Wannon River diversions – your questions answered: Radio interviews, a diagram and video bring the issue into focus

In our recent mid-month special update on the impacts of the Grampians bushfire, we also shared NGT’s perspective on the water needs of the upper Wannon River in its post-fire recovery phase.

As we explained in that recent article, since 1971 the river has had much of the flow from its most reliable headwater streams, the First and Second Wannon Creeks, diverted each year to Lake Bellfield – a dam in an adjacent catchment that was completed in 1969.

In the days following the article, I had the chance to talk about bushfire impacts on the NGT Reserve at Walker Swamp, but we also touched on the topic of the Wannon River diversions. If you would like to hear the part of those interviews dedicated to the upper Wannon in the National Park, please listen via the audio players below:

• South East SA Weekends (Saturday 18th January 2025), with Rod Sparks

• Regional Victoria Saturday Breakfast (Saturday 18th January 2025), with Gavin McGrath

Our update from a couple of weeks ago has also prompted a number of people to reach out wanting to learn more about the Wannon Diversions, because it is now apparent that many people had no idea that they existed. Here are some of the most common questions answered:

Where exactly are the Wannon Diversions?

The Wannon headwaters are diverted from three locations on the First and Second Wannon Creeks, just to the east of the Grampians Road, about 20 km south of Halls Gap. After a short journey by pipeline, the water is discharged into the top of Fyans Creek, a neighbouring catchment to the north, and then flows downstream to the artificial water storage at Lake Bellfield. The infrastructure associated with the diversions is clearly visible in aerial imagery, so I have marked up an oblique aerial view below to give you a feel for the layout of the diversions and how they intercept and divert flow. Please click on the image to enlarge.

Putting aside the ecological impacts of the diversions for just a moment, there is certainly some clever engineering involved.

What do we know about rainfall up on the Major Mitchell Plateau?

The Major Mitchell Plateau sits at a similar elevation to Mount William / Duwil, the highest peak in the Grampians, so although there is no Bureau of Meteorology rainfall gauge specifically on the plateau that feeds the First and Second Wannon Creeks, we are able to use the rainfall figures for Mount William as a reasonably accurate guide.

The rainfall data for last year (2024), during the diversion months of June to October – which also corresponds with the 6 month period leading up to the bushfire – makes for an interesting comparison. While the nearest major towns to the south-west (Hamilton) and east (Ararat), received totals over these five months of just 287 mm and 187 mm of rainfall respectively, in stark contrast Mt William received 680 mm of rain. The breakdown is shown below.

Of course with the diversion infrastructure in place and operating over this period, a significant proportion of the flows generated by this period of good rainfall in the catchments of the First and Second Wannon Creeks, from the highest elevations in the Grampians, never made it to the Wannon River.

Exactly what do the diversions look like when they are working?

It just so happens that we have some excellent footage to illustrate what the diversion looks like on the First Wannon Creek, under flowing conditions, that helps to bring the above annotated diagram to life. The example footage below is from October 2024, just a couple of months before the recent bushfire, and shows how the diversion points – when they are open, in low-moderate flows – are capable of capturing all of the water that would otherwise naturally flow down the Wannon River.

As you can see, it is a simple and highly effective system for diverting flows every winter and spring. This is the current, long-standing management regime that we asking the Minister for Water in Victoria to urgently review before winter 2025.

NGT’s key recommendations to protect the Wannon River

As explained in the previous article, in our 2024 review of the Wannon River (also shared below), 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 recently wrote to the Victorian Minister for Water to ask her to 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