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The AAPG/Datapages Combined Publications Database

Environmental Geosciences (DEG)

Abstract

 

Can Storage Coefficient Be Neglected in the Estimation of Unconfined Aquifer Parameters?

Xunhong Chen1

1 Conservation and Survey Division, University of Nebraska–Lincoln, Lincoln, NE 68588

Xunhong Chen is an associate professor and research hydrogeologist with the Conservation and Survey Division at the University of Nebraska–Lincoln. He received his Ph.D. from the University of Wyoming. His current research includes groundwater modeling, aquifer tests, and stream–aquifer interactions.

Abstract

Unlike the Neuman Previous HitsolutionNext Hit (1974), the Dagan Previous HitsolutionNext Hit (1967) neglects elastic storage of unconfined aquifers. Whereas theformer has been commonly used in the analysis of aquifer pumpingtests, application of the latter to determination of aquiferparameters are rare. This article evaluates the reliabilityof the Dagan Previous HitsolutionNext Hit (1967) for the determination of the horizontaland Previous HitverticalNext Hit hydraulic conductivity Kr and Kz and specific yieldSy by neglecting the role of aquifer storage coefficient S.To be consistent in the analysis of aquifer test data, the Dagansolution was combined with an inverse computational procedureso that Kr, Kz, and Sy can be automatically calculated. Computationsconverge relatively fast because evaluation of the Dagan solutionis mathematically simpler than is the Neuman Previous HitsolutionNext Hit. Datafrom three pumping tests conducted in alluvial aquifers in thePlatte and Republican River valleys, Nebraska, were analyzed.Earlytime drawdown data from the site in the Platte River valleyare scarce, but plenty of early-time drawdowns were collectedfrom the two sites in the Republican River valley. Comparisonof the results from the Dagan and the Neuman Previous HitsolutionNext Hit indicatesthat the Dagan Previous HitsolutionNext Hit provides aquifer parameter values veryclose to those of the Neuman Previous HitsolutionNext Hit in most situations. Formost practical purposes, the Dagan Previous HitsolutionNext Hit is as good as theNeuman Previous HitsolutionTop for aquifer test analysis.

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