1. Introduction

This tutorial  will guide the user in how to setup a 2D lake hydrodynamic model and run a solution for EFDC. It will cover preparation of the necessary input files for the EFDC model and visualization of the output by using the EFDC_Explorer (EE) Software.

The data used for this tutorial are from Hillsborough Water Atlas, Lake Thonotasassa, Florida, USA. All files for this tutorial are contained in the Demonstration Models of the Resources page folder file (DM-14 Lake T Hydrodynamic and WQ Model).  

Before beginning the first session, let us first introduce the main form of the EE GUI in order to better understand our explanations in this document. Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 1 is the main form of EFDC_Explorer or EE User Interface.

Figure 1. EFDC_Explorer main form.

2. Create a New Grid

This session will guide you to create a new simple grid with EFDC_Explorer. If the user requires a more complicated grid it is recommended to use other grid generation software such as CVLGrid.

Lake Thonotosassa is located in Hillsborough County, Florida, USA and has been chosen as an the example for where to build a 2D model in EE

The gird generation process includes following steps:

1. Open EE

2. Click Generate New Model icon:  on the main menu of the EE interface. The Generate EFDC Model frame appears shown in Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 2.

3. In Grid Type of Generate EFDC Model, the user should select Cartesian; in Grid/Element Generation Options, select Uniform Grid. The user must fill the coordinates of Lower Left, Upper Right and Delta (dimension of grid cells) as outlined below.

4. In order to obtain the coordinates of the two points Lower Left and Upper Right, the user can use Google Earth or some other GIS software. The requirement for this task is that the rectangular area defined by the two points on the map should cover the outline of the Lake Thonotosassa (see Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 3).

Figure 2. Generate EFDC Model form.

Figure 3. Identifying Lower Left and Upper Right coordinates.

5. Table 1 the shows coordinates of Lower Left and Upper Right obtained from Google Earth.

3.2 Assigning the Depth/Water Surface Elevations

This step assigns the initial depth or water surface elevations. There are two options for setting the surface water elevation, namely, Use Constant and Use Point Measurements/Gridded Data.

1. Click Assign button, select Use Constant: to assign a constant water surface elevation of 11.5 m in the Operator or Constant box. (Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 11). (Note that if the user selected Use Point Measurements/Gridded Data then the water surface will be assigned as equal to bottom elevation plus 11.5 m at every point. A further option is for the user to assign the water depth by check box of Assign Depths Instead of Water Surface Elevations).

Figure 11. Assigning water surface elevation (use constant option).

2. After selecting this option for assigning water surface elevation, click Apply button then click Done button to finish.

4. Boundary Conditions

This section will teach you how to prepare the boundary conditions and assign them to the model cell configuration. In this Lake 2D case there are two flow boundaries; one is runoff inflow to the lake and the other is outflow through a gate. Thus, we should prepare two time series of inflow and outflow boundaries. In other cases, the number of time series for boundary conditions might be many more such as those for hydraulic structures, pressure boundaries, or include time series for temperature, salinity and water quality boundaries also.

4.1 Set Time Series

To set the boundary time series take the following steps:

1. Select the Domain | Boundary Conditions. (Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 12)

2. Click the Edit (E) button  for Flow to edit the flow boundary. (Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 12)

Figure 12. Assigning boundary conditions.

3. Enter the Number of Series into the box. There are two flow boundaries as mentioned so it should be “2”.

4. Give a Title for associated time series. In this case, title “outflow” for Current Series 1, and “inflow” for Current Series 2.

5. Copy and Paste time series data, “Lake2D Inflows.dat,” into the workspace corresponding to the inflow series. Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 13 shows time series of inflow.

Figure 13. Data series: inflow.

6. Click to the Current button to view the current time series (for a case where there are multiple layers check Sum Layers to show total flow).

Figure 14. Time series plot of inflow.

7. Select the up/down arrow buttons to edit the other time series.

8. In this model we will keep inflow and outflow identical. We copy and paste the same time series data, “Lake2D Inflows.dat,” into the workspace corresponding to "Outflow". We then apply an operator to the outflow by entering “* -1” in the the operator box. This will make the values negative as shown in Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 15.

Figure 15. Data series: outflow.

9. Click OK to finish editing the boundary time series.

After completing the above steps, the user has prepared all the required boundary time series. Now we will assign these boundary time series to the model cells. Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 16 shows the location of inflow and outflow for this lake case. Thus, we have to assign these cells with associated time series for in/outflow prepared in previous session.

