When to Read Flags |
When to Read Flags |
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This pane is a subpane of the FMP: Farm Process pane on the MODFLOW Packages and Programs dialog box.
The four flags listed here determine how some of the input required by the Farm Process is specified. (There are two other "When to Read Flags" (IFTEFL and IEFFL) that you do not need to specify because ModelMuse can infer the correct values for these variables.)
The rooting depth is the distance from the soil surface to lowest level in the soil from which the crops can extract water. You can either specify the rooting depth for each crop as a function of time or you can have the Farm Process calculate the rooting depth from climate data.
The FMP process has several ways of determining the consumptive use of water for various crops.
•Calculated (3): The Farm Process can calculate the volumetric based on climate data, the properties of each soil, and the cell areas.
•Potential ET (2): The Crop Consumptive Use Flux (CU) is specified for each crop and is multiplied by the area of each cell to determine the volumetric flux rate. Fallow areas (CropID = -1) are not allowed with this option.
•Potential and reference ET (1): For crops, the Crop Consumptive Use Flux (CU) is specified for each crop and is multiplied by the area of each cell to determine the volumetric flux rate. For fallow areas (CropID = -1), the Reference Evapotranspiration is multiplied by the area of each cell to determine the volumetric flux rate.
•Crop coefficient (-1): For crops, the Crop coefficients is specified for each crop and is multiplied by the Reference Evapotranspiration and the area of each cell to determine the volumetric flux rate. For fallow areas (CropID = -1), the Reference Evapotranspiration is multiplied by the area of each cell to determine the volumetric flux rate.
The precipitation rate can be determined in either of two ways.
•Spatially disptributed (2): The modeler can specify precipitation rates for each cell that can vary with time.
•Climate time series (3): Precipitation data can be included in climate data. The average rate within each time step will be used.
Some of the precipitation and irrigation applied to a field may not be used by the crops but will instead end up in the surface water. The fraction that is lost to surface water can be determined by FMP in either of two ways.
•Calculated (0): The fraction is calculated based on the slope of the ground surface
•Specified (1 or 2): The modeler specifies the fraction lost for each crop.