考量因氣候變遷導致河川流量停止流動的頻率增加，並造成水資源與生態的危害，有必要針對河川流量的間歇性進行分析。間歇性是指河流會週期性停止流動或乾涸，在全球範圍普遍存在。由於臺灣的降雨分布不均、河流長度短且山坡陡峭，使河流容易在暴雨時出現洪水並在長期沒有降雨時出現斷流現象。因此，需要辨識出主導臺灣河流發生間歇性的特徵。本研究對全臺灣從1960至2022年的65個流量測站資料，分別使用間歇率(Intermittency Ratio, IR) 、Richards-Baker Flashiness(RBF) Index、乾季六個月的季節性(Six-month Seasonality of Dry periods, SD6)與方向統計，說明流量間歇性、變化性與季節性並對上述水文指標執行趨勢分析說明隨時間的趨勢，用來了解臺灣的河流現況與時空變化。另外，進一步對集水區屬性使用主成分分析(Principal Component Analysis, PCA)，確認主導集水區差異的環境變數，並與氣候數據、乾旱指標進行相關性分析，確認間歇性與上述指數的關聯性，說明時間與空間上主導間歇性發生變化的特徵。
本研究的結果顯示，臺灣的河流屬於弱間歇性(0 < IR ≤ 0.5)，流量變化範圍小，大多的低流事件集中於冬季時期發生，並且主要發生在1月至3月份。東部集水區的低流天數占比會隨著時間增加，但季節性不隨時間變化。延長冬季六個月的間歇性特徵分析，顯示出具有較大間歇性之集水區主要發生在土壤含水量較少、潛勢蒸發散較大或滲透率較大之區域。在氣候相關性結果顯示，臺灣的間歇性與未降雨的頻率(L1mm)呈顯著相關，代表未降雨導致低流事件發生。在乾旱的相關性結果顯示，間歇性的大小能夠說明乾旱的嚴重程度，並且能代表水文乾旱。本研究提供各個河流的間歇性分析結果與冬季間歇性的主要影響因子，可為河川及水資源管理提供參考。

Considering the climate change that increases the frequency of river flow stops and causes harm to water resources and ecosystems, analyzing the river intermittency is necessary. Intermittent rivers are rivers which periodically stop flowing or dry up, are common worldwide. In Taiwan, uneven rainfall distribution, short river lengths and steep slopes cause rivers to experience flooding during heavy rainfalls and stop flowing during long periods of non-rainfall. Therefore, identifying the characteristics of driving river intermittency in Taiwan is necessary. This study aimed to analyze the spatiotemporal variations in river conditions across Taiwan using the Intermittency Ratio (IR), Richards-Baker Flashiness (RBF) Index, Six-month Seasonality of Dry periods (SD6) and directional statistics to indicate river intermittency, variability and seasonality. The analysis was based on streamflow data from 65 gauging stations covering the period from 1960 to 2022. Trend analysis was conducted to illustrate temporal changes in the selected hydrological indicators. Principal Component Analysis (PCA) was applied to catchment attributes to identify dominant variables influencing catchment differences. Correlation analysis was performed with the climate data and drought indicators to identify the correlation between the intermittency and the above indicators, and to illustrate the temporal and spatial characteristics driving intermittency changes. The results show that the rivers in Taiwan have weak intermittency (0 < IR ≤ 0.5) with small flow variability, and most of the low flow events are concentrated in the winter period and occur between January and March. The ratio of low flow days has increased over time in catchments at east of the Central Mountain Range, but seasonality remained unchanged over time. Characterization of intermittency during the six-month winter period indicates that higher intermittency occurs in catchments with lower soil moisture, higher potential evapotranspiration or higher permeability. Climate correlation analysis shows that the significant relationship between intermittency and the frequency of rainless rainfall (L1mm), indicating that lack of rainfall causes low flow events. Drought correlation analysis shows that intermittency magnitude reflects drought severity and serves as a strong indicator of hydrological drought. This study provides the results of intermittency analysis and identifies the main factors affecting winter period intermittency in Taiwan's rivers, offering valuable reference for river and water resources management.

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