Watershed analysis is a fundamental process in hydrology and water resource management. Traditionally, this analysis required a significant time investment. However, modern Geographic Information System (GIS) tools have revolutionized this process. This tutorial demonstrates how to use QGIS with the ArcGeek Calculator plugin to perform a comprehensive watershed analysis in a matter of seconds.
Prerequisites
QGIS 3.x (version 3.38 recommended)
ArcGeek Calculator plugin installed in QGIS
Digital Elevation Model (DEM) of the study area
1. Generating the Stream Network
- Launch QGIS and load the DEM of the study area.
- Activate the ArcGeek Calculator plugin.
- In the menu bar, go to Plugins > ArcGeek Calculator, select “Stream Network with Order”.
In the tool dialog:
- Select the DEM as “Input DEM”.
- Specify the appropriate “Flow Accumulation Threshold” for your study area.
- Configure smoothing parameters as needed.
- Run the tool.
Verify the resulting stream network on the QGIS map.
2. Watershed Delineation
In the menu bar, go to Plugins > ArcGeek Calculator, select “Watershed Basin Delineation”.
In the tool dialog:
- Select the DEM as “Input DEM”.
- Define the “Pour Point” (watershed outlet) by drawing on the map.
- Adjust smoothing parameters if necessary.
- Run the tool.
Examine the delineated watershed on the QGIS map.
3. Calculation of Morphometric Parameters
Select “Watershed Morphometric Analysis” in the menu bar under Plugins > ArcGeek Calculator.
In the tool dialog:
- Select the generated watershed layer.
- Select the stream network layer.
- Specify the field containing the stream order.
- Select the original DEM.
- Define the watershed outlet point.
- Run the tool.
Analyze the results table with the calculated morphometric parameters.
Results and Analysis
The described process generates three main data sets:
- Stream network with stream orders
- Precise delineation of the watershed
- Complete table of morphometric parameters
These results allow for:
- Detailed analysis of watershed morphology
- Evaluation of drainage patterns
- Estimation of susceptibility to extreme hydrological events
- Efficient planning of water resource management
The integration of QGIS with the ArcGeek Calculator plugin significantly optimizes the watershed analysis process. This methodology allows for complex analyses to be performed in seconds, facilitating more frequent and detailed studies, and improving decision-making in water resource management. If you find any errors in the calculation, you can report them in a comment. It is recommended to use QGIS 3.38.
