應用一維地電阻於水力傳導係數推估－以濁水溪沖積扇第一含水層為例

水力傳導係數為一重要之水文地質參數，傳統上多以抽水試驗求得，因抽水試驗需要鑿井，其成本昂貴，加上試驗場地取得不易等問題，限制了參數的數量。近年來已有實驗室或現地尺度之研究，整合地表地電阻及抽水試驗資料推估水文地質參數，惟前人研究大都忽略泥層影響，而沖積扇之扇央與扇尾通常為泥層出現頻率較高的區域，因此泥質之影響應加以考量。本研究依沉積物分布，將研究區域分區，再將試驗資料依區域分區進行分群，並建立各分群之水力傳導係數推估式。接著再應用此水力傳導係數推估式，建立濁水溪沖積扇第一含水層於主扇範圍，包含舊濁水溪以南至新虎尾溪以北區域之水力傳導係數分佈。分群結果顯示，濁水溪沖積扇之主扇，在第一含水層可分為扇頂與扇頂以外區域兩個分群，各分群之水力傳導係數與地層因子之回歸關係成線性相關。水力傳導係數推估部份，比較本研究推估之水力傳導係數、現地試驗資料及應用文獻推估式之推估值等，結果顯示本研究與現地試驗值之誤差介於11～58 m/day之間，遠較文獻推估式所得結果合理，顯示本研究所建立推估式之正確性與適用性。本研究所推估之水力傳導係數場，可作為濁水溪沖積扇後續地下水相關研究，如地下水數值模式建模之依據，所發展之水力傳導係數推估流程，亦可推廣至其他相似沖積扇，而有助於更廣泛的地下水相關研究。

關鍵字

地表地電阻；水力傳導係數；地層結構因子；濁水溪沖積扇

並列摘要

Hydraulic conductivity (K) is an important aquifer parameter and is usually obtained using conventional pumping test. However, only limited amount of data can be collected, because pumping test is time consuming and expensive. In recent years, some studies estimated K by using pumping test data and surface electrical resistivity survey. These studies cost less because less pumping tests are required. However, majority of these studies don't consider the effects caused by layers of clay. In fact, clay layers are commonly distributed in middle-fan and distal-fan. Therefore, this study divides Zhuoshui River Alluvial Fan into several zones based on the sediment distribution. A linear regression equation is derived from the pumping test data and formation factors for each zone. This study applied these equations to develop the distribution of K in the shallow aquifer of major fan, which is bounded by the Old Zhuoshui River at the north side and by New Hu-Wei River at the south side.The result shows that the shallow aquifer of the major fan of Zhuoshui River can be divided into two zones, which are top-fan and non-top-fan areas. The regression results show good correlation between K and the formation factor in each zone. These regression equations are then used to estimate K in the study area. The results are compared between the field measurement and the results obtained from Khalil's equations. The results indicate that the estimation error, between 11 m/day and 58 m/day, is much smaller than the estimation error obtained using Khalil's equation. The developed methodology for estimating K can contribute to related groundwater research and can be applied to other alluvial fans with similar sediment distribution to this study area.

並列關鍵字

surface electrical resistivity ； hydraulic conductivity ； formation factor ； Zhuoshui River alluvial fan

國際替代計量

應用一維地電阻於水力傳導係數推估－以濁水溪沖積扇第一含水層為例

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