Figure 16. Locations of Inflow and Outflow for the Lake.

4.2 Assigning a Boundary Condition

In order to assign the boundary, the following steps should be taken;

1. Click the ViewPlan icon  on the main form of EE (Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 1).

2. Choose Boundary C’s in the Viewing Opt’s .

3. Enable Edit grid by checking to  (see Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 17)

4. Right mouse-click on the inflow location cell and select New (Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 18)

Figure 17. Assigning boundary condition cells.

Figure 18. Right mouse-click on the inflow cell.

5. Enter the Boundary Group ID by typing “Inflow” (Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 19)

6. Select boundary types. This depends on your current boundary type as to what selection is made. In this case, we have flow boundary so we choose number 1 (Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 20).

7. Select the flow series associated with this inflow boundary time series from the dropdown list. Make sure that the Factor is set to “1”. Then click OK to complete.

8. Apply same process for assigning the outflow boundary cell. Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 22 shows the boundary conditions after assigning the inflow and outflow boundaries.

Figure 19. Enter Boundary Group ID.

Figure 20. Select the Boundary Types.

Figure 21. Assign the corresponding time series.

Figure 22. Inflow and Outflow boundaries assigned.

5. Model Timing

After completing the previous sections, the user has almost completed the hydrodynamic model of a lake. This section will guide the user how to setup the model simulation time and model time steps.

1. Select Timing/ Linkage tab and Model Run Timing (Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 23)

2. Enter duration of start/ end of the simulation. Note that the boundaries time series should always cover this simulation duration period, otherwise the model will not run.

Figure 23. Model Run Time.

Table 2. Model Run Timing.

3. Select the EFDC_Explorer Linkage tab and set Link EFDC Results to EFDC_Explorer and set Linkage Output Frequency to 60 minutes. This means that EFDC will record the output every 60 minutes for display of the model results in the EE. (Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 24). Note that a smaller output frequency will create a larger output file.

Figure 24. Setting linkage output frequency.

6. Setting Wetting and Drying

In order to optimize simulation time it is recommended to apply the EFDC model’s wet and dry condition function. This means that dry cells are ignored in each hydrodyanmic calculation, though volume of water is kept to maintain mass balance. For this condition we should make the following settings:

1. Select Hydrodynamics / Wetting & Drying box

2. Set Flag equal to -99 to allow cell skipping.

3. Enter the Dry Depth and the Wet Depth. Note that the wet depth should always greater than the dry depth. (Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 25). The hydrodynamic model is ready for running now. If the model simulation results are not satisfied then we may have to select Turbulence Options | Modify button to adjust the hydraulic parameters.

Figure 25. Hydrodynamic model setup.

4. Return to select Domain | Grid tab and enter the number of vertical layers required into the box. In this case we will set the vertical layers equal to 5 (Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 26).

5. Save the project.

Figure 26. Setting the vertical layers.

7. Running EFDC

This section runs the EFDC model and includes following steps:

1 Select the Setting icon  on the main EE form to browse to the EFDC Executable file. (Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 27). By default this file is in the installation folder C:\Program Files (x86)\DSI\EFDC_ExplorerXX

Figure 27. Browse to the EFDC executable file

Select the Run EFDC icon  on the main form and click the Run EFDC_DSI button to run the model (Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 28).

Figure 28. Run EFDC Options.

If all settings are correct, the model will start running and you will see the MS-DOS Window appear showing the model results as shown in Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 29

Figure 29. EFDC run window.

8. Visualizing the EFDC Model Output

This session will teach you how to view the model simulation results. In general, selecting these three icons  on EE’s main form (Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 1) to view the model simulation results in ViewPlan, ViewProfile or View3D, respectively.

1. Select the ViewPlan icon as .

2. Scroll drown the Viewing Opt’s to choose the parameters for which you want to view the model results. Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 30 is an example of showing the vector and magnitude velocity field results. Similarly, you can select other parameters to show the results.

3. Right mouse-click to the legend scale to open the ViewPlan Display Options (Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 31)

Figure 30. Visualizing the EFDC solutions.

Figure 31. ViewPlan Display Options.

There are a few main features in this form that are frequently used when analyzing model results. The detailed explanations for each icon are described in the Table 3.

Table 3. Description of Main Features in the Toolbar.

Please refer to the EE Knowledge Base for more information on EE capabilities.