Description

Calculates the additional outflow necessary to meet an unmet load, if any exists. The function limits the additional release to ensure that additional downstream flooding does not occur.

Type

LIST { LIST { SLOT, NUMERIC, OBJECT } }

Arguments

Type

Meaning

1

STRING

the name of the computational subbasin

Evaluation

The function does the following:

1. Prioritizes the power reservoirs in the basin according to the relative Load shortage using the equation below.

If Load is unknown because the Seasonal Load Time method is selected, it is calculated. The calculated shortage then is a value less than one. The reservoirs with the highest values are first, the lowest reservoirs last.

2. Runs the selected Additional Hydropower Release Calculation on the each power reservoir in the subbasin to calculate the proposed additional release required to meet the load within outflow constraints.

3. In order of priority, hypothetically makes the additional release, visits downstream control points until it reaches a tandem reservoir or the end of the subbasin, whichever comes first. If the release causes (additional) flooding at a control point, it reduces the release until flooding is not caused or the release becomes zero. Resulting releases are then hypothetically routed to downstream control points to make adjustments to their available space hydrographs.

A control point’s available space hydrograph (in units of flow projected into the future based on the routing coefficients on the control point) is calculated as:

Inflow includes the value of the Inflow slot (at the time of the last dispatch) and the additional inflow resulting from the hypothetical additional releases from upstream reservoirs. It also contains the proposed flood control release hydrograph from the last pass of the flood control method.

Note, if the “” method is selected in the “” on the control point (, the control point is ignored, i.e. flooding is allowed at that control point.

Evaluation (cont)

4. Once all power reservoirs have been visited (in priority order), the HydropowerRelease function returns to the calling rule. For each reservoir in the subbasin, three triplets may be returned:

• Additional Power Release: This is the additional release to meet the load. If the proposed release is positive, but the additional power release was constrained to zero, the triplet {reservoir.Additional Power Release, 0.0, reservoir} will be returned. If the proposed release is zero, the Additional Power Release (of zero) triplet will not be returned.
• Outflow: If the new Outflow is the same as the existing Outflow, no Outflow triplet is returned because the value of the Outflow slot will not change as a direct result of this rule. Otherwise the value for outflow is the existing Outflow plus the additional power release.
• Load: the Load triplet is only returned if the method () is selected on the reservoir.

The calling rule is expected to make the assignments of the values to the slots

Comments

This function is dependent on having the predefined function FloodControl() and its associated methods execute first. The flood control operation sets up the network topology necessary data. HydropowerRelease requires that the reservoirs in the subbasin have already dispatched and have valid values in the Regulation Discharge, Outflow, Energy, and Load slots.

Use of this function for USACE-SWD is described .