Delineating catchment with >3000 lakes in shp file

[Louise Malmquist]

Hi all

I wonder if anyone has ideas/suggestions on how to deal with a catchments with thousands of ponds/reservoirs/wetlands and delineation errors? 

I have produced a shp file and dissolved all adjacent shapes of the same classification (reservoir/pond/wetland respectively - henceforth called lakes). After creating streams from DEM I have also removed the lakes that do not intersect with the stream network. Still I have >1000 lakes remaining. 

My problem lies in that i get the error message that the streams cross lakes multiple times, which is the case for about 1/3rd of the lakes.

Even though I click OK on the correction that "the last outlet for the streams within the lakes will be considered as the true outlet", I am unable to continue to delineate any HRU and continue to next step, as I get the error that the stream links do not match the outlets.

My question is how to deal with so many un-synced shapes to avoid error messages? Is there a way to correct them as a bulk, rather than one-by-one in editing mode as this requires significant amount of time?

Would greatly appreciate your suggestions. Thanks!

[Louise Malmquist]

Hi!

It was a while ago I posted this thread, would like to bring it up as the issue still remains.

I tried to solve the problem by erasing the lakes not intersecting with streams, and have now approximately 900 lakes/wetlands remaining. I have manually delineated the lakes after instructions in QSWAT manual and ensured that streams are inside the lakes without multiple crossings and the other errors that the manual describes.

Still I get the following error messages:

"Failed to find outlet for Lake XX"

"Outlet point 1311 at (435669.99999999977, 6475690.0) not coincident with start of channel link 1705"

"ID value 23 from inlets/outlets file C:/SWAT/Tidan202030m100ha20221014LimReservoirs_230113/Watershed/Shapes/drawoutlets_snap_snap.shp not found as DSNODEID in channels file C:/SWAT/Tidan202030m100ha20221014LimReservoirs_230113/Watershed/Shapes/DEM_BSR50m_AdjSkogdataAdjLine_30mIntchannel/DEM_BSR50m_AdjSkogdataAdjLine_30mIntchannel.shp. Will be ignored.

This can be caused by an occasional error in delineation: try rerunning 'Create watershed'."

As the effect of waterbodies is an important part of my project, I would very much appreciate help on how to deal with them to get my model running.

I have attached the lake file, the txt-in-txt out file does not generate when I load

Kind regards,

Louise  

[Louise Malmquist]

After getting assistance with this issue:

Problem solved by 

- adding wetlands to Land use raster instead of including as polygons.

- Removing polygon lakes that did not intersect with the stream network

- Lakes smaller than smallest raster pixel area (here 30x30m) were erased to have outlets and inlets in separate pixels 

- Remaining lakes were manually adjusted to avoid multiple crossings of streams within lakes

Thanks for the help

Best,

Louise

[Tala Ham]

Hi Louise,

I recently came across your insightful post in the QSWAT group about delineating catchments with lakes in a SHP file. Your approach and solution seem highly relevant and useful, not just for my project, but potentially for others in our group as well.

In your post, you mentioned successfully addressing the challenge by:

Adding wetlands to the land use raster.
Removing non-intersecting polygon lakes.
Erasing smaller lakes for clearer outlet and inlet demarcation.
Manually adjusting remaining lakes to prevent multiple stream crossings.
Could you please provide more details or visual aids on how you executed these steps? I am particularly interested in understanding how to effectively delineate lakes, as it closely aligns with a challenge I'm facing in my work.

Additionally, another member in our group posted a related question under

Incorporating a Centrally Located Terminal Lake in a Watershed (google.com)

I believe your expertise and experience could greatly assist them as well. It would be wonderful if you could take a look and possibly share your insights.

Thank you for your valuable contribution to the group, and I look forward to your response.

Best regards,

[Tala Ham]

Hallo Louise,

I recently came across your insightful post in the QSWAT group about delineating catchments with lakes in a SHP file. Your approach and solution seem highly relevant and useful, not just for my project, but potentially for others in our group as well.

In your post, you mentioned successfully addressing the challenge by:

Adding wetlands to the land use raster.
Removing non-intersecting polygon lakes.
Erasing smaller lakes for clearer outlet and inlet demarcation.
Manually adjusting remaining lakes to prevent multiple stream crossings.
Could you please provide more details or visual aids on how you executed these steps? I am particularly interested in understanding how to effectively delineate lakes, as it closely aligns with a challenge I'm facing in my work.

Additionally, another member in our group posted a related question under 

Incorporating a Centrally Located Terminal Lake in a Watershed (google.com)

I believe your expertise and experience could greatly assist them as well. It would be wonderful if you could take a look and possibly share your insights.

Thank you for your valuable contribution to the group, and I look forward to your response.

Best regards,

Tala

On Wednesday, February 1, 2023 at 6:59:30 PM UTC mq.l...@gmail.com wrote:

[Awel Seid]

Hello, dear  Louise and the rest of the group members,

May you check out this new video I made to solve the problem of delineating a terminal lake watershed using QSWAT/QGIS? Lake Watershed Delineation using QSWAT/QGIS | Reservoir Watershed Delineation: https://www.youtube.com/watch?v=Rl2voep35-Q ?

Reply