In the wake of the Grampians bushfire, will the Wannon River get the water it needs?
This is the final – and arguably most important – of the three stories in our special mid-month “bushfire edition” of the NGT Newsletter.

As you are probably already aware, the bushfire that impacted Walker Swamp, also burned a massive swathe of the eastern and south-eastern portions of the Grampians National Park – where the fire started as a result of a lightning strike in a remote area in the park.
This fire footprint means that the entire length of the upper Wannon River in the National Park has just burned in a single bushfire event for the first time in living memory, including a biodiversity hot-spot and refuge adjacent to Walker Swamp, which locals refer to as the “Wannon fan”. This alluvial fan, where the Wannon River sheets broadly along multiple flowpaths, through dense tea-tree shrubland and forest, burned intensely hot – as shown right.
In the image below you will see how this area is where the river breaks into a series of distributaries, which in turn provide water to a chain of wetlands now restored by NGT: Brady Swamp, Gooseneck Swamp and parts of NGT’s Walker Swamp Restoration Reserve next door to the National Park. The river re-forms into a single channel on the western side of Brady Swamp, where it continues downstream towards Dunkeld.

What is not widely known however, is that even though the upper Wannon River is entirely embedded within a National Park, changes were made long ago to its headwater streams, that – if current state government water policy is not temporarily paused, reviewed or changed – will see critical flows diverted away from the river this coming winter and spring.
Given that the ecological recovery of the river (and the successful post-fire survival and persistence of nationally threatened species that depend upon that recovery) is at stake, NGT has just taken what, for us, is a rare step.
NGT have written to the Victorian Minister for Water, The Hon. Gayle Tierney MP, asking for her urgent intervention to review the operating rules of the Wannon diversions before winter. We have also written to a range of 12 other organisations with a stake, interest or formal role in this issue, asking them to work together and provide their support.
We genuinely hope that a common sense approach will see the Wannon River have its full catchment temporarily reinstated for the coming winter and spring, for this year at least, to assist in its post-fire recovery.
In this article, we outline why this is a such a critical decision for the river.
Background context
Beyond the wetland restoration works completed over the past decade by NGT within and adjacent to the National Park at the terminus of the Wannon alluvial fan, we have also taken a keen and active interest in the health of the Wannon River in the National Park upstream. We have become increasingly aware that changes to river flows are impacting average annual water availability, despite occasional periods of high rainfall, as occurred in 2022 (and illustrated by the images in this story). This context is vital to understand, because a river’s health is best measured by how well it copes during the dry times (e.g. persistence of permanent pools) and its resilience to disturbances (e,g, bushfire), not during floods.
Thanks to the support of Parks Victoria and the Australian Government (via the Australian Heritage Grants Program 2020-21), over the past few years, NGT completed an important study on the Wannon River (you can read past stories about some of that work here), which helped to document the ecological values of the river between Brady Swamp and its headwaters on the Major Mitchell Plateau. Our work highlighted the value of this stretch of the river in the National Park, including how it provides critical refuge habitat for a range of threatened aquatic species, including nationally listed species.
The final Issues and Recommendations Summary Report associated with that project (Farrington, Bachmann and Kerr, 2024) was only completed last year, and is timely given the impacts of the recent bushfire on this reach of the river.
The full report is attached here for your information.
What exactly are the Wannon Diversions?
As part of the project, we investigated some of the lesser known elements of the Wannon River story, including activities over the past 200 years that have altered the river’s hydrology and ecology.
One of the most prominent of those changes, which continues to impact the river today, happened in 1971, when a couple of the most reliable headwater streams of the Wannon River were diverted to a neighboring waterway (Fyans Creek), to artificially increase the catchment available to the dam near Halls Gap, Lake Bellfield. The diversions currently occur each winter and spring for 5 months, from 1st June to 30th October annually, and have significantly reduced flows to the upper Wannon River during the most important (and typically reliable) period for flows.
The following are excerpts from the report that more comprehensively explain the diversions and their impact.
From page 10:
“The Wannon diversion pipeline was completed in 1971. Under this scheme, now managed by the Grampians Wimmera Mallee Water Corporation, water is regulated at three locations on the First and Second Wannon Creeks and piped by gravity to the headwaters of Fyans Creek for transfer to either Lake Bellfield and use in the Wimmera-Mallee System, or historically to Stawell for domestic supply.
Despite being relatively modest in catchment area, this part of the Wannon River catchment is significant for its reliability and quantity of rainfall, being situated within the highest elevations of the Grampians (with highest average rainfall) which often receives rainfall when lower altitude catchment areas downstream do not.
The average annual diversion from these headwater streams between 1971 and 2000 (4.5 GL), reduced Wannon River overbank flows from an average of 4.49 events/season to 2.76 events/season and a decline in average duration from 5.2 to 3.4 days (Szabo et al. 2018).
Since 2000, the diversions have operated each year during the most reliable winter-spring flow period, from start of June until the end of October (average annual diversion volume from 2000 to present is 2.9 GL).
This means that in years where initial flows don’t establish [in the Wannon River] before June, which has become increasingly regular since 1996, the diversions have had a greater impact on the initial wetting up of the river system downstream and result in earlier annual cease to flow conditions in late spring.”
From pages 14 and 15:
“In addition to a background drying trend over the past 30 years, the diversion of the headwater streams since 1971 has artificially imposed an additional drying effect on the upper Wannon River. Because the volume of water required for overbank flows and flood events to occur, which are important for many of the vegetation communities through zones 3 and 4, are larger than any shortfalls created by water harvesting, the impact of the diversions during wetter climatic phases on river ecology is less clear or apparent. However, and in contrast, it is during low-moderate flow years that the impact of the diversions is especially observable and pronounced.
In the years since a step-change in flows occurred in the mid-1990s, the diversion volumes largely correlate with the deviation of upper Wannon flows from average (as measured upstream of Jimmy Creek) for the main runoff season of June to October, as shown the figure below.

