Forest Lake management plan

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 investing more than $1 million over two-and-a-half years to implement a long-term plan to combat the ongoing issues affecting Forest Lake.

This program is in addition to a range of other measures Council is undertaking to improve the health of Forest Lake.

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 algal blooms on Forest Lake and improve the health of the lake ecosystem
Latest update

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

Project background

The lake at Forest Lake is a man-made wetland that was originally designed as a stormwater quality improvement device to:

  • improve water quality flowing into the downstream creek system (Oxley Creek)
  • provide recreational and visual amenity for the community.

A number of environmental issues have affected the lake over the last few years including:

  • blue-green algae growth, creating poor water quality that can cause skin and eye irritations for people and pets touching the water, as well as emitting a strong musty odour
  • growth of the water weed salvina, which is highly invasive, can cover the whole lake surface and reduces oxygen levels for fish and other aquatic species, resulting in the death of the pest fish, tilapia (cichlid fish) and small numbers of native catfish
  • the ibis populations increasing on Bird Island and other areas around the lake, resulting in odour issues and high nutrient levels in the lake.

There is no one quick fix to solve these environmental issues at this man-made lake. Improving the health of the lake ecosystem will need a range of solutions and will take time.

About the project

A two-and-a-half-year program is underway to improve the health of Forest Lake. This includes the following measures to reduce sediment and nutrient levels in the lake and enhance water movement. These are key elements in reducing the conditions that support algal blooms.

  1. Development of a strategic management plan for the long-term management of the lake.
  2. Desilting the lake to remove large volumes of sediment and nutrient loads that have built-up over time.
  3. Replanting with aquatic macrophytes to encourage the return from an algae-based system to a plant-based system.

While these measures are being introduced and until the ecosystem health improves, the lake may see further occurrences of algal blooms and salvinia growth.

Download the:

Expert working group

The issues affecting the health of Forest Lake are complex and required the attention of dedicated experts. In April 2019, Council developed a working group 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, Deputy Director of the Australian Rivers Institute at Griffith University and Tony Webster, one of Australia's leading practitioners in the catchment modelling and water quality field.

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.

The purpose of the strategic management plan is to:

  • document the current condition and existing maintenance practices at the lake
  • document outcomes from the Forest Lake working group, which was established in April 2019 to bring Council and external experts together to develop a robust plan for the lake's health
  • identify future lake management options to reduce the frequency and abundance of algal blooms, while also improving the overall condition of the lake
  • recommend a lake monitoring plan to address data gaps and ensure the long-term health of the lake.

Download the strategic plan in your preferred format:

Findings from investigation works

Since March 2019, Council has been out on the lake with boats and sampling equipment. This is part of undertaking important investigations to get a more in-depth understanding of water quality by sampling throughout the water column at different depths. The following sampling was undertaken as part of the strategic management plan.

Water quality sampling and analysis (surface water, groundwater and sediment)

  • physico-chemical parameters (pH, dissolved oxygen, conductivity, temperature, turbidity
  • blue-green algae (species, toxicity)
  • total dissolved solids
  • total suspended solids
  • total alkalinity
  • total organic carbon
  • bicarbonate
  • carbonate
  • hydroxide
  • chloride
  • major ions (calcium, magnesium, sodium, potassium)
  • nutrients (ammonium, oxides of nitrogen (nitrite, nitrate), nitrite, nitrate, total Kieldahl nitrogen, total nitrogen, ortho-phosphorus, total phosphorus)'
  • water hardness
  • total and dissolved metals and metalloids (aluminium, arsenic, boran, barium, cadmium, cobalt, chromium, copper, iron, manganese, molybdenum, nickel, lead, zinc, mercury
  • silica
  • sulphur
  • polycyclic aromatic hydrocarbons
  • polycholorinated biphenyls
  • total petroleum hydrocarbons
  • BTEX
  • organochlorine and organophosphorus pesticides.

Aquatic ecological assessment

  • aquatic vegetation
  • macroinvertebrate communities
  • fish communities
  • turtle communities
  • birds.

The key findings from the ecological investigation works are listed below.

