You would be right to believe that critical environmental and human needs for water have the highest priority to access to water in the rules that manage the Wambuul-Macquarie River… on paper, yes, the environment has the highest priority. But in reality, on the ground, the rules are applied in such a way so that irrigation gets looked after first – even after last summers crippling drought.
Supplementary access was announced – when the first flows arrived in the Macquarie in mid February 2020, the peak of the first flows was allowed to be pumped. The critical environmental and human needs downstream were ignored.
Floodplain harvesting is enormous – the diversion of overland flows into private dams by levy’s – held back an unknown, unmeasured volume of water. So much water, that flows that began in February didn’t reach the northern parts of the burnt North Marsh reed bed until the end of April. Healthy Rivers Dubbo conservatively estimates from the pieces of information available that around 70 to 90 GL ( 1 GL = 1 billion litres) was taken from the floodplains in the Macquarie this year (for scale Dubbo uses 8 GL a year from the river).
Remember the summer of 2019/20 in the Macquarie Valley?
The sharp severity of the drought was unprecedented. The Warren weir was raised by WaterNSW stopping flows beyond. Downstream, the river rapidly dried up to a series of disconnected green pools.
Insurance populations of turtles and fish were rescued from the river and secured in hatcheries by environmental agencies. Despite commendable efforts from the recreational fishing community to rescue as many fish as possible, mass fish deaths resulted.
The Macquarie Marshes were parched. There hadn’t been any surface water in the core Marsh since January 2019. The impact of years of ‘tight’ river management was evident – there was far less water around, and it disappeared very quickly.
Critical human need and stock and domestic requirements were not being met along the River and creeks downstream of Warren. There was a shocking loss of wildlife as a result. Mobs of kangaroos perished, many 50 year old plus turtles died, and we lost some of the oldest mussels known to exist in our fresh water rivers. The loss of vegetation meant less habitat for many and varied water dependent animals, fish and birds.
The North Marsh reed bed (the largest reed bed in the Murray Darling Basin) caught a lightning strike in October 2019 and about 4,000 ha was burnt. The reed beds needed flood water ASAP. While the reeds shot up after some rain fall that summer, they were using what little precious reserves their rhizomes held, making floodwater even more critical to their recovery.
The Drought Breaks
The flows came in February 2020, entering the Macquarie in several events through the Bell, Little and Talbragar Rivers – all of which are downstream of Burrendong Dam.
Shockingly, the first announcement of supplementary access was made on the 20th February, leading to over 12 GL being pumped from the vital first flow peak. The peak of the flow was taken, that meant that the area of wetland that potentially could have been inundated by the first flow was greatly reduced.
The shape of the hydrograph matters. The same volume of water flowing down the river over longer period of time wouldn’t have had the same potential to inundate as many hectares as the water arriving in one peak flow. The value of the peak of the flow to the environment in this circumstance was exponentially higher than the same volume of subsequent inflows at lower daily flow rates.
From a combined total of 84 GL flow at the Baroona gauge near Narromine, by 5 March 2020, 22.3 GL of this first flow had been recorded at Marebone Weir, with only 7 GL reaching the northern Macquarie Marshes.
Some of the flow was diverted by WaterNSW to other streams to meet stock and domestic replenishment flows, and some was extracted under a supplementary announcement. Much of the flow also performed a valuable role of soaking into alluvial aquifers and soils, filling pools in the river and meeting riparian needs for stock and domestic supply under basic landholder rights. An unknown volume was diverted by levys, and even more water was prevented from entering the river from floodplain harvesting.
By 1/3/2020, not even 1,200 ha of the 4,000 ha burnt North Marsh Reed bed had been inundated.
Timing matters. The reed bed needed to get that flood water as early as possible, so they could take advantage of the warmer summer days and get some growth up to store energy in their rhizomes for winter. It was not until late April 2020 that flood water finally made it to the northern most part of the charred reed bed, and into the Lower Macquarie River.
Because of the delay in flows reaching all of the fire damaged reed bed, the requirement for environmental water in the Macquarie Marshes was still classified as HIGH as of autumn 2020.
Why was supplementary access allowed?
Supplementary access has the lowest priority of water access, and should only be allowed once critical human need, and stock and domestic requirements downstream had been met. The go ahead to pump and divert was given before critical human need, and stock and domestic requirements downstream had been actually met (only forecast to be met).
By tweaking a rule, allowing critical need to be forecast, the peak of the very first flow after the drought broke was given the highest priority. Lucky for everyone it rained again……
The critical need for water in Macquarie Marshes after the worst drought in recorded history was ignored by NSW DPIE Water, who even ignored their own environmental water management team.
How much water does floodplain harvesting take in the Macquarie?
Floodplain Harvesting takes water from the floodplain for free, the volumes are unmeasured and therefore unknown. Healthy Rivers Dubbo has put together some available information to conservatively estimate the volumes involved.
- From the Macquarie’s draft water resource plan, we know the the total on farm dam storage capacity in the valley is about 175 GL. Disregarding storage of off river schemes, and being very conservative, let’s say on farm dam storage close to the river that could catch water from the floodplain is about 70 to 90 GL.
- Water from drought breaking flows that started in February didn’t reach the northern most part of the Marshes until late April.
- When a third supplementary access event was announced in April, there was a relatively small amount of water extracted, indicating that the on-farm dams were already full of water.
Of course, this is an estimate, as the government still does not provide this information publicly. It could be even more then that.
I’ll just leave this here… last permanent trades in the Macquarie were $1,900 a ML, temporary trades were $200 a ML.
To the untrained eye (or those with conflicting vested interests), this spring the Marshes look green and healthy – but without the early arrival of the flows, damaging weeds like lippia have taken hold. How much of the 4,000 ha burnt reed bed will come back? Yet to be seen.
The real impact of the drought breaking flows being held back will be a scar on the landscape for many years.