A study on seawater intrusion with sharp interface by perturbation concept
Date Issued
2005
Date
2005
Author(s)
Li, Tsui-Yin
DOI
zh-TW
Abstract
Recently, landsubsidence and aquifer pollution due to seawater intrusion caused by groundwater over pumping of farm fishing business have happened in coastal areas of Taiwan such as Ping-dong, Budai, Yunlin, etc.
The so-called seawater intrusion in this study is seawater invading from the coastal line. There are two ways to investigate this kind of seawater intrusion：the first way assumes there is a sharp interface between fresh water and seawater, and the second way allows mixing of seawater and fresh water. In this study, we choose the first way.
Because the little density difference between seawater and fresh water, other than using conventional methods, we apply perturbation concept to solve our seawater intrusion problem. Neither solving seawater and fresh water simultaneously, nor assuming the seawater stationary（Gyben assumption）, in this study, we compute fresh water potential first, then compute the perturbation part due to density difference of seawater and fresh water, and finally combine both parts to get the completed solution.
In our three dimensional computation, the finite analytic method which preserves local analytical solution and unconditional convergence is applied to our horizontal two dimensional computation, while the second order polynomial is used as the vertical interpolation function. Hence we can not only solve problems with multiple layers of aquifers but also obtain vertical variation of water head for each layer.
The characteristics of our method can be summarized as follows：1. the method is only valid for seawater intrusion with sharp interface, 2. Duipuit’s assumption is not necessary, 3. Gyben assumption is not necessary（i.e. it is not necessary to assume stationary seawater）, 4. fresh water and seawater perturbation are solved in sequence instead of solved fresh water and seawater simultaneously as conventional method does.
The model established in this study is examined by the analytical solutions of Wilson and Sa Da Costa（1982）, Strack（1976）and Strack（1989）. The computation capability of this model is also tested by the cases of a circle island and a discontinuous multiple layered soil.
Subjects
明顯交界面
海水入侵
擾動法
sharp interface
seawater intrusion
perturbation method
SDGs
Type
thesis
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