氣候變遷下水文乾旱的偵測、診斷與預測—水會計觀點

Abstract

通過考慮供水系統的資源稀缺抗性和季節性脆弱性閾值，本研究引入水會計 (Water accounting) 和 開發了 改良版水會計系統脆弱性評估 （modified WAVE+）模型。該模型基於水文-社會經濟活動互動及對偶雙系統的概念 (Hydrological-social interaction and dual system)，從供水系統的角度有效評估和量化水文乾旱的多重原因。本研究使用石門水庫供水系統的歷史數據驗證了modified WAVE+ 模型在乾旱檢測和診斷方面的性能。這種新方法能夠評估乾旱的嚴重程度、強度和持續時間，表現優於同時考慮了入流量、儲水量、消耗量的兩種乾旱指標：社會經濟乾旱指數 (SEDI) 和改進的多元標準化恢復力和可靠性指數 (IMSRRI) 等現有方法。本研究基於上述討論新開發的模塊化條件數據庫乾旱指數（MCDBDI）框架集成了水文隨機過程和modified WAVE+模型，可以計算乾旱發生的條件機率。條件概率可以支持用水量和水庫調度的實時政策調整。此外，本研究開發了一個對偶雙系統序列模擬過程來評估氣候變化和用水量變化情景下的乾旱事件特徵演變。結果表明，在預測的氣候變化情境（RCP 2.6 和 RCP 8.5）下，台灣北部乾旱事件的發生次數有明顯減少，而乾旱嚴重程度及乾旱持續時間在平均值與變異數相差不大的情況下極端嚴重以及極端長的持續時間有下降的趨勢。

By considering the water stress robustness and the seasonal vulnerability threshold of the water supply system, I developed a modified water accounting and vulnerability evaluation plus (WAVE+) model. Based on the dual system concept, the model effectively assesses and quantifies the multi-causalities of drought from the water supply system point of view. I validated the performance of the modified WAVE+ model in drought detection and diagnosis using the historical data from the Shihmen Reservoir water supply system. This new approach enables the evaluation of drought severity, intensity, and duration, outperforming existing methods such as the SocioEconomic Drought Index (SEDI) and Improved Multivariate Standardized Resilience and Reliability Index (IMSRRI). Additionally, the newly developed Modularized Conditional Data Base Drought Index (MCDBDI) framework, which integrates hydrologic stochastic processes and the modified WAVE+ model, enables the calculation of conditional probability for drought occurrences. The conditional probability could support real-time policy adjustments in water consumption and reservoir operations. Furthermore, I developed a sequential dual system simulation process to evaluate the drought characteristic evolution under climate change and water consumption change scenarios. The results indicate a reduction in occurrence numbers and the distribution tail shrinkage on event severity and duration in Northern Taiwan under the projected climate change scenarios (RCP 2.6 and RCP 8.5).