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Simulation Objects
Groundwater Storage object - Wetted Sand Evaporation
On the Groundwater Storage object, Wetted Sand Evaporation method, three slots were added to model Soil Limited Evaporation. These slots are optional inputs; without inputs, the previous functionality is used.
If the user inputs the "Soil Limited Evaporation Elevation", an alternative equation may be used if the wetted area excluded is zero (reach above flow is zero) and the previous elevation is less than the Soil Limited Evap Elevation. Then evaporation is the
Soil Limited Evap Rate * Soil Limited Evap Factor * Wetted Area.
Otherwise, the existing equation is used.
Changing Elevation Volume and Elevation Area Methods
Functionality was added to allow the elevation vs volume and elevation vs area relationships on the storage and level power reservoir to have data that changes at various times within a run. When trying to match historical results, these methods can be used to simulate a re-survey of the reservoir bathymetry that occurs periodically. A new method, Time Varying Elevation Volume was added to the Sedimentation Calculation category. Also, a new category and method called Surface Area Modification and Time Varying Elevation Area method were added. In both of these methods, the user provides the survey date as a column header on a table. The column then represents the new data to use until the next column in the table becomes valid. For more information on using these methods, see Time Varying Elevation Volume in Objects and Methods and Time Varying Elevation Area in Objects and Methods.
Convergence Percentage Slot
The slot Convergence Percentage is now used correctly as a percentage. This tightens up convergence in many spill computations. Some models may now abort with an error when before they did not.
Method and Category Name Changes
The following method and category names on the reservoir objects were changed to be more consistent:
New Name
Sediment Calculation
Sediment Calculation
CRSS Sediment Calc
Evaporation and Precipitation
Monthly Evaporation
Monthly Evaporation In Annual Timestep
Single Evaporation
Daily Evaporation
Pan and Ice Evaporation
Pan and Ice Evaporation, Current Surface Area
Heat Budget Evaporation
Input Evaporation
Peak Base Power Calc
In the PeakBasePowerCalc, if the outflow was less than the first value on the Base Flow Table, it would use a very small value. Now it issues an error if the lookup value is not on the table. This change could lead to a new error condition. If you want to match old results, you can insert 0 outflow and 0 baseflow as the first row of the table.
Unregulated spill near the crest
For certain inputs, the unregulated spill near the spillway crest was not correct. Note, this change can lead to slightly different numerical results. See Unregulated in Objects and Methods for more information on the change.
Thermal Object - Load Evaluation
A new category, Modified Load Evaluation, was added to the Thermal object. Within this category, the Calculate Modified Load method subtracts the net hydropower generation from the System Load. Also, within optimization, it allows you to write constraints to level the load to the extent possible.
Revised: 08/02/2021