Spectral analysis of water level fluctuations in aquifers |
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| Authors: | D C-F Shih G-F Lin |
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| Institution: | (1) Institute of Nuclear Energy Research, AEC, P.O. Box 3-7, Lungtan, 325, Taiwan, Republic of China E-mail: cfshih@iner.gov.tw, TW;(2) Department of Civil Engineering, National Taiwan University, Taipei 10617, Taiwan, Republic of China, TW |
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| Abstract: | The water level of a seawater gauging station and 18 groundwater wells coupled with atmospheric pressure in southwestern
Taiwan are analyzed by using spectral analysis in time and frequency domain. The semidiurnal component is found to be the
most significant signal from the measurement of water level and atmospheric pressure, and the diurnal component is less distinctive
in part of water level and atmospheric pressure record. Although auto-spectral and cross-spectral density functions are significant
in atmospheric pressure and water level, the pressure variations do not significantly affect the seawater and the majority
of groundwater level in the study area with amplitude of time series observations. The astronomical tidal components are likely
the main factor causing seawater and groundwater level to fluctuate in Pingtung, Taiwan. Time lags are estimated from 20 min
to a few hours in aquifers. It concludes that the disturbance on groundwater levels from the effect of oceanic astronomical
tide is different from the varying hydrogeological characteristics of aquifer. In this study, the spectral analysis of water
level in time and frequency domains gives strong indications of sensitive variations to water level fluctuation.
This research is supported by the Institute of Nuclear Energy Research (INER), AEC, Taiwan, Republic of China, under a fund
from Executive Yuan. The authors thank Taiwan Central Weather Bureau and Taiwan Provincial Government Water Resources Department
for providing useful data. |
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| Keywords: | : Groundwater Spectral analysis Tide |
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