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. 002J~7 (1) The required release cannot be made due to capacity constraints (2) A portion of the actual water released did not reach the demand element because an intervening down- stream reservoir restricted routing due to capacity constraints In either case, the reservoir making the release is removed from the list of available reservoirs. That portion of the demand not met becomes the new demand which is to be satisfied by operating the remaining available reservoirs. This procedure is continually repeated until the demand is satisfied, or there are no reservoirs remaining. . When flows are routed through a reservoir, only the normal zones and capacities apply. Thus, even if water is below the variable constraint level, water may be routed through the reservoir if sufficient capacity exists. Similarly, the demand array only pertains to making releases from storage and not to routing. It should also be noted that although this discussion ta1k~ of routing water through a reservoir, in reality water is released from . storage at the originating reservoir to exactly replenish water released from the lower reservoir to meet downstream demands. The routing concept is a computational expedient. When the downstream boundary is reached, the computed flow is compared to the target value specified on input. If the computed value is less than the target value, the difference is treated as a demand. Segment data are then used in the usual way. During the normal computation process the demand in a river reach or reservoir may not be met, or the downstream boundary target flow may not be satisfied. The unsatisfied demand or target flows are retained as a variable called the deficit flow on out- put. Subsequent spills may occur, which if used properly, could reduce or satisfy the deficit flow.. However, when reservoirs are operated in a logical manner, this is unlikely. It should also be noted that there may be outflow from a reach even if there is a deficit flow.since.releases .from a reservoir above the reach to elements below it may be specified. ~ -' ..~.u ~. .~-- -.------. . After computations for the downstream boundary are completed, each reservoir is checked to see if the reservoir balancing option has been selected. The procedure commences with the upstream boundary and is applied progressively in the downstream direction. If a reservoir is using this option, the balanced operation philosophy is applied to determine the portion of the normal operating zone that is full in both the upstream reservoir using this option and the speci- fied downstream reservoir with which it is to be balanced. If the upstream reservoir storage is greater, the required release to balance 3-5 (rev. 07/75)