Hydraulic Tomography for Estimating the Diffusivity of Heterogeneous Aquifers Based on Groundwater Response to Tidal Fluctuation in an Artificial Island in Taiwan

Jet-Chau Wen,Keng-Li Lin,Tian-Chyi Jim Yeh,Yu-Li Wang,Hong-Ru Lin,Shao-Yang Huang

doi:10.1155/2018/6046258

Jet-Chau Wen, Keng-Li Lin + Show 4 more

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https://doi.org/10.1155/2018/6046258

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Abstract

This study investigated the hydraulic properties of the heterogeneous aquifers of an artificial island (Yunlin Offshore Industrial Park) in Taiwan. The research was based on the groundwater level response affected by tidal fluctuation using the hydraulic tomography (HT) to analyze the hydraulic diffusivity (α). Specifically, the power spectrum ratio of groundwater and tidal fluctuations derived from the Gelhar solution was used to estimate α in homogeneous aquifers; this, however, could not be applied in the artificial island. Next, the spatial distribution of the groundwater level response affected by tidal fluctuation was analyzed and found to be irregular, proving the existence of hydrogeological heterogeneity in the artificial island. Furthermore, the results of the estimated α using the HT showed low error and high correlation, 0.41 m2/hr and 0.83, respectively, between the optimal estimated heterogeneous and reference α fields in the synthetic aquifer. Last, the HT was used in the real tested scenario. By comparing the predicted groundwater levels of the optimal estimated heterogeneous α field and the observed groundwater levels of the real aquifer, it was found that the correlation was higher than 0.99. Therefore, the HT can be used to obtain the optimal estimated heterogeneous α field in the artificial island.

Highlights

The efficient planning of groundwater resources is necessary, and aquifer hydrogeological parameters provide valuable information when addressing groundwater resource management issues
While the previously mentioned studies focused on the homogeneous hydrogeological parameters under uniform aquifers, the purpose of this study was to prove the existence of hydrogeological heterogeneity in artificial islands, as well as to develop a method for estimating the heterogeneous α field using the hydraulic tomography (HT), when the groundwater level response is affected by the tidal fluctuation
The results of 8 observation wells presented values higher than 0.9. This occurred because the aforementioned observation wells were relatively close to the boundary of the artificial island, so they were susceptible to tidal fluctuation

Summary

Introduction

The efficient planning of groundwater resources is necessary, and aquifer hydrogeological parameters provide valuable information when addressing groundwater resource management issues. For estimating the hydraulic parameters from heterogeneous aquifers, Meier et al [4] assumed that T is heterogeneous and S is homogeneous in a synthetic aquifer. They collected the late time drawdown data results of observation wells in pumping tests and used Jacob’s method to estimate the T and S results. They found a strong spatial variability of the estimated S result. It often becomes problematic when determining the hydrogeological parameters of heterogeneous aquifers using analytical solutions of traditional homogeneous hypotheses [5]

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