因應環境與社會變遷之穩定供水與減災總合政策研究-子計畫:區域地下水補注機制探討及管制與運用策略研究(I)

Abstract

彰雲地區主要用水來源為地下水，由於大量抽取地下水，導致海水入侵及地 層下陷等災害，為防止災害擴張及惡化，妥善地管理地下水資源實乃刻不容 緩之工作。由過去之研究經驗顯示，要明瞭研究區域內地下水資源，則須全 面的了解水文地質架構及地下水補注來源，爰此，本研究第一年應用地下水 觀測站網之井測資料及岩心樣本等資料，建立彰雲地區之水文地質模型，再 以此模型配合土地利用及雨量等資料，參考DRASTIC 架構推估彰雲地區之 主要補注區。第二年應用彰雲地區之地下水位資料，以水平衡分析為基礎， 推估抽水量與補注量，並以所推估之補注量檢討前述主要補注區之正確性。 此外，本研究以MODFLOW 建立彰雲地區之地下水流模式，以為後續地下 水相關策略之模擬。本研究主軸雖以地下水為核心，惟研究流域尺度之地下 水資源運用時，須同時考量地表及地下水之聯合運用，方可評估地下水之取 用量，故本研究於第三年參考彰雲地區地表地下水聯合營運及水資源經理等 相關文獻，擬定研究區域之地下水管制及運用策略，再應用條件氣候繁衍降 尺度模式(CWGDM)推估研究區域未來雨量，並以地表地下聯合營運模式 (GWSM)模擬前述策略，最後以IPCC 之脆弱度定義，評估彰雲地區之水資源 脆弱度。

Groundwater is the main water source of Changhua and Yunlin Areas. This groundwater extraction results in land subsidence and sea water intrusion. To avoid the expansion of land subsidence and sea water intrusion areas, water management is an emergency issue. This study proposes a three-year plan to develop a proper water management strategy which can avoid overdraft of groundwater in the study area and also mitigate the groundwater related damages. First year, this study will collect and analyze the borehole geophysical logging data from the network of observation wells and the related core samples. Based on these data, a hydrogeological model will be developed. Along with land use data, rainfall record, and the DRASTIC framework, this study will identify the main recharge areas of the study area. Second year, the study focuses on the water balance. The groundwater level data collected in the first year will be used to estimate the water volume of groundwater extraction and recharge. The estimated volume will be analyzed and compared with the identified recharge area from the first year study. Furthermore, a MODFLOW groundwater numerical model will be developed to study the physical groundwater flow and head distribution in the study area. Third year, this study will develop a conjunctive use strategy of surface and groundwater model which is called General Water Supply Model (GWSM). The developed strategy also considers climate change. A Conditional Weather Generation Downscaling Model (CWGDM) will be used to estimate the water availability under climate change conditions. The vulnerability defined by Intergovernmental Panel on Climate Change (IPCC) will be used to evaluate the management strategy for the study area.