天然刺激源引起之地下水位變動時空分析－以濁水溪沖積扇為例

Spatiotemporal Analysis of the Groundwater Head Variation Caused by Natural Stimuli - A Case Study of Choushui River Alluvial Fan

蕭金財(Chin Tsai Hsiao) ； 蔡瑞彬(Jui-Pin Tsai) ； 張良正(Liang Cheng Chang)

《農業工程學報》 66卷4期 (2020/12) Pp. 21-35

https://doi.org/10.29974/JTAE.202012_66(4).0003

摘要

由於地下水位為含水層受到外部刺激影響下的綜合反應，因此其為一混合訊號。為了探討含水層受外部刺激源影響的種類與範圍，本研究應用獨立成分進行地下水位時空分析，並與降雨及河川水位觀測資料進行比對，以辨識獨立成分的物理意義；比對方法包含交叉相關性分析、頻率域交叉相關性分析，快速傅立葉轉換與小波轉換等。本研究以濁水溪沖積扇淺層含水層58口觀測井之時水位資料進行分析，分析期距為2005年至2014年，並取同時段之降雨及河川觀測資料作為獨立成分辨識之參照。研究結果顯示，此區域之地下水系統包含2個降雨成分及2個河川成分。接著本研究將這些成分轉換為觀測井水位變動量，再與原地下水位變動量計算相關係數，此成果可解讀降雨或河川對於區域地下水影響程度之空間分布，同時反應了區域之水文地質特性，後續本研究將以此分析為基礎，進一步進行抽水研究。

關鍵字

獨立成份分析 ； 相關係數 ； 頻率相關性 ； 小波轉換 ； 地下水

並列摘要

Groundwater head is a mixed signal since it is the response of an aquifer to the external stimuli. In order to identify the natural stimuli's types (i.e. rainfall and river stage) and their contribution to the head variation of an alluvial fan, the independent component analysis was used to analyze the head time series collected from the groundwater-monitoring well network. In order to identify the physical meaning of an independent component (IC), the derived ICs were compared with the observed river stage and rainfall time series based on the cross-correlation, coherence, fast Fourier transform, and wavelet transform. The proposed method was applied to analyze the groundwater levels collected from the 58 observation wells in the Choushui River Alluvial Fan during 2005-2014. The results show that two ICs highly correlate to rainfall, and the other two represent river stage' features. These four ICs were then transformed to four types of head variations of all the wells, and the four types of correlation coefficients between these derived head variations and original head observations at all the wells were calculated. The spatial distributions of these correlation coefficients reveal the contribution of the rainfall, river stage, and hydrogeological structure to the original head variation everywhere in the study area. The study results will be the foundation to analyze the pumping features of the study area in the near future.

並列關鍵字

Reservoir system ； Early warning model ； Standardized drought indices ； Pre-preparedness