xpswmm/xpstorm Resource Center xps

The Global Pollutants Database allows the definition of any number of water quality constituents (pollutants). 

In order to model pollutants for a simulation, pollutants must be chosen from the 'Pollutant List' button in the 'Water Quality' dialog under Job Control. The pollutant names are used as column headings in the tabular output.

This page contains the following topics:


Options for concentration units are reasonably broad and broken into three categories. 

    1. mg/l (J3 - NDIM = 0). This option defines pollutant units of mg/l. If this item is selected the unit label is ignored. All parameters for which the quantity is measured as a mass should be suited to this option. Most pollutants are measurable in this unit. Although parameters such as metals, phosphorus or trace organics are often given as micrograms per litre, SWMM output is to 3 decimal places and is expected to be compatible with typical values of these parameters.
    2. 'Other'/l (J3 - NDIM = 1). Used when the pollutant has some per litre units other than mg/l. eg a bacteria count such as MPN/l. This unit accounts for pollutants defined by a count per unit volume.
    3. Other (J3 - NDIM = 2). This option covers parameters with specialised concentration-type units such as pH, conductivity (umho), turbidity (JTU), colour (PCU), temperature (C), etc. For these parameters, interpretation of concentration results is straightforward, but "total mass" or "buildup" is mostly conceptual. Since loads are transmitted in terms of concentration times flow rate, whichever concentration units are used, proper continuity of parameters is easily maintained.

Unit Label (J3 - PUNIT)

Unit used as heading for tabular output for units other than mg/l.

Daily Decay Rate (J3 - DECAY)

Decay rate of pollutant in units specified per day.

Add fraction (percent)

This flag indicates a fraction of this pollutant in the range 0.0 - 1.0 is to be added to another pollutant. Many constituents can appear in either dissolved or solid forms and may be absorbed into other constituents. To treat this situation, any constituent may be computed as a fraction ("potency factor") of another.

Fractional contributions are added after computing and summing all loads except those resulting from precipitation. The fraction added to the referenced pollutant will not, however, be removed from the current pollutant. If this flag is OFF, then none of the current pollutant is added to another.

To (J4 - F1). Reference to the pollutant to add fractional contributions to.

Fractional contributions are added after computing and summing all loads except those resulting from precipitation. However, the fraction added to the referenced pollutant will not be removed from the current pollutant.

Landuse Specific Data

Part of the pollutant data is also dependent on the landuse. The data fields should be entered, in turn, for each of the landuses highlighted.


A reference to the Global Database of buildup and washoff data (for the highlighted Landuse).

Linkage to Snowmelt (JX - LINKUP)

Constituent buildup during dry weather only when snow is present on impervious surface of subcatchment (for the highlighted Landuse). For instance, if chlorides are simulated, they might only be applied for street salting when snow is present but the rate of buildup will not be a function of the amount of snow. This flag will be ignored if snowmelt is not being simulated, or no buildup is specified.

Concentration in Precipitation (JX - CONCRN)

Concentration of pollutant in the precipitation (for the highlighted landuse). All runoff, including snowmelt, is assumed to have at least this concentration. The precipitation load is always added regardless of the washoff mechanism utilized. A summary of concentrations observed in rainfall is given in the following table (Brezonik, 1975)


Typical Range of Concentration in Rainfall

Acidity (pH) 3 - 6
BOD5 mg/l 1 - 13
CODmg/l 9 - 16
TOC mg/l 1 - 3 (a)
Inorg C mg/l 0 - 2 (a)
Color PCU 5 - 10 (a)
Total Solidsmg/l 18 - 24 (a)
Suspended Solids mg/l 2 - 10 (a)
Turbidity JTU 4 - 7 (a)
Org. N mg/l 0.05 - 1.0
NH3-N mg/l 0.01 - 0.04 (a)
NO2-N mg/l 0.00 - 0.01 (a)
NO3-N mg/l 0.05 - 1.0
Total N mg/l 0.2 - 1.5
Orthophosphorus mg/l 0.0 - 0.05
Total P mg/l 0.02 - 0.15
Pesticides ug/l Few
Heavy metals ug/l Few
Leadug/l 30 - 70

(a) = data for Ft. Lauderdale (Mattraw and Sherwood, 1977)

Concentration in Groundwater (J5 - GCONC)

Concentration of the pollutant in the groundwater (for the highlighted landuse).

Street Sweeping Efficiency (JX - REFF)

Fraction of the pollutant removed by street sweeping. The effect of multiple passes must be included in the value of this parameter. Removal efficiencies from a Street Cleaner path for various street cleaning programs are provided in the following table (Pitt, 1979).

Street Cleaning

Program and Street Surface

Loading Conditions

Estimated Removal Percentage

Total Solids



Vacuum Street Cleaner

1 pass; 20-200

lb/curb mile total solids

2 passes45352237125059
3 passes53412745145968

Vacuum Street Cleaner

1 pass; 200-1000

lb/curb mile total solids

2 passes51422946175968
3 passes58473551206775
Vacuum Street Cleaner

1 pass; 1000-10000

lb/curb mile total solids

2 passes60504254257277
3 passes63524457267582
Mechanical Street Cleaner

1 pass; 180-1800

lb/curb mile total solids

2 passes75584858356071
3 passes85695969467282

Mechanical Street Cleaner

followed by a flusher



a = 15- 40 percent estimated

b = 35 -100 percent estimated

Initial Catchbasin Concentration (JX - CBFACT)

Initial concentration of pollutant within catchbasins (for the highlighted Landuse). Concentrations will be regenerated to this value during dry periods. The time to recharge concentrations is defined in the 'Typical Catchbasin' dialog under 'Water Quality' under Job Control.

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