Comment on "Horizontal aquifer movement in a theis-theim confined system, by Donald C. Helm

Water Resources Research
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Abstract

In a recent paper, Helm [1994] presents an analysis of horizontal aquifer movement induced by groundwater withdrawal from a confined aquifer in which fluid and grains are incompressible. The analysis considers the aquifer in isolation (ignoring overlying and underlying strata) and assumes that the aquifer deforms purely in the horizontal direction (with no vertical movement). Helm's solution for grain displacement is obtained through introduction of a quantity known as bulk flux, qb, defined as

qb = nvw + (1 - n)vs

where n is porosity, vw is velocity of water, and vs is the velocity of the solid grains. On the basis of the bulk flux concept, Helm develops an explanation for the driving force on the bulk material.

It is our view that Helm's analysis is subject to four limitations. First, Helm's assumption of zero vertical displacement is not supported by field observations and could result in over- estimation of radial displacement. Second, in ignoring the role of overlying and underlying strata, Helm's solution does not yield reliable estimates of aquifer deformation. Third, Helm's solution method works only for problems that involve one spatial coordinate (for example, x or r) but does not generally work for problems involving three-dimensional flow and de- formation. Fourth, Helm's explanation of the driving force on the bulk material is faulty for general three-dimensional problems. The purpose of our comment is to discuss these four issues.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Comment on "Horizontal aquifer movement in a theis-theim confined system, by Donald C. Helm
Series title Water Resources Research
DOI 10.1029/95WR02713
Volume 31
Issue 12
Year Published 1995
Language English
Publisher American Geophysical Union
Contributing office(s) Toxic Substances Hydrology Program
Description 5 p.
First page 3107
Last page 3111