Very High Value of r-factor

[Salman Khan]

Dear All,

Greetings from Pakistan

I am working to calibrate a snow fed mountainous watershed. After setting up my model in SWAT-CUP Premium (v6.2) I ran an iteration with a neutral parameter just to check my model behaviour (Attachment #1). Keeping in view my initial model behaviour I tried to improve my model in terms of Elevation Bands definition. After Successful definition of elevation bands into my model I just tried to fix the lapse rates for Precipitation and Temperature. I tried another Iteration with the following given ranges: I am having a very strange 95PPU (Attachment #2).  I don't exactly know what's the problem. As I checked all the files, everything seemed fine. Any guidance in this regard is highly appreciated.

V_PLAPS       0    100

V_TLAPS       -8      -4

Attachment #1

Attachment #2

Kind Regards

Salman Khan

[Salman Khan]

Dear Dr. Karim Abbaspour and all other SWAT CUP users any guidance on the issue plz ?

[Karim Abbaspour]

use the new parameter ranges and iterate a couple of times, then fix these two parameters and calibrate for other flow parameters, CN2, etc....

Karim

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[Salman Khan]

Thanks for your kind  suggestion Dear Sir,

I dug out the problem. Actually,  I was trying to calibrate for  PLAPS and TLAPS at a time.  However, later I came to know that only TLAPS was sensitive. The very  high r-factor  was because of the precipitation lapse rate which was not  really sensitive and significant. When  I fix the  value for PLAPS as zero  then  it's  fine  otherwise, for  any  range it gives a very high value of r-factor.

Kind Regards

Salman Khan

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[Bernard Robenson]

Hi Everyone,

I have a question about setting PLAPS and TLAPS within swat-cup parameterizations. When do we need to set these two parameters? My study area doesn't have snow and its elevation is not that high. 

Kindest regards

[Salman Khan]

Dear Robenson,

In my opinion, we must consider the spatial variation of altitude within your watershed area. Also, The density and location of the climate stations which you are going to use in your study. If the elevation difference is high and you have climate stations  located in valley plains of your watershed, which will not reflect the climate of the high altitude area, Then of course, the lapse rates are significant and need to be fixed. 

Kind regards

Salman Khan

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