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<br />fl oods of record, or the hypotheti ca 1 Standard Project Fl ood (occurri ng <br />5 days in advance of the spi11~ay design flood), shows that such a <br />level (or higher) might prevail at the time the spillway design flood <br />occurs. If the spillway design flood estimate is associated with a <br />particular season, the determination of initial pool level ~lou1d consider <br />flood conditions on comparable dates. <br />In ~any instances the assumption of initial reservoir levels <br />corresponding to arbitrarily selected percentages of the flood control <br />capacity Hill serve to demonstrate the effects that alternative assump- <br />tions would have on maximum reservoir surcharge levels, and may eliminate <br />the need for more detailed studies of probable initial pool levels when <br />the effects are relatively small or moderate. In this connection, it is <br />usually desirable to assume, for one routing of the spillway design flood <br />that the design flood control capacity is 50 percent filled at the begin- <br />ning of inflow. There are several reasons for concluding that the flood <br />control design storage capacity of a reservoir is likely to be at least <br />50 percent filled at the beginning of the spill~/ay design flood, regard- <br />less of the size of the capacity involved. Uormally there \/il1 be a <br />relatively large number of floods capable of filling at least one-half <br />the design flood control space, and most reservoir regulation plans call <br />for optimum control of these moderate floods. In some cases. reservoir <br />capacities originally assigned to flood control are reassigned in part <br />to conservation or similar uses, further increasing the likelihood that <br />at least 50 percent of the original design capacity will be filled at <br />the beginning of the spillway design flood. It is also probable that <br />hydrologic and meteorological conditions required for development of <br /> <br />6-12 <br />