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<br />C~ <br />'-:J <br />N <br />I',) <br />N <br />W <br /> <br />192 <br /> <br />importance on the reliability with which target demands can be met. As <br /> <br />reported in Chapter 1, discharge requirements for Lake Powell have been <br /> <br />expressed as annual and ten year average target discharges. <br /> <br />The simulation program produces tables and plots of the cumu1a- <br /> <br />tive distributions of both the annual and ten year average discharges <br /> <br />of Lakes Powell and Mead. From these plots the probability of failure <br /> <br />to meet any given discharge can be read. <br /> <br />The ten simulations introduced in Section 6.2.1 were used to ex- <br /> <br />p10re the stability of the discharge distribution. For visual clarity, <br /> <br />only the distributions produced by four of the inflow sequences are <br /> <br />displayed in Figures 6.6 to 6.9. The four distributions displayed <br /> <br />include the cases of highest and lowest probabilities of reservoir <br /> <br />failure, and two other cases chosen at random. Cumulative probabilities <br /> <br />are displayed as the percentage of years for which discharge is less <br /> <br />than or equal to a specified value. <br /> <br />The distributions of annual discharge in Figures 6.6(a,b) and <br /> <br />Figures,6.7(a,b) show that target discharge,D , is maintained for a <br />t <br /> <br />large percentage of years. Discharges above the target indicate that <br /> <br />additional releases were required to obey maximum storage constraints. <br /> <br />Discharges below the target reflect incidents of reservoir failure, at <br /> <br />which times storage is reduced to the minimum or dead storage value. <br /> <br />The differences between the distributions of annual discharge <br /> <br />cannot be judged significant on the basis of a Kolmogorov-Smirnov <br /> <br />cumulative distribution test (see Section 2.3.5). However Figure 6.6(a) <br /> <br />displays a wide range of probabilities of Lake Powell failure. Failure <br /> <br />to meet the target discharge of 8.23 MAF varies 0.0+ to 10% for the case <br />