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<br />upstream and downstream data can be accomplished using the computer <br />program described in Appendix 4 of this Volume or Appendix 1 of Vol- <br />ume 1. <br /> <br />Section 2.12. Reservoir routing <br /> <br />Reservoir routings are made to determine the outflow that would <br />result from a specified hypothetical flood hydrograph. with a specified <br />reservoir stage at the start and specified operation ru~es. Hypothetical <br />flood computations described in this report are restricted to those <br />where operation rules are based on conditions at the reservoir and <br />not on conditions at remote locations downstream. Thus. outflow is <br />a unique function of reservoir storage in these circumstances. Rout- <br />ing of hypothetical floods through the reservoir and spillway is needed <br />to determine maximum pool elevation during the spillway design flood. <br />Freeboard requirements are added to establish the elevation of top of <br />dam. The spillway design flood may be based on the probable maximum <br />flood, standard project flood or a flo~d of lesser magnitude depend- <br />ing on the resulant loss in event of failure from overtopping. <br />The most simple and satisfactory technique for performing a reser- <br />voir routing is a special form of the Modified Puls method. In order <br />to perform this routing, a curve or table of storage indication versus <br />outflow is first constructed from stage-storage-outflow data. Storage <br />indication is the sum of storage and one-half of the corresponding <br />outflow. when the storage is expressed in volume units equal to one <br />unit of outflow lasting for one computation interval. When these units <br />are used. inflow and outflow can be directly added to or subtracted <br />from storage without converting units each time. The routing equation <br />is based only on the law of continuity and the assumption that aver- <br />age outflow for a computation interval is equal to the average of in- <br />stantaneouS outflow quantities at the start and end of that interval. <br />The equation is derived as follows: <br /> <br />2-20 <br />