Water quality update

The City is continuing to monitor water quality and midge activity across Lake Brearley, Lake Bungana and Brickworks Lake.

Monitoring undertaken on 30 July has provided further information about current water quality conditions.

While the algaecide and Phoslock treatments undertaken in March have significantly improved water quality, Maylands Lakes remains a highly modified urban lake system where periodic algal blooms can occur when environmental conditions are favourable.

To reduce the frequency and severity of these events over the longer term, the City is continuing to implement the Council-endorsed Maylands Lakes Environmental Restoration Masterplan.

Lake Brearley algae

Recent monitoring results indicate the bloom in Lake Brearley is predominantly green algae, rather than cyanobacteria that has affected the lake in previous years.

Following the algaecide and Phoslock treatments in March, water clarity in Lake Brearley has improved significantly and cyanobacteria levels have substantially reduced. However, other algae remains present in the lake.

The improved water clarity means more sunlight is now able to penetrate the water column. Combined with nutrients entering the lake following recent rainfall, nutrients associated with bird activity and suitable water temperatures, conditions have remained favourable for some algae to grow.

The visible algae is currently concentrated in areas where wind pushes floating material towards the shoreline, causing it to accumulate as a surface film or scum.

This highlights the difference between Lake Brearley and Lake Bungana. Extensive submerged aquatic vegetation has established throughout Lake Bungana and is helping take up available nutrients and reduce their availability to algae.

Establishing aquatic vegetation within Lake Brearley is therefore an important part of the City's longer-term restoration program.

At this stage, the visible bloom does not appear to represent a return of the significant cyanobacterial blooms experienced in previous years.

The City will continue to monitor conditions and assess options to disperse surface build-up following the recent wet weather.

Midge monitoring and treatment

Monitoring and observations have identified an increase in midge activity around parts of Maylands Lakes.

While there has been an increase in midge swarms, overall numbers remain significantly lower than in previous years.

In response to the increase, the lakes were treated in July with a higher concentration of larvicide, in accordance with the City’s Australian Pesticides and Veterinary Medicines Authority (APVMA) off label permit. Previous APVMA treatments have generally resulted in reduced midge numbers in the weeks following treatment.

The City will continue to monitor midge numbers to assess the effectiveness of the July treatment and adjust its management response as required.

Next steps

The City will continue to monitor water quality, algae and midge numbers across Maylands Lakes, with the latest monitoring results published on Engage Bayswater.

Longer-term restoration works are progressing, including aquatic planting within Lake Brearley expected in spring, construction of the Brickworks Lake biofilter and installation of a pump system in Lake Brearley.

These works are designed to help manage nutrients entering and circulating in the lake system, while improving water quality and building the lakes' resilience over the longer term.