Peter Hopper Lake revitalisation

The project’s first stage started in February 2024 and concluded in June 2024. It involved dredging the lake to remove silt and other pollutants that had built up on the lakebed over decades. Approximately 3000 cubic metres of sediment was removed from the lakebed during this process.

This approach to removing the pollutants had the benefit of maintaining the amenity of the lake, reducing potential noise and odour issues and reducing the impact on flora and fauna.

In August 2024, Council awarded a contract for the second stage of the revitalisation project.

This stage includes reconstruction of the lakebed to remove the waterbody’s central island, construction of a gross pollutant trap, sediment basin and raingarden to improve the quality of stormwater before it enters the lake.

The second stage, which will commence when the timing is suitable for local fauna, includes further lowering of the lake’s water level to allow for the earthworks to be undertaken and installation of pumps to circulate the lake water to the raingarden.

• Peter Hopper Lake has accumulated large quantities of silt from stormwater run-off that feeds into the lake.

• Silts bind all sorts of contaminants as they wash off the catchment, including phosphorus which impacts the lake's water quality through over-nutrification, leading to algae blooms and low oxygen levels in the water.

• We will remove all silt from the bottom of the lake and install a gross pollutant trap upstream to catch coarse organic debris.

• A sediment pond will be built at the lake's inlet to capture finer silts before they enter the lake. These will protect the lake from ongoing natural contamination in the future.

• The lake's catchment does not currently supply enough water for the lake to refresh itself regularly.

• We'll be increasing the lake's inflow of water and upgrading the lake's overflow capacity in order to achieve more water turnover.

• Peter Hopper Lake is a large waterbody and movement of water is dependent on stormwater flowing in and out of the lake.

• This means that between rain events, water does not move around as much.

• To help move the water regularly and avoid stagnation, we'll be installing a pump system at the lake.

• Nutrients, such as nitrogen and phosphorus, occur naturally but much of the nutrients in our waterways come from human activities such as fertilisers or from animal droppings.

• When there is an excess of nutrients in the water, it can lead to algae blooms.

• To continuously filter out excess nutrients, we're constructing a specifically designed raingarden in the northern part of Redleap Reserve.

• Lake water will be pumped to the raingarden and be filtered through a sandy soil and nutrient-hungry vegetation before making its way back to the lake.

The proposal to retrofit the lake with water-quality-improving infrastructure resonated well with the community.

We received ideas on these additional assets which the project delivery team will consider in the finalisation of the design.This includes:

• an optimised location for the bioretention (raingarden) system to have less impact on current park use
• infrastructure features which are safe for wildlife
• possible retention of the lake island infrastructure installations.

A variation to the lake redesign will be published and shared with the community once available.

More information on raingardens is available on Melbourne Water's website.

• As part of the design phase, we have engaged ecology experts who will inform the management of all species identified on-site before, during and after construction.

• A Wildlife Management Plan will be prepared for this purpose which will also inform about the adequate handling of pest species like the European carp and the management of the unsustainable population of white ibis on the island.

• We have received a number of habitat creation ideas from the community, of which a vast majority will be considered in the final design of the works.

• We will be exploring terrestrial, floating, and underwater habitats, and their safe and successful implementation will be guided by specialist ecological advice.

• We have received a large spectrum of ideas on how to improve and add to the aesthetics of the lake.

• In working through the detailed design, we are currently exploring opportunities to utilise both existing and future infrastructure to provide for purposeful engagement with the lake that is safe for both animals and visitors.

• This will include viewing platforms and resting opportunities in appropriate locations, as well as small fountains that will add a playful feature while drawing in oxygen from the air which is a healthy addition to the lake.

• The strong landscaping expertise the design team brings to this project will ensure that the lake retains its beautiful natural look.

• Safety in design, construction and future operations will be at the heart of the revitalisation of Peter Hopper Lake.

• We will use the opportunity to overhaul the lake's educational signage to promote good visitor behaviour and discourage bad behaviour.

