Sediment Fluxes

Benthic flux settings are made in the Sediment Fluxes tab is shown in Figure 1. The nutrient benthic flux computational options are set using the Modify Parameters button in the Benthic Flux frame.

Figure 1.  Water Quality Tab: Benthic.

Clicking the button displays the form shown in Figure 2. The top frame, Benthic Nutrient Flux Method is the option that controls EFDC's benthic flux approach. If the nutrient mass fluxes are to be specified either as constants or variable in time and space, then the diagenesis tabs are not used and consequently disabled. If the Full Diagenesis Model (DiToro & Fitzpatrick, 1993) option is selected then the three diagenesis tabs are visible to allow the user to specify the diagenesis parameters.

Figure 2.  Sediment nutrient flux – Sediment Diagenesis Options and Parameters.

Figure 3 shows one of the diagenesis tabs for defining the diagenesis parameters. The best way to initialize all of the diagenesis parameters is to use the Load Settings button. This will read an existing WQSD3D.INP file from another project and initialize the settings for the current project with those from the loaded project. After the user initializes the parameters, they can modify the settings during the model development stages. The diagenesis values from the Chesapeake Bay ICM application (Cerco & Cole, 1995) provide a good starting point for diagenesis model parameterization.

Figure 3.  Sediment Diagenesis: Diagenesis – Options.

In addition to the diagenesis kinetic parameters, the sediment bed diagenesis initial concentrations also need to be specified. This can be accomplished by applying measured data for each parameter using the Spatially Varying IC's button. When pressed, the form shown in Figure 4 is displayed. Each parameter reaction class, i.e. G1 (most reactive), G2, and G3 (least reactive or inert) can be separately specified or specified at once by selecting options in A Class Options frame. The Value to Set frame allows the user to select the assignment method by using a Constant value, interpolating From Scatter (XYZ) Data or From Profile Data. The data can be interpolated for the entire model in a single operation or using only selected cells by selecting in Grid Options frame.

Figure 4.  Sediment Diagenesis: setting the initial conditions.

Figure 5 shows the Diagenesis-Rates parameter. In the Spatially Constant General Conditions frame, the user can set general parameters for all G classes. 

Figure 5.  Sediment Diagenesis: Diagenesis Rates setting.

Clicking on Nutrient Decay Rates for each Gi Class button displays the form shown in Figure 6 which allows users to modify decay rates for each Gi class. 

Figure 6.  Nutrient Decay Rates for each Gi Class setting.

The diagenesis kinetic parameters can be divided into zones using the Diagenesis-Zones tab. Figure 7 shows how the users access the options to set the zones and assign the zone-specific parameters. The maximum number of zones needed is set by entering the appropriate number in the # of Zones field. To edit a specific zone, the user should scroll to the desired zone using the up/down arrow control.

Figure 7.  Sediment Diagenesis: Diagenesis kinetic zones.