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Show c m « 1 A t i v t F 1 o v Timt l Figure 6.1 The stretched thread method ( after Klemes 1979, Figure 2) In Figure 6.1, the first section of the optimal mass curve of outflow ( opt Y) represents the first release condition, the second section, the third release condition, and the third section the second release condition. The characteristics of the optimal regulation policy stated above are obvious from an examination of the release pattern indicated in Figure 6.1. Actual reservoir operation is then performed by first developing rule curves using the storage depletion for each year determined from an analysis represented by Figure 6.1, determining the maximum and minimum yields qmax an^ ^ min a s t n e largest and smallest slopes of opt Y from Figure 6.1, and then operating the reservoir such that the release y falls within the range qj^ n £ y £ qmax> sn^ me storage levels are maintained as prescribed by the rule curve developed. Klemes ( 1979) indicates that it is possible to determine a rule curve at a certain level of reliability ( frequency of violation) and assess the reliability of the actual operation following the rule curve, through simulation and trial and error. Klemes ( 1979) also provides a sequential search algorithm for computerization of the stretched thread method. This search scheme is summarized below. 1. Let SQ and S j represent reservoir storage at times t= 0, and t= T, respectively. SQ and S j are constrained to lie in the corridor defined by Xe and Xf. The shortest path between SQ and Sj through the corridor defines the optimal release policy. Choose SQ and Sj. Define Ao= Xe| t= o - So, and Aj= Xe| t= x - Sj. 2. Join AQ and Ay with a straight line AQAJ. The slope of this line represents a trial value of the optimal yield in the period 0 to T. 3. Scan from t= 0 to t= T to see if AQAJ crosses Xe or Xf. If no crossing point is 157 |