1 - Delineating Watershed in QGIS

[@robmcewan7943]

Really great to find high quality, well described videos like this. Thanks John!

[@gugumgumilang5042]

THANK YOU SO MUCH JOHN!!! I had a problem where my vectorized raster can't make a proper Thiessen Polygon. Your video helped me to check in the attribute table and made me realized that there were 30 polygons :')

[@mohamedelgamal6333]

Many thanks, John for the nice and clear presentation. It is really very helpfull.

[@kopirobustaofficial5709]

Thanks John, for the tips and tutorials. This is very helpfull, especially for a beginner like me.

[@NjectRevenge]

Thank you very much, best tutorial on the matter so far :)

[@divyasrini1]

A really great video tutorial. Very well explained and demonstrated. Could you please show the same using Remote Sensing (Earth Engine) data in QGIS. Maybe use some Python as well? Thanks.

[@managana]

Excellent tutorial

[@kinjaldutta5503]

Good day! How can one find morphometric parameters like stream length , bifurcation ratio of this watershed using QGIS?

[@johnedwards4115]

When running the channel network and drainage basins tool, select the Strahler order button to get your stream orders, however this comes out as a raster I believe. You can get stream lengths from the channels vector file that you create in the same tool as above using the raster calculator. Then you could just associate each vector with its stream order to give you the data for the bifurcation ratio

[@kinjaldutta5503]

@@johnedwards4115 Thanks a lot sir! Your video was helpful.

[@shimafarahani6492]

Thanks, It is too helpful.

[@adamuel-oji3510]

Thanks sir for this exciting video. I have this challenge with SAGA Plugin Whenever I run Fill L &G, get error as SAGA 7 .2. 8 is not a support for windows. What's the solution, please.

[@sssoha8626]

How you cut that little pice of DEM? Its very useful this tutorial, and i really apreciated this video.

[@johnedwards4115]

I'm not sure which part of the DEM you are referring to. Or are you referencing the vector shape of the watershed produced at the end of the video?

[@sssoha8626]

For exemple: i got a DEM whit Hungary, Ukraine, and North West of Romania. I think this area is to big for my laptop... Maybe i need to clip my interes area first. Sorry for my english.

[@johnedwards4115]

@@sssoha8626 No worries. You can just use the raster clip tool. You can either use a polygon to clip or select an extent on screen to reduce the size of your DEM. It all depends on how big of a watershed are you are needing. If your area is extremely large (e.g., watershed for a major river), you can always resample your DEM to a larger cell size to reduce the file size

[@sssoha8626]

@@johnedwards4115 Hello again. I selected a my area whit a polygon and i try it to clip that region, but it show me this: The following layers were not correctly generated. You can check the 'Log Messages Panel' in QGIS main window to find more information about the execution of the algorithm. I can't find de problem. i know your title was about "Deliniating a Watershed in QGIS" , and is not right to ask you about this problem. Thank you again for information.

[@paladyeproject]

will qgis always calculate the area in ft^2? how can I change the output to metric or does it depend on the dem file which system is used?

[@johnedwards4115]

The units for area are based on the units of your coordinate system. In this case I had a coordinate system in USft, therefore ft^2. You can always add the conversion factor in the calculation of the area, or afterward, if you want units other than for your coordinate system. For Q calculations based on the Regional Regression equations the area is in square miles anyway, so even the ft^2 need to be converted.

[@nprakash007]

While going for the upslope area an error occurs stating missing / wrong parameter value..no idea!!

[@kevinmurphy3408]

Whenever i try to run in Fill Sinks XXL in QGIS 3.12.3, an error message appears: "Las siguientes capas no se generaron correctamente.C:/Users/Lenovo/AppData/Local/Temp/processing_PvhdrT/18d11ce521e74a3c9bb68d2bb82b4d10/FILLED.sdatPuede comprobar el «Panel de mensajes del registro» en la ventana principal de QGIS para encontrar más información sobre la ejecución del algoritmo." Please, can you, or might you know someone that could help me? I would appreciatte a lot!. Im from Argentina.

[@johnedwards4115]

Whenever I get this error that the layers were not correctly generated its often one of just a few problems: 1) Sometimes saving to a file, instead of a temporary file works better; 2) Your raster input file is too large, in which case you might need to resample to a lower resolution; and 3) There are errors in you DEM, perhaps due to clipping or a collar of no data. Hope this helps.