SSURGO and MUID as Name

[Derek]

I am new to ArcSWAT and am trying to determine the best way to utilize
SSURGO data. What I have come up with thusfar is as follows:

1) Use Arcivew 3.x SSURGO SWAT tool to create a usersoil.dbf data
table (from chorizon.txt, comp.txt and mapunit.txt)

2) Convert SSURGO polygon features into GRID, preserving MUKEY
field.

3) Add "MUID" field to usersoil.dbf (generated by SSURGO SWAT) and
calculate as "SD" + right three values from MUKEY or SNAM fields in
usersoil.dbf.

4) Append usersoil.dbf to usersoil table in SWAT2005.mdb.

5) Import SSURGO GRID into ArcSWAT using lookup table for GRID code
and NAME. Note that name in lookup table looks like "AXXXXXX" where
XXXXXX is the MUKEY value.

The confusion I am having with the use of MUKEY or even NAME (as
AXXXXXX) is that there are cases where MUKEY has two instances within
mapunit.txt and this propagates through the process to the usersoil
table. How can MUKEY used as the identifier if it is not unique? It
seems to me that the SEQN field in usersoil.dbf should be appended to
the end of the MUKEY to create the SNAM field in usersoil.dbf. And
the GRID lookup table would use a simliar naming convention. Is there
a reason that this is not necessary?

Regards,
Derek

[mcl...@gmail.com]

Hi again Derek ,

As far as I know, the MUKEY can be extracted from "old" STATSGO
dataset directly. However, SSURGO is a detail soil dataset, that
meant it use several components (COKEY) to represent single MUKEY.
(If you read through SSURGO table specifications, you can find out
their relationship.) In other words, for the SSURGO dataset, a single
geospatial block (so call SURVEY AREA) will have several soil subset
(COKEY) in percentage (COMPPCT_R). Each COKEY also has its "horizon"
properties recorded in chorizon.txt. However, SWAT only use ONE soil
data for any single SURVEY AREA, that means you can just choose one
soil subset (COKEY) to represent the MUKEY by percentage (major
component) or do the weighted calculation.

FYI, to clean up and prepared the SSURGO data for SWAT, we developed a
VBA program on MS Access to automatically import .txt files and
generate soil data table.

GOOD LUCK,

Ming-chieh Lee