Forest Lake Management Plan

Brisbane City Council is implementing long-term solutions as part of the Forest Lake Management Plan to improve the health of Forest Lake for the community and the environment.

Brisbane’s natural environment makes our city one of Australia’s best places to live, work and relax. It’s important that we continue to work together to protect our waterways to ensure future generations can enjoy them.

Council is implementing a long-term plan to combat the ongoing issues that contribute to algae blooms in Forest Lake. This plan is in addition to a range of other measures Council continues to employ to improve the overall health of the lake.

Project summary

This table provides summary information about the Forest Lake management plan including address, ward, project outcomes and latest update.
Address The Lake Parklands, Forest Lake
Ward Forest Lake
Project outcomes To reduce algae blooms in Forest Lake and improve the health of the lake's ecosystem
Latest update Stage 2 commencing late August 2021

Project background

A number of environmental issues have affected the lake over the last few years, including the following.

  • High nutrient levels in the lake have led to blooms of various algae types. Blue-green algae growth, in particular, can cause skin and eye irritations for people and pets touching the water, as well as emitting a strong, musty odour. Other algae types detected in the lake are not dangerous to humans or pets and are a part of normal lake ecological processes.
  • Rapid growth and coverage of the water weed, Salvinia. This plant can die off and sink to the bottom of the lake, reducing dissolved oxygen levels, resulting in reduced oxygen levels for fish and aquatic species to breathe.
  • The large ibis population on Bird Island and other areas around the lake have led to odour issues and high nutrient levels in the lake.

Unfortunately, solving these environmental issues cannot be done quickly. Rebalancing the lake's ecosystem will require implementing a range of solutions over a period of time, along with ongoing monitoring schedules and maintenance activities.

Previous lake management activities

Council has already taken action to improve the lake's health and the benefits can be seen in the improvement of the lake's general water quality and reduction in algae blooms. Council's actions are listed below.

  • Managing the ibis through egg and nest management, and by removing specific vegetation types to deter ibis from the lake. The number of ibis roosting at Forest Lake has been regularly monitored. In July 2021, there were 90 ibis roosting, and no nests or eggs were detected. This is a decrease from the highest counts of ibis of approximately 469 in 2018, demonstrating the measures continue to effectively deter ibis from Forest Lake. Overall, this will benefit the health of the lake by decreasing the unwanted nutrients they bring to the lake through their droppings.
  • The ongoing Salvinia harvesting works at the lake. The Salvinia provided an interim solution to reducing the high nutrient levels in the lake until the first round of native plants were established in the lake in late 2020. While the harvesting works continue to be successful, it is unlikely Salvinia will ever be completely eradicated from the lake. This is due to the presence of Salvinia upstream and the natural dispersal of the plant that occurs with the movement of birds between water bodies. Council remains committed to proactively monitoring and managing blooms of Salvinia as they occur.
  • The completed rehabilitation works near Seabrook Crescent included desilting the inlet, minor tree removal, and revegetation work. This improved the hydraulic drainage of the creek.
  • Tree and vegetation management in the lake parklands. Council removed some trees that had died or that were leaning over private properties. Over 100 trees will be planted in the next year. Some of these will be located around the lake to help shade and cool the water, and others will be planted in the park area.

General maintenance and routine inspections will continue at the lake, which include:

  • continuing the successful ibis management plan
  • testing and analysis of the lake water quality which allows Council to monitor ongoing conditions and implement appropriate actions where required
  • treating weeds around the lake
  • collecting litter
  • clearing silt traps
  • monitoring and managing any changes to the lake environment.

Revised approach

The Forest Lake Management Plan is being implemented in a revised three-stage approach which allows for planting and desilting to occur at the most favourable times of the year for these activities.

This three-part timeline shows the new staged approach.

Stage

Planting

LATE 2020

Approximately 30,000 native aquatic plants were added to the lake in areas where desilting will not occur. These plants will improve the health of the lake during the summer months by reducing the nutrient levels available for algae to grow.

Stage

Desilting

MID-2021

This work will take place in two inlet areas of the lake to reduce the sediment loads and levels of nitrogen and phosphorus available for algae growth. Council has obtained the Queensland Government permit required to undertake the desilting works in this environment.