  • Forest Lake supports an array of biodiversity including six native fish species, over 50 bird species, a high diversity of aquatic macroinvertebrates and three native submerged aquatic plants.
  • Despite recent algal and salvinia blooms, the presence of aquatic macroinvertebrates and native submerged aquatic plants indicate better water quality than expected. These species are usually quite sensitive to changes in water quality and poor light penetration.
  • The six native fish species identified include eel-tailed catfish, spangled perch, garfish and eels, and occur in healthy numbers.
  • Although only a few turtles were sampled formally as part of the investigations, a large number of short-necked turtles were observed and believed to be in good health.

The work has helped us understand the current conditions and species at the lake, which informed the development of the strategic management plan.

If you would like a copy of the sampling report, email the project team.

Proposed solution

Council is committed to building and maintaining the infrastructure for the future while protecting our unique lifestyle, local greenspace and parks. To find the best solution for the lake, the working group divided lake management options into four categories:

  • reducing nutrient levels (both those entering the lake and those already in the lake)
  • reducing light availability
  • recreating a more 'plant-based' lake system
  • potentially increasing water movement in the lake.

Additional monitoring is proposed to address key data gaps over time and continue to adapt the management of the lake.

Timing

The plan recommends strategic desilting in areas of the lake to start in April 2020, followed by planting in those zones and more broadly across the open water areas of the lake.

The timeline below for the desilting and replanting activities has been recommended by Tony Webber, Professor David Hamilton and the working group. Timing is subject to weather and site conditions.

This table includes the timing for desilting and replanting activities for Forest Lake.
Action Date
Final strategic management plan and rehabilitation plan Complete July 2019
Planning and design Complete August 2019
Approvals, permits, procurement and tendering August 2019-March 2020
Desilting and replanting  April 2020-late 2020 

This new program of activities will be undertaken in addition to Council’s existing efforts to manage Forest Lake including:

  • an ibis management program
  • salvinia weed harvesting
  • cleaning out litter traps upstream of the lake
  • algae scum collection and disposal.

Council has an ongoing program of works at Forest Lake to improve amenities including park furniture, landscaping, toilet blocks and car parking.

Ibis population

Ibis are an Australia native species protected by Queensland Government law. Council is attempting to address the growing ibis populations on the small islands and vegetation at the lake, which have also contributed to the excess nutrients in the lake.

As part of Council’s Ibis Management Plan, wildlife consultants try to manage the ibis population through egg and nest management.

Council also recently received approval to proceed with the additional vegetation management plan for the lake. As part of this plan, Council has begun works to remove some vegetation and will replace some reeds and rushes around the lake with plants that are less suited to ibis roosting to deter ibis from the lake.

Student research project 

A Griffith University student research project is currently underway in partnership with Council to model water quality and ecosystem dynamics at Forest Lake. This project is coordinated through the Australian Rivers Institute at Griffith University, as part ongoing research projects undertaken with Council.

The modelling will provide: 

  • an understanding of the present state of the lake’s ecology and water quality
  • the potential future state of the lake through analysis of newly proposed methods and technologies for algae bloom management and sediment deposition. 

The research project was concluded in late May 2019 and the findings were provided to the project team developing the Forest Lake Strategic Management Plan. 

What you can do

As a local resident living in the lake catchment, you can also play a part in reducing the build-up of nutrients and sediments entering the lake. Some of the things that we can all do in our day-to-day lives to help improve the health of the lake are:

  • washing cars on the lawn
  • reducing fertiliser use, particularly before rain
  • collecting lawn clippings
  • not feeding the ducks and wader birds
  • picking up dog droppings.

Get involved

We have 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 number of sites including Desoto Park and Hancock Park-Pine Village Park have been suggested by local residents as potential Habitat Brisbane sites. Although not directly located on the lake, Desoto Park has bushland registered as Endangered Regional Ecosystems and is a strategic corridor linking Greenbank and Oxley Creek, with run-off into Forest Lake.

If you are interested in joining the group or learning more, please email the project team.

If you’re passionate about the environment and are keen to make a difference with hands-on volunteering, 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).
Last updated:16 September 2019