Building a 2D Lake Water Quality Model (Level 2 Step-by-Step Guidance)
1. Introduction
Lake Thonotosassa is the largest natural freshwater lake in Hillsborough County covering an area of 849 acres (3.44 km2) (Hillsborough County Water Atlas). The lake is fed by Baker Creek at the southeastern end of the lake and water flows out through Flint Creek on the northeastern end to the Hillsborough River (Figure 1). This guidance document carries on from the hydrodynamic model introduced in Build a 2D Lake Model (Level 1 Step-by-Step Guidance). The model files are contained in the Demonstration Models of the Resources page folder file (1.14 Lake T Hydrodynamic and WQ Model).
2. Description of Hydrodynamic Model
The hydrodynamic model is used as the basis for building a water quality model that is part of this guidance document. Figure 2 provides a representation of the digital terrain model for Lake Thonotosassa. All of the boundary types for the Lake Thonotosassa model are flow boundaries, the locations of flow boundary conditions are presented in Figure 3. Flow discharge and temperature used for the model are shown in Figure 4. Figure 5 shows a wind rose of the wind data.
3. Setting Water Quality Model
Open the hydrodynamic model then add wind data in the model as shown in Figure 6.
From Model Control form, select External Forcing Data menu item, RMC on Wind sub-option and select Add a Data Series to add wind data series.
Boundary Data Series form is displayed to edit wind boundary.
Figure 6. Add new wind data series.
Enter the Number of Series into the # box for adding multiple times series, or click on Add New button to add series one by one. There is one winds boundary so it should be “1” in this case.
Update the Series Name for associated time series. In this case, the title “Winds” for current series 1.
Copy and paste time series data, “Winds.dat,” into the workspace corresponding to the winds as shown in Figure 7 then click the OK button.
Figure 7. Wind Boundary Data Series form.
From the Model Control form, RMC on Modules the tree menu and check Temperature and Water Quality modules then click OK to activate these modules as shown in Figure 8.
Figure 8. Activate Temperature and Water Quality (1).
After activating Temperature and Water Quality modules, these modules will appear on the left side of the Model Control form, under Modules tree for setting as shown in Figure 9.
Figure 9. Activate Temperature and Water Quality (2).
3.1 Create the Temperature Boundary Time Series; the Atmospheric Boundary Time Series and set IC for Temperature
1. From Model Control form, RMC on Temperature sub-item, under Modules. Here the user can select (1) Setting to go to Temperature Parameters form to set temperature parameters, (2) Initial Condition to assign temperature IC (Figure 10).
Figure 10. Temperature module setting options.
2. From Model Control form, RMC on Temperature under Modules, select Settings to open Temperature Parameters form as shown in Figure 11.
Figure 11. Temperature Parameters form.
2.1. In the Surface Heat Exchange frame, the drop-down list provides several options, including No Atmospheric Linkage, Full Heat Balance, COARE 3.6, Equilibrium temperature (CE-QUAL-W2 method), and External Equilibrium Temperature. Set parameters as shown in Figure 12.
2.2. In the Bed Heat Exchange frame, set Heat Transfer Coefficient value to 7.179E-08, Convective Heat Transfer Coefficient value to 0, as shown in Figure 13.
The settings for Solar Radiation and Evaporation are shown in Figure 13(a) and Figure 13(b).
2.3. Move to the Initial Conditions tab (shown in Figure 14), set parameters for Bed Temperatures Initial Conditions, then click Assign button in the Initial Conditions for Water Temperature frame to open Apply Cell Properties via Polygons: Temp form to assign temperature IC. Select Use Constant from the Set Initial Conditions and set Operator = 10.5. In the Layer Options frame select Set for All the layers to assign the same value to all layers or select For A Specific Layer to set for each layer, then click on Apply button to assign temperature IC and OK to close the form and return it to the parent form (Figure 15).
Figure 14. Temperature Parameters - Initial Conditions setting.
Figure 15. Assign Temperature IC.
2.4. Move to the Boundary Conditions tab. Here the user can create the number of atmospheric and temperature data series as shown in Figure 16.
Figure 16. Temperature Parameters - Boundary Conditions setting.
