The General tab in the Temperature Parameters form allows the user to configure the Ice Computation Options, Bed Heat Exchange Coefficient, and Evaporation Options as shown in Figure 1 244023409. These options are each described in detail below. Note that by default the Display Options in EE are the water depth and water surface elevation include the ice thickness. This can be manually changed by the user in this option.
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Figure 1. Temperature Parameters: General.
Ice Computation Options
A robust ice sub-model is available in EEMS. Older versions of EFDC had relatively limited ice modeling ability. Ice formation and melt is currently simulated by EFDC using a coupled heat model and fully handled by EFDC_Explorer.
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Ice options are now available under the Ice Computational Options frame shown in Figure 2. For all these options, ice is only enabled if the user is simulating temperature.
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Figure 2. Temperature Parameters: Ice Computation Options.
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Currently the ice sub-model in EFDC+is only an ice cover model and not an ice and snow cover model. The snow cover would account for snow on top of the ice and is expected to be added for an upcoming release. The ice cover model allows light to be attenuated through the ice. The solar radiation absorption is accounted for in this process. To implement this in EFDC, routines such as CALQVS and CALHEAT were modified. CALPUV was also updated so that the bed heat is handled when the elevation is below the bottom of the cell.
Figure 5244023409 shows the default values of the ice parameters that are required to simulate ice in EFDC+ model. A checkbox is provided for the Use Ryan Harleman Wind Function option if desired.
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Output from the ice sub model can be displayed in a number of ways in EE. A 2D plan view of the ice thickness or temperature may be viewed by selecting 2DH View and then add layer Thermal/Ice | Ice Thickness. Figure 7244023409 shows an example of frazil ice formation in a river in Alberta, Canada. Note that initially ice forms on the river banks where depths are shallower and flow is lower.
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The user can also visualize ice on the water column in the 2DV View tool. This displays as a solid grey color as shown in Figure 8. The vertical exaggeration of the ice layer can be modified by RMC on Ice Thickness | Properties and change Thickness Factor to show it more clearly as shown in Figure 9244023409.
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Figure 8. Ice Sub model: 2DV View ice cover and WC temperature.
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Figure 9. Ice Sub model: 2DV View Properties.
Evaporation Options
The Evaporation Options (Water Balance Only) frame is only displayed if the appropriate surface heat exchange sub-model has been shown in the Surface Heat Exchange tab. Evaporation Options will only appear for the following surface heat exchange options:
- Full Heal Balance (Legacy)
- Full Heat Balance with Variable Extinction Coefficient
- Equilibrium Temp (CE-QUAL-W2 Method)
The heading states the evaporation options are for water balance only because for the water balance evaporation is optional. If activated, there are a number of ways to define or compute evaporation. Since EFDC+ is a coupled model, any changes to the water balance is automatically accounted for in all other modules, including the eutrophication module. Note that evaporation is always included in the surface heat exchange processes.