Treatment MeasuresWetlands : the Wetland 'Zones'

Functionally, wetlands are divided into three zones, namely, the inlet zone, macrophyte (plant) zone and the open water zone.

Inlet zone:

Energy Dissipation and Sedimentation

This is a transitional zone between the waterways draining the catchment and the wetland . The purpose of this zone is to reduce the velocity of the inflowing water and to enable the larger particles (such as sedimnet/clays) to settle and sink. Aquatic plants can also be grown in the edges of this area as they will generally be able to withstand high velocity inflows during severe storm events.

Inlet zone

This Zone can be constructed using varying methods and is not restricted to small sedimentation water bodies. This zone although a necessity for constructed wetlands in developed regions, can be omitted through the use of various primary and secondary treatment measures in newly (proposed) constructed developments. An example is the use of swale drains and bioretention systems. (See Main Menu options).

Macrophyte / Ephemeral zone:

Leaf / Organic matter trap

This area is usually occupied by emergent and submerged aquatic plants. The plants and micro-organisms on their stems plus the sediments in which these plants grow, take up or convert the nutrients and assist in the treatment of stormwater.

Macrophyte / Ephemeral zone

Open water / Wetland zone:

Fine particulate and dissolved contaminant retention

This is a deeper area that allows time for finer particles to settle and sink to the bed, plus allowing sunlight to kill bacteria. Due to sunlight and nutrient availability, periodic algal growth may also occur in this zone, which will also trap dissolved nutrients and allow them to either enter the food chain or settle to the bottom of the pond.

Open water / Wetland zone

Currently small lakes have been used to fill this requirement. The open water body enables sunlight to penetrate into various layers of the water thus driving many reactions that serve to remove pollutants (eg. Dissolved nutrients) and give time for the finest particles to settle out of the waters.