A probabilistic approach to rainwater harvesting systems design and evaluation

雨水貯水為一種可使用之水源，但其貯集效率經常受到降雨時空分布之影響，導致可貯集以提供利用之雨水量有限。以往常用最佳化或模擬之方法研討貯水容量設計，並多以平均之貯水容量與缺水程度進行討論；但降雨為一隨機歷程，貯水容量對缺水率之影響應為一連續性分布，以特定貯水容量之平均缺水率大小決定設計容量並不適當。是故，本研究提出機率觀念並導入系統評估之風險分析指標，藉此分析雨水貯集系統設計中之貯水容量設計，建立不同貯水容量之缺水率超越機率曲線與不同缺水狀態下貯水容量之超越機率曲線，同時亦建立系統評估指標之超越機率曲線，冀能藉此建立以機率為觀點雨水貯集系統之不確定性。究中首先以台北市都會區為例，模擬單一建物內人口，利用不同大小之雨水貯水容量設計，以替代衛生沖廁用水量之可行性進行分析討論；爾後，選擇台南都會區作為例證，期能透過區域之差異性，除將方法應用於不同區域，亦進一步探討其結果之異同。究結果顯示在不同超越機率情況下，當設計之貯水容量達90立方公尺時，缺水率以達穩定，即增加貯水容量對改變缺水率已無成效。當貯水容量設計達20立方公尺，台北都會區缺水率變化率最大；台南都會區則需達90立方公尺才有相當之成效。台北都會區與台南都會區之貯水容量設計分別達50立方公尺與90立方公尺時，其綜合評估指標呈現穩定。另外，若以單位面積之貯水容量來探討，台北都會區達0.2（立方公尺/平方公尺）時，系統之缺水率或綜合評估指標有較佳之結果，台南都會區則需達0.6（立方公尺/平方公尺）。結果顯示，當區域之降雨豐枯比較大，系統需要較大之貯水容量。The imbalance among water supply and demand becomes a more and more serious problem in Taiwan owing to rapid growth of population and socio-economic activities. Rainwater harvest is an alternative water supply source to relieve this water shortage pressure in urban area. Since the effectiveness of Rainwater Harvesting System (RHS) design is heavily dependent on rainfall characteristics, both optimization and simulation were used to approach this problem of storage design for RHS. In the past, most of the studies present the average successful rate under a specific storage capacity. his paper presents a probabilistic analysis approach to construct the supply deficit probability distribution under a designed storage as well as the exceedence probability curve of deficit rate under different storage capacities. The fitted probability density function was transformed into exceedance probability (EP) curve for reliability evaluation on RHS designs. A more effective RHS design may be achieved and relieve regional water supply pressure. This information provides a holistic view of the RHS performance characteristic for more effective RHS design.n this research, cities of Taipei and Tainan were used as study areas for the demonstration of this methodology. Subsequently the probabilistic distribution curves for relationships between storage capacities and deficit rates as well as the relationships between storage capacities and system evaluation index were presented. The results show that deficit rate and comprehensive evaluation index is lower in Taipei with 0.2 （m3/m2） than in Tainan with 0.6 （m3/m2）. It indicates that the system requires larger storage capacity when ratio of high rainfall to low rainfall is higher.口試委員會審定書 i謝 ii錄 iii目錄 v目錄 viii要 ixbstract x一章 緒 論 1-1 研究動機 2-2 研究目的 3-3 架構與方法 5二章 文獻回顧 7-1 水資源系統規劃 7-2 雨水貯集系統 11-3 系統風險分析 14-4 小結 17三章 研究區域概述 20-1 區域簡介 20-2 氣候與降雨狀況 25四章 水資源供需分析與推估 28-1 供給面推估 28-2 用水需求面推估 32-3 供需模式 37-4 機率模型 40五章 系統分析 42-1 貯水容量與缺水率分析 43-2 系統評估指標 48六章 系統評估與結果討論 63-1 貯水容量與缺水率超越機率曲線 63-2 貯水容量與系統評估指標關係曲線 67-3 結果與討論 73七章 結論與建議 81-1 結論 81-2 建議 83考文獻 8