Wflow Instructable Ethiopia Case

Introduction: Wflow Instructable Ethiopia Case

Ethiopia is a country in Africa. Ethiopia frequently suffers from drought periods. The drought periods occur from May till the end of November. Due to these drought periods, the ground and the river dry out. Whenever this occurs the water scarcity rises. Besides drought Ethiopia, like any other country in the world, has it's raining periods. These occur between December to April with often spikes from June to September.

In Ethiopia, the Awash river is one of the main water resources. Due to the climate, the river changes its path regularly. With climate change, drought will occur more often and there will be more precipitation. In this instructable, a water system analysis will be shown in steps. This will be done by following a specific program called Wflow. The following steps will be taken: a sensitivity analysis on the Wflow.

Made by:

  • Boaz Elias-Pour 0922267
  • Rick van Bragt 0998412
  • Troy Vlieger 0997410
  • Djurre Schouten 0925603
  • Michiel Kappetein 0869913

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Step 1: Getting Started

To create a realistic hydraulic model. The following programs are needed.

  1. Qgis (Download link Qgis)
    Qgis is an open-source geographical information system. Necessary for interpreting and visualizing collected data.
  2. Notepad++(Download link Notepad++ latest release)
    Notepad++ is a textediter used to set parameters for Wflow.
  3. Wflow (Download link Wflow)
    Wflow is an open-source phyton based program used for hydraulic modeling.

It is highly recommended to install all programs on the C drive. Creating a proper folder structure will also benefit during the project.

For Wflow a separate folder has to be created in which the Wflow.zip file has to be extracted. After unzipping, the folder should contain the following files and folders:

  • Wflow-2019.1\
  • Wflow_Melkakuntire\
  • run-hydrology.bat

The map structure in the Melkakuntire folder should be as the picture above

Qgis plugins recommended:

  • QuickmapServices;
  • CrayFish plugin.

Step 2: Exploring Wflow

In this step, we will start exploring the delivered data in Qgis. The data is delivered in the staticmaps folder and the dynamic inmaps folder

Staticmaps

Go to the staticmaps folder and explore the content in Qgis by adding them to your map (use the WGS84 coordinate system). In this folder, you can find data as:

  • River;
  • Catchment area;
  • Flow direction.

You can change the look of the data using the symbology function in the properties tab, change the look of your map to your liking.

Needed maps:

Make sure you add the following maps to your mapview:

  • wflow_river.map;
  • wflow_streamorder.map;
  • wflow_subcatch.map.

Dynamic Inmaps

Go to the Dynamic_inmaps folder, in this folder you can see data on the following subjects:

  • Temperature;
  • Precipitation;
  • Potential Evapotranspiration.

Dynamic gridded data can be processed by Qgis as Mesh layers. Select Layer/Data Source Manager in the Menu and open the Mesh tab. Click on "Add" and open the forcing -1990-2018.nc file in the Wflow_Melkakuntire/inmaps folder.

The rasterfile has been added to Qgis, but only shows as a regular grid. To display the results a new styling tab appeared on the right of the screen with four different tabs:

  • General, use this tab to select the wanted variable, in this case, the P (precipitation in mm);
  • Contours symbology, use this tab to change the symbology of the map, set maximum discharge to 0,1 an apply the changes;
  • Vectors symbology, this tab is not yet needed;
  • Rendering, use this tab to deselect the Native Mesh Grid.

Use the general tab to slide to different timesteps. You can use the CrayFish plugin to plot the results in a chart.

At the end of this step, your screen should look something like the screen above.

Step 3: Running Wflow

Setting boundaries

Now you've collected and checked all the data it is time to process it. Before you start doing this, it is important to set your time boundaries. To do this you open the following folderWflow_Melkakuntire\ in this folder you edit the wlfow_sbm file with your Notepad++ application. If you edit this file it should look like the first screen above.

To edit the time boundaries you go to the run tab (blue). In this tab, you can see the "starttime" and "endtime". To edit this simply change the date and/or time after the text, do this for both and make sure they don't conflict. You must select a time and date on which you also have measured data.

