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<br />190 <br /> <br />("';) <br />,~ <br />tv nature of Powell inflows. The average Lake Powell storages from ten <br />I" <br />~ simulations using different streamflow sequences were examined. <br />1-'0 <br /> <br />The estimate of average storage from a single simulation of 200 <br /> <br />years has a confidence interval of ~ 1% of the average value. Averages <br /> <br />from the remaining nine simulations are found to vary from run to run <br /> <br />(Figure 6.4), and some of the differences may be judged statistically <br /> <br />significant. The largest difference observed is 1.6 MAF or 7% of the <br /> <br />average storage. <br /> <br />As before, the convergence of the estimate may be observed by <br /> <br />treating the simulations as replications. Figure 6.5 shows that the <br /> <br />value of the averag~ S , appears to converge after eight or nine rep1i- <br />n <br /> <br />cations. <br /> <br />The variability of the estimate, ~ , is observed to decrease <br />n <br /> <br />very little as the number of replications increases. <br /> <br />Estimates of average storage, like the estimates of average <br /> <br />discharge, vary from run to run, but the differences are small and <br /> <br />replication contributes little to the accuracy of the result. <br /> <br />6.2.3 Examination of the Lower Extremes of the Reservoir Discharge <br />Distributions <br /> <br />An important reservoir management concern is the probability <br /> <br />that the reservoir fails to meet target discharges, called simply <br /> <br />reservoir failure. To determine this probability accurately it is <br /> <br />necessary that the extremes of the probability distribution of dis- <br /> <br />charge become stable or cease to change with increasing numbers of <br /> <br />observat ions. <br /> <br />The legal imposition of reservoir discharge requirements and the <br /> <br />development of water rights in the Colorado River Basin place great <br />