考慮潮汐擾動在非均質沿海滲漏含水層系統之解析解

Abstract

滲漏含水層系統通常包含頂部的非侷限含水層、底部的侷限含水層，以及在前兩者間的滯水層。過去滲漏含水層通常假設為均質，且在水平方向無限延伸；然而由於地層沉積的變異，使沿海滲漏含水層有可能為非均質。本文考慮滲漏含水層內的侷限水層及滯水層為非均質，並將此兩水層分割為數個具均質的水平區域，且假設非侷限含水層之水頭為定值，發展了一個解析解模式，以描述侷限水層中水位的變動。研究結果顯示，不連續滯水層之長度愈長及位置離海岸愈近將造成侷限含水層水位變動之振幅減小及相位差增大。此外，本研究也指出在一沿海滲漏含水層系統中，非均質順向侷限水層亦會造成潮汐入侵距離之縮短及較低之水位變動。

The coastal leaky aquifer system includes an unconfined aquifer on the top, a confined aquifer at the bottom, and an aquitard in between. This aquifer system was usually assumed to be homogeneous and of an infinite extent in the horizontal direction. The aquifer system may however be heterogeneous due to depositional and post depositional processes. This study considers that the aquitard and confined aquifer are heterogeneous and both formations are divided into several homogeneous regions. A one-dimensional analytical model is developed for describing the head fluctuation in such a heterogeneous leaky aquifer system. The water table of the upper unconfined aquifer is maintained constant. It is revealed that both the length increasing and location nearing coast line of the heterogeneous aquitard have significant decreasing on the amplitude and increasing phase shift of the head fluctuation in the confined aquifer. Besides, this study indicates a heterogeneous trending confined aquifer may probably cause a shorter tidal intrusion distance and lower head distribution in a coastal leaky aquifer system.