地下水水文地質與補注模式研究-補注區劃設與資源量評估(3/4)

Abstract

地質法第五條：「中央主管機關應將具有特殊地質景觀、地質環境或有發生地質災害之虞之地區，公告為地質敏感區。地質敏感區之劃定、變更及廢止辦法，由中央主管機關定之」。其中地質環境包括容易因自然作用或人為活動而遭致破壞之地下水補注區，應補充地質調查，提高調查密度和精度，劃設主要補注區，公告為地質補注區。基於此，中央地質調查所自102年起推動4年科技發展計畫「地下水水文地質與補注模式研究」，其主要工作目標為評估地下水補注區之水文地質特性，並瞭解區域地下水補注範圍及資源量，使地下水資源的管理朝向永續利用的目標。其執行策略採分年分區執行，4年內將針對臺灣重要地下水區蘭陽平原、台北盆地、台中盆地及嘉南平原地區進行調查，釐定主要地下水補注區範圍並評估地下水補注量。 為達成上述「地下水水文地質與補注模式研究」之計畫目標，中央地質調查所乃規劃本項4年期委辦計畫：補注區劃設與資源量評估，本項委辦計畫之目標包含以下各點： (一) 完成蘭陽平原、台北盆地、台中盆地及嘉南平原地區等4個地下水區之水文地質補充調查。 (二) 建立蘭陽平原、台北盆地、台中盆地及嘉南平原地區地下水區之地下水補注模式，分析其補注機制、水平衡分析、地下水流模擬及地下水位水質監測。 (三)劃設蘭陽平原、台北盆地、台中盆地及嘉南平原地區等4個地下水區之主要地下水補注範圍。 (四)評估蘭陽平原、台北盆地、台中盆地及嘉南平原地區等4個地下水區之補注量、推估現況抽水之總抽水量及可抽用水量。 為達成上述計畫目標，本項委辦計畫於各地下水區之主要工作項目包括： (一)彙整歷年水文地質、地下水和水文資料及成果。 (二)地球物理補充調查：包括一維地電阻補充調查、二維地電阻調查與淺層水文地質架構檢討及現地重力量測調查與分析。 (三)地球化學補充調查：包括地面及地下水水質採樣與分析、地下水溫度剖面調查及綜整蘭陽平原水文地質調查資料及蒐集氚濃度分析資料，以描述區域性水文地質及水質特性。 (四)地下水補注區及水平衡評估：包括水文地質資料庫建置、三維水文地質模型建立、地下水補注區劃設、地下水資源量評估、地下水流數值模式建置及主要補注區對區域地下水水量與水質之綜合影響分析。 本項委辦計畫於民國102年度已完成蘭陽平原之工作項目，本年度(103年)將以蘭陽平原之研究成果為基礎，完成台北盆地之補注區劃設與資源量評估。

Article V of the Geological Act indicates "The central government authority should announce sensitive areas for those areas having special geological landscape, geological environment, or geological disaster tendency. The authority should also clearly define the rules for delineation, change, and cancellation of the sensitive areas." The " special geological environment " includes groundwater recharge area which could be easily influenced due to natural events or human activities. To precisely identify these recharge areas, Central Geological Survey, MOEA initiates a four-year project named "The study of groundwater hydrogeology and the recharge model" starting from year 2013. The main tasks of this project are evaluation of the groundwater hydrogeology characteristics of recharge area and identification of the recharge area and the recharge volume. These tasks assist the groundwater management toward sustainable use. The implementation strategy is to investigate and assess one groundwater region a year for Lanyang Basin, Taipei Basin, Taichung Basin, and East Rift Valley during the project time frame. The targets of the entire 4-year project: 1.Complete supplement hydro-geological investigation for four groundwater regions, Lanyang Basin, Taipei Basin, Taichung Basin, and East Rift Valley (called the four groundwater regions hereafter), to comprehend the hydro-geological characteristics of the groundwater recharge areas. 2.Develop the groundwater recharge models for the four groundwater regions. The developed models can perform the recharge mechanism analysis, water balance analysis, groundwater flow simulation to identify the recharge zones based on the investigation results including water level observation and water quality monitoring. 3.Delineate the main recharge areas for the four groundwater regions. 4.Assess the current recharge, current extraction, potential extraction limits for future water resources management and conservation. Main tasks for the Taipei Basin in year 2014： 1.Collect related data including groundwater hydrogeology, hydrology, head observation, and related studies. 2.Geophysical investigation: Perform supplement 1D and 2D electrical resistance survey, review shallow layer hydro-geological structure, and investigate and analyze in-situ gravity. 3.Geochemical investigation: sample and analyze the surface water and groundwater, analyze geothermal gradient, and collect historical Tritium concentration data. 4.Assess the recharge area and the water balance: establish a hydro-geological database, develop a 3D hydro-geological model, delineate groundwater recharge area, evaluate the quantity of groundwater resource, develop a groundwater flow numerical model, and analyze groundwater flow and quality.