Tandem Storage Considered
This category appears only if the Route Tandem Storage method is selected in the Tandem Storage Management category. When water scheduled for tandem storage is routed, its arrival times are known.
The flood control algorithm balances reservoirs based on their projected storages at the end of the balance period. In a sense, the end of the balance period is the end of the time when there is some confidence in the forecasts. The question arises: if we release water today to store downstream, we know it will arrive, so do we care when it arrives? Should the fact that we released it be enough to consider it stored at its destination? This category lets us choose one of two ways of answering that question. Myriad other possibilities (such as considering only water released on the first timestep, or scheduling storage only on the first timestep or only during the balance period) are not implemented.
Arrives in Forecast Period This is the default method.
The flood control algorithm considers all the water that arrives at a tandem within the forecast period to contribute to the tandem’s storage. This means that water released after the end of the balance period is considered also.
There are no slots specific to this method.
Method Details
RB is forecast to be at level 10.0 and RC is forecast to be at level 5.0 at the end of the balance period. The key control point balancing method assigns level 7.0 to all three reservoirs. On the first pass, at balance level 7.0, RC takes on 100 units from RB, released as { 40, 30, 20, 10}. Since the forecast period is 5 days long, the arrival hydrograph for this release schedule from RB is {4, 19, 30, 25, 15}, leaving 7 units that are routed off the end of the forecast period. Thus, in future calculations based on the forecast storage in RC, 93 units of volume will be added to RC’s forecast storage. RC will be free to release on day 1 an additional 4 units of volume, and on day 2 an additional 19 units of volume, and so on. If the Two-Reservoir Midpoint method is selected, the starting volume for RC will henceforth include 93 units of volume above its forecast volume at the end of the balance period.
Arrives in Balance PeriodThe flood control algorithm considers only that water that arrives within the balance period to contribute to the tandem’s storage. This means that water released within the balance period is the only water considered.
There are no slots specific to this method.
Revised: 07/09/2023