本研究區域以珊瑚砂堆積成的一個小型島嶼為題材,探討地下水補注之效益。此區水資源全來自於降雨,然而由於雨量在時間與空間的分佈不均,造成大部份的水流都直接逕流入海,無法作有效保存與利用,本研究探討自然降雨給予補注涵養地下水,防止地下水鹽化與地下水的有效管理利用,提昇整體供水潛能之開發。 在水平衡分析結果,島上之水資源大部分都因逕流入海而損失,佔支出比例之56.84%,其次損失為蒸發損失之42.02%。流出量已超出入流量32.8萬立方公尺/年,雖然地下水抽水量僅為2.5萬立方公尺/年(佔1.09%),因入滲補注量不足,東沙環礁島淡水出水量已經超越安全值。以地下水補注概念分析,若開發四處補注池其入滲面積均為2,037平方公尺,可獲得6,730立方公尺/年地下水補注量,以此方案可滿足每年地下水抽水量2.5萬立方公尺/年。若在海水和抽水井之間設置不透水牆,產生一永久性地下屏障,則兼有保持地下水量及增加地下水位之功效;用年降雨量1,346公釐,主要入滲區域面積80,000平方公尺,考量折減系數為0.3(包含蒸發截流地表進流因素),則可獲得32.7萬立方公尺/年地下水儲存量。
Student ID No.: N9733017 Title of Thesis: A Study on Water Resources of Dongsha Atoll Island Total Pages: 51 Name of Institute: National Pingtung University of Science & Technology Name of Department: Department of Civil Engineering Date of Graduation: June, 2010 Degree Conferred: Master Name of Student: Liu Chi-Ming Adviser: Dr. Ting Cheh-Shyh The Contents of Abstract in this Thesis: The proposal of study is to evaluate groundwater resources utilization at Dongsha Atoll Island. All of the water resource in Dongsha come from rainfall in rainy season, due to the soil consists of coralline with high porosity causes hallow groundwater flow into the ocean. Therefore, how can collect the rain in the ground then store into the aquifer is key point in this study. In term of the results of water balance, the maximum outflow is ground runoff, in total is 1,518,228 m3/year approximates 56.84% into ocean, and the evapotranspiration next approximate 42.02%. The out flow of groundwater amount to 32.8×104 m3/year is in excess of natural recharge in aquifer, in artificial recharge point of view, this case can obtain balance out by pumping; In total is 25,000 m3/year. Additionally, the study simulated to construct the impermeable wall in the aquifer, can be gained the groundwater store 32.7×104 m3/year when the annual rainfall was 1,346mm. Key word: Dongsha Atoll Island, Water Balance, Groundwater Recharge