Estimate the total discharge at selected outlet

[majid sueed]

Hi all,

I am trying to estimate the total discharge on selected outlet by using SWAT, and I try to calibrate SWAT parameters. I read SWAT INPUT/OUTPUT documentations. I couldn't find clear answer about to estimate the total discharge on a selected outlet. However, I am adding all  FLOW_OUTcms value (which is located in output.rch) of each reach. For example, I have 7 reaches, and I sum up the value of the 7 reaches together to estimate the discharge. But unfortunately, the simulated discharge is way less than the measured discharge at this outlet! 

Please, may you advice me if this is the right way to estimate the discharge?

I appreciate your time and help!

Thanks, 

Majid 

[Jim Almendinger]

The flow-out in the reach output file already includes all the flow from upstream subbasins -- there is no need to add them together.  This will make your simulated discharge even less than before, of course.  Check to make sure your simulated flows are not plotted on a log scale, which will make them appear less.  Otherwise, you've got a problem with too little input (precipitation) or too much loss (ET, deep seepage).  Make sure your precipitation values are large enough and in the right units (mm).  

-- Jim

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James Almendinger, Ph.D. Director, St. Croix Watershed Research Station 16910 152nd St N, Marine on St Croix, MN  55047 e: jalmen...@smm.org o: 651-433-5953 x 11 https://www.smm.org/scwrs

[majid sueed]

Thanks James for your valuable answer. I just have more question about your answer:

1- "The flow-out in the reach output file already includes all the flow from upstream subbasins" So that means, the reading of the last reach (which is 

reach no 7 in my study) represents the water discharge at the outlet?

2- "Check to make sure your simulated flows are not plotted on a log scale"  You mean uncheck the option in SWAT Simulation>Run SWAT>Print Log Flow?

3-"Otherwise, you've got a problem with too little input (precipitation) or too much loss (ET, deep seepage)." I'm trying to figure out how to change SWAT parameters. My method is by change the parameters in TablesIn> access database and then I go to ArcSWAT>Edit SWAT input>Rewrite SWAT input file, and then run the model. 

My second method is by change SWAT parameter through TxtInOut folder and choose for example basins.bsn...

The two methods didn't add any change for Flow_OUTcms before and after the change.

I updated SURLAG, IEVENT and ICN. But as I said there was no change!

Please, I am looking forward to your help!

Thank you so much,

Majid

[Jim Almendinger]

Parameter changes are made in your named project data base, in the main root directory of your project, not (usually) in the TablesIn folder. 

Modifying the text files in TxtInOut should have worked, but perhaps the parameter you changed was not very effective.  Some parameters (like SURLAG I believe) can be changed in either bsn or hru, and if values are >0 in hru then they take priority over the value set in bsn. 

-- Jim

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From: "majid sueed" <majid...@gmail.com>
To: "SWAT-user" <swat...@googlegroups.com>

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