In this tutorial, we will go through the steps required to delimit hydrological basins using GRASS GIS, including setting up the software, importing data, installing plugins, correcting depressions in the digital elevation model, generating the stream network, and calculating morphometric parameters of the basin. By the end of this tutorial, you will have a better understanding of how to use GRASS GIS for hydrological analysis, and how to apply it to your own research or management projects.
- Configuration of GRASS GIS directories
- Create a folder anywhere on the hard drive and save the Digital Terrain Model (DTM) of the working area in it.
- Launch the GRASS GIS software.
- Select the database directory first, then select a new GRASS location and name the file.
- Define the geographic location of the project using the information from the DTM file saved in the folder where it is stored.
- Start the GRASS session.
- DTM Import
Import the DTM to the project and activate it in the layer manager.
3. Installation of GRASS GIS Addons
- To install the necessary addons (r.basin, r.hypso, r.stream.basins, r.stream.distance, r.stream.order, r.stream.snap, r.stream.stats, and r.width.funct), internet connection is required.
- Open the addons manager, type the name of the addon in the upper section of the installation manager (e.g. r.basin), select it, and install it.
- Correction of DTM depressions
Generate a depression-free elevation map and a flow direction map from a specified raster elevation map using the r.fill.dir algorithm. Save the new raster and the flow direction raster.
5. Generation of the Hydrological Network of the DTM
Configure the r.stream.extract algorithm by selecting the depression-free DTM as the input layer, a pixel accumulation value of 25,000 pixels, and raster and vector hydrological networks as well as a new flow direction raster as the output.
- Calculation of Morphometric Parameters of the Hydrographic Basin
- Create a drainage point for the hydrographic basin of study by right-clicking two pixels above the microbasin outflow and copying the coordinates.
- Use the v.in.ascii algorithm to import the coordinates and configure the point properties by changing the color, symbol, and size.
- Run the r.basin algorithm by selecting the DTM, setting the output prefix, entering the coordinates from the drainage point, selecting the output directory, and executing the process. Save the results to a text file.
7. Visualization of the results
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