High NS but very small p and r factor

[Rasika Ramesh]

Hi SWAT CUP users

For one of my study watersheds - a highly urban watershed - I ran SWAT CUP in 2 iterations off 500 sims each. During manual calibration initially the SWAT stimulated flows showed high performance (NS=85%). After running SWATCUP, the NS of the behavioral set improved to 88% but p factor and r factor are very very low (p factor = 0.37 and r factor = 0.30). Below are the parameter ranges I used for the calibration and the 95ppu plot for the data following iteration 2. 

Can I use these ranges despite the low p and r factor since the NS is pretty good?

If not, how can I improve the the width of the 95ppu band and have parameters represent it?

------------------------------------------------

1st iteration

r__CN2.mgt          -0.2       0.2

v__ALPHA_BF.gw             0.0       1.0

v__GW_DELAY.gw           1      100

v__GWQMN.gw                0.0       2.0

v__GW_REVAP.gw             0.0       0.2

v__ESCO.hru                0.8       1.0

v__CH_N2.rte               0.0       0.3

v__CH_K2.rte               5.0       130.0

v__ALPHA_BNK.rte           0.0       1.0

r__SOL_AWC(1).sol         -0.2       0.4

r__SOL_K(1).sol          -0.8       0.8

r__SOL_BD(1).sol          -0.5       0.6

v__SURLAG.bsn              1.0     10.0

2nd iteration 

r__CN2.mgt    -0.03042   0.309086

v__ALPHA_BF.gw    0.433953   1.302713

v__GW_DELAY.gw    0   54.893501

v__GWQMN.gw    0   1.102085

v__GW_REVAP.gw    0   0.121542

v__ESCO.hru    0.865126   0.99554

v__CH_N2.rte    0.054685   0.218315

v__CH_K2.rte    0   68.486168

v__ALPHA_BNK.rte    0.337263   1.012737

r__SOL_AWC(1).sol    0.066372   0.599627

r__SOL_K(1).sol    -0.297672   0.708338

r__SOL_BD(1).sol    -0.112481   0.663481

v__SURLAG.bsn    1   6.454466

Thanks

Rasika Ramesh

School of Forestry and Wildlife Sciences

Auburn University

[Abbaspour, Karim]

I assume this is daily flow? It seems like the first 140 days you are overestimating the peaks and the next 100 days underestimating it. I would look into that by examining the rainfall or what management is taking place.

As discharges are very small, and in an urban area, small perturbations really show themselves in a big way! A lot of the data that falls outside of 95ppu is when the flow is near zero or zero. In this case I would recalculate the 95ppu in such a way as not to include the zero flows, or just not  worry about the low p-factor!

 

Karim

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[Rasika Ramesh]

Thank you for the clarification Dr. Abbaspour. 

Regards

Rasika

"Only when the last tree has withered, and the last fish caught, and the last river been poisoned, will we realize we cannot eat money" -  Native Cree Prophecy

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