圖書典藏及影音數位平台

近年世界各地極端氣候頻傳，旱災發生頻率增加，影響層面深遠，經常造成嚴重經濟損失。103年臺灣各地秋冬期間降雨偏少，導致長達9個月之枯旱情況，水情惡劣時期新北市板新、林口地區、桃園市及高雄地區被迫實施第三階段限水，採取供五停二措施以控制水源運用，旱象直至5月底梅雨鋒面抵達才逐漸舒緩。 面臨極端天氣，除強化現有之防災體系與因應作為，更需預先執行衝擊評估與風險分析，使災時損失降至最低，並提升抗旱韌性。為強化因應氣候變遷之抗旱手段與面對災變之危機處理能力，故研提本計畫；除分析可能水文情境，以探討惡劣條件下之水源枯旱風險與管理機制，並配合經濟分析，推估水源枯旱可能造成之經濟損失，以作為決策支援之參考資訊。此外，透過盤點計畫區域內相關因應措施，以舒緩枯旱之衝擊與影響，於未來嚴重枯旱發生時，可提供水資源運用之重要參考。其中，因應措施可考量「開源、節流、調度、備援」四大策略，並藉由風險管控、細緻管理機制、水文枯旱預警與超前布署機制等精進作為，以未來於104年情境下不進入三階限水為整體抗旱目標。

This project aims to build up an economic analsys and policy assessment system for water under various hydrological scenarios. The project evaluated the drought risk from the perspective of both water shortage and economic impact. With taking economic analysis into account, a more valuable information for water policy assessment or decision making can be provided. First of all, the project investigated hydrological characteristics of the project area and proposed various hydrological scenarios (e.g., below normal, few, delay and normal mei-yu conditions) based on the local hydrological characteristics of mei-yu and typhoon. Then, the project focused on drought risk assessment and economic analysis to quantifying possible water shortage or economic loss caused by drought events under various hydrological scenarios. Moreover, the project also focused on water policy assessment to rank the benefits of adaptation strategies. Various adaptation strategies such as reclaimed water or water saving will be implemented and examined under worse hydrological scenarios. Since the major rainfall seasons in Tainan are mei-yu (May to June) and typhoon (July to September) seasons, this project designs some hydrological scenarios to study potential drought risk. The designed hydrological scenarios are composed of below normal, few, delay and normal conditions for both mei-yu and typhoon seasons. The definition of proposed hydrological scenarios are given below: (1) the below normal condition: the cumulative probability of total rainfall amount is less than 30%. (2) the few condition: the cumulative probability of total rainfall is less than 10%. (3) the delay condition: the cumulative probability of the first month rainfall is less than 30%. (4) the normal condition: the exclusion of above conditions. Besides, the project also took climate change scenarios into consideration. The impact assessment shows that: (1) under the A2-CSMK35 scenario (the worst scenario), all the average values of below normal, few, delay and normal mei-yu conditions decrease, while the delay mei-yu condition decreases most significantly; the average values of below normal and few mei-yu conditions slightly decrease, but the average values of delay and normal mei-yu conditions increase significantly. (2) under the A2-CSMK35 scenario (the worst scenario), the occurrence probabilities of below normal and few mei-yu conditions increase but the occurrence probabilities of delay and normal mei-yu conditions decrease; the occurrence probabilities of below normal and few typhoon conditions decrease but the occurrence probabilities of delay and normal typhoon conditions plateau and increase, respectively. The expected value theory was used to quantify the drought risk of a water supply system under both hydrological and climate change scenarios. The drought risk is defined as the expectd value of water shortage and economic impact. In this project, the benefit of a strategy is evaluated by the increase in drought risk (i.e., expected water shortage or expected economic impact) due to a failure in strategy implementation. A larger increase in expected water shortage indicates the benefit of a strategy is higher. Eight different combinations of adaptation strategies were examined and then ranked. The evaluation results show: (1) the benefits of S2 and S8 strategies are relatively higher than others. (2) S3 and S4 strategies are of medium benefits in reduction of water shortage.