Constructed Wetlands

Successful Constructed Wetlands

Constructed Wetlands

Constructed wetland projects can be separated into 3 categories:

  1. Construction of a new wetland to harvest, store and treat storm water run-off. Almost all new sub-division developments will require a system to harvest storm water for storage and treatment prior to the water entering natural rivers, creeks and estuaries. These systems are designed by engineers and in most cases constructed by civil contractors to specification.
  2. Restoration of an existing natural wetland. These existing wetlands are re-established after disturbance by development and/or other activities. This may involve simple remedial planting to supplement existing vegetation, to a complete re-vegetating of a degraded site using endemic species. Bluedale can undertake site visits to identify plants and assist with plant species selection for fresh and saline water wetlands.
  3. Sewage Treatment Plant.  Many modern sewage treatment plants use wetland systems in the final stage of grey water treatment. These systems are large or small depending on the size of the sewage treatment plant (STP). An example is West Byron STP, in Byron Bay NSW which has a number of cells covering many hectares.

Guidelines for successful wetland planting:

Wetlands are either planted-out on-line or off-line.

Online: the wetland will have water in the basins that cannot be drained and refilled easily, often these are existing water bodies that are part of the natural environment.

Off-line: the wetland can have the water diverted during construction, planting and maintenance and refilled once finished. These are usually new constructions that will have water flow and water level control weirs.

Following is a blueprint for the successful planting of each system. Each requires a different planting process.

On-line Wetlands

Planting on-line wetlands is a simple procedure - the following 7 steps will guide you through the process.

  1. ORDER YOUR PLANTS IN ADVANCE. If possible give yourself at least 8 weeks lead time. The longer the lead time the taller the plants can be grown, this will make a huge difference when planting into an existing body of water.
  2. Remove all weeds from the site prior to planting. This will give your project the best possible start.
  3. Optional: If the water in the basin is turbid, (cloudy), use Aluminum sulfate, (alum), as per directions, to clear the water, this can help the plants to establish, by allowing additional light for photosynthesis.
  4. If the wetland has a water level control weir, set the weir so that a stable water level can be maintained during the plant establishment period, usually 4 to 8 weeks.
  5. Predation by water birds has been known to cause damage to young plants. Observation of bird activity prior to planting should indicate whether precautions are needed.If water birds are a potential problem, the use netting or wire cages to cover the young plants has proven successful. Providing an alternate food source away from the site has also been effective.
  6. Now you are ready to plant. Firstly set-out the plants according to their planting zones, (see habitat zones diagram for details). Edge plants should be planted between the high and low water marks. Plants that grow in water should be planted no deeper than 2/3 the height of the plant foliage. Make sure to anchor the root ball of the plant by planting firmly into the substrate of the basin.
  7. Monitor the site over the coming weeks for signs of bird predation and plant dislodgement. Protect and replant as needed until established, usually 4 to 8 weeks (season dependent).

Off-line Wetlands

Planting off-line wetlands is also a simple procedure - the following 7 steps will guide you through the process.

  1. ORDER YOUR PLANTS IN ADVANCE.  Again, if possible give yourself at least 8 weeks lead time. The longer the lead time the more mature and taller your plants will be, this will make a huge difference to the success of your planting.
  2. Remove all weeds from the site prior to planting. This will give your project the best possible start.
  3. Off-line wetlands are often dry basins, so it will be vital to know the final water depths so that each habitat zone will have the correct plant species. Mark the different zones with stakes. If the wetland already contains water, mark the planting zones prior to removing the water for planting.
  4. With the water removed you are ready to plant. Firstly set-out the plants according to their planting zones, (see habitat zones below). Edge plants should be planted between the high and low water marks, water plants according to their planting zones. When planting make sure to anchor the root ball of the plant by planting it firmly into the substrate of the basin.
  5. If the wetland has a water level control weir, set the weir so that a stable water level can be maintained, the water should be no deeper than 2/3 the foliage height of the plants in the deepest zone. As the plants increase in height the water level can be progressively raised until full. 
  6. Again, observe bird activity prior to planting, and take measures as outlined above.
  7. If the water hasn’t been returned to the basin, irrigating the plants will be necessary until the basin has water again. Monitor the planting over the coming weeks for signs of bird predation and plant dislodgement. Protect and replant as needed until established.

Easy Care Maintenance of Constructed Wetlands.

  1. Ensure that water levels are monitored and maintained during establishment period.
  2. Seasonal drying of the wetland will mimic a natural system and allow for easy maintenance.
  3. Use bird protection measures when establishing young plants. Remove when established.
  4. Replace any failed plants, if needed. Generally this is rarely necessary.
  5. Remove any undesirable plants or weeds throughout the maintenance period.