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WRRCTR No.86 Response to Tides of Coastal Aquifers: Analog Simulation vs. Field Observation

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Title:WRRCTR No.86 Response to Tides of Coastal Aquifers: Analog Simulation vs. Field Observation
Authors:Williams, John A.
Liu, Ta-Chiang
LC Subject Headings:Aquifers -- Electromechanical analogies.
Tides -- Hawaii.
Analog computer simulation.
Tides -- Mathematical models.
Aquifers -- Hawaii -- Oahu.
Date Issued:Jun 1975
Publisher:Water Resources Research Center, University of Hawaii at Manoa
Citation:Williams JA, Liu TC. 1975. Response to tides of coastal aquifers: analog simulation vs. field observation. Honolulu (HI): Water Resources Research Center, University of Hawaii at Manoa. WRRC technical report, 86.
Series:WRRC Technical Report
Abstract:This report presents a summary of the work to date on the response to tides of coastal aquifers. In particular, it presents the results of experiments performed to study the influence of an oscillating water table on storativity (i.e., effective porosity), the application of both harmonic and spectral analyses to water surface time histories measured in the field near Ewa Beach and in Honolulu Harbor, and an electric analog model designed to simulate the shallow, coral-limestone aquifer at Ewa Beach, Oahu, Hawaii. Results indicate that the effective porosity for an oscillating water table will, in general, depend on the frequency of the oscillation with dependence being strong or weak as either or both the specific yield and the transmissivity are larger or smaller, respectively. Also, water surface time histories can be considered to be composed of a fundamental (diurnal) component and a second harmonic (semidiurnal) component and a 24-hr record analyzed and that the resulting average values of the amplitude and phase angles be used. The spectral analysis confirms that the semidiurnal power suffers a greater attenuation than the diurnal power.

It is concluded that the technique of determining aquifer properties from tidal response data is a valid one, but that the results will be less reliable than those ascertained from pump test data. The optimum results are considered to be those based on both tidal data and pump test data, as one method serves as a check on the other.
Pages/Duration:iii + 67 pages
Appears in Collections: WRRC Technical Reports

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