used, age dating techniques can be used to date relatively young groundwater (e.g., Busenberg and Plummer 1992;Plummer and Friedman 1999;Shapiro et al 1999) or can target longer, basin-scale transport times (Castro et al 1998;Sanford et al 2004).…”

Section: Introductionmentioning

confidence: 99%

Effects of intraborehole flow on groundwater age distribution

Zinn

Konikow

2007

Hydrogeol J

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Environmental tracers are used to estimate groundwater ages and travel times, but the strongly heterogeneous nature of many subsurface environments can cause mixing between waters of highly disparate ages, adding additional complexity to the age-estimation process. Mixing may be exacerbated by the presence of wells because long open intervals or long screens with openings at multiple depths can transport water and solutes rapidly over a large vertical distance. The effect of intraborehole flow on groundwater age was examined numerically using direct age transport simulation coupled with the MultiNode Well Package of MODFLOW. Ages in a homogeneous, anisotropic aquifer reached a predevelopment steady state possessing strong depth dependence. A nonpumping multi-node well was then introduced in one of three locations within the system. In all three cases, vertical transport along the well resulted in substantial changes in age distributions within the system. After a pumping well was added near the nonpumping multi-node well, ages were further perturbed by a flow reversal in the nonpumping multi-node well. Results indicated that intraborehole flow can substantially alter groundwater ages, but the effects are highly dependent on local or regional flow conditions and may change with time.Résumé Les traceurs environnementaux sont habituellement utilisés pour estimer les âges des eaux souterraines et les temps de résidence. Cependant, la nature hautement hétérogène de nombreux environnements souterrains peut engendrer des mélanges entre des eaux d'âges très disparates, complexifiant par-là même le processus d'estimation des âges. La présence de puits peut exacerber le phénomène de mélange : de longues sections en trou nu ou crépinées exploitant plusieurs niveaux productifs distincts peuvent transporter rapidement l'eau et les solutés sur une grande distance verticale. Les conséquences de flux intraforages sur les ages des eaux souterraines ont été étudiées numériquement en couplant les simulations directes de temps de résidence avec le "Multi-Node Well Package" de MODFLOW. Dans un aquifère homogène et anisotrope, les âges ont atteint un régime permanent étroitement dépendant de la profondeur. Un puits multinoeud au repos a ensuite été inséré dans l'une des trois zones du système. Dans les trois cas, les transports verticaux par le puits ont entraîné des modifications substantielles des distributions des âges dans le système. Enfin, après ajout d'un puits en pompage à proximité du puits au repos, les âges ont été perturbé davantage, par une inversion du flux dans le puits au repos. Les résultats ont montré que les flux intraforages peuvent modifier substantiellement les âges des eaux souterraines, mais leurs effets sont hautement dépendants des conditions locales ou régionales d'écoule-ment, et peuvent de surcroît changer dans le temps.Resumen Los trazadores ambientales pueden usarse para estimar el tiempo de viaje y las edades del agua subterránea pero la naturaleza fuertemente heterogénea de muchos ambientes s...

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“…In the till, recharge dates were estimated using tritium‐dating methods (Thatcher et al. , 1977), whereas in the sand, recharge dates were estimated using chlorofluorocarbon (CFC)‐dating methods (Plummer and Busenberg, 1999; Plummer and Friedman, 1999). The tritium‐dating method is less precise than the CFC‐dating method, but was used because of anticipated low dissolved oxygen concentrations, and availability and cost of equipment.…”

Section: Methodsmentioning

confidence: 99%

Pesticide and Transformation Product Detections and Age‐Dating Relations from Till and Sand Deposits¹

Warner¹,

Morrow²

2007

J American Water Resour Assoc

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Pesticide and transformation product concentrations and frequencies in ground water from areas of similar crop and pesticide applications may vary substantially with differing lithologies. Pesticide analysis data for atrazine, metolachlor, alachlor, acetochlor, and cyanazine and their pesticide transformation products were collected at 69 monitoring wells in Illinois and northern Indiana to document occurrence of pesticides and their transformation products in two agricultural areas of differing lithologies, till, and sand. The till is primarily tile drained and has preferential fractured flow, whereas the sand primarily has surface water drainage and primary porosity flow. Transformation products represent most of the agricultural pesticides in ground water regardless of aquifer material – till or sand. Transformation products were detected more frequently than parent pesticides in both the till and sand, with metolachlor ethane sulfonic acid being most frequently detected. Estimated ground‐water recharge dates for the sand were based on chlorofluorocarbon analyses. These age‐dating data indicate that ground water recharged prior to 1990 is more likely to have a detection of a pesticide or pesticide transformation product. Detections were twice as frequent in ground water recharged prior to 1990 (82%) than in ground water recharged on or after 1990 (33%). The highest concentrations of atrazine, alachlor, metolachlor, and their transformation products, also were detected in samples from ground water recharged prior to 1990. These age/pesticide detection relations are opposite of what would normally be expected, and may be the result of preferential flow and/or ground‐water mixing between aquifers and aquitards as evident by the detection of acetochlor transformation products in samples with estimated ground‐water ages predating initial pesticide application.

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Tracing and dating young ground water

Cited by 28 publications

References 6 publications

Potential effects of regional pumpage on groundwater age distribution

Potential effects of regional pumpage on groundwater age distribution

Effects of intraborehole flow on groundwater age distribution

Pesticide and Transformation Product Detections and Age‐Dating Relations from Till and Sand Deposits¹

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Tracing and dating young ground water

Cited by 28 publications

References 6 publications

Potential effects of regional pumpage on groundwater age distribution

Potential effects of regional pumpage on groundwater age distribution

Effects of intraborehole flow on groundwater age distribution

Pesticide and Transformation Product Detections and Age‐Dating Relations from Till and Sand Deposits1

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Pesticide and Transformation Product Detections and Age‐Dating Relations from Till and Sand Deposits¹