臺灣西部沿海海水入侵與地下水排出模擬分析;Numerical Simulation Analysis of Seawater Intrusion and Groundwater Discharge in Western Taiwan

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題名:	臺灣西部沿海海水入侵與地下水排出模擬分析;Numerical Simulation Analysis of Seawater Intrusion and Groundwater Discharge in Western Taiwan
作者:	林柏帆;Lin,Po-Fan
貢獻者:	應用地質研究所
關鍵詞:	沿岸地下水流;海灘坡度;沿海非受壓含水層;潮汐變化;HYDROGEOCHEM;Coastal groundwater flow;beach slope;unconfined aquifers;tidal variations;HYDROGEOCHEM
日期:	2015-07-17
上傳時間:	2015-09-23 15:02:53 (UTC+8)
出版者:	國立中央大學
摘要:	沿岸地下水流動情形會受自然因素如季節性水位變化、潮汐及波浪作用。為探討海岸坡度、潮汐作用與水文地質條件對台灣西部沿海非受壓含水層海水入侵及地下水排出量影響，本研究蒐集2009年台灣西部北起桃園中壢臺地，南至嘉南平原沿海相關水文地質資料，包括133口觀測井與10個潮位站之潮位資料，選取距沿岸1 公里內之平均高程變化為海岸坡度範圍，作為模擬參數設定之參考；資料分析結果顯示地下水位值範圍分布於0公尺至30公尺，平均高潮範圍為0.6公尺至2公尺，平均低潮位範圍為- 0.2公尺至0.08公尺，平均坡度則普遍分布在20 %以下，最高可達33 %。本研究使用HYDROGEOCHEM模式模擬台灣西部沿海垂直二維含水層之海水與地下水之交互作用情形，探討不同坡度、海岸長度與潮位條件下之鹽楔範圍與地下水排出量，分析水文地質條件如水力傳導係數與內陸地下水水力梯度對地下水排出影響。模擬結果顯示，固定海岸坡度，水力傳導係數對於地下水排出量影響顯著，當水力傳導係數較大時(51.84、65.15公尺/天)，地下水排出率較大，隨海平面上升時之出流率減少現象較大；而內陸水力梯度之增加則可有效地使地下水排出增加，並降低密度流影響。當固定坡度與水文地質條件下，海平面位置每上升0.5公尺時，單位厚度地下水排出率出現逐漸減少之趨勢，平均流量約減少0.008立方公尺/天。坡度影響方面則是當坡度較大時(5%~16%)，其含水層內的氯離子濃度線移動距離較短；海平面每上升平均0.5公尺時，氯離子濃度線約可向內陸前進15-20公尺；若是處於平緩坡度(0.5%~2%)的情況下，則氯離子濃度線隨海平面位置上升之移動距離較長，海平面每上升0.5公尺時，氯離子濃度線約可向內陸前進50-60公尺，最遠約可前進100公尺。若為極端陡峭之坡面(坡度33%)時，海平面每上升0.5公尺時氯離子濃度線往內陸之前進距離約僅5公尺。;Coastal groundwater flow are often affected by natural factors, including seasonal groundwater variations, tide and wave fluctuations, or human activities such as agricultural, aquacultural, and industrial water use. This study aims to assess the effects of beach slopes, tidal variations, and hydrogeological conditions on the seawater intrusion and discharge in unconfined aquifers. The hydrogeological data were collected along the westen coastal line of Taiwan. Collected data from DEM, 133 wells, and 10 tide stations show that the average beach slope is less than 20% in western Taiwan. The largest beach slope can reach to 33%. Based on the locations 1 km away from the shoreline, near shore groundwater tables vary in the interval of 0 to 30 m. The average high tide levels are in the range of 0.6 to 2 m and the average low tide level are in the range of 0.2 to 0.08 m. In this study, HYDROGEOCHEM numerical model was used to simulate the interaction of seawater and groundwater in unconfined two-dimensional profile aquifers in western Taiwan. , Simulation results show that the hydraulic conductivity significantly influences the groundwater discharge rate. The increase of inland hydraulic gradient can effectively increase groundwater discharge rate and reduce the density effect. With fixed slope and hydrogeological conditions, 0.5 meter sea level rise can lead to reduction of flow rate about 0.008 m3 / day. When the slope is large (5% to 16%), the chloride ion concentration line (or the saltwater front) in aquifer moves in a short distance. An increase of 0.5 m sea level rise, the saltwater front move landward about 15-20 m. In the low slope(0.5% to 2%) situation, a 0.5 m sea level rise can induce a landward saltwater front movement of 50 to 100 m. Under the condition of extremely steep slope (about 33%), the increase of 0.5 m sea level causes a 5 m seawater front movement.
顯示於類別:	[應用地質研究所] 博碩士論文

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