The figure above highlights the combined impact of diversions and the step-change in climate (rainfall and runoff) that has occurred since the mid-1990s. For example, since the headwater stream diversions were constructed in 1971, the Wannon River has experienced a below average flow in a total of 36 of 53 years (or 2/3 of years), and diversions have occurred in every year except for two.
The pattern of when those below average flow years have occurred is especially revealing, namely:
- Between 1971-1996, the impact of the diversions was less obvious with:
- only 12 years of 26 (46%) being of below average flows, and
- only four times did the river’s flow deficit (below average) exceed the volume diverted.
- Since 1997 however, the impact of the diversions and climate is clearly apparent, with:
- 25 years of 27 (93%) being of below average flows, and
- in 22 of these years, the magnitude of the river’s flow deficit (below average) exceeded the total volume diverted that year.
In a drying climate, where we experience low-moderate flow years more regularly, the impact of the water being lost (via the diversions) to the health and ecology of the Wannon River cannot be understated. The data clearly indicates that over time, the diversions are having an increasingly regular impact on the reliability and availability of flows to the Wannon River.”
Our key recommendations to protect the health of the Wannon River
In the 2024 review, we recommended that:
(1) a more equitable and balanced framework for determining future water diversions be developed, where the ecological needs of the upper Wannon River through the winter and spring flow period are actively considered.
(2) as a result of this framework, a more responsive, adaptive and sophisticated flow management system be devised and implemented, where annual diversions in future only occur once an agreed set of minimum environmental flow requirements of the upper Wannon River within the Grampians National Park have been met.
However, these recommendations should now be read and re-interpreted in the context of the recent bushfire event. This includes the need to ensure more urgent steps are taken to facilitate the protection and recovery of the river ecosystem and its resident threatened species ahead of the upcoming winter/spring flow period in 2025.
Against this backdrop, we have requested that the Victorian Minister for Water consider:
(A) implementing an emergency measure where no diversions are permitted away from the upper Wannon River in 2025, at this time when it is most vulnerable, to provide the river ecosystem and resident aquatic species the best chance of successful recovery from the recent bushfire event.
(B) investing in the collection of detailed data in 2025 to document the impact of this emergency policy intervention, with the findings used to inform the development of a new framework for more nuanced management of the diversions in future, ahead of the 2026 flow season.

Do you want to have a say on this issue?
If you would like to share your own, considered perspective on the Wannon River diversions ahead of the 2025 winter flow period, then we recommend you write to:
The Hon. Gayle Tierney MP
Minister for Water
PO Box 500
East Melbourne VIC 8002
or Email:
Do you want to learn more?
You can read the two reports produced by NGT in 2024, which document the Health of the Wannon River in Grampians-Gariwerd National Park, by clicking on the bold hyperlinks below:
(1) Issues and Recommendations Report – this is an overarching summary report (which is quoted in the article above, and is also shown in the pdf viewer below)
(2) Background Investigation Report – this is the detailed technical report that informed the summary report