Estimation of the Hydrogeological Parameters in Confined Aquifer Using Groundwater Variations after Earthquake
Date Issued
2012
Date
2012
Author(s)
Chang, Yu-Ling
Abstract
This study proposes a new methodology to estimate transmissivity and storage coefficient of confined aquifer. The hourly groundwater level observations after Chi-Chi earthquake in 48 hours are collected. It is found out the groundwater variations after earthquake acts as that of pumping test. Such phenomenon explains the earthquake is like a regional uniform pumping test, and the drawdown can be used to identify the hydrogeological parameters of aquifer.
Two conceptual models are established to simulate the uniform pumping test within the radius of influence (R) of monitoring well, one is radial uniform pumping; the other is spatial uniform pumping. Moreover, the pumping wells clusters are simplified by linear superposition as an equivalent single well with the same drawdown observed at monitoring well. The equivalent quantity of pumping is both equal to summation of all pumping rate; while the equivalent distance from monitoring well to pumping well is 0.36788R for radial uniform pumping and 0.60650R for spatial uniform pumping, respectively. The simplification is verified by a virtual case and shows success in identifying transmissivity and storage coefficient.
Lastly, the proposed parameter estimation method is applied to Jhuoshuei River alluvial fan for identifying transmissivity and storage coefficient of confined aquifer. The identified value of parameters falls in a reasonable range of typical sand-deposited aquifer, which shows the proposed method is suitable for a preliminary assessment of hydrogeological characteristic. Additionally, the identified parameters varies significantly from different locations, which supposes further investigate of the groundwater system to clarify the hydrogeological distribution is suggested.
Furthermore, compare the results of viewing earthquake as a pumping test with that of in-situ pumping test, the identified parameters are generally smaller. This may infer the scale effect of hydrogeological characteristics, that is, the analysis of earthquake provides a larger-scale character of aquifer and is more close to the scale of groundwater flow simulation of a groundwater district.
Subjects
Confined aquifer
Transmissivity
Storage coefficient
Earthquake
Pumping test
Type
thesis
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