If you selected a time series variable — Model, External, or State Variable — as your independent variable, a second independent variable, Date, can be selected to describe your release function. For example, if your release limit varies as a function of pool elevation but the lookup table has a column for growing season and non-growing season, then your first independent variable is the model variable Elevation and the second independent variable is date (or season).

To add Date as a second independent variable of your release function:

  • Click the Seasonal Variation button located at the bottom of the list of modifiers to the right of the release function table.

  • The Seasonal Variation editor will open ("Figure: Seasonal Variation Editor").

    Figure: Seasonal Variation Editor


    • Dates—Use the Seasonal Variation editor to define the seasons or date values to be entered into your release function table. The seasons or dates that you enter here define the columns of your function table ("Figure: Release Function table for a Seasonally-Varying Function of Inflow Relationship").

      Figure: Release Function table for a Seasonally-Varying Function of Inflow Relationship


    • Interpolation Type — this interpolation type selection applies to the columns of the release function table. The interpolation type on the main edit panel applies to the rows of the table (between the values list for the first independent variable.) Your options are: Linear, Cubic, or Step.

  • When you have finished entering the dates that represent the start of each season, click OK. The Seasonal Variation editor will close, the Seasonal Variation checkbox will be checked , and the function table will have a column for each season start date you specified ("Figure: Release Function table for a Seasonally-Varying Function of Inflow Relationship").