Precipitation data from pcp1.pcp note being used properly by SWAT

[James Dennedy-Frank]

To whom it may concern:

I am attempting to use a set of radar data for SWAT modeling, but am finding that somewhere there is a problem that gives me unreasonable results; I am hoping that someone can help me here. 

I obtained the radar data from an EPA colleague (pre-shutdown), and did just a little bit of work to get both the individual precipitation station files and the file for the locations of the precipitation stations into the correct format. This seems to have worked, as I can use ArcSWAT to build the weather files and the resulting pcp1.pcp looks, to me, to be formatted correctly (I have attached it here). I looked at the .sub files, and they list the correct stations for IRGAGE, according to pcp1.pcp, and the precipitation values in pcp1.pcp are correct. 

However, the resulting precipitation that occurs in SWAT is incorrect. Looking at the precipitation from output.sub, it subbasin 1 looks correct--the values are identical except when pcp1.pcp is -99, when output.sub has mostly 0 values (except for 1 day when it estimates some precipitation). However, none of the other subbasins are correct. All subbasins except for 10, 23, 25, and 27 have 0 precipitation for the entire simulation period (there are non-0 values for each of these in pcp1). 10, and 27 start with 0 on the first day and then have a constant value of 0.9730 mm for each subsequent day; 23 starts with 0.9340 and then a constant value of 0.9250; and 25  has a constant value of 0.8120. 

As I mentioned, the format looks correct to me. I have a couple of thoughts but have not tested them:

1. I have 32 precipitation stations in this pcp1.pcp file--is this too many?

2. Each precipitation station is named pcpXXXXXX, leading to 9-digit names, which may cause a problem (although I think that should not be read at this point, and the IRGAGE values are assigned correctly.

If either of these are correct, or you have other suggestions about where the error might lie, I would greatly appreciate your assistance.

Best,

James

[lei qiao]

Hi James,

did you check your File.Cio file to see if you have used the measured data rather than the simulated and if the numbers of station are right? 

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Lei Qiao, Ph.D. 

Postdoctoral Research Fellow

 

Dept. of Natural Resource Ecology & Management
Oklahoma State University
008C Agricultural Hall, Stillwater, OK 74078

Office: 550 Ag Hall

Phone: 405-744-9637

Email: lei....@okstate.edu

[James Dennedy-Frank]

Hi Lei Qiao,

I am definitely using the measured data according to file.cio--otherwise subbasin 1 would not have had the correct precipitation each day over 4 years. I also checked the numbers of the stations, and they are correct.

I did get this working, but still don't know the source of the error. I went back into ArcSWAT and rewrote the files, and then did a SWAT run from ArcSWAT. This seems to have fixed it--again, I'm not sure why.

Best,

James