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File:Constructed Wetland.png|thumb|700px|The following is a labelled schematic of a constructed "Free-water surface flow wetland". These types of wetlands are generally used as a BMP for stormwater treatment and are most similar to stormwater management ponds, both in function and design, the major difference being that they are shallower to allow for wetland species (i.e. macrophytes to effectively grow and biologically treat incoming flows of pollutant and suspended sediments). <span style="color:red">''A note: The following is an "image map", feel free to explore the image with your cursor and click on highlighted labels that appear to take you to corresponding pages on the Wiki.''</span>

File:Constructed Wetland.png|thumb|900px|The following is a labelled schematic of a constructed "Free-water surface flow wetland". These types of wetlands are generally used as a BMP for stormwater treatment and are most similar to stormwater management ponds, both in function and design, the major difference being that they are shallower to allow for wetland species (i.e. macrophytes to effectively grow and biologically treat incoming flows of pollutant and suspended sediments). <span style="color:red">''Explore this "image map" with your cursor and click on highlighted labels that appear to go to corresponding pages on the Wiki.''</span>

rect 16 344 196 432 [[Inlets|Inlet]]

rect 16 344 196 432 [[Inlets|Inlet]]

rect 3078 900 3949 1039 [[Natural drainage|Receiving Waterbody]]

rect 3078 900 3949 1039 [[Natural drainage|Receiving Waterbody]]

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Natural wetlands are ecosystems that have developed over time, providing diverse habitats and naturally filtering water through complex biological and physical processes. Constructed wetlands, on the other hand, are designed and built to mimic these natural functions, targeting specific water quality goals and pollutant removal. They are a cost-effective and efficient method widely used in North America to treat various wastewaters—such as stormwater, sewage, and agricultural runoff. The most significant difference between ponds and wetlands is the extent to which they incorporate shallow zones for wetland [[plants]]. A facility is normally characterized as a wetland if shallow zones (<0.5 m deep) make up more than 70 % of its volume.

[[File:Kortright-farm-june-2011.jpg|thumb|500px|Wetlands fed by stormwater at Kortright Farm, Vaughan ON]]

Wetlands can contribute to<ref>Toronto and Region Conservation Authority. 2025. Wetlands. https://trca.ca/conservation/restoration/wetlands/#:~:text=Increased%20biodiversity,as%20bird%20watching%20and%20fishing</ref><ref>Bendoricchio, G., L. Dal Cin, and J. Persson. 2000. Guidelines for free water surface wetland design. EcoSys Bd 8: 51–91. http://www.pixelrauschen.de/wet/design.pdf</ref>:

 

*Enhanced biodiversity

{{textbox|Wetlands can contribute to (TRCA, 2025; Bendoricchio, 2000)<ref>Toronto and Region Conservation Authority. 2025. Wetlands. https://trca.ca/conservation/restoration/wetlands/#:~:text=Increased%20biodiversity,as%20bird%20watching%20and%20fishing</ref><ref>Bendoricchio, G., L. Dal Cin, and J. Persson. 2000. Guidelines for free water surface wetland design. EcoSys Bd 8: 51–91. http://www.pixelrauschen.de/wet/design.pdf</ref>:

*Enhancing biodiversity

*Improving water quality and helping to meet TSS reduction targets

*Improving water quality and helping to meet TSS reduction targets

*Storing water and attenuating floods

*Storing water and attenuating floods

*Carbon sequestration<ref>Kennedy, G., and T. Mayer. 2002. Natural and Constructed Wetlands in Canada: An Overview. Water Qual. Res. J. Canada 37(2): 295–325. doi: 10.2166/wqrj.2002.020.</ref>

*Carbon sequestration (Kennedy, 2002)<ref>Kennedy, G., and T. Mayer. 2002. Natural and Constructed Wetlands in Canada: An Overview. Water Qual. Res. J. Canada 37(2): 295–325. doi: 10.2166/wqrj.2002.020.</ref>}}

 

[[LID Case Studies#Wetlands|Case studies]] are available for wetlands used in LID systems.

[[LID Case Studies#Wetlands|Case studies]] are available for wetlands used in LID systems.

