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Inline Power Plant - Flow Tables and Flow vs Power Tables method
The Flow Tables and Flow vs. Power Table method was modified to use the Min Turbine Release at Max Generation as its constraining value. This is obtained from the Flow vs Power Table by finding the max power and then using the corresponding flow.
The algorithm is documented Flow Tables in Objects and Methods.
Stream Gage - Stage Methods
A new category, Stream Gage Stage, and method, Stage Table Lookup, were added to the Stream Gage to compute the Stage associated with the flow at the stream gage by looking up the flow on a table that relates flow to stage. In addition, a dispatch method was added to trigger this solution.
For more information, see Stream Gage Stage in Objects and Methods.
Earliest Dispatch Timestep
Certain objects like the Reach, Confluence, and Control Point determine the first allowable timestep at which they can dispatch by searching upstream to find the earliest input value. Previously, if the search encountered a Stream Gage, it would stop the search. Now the search continues upstream through the gage. As a result, some downstream objects may be able to dispatch earlier if there is a gage upstream and there are inputs on or upstream of the gage. In some models this can lead to errors if the user has input values on the gage or other objects to solve at these pre-simulation timesteps. Often clearing the inputs is all that is required. The values will propagate from upstream.
Power Reservoirs
Power Method: Plant Efficiency Curve modifications
In the Plant Efficiency Curve power method, the Plant Power Table data was previously required to be concave. This check was removed for the beginning of Simulation and Rulebased Simulation but is still performed at the beginning of an Optimization run.
Tailwater Method: new Coefficients Table method
A new Tailwater method was added: Coefficients Table. This method models the tailwater using a series of coefficients that are applied to the Outflow, Tailwater Base Value, and Tailwater Elevation at the current and/or previous timestep. For more information, see Coefficients Table in Objects and Methods.
Water User - Soil Moisture Methods
A new slot Soil Moisture Gain Loss was added to track the soil moisture water lost when the irrigated acreage is reduced from the previous timestep. In the Irrigation Request with Soil Moisture, the method calculates the volume lost by the reduced area. This volume is then included in the water balance when the water user solves for the current Soil Moisture.
Revised: 08/02/2021