negative parameter value for CN2

[Sheila]

Hi Swat Cup users. I am still using SWAT CUP 313. I wanted to double
check that I am understanding the nomenclature:

If my final calibrated r_ CN2.mgt value is -0.05. This means I
multipy my CN2 values by 0.95, right? In other words, this -0.05
means I should decrease values by 5 %, correct?

Thanks.
Sheila

[Srini]

Yes.

R. Srinivasan Director and Professor
r-srin...@tamu.edu Spatial Sciences Laboratory
http://www-ssl.tamu.edu Texas A&M University

[Sheila]

Thanks Srini!

On May 13, 10:18 pm, "Srini" <r-sriniva...@tamu.edu> wrote:
> Yes.
>
> R. Srinivasan       Director and Professor

> r-sriniva...@tamu.edu                  Spatial Sciences Laboratory  http://www-ssl.tamu.edu    Texas A&M University

[David Coffman]

As a follow up to this question...what is the best way to edit all the CN values.  There are different CN values for each HRU, and I have a lot of HRU's.  Is there any way to automate this process to apply the adjustment factor to all CN values without editing them individually for each HRU?

 

 

On Mon, May 14, 2012 at 5:48 PM, ArcSWAT <danilof...@gmail.com> wrote:

Yes, I think it's right. I work it the same way.

Danilo

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[Karim]

... You have all those examples and still ask this question!

In par_inf file you write

r__CN2.mgt.     R1.  R2

with the rages R1 and R2 and this will change CN2 in all mgt files..

[David Coffman]

Wow....  I just now made the connection.  The SWAT_CUP files from my best interation are used to replace the input files in my SWAT model.  I wish I would have realized that earlier, because I spent quite a bit of time manually changing input values using the ArcSWAT interface. 

 

Thanks, Karim.

[Elham Rouholahnejad]

If you dont address an specefic hru, the changes will be global.

Using the reletive changes, you have the oppertunity to increase or decrease all values....

e.g.    r__CN2.mgt     0.0    0.4

Elham

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From: David Coffman <dkco...@gmail.com>
To: ArcSWAT <danilof...@gmail.com>
Cc: swat...@googlegroups.com
Sent: Wednesday, May 23, 2012 4:40 PM
Subject: Re: [ArcSWAT:4181] Re: negative parameter value for CN2

[Mike]

What's the rational for using percent change instead of curve number values?

[Karim]

... There are three ways to change a parameter, r, a, and v

Please look at the manual for explanation. Be aware that replacing spatial parameters with a value without specifying the individual subbasin number, will change everything to the same value, hence getting rid of the spatial variability in your system.

Best, 

Karim

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[David Coffman]

Each HRU has a curve number value associated with it withough the .mgt file associated with the HRU.  It is my understanding that the initial Curve Number applied to each HRU is dependent on the landuse/land cover and soil type in the HRU.  It would be impossible and probalby pointless to try to calibrate each CN value in every HRU by manually adjusting the values.  The percent change forces all CN values in your calibration subbasins to change up or down and equal amount during each iteration.  I hope this helps clarify. 

 

Dave

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