==Planning considerations==

==Planning considerations==

Wetlands differ based on how water travels through the system. Free-water surface flow wetlands have water exposed on the surface, which provides excellent water quality treatment but may pose health and safety risks. Free-water surface flow wetlands are most commonly employed for stormwater treatment and are similar to [[SWM ponds]] in function and design. Sub surface flow systems provide generally lower health and safety risks and are sometimes employed to handle stormwater in combination with another wastewater stream. In horizontal sub-surface flow wetlands, water flows horizontally through a media bed, while in vertical sub-surface flow wetlands, water is introduced at the surface and percolates vertically through the media.

Constructed wetlands differ based on how water travels through the system (Grant, 2000; USEPA, 1995; Jacques Whitford Consultants, 2008)<ref name ="Grant">Grant, N., M. Moodie, and C. Weedon. 2000. Sewage Treatment Solutions. p. 35–67. In Sewage Solutions: Answering the Call of Nature. Centre for Alternative Technology Publications.</ref><ref name="EPA">United States Environmental Protection Agency. 1995. A handbook of constructed wetlands: A guide to creating wetlands for agricultural wastewater, domestic wastewater, coal mine drainage and stormwater.</ref><ref name="JW">Jacques Whitford Consultants, 2008. Constructed and engineered wetlands. p. 1-21</ref>:

*Free-water surface flow wetlands have water exposed on the surface, which provides excellent water quality treatment but may pose health and safety risks. Free-water surface flow wetlands are most commonly employed for stormwater treatment and are similar to [[SWM ponds]] in function and design. However, ponds and wetlands differ by the extent to which shallow zones for wetland [[plants]] are incorporated. A facility is normally characterized as a wet pond if shallow zones (<0.5 m deep) comprise less than 20% of its surface area, while a facility is normally characterized as a wetland if shallow zones (<0.5 m deep) make up more than 70 % of its volume. Unlike SWM ponds and constructed wetlands, [[Dry ponds|dry ponds]] are designed to temporarily store stormwater runoff and completely drain out between storm events and focus more on flood attenuation than treatment.

*Sub surface flow systems provide generally lower health and safety risks and are sometimes employed to handle stormwater in combination with another wastewater stream. In horizontal sub-surface flow wetlands, water flows horizontally through a media bed, while in vertical sub-surface flow wetlands, water is introduced at the surface and percolates vertically through the media.

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|+ Types of Constructed Wetland<ref>Grant, N., M. Moodie, and C. Weedon. 2000. Sewage Treatment Solutions. p. 35–67. In Sewage Solutions: Answering the Call of Nature. Centre for Alternative Technology Publications.</ref><ref name="EPA">United States Environmental Protection Agency. 1995. A handbook of constructed wetlands: A guide to creating wetlands for agricultural wastewater, domestic wastewater, coal mine drainage and stormwater.</ref><ref name="JW">Jacques Whitford Consultants, 2008. Constructed and engineered wetlands. p. 1-21</ref>

|+ Types of Constructed Wetland<ref name ="Grant">Grant, N., M. Moodie, and C. Weedon. 2000. Sewage Treatment Solutions. p. 35–67. In Sewage Solutions: Answering the Call of Nature. Centre for Alternative Technology Publications.</ref><ref name="EPA">United States Environmental Protection Agency. 1995. A handbook of constructed wetlands: A guide to creating wetlands for agricultural wastewater, domestic wastewater, coal mine drainage and stormwater.</ref><ref name="JW">Jacques Whitford Consultants, 2008. Constructed and engineered wetlands. p. 1-21</ref>

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!Free-water surface flow

!Free-water surface flow

===Sizing free-water===

===Sizing free-water===

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|+Design parameters for free-water surface flow wetlands <ref name="TRCA">Toronto and Region Conservation Authority (TRCA), and CH2M Hill Canada. 2018. Inspection and Maintenance Guide for Stormwater Management Ponds and Constructed Wetlands (T van Seters, L Rocha, and K Delidjakovva, Eds.). https://sustainabletechnologies.ca/app/uploads/2018/04/SWMFG2016_Guide_April-2018.pdf</ref>

|+Design parameters for free-water surface flow wetlands <ref name="TRCA">Toronto and Region Conservation Authority (TRCA), and CH2M Hill Canada. 2018. Inspection and Maintenance Guide for Stormwater Management Ponds and Constructed Wetlands (T van Seters, L Rocha, and K Delidjakovva, Eds.). https://sustainabletechnologies.ca/app/uploads/2018/04/SWMFG2016_Guide_April-2018.pdf</ref>

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===Materials===

===Materials===

*For planting recommendations, see [[Wetlands: Plants]]

*The chamber and barrel outlet [[Pipes|pipe]] should be made from reinforced concrete, rather than corrugated metal.

