Constructed stormwater wetland design for the dry and wet tropics

P. Breen, K. Markwell, G. Walsh, C. Henderson

Research output: Chapter in Book/Report/Conference proceedingConference PaperResearchpeer-review

Abstract

Constructed wetlands are commonly used for stormwater treatment in South-East Australia. Their treatment efficiency relies on sustaining aquatic macrophytes throughout the year. The use of wetlands in Australia's dry and wet tropic areas has been met with some reluctance due to uncertainty as to whether the aquatic macrophytes can persist through the dry season. A design process was undertaken to adapt constructed wetland designs for use in the dry and wet tropics. Local aquatic macrophyte species tolerant of deep inundation and seasonal drying were identified. The wetland bathymetry was modified to accommodate the expected hydrology. A wetland spreadsheet model was built incorporating rainfall, runoff and evaporation and different designs were tested until the adapted design did not experience dry periods longer than 70 days. The final designs incorporate deep macrophyte zones up to 800mm deep (NWL). The deep macrophyte zones allow the plants to persist through the dry season. This approach ensured a viable treatment system could be in operation at the start of the wet season when runoff quality was worst. Deep permanent pools (2m) were included as refugia for mosquito predators. Modelling revealed that sporadic winter rainfall events provide sufficient water to allow perennial emergent macrophytes to persist through the dry season and to "top-up" refuge pools. The ability of these adapted constructed stormwater wetland systems to sustain their treatment efficiency and also their landscape and aesthetic appeal throughout the year should help to promote the use of these treatment systems within Australia's dry and wet tropics. Constructed wetlands are commonly used for stormwater treatment in South-East Australia. Their treatment efficiency relies on sustaining aquatic macrophytes throughout the year. The use of wetlands in Australia's dry and wet tropic areas has been met with some reluctance due to uncertainty as to whether the aquatic macrophytes can persist through the dry season. A design process was undertaken to adapt constructed wetland designs for use in the dry and wet tropics. Local aquatic macrophyte species tolerant of deep inundation and seasonal drying were identified. The wetland bathymetry was modified to accommodate the expected hydrology. A wetland spreadsheet model was built incorporating rainfall, runoff and evaporation and different designs were tested until the adapted design did not experience dry periods longer than 70 days. The final designs incorporate deep macrophyte zones up to 800mm deep (NWL). The deep macrophyte zones allow the plants to persist through the dry season. This approach ensured a viable treatment system could be in operation at the start of the wet season when runoff quality was worst. Deep permanent pools (2m) were included as refugia for mosquito predators. Modelling revealed that sporadic winter rainfall events provide sufficient water to allow perennial emergent macrophytes to persist through the dry season and to "top-up" refuge pools. The ability of these adapted constructed stormwater wetland systems to sustain their treatment efficiency and also their landscape and aesthetic appeal throughout the year should help to promote the use of these treatment systems within Australia's dry and wet tropics.

Original languageEnglish
Title of host publicationWSUD 2012 - 7th International Conference on Water Sensitive Urban Design
Subtitle of host publicationBuilding the Water Sensitive Community, Final Program and Abstract Book
Publication statusPublished - 14 Jun 2012
Externally publishedYes
EventInternational Conference on Water Sensitive Urban Design 2012: Building the Water Sensitive Community - Melbourne Cricket Ground, Melbourne, Australia
Duration: 21 Feb 201223 Feb 2012
Conference number: 7th
http://www.wsud2012.com

Publication series

NameWSUD 2012 - 7th International Conference on Water Sensitive Urban Design: Building the Water Sensitive Community, Final Program and Abstract Book

Conference

ConferenceInternational Conference on Water Sensitive Urban Design 2012
Abbreviated titleWSUD Conference 2012
Country/TerritoryAustralia
CityMelbourne
Period21/02/1223/02/12
Internet address

Keywords

  • Constructed wetlands
  • Dry and wet tropics
  • Stormwater treatment

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