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Water Quality Parameter Dialogue Boxes
The third, fourth and fifthe dialog boxes contain the water quality parameters used in the generation of pollutants from the source node. Each dialog box is devoted to one of the pollutants modelled:
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There are different tabs as Total Suspended Solids, Total Phosphorus and Total Nitrogen for modelling these pollutants.
The pollutants are generated as concentrations in mg/L, and can be defined for both the storm flow and base flow components of runoff generated from the rainfall runoff model.
Tip Box
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The default values displayed for Mean and Standard Deviation (Std Dev) for both base flow and storm flow (Table 1) are adapted from a range of sources, particularly Duncan (1999) and are discussed in more detail in Urban Runoff Generation. Wherever possible, these values have been modified in the MUSIC6.ini file to be representative of the region in which MUSIC is being applied.
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You can modify the pollutant concentrations as desired, by changing the values displayed in the Mean and Std Dev boxes.
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Land Use/
SurfaceZoning Types
For Urban For source nodes, each land use/zoning /surface type has appropriate base flow and storm flow pollutant concentrations for that zoning (eg. rural residential) or surface type (eg, sealed roads, unsealed roads). The selection of Land Use/Zoning /Surface Type is selected on Page 1 of the Wizard, and on Source Tab changes the default values displayed on pages 3, 4 and 5Total Suspended Solids, Total Phosphorous and Total Nitrogen Tabs. Prior to MUSIC version 6.2, MUSIC had three source nodes, Urban, Agricultural and Forest. The 'mixed' Zoning/Surface type contains the same pollutant concentration parameters as the prior default 'Urban' values. For all other Zoning/Surface types, the pollutant concentration parameters are Sydney Catchment Authority (2012).
Table 1. Default pollutant concentrations for each source node
Source Node Type | Zoning/Surface Type | Pollutant Concentration (log mg/L) | |||||||||||
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Total Suspended Solids | Total Phosphorus | Total Nitrogen | |||||||||||
Base Flow | Storm Flow | Base Flow | Storm Flow | Base | Storm | ||||||||
Mean | Std Dev | Mean | Std Dev | Mean | Std Dev | Mean | Std Dev | Mean | Std Dev | Mean | Std Dev | ||
Agricultural | - | 1.40 | 0.13 | 2.30 | 0.31 | -0.88 | 0.13 | -0.27 | 0.30 | 0.074 | 0.130 | 0.59 | 0.26 |
Forest | - | 0.90 | 0.13 | 1.90 | 0.20 | -1.50 | 0.13 | -1.10 | 0.22 | -0.14 | 0.13 | -0.075 | 0.240 |
Urban | Mixed | 1.10 | 0.17 | 2.20 | 0.32 | -8.20 | 0.19 | -0.45 | 0.25 | 0.32 | 0.12 | 0.42 | 0.19 |
Roof | 1.10 | 0.17 | 1.30 | 0.32 | -8.20 | 0.19 | -0.89 | 0.25 | 0.32 | 0.12 | 0.30 | 0.19 | |
Sealed Road | 1.20 | 0.17 | 2.43 | 0.32 | -8.50 | 0.19 | -0.30 | 0.25 | 0.11 | 0.12 | 0.34 | 0.19 | |
Unsealed road | 1.20 | 0.17 | 3.00 | 0.32 | -8.50 | 0.19 | -0.30 | 0.25 | 0.11 | 0.12 | 0.34 | 0.19 | |
Eroding gullies | 1.20 | 0.17 | 3.00 | 0.32 | -8.50 | 0.19 | -0.30 | 0.25 | 0.11 | 0.12 | 0.34 | 0.19 | |
Revegetated land | 1.15 | 0.17 | 1.95 | 0.32 | -1.22 | 0.19 | -0.66 | 0.25 | -0.05 | 0.12 | 0.30 | 0.19 | |
Quarries | 1.20 | 0.17 | 3.00 | 0.32 | -0.85 | 0.19 | -0.30 | 0.25 | 0.11 | 0.12 | 0.34 | 0.19 | |
Residential | 1.20 | 0.17 | 2.15 | 0.32 | -0.85 | 0.19 | -0.60 | 0.25 | 0.11 | 0.12 | 0.30 | 0.19 | |
Commercial | 1.20 | 0.17 | 2.15 | 0.32 | -0.85 | 0.19 | -0.60 | 0.25 | 0.11 | 0.12 | 0.30 | 0.19 | |
Industrial | 1.20 | 0.17 | 2.15 | 0.32 | -0.85 | 0.19 | -0.60 | 0.25 | 0.11 | 0.12 | 0.30 | 0.19 | |
Rural residential | 1.15 | 0.17 | 1.95 | 0.32 | -1.22 | 0.19 | -0.66 | 0.25 | -0.05 | 0.12 | 0.30 | 0.19 |
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Tip BoxThe default urban parameters were the basis for guidelines such as the Victoria Stormwater Committee (1999) BPEM Guidelines : Stormwater. It is generally recommended that these are adopted when modelling for the purposes of demonstrating compliance with this guideline. This is because using other landuse/surface types will result in larger/smaller treatment systems being required. The percentage reductions set in the guidelines combined with the 'diminishing returns' effect as concentrations decrease mean that if the starting point concentrations are lower, treatment to a percentage reduction will be harder to achieve and the required treatment size will be larger. Conversely, higher concentrations will typically require a smaller treatment system. |
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Tip BoxThe Mean and Standard Deviation values displayed in the text boxes are displayed as the Log of the concentration in mg/L. Concentrations in the normal domain are displayed on the schematic distribution graphs on the dialogue box. |
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There are two options available for defining pollutant concentration in both the surface and baseflow components of the runoff:
- Mean: A constant value set at the value displayed in the Mean text box; or
- Stochastically Generated: A stochastically generated concentration whose mean and standard deviation will be consistent with those displayed in the Mean and Standard Deviation text boxes.
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Tip BoxChanging the Mean and Std Dev of the Log concentrations in the text boxes will change the corresponding concentration values displayed on the accompanying graph. |
When using the Stochastically generated option, the concentration at each time-step will be regenerated using a stochastic model that reproduces the mean and standard deviation of the log values displayed in the text boxes.
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A review of instantaneous water quality data has been undertaken to examine the ‘cross-correlation’ between pollutant concentrations, under both baseflow and stormflow conditions. No significant correlations were found during baseflow, however in urban catchments, a strong correlation can exist between TSS and TP during stormflow. In previous versions of music, this correlation was hard-wired, however in Version 4 and above of music, this has been removed to allow greater flexibility in the configuring of constituents.
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It is important to note that the autocorrelation coefficient will not significantly affect the treatment train effectiveness produced by music, but simply ensures that the variation over time in concentrations during storm events and baseflow conditions is more ‘realistic’. Depending on the time-step and coefficient used, there can be variations in mean annual loads for the same model run on different computers, however the maximum difference is usually within 10% of the previous run.
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Tip BoxSerial correlation (also called autocorrelation) is the correlation between pollutant concentration at time t, and the previous time-step, t-1. music does not model autocorrelation for lag periods of more than one time-step. |
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