Weather Gage Locations

[dchappell]

All:

I was just wondering where (and how) the SWAT 2005 model (the back-
end, not the interface) uses gage latitude/longitude data. According
to the documentation, SWAT 2005 does not need the lat/lon values for
rain or temperature gages, but I'm told that it'd need to know where
the gages are located.

Is this a problem? Any help would be appreciated!

Daniel

[Naresh]

Each subbasin uses the temperature/precipitation data from the nearest
gage location. If you are using custom weather stations then SWAT uses
the lat/lon information to find the nearest gage for each subbasin.
This information has to be updated in the userwgn table in
SWAT2005.mdb.

[dchappell]

Naresh,

Thanks for getting back to me on this.

I note that there is a lack of an MDB file in the SWAT2005 directory.
I totally agree with everything you said (it makes sense to me), but I
don't think SWAT is using my data. I have a nasty feeling that it's
using the data in the files and just assuming the data from record 1
goes with sub-basin 1. I'm not sure what to think about this <i>a
priori</i> assumption. It was just a point of interest to me that it
is doing that, and I was hoping someone might have something to say
about it.

I appreciate your help!

Daniel

[Naresh]

SWAT2005.mdb can be found under the installation directory. Typically
it should be somewhere here,

C:\Program Files\Swat\ArcSWAT\Databases

although it may be slightly different for you.

Some pointers if you have already set-up the model,

1. Go to your project under Scenarios\Default\TxtInOut and open the
file.cio. Under the climate section look for the NRTOT variable which
tells you how many gages are being used in the simulation

2. The files pcp1.pcp and tmp1.tmp under the same folder will list out
precipitation and temperature data for all gages.

3. If you open any of the .sub files, under the "Climate in subbasin"
section, the variables IRGAGE and ITGAGE tell which precipitation and
temperature gage, respectively was used for that particular subbasin.

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[dchappell]

Naresh,

I took a look at the sub-basin file, and it showed the value for which
gage was to be used (1 - 16, in this case). That's what I
figured...but then I noticed that the sub-basin's latitude is also in
the file. I was unaware of that.

An an FYI: I'm using the pure SWAT 2005 model. I don't have access to
any GIS suite, so I cannot run any of the others. I've developed a
pretty good method for feeling my way around the command-line
version :)

Thanks for the advice, though, as I found what I was looking for.
I'll be sure to report that to my supervisor on Monday.

Daniel