缺水風險指標之建立及其應用於評估桃園地區水資源系統

Developing the Shortage Risk Index and Its Application to Taoyuan Water Resources system

李孟恩(Meng-en Lee)

指導教授 ： 吳瑞賢

國立中央大學/工學院/土木工程學系/碩士(2011年)

摘要

台灣常以美國工兵團制定之缺水指標(Shortage Index, SI)做為水資源系統優劣之評估標準。然而該指標無法明確分別描述系統在模擬時間的缺水特性，如：缺水發生之機率、缺水延時或缺水強度。為此利用可靠度、恢復度、脆弱度結合風險管理概念定義缺水風險指標。藉此顯示系統發生錯誤的機率、從錯誤狀態中恢復為正常運作狀態之機率或連續缺水天數之倒數、受損程度與不同等級風險定義下的系統錯誤狀況。
利用下游需水量增加之情境以比較有無規線操作的供水策略在各項指標的差異。其結果顯示不同風險等級的缺水容忍度與規線操作下的階段性限水有著極大的關係。如以缺水容忍度20%做為系統不可接受風險之標準時，即表示視缺水率大於20%時為系統出錯（X_t∈F），此時在規線操作下第一階段限水（八折供水）則會被視為系統出錯。若以缺水容忍度30%做為系統不可接受之標準時，即表示缺水率大於30%時才視為系統出錯，而此時規線操作下第一階段限水則視為系統正常運作（X_t∈S），直到第二階段限水（五折供水）時，才視為系統出錯。
據結果顯示，可靠度應考慮系統在第二階段限水之後的缺水狀況，所以計算時以缺水率超過30%時為系統出錯之判定標準。而恢復度是表示系統恢復一般運作時之機率，所以認為只要進入限水階段即視為系統出錯，故計算時應以缺水率超過20%時做為系統出錯之判定標準。採取規線操作的供水策略，因為先行採取了限水措施，所以其可靠度與恢復度皆小於沒有規線操作的供水策略，但其優點為大幅降低缺水時期的缺水率，使得最終加總計算後有規線操作的策略下，其缺水風險指標（Shortage Risk Index, SRI）將優於沒有規線操作的結果。

關鍵字

供水系統 ； 風險分析 ； 脆弱度 ； 恢復度 ； 可靠度

並列摘要

In order to estimate the water supply system, many indices about water usage or deficit are calculated, and these indices are employed to describe the characteristic about the water shortage of the system. Shortage Index (SI) developed by Hydraulic Engineering Center of U.S. Army Corps of Engineers is a widely conventional index applied in Taiwan. However, it could not express the details about the water shortage events. For this reason, reliability, resiliency and vulnerability are used to represent how likely the system to fail, how quickly the system recovered from failure, and the scale of its damage, respectively. These criteria could be defined as Shortage Risk Indices, SRI, by being combined with the concept of risk management.
The Taiyuan system was tested as a case study. The result showed that different deficit tolerance levels had a close relationship with the release policy of the reservoir. For instance, if the tolerance level was set to 20%, then taking the first hedging step should be treated as a failure situation. But if the tolerance level was set to 30%, then taking the first hedging step would be recognized as a acceptable situation. In this case, the failure situation would be related to the second hedging step taken.
According to the results, the tolerance level us proposed to be set to 30% when concerning reliability, and it would reflect how likely the system to fail. And the tolerance level to be set to 20% when concerning resiliency to represent how quickly the system could work again.

並列關鍵字

reliability ； resiliency ； risk analysis ； water supply system ； vulnerability

參考文獻

21. 林冠慧，「全球變遷下脆弱性與適應性研究方法與方法論的探討」，全球變遷通訊雜誌，第43卷，33-38頁，2004。

36. 謝進南，「高屏溪水資源系統供水可用度分析研究」，財團法人曹公農業水利研究發展基金會研究報告，1999。

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