Estimating Flow Using Tracers and Hydraulics in Synthetic Heterogeneous Aquifers

Larocque, Marie; Cook, Peter G.; Haaken, Klaus et Simmons, Craig T. (2009). « Estimating Flow Using Tracers and Hydraulics in Synthetic Heterogeneous Aquifers ». Ground Water, 47(6), pp. 786-796.

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Résumé

Regional ground water flow is most usually estimated using Darcy’s law, with hydraulic conductivities estimated from pumping tests, but can also be estimated using ground water residence times derived from radioactive tracers. The two methods agree reasonably well in relatively homogeneous aquifers but it is not clear which is likely to produce more reliable estimates of ground water flow rates in heterogeneous systems. The aim of this paper is to compare bias and uncertainty of tracer and hydraulic approaches to assess ground water flow in heterogeneous aquifers. Synthetic two-dimensional aquifers with different levels of heterogeneity (correlation lengths, variances) are used to simulate ground water flow, pumping tests, and transport of radioactive tracers. Results show that bias and uncertainty of flow rates increase with the variance of the hydraulic conductivity for both methods. The bias resulting from the nonlinearity of the concentration–time relationship can be reduced by choosing a tracer with a decay rate similar to the mean ground water residence time. The bias on flow rates estimated from pumping tests is reduced when performing long duration tests. The uncertainty on ground water flow is minimized when the sampling volume is large compared to the correlation length. For tracers, the uncertainty is related to the ratio of correlation length to the distance between sampling wells. For pumping tests, it is related to the ratio of correlation length to the pumping test’s radius of influence. In regional systems, it may be easier to minimize this ratio for tracers than for pumping tests.

Type:	Article de revue scientifique
Informations complémentaires:	Copyright © 2009 The Author(s).
Mots-clés ou Sujets:	Concentration-time, Correlation lengths, Darcy's law, Decay rate, Heterogeneous aquifers, Heterogeneous systems, Long duration, Non-Linearity, On flow, Pumping tests, Radius of influences, Reliable estimates, Residence time, Sampling volume
Unité d'appartenance:	Centres institutionnels > Centre pour l'étude et la simulation du climat à l'échelle régionale (ESCER) Faculté des sciences > Département des sciences de la Terre et de l'atmosphère
Déposé par:	Marie Larocque
Date de dépôt:	23 mars 2016 13:17
Dernière modification:	25 avr. 2016 15:39
Adresse URL :	http://archipel.uqam.ca/id/eprint/8011

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