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

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 spatialtemporal of rainfall and groundwater variation characteristics can be well provided.