• With the lake acting predominantly as wildlife habitat, we are committed to reinstating the asset to be a home for fauna and flora that visitors can engage with in a safe and respectful manner, and that all age groups will be able to enjoy.

This activity is jointly funded by the Australian Government’s Urban Rivers and Catchments Program, and the City of Whittlesea.

• Water quality varies at different times of the year and seasonal temperature fluctations play a role. Particularly in summer, warmer temperatures combine with low oxygen levels and high nutrient levels, leading to algae blooms.

• Pollutants such as chemicals, animal droppings and other debris can also be washed into lakes through stormwater run-off, contributing to a decline in water quality.

• Peter Hopper Lake is large and requires substantial rainfall to be able to refresh the water often. If this doesn’t happen, the water becomes stagnant, allowing the build up of harmful micro-organisms, insect larvae, and algae blooms.

We have been working to address the poor water quality in the lake in a number of ways.

• Adding binding agents to remove excess phosphorus in the water.
• Applying a specialised treatment to increase the oxygen levels in the water.
• Installing four air dispersers to help oxygenate the water at its deepest and most stagnant locations. 

Unfortunately, these treatments haven't had long-lasting effects.

More substantial work is required to improve the long-term health of the lake.

Following extensive investigations and expert recommendations, we now have a long-term plan to improve the water quality of Peter Hopper Lake. 

• The first stage will desilt the lake using special dredging equipment to remove excess sediment and debris. One of the advantages of dredging is that the lake’s water level can be maintained, reducing the impact of odour and having little effect on wildlife.

• The second stage of the rectification works involve draining the lake to enable the installation of a gross pollutant trap and sediment pond. These capture water and filter pollutants before they go into the lake.

• An offline pumped raingarden will be established to further filter and treat the water.

• A circulation pump will be installed to ensure water does not remain stagnant, which helps minimise algae formation. 

The first stage of the project, to desilt the lake, began in February 2024 and finished in June 2024.

The second stage of works will commence when the timing is suitable for the local fauna and all relevant permits have been issued.

• There will be no public access to Peter Hopper Lake until the desilting has been completed and all the new infrastructure is installed. 

• During the works, the lake will need to be drained to allow for the safe construction of the sediment pond and infrastructure. 

• Once construction is complete, the lake will be progressively refilled and landscaping undertaken in and around the site. 

• The footpath around the lake is expected to remain open to pedestrians throughout the desilting works.

• We are working closely with zoologists to manage the impacts on the various wildlife, including the White Ibis population on the central island.

• A Wildlife Management Plan is being prepared to ensure that all species are cared for through safe dispersion or temporary relocation. This process is planned to take place outside of the common breeding season. 

• While disturbance to wildlife is expected to be minimal during the desilting stage, a zoologist will be engaged to oversee the site and attend to any animal salvage and relocation as necessary. 

• We will be preparing a Wildlife Management Plan for the lake and specifically address the white ibis population that nests on the central island in Peter Hopper Lake.

• We will also work with the Department of Energy, Environment and Climate Action on developing a long-term, localised solution for the birds.

If you see any sick, distressed, abandoned or dead wildlife, please do not handle the animal yourself. 

Contact the City of Whittlesea’s customer service team on 03 9217 2170 to have the animal removed safely. 

For non-urgent inquiries regarding the Peter Hopper Lake revitalisation project, please email peterhopperlake@whittlesea.vic.gov.au.

There are carp present in the lake that will be removed to benefit the revitalisation of Peter Hopper Lake.

Carp are an introduced species of fish and are a known major aquatic pest by the Victorian Fisheries Authority.

For more information on carp, visit the Victorian Fisheries Authority website.

While works are in progress, we will continue to manage the conditions of the lake using the methods we have been using to date, which includes algaecides to suppress blue-green algae growth. 

The lake will remain open for the most part during the desilting stage. However, we ask that visitors: 

• avoid contact with the lake water
• keep dogs on a leash 
• not handle birds or other wildlife
• not feed the birds as this can attract further wildlife to the site
• not fish in the lake
• not leave rubbish behind.