Subject: Location of Pour Points and Number of Catchments in Automatic Catchment Delineation Posted: 11/10/2024 Viewed: 230 times
Dear All,
How can we determine the optimal number of catchments and locations for pour points in a large basin to balance model accuracy and runtime efficiency using the automatic catchment delineation mode? Should pour points be placed immediately upstream or downstream of dams and demand nodes, at the confluence points of tributaries, or as a combination of these or other locations? Based on your experience, what would you recommend as the ideal number of catchments for a basin with an area of approximately 360,000 km² and a length of 1600 km? Additionally, where would you suggest locating the pour points?
Thank you for sharing your insights.
Kind Regards,
Selam
Mr. Doug Chalmers
Subject: Re: Location of Pour Points and Number of Catchments in Automatic Catchment Delineation Posted: 11/11/2024 Viewed: 198 times
Selam,
I would place catchments immediately upstream of locations where you need the calculated flow to be accurate. I would place catchment drainage areas to end immediately upstream of each observed flow gauge, each reservoir, and each major demand diversion.
If you have a large upstream area where you do not need to calculate the intermediate flow anywhere, then you likely wouldn't need to split up into multiple catchments.
In general, each hydrologic parameter (runoff resistance factor, soil water capacity if using the soil moisture method) is the same for each land class across all catchments in a given model. For example, you would have one value for runoff resistance factor to apply for all Grassland land classes across all catchments. For this reason, splitting up more catchments may not have significant effects on model results. Additionally, unless you have a very large model, the runtime shouldn't be a big issue for thinking about catchments.
-Doug
Eng. Selam Sahlu
Subject: Re: Location of Pour Points and Number of Catchments in Automatic Catchment Delineation Posted: 11/11/2024 Viewed: 190 times
Dear Doug,
Thank you very much for your clarification and detailed explanations. I have a follow-up question about the automatic catchment delineation process. When delineating the catchment, a pop-up window sometimes shows both the catchment name and river name, while at other times only the catchment name appears. In the first case, there is a river that flows into the main river, whereas in the second case, there is a runoff infiltration link that connects to the river. Does this difference significantly impact the flow toward the main river?
Thank you once again.
Kind Regards,
Selam
Mr. Doug Chalmers
Subject: Re: Location of Pour Points and Number of Catchments in Automatic Catchment Delineation Posted: 11/11/2024 Viewed: 180 times
Selam,
I would pay attention to the location where each runoff link enters your river. These are the locations where your inflows from your catchments will add to the streamflow in the river. You'll need to ensure their configuration will create accurate flow at the important points of interest in your watershed (observed gauges, reservoir inflow, diversions, etc.) as described above.
-Doug
Eng. Selam Sahlu
Subject: Re: Location of Pour Points and Number of Catchments in Automatic Catchment Delineation Posted: 11/12/2024 Viewed: 168 times
Thank you, Doug. It's very helpful.
Kind Regards,
Selam
Topic "Location of Pour Points and Number of Catchments in Automatic Catchment Delineation"
