toy model - is it possible to create a single HRU?

[Camilla Negri]

Hi there,

Please see details below.

SWAT+ Issue Report Template

1. Primary Issue Location

• Component: QSWAT
• Area of impact: Model input - HRU creation

2. Software Versions

• QSWAT +  3.1.2

3. Project Characteristics

• Watershed Details:  2852 ha, 7 subbasins, 109 HRUs created, Located in Ontario, Canada
• Modeling Aim: water balance and water quality

4. Description of Issue

• The Problem: I would like to create a small toy model with one (or a few, but less than 5) HRUs to conduct a few quick tests. I am wondering whether this is at all possible?
• Step to Reproduce: No error. I created a 1 soil raster and a 1 land use raster to do this, then I tried to make the HRUs have only the [0, 9999] slope bands. It seems this creates a minimum of 109 HRUs, which feels like too much for my purposes - whichever HRUs options I choose. Is it at all possible to make 1 HRU or does the fact that we have 7 subbasins already hinder this?

5. Supporting Data (Optional)

• Link to project folder: I don't have one but can share folder if needed 

Any help with this is appreciated.

Many thanks and best wishes,

Camilla 

--

Camilla Negri

Postdoc Fellow, Toronto Metropolitan University

ORCID iD https://orcid.org/0000-0001-8917-5322

[Chris George]

There must be at least one HRU per channel reach. To get a small
number, say 5, proceed as follows:

1. Set the stream threshold high enough to get only 5 subbasins. (Or
move the main outlet upstream until there are only 5 subbasins upstream
from it.)

2. Set the channel threshold the same as the stream threshold.

3. Choose either of the first two HRU creation options, both of which
give one HRU per channel reach. You do not need special landuse or soil
rasters.

Chris

On 5/1/2026 11:59 PM, 'Camilla Negri' via QSWAT+ wrote:
> Hi there, Please see details below. SWAT+ Issue Report Template 1.
> Primary Issue Location Component:  QSWAT Area of impact:  Model input -

> HRU creation 2. Software Versions QSWAT +  3. 1. 2 3. Project

> Characteristics Watershed Details:   2852 ha,

> ZjQcmQRYFpfptBannerStart
> This Message Is From an External Sender
> This message came from outside your organization.
> ZjQcmQRYFpfptBannerEnd

> Hi there,
>
> Please see details below.
>

> *SWAT+ Issue Report Template*
>
> *1. Primary Issue Location*
>
> * *Component:* QSWAT
> * *Area of impact:* Model input - HRU creation
>
> *2. Software Versions*
>
> * *QSWAT +  3.1.2*
>
> *3. Project Characteristics*
>
> * *Watershed Details:*2852 ha, 7 subbasins, 109 HRUs created, Located
> in Ontario, Canada
> * *Modeling Aim:* water balance and water quality
>
> *4. Description of Issue*
>
> * *The Problem:* I would like to create a small toy model with one (or

> a few, but less than 5) HRUs to conduct a few quick tests. I am
> wondering whether this is at all possible?

> * *Step to Reproduce:* No error. I created a 1 soil raster and a 1

> land use raster to do this, then I tried to make the HRUs have only
> the [0, 9999] slope bands. It seems this creates a minimum of 109
> HRUs, which feels like too much for my purposes - whichever HRUs
> options I choose. Is it at all possible to make 1 HRU or does the
> fact that we have 7 subbasins already hinder this?
>

> *5. Supporting Data (Optional)*
>
> * *Link to project folder: *I don't have one but can share folder if

> needed
>
>
> Any help with this is appreciated.
>
> Many thanks and best wishes,
> Camilla
> --
>
> Camilla Negri
>
> Postdoc Fellow, Toronto Metropolitan University
>

> *ORCID iD *https://orcid.org/0000-0001-8917-5322 <https://
> urldefense.com/v3/__https://orcid.org/0000-0001-8917-5322__;!!KwNVnqRv!
> AqGZsbQdSxW3zv0_Ij-
> t2loCIxtjooQBWkznzGtoqs_dBUxVS7SiSa1vzLAdm6o5aWMVNKfqNXbDKrHn6HfPDZE$>
>
>
> --
> You received this message because you are subscribed to the Google
> Groups "QSWAT+" group.
> To unsubscribe from this group and stop receiving emails from it, send
> an email to qswatplus+...@googlegroups.com
> <mailto:qswatplus+...@googlegroups.com>.
> To view this discussion visit https://groups.google.com/d/msgid/
> qswatplus/d4b02acd-cd9e-4275-b5ab-7c6903662a85n%40googlegroups.com
> <https://urldefense.com/v3/__https://groups.google.com/d/msgid/
> qswatplus/d4b02acd-cd9e-4275-b5ab-7c6903662a85n*40googlegroups.com?
> utm_medium=email&utm_source=footer__;JQ!!KwNVnqRv!AqGZsbQdSxW3zv0_Ij-
> t2loCIxtjooQBWkznzGtoqs_dBUxVS7SiSa1vzLAdm6o5aWMVNKfqNXbDKrHnajXsb38$>.