Floodplain harvesting
What is it and why is it a problem?
We want healthy rivers, and an important part of that is ensuring rivers receive inflows from their catchment.
The problem
Floodplain harvesting is the collection, extraction or impoundment of water flowing across floodplains. This practice is widespread in the northern Basin, where large upstream operators have constructed long levee banks and huge on farm dams to harvest floodplain flows and rainfall for their own profit at the expense of downstream communities and the environment. While now in the process of being licenced, the volume of water being taken is still largely unknown while the negative impacts of this practice has on river health are clear.
Floodplain harvesting takes water from the first rainfall and flows after a drought, denying the environment ‘first flush’ flows that are so important for ecological and cultural health. Diverting this water stops the medium sized floods that would normally pulse through the tributary rivers, bringing life into the Darling-Baaka River in between big flood events. This practice also denies Indigenous Nations rights to water downstream, which contradicts the priorities of the NSW Water Management Act and the Murray Darling Basin Plan.
The survival of rivers and their adjacent floodplains, wetlands, creeks and billabongs depends on these flows. Floodplain harvesting needs to be reduced to avoid further damage to ecosystems and communities downstream. This is particularly important in a drying climate. High levels of floodplain harvesting is killing the rivers of the northern Basin and leading to fish kills, algal blooms and poor water quality.
The volumes that are taken are unknown. Queensland reports floodplain harvesting volumes based on estimates. In 2023-24 the Queensland estimate was 215 GL. NSW does not report how much water is actually taken from rivers or floodplains.
Researchers have estimated that every year between 2004 and 2020, floodplain harvesting in northern NSW diverted an average of 778 gigalitres of water. That is more water than the entire population of Greater Sydney uses in a whole year. This water is kept in private storage dams that cover 42,650 hectares, an area roughly 65 times the size of the Melbourne CBD (Brown et. al. 2022).
To protect the health of our rivers, the Basin Plan enforces a legal limit on how much water can be extracted each year. In 2023-24, that limit was 11,807 gigalitres. On paper, it looked like we played by the rules, with only 11,064 gigalitres officially reported as taken. But there’s a massive loophole: that official figure doesn’t accurately account for floodplain harvesting in NSW. If we factor in the estimated 778 gigalitres of harvested floodplain water, the real total hits 11,842 gigalitres—pushing extractions over the legal limit. Simply put: until we accurately measure and report every drop taken by floodplain harvesting, we are flying blind, with no way to guarantee we are actually protecting our rivers.
The solution
We need to make major changes so that rivers are receiving the flows they need and commercial irrigators aren’t allowed to take more than their share, leaving the environment and downstream communities with nothing but fish kills.
Systems for licensing and regulating floodplain harvesting need to include the fresh rainfall that is captured before it can run into the rivers. Rainfall runoff capture makes up 44% of floodplain harvesting water take, and is mostly exempt from licensing in NSW. The rules that manage when floodplain harvesting can occur must change so that the volume of floodwater and rainfall that can be taken is reduced. And we need to more accurately measure the volume of water being taken by floodplain harvesting rather than using inaccurate estimates that do not show the full extent of the impact.
To reduce the impacts of floodplain harvesting we need to set targets that ensure floodplain harvesting cannot take place unless downstream environmental flow targets are being met. And we need to ensure floodplain harvesting cannot take place unless cultural responsibilities of Traditional Owners to care for Country are being met.
Photo credit: Max Phillips