The Role of the Coastal Aquifer Structure on the Transfer Processes of the Tidal Signal Inferred from Harmonic Decomposition of Hydrogeological Time Series
<p id="p1">In volcanic islands, the quality of coastal groundwater displays a high degree of spatial heterogeneity. In this study, hydrogeological time series were recorded on a groundwater monitoring network including 13 boreholes: 10 in Reunion island and 3 in Grande Comore island. Calculated appa...
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| Main Authors: | , , |
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| Format: | Book Chapter |
| Language: | English |
| Published: |
IntechOpen
2024
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| Subjects: | |
| Online Access: | https://www.intechopen.com/chapters/89536 |
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| Summary: | <p id="p1">In volcanic islands, the quality of coastal groundwater displays a high degree of spatial heterogeneity. In this study, hydrogeological time series were recorded on a groundwater monitoring network including 13 boreholes: 10 in Reunion island and 3 in Grande Comore island. Calculated apparent diffusivity values reflect the diversity in the degree of confinement of the considered aquifers. Using a signal analysis script, 68 theoretical tidal constituents were identified in all the collected groundwater head time series. Analysis of the amplitude of the signal-to-noise ratio on the various tidal components in each borehole shows that the confined groundwater bodies are more sensitive to high-frequency tidal components, whereas unconfined groundwater bodies are characterized by a sensitivity to low-frequency tidal components only. The analysis of the groundwater electrical conductivity signal also revealed two types of behavior: In a first group of boreholes, the evolution of the salinity is essentially controlled by long-period oceanic variations, whereas in a second group of boreholes, groundwater quality is rather controlled by the seasonal freshwater recharge. These results contribute to a better understanding of the groundwater vulnerability to marine intrusions in these complex coastal environments, where the degree of aquifer confinement is found to play a key role.</p> |
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| ISBN: | 978-0-85014-345-4 |
| DOI: | 10.5772/intechopen.115097 |