Spectral analysis of tidal fluctuations in ground water level

Water level data at 16 ground water wells and two sea water gauging station s, coupled with barometric measurements in an alluvial plain in the central -west region of Taiwan, are analyzed using spectral analysis in the time an d frequency domains. The semi-diurnal component from water level station is observed to be the most noticeable signal while the diurnal component is t he less distinct signal recorded at the water level stations. Both semidiur nal and diurnal components are coupled with atmospheric pressure measuremen ts. From the atmospheric pressure data, spectral analysis indicates that bo th the raw and the pressure adjusted water levels are almost in phase and r etain the same amplitude in this area. It implies that the effect of pressu re variations is not significant for the sea water and ground water level n earby; the astronomical tidal components, as expected, are the main factor causing fluctuation of ocean water and ground water levels in the Choshuihs i alluvial plain.