In the Atmospheric Data frame, click on the Edit button then the Boundary Data Series form appears to assign atmospheric data series (Figure 17). Click Add New button to add a new time series then put a name as "Atmospheric" for the Series Name then press Enter key as shown in Figure 17.
Figure 17. Boundary Condition Settings: Temperature Data Series (1).
Copy and paste time series from “Atmospheric.dat” file from the Data folder, then click OK (Figure 18)
Figure 18. Boundary Condition Settings: Atmospheric Data Series (2).
In the Temperature Data frame (Figure 16), click on Edit button then the Boundary Data Series form appears to assign Temperature data series (Figure 19). Click Add New button to add a new time series then put a name as "Temp Inflow" for the Series Name then press Enter key as shown in Figure 19.
Copy and paste time series from “Temperature.dat” file from the Data folder, then click OK (Figure 20)
Figure 19. Boundary Condition Settings: Temperature Data Series (1).
Figure 20. Boundary Condition Settings: Temperature Data Series (2).
3.2 Create the Water Quality Time Series and set Initial Conditions for Water Quality
From the Model Control form, RMC on Water Quality sub-menu under Modules, select Setting to open Water Quality form as shown in Figure 21.
Figure 21. Open Water Quality Settings form.
3.2.1 Water Quality – Kinetics
1. Proceed to the Kinetics tab, select Module 1 (Standard) from the Global Kinetic Options frame dropdown, then click on Params button to display the list of simulated parameters; type 1 for simulated parameter and 0 for not simulated, then click OK as shown in Figure 22.
Figure 22. Kinetics Computation Options.
2. Click the Modify Parameter button in Water Column Kinetics frame for Use Zones for Kinetics to edit Kinetic Parameters for the current zone as shown in Figure 23.
Figure 23. Kinetics Parameters by zone.
3. Click the Fecal Coliform Decay button in the frame Water Column Kinetics to edit Parameter for the current zone as shown in Figure 24.
Figure 24. Fecal Coliform Parameters.
4. Click the Light Extinction button in the frame Water Column Kinetics to edit light extinction options as shown in Figure 25.
Figure 25. Light Extinction Options.
3.2.2 Water Quality – Nutrients
Proceed to the Nutrients tab as shown in Figure 26.
In the Nutrient Options & Parameters frame: (1) click Temperature Effects button to edit temperature effects as shown in Figure 27; (2) click Carbon button to edit the Carbon parameters as shown in Figure 28; (3) Nitrogen button to edit the Nitrogen parameters as shown in Figure 29; (4) Phosphorus button to edit the Phosphorus parameters as shown in Figure 30; (5) COD&DO button to edit the COD&DO parameters as shown in Figure 31.
In the Sorption Options frame: Select Total Active Metal (TAM) Based option and (6) click Modify Parameters buttons to edit Nutrient Sorption Parameters as shown in Figure 32.
Figure 26. Water Quality Tab: Nutrients.
Figure 27. Nutrients: (1) Temperature Effects.
Figure 28. Nutrients: (2) Carbon Parameters.
Figure 29. Nutrients: (3) Nitrogen Parameters.
Figure 30. Nutrients: (4) Phosphorus Parameters.
Figure 31. Nutrients: (5) COD and DO Parameters
Figure 32. Nutrients: (6) Nutrient Sorption Parameters.
3.2.3 Water Quality – Biota
To configure the algae to the model, proceed to the Biota tab which is shown in Figure 33. By default, there are four algal groups, in this model only one algal group (green algae) is simulated (Figure 22).
In Algae and Macrophyte Options frame: click Modify button, the form of Algae and Macrophyte Options will be appeared as shown in Figure 34. Select Green Algae for Select Biota. Settings for the current green algae through General, Growth, Basal Metabolism, Predation tabs as shown from Figure 34 to Figure 37.
In the Solar Radiation Option for Photosynthesis frame (Figure 33), select source drop-down and select Constant, then click Modify button to edit solar radiation parameters as shown in Figure 38.
Figure 36. Green Algae: Basal Metabolism.
Figure 37. Green Algae: Predation.
