Complete QGIS Watershed Delineation Tutorial
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- Опубліковано 5 лют 2025
- In this tutorial, we walk you through the process of generating multiple catchments/ watersheds using QGIS, which is a powerful open-source GIS tool.
A watershed or catchment is an area of land where all surface water converges to a single point, making its analysis crucial for hydrology, environmental management, and urban planning. We'll begin by discussing the importance of using GIS tools like QGIS or ArcGIS for precise watershed delineation. You'll learn how to obtain and work with a Digital Elevation Model (DEM), which is essential for accurately mapping terrain and water flow. We’ll cover key concepts like Strahler stream order to derive river networks and then guide you through the steps of generating catchments. Additionally, we’ll perform geometric computations, such as calculating catchment areas, to help you fully understand the spatial characteristics of the watersheds.
One of the tools that we are going to rely on during the delineation process is SAGA tools, which can be installed as an external plugin on QGIS. It has been brought to attention that some QGIS versions encounter issues when working with SAGA tools, and specifically when running an algorithm related to a tool called Upslope Area. During this tutorial, we are also discussing that issue, and we are offering a potential solution for that as well for those who are encountering this issue along the way.
We start this tutorial from scratch, and work our way up at a decent pace so that even if you are new to using these GIS tools, you will have plenty of time and applications through which you would be able to become proficient in using the tools by the end of this tutorial.
For your convenience, the structure of the video has been listed below. If you wish to skip over to a specific part of the video, feel free to use the time stamps.
00:00 - Introduction
01:28 - DEM data downloading
02:01 - Adding DEM data to QGIS workspace
07:29 - Checking the relevant UTM zone for DEM reprojecting
10:07 - Defining the area of interest using a polygon object and clipping the DEM
16:30 - Using SAGA fill tool for correcting the DEM irregularities
19:54 - Deriving stream order using Strahler Order method
31:27 - Deriving the river network in as a polyline type vector layer
34:12 - Deriving a single watershed using SAGA Upslope Area tool
41:33 - Discussing issues with errors when running Upslope Area tool, and the potential fix
46:09 - Generating multiple sub-catchments using batch processing
01:05:43 - Calculating areas of sub-catchments
Link to download the data for this tutorial - drive.google.c...
Downloading a DEM for free using NASA EarthData tools - • Downloading Elevation ...
#hydrology #QGIS #delineation
The QGIS version that I'm using in this tutorial is QGIS 3.34 Prizren (LTR), In case if you want to make sure you have the same version installed at your end to potentially not have any version conflicts.
Thanks Sir for your content! I follow you since 4 years. I meet issues using Saga tools in qgis. all Saga algorithms used to derive river networks and catchment delineation don't work in all QGIS version. Could you please help fix that issue?
@@loicndzang3839 did u find a fix for the saga upslope area?
@@LordLegion-d4b not yet. I used the Saga GIS to do my project I better do it in QGIS but saga algorithm don't work anymore
@@loicndzang3839 whats saga his? Another software? Hope u help me on this
i HAVE BEEN SPENDING LOT OF TIME WATCHING TUTORIALS OF LATAM, BUT MUCH OF THEM AREN'T ABLE TO EXPLAIN CORRECTLY WHAY THEY'RE USING SOME TOOLS AND THE PRODUCT OF THESE STEPS I'VE FOLLOWED WERE A MESS.
THANX ALOT GEO DELTA, YOUR MY HERO (that data it that makes me feel mor confindent to start my tesis)
Thank you very much. Your tutorial is amazing and the explanation is very well-detailed. I hope you continue developing this content.
Thank you, I will
Finally I can design my bridges from scratch..thanks GeoDelta
Thankyou for uploading such a nice educative content. It is very useful
Excellent video
thank you for this video, it was a great help for me
This is very Helpful thank you sir.
Thank you very much for the step-by-step tutorial.
I was able to generate the streams network but my catchment area delineation step resulted in rubbish. The watershed resulting from the UpSlope tool were butchered (too small, or just a line, outside the streams). I've repeated it so many times and made sure the coordinates are correct, but same rubbish results
Thank you so much!
Thanks for the great content
No worries!
Thank you for this very informative video. Do you, by any chance, know how to extract the lineament density of a catchment from a 1m DEM? It would be useful to have a tutorial on this topic. Thank you!
When it is required to use Projected Co-ordinate system and UTM zones are unknowm, just use EPSG:3857. it is pseudo-mercator projection. It is similar to UTM projection. EPSG:3857 has unit meters.
Awesome tutorial dude! I have a doubt, save the raster with the "Save as" have the same effect as the Warp(reproject)?
The ta_hydrology_upslope_area file does not exist, instead a file ta_hydrology_upslope_height is visible in QGis folder. Do you have any idea in this case as error message is exactly same as you mentioned.
Same question. Please let me know how to fix this issue😒
sir could you please make watershed delineation map of Pennar river sir
I proceeded all along, but has not got any stream network, just random pixels. Also the suggested approach seems not to work if one has to delineate the catchment area of the reservoir and the river dale is wide.
I was able to generate the streams network but my catchment area delineation step resulted in rubbish. The watershed resulting from the UpSlope tool were butchered (too small, or just a line, outside the streams). I've repeated it so many times and made sure the coordinates are correct, but same rubbish results
@aminmneina6317 I used HEC HMS and the results obtained were very good. QGIS is not suitable for hydrology. My professor was right. Use HEC HMS. Easier and much more precise.
hOW DO YOU INDICATE DIRECTION OF FLOW
Merci
You are welcome!
Thank you for this helpful tutorial. Could I ask for your assistance with an error message I encountered while processing the channel network and drainage basin: 'The following layers were not correctly generated.' Your help would be greatly appreciated.
A potential fix for this that may work is making sure you are running one of the recent versions of QGIS (such as QGIS 3.34 LTR - Prizren, which is what I happen to use currently), and then install SAGA Next Gen Provider plugin on that. You might be able to circumvent the version issues that way.
@@geodeltalabsI installed QGIS 3.34 Prizren version and it works perfectly. Thank you so much.
Sir I request you to please provide us advance class of RS and GIS we will paid for that....
Thank you
I have followed every step precisely but I'm getting an error saying "COORDINATES OF TARGET POINT OUTSIDE DEM" any solution please
😢😢😢😢😢😢😢😢😢
I ran into that too. Check your DEM coordinate (through it's properties). now your Canvas coordinates are probably different from that (found on the bottom right corner of your screen). click on your Canvas coordinates and change them to your DEM's coordinate system
my fill sinks(wang&liu) process is very long, it has been 2 hours already, any idea why this happens?
seems like an issue with the input DEM? mine took 10 seconds