Build a 2D Lake Model (Level 1 Step-by-Step Guidance)
1 Introduction
This tutorial will guide the user on how to set up a 2D lake hydrodynamic model and run a solution for EFDC. It will cover the preparation of the necessary input files for the EFDC model and the 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_HYD-WQ_Model). Note that the model grid will contain more than 300 grid cells and use the dye module; therefore, a Demo version of EE, which only allows running models with less than 300 horizontal cells and without the dye, salinity, and particle tracking modules, will not be applicable. The user, however, can load and view the model without being able to edit, save edits, run, and view model output with this version.
Before beginning the first session, let's introduce the main form of the EE GUI to help you 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.
2 Create a New Grid
This session will guide you to create a new simple grid with EFDC+ Explorer.
Lake Thonotosassa is located in Hillsborough County, Florida, USA, and has been chosen as an example of where to build a 2D model in EE
The gird generation process includes the following steps:
1. Open EE
2. Click New Model icon: on the main menu of the EE interface. The Cartesian Grid Generator frame appears in Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 2
3. In Grid Options, select Uniform Grid.
4. Click Set button to select projection as UTM Zone 17 in the northern hemisphere, as the lake is located in that zone (Figure 2.1)
4. RMC (Right Mouse Click) on the Bounding Polygons blank to open a pop-up menu. In the pop-up menu, select Add Files to browse the polygon file. The land boundary of the lake will be loaded here.
The polygon file for this model is "Outline.p2d" and can be found in Data/Bathymetry folder of the Demonstration Models provided above.
5. With the polygon file loaded, the X-Y Directions for the corners of the models are automatically defined. The user can also adjust the Cell Size and Number of Cells in Uniform Grid Options.
In this example, enter cell size is 100x100m for the Cell Size (m) then click the calculator symbol for the Number of Cells.
6. If the user adjust any options in Uniform Grid Options they must click the Generate button so that EE can generate the changes.
7. Click on Remove Dry, this will remove all cells outside of the polygon.
8. Click OK button to finish grid generation. An overview of the created grid is shown in the General tab (Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 5).
9. Save the model by selecting the Save button and create a new directory.
3 Assigning the Initial Conditions
This section will guide you on how to assign the initial conditions, such as the bathymetry, water level, and bottom roughness.
3.1 Assigning the Initial Bathymetry
1. Select the Initial Conditions tab and right mouse click (RMC) on the Bathymetry sub-tab. A new Bathymetry form will appear. In that form, click on Assign to define bathymetric value.
2. The area the user wants to assign the bathymetry data to is set by a poly file. In this case, choose All grid cells
3. The data for bathymetry values are assigned by “Bathymetry.dat” file in Bathymetry folder . This bathymetry file is simply an xyz format.
4. Choose Scatter (XYZ) data and then Add file to browse for “Bathymetry.dat”.
5. After adding the data file, click on the Apply Defined Conditions button to make your changes take effect before selecting the OK button.
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 Scatter (XYZ) data.
1. RMC on Water Depth/Elevation button then click Assign Elevation button (Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 10)
2. Select Constant to assign a constant water surface elevation of 11.5 m in the Constant box. (Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 11).
3. After selecting this option for assigning water surface elevation, click Apply Defined Conditions button, then click the OK button to finish.
4 Boundary Conditions
This section will teach you how to prepare and assign the boundary conditions 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 much more, such as those for hydraulic structures, pressure boundaries, or include time series for temperature, salinity, and water quality boundaries.
4.1 Set Time Series
To set the boundary time series, take the following steps:
1. Select the External Forcing Data tab. (Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 12)
2. RMC on Flow button and select Add New Data Series to edit the flow boundary. (Build a 2D Lake Model (Level 1 Step-by-Step Guidance)#Figure 13)
3. Enter the Number of Series into the box. There are two flow boundaries as mentioned so it should be “2”.
4. Give a Series Name for associated time series. In this case, title “Inflow” for Series 1, and “Outflow” for Series 2. (remember to press Enter after each input)
5. To import Inflow time-series data, click on the Import data from file button on the Toolbar.
In the ASCII Data Import form as shown in Figure 4-2.
(1) Browse to the “Inflow.dat” file and select the data format as EE Dat or WQ Data.
(2) Modify the Import Settings parameters as Figure 4-2 shows.
• Header Rows to Skip: 0