抽水行為對雲林地區地層下陷之影響

臺灣地區由於降雨時空分配不平均，造成乾早時期地表水資源不敷使用，部份地區乃大量抽取地下水，其中以屏東及雲林等地區超抽地下水造成地層下陷的現象最爲嚴重，爲此本研究及探討雲林地區抽水量與地層下陷之關係，研究方法採用MODFLOW模擬地下水水流及修改過之INTERBED模擬地層的下陷量，藉以了解抽水行爲與地層下陷之相關性。選定麥寮、臺西、四湖、口湖、水林等五處地層下陷嚴重地區爲模擬分析之對象，研究結果顯示以6億噸的抽水量連續二年抽水所導致的地層下陷，停止抽水兩年後，僅四湖及水林有些微囘漲，最大囘漲量分別佔總下陷量的0.5%及4%。模擬在降低20%抽水量之驟降與漸降行爲下，結果顯示驟降之抽水行爲雖較有效之方式，但僅能減緩地層下陷量而無法的有效囘復下陷。故麥寮、臺西及四湖應列為優先取締非法水井之管制地區，以避免該區地層下陷繼續惡化。本研究並推估雲林地區的之年安全出水量大約3億噸左右。此量化的數據可作爲未來決策者分配水資源或核發水權之參考。

關鍵字

抽水；地層下陷；雲林

並列摘要

The uneven distribution of water resource and the uncertainty of the amount of groundwater withdrawal have caused the overpumping of groundwater and compounded the difficulty of groundwater management in the recent years. Land subsidence is the serious problems in Yun-Lin and Pen-Tung. The object of the study is to establish the relationship between pumping behavior and land subsidence in Yun-Lin. The MODFLOW model is adopted to simulate groundwater flow and the revised INTERBED model is used to simulate land subsidence. The results show that land subsidence is almost unrecoverable. The amounts of formation rebound are only 0.5% and 4% after first two years of 0.6 billion tons pumping and second two years zero pumping scheme in Sz-Hu ane Sheu-Lin. The constant decrease scheme is a more effective than gradual-decrease to reduce the amount of subsidence. Mai-Liau, Tai-Shi, Sz-Hu are priority areas to regulate the amount of groundwater withdraw. The 0.3 billion tons per year is the suggested safe yield in Yun-Lin. The above results may be useful for groundwater management and water right application.

並列關鍵字

Pumping ； Land subsidence ； Yun-Lin

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