The influence of barometric pressure fluctuations, earth tides and rainfall loading on fluid pressures in coastal plain aquifers, Burke County, Georgia

Conference · Mon Mar 01 04:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:6112923

Benson, S M; Moore, J; Daggett, J; Snipes, D S ^[1]

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1. Clemson Univ., SC (United States). Dept. of Earth Sciences

High precision pressure measurements from several aquifers in the top 225 m of coastal plain sediments reveal that barometric pressure fluctuations, earth tides and rainfall loading create pressure fluctuations on the order of tens of centimeters. If not correctly identified, erroneous conclusions regarding the magnitude of pressure communication within and across aquifers during pumping tests may be inferred. Aquifer pressure data with an equivalent resolution of 0.1 mm change in water level were measured in 4 wells over a 10 day period at the USGS Miller's Pond Test Site. During this time, barometric pressures fluctuated by the equivalent of 20 cm of water. Aquifer pressures mimicked these changes, with corresponding barometric efficiencies ranging from 0.59 for the deepest well (215 to 224 m) to 0.73 for the shallowest (136 to 145 m). After removing barometric influences from the pressure data, periodic pressure fluctuations of 2 cm were observed. These correlate well with fluctuations in the earths gravitational field created by planetary motion. A twelve component earth tide model was used to calculate the magnitude of the gravitational fluctuations and provide a quantitative basis for comparing them to observed aquifer pressure fluctuations. Additionally, three rainfall events caused rapid and relatively large increases in aquifer pressures. Up to 4 cm increase in the aquifer pressure accompanied the heaviest rains. The pressures increased concurrent to the rains and decayed slowly to background levels over a several day period, indicating a loading response instead of an infiltration induced pressure increase. The relatively large magnitude of these influences, compared to the small changes induced by leakage across confining layers requires careful consideration in the data analysis.

• OSTI ID: 6112923
• Report Number(s): CONF-9304188--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 25:4
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
AQUIFERS
ATMOSPHERIC PRECIPITATIONS
ATMOSPHERIC PRESSURE
DEVELOPED COUNTRIES
ERRORS
FLUCTUATIONS
GEORGIA
NORTH AMERICA
PRESSURE MEASUREMENT
RAIN
TESTING
TIDE
USA
VARIATIONS