SEPARATION OF FLUCTUATION COMPONENT OF GROUNDWATER LEVEL USING SPECTRAL ANALYSIS

Abstract

 It is sometimes difficult to understand fluctuation of groundwater and recharge processes caused by the precipitation, because the groundwater level is affected by many factors, including the effects of tides and groundwater extraction. In the present study, we applied the spectral analysis in order to separate the groundwater level fluctuation components connected to the tidal effects and groundwater extraction. As a result, during the period when the pumping effect was not observed, the groundwater level without the tidal component could be obtained by performing the inverse Fourier transform after removing the peak of the tide spectrum and the corresponding groundwater level spectrum. On the other hand, during the period when the pumping effect was observed, the tidal component and the pumping component could not be clearly distinguished, but removed as a fluctuation component. Furthermore, the relationship between precipitation and groundwater level was examined.