Hydrology of Small Oceanic Islands — Influence of Atmospheric Pressure on the Water Table

Document Type

Article

Publication Date

11-1978

Digital Object Identifier (DOI)

https://doi.org/10.1111/j.1745-6584.1978.tb03256.x

Abstract

There is a spectrum of sea‐level fluctuations that affect the water table of a small, permeable oceanic island. At the high‐frequency end of the spectrum are the semi‐diurnal and diurnal components of the astronomical tides. Also affecting sea‐level elevation are atmospheric pressure and the temperature and salinity (hence density) of the ocean column.

Changes in atmospheric pressure cause sea‐level changes on the order of up to about 30 cm, by what oceanographers call the “inverted barometer effect.” As a result, pressure changes, like tides, generate waves that migrate across the water table. Amplitudes of the resultant pressure‐related water‐table fluctuations diminish inland. However, owing to the relatively long period of the pressure‐related fluctuations, their inland attenuation is far less than that of the hydraulically analogous tides. In fact, in Bermuda for example, the pressure‐related water‐table fluctuations completely dominate water‐table statistics that reflect day‐to‐day changes in elevation.

Because a drop in pressure and corresponding rise in the water table accompanies passage of a storm front, which also brings a rainfall, there is commonly a coincidental, and very misleading, correlation between rainfalls and water‐table rises. In island and coastal settings, non‐tidal sea‐level changes and their effect on the water table must be taken into account, if recharge is to be correctly evaluated from water‐table data.

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Citation / Publisher Attribution

Groundwater, v. 16, issue 6, p. 417-423

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