Stage

Additional planting

late-2021

Approximately 70,000 plants will be added to the lake following the desilting works in mid-2021 to help mitigate high nutrient levels and create a more 'plant' based lake system.

Stage three works will allow for the newly desilted areas to be freshly planted to reintroduce a more 'plant' based lake system.

Project update

Stage one of the newly revised approach was successfully completed in late 2020. The new plants were left to mature while Council continued to manage the water levels to ensure the plants had fresh air to breathe. While some plant loss occurred as a result of the new plants proving to be an attractive food source and nesting material for local bird life, Council is working with the expert working group and the planting contractor to implement a range of measures that will mitigate current losses and protect future planting works. Since then, Council has continued to manage any Salvinia outbreaks and maintain weed control measures.

Stage two of the works will involve removing sediment from the lake in accordance with strict environmental and workplace health and safety guidelines. The desilting work will be undertaken using a dredging methodology and will take 2-4 weeks to complete. Council is pleased to advise there is no requirement to reduce the water level to complete the desilting work.

Stage three of works is anticipated to start in September 2021, prior to the wet season beginning. In consultation with the expert working group, planting efforts will be significantly increased to see 70,000 new plants established in the lake. This strategy is based on the positive results achieved by stage one planting works, the lower than expected silt levels, and the understanding that an increased volume of aquatic plants will have the ability to consume larger quantities of nutrients from the water to mitigate future algae blooms. To undertake the planting, the lake's water level will be reduced by approximately 400 millimetres. As the plants mature, Council will continue to manage the water levels to ensure the plants have access to fresh air until they reach maturity, at which point the lake will be allowed to refill again.

Following the completion of stage three, Council will continue to monitor the lake as part of Brisbane's Total Water Cycle Management Plan. While every care has been taken in the development and implementation of the Forest Lake Management Plan, the lake may require further intervention in the future. Be assured Concil remains committed to achieving the ecological, amenity and liveability outcomes associated with healthy waterways.

Strategic management plan

The Forest Lake Strategic Management Plan has been developed by the expert working group and outlines the best evidence-based solutions to improve the long-term health of Forest Lake.

Download:

Expert working group

Due to the complexity of the health issues impacting Forest Lake, Council established a dedicated expert working group in April 2019. This group is made up of Council scientists and external water experts to ensure that any future works undertaken are based on the best expert advice.

Supporting Council's experts are Professor David Hamilton who is the Deputy Director of the Australian Rivers Institute, Griffith University and Tony Weber who is one of Australia's leading practitioners in catchment modelling and water quality.

How you can help

As a local resident living in the lake catchment, you can help reduce nutrients and sediment from entering the lake by making a few small changes to your lifestyle.

Some of the things that will help reduce the number of new nutrients entering the lake are:

  • continuing to wash cars on the lawn to avoid detergents from entering the lake
  • reducing the use of fertilisers in the garden
  • collecting and disposing of lawn clippings
  • not feeding the lake's population of ducks and wader birds
  • picking up and disposing of dog droppings.

Get involved

Council has received some interest from the community to form a new Habitat Brisbane group in Forest Lake. The Habitat Brisbane Program provides an opportunity for the local community to work with Council to protect and enhance the habitat values of local parks and natural areas.

A new group is in the early stages of formation and will be working from Desoto Place Park. The group's future leaders are currently participating in a mandatory twelve-month training program with Habitat Brisbane officers. This training assists the group in refining future work zones and objectives and ensures the group will be ready to proactively manage the unique needs of the Forest Lake ecosystem. The Forest Lake Habitat Brisbane group is anticipated to formally commence conservation activities in early 2022.

If you are passionate about the environment and are keen to make a difference with hands-on volunteering or would like to learn more, phone Council on 07 3403 8888.

Register for updates

Register for updates on the Forest Lake management plan.

More information

For more information:

  • email the project team
  • phone the project team on 1800 669 416 (during business hours)
  • phone Council's Contact Centre on 07 3403 8888 (after hours).
  • write to:
    Forest Lake management plan project
    City Projects
    Brisbane City Council
    GPO Box 1434
    Brisbane Qld 4001.
Last updated: 23 August 2021