Peter Hopper Lake, situated within Redleap Recreation Reserve in Mill Park, is one of the City of Whittlesea's largest waterbodies and attracts visitors from the community, as well as beyond the municipality.
In recent years, the lake has experienced numerous algae outbreaks and water quality issues. While various treatments have had some success in restoring water quality, the effects have not been long-lasting and further work is required to improve the long-term health of the lake.
City of Whittlesea is committed to providing a long-term solution to rehabilitate Peter Hopper Lake. Council has engaged a specialist consultant to provide expert advice and develop a feasible long-term plan to improve the water quality and revive the vitality of Peter Hopper Lake.
Improving water quality
There are several factors that have contributed to the lake's poor water quality. The upgrade will address these issues to ensure the lake will remain a place for the community and wildlife to enjoy for years to come.
Mud: 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. Council will remove all silt from the bottom of the lake and will install a gross pollutant trap upstream of the lake 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.
Water quantity: The lake's catchment does not currently supply enough water for the lake to refresh itself regularly. Council will be increasing the lake's inflow of water and upgrade the lake's overflow capacity in order to achieve more water turnover.
Circulation: 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 it becoming stagnant, Council will be installing a pump system at the lake.
Nutrients: 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. In order to continuously filter out excess nutrients, Council will construct 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.
Council received overwhelmingly positive feedback on the lake rectification proposal during the public consultation period between March and June 2023.
The feedback received through our online Engage page, as well as through our on-site pop-ups and consultation with the Friends of Peter Hopper Lake Group, can be summarised in the following themes:
Proposed infrastructure: The proposal to retrofit the lake with water-quality-improving infrastructure resonated well with the community. We have 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 the current park use, infrastructure features which are safe for wildlife, and perhaps the 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.
Site management: Given the substantial works required on the lake and the duration of the rehabilitation needing to allow for desilting, construction and re-establishment, residents have concerns about the traffic situation, noise levels and overall site accessibility during this time. Council has engaged a specialist consultant for the design of the lake's new infrastructure and is currently in the process of working through the site logistics and the impacts to visitors and local residents. Council will ensure that the impacts are communication to affected reserve users and neighbours, directly and through this website.
Wildlife: As part of the design phase, Council has 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 further received a number of habitat creation ideas from the community of which a vast majority will find consideration in the final design of the works. Council will be exploring terrestrial, floating as well as underwater habitat, and their safe and successful implementation will be guided by specialist ecological advice.
Amenity: We have also received a large spectrum of ideas on how to improve and add to the aesthetics of the lake. In working through the detailed design, Council is 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: Safety in design, construction and future operations will be at the heart of the revitalisation of Peter Hopper Lake. Council will use the opportunity to overhaul the lake's educational signage and promote good visitor behaviour and discourage bad behaviour either through novel design or signage. With the lake acting predominantly as wildlife habitat, Council is 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.
Respondents also said:
Frequently Asked Questions
+ What has caused the poor water quality?
When it comes to lakes, it is not uncommon to see water quality decline from time to time, particularly during the summer months when warm water temperatures, combined with low oxygen levels and high nutrient levels, lead to algae blooms and bacterial infestations.
Pollutants such as chemicals from garden fertilisers and pesticides that are washed into the lake through stormwater run-off, animal droppings and other debris such as leaves also contribute to a decline in water quality.
Peter Hopper Lake is a large lake and requires substantial rainfall to be able to "refresh" itself frequently. When this doesn't occur, the water can become stagnant, adding to issues of water quality.
+ What has been done to try to fix the problem?
Council has been working to address the poor water quality in the lake in a number of different ways, including adding binding agents to remove excess phosphorus in the water (too much phosphorus can lead to algae blooms), applying a specialised treatment to increase the oxygen levels in the water and installing four air dispersers to help oxygenate the water at its deepest and most stagnant locations.
Unfortunately, though, these treatments have not had long-lasting effects and further, more substantial work is required to improve the long-term health of the lake.
+ What is planned to improve the long-term quality of the lake?
In order to fix the ongoing water quality problems experienced at Peter Hopper Lake, substantial work is required.
Following extensive investigations and expert recommendations, the lake will firstly require desilting, which means that the water in the lake will be drained and the silt (mud) and sediment (debris) that has collected in the bottom of the lake over many years will be removed.
In addition, a range of new infrastructure will be built to help filter water flowing into the ensure continuous water movement to avoid the issues currently seen as a result of stagnant water. This includes a new raingarden, which filters out excessive nutrients from the water, and a sediment pond at the lake inlet to help separate incoming silts from the main body of water.
More information about raingardens is available on Melbourne Water's website.
Finally, a circulation pump will ensure water does not remain stagnant, which will help minimise the forming algae.
+ When will the work begin?
Timelines are yet to be finalised, however, it is anticipated work will begin in early 2024 when the dry season allows for optimal conditions to desilt the lake and construct the additional water treatment assets.
+ How long will the work take?
Again, no timeline has been finalised, however it is expected that the overall construction period, including landscaping works, will take about 12 months to complete.
+ How will the work impact the lake and surrounding area?
Access to Peter Hopper Lake will be closed once the rectification works commence and isolation of the lake will remain in place until all new infrastructure has been established and it is fit to receive water again.
During the works, the lake will need to be drained to allow for the safe construction of the sediment pond and other infrastructure.
The desilting process will require the silt and sediment that is removed from the bottom of the lake to be dried out prior to disposal. As it dries, the silt may have an unpleasant odour, which is caused by natural materials breaking down. We will work to speed up this process as much as possible and Council will be advising affected residents about the likely duration and the methods used to complete this major task in reviving the lake.
Once construction is complete, the lake will be progressively refilled and landscaping (vegetation planting) in and around the lake will take place.
+ What will happen to the wildlife at the lake?
Council is working closely with ecologists and the local community to identify the various wildlife that call Peter Hopper Lake home.
A Wildlife Management Plan will be prepared prior to construction to ensure that all species are cared for to enable safe dispersion or temporary rehoming. This process is planned to take place outside of known breeding seasons.
+ What is being done about the ibis population on the lake's island?
Council 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.
+ What should I do if I see any wildlife in the area that requires assistance?
If you see any sick wildlife, please contact Wildlife Victoria on 8400 7300 or visit their website to lodge a request to have the animal attended to.
Please do not handle the animal yourself. If you see a dead animal in or near the lake, please contact Council on 9217 2170 to have the animal removed safely.
+ What else can I do?
Until work begins on-site, we will continue to manage the condition of the lake using the methods we have been using to date.
While the lake currently remains open, we ask visitors to:
- Avoid contact with the lake water and keep dogs on a leash. No access into the lake is permitted
- Not handle birds or other wildlife
- Not feed the birds as this can attract further wildlife to the site
- Not fish in the lake
- Don't leave rubbish behind
For more information on the Peter Hopper Lake revitalisation project, call Council on (03) 9217 2170 or if you speak a language other than English, call on 131 450.