以擴展經驗正交函數法分析屏東平原地下含水層時空變化特徵

ANALYSIS OF THE SPATIAL-TEMPORAL GROUNDWATER VARIATION PATTERNS BY EXTENDED EMPIRICAL ORTHOGONAL FUNCTION IN PINGTUNG PLAIN AQUIFER

10.6652/JoCICHE.202211_34(7).0008

林永清(Yong-Qing Lin)；葉姿妤(Tzu-Yu Yeh)；方詠俞(Yung-Yu Fang)；林遠見(Yuan-Chien Lin)

側向補注 ； 沖積扇 ； 資料探勘 ； 擴展經驗正交函數 ； 地下水資源管理 ； lateral recharge ； alluvial fan ； data mining ； extended empirical orthogonal function ； groundwater resource management

中國土木水利工程學刊

34卷7期（2022 / 11 / 01）

639 - 648

英文

許多研究顯示隨著全球氣候變遷的影響，臺灣降雨型態面臨著豐者愈豐、枯者愈枯等旱澇愈加分明的情形，且因臺灣地形多山脈橫亙，山高水急變化特殊，雖然臺灣年降雨量十分豐沛，但正面臨著降雨時空不均、水庫淤積以及超抽地下水等嚴峻的水資源管理問題。長期以來，隨著養殖漁業、農業與工業的發展，台灣西部沿海部分地區地下水之超抽，導致地層下陷、土壤鹽化、用水調度等問題，因此造成談到地下水的利用皆彷彿避之唯恐不及。然而，臺灣有潛在豐富的山區地下水資源甚至是山麓沖積扇頂地下水仍尚未被妥善開發利用。此外，地下水的降雨垂向直接補注容易透過降雨量分析，但區外的側向補注量卻一直很難有效評估。妥善分析利用整體地下水資源進行有效控管以及對地下水補注量及抽用量的評估可能成為未來政府及學界解決水資源缺乏的重要課題。因此，本研究以新的時空資料探勘方法－擴展經驗正交函數法（Extended Empirical Orthogonal Function, EEOF）分析地下水位資料，並以屏東平原為例，結合歷年來降雨量與地下水觀測資料進行分析，嘗試建立降雨與地下水變動之時空變化關係。藉由此分析架構，瞭解降雨與地下水變動之主要時空特徵關係，並能進一步分析屏東平原地下含水層補注與山麓沖積扇頂地下水側向流動情形。結果顯示，屏東平原東側沿中央山脈沖積扇頂有主要的山區側向補注特徵，其中以平原東北部的荖濃扇與口社扇，其次東南部的林邊扇及力力扇補注量最大，且以延遲15-30天達到最高峰後逐漸消退。經由本研究分析方法，可很好提供降雨與地下水之間的時空主要變異特性之資訊，尤其是地下水側向補注的資訊。

Due to the influence of global climate change, many studies show that the types of rainfall in Taiwan have clearly been extreme situation. In addition, mountains have took large portion in Taiwan's topography type, and the streamflow changes rapidly. Although there is abundant precipitation in Taiwan, the water resource management is still confronted with some difficulties such as uneven distribution of precipitation, reservoir sedimentation, and over-pumping of the groundwater. For a long time, as the development of aquaculture, agriculture, and industry, the over-pumping of the groundwater in the west coastal area of Taiwan has led to issues such as land subsidence, soil alkalization and water resources operation problem. Therefore, the usage of the groundwater has unfavorable impression. However, the rich groundwater resources in mountainous areas and the top of alluvial fan haven't been properly developed and utilized in Taiwan. Furthermore, the direct groundwater recharge form rainfall is easy to analyze with precipitation amount, but the lateral recharge is difficult to evaluate effectively. The appropriate analysis and utilization of the groundwater resources for establishing an effective control and the assessment of groundwater resources recharge as well as pumping amounts may be important issues for the government and academia to solve water scarcity in the future. In this study, we propose a new spatial-temporal data mining method--Extended Empirical Orthogonal Function (EEOF) method to analyze the groundwater level, and use annual rainfall amounts as well as the observation data of groundwater levels to analyze their connection in Pingtung plain. Through this analysis framework, we can understand the main relationship of the spatial and temporal characteristics between rainfall and groundwater fluctuations. This study further analyzes the recharge of the aquifer and the lateral flow of groundwater at the alluvial fans in Pingtung Plain. The results shows the main features of lateral recharge in the mountains are located at the top of alluvial fan of Central Mountain Range on the eastern side of the Pingtung Plain. Among the alluvial fans, the largest recharge amount of groundwater is measured at the Laonong fan and Koushe fan in the northeastern part of the plain, followed by the Linbian fan and Lili fan in the southeastern part of the plain. The recharge amount reaches the peak at 15 to 30 days delay and gradually decreases afterwards. Under the approach proposed in this study, especially for the lateral recharge of groundwater, the main spatial temporal of rainfall and groundwater variation characteristics can be well provided.

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