Running Wflow

First, open the wflow folder and run-hydrology-parameters-changes file and open this file with notepad ++. There are several parameters you can edit:

  • C: is your location on your c:drive
  • R: is the to be run parameter
  • c: is the name of the batchfile

Now you have completed all your settings it is time to run the model. To do this go to the Wflow\ folder. In this folder, you find the run-hydrology-MelkaKuntire batchfile. Double click on this file and press enter to make it run. It should look like the second screen above while running.

Step 4: Interpreting Results

Now you've run your first Wflow model, in this step, we will start by examining and interpreting the data in both Qgis and excel

Opening data in Qgis

After the model has successfully run, the grid output is written in the wfow_outputs.nc file. This file can be processed just like the Mesh layer done in the steps before. To open the outputs of wflow, in QGIS, select Layer \ Data Source Manager. Go to the Mesh tab and open the wflow_outputs.nc file in wflow_Moselle/SBM folder. Click on Add and select WGS 84 EPSG 4326 as the coordinates system. Close the Data Source Manager when the file is loaded.

Wflow_outputs has been added but only show a regular grid. To display your results, select View/Panels/Layerstyling. The following tabs appear on your screen:

  • General, use this tab to select the wanted variable, you can choose between runL (overland run in m3/s) or runR (river discharge in m3/s)
  • Contours symbology, use this tab to change the symbology of the map, set the tab to your liking.
  • Vectors symbology, this tab is not yet needed;
  • Rendering, use this tab to deselect the Native Mesh Grid.

In this case, the crayfish plugin can also be used to plot the data as a graph. Your screen should look like the first picture above.

Opening data in Excel

To see the data in excel go the Wflow_Melkakuntire\SBM folder and open the Run.csv file in Excel. This is a text-based file that needs to be readable. To do this select column A and go to the Data tab above. Select Text to Columns, the screen above opens. Press Next and deselect Tab and select Comma and press Next. Click on Advanced and us "." as decimal separator and use "," as thousands separator press Ok and then Finish. The result is an Excel sheet which you can use to make graphs and sheets of your run.

The first Column shows the timesteps and the other columns show the different GRDC stations.

Step 5: Locating Your Station

The next step in your project is finding your station on which you collected data so you can compare reality to your model. To do this follow these steps:

Converting Excel to shapefile

Go to the Awash_data.zip and find the grdc_stations_Awash.xlsx file, add this file to your map in Qgis. The points should appear like the first picture above. Go to the wflow_melkakuntire_staticmaps folder and add the wflow_gauges.map file to your map in Qgis. Use the object identifier in the toolbar and select the point at the outflow of your discharge area. In the tab on the right, you can now read its name, for example, MELKA KUNTIRE.

Then select the nearest raster point to the MELKA KUNTIRE point to read the number it has. If right this number should correspondent with one of the tabs in your output excel file.

Step 6: Calibrating Your Model

Now you have your results visible, it is important to compare them to the measured data. Probably there will be a difference in timing and/or the intensity of the flow as in the picture above. In this step, we will discuss how to overcome this difference in results.

Changing parameters

To adjust your model there are several parameters you can define, in the following list are the parameters we used to our model:

  • Soilthickness: Maximum depth of the soil (m)
  • KsatVer: Saturated conductivity (mm/d)
  • KsatHorFrac: Saturated conductivity horizontal (mm/d)
  • RootingDepth: Depth of the roots (mm)
  • N_River: Manning's N parameter for cells marked as river

To change these parameters edit the run-hydrology-parameters-changes.bat file with Notepad ++. The following code appears on your screen:

wflow-2019.1\wflow_sbm.exe -C wflow_Melkakuntire -R SBM_SoilThickness_1 -c wflow_sbm.ini -P "self.SoilThickness = self.SoilThickness * 1.0"

Now you need to specify and edit the parameters to fit them to your project. Do this by changing the values behind the text. Keep running the model with different parameters until you have a model that is representative of the reality. Keep in mind that the parameters you edit should be realistic.

Good luck

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