Neil McDougall Lake
Like many other wetlands and lakes across the Perth metropolitan area, Neil McDougall Lake experiences an almost yearly reccurrence of a dense Lemna (duckweed) mat that covers the lake. Blue-green algae blooms are also noted at the Lake when naturally occurring blue-green algae multiply quickly and dominate the water column.
A sustainable solution
The City is investigating a long-term, sustainable solution for the management of the duckweed and blue-green algae blooms.
The lake has significant environmental values and is visited by a variety of birds including the Western Swamp Hen, Pacific Black Duck, Eurasian Coot and Black Swan, as well as the Western long-necked tortoise, and the surrounding parkland is home to numerous passerines and small native Fauna.
Neil McDougall Lake acts as an infiltration basin and receives stormwater from four catchments, resulting in excess nutrients and organic loading entering the lake. High level of nutrients promotes algal blooms and low oxygen conditions, which in turn stress aquatic organisms. Other contaminants, such as heavy metals, also enter the lake through the drainage network and together with nutrients accumulate in the sediment. These can be released into the water column and enter the food chain.
The lake is shallow and has no outflow to promote flushing. As such there is an insufficient water movement to disrupt the blue-green algae growth cycle or to allow fringing vegetation to filter and remove nutrients.
Poor water movement and stagnation also lead to high temperatures in the water column in summer, which is one of the main factors fostering algal blooms.
An integrated remediation solution has been designed to address the processes driving the algae and duckweed blooms. This system addresses the continual inputs of polluted stormwater and poor lake circulation and is designed to operate with minimum maintenance requirements.
The system will also provide a range of additional benefits such as:
- Biodiversity enhancement and increased resilience
- Enhancement of the landscape and amenity values of the lake and surrounds
- Provision for nesting and shelters for native birds and animals
- Opportunities for environmental education.
In March 2019 the community were invited to provide feedback on the preliminary water sensitive urban design.
A feedback and outcomes report is available on Your Say South Perth. The design was updated taking on board the feedback along with the outcomes of environmental studies.
The design has now been finalised and design was completed mid 2020.
In early 2021 the City secured funds from the Local Roads and Community Infrastructure Grant funding for implementation of the construction of stage 1. Stage 1 construction is anticipated to commence in early 2022 subject to procurement.
Neil McDougall lake shows signs of recovery
Extensive environmental restoration work completed in 2022 at Neil McDougall Park has already had a positive effect on water quality at the lake and overall health of the wetlands.
The recent summer showed a noticeable reduction in duckweed growth and algal blooms that have affected the lake for more than two decades due to a drying climate and increased nutrient levels, such as nitrogen and phosphorous, which can upset the natural balance of ecosystems.
Mayor Greg Milner said it was great to see such significant improvement following the City’s $1.3 million remediation project, which was almost fully funded by a Local Roads and Community Infrastructure Program grant from the Australian Government.
“Neil McDougall Park currently receives stormwater from four catchments and provides habitat for several bird species and the western long-neck or Oblong turtle, so this work has not only improved the lake’s aesthetics, it will also benefit habitat for our local wildlife,” the Mayor said.
“For decades, the lake at this much-loved park has been choked each summer with duckweed and algal blooms. The work we have done will help ensure that Neil McDougall Park Lake remains healthy and beautiful all year round.”
Federal Member for Swan Zaneta Mascarenhas said: “I’m thrilled to see Neil McDougall Park thriving after the remediation work to restore lake water quality.
“Locals love our native water birds – healthy wetlands are critical to ensure that they are here for future generations. This is a great example of the importance of our wetlands for water quality.”
The City partnered with Syrinx Environmental to develop a range of water sensitive urban design features including construction of sedimentation zones, vegetated filtration zones and a treatment wetland for stormwater inflows and re-circulated lake water.
Syrinx Environmental even custom-designed a pollutant trap to help keep debris out of the wetlands.
Further remediation works are planned at the Henley Street end of the park. For updates or more information, please see our Environmental Projects page.
Image (L-R): Federal Member for Swan Zaneta Mascarenhas with some of the City's Neil McDougall Park project team – Construction Projects Officer Ryan Smith, Acting Parks Coordinator Paul Reed, Environment Coordinator Yulia Volobueva – and Mayor Greg Milner.
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