• Multiple constraints lead to non constant release patterns. This method determines the constant additional release required to meet each constraint. The actual additional flow that will be added to the surcharge release is the sum of the values for each constraint. Therefore, the final release schedule may not be a constant value if there are multiple constraints in effect.

• Surcharge pattern leads to non constant release patterns. The originally computed Surcharge Release schedule is not constant, so adding flows to the surcharge release will result in a non-constant release schedule.

• Forecast values are overwritten at each timestep. The Surcharge Release method, including this method, is executed at each timestep and will update the values in the Surcharge Release and other slots throughout the forecast period. Therefore, at the end of the run, the results may not be obvious what is happening. If you want to see the schedules used for a particular timestep, pause the run after that timestep has executed, then look at slot values or the special results in the model Run Analysis tool; see Model Run Analysis—Special Results Details Dialog in USACE‑SWD Modeling Techniques for details.

• Constraining elevations may not be exactly met. Surcharge Release operations do not include Evaporation or Precipitation in the computation. Similarly, reservoir diversions (withdrawals) are performed after surcharge operations. Once the other operations execute and the reservoir dispatches and solves, the resulting elevation may be slightly different than the values used in the Surcharge and elevation max duration computations. This will manifest in not exactly reaching the constraining elevations. Because diversions (and evaporation) remove water from the reservoir, typically the elevations will be slightly below the constraining elevations.

• Duration constraints still aren’t met. Maximum outflow constraints are applied after this additional release schedule is computed. Thus, even if the an additional amount is required, it may not be released and the target elevation may not be achieved. The proposed values are stored in the Surcharge Release slot, the actual maximums would be stored in the Outflow slot.

• Elevations are unexpectedly at (or below) the constraint. The algorithm looks at the pool elevation after forecasting and surcharge have executed. (This preconstrained pool elevation is currently not available but looking at the forecasted inflows gives some indication of the values.) It then determines the additional flow to prevent violating the constraint at any time in the forecast period. If the elevation is already at the constraint, then the additional flow will likely keep the elevations at or even below the constraint. The method will add releases to the current timesteps (and future) timestep. There is no mechanism to delay releasing water to wait until the flood actually arrives. Thus, if it seems like the elevation should stay above the constraint, the algorithm will start releasing to make room for forecasted inflows.

• There are still violations in the forecast period. Only one violation per constraint is considered, though in theory there could be another violation later in the forecast period.