Improvements in a simple harmonic analysis of groundwater time series based on error analysis on simulated data of specified lengths

Abstract

Tidal response method is an efficient technique for investigating hydraulic properties of an aquifer in insular and coastal areas of highly permeable geological settings. The present study extends a simple and straightforward harmonic-analysis technique recently introduced as part of a tidal response method applied to a freshwater-lens aquifer. This simple analysis technique was examined with artificially synthesized time series composed of multiple realistic tidal components. The analysis outputs of major diurnal and semidiurnal components are sufficiently accurate if the analyzed time-series length is appropriately restricted. Limitations of the simple harmonic analysis in the applicable time-series length arise from tidal-component interference that occurs in analyses over a finite length. Definitively recommended simple harmonic-analysis technique with appropriate combinations of time-series lengths and extractable tidal components are convenient for investigating hydraulic properties of an aquifer, such as on a remote island where the freshwater lens is the only freshwater resource.