Barometric fluctuations in wells tapping deep unconfined aquifers

Water Resources Research



Water levels in wells screened only below the water table in unconfined aquifers fluctuate in response to atmospheric pressure changes. These fluctuations occur because the materials composing the unsaturated zone resist air movement and have capacity to store air with a change in pressure. Consequently, the translation of any pressure change at land surface is slowed as it moves through the unsaturated zone to the water table, but it reaches the water surface in the well instantaneously. Thus a pressure imbalance is created that results in a water level fluctuation. Barometric effects on water levels in unconfined aquifers can be computed by solution of the differential equation governing the flow of gas in the unsaturated zone subject to the appropriate boundary conditions. Solutions to this equation for two sets of boundary conditions were applied to compute water level response in a well tapping the Ogallala Formation near Lubbock, Texas from simultaneous microbarograph records. One set of computations, based on the step function unit response solution and convolution, resulted in a very good match between computed and measured water levels. A second set of computations, based on analysis of the amplitude ratios of simultaneous cyclic microbarograph and water level fluctuations, gave inconsistent results in terms of the unsaturated zone pneumatic properties but provided useful insights on the nature of unconfined-aquifer water level fluctuations.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Barometric fluctuations in wells tapping deep unconfined aquifers
Series title Water Resources Research
DOI 10.1029/WR015i005p01167
Volume 15
Issue 5
Year Published 1979
Language English
Publisher American Geophysical Union
Description 10 p.
First page 1167
Last page 1176
Country United States
State Texas
City Lubbock
Other Geospatial Ogallala Formation