> 5 landuses with quality

I'm sure this has been asked before, but I'm trying to clarify my understanding of the inputs for runoff quality.

All questions assume one landuse per subcatchment.

If I have one landuse, and one constituent, and want to simulate constituent buildup as a fraction of dust and dirt, then do I specify QFACT1=the fraction of the constituent in mg/g?

If I have two landuses, and two constituents, then do I enter a fraction on each constituent line for QFACT1 and QFACT2?

If I have greater than 5 landuses, then assuming my previous two suppositions are correct, then how do I add fractions for landuses > 5?

Wes Byne
fbyne@engr.uga.edu

Wes,

This snippet below shows how to model 5 land uses in SWMM. The number of J3 lines is the number of land uses times the number of pollutants. If you have ten land uses and 2 pollutants then you will have 20 J3 lines. The dust and dirt buildup parameters complicate matters. Depending on how you read the SWMM code it seems that if you use dust and dirt buildup you are limited to 5 pollutants but an unlimited number of land uses (the 5 QFACT input variables) - or it may be 5 land uses and an unlimited number of pollutants. If you use buildup/washoff or rating curve washoff you will have no limitations. We will check the dust and dirt limitation later and inform the group.

* WATER QUALITY erosion parameters -->
* JJ Line - # land uses per subcatchment
JJ 5
*
* # Pollutants # LU's Erosion(0=no)
IROSAD DRYDAY CBVOL DRYBSN RAINIT REFFDD KLNBGN KLNEND
J1 1 5 0
0
2.0 0.0 0.0 2.0 /
*
* J2 lines - one for each land use - other parameters irrelevant if no dust and dirt simulation
* LU Name
J2 'Forest' / * 1
J2 'Urban' / * 2
J2 'Mixed Urban' / * 3
J2 'barren' / * 4
J2 'mall' / * 5
*
* J3 lines - one for each constituent and land use combination
Irrelevant -->
<--
Irrelevant
* Name Units Unit Type Buildup
CalWashoff CalKACGUT(K) LINKUP(K) QFACT(1) QFACT(2) QFACT(3) QFACT(4)
QFACT(5) WASHPO EMC or RCoef
J3 'TSS' 'mg/L' 0 4
1
0 0 0 0 0 0 0 2
2.0 / * TSS Original
J3 'TSS' 'mg/L' 0 4
1
0 0 0 0 0 0 0 2
2.0 / * TSS Original
J3 'TSS' 'mg/L' 0 4
1
0 0 0 0 0 0 0 2
2.0 / * TSS Original
J3 'TSS' 'mg/L' 0 4
1
0 0 0 0 0 0 0 2
2.0 / * TSS Original
J3 'TSS' 'mg/L' 0 4
1
0 0 0 0 0 0 0 2
2.0 / * TSS Original
*
* L1 and L2 lines - land use information
* L1 Subwatershed
L1 'stream' 1 /
* the watershed is divided into five land uses
L2 0.2 0.2 0.2 0.2 0.2 /

Best Regards,
Robert Dickinson
dickinsonre@cdm.com