3.2.4 Water Quality – Initial Conditions
Proceed to the Initial Conditions tab as shown in Figure 40. In Initial Conditions frame, click on the drop-down menu and select Spatially Constant, then edit each of the water quality parameters shown in Figure 40 and Figure 41.
Figure 40. Water Quality Tab: Initial Conditions.
Figure 41. WQ Initial Conditions Parameters.
3.2.5 Water Quality – Boundary Conditions
1. Proceed to the Boundary Conditions tab as shown in Figure 42; Click the Edit button in the Time series Data frame to open Boundary Data Series form which is shown in Figure 43.
Figure 42. Water Quality Tab: Boundary Conditions.
2. Set the number of series to 1 in # box or click on Add New button to add a data series. Set the Series Name to "WQ Data" and type or copy and paste into the form for the time and cyanobacteria data as shown in Figure 43.
3. Click on Select Class drop-down menu to select other parameters. Copy and paste into the form for the time and water quality parameter data. An example of the diatom algae parameter is shown in Figure 44.
Figure 44. Boundary Condition Settings: Diatom algae Data Series.
5. Repeat this process for the others parameters in the list below:
3) Green algae | Figure 45 | 13) Dissolved organic nitrogen | Figure 55 |
4) Refractory particulate organic carbon | Figure 46 | 14) Ammonia nitrogen | Figure 56 |
5) Labile particulate organic carbon | Figure 47 | 15) Nitrate nitrogen | Figure 57 |
6) Dissolved carbon | Figure 48 | 16) Particulate biogenic silica | Figure 58 |
7) Refractory part. organic phosphorus | Figure 49 | 17) Dissolved available silica | Figure 59 |
8) Labile particulate organic phosphorus | Figure 50 | 18) Chemical oxygen demand | Figure 60 |
9) Dissolved organic phosphorus | Figure 51 | 19) Dissolved oxygen | Figure 61 |
10) Total phosphate | Figure 52 | 20) Total active metal | Figure 62 |
11) Refractory part. Org. nitrogen | Figure 53 | 21) Fecal coliform bacteria | Figure 63 |
12) Labile part. organic nitrogen | Figure 54 |
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Figure 45. Boundary Condition Settings: green algae.
Figure 46. Boundary Condition Settings: Refractory particulate organic carbon.
Figure 47. Boundary Condition Settings: Labile particulate organic carbon.
Figure 48. Boundary Condition Settings: DOC.
Figure 49. Boundary Condition Settings: Refractory particulate organic phosphorus.
Figure 50. Boundary Condition Settings: Labile particulate organic phosphorus.
Figure 51. Boundary Condition Settings: Dissolved organic phosphorus.
Figure 52. Boundary Condition Settings: Total phosphate.
Figure 53. Boundary Condition Settings: Refractory particulate organic nitrogen.
Figure 54. Boundary Condition Settings: Labile particulate organic nitrogen.
Figure 55. Boundary Condition Settings: Dissolved organic nitrogen.
Figure 56. Boundary Condition Settings: Ammonia nitrogen.
Figure 57. Boundary Condition Settings: Nitrate nitrogen.
Figure 58. Boundary Condition Settings: Particulate biogenic silica.
Figure 59. Boundary Condition Settings: Dissolved available silica.
Figure 60. Boundary Condition Settings: Chemical oxygen demand.
Figure 61. Boundary Condition Settings: Dissolved oxygen.
Figure 62. Boundary Condition Settings: Total active metal.
Figure 63. Boundary Condition Settings: Fecal coliform bacteria.
6. Click the OK button when you have finished setting all 21 parameters
3.2.6 Water Quality – Benthic
1. Proceed to the Sediment Fluxes tab shown in Figure 64.
2. Select Modify Parameters button will now displayed under Sediment Fluxes as shown in Figure 65.
Figure 64. Water Quality Tab: Sediment Fluxes.
3. From the Sediment Diagenesis Option & Parameters form (Figure 65), in the top frame, Benthic Nutrient Flux Method select Spatially & Temporally Constant; enter the values of parameters in the Constant Benthic Flux Rates frame as shown in Figure 65.
Figure 65. Set Benthic Flux Rates.
4. Click the OK button when finished setting to return to the main form.