本文研究目的為推導供水水庫考慮供水與蓄水二營運目標之最佳限水策略理論解，水庫營運目標以常態化偏離供水與蓄水目標值之權重和為代表，所推導得之最佳限水策略為水庫可利用水量(定義為水庫蓄水量加入流量並扣除蒸發量)的線性函數，因此可利用其二端點來定義限水策略，本文稱為起始可利用水量(SWA)及終止可利用水量(EWA)。水庫供水與蓄水目標何者較易達成會使起始可利用水量位於不同位置，本文稱供水目標較易於達成的限水策略為二點法第一類最佳限水策略，而第二類最佳限水策略則適用於蓄水目標較易達成的狀況。由於可利用水量包括未知的入流量，因此用於決定水庫放水量隱含不確定性，在已知水庫蓄水量的條件下，本文以入流量的機率分佈配合前所推導之理論限水策略來量化限水的不確定性。本文以石門水庫及其1964~2007年入流量資料為例說明不同參數值的選定對限水策略及限水效果的影響，並探討在不同水庫蓄水量、不同月份之限水不確定性，本文所建立之理論最佳限水策略及不確定性分析可提供水庫營運者建立水庫營運策略及有效管理水資源。

This study aims to derive the analytical optimal hedging rules of a reservoir for simultaneously considering the water supply and carryover storage targets. Weighted sum of normalized water-demand and carryover-storage targets is employed as an objective function to derive the reservoir optimal hedging rules. The derived optimal hedging rules are linearly varied with water availability, which is defined as the reservoir storage plus inflows and minus evaporation losses. Thus the optimal reservoir hedging can be expressed in terms of two end points, called the starting water availability (SWA) and ending water availability (EWA). The value of starting water availability depends upon which target is easily to satisfy. In this study, two-point type I hedging rules are preferable to the water-supply target, while two-point type II hedging rules are preferable to the carryover storage target. In addition, unknown future reservoir inflow involved in water availability leads to uncertainty of reservoir releases. In this study, this uncertainty is quantified by inflow distribution and derived optimal hedging rules. The proposed methodology is applied to the Shihmen reservoir associated with 1964-2007 inflow records. Effects of various combinations of parameters on hedging rules are explored in this study. Hedging uncertainty for various reservoir storages for each calendar month are also discussed. The results show that the derived optimal hedging rules associated with the uncertainty analysis provide useful information for efficient water-resources management.

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