Neil McDougall Park lake

Journalist’s enquiry: A reader contacted us (The Southern Gazette) regarding the lake in Neil McDougall Park, Como – the photo is attached. The image was sent to us around two weeks ago, but could I chase an update from City of South Perth on the lake?

• Why is the lake currently in this state?
• What has been done to rectify, if this is considered an issue?
• What will City of South Perth do in the future regarding this matter?

Please attribute all quotes to City of South Perth Mayor Sue Doherty

The growth on Neil McDougall Park lake is an aquatic plant species Lemna minor, commonly known as duckweed. The lake historically has duckweed annually at this time of the year. It is not algae, it occurs naturally and it is not harmful to wildlife or people. 

The growth of duckweed is related to high nutrient levels in the lake. The lake is a receiving water body for stormwater in the area and picks up nutrients from the surrounding catchment area. These nutrients are then deposited into the lake. The duckweed feeds off this nutrient and coupled with warm weather conditions it flourishes. It tends to reduce in density as the weather cools over autumn and winter. It is not a mat forming plant, rather it moves around the lake with wind and wildlife movement.

The City’s environment team monitor the occurrence and density of duckweed in Neil McDougall Park lake on a regular basis. An upgrade is planned for the lake in 2019 to retrofit all inlets that feed into the lake with a range of Water Sensitive Urban Design features to help to reduce nutrients before they enter the lake.