A wetland is a treatment measure that is generally used for the removal of to remove fine suspended solids and associated contaminants, as well as soluble contaminants. They can also provide significant storage for a range of storm events.
In music, the USTM uses a conceptual model of a wetland system that includes two cells; an inlet pond followed by the main wetland or macrophyte cell. Stormwater can bypass the whole system , when it falls below ("Low Flow Bypass") or exceeds ("High Flow Bypass") the predefined flow rates. The macrophyte cell has a permanent volume of water, with a low flow outlet pipe, whose invert is notionally set at the standing water level of this permanent pool. An overflow weir is located at an elevation equal to the extended detention depth above the standing water level of the permanent pool. A conceptual diagram of the wetland properties in music is presented below.
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The Inlet Properties define the physical characteristics of the inlet pond of the wetland system. It is assumed in the model configuration for a wetland that the macrophyte cell is preceded by a separate inlet pond. Flow is hydrologically routed through the wetland based on the characteristics defined by the user.
Low Flow Bypass
All of the stormwater that approaches the wetland below the user-defined Low Flow Bypass amount will bypass the wetland. Any flow above the Low Flow Bypass (subject to the presence of a High Flow Bypass) will enter and be treated by the wetland.
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When the stormwater inflow rate exceeds the user-defined High Flow Bypass amount, only a flow rate equal to the High Bypass Flow (less that than specified in any Low Flow Bypass) will enter and be treated by the wetland. All of the stormwater flow in excess of the High Flow Bypass amount will bypass the wetland and will not be treated by the wetland.
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The inlet pond volume in wetland systems provides a pre-treatment of the stormwater prior to its discharge into the macrophyte cell of the wetland. Pre-treatment of stormwater discharging into the wetland includes sedimentation of coarse to medium-sized particles and hydrologic control by facilitating a by-pass of flow around the macrophyte zone when the water level in the macrophyte zone has reached its maximum extended detention depth. music Music models the performance of these pre-treatment functions using the inlet pond volume, assumed to be a permanent pool and defined, as the principal parameter. Estimate inlet pond volume feature has not been offered at this stage.
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