Preprocessing the Input Data
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This section describes how to preprocess spatial data in QGIS before using Hydrobricks.

All operations assume you're working in the Swiss coordinate system EPSG:2056 - CH1903+ / LV95.  
Always make sure that the EPSG is 2056.

First step:
    Create a SHP file of the outlet location using the map of Switzerland:

    - Layer ➔ Create Layer ➔ New Shapefile Layer
    - Specify the name (example `TR_intake_EPSG2056`) and save it in the folder `Intakes_locations`
    - Geometry type **Point** and CRS **EPSG:2056**
    - Right-click on the newly created Layer ➔ Toggle Editing ➔ Add point feature
    - Click on the point where there is the outlet/water intake

Second step:
    Cut out the study area from the DEM with 10 m resolution (from swissALTIregio). The study area must cover the entire catchment area.

    - Load the DEM into QGIS: either by dragging it into the project or using **Layer ➔ Add Layer ➔ Add Raster Layer**
    - **Raster ➔ Extraction ➔ Clip Raster by Extent**  in the “Clipping extent” window choose “Draw on Map Canvas”
    - Save the clipped area as `name.tif` (important: use `.tif` extension)

Third step: 
    Fill the sinks of the clipped DEM
    
    - **Processing toolbox ➔ SAGA ➔ Fill Sinks (Wang & Liu)** 
    
    - Input file: Clipped DEM; Output file: Filled DEM

Fourth step: 
    Compute the Strahler order of the stream network and generate a polyline of the stream network
    
    - **Processing toolbox ➔ SAGA ➔ Terrain analysis ➔ Channels ➔ Channel Network and Drainage Basins**
    
    - Input file: Filled DEM ; Output files: “Strahler order” and “Channels”

Fifth step: 
    Correct manually the location of the outlet point(s) so that they match the stream network. If the location of the water intake (made in step one) is not exactly on the stream network, create a new .shp file that is exactly in the middle of the stream network pixel
    
    - **Layer ➔ Create Layer ➔ New Shapefile Layer**
    
    - Specify the name (example TR_outlet_EPSG2056) and save it in the folder “Outlet_locations_on_dhm25”
    
    - Geometry type **“Point”** and **EPSG:2056**
    
    - Right-click on the newly created Layer ➔ Toggle Editing ➔ Add point feature 
    
    - Click on the point where there is the water intake

Sixth step: 
    Extract coordinates of the Outlet Point
    
    - **Right-click on the new Outlet.shp ➔ Open Attribute table ➔ Open Field Calculator**
    
    - In the middle panel, select **Geometry ➔ Double-click on $x ➔ Set Output field name to “X-coord”**, and Output field type to “Decimal number (real)”. Do the same for Y.

Seventh step: 
    Generate Watershed of the Stream Network
    
    - **Processing Toolbox ➔ SAGA ➔ Terrain Analysis ➔ Hydrology ➔ Upslope Area**
    
    - Open the Attribute Table of the “Outlet Point” and copy/paste the X-Y coordinates in the Upslope Area window (Target X and Target Y)
    
    - In “Elevation”: Filled DEM
    
    - In “Method”: [0] Deterministic 8

Eighth step:  
    Convert the Upslope Area raster to a vector
    
    - **Raster ➔ Conversion ➔ Polygonize (Raster to vector)**
    
    - In the “Vectorized” window save the Upslope Area are with a “out.shp”
    
    - Save the out.shp file in the folder “Watersheds_on_dhm25”

Ninth step:
    Calculate out.shp area:

    - Open the Attribute Table of the “out” file , open the Field calculator and paste:

    ``area(transform($geometry, 'EPSG:2056', 'EPSG:2056'))``

    - Save the area (integer only) in a `.txt` file in `Watersheds_on_dhm25`  
    First line: `Area`  
    Second line: area value (without decimals)