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Response of the water level in a well to Earth tides and atmospheric loading under unconfined conditions

Water Resources Research

By:
and
https://doi.org/10.1029/WR026i008p01803

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Abstract

The response of the water level in a well to Earth tides and atmospheric loading under unconfined conditions can be explained if the water level is controlled by the aquifer response averaged over the saturated depth of the well. Because vertical averaging tends to diminish the influence of the water table, the response is qualitatively similar to the response of a well under partially confined conditions. When the influence of well bore storage can be ignored, the response to Earth tides is strongly governed by a dimensionless aquifer frequency Qu. The response to atmospheric loading is strongly governed by two dimensionless vertical fluid flow parameters: a dimensionless unsaturated zone frequency, R, and a dimensionless aquifer frequency Qu. The differences between Qu and Qu are generally small for aquifers which are highly sensitive to Earth tides. When Qu and Qu are large, the response of the well to Earth tides and atmospheric loading approaches the static response of the aquifer under confined conditions. At small values of Qu and Qu, well response to Earth tides and atmospheric loading is strongly influenced by water table drainage. When R is large relative to Qu, the response to atmospheric loading is strongly influenced by attenuation and phase shift of the pneumatic pressure signal in the unsaturated zone. The presence of partial penetration retards phase advance in well response to Earth tides and atmospheric loading. When the theoretical response of a phreatic well to Earth tides and atmospheric loading is fit to the well response inferred from cross-spectral estimation, it is possible to obtain estimates of the pneumatic diffusivity of the unsaturated zone and the vertical hydraulic conductivity of the aquifer.

Additional publication details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Response of the water level in a well to Earth tides and atmospheric loading under unconfined conditions
Series title:
Water Resources Research
DOI:
10.1029/WR026i008p01803
Volume:
26
Issue:
8
Year Published:
1990
Language:
English
Publisher:
American Geophysical Union
Description:
15 p.
First page:
1803
Last page:
1817