13 February 2026
Melbourne Water manages the Western Treatment Plant (WTP) to treat about half of Melbourne’s sewage, as well as for other purposes like biodiversity conservation. To help with this process, we established a committee now known as the Biodiversity Conservation Advisory Committee (BCAC).
The BCAC is tasked with providing specialist advice on the conservation, research, enjoyment and management of the WTP’s native biodiversity values. It has operated for almost 40 years (since 1986) and has helped us achieve many successes in biodiversity conservation.
This newsletter highlights some of BCAC’s work during 2024-25. Read it online or download a copy below:
During the winter months, we undertake planning to manage water levels in conservation ponds. This provides or enhances habitat for migratory shorebirds, other waterbirds and Growling Grass Frogs.
For migratory shorebirds we aim to optimise habitat values during the times of peak abundance between September and April. Additional water is also delivered across irrigated pastures to support critical terrestrial habitat for waterbird species such as Straw-necked Ibis.
Melbourne Water manages the range of habitats at the WTP via a program of:
This year, activities benefitting from BCAC advice include:
Melbourne Water is developing a Coastal Hazard Assessment Adaptation and Resilience Plan. This will address site-specific risks and issues from sea level rise and the consequent foreshore erosion.
This includes protecting critical habitats and biodiversity infrastructure such as intertidal areas, saltmarsh and constructed wetlands. BCAC provided advice on the habitat values and how to best minimise disturbance.
In February 2024, Melbourne Water raised opportunities for BCAC members to contribute ideas for minor capital works to enhance biodiversity and conservation values across the site. The BCAC and Melbourne Water team expressed interested in improving habitat for cormorants, such as installing floating platforms in operational lagoons to provide additional sites for roosting and nesting.
This project has progressed to the design stage, with the aim of installation at the 25W lagoon in the non-breeding season in 2026. The main breeding season for Pied Cormorants at the WTP is from January to June.
Pied Cormorants are the main focus as they are the most numerous species nesting at the WTP, and are known to nest regularly at only a few sites in Victoria. Five species of cormorant roost regularly at the 25W lagoon and four of them nest there (plus a few related Australasian Darters (Anhinga novaehollandiae), making it one of the most diverse breeding colonies of such birds in the world.
Melbourne Water and BCAC continue to work closely with farming leaseholders MPH Agriculture to manage and enhance biodiversity outcomes across the site. In 2023, MPH Agriculture reviewed the current agricultural lease. This investigated the relationship between irrigating the terrestrial margins and bird populations – particularly the Straw-necked Ibis, which relies on irrigated pasture and paddocks for foraging.
As a result of this this review, the timing of irrigation delivery has been adjusted to provide more water to paddocks during the period of peak abundance of Straw-necked Ibis (December to June), and less water from July to November. The latter period coincides with generally high rainfall in Victoria, and most ibis leave the WTP to breed at wetlands elsewhere.
A new initiative this year has been supplementing regular monitoring of ibis numbers with GPS transmitters, to assess the extent of their movements more broadly.
The Arthur Rylah Institute (ARI) has monitored Straw-Necked Ibis numbers and habitat use at the plant since 2001, and continues to do this with Melbourne Water funding.
Eighteen solar-powered transmitters have been attached to Straw-necked Ibis captured at the WTP, providing real-time detailed movement data for about 2 years before they fall off.
Already, the transmitters are providing detailed data on feeding, roosting and breeding sites, how management at the treatment plant affects these behaviours, and the effects of irrigation on ibis numbers.
Image: Straw-necked Ibis tracker fitting. Photo courtesy of Dan Purdey.
The extent and complexity of their movements have proved remarkable, with some ibis flying over 10,000 km in a single year. Most of these movements were made within southern Victoria, but some also visited the Murray River floodplains, one travelled west to South Australia and one went north to Queensland.
During autumn and winter 2025, 13 individuals of this critically-endangered species were observed at the treatment plant. This number is the most seen at the WTP this century, reflecting a welcome increase in the wild population as a result of active management by the multi-state Orange-bellied Parrot Recovery Team.
The WTP and adjacent Spit Nature Conservation Reserve were a stronghold for the species from the 1970s to the 1990s.
In research aimed at streamlining monitoring of this species, both the Australian National University and Arthur Rylah Institute have deployed acoustic monitoring equipment in appropriate habitat at the treatment plant to test its efficacy for detecting the presence of Orange-bellied Parrots.
Image: Orange-bellied Parrot (Neophema chrysogaster). Photo courtesy of Kathryn Hocking.
The resulting data will be used to develop improved call recogniser models for the species with application across the entire range of the species. Orange-bellied Parrots breed in remote wilderness in south-west Tasmania and migrate to spend the winter in coastal saltmarsh mainly in Victoria and South Australia.
During the past few years our dedicated birdwatching community has added two new species to the Western Treatment Plant bird list: a Black Tern found on 2 April 2023, and an American Golden Plover found on 19 April 2024. Both were in breeding plumage, and the Black Tern was found to be of the American subspecies surinamensis.
With these additions the WTP bird list now stands at 313 species!
Another significant find was the Fat tailed Dunnart and their unique nests, recently spotted by Melbourne Water staff and Wadawurrung Traditional Owners while undertaking survey and conservation works at T-Section Grassland. It’s been 10 years since the dunnart has been sighted at the treatment plant.
Melbourne Water respectfully acknowledges the Bunurong, Gunaikurnai,
Taungurung, Wadawurrung and Wurundjeri Woi-wurrung peoples as the Traditional
Owners and Custodians of the land and water on which we rely and operate.
We
pay our deepest respects to their Elders - past, present and emerging.
