Filtering methods in tidal-affected groundwater head measurements: Application of harmonic analysis and continuous wavelet transform
Autor: | Carlos Duque, Juan Pedro Sánchez-Úbeda, Manuel López-Chicano, M. L. Calvache |
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Rok vydání: | 2016 |
Předmět: |
Hydrology
geography geography.geographical_feature_category 010504 meteorology & atmospheric sciences Piezometer 0208 environmental biotechnology Wavelet transform Soil science Aquifer 02 engineering and technology 01 natural sciences 020801 environmental engineering Harmonic analysis Environmental science Extraction (military) Groundwater Continuous wavelet transform Sea level 0105 earth and related environmental sciences Water Science and Technology |
Zdroj: | Advances in Water Resources. 97:52-72 |
ISSN: | 0309-1708 |
Popis: | A new methodology has been developed to obtain tidal-filtered time series of groundwater levels in coastal aquifers. Two methods used for oceanography processing and forecasting of sea level data were adapted for this purpose and compared: HA (Harmonic Analysis) and CWT (Continuous Wavelet Transform). The filtering process is generally comprised of two main steps: the detection and fitting of the major tide constituents through the decomposition of the original signal and the subsequent extraction of the complete tidal oscillations. The abilities of the optional HA and CWT methods to decompose and extract the tidal oscillations were assessed by applying them to the data from two piezometers at different depths close to the shoreline of a Mediterranean coastal aquifer (Motril-Salobrena, SE Spain). These methods were applied to three time series of different lengths (one month, one year, and 3.7 years of hourly data) to determine the range of detected frequencies. The different lengths of time series were also used to determine the fit accuracies of the tidal constituents for both the sea level and groundwater heads measurements. The detected tidal constituents were better resolved with increasing depth in the aquifer. The application of these methods yielded a detailed resolution of the tidal components, which enabled the extraction of the major tidal constituents of the sea level measurements from the groundwater heads (e.g., semi-diurnal, diurnal, fortnightly, monthly, semi-annual and annual). In the two wells studied, the CWT method was shown to be a more effective method than HA for extracting the tidal constituents of highest and lowest frequencies from groundwater head measurements. |
Databáze: | OpenAIRE |
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