*[[Wetlands: Plants|Aquatic plants]] reduce flow velocity and contribute to nutrient and pollutant uptake.

*[[Plant lists|Vegetation]] such as bushes and tree planted on the perimeter and bank slope can help discourage geese and people from accessing the water.

==Performance==

==Performance==

Relative to a wet pond, a constructed wetland may offer added pollutant removal benefits due to enhanced biological uptake and the filtration effects of the vegetation.

Relative to a wet pond, a constructed wetland may offer added pollutant removal benefits due to enhanced biological uptake and the filtration effects of the vegetation.

Early stage wetlands readily sorb phosphorus onto substrates and sediments. Phosphorus removal in wetland systems is usually carried out by incorporating alum sedimentation ponds or [[sand filters]] as cells of the system, and/or by polishing wetland effluent in an iron-dosed mechanical filter.<ref name="JW">

Early stage wetlands readily sorb phosphorus onto substrates and sediments. Phosphorus removal in wetland systems is usually carried out by incorporating alum sedimentation ponds or [[sand filters]] as cells of the system, and/or by polishing wetland effluent in an iron-dosed mechanical filter (Jacques Whitford Consultants, 2008).<ref name="JW">Jacques Whitford Consultants, 2008. Constructed and engineered wetlands. p. 1-21</ref>

Freezing temperatures in winter and early spring can reduce treatment if the wetland either freezes solid or a cover of ice prevents the water from entering the wetland. If under-ice water becomes confined, water velocities may increase, thereby reducing contact times<ref name="EPA" />. Runoff in excess of maximum design flows should be [[Overflow#routing|diverted]] around the wetland to avoid excessive flows through the wetland.

Freezing temperatures in winter and early spring can reduce treatment if the wetland either freezes solid or a cover of ice prevents the water from entering the wetland. If under-ice water becomes confined, water velocities may increase, thereby reducing contact times (USEPA, 1995)<ref name="EPA" />. Runoff in excess of maximum design flows should be [[Overflow#routing|diverted]] around the wetland to avoid excessive flows through the wetland.

STEP (under previous name SWAMP) conducted their own research into the performance of stormwater wetlands, the project page and report can be viewed [https://sustainabletechnologies.ca/home/urban-runoff-green-infrastructure/conventional-stormwater-management/constructed-wetlands/performance-assessment-of-an-open-and-covered-stormwater-wetland-system-aurora-ontario/ here].

STEP (under previous name SWAMP) conducted their own research into the performance of stormwater wetlands, the project page and report can be viewed [https://sustainabletechnologies.ca/home/urban-runoff-green-infrastructure/conventional-stormwater-management/constructed-wetlands/performance-assessment-of-an-open-and-covered-stormwater-wetland-system-aurora-ontario/ here].

* Ease of access for inspections   

* Ease of access for inspections   

* Vegetation management - grass mowed to a height greater than 4–6" and clippings collected, invasive species monitoring and control   

* Vegetation management - grass mowed to a height greater than 4–6" and clippings collected, invasive species monitoring and control   

* Repair of vandalized areas

* Repair of vandalized areas

* Sediment accumulation

* Sediment accumulation measurement and removal

* Mechanical equipment check

* Mechanical equipment check - such as leaky valves

* Structural component check

* Structural component check - cracks or damage to concrete

Functional, performance, and environmental effects [[Monitoring|monitoring]] can help determine the frequency of routine maintenance and identify the need for more extensive corrective maintenance. Most major [[Inspections and maintenance#Forensic Inspection and Testing (FIT)|corrective maintenance]] for constructed wetlands fall into:

Functional, performance, and environmental effects [[Monitoring|monitoring]] can help determine the frequency of routine maintenance and identify the need for more extensive corrective maintenance. Most major [[Inspections and maintenance#Forensic Inspection and Testing (FIT)|corrective maintenance]] for constructed wetlands falls into:

* major structural repair   

* major structural repair   

* bank stabilization   

* bank stabilization   

==Gallery==

==Gallery==

{{:Wetlands: Gallery}}

{{:Wetlands: Gallery}}

==References==

==References==