A look at the flow and management at key locations

There is an uncontrolled inflow from high flows on the Darling River and a controlled inflow from Lake Cawndilla that feeds into the Darling Anabranch at Redbank Creek. This makes for one of the more complicated systems to track the flow down.

As a general rule, most high flow events in the lower Darling are caused by winter rainfall in central and northeastern NSW that arrive in late winter and spring, while it is the summer monsoon rainfall in southern Queensland that arrive in autumn.

Some key observations of some recent flow events are noted below:

Quick Summary

The Great Darling Anabranch at the offtake needs around 500 ML/day for pleasant paddling, which is around 14,000 ML/day on the Darling. This is just below a minor flood level.

Cawndilla Channel feeds into the lower Tandou Creek and usually has a small envirnmental flow, albeit not nessarily paddable. A flow of around 1,000 ML/day as measured in the Lake Cawndilla Outlet should provide an enjoyable journey if there is water downstream of at least 250 ML/day.

The speed of the flow through the system is fairly slow, just 8 km/day, so a longer prolonged flow is best.

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History

From 1890 to 1961 water flowed the full length of the Darling Anabranch to the River Murray just nine times.

From 1962 to 2008, there was an annual regulated release into the system that is no longer applicable with the new water pipeline for landowners along the system.

Since 2007 up until 2023, the upper anabranch has only flown naturally five times; in Jan 2010, Mar 2011, Mar 2012, Feb 2022 and a ten month long flow event between May 2022 and Feb 2023. Releases from Lake Cawndilla in 2013 and 2017 provided the other two flow events along the lower anabranch.

Mar 2011 and 2012 saw a high flow from both the Lakes and the Darling. The resulting flow pattern was irregular until the high flows that were seen a number of months after the water release started. Flow of approx. 1,000 ML/day were seen in the lower anabranch for around 6 months.

Late 2013 was from Lake Cawndilla at around 1,000 ML/day. This was seen downstream but with a significantly smaller flow with a reduced flow window that would have been hard to paddle.

Autumn 2017 saw a controlled release from Lake Cawndilla, no flow from the Darling River. This provided a clean flush down the entire anabranch and would have been a comfitable paddle.

Summer 2017-18 saw a slightly smaller release from Lake Cawndilla of around 700 ML/day. Most of the water did not reach the lower anabranch and was likely utilised for irragation or simply lost in the heat of summer.

Mid-2021 to 2024 saw a small controlled release from the lakes, followed by a high flow from the Darling. This provided nearly two years worth of good flow to the lower anabranch, including some widespread flooding at the peak that filled most of the lakes other than Lake Tandou.

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Anabranch Start to Flow

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Lakes

To complicate matters, there is a series of 16 lakes along the Darling Anabranch that range from 120 to 11,000 ha in size. Water can be diverted into the lakes making it difficult to forecast the flow along the system. For example, in 2022, the high flows from both the Lakes and the Darling itself were mainly being diverted into the lakes. An uncontrolled flow into Popio Lake was still taking approximately two thirds of the remaining flow from the system as I paddled past. This is more likely to occur after the initial peak flows down the system as they try to minimise the impacts of prolonged flooding to the river banks. You should be able to see the lakes fill from the National Maps DEA Surface Reflectance (Sentinel-2 Near Real-Time). This will give you some idea of what is happening in the middle section of the anabranch before the gauge at Dam 183.

A similar thing happened on my second trip, with the lake inflows significantly buffering the flow down the system.

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Flow Speeds

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Personal Experience

I paddled Cawndilla Channel, Tandou Creek, Redbank Creek and the upper section of the Anabranch on around 1,000 ML/day. This provided great paddling conditions, but there were a few spots where a lower flow could become problematic, namely upper Tandou Creek, and the snaggy and tree-filled sections of the other areas. It is difficult to estimate the point where paddling around the thickets of trees will become unnavigable. Similar thickets on the lower anabranch were navigated with a lower flow.

Due to an uncontrolled redirection of water into Popio Lake, I mostly paddled the lower section at 300 ML/day. The conditions with this flow were generally easier than in the top section due to cleaner pools and channels. At this height I ran three channelled flowing sections and a number of wider flowing or pool sections that were shallow, but I only grounded the kayak a small number of times. I wouldn't be alarmed to paddle here in a slightly lower flow but due to the groundings I would recommend a slightly higher flow, somewhere between 400 ML/day and 500 ML/day.

My second trip down was on a much higher flow, and I paddled both Tandou and Coonalhugga creek when the Darling was in minor flood, before the major floods of summer 2022/23.

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Tandou and Coonalhugga Creeks

The other two ways into the anabranch are a bit more complex and only flow when the lower Darling is in flood.