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MUSIC models the infiltration system by taking into account infiltration through both the base and sides of the system (unlike MUSIC v3 which assumed that infiltration occurred only through the base). It is important to note that there is no option to include lining of the base of the infiltration system. However, you can take into account lined walls, by subtracting them from the specified Infiltration Media Perimeter specified in MUSIC.Treatment in the infiltration system is assumed to occur only in the ponding (extended detention) zone; no treatment is modelled in the infiltration media. Whilst this is not strictly true, it must be remembered that MUSIC ‘loses’ water that is infiltrated and so there is no benefit in modelling the treatment performance further.
A conceptual diagram of the infiltration system properties in MUSIC is presented below:
Conceptual diagram of infiltration system properties.
Infiltration System Properties
The infiltration system properties dialogue box contains the parameters that describe the basic physical characteristics of the infiltration system. A description of each of the parameters is given below.
A conceptual diagram of the infiltration system properties in MUSIC is presented below:
Conceptual diagram of infiltration system properties.
Inlet Properties
The Inlet Properties define the physical characteristics of the inlet section of the infiltration system.
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When the stormwater inflow rate exceeds the user-defined High Flow Bypass amount (in units of m3/s), only a flow rate equal to the High Flow Bypass (less that specified in any Low Flow Bypass) will enter and be treated by the infiltration system. All of the stormwater flow in excess of the High Flow Bypass amount will bypass the infiltration system and will not be treated.
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Storage Properties
The Storage Properties define the physical characteristics of the surface storage above the infiltration medium the infiltration system.
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A reporting window will then be presented showing the water balances for various inflows and outflows at the infiltration systems as shown below.
It is possible to view or save various flows and water quality as below for the infiltration system:
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The advanced properties section (opened using the Advanced Tab under Infiltration System) displays the parameters that describe the hydraulic characteristics for the overflow weir, and the parameters that describe the treatment process in the infiltration system.
Weir Coefficient
The overflow weir carries a discharge when the water level in the infiltration system pond exceeds the Extended Detention Depth. The overflow weir is modelled as a sharp broad crested weir whose discharge equation is given by:
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For details on CSTR cells, refer to Number of CSTR Cells. For infiltration systems:
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MUSIC models the influence of infiltration through the sides of the system. This is important, since a number of studies have shown that this can represent a very high proportion of the total infiltration of the system. MUSIC has been calibrated for a number of infiltration systems, both in the field and using detailed laboratory studies, to derive a default Horizontal Flow Coefficient of 3.0 (ie. the lateral infiltration rate being effectively three times the rate of vertical infiltration through the base). You should only modify this value where they have appropriate data to calibrate it; these data should preferably be based on published, peer reviewed studies.
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NOTE: Advanced Properties are uneditable by default. You can make it editable for each project by clicking on Edit and Project Options. This will present you with a Project Options Screen as displayed below:
Now, click on MUSICX Treatment Node Settings and tick on Editable as shown above. |
