How long does it take to travel from south-west Queensland to the Murray Mouth in South Australia? If you’re a golden perch starting out in life right now, it could take just a few months, depending on how many detours you make along the way.
Not so long ago a fish would have met many dead-ends on such a trip, with the connections between rivers broken and floodplains all but dried up because of the 2019 drought.
At the moment much of the Murray–Darling Basin is awash, across the floodplains, down the rivers and in the lakes and wetlands.
The rain of the past two years has helped connect the different parts of the system. This broad-scale connectivity across Australia’s most complex river system has restored the natural highways that link the breeding grounds, nurseries, food sources and long-term habitat for golden perch and the rest of the Basin’s native wildlife.
Why connected rivers are important
Longitudinally, it means one river can flow from its source into the next river and into the next until it reaches the sea. A good example is the Tumut River which starts in the Australian Alps, flows into the Murrumbidgee, and joins the Murray which reaches the Southern Ocean.
Latitudinally, it means the land is also connected to the creeks and rivers, when rain falls and drains into the waterway or water rises out of the main channel and reaches out across the floodplain. In 2022, we’ve seen many examples of this in southern Queensland and northern NSW as floodwater has moved across the landscape into the Darling River and filled the Menindee Lakes in southwest NSW.
And there’s important connectivity that links the rivers with the vast aquifer system under the ground. This is the source of springs that is so important for ecosystems away from the rivers, not to mention the bore water many communities rely on. These systems need to be replenished by the slow, steady transfer of water through the ground.
The movement of water distributes nutrients, carbon and energy through all elements of the food web. It allows wildlife to migrate up and down the system to complete their lifecycle.
That golden perch starts as a fish egg in the Warrego River in southern Queensland, and it floats all the way down the Darling River, hatching along the way and ending up at an all-you-can-eat buffet in the Menindee Lakes. As a fat young fish, it heads into the Great Darling Anabranch system or the Lower Darling River before hitting the big channel of the Murray River. From there it could head upstream and end up in the Goulburn River in Victoria, or downstream to the Lower Lakes near the Murray Mouth. Either way, it’s quite a journey, helped by flowing rivers and the fish ladders at the locks and weirs.
Birds, like the ibis or spoonbill, often need a variety of habitats for their life cycle. They breed in the marshes and shallow lakes and then head off elsewhere seeking better food, or a better place to be, as we often do! When more wetlands and floodplains are connected, they provide more opportunities for different genetic groups to get together – and greater genetic diversity passed on through their offspring means as a species they are better able to survive when wet times return to drought.
Stranded rivers, isolated wetlands and disconnected floodplains are the result of broken connectivity. In the recent drought, water managers were able to step in by using water for the environment to create refuges that supported pockets of plants, fish and other creatures. This use of water for the environment meant a residual population of native species was there to spur on the recovery when the rain came again.
Keeping our rivers, wetlands and floodplains connected is a world-wide issue. Australia is doing it well compared to many other parts of the planet, with the Murray–Darling Basin Plan driving the work of governments and communities to keep a whole-of-Basin perspective. No one river exists in isolation and you can understand the reason why this connectivity is fundamental to the heath of all of us!
Read more about how the Basin Plan supports river connectivity and the creatures that rely on it.
World Water Week runs from 23 August to 1 September 2022.
