Fish lacking oxygen
The blackwater events this season have resulted in significant stress and fish deaths in parts of the Murray system due to low oxygen levels in the water. It has also resulted in a fair bit of misinformation.
We’ve seen relatively widespread blackwater this season because the floods in parts of the Murray and its tributaries reached so far across the floodplain they mobilised up to 25 years worth of organic matter. An immense amount of leaves, wood, bark and other high-carbon material builds up over that many years.
In the not too distant past, these higher floodplains had had more regular flushing than the current river regulation and land practices allow. These days flushing away the build-up of matter is limited mainly to the lower floodplains through a complex process of environmental watering (it’s never a case of ‘simply adding water’). Regulated flooding of Barmah-Millewa and Gunbower forests prior to this year, for example, shifted carbon out of those areas and reduced the severity of this current event.
One thing that’s clear is environmental watering and works programs on the Murray did not give rise to the backwater we’re now seeing. In fact environmental watering goes a long way towards healthier ecosystems by flushing the lower floodplains.
The MDBA, local land and water managers, environmental water holders and scientists continue to devote a lot of effort to exploring the causes and impacts of blackwater. The investigation into the 2010-11 and other events found that actions such as regularly flushing carbon from the floodplains helps but that it is very difficult to prevent and manage large scale blackwater, particularly in river systems regulated to support development.
Right now these same people are working to mitigate the impact of this latest event.
Environmental water is being used to create pockets of refuge and dilution. Further, where possible we will re-aerate blackwater by spilling it over weirs when they are reinstated in the Murray and diverting it into wide, shallow lakes such as Lake Victoria.
The benefits of all this work are highly localised when you consider the size of the area affected, but worthwhile particularly for creating refuges to help fish populations recover across the system. If we want to limit blackwater events in the future, more frequent environmental watering of the lower floodplain is part of the answer.
Murray–Darling Basin Authority Environmental Management executive director
Violence is violence
Why do some people get angry when violence to humans is compared with violence to non-humans?
Whether you like it or not, Greg Park (Bleeding heart nonsense, 24/11), we are all animals and we all have the same capacity for suffering. And farmed animals suffer enormously as video footage that aired on the ABC news this week clearly showed.
In footage, secretly filmed at an Echuca abattoir, frightened animals were violently and repeatedly stabbed in the neck