Aquatic vegetation management

News Update 25 October 2017

The City’s Environmental Management team regularly monitor the City's lakes and waterbodies for the presence of aquatic weeds.

Aquatic vegetation growth severity and frequency are only mitigated by controlling the nutrient supply to the waterbody. The City has incorporated Water Sensitive Urban Design principles and features at Doneraile Reserve and Bodkin Park in Waterford with plans for Neil McDougal Park in Como for 2018, however the success will be influenced by the quantity of nutrients flowing into the water bodies from the catchment area.

Lemna (Duckweed)
Lemna disperma is a native free floating annual herb occurring in still freshwater lakes in the City, belonging to the Lemnaceae family which are the smallest flowering plants existing. They have very rapid growth under the right conditions – high nutrients (nitrogen and phosphorous) and warm weather and can quickly cover the surface of a waterbody. 

Algae is a small aquatic organism containing chlorophyll and produce energy from the sun and feed off nutrients in waterbodies. The most common algae in the City is filament forming green or brown algae which occur in lakes and waterbodies as well as the Swan and Canning Rivers. Blooms occur in the warmer weather and are a result of high nutrients in the water body. Generally the species which occur in lakes and wetlands within the City are non-toxic and not harmful to human or domestic animal health, however it is recommended that all algae is treated as potentially irritative just like you would treat most plants.

Benefits of Aquatic vegetation
As lemna and algae proliferate they remove nutrients from the water body and provide habitat and provides a food source and habitat for birds, fish and turtles as well as invertebrate species. The lemna cover also keeps the waterbody cool and suppresses algal blooms.

How you can help
Everyone can work toward reducing excess nutrients and pollution from entering waterbodies by: 
• Pick up animal droppings from lawns and parks and place them in bins provided. 
• Please do not feed native wildlife. This can increase faecal waste which affects the water quality. It can also be harmful to native wildlife. 
• Always place unwanted garden waste in a green waste bin, take it to the City's Recycling Centre or use it as mulch or compost for your home garden as opposed to fertilisers. Never dispose of green waste in or near a water body. 
• Wash your car, boat or caravan on the lawn as opposed to on the street or in the driveway and use phosphorus free detergents. This prevents chemicals and excess nutrients from entering waterways through the stormwater system. 
• Use fertilisers in moderation and follow the instructions carefully or seek alternatives. For more information visit

To find out more visit the Environment page of the City's website.

Useful links
How you can help
Fertilise wise

Contact us

For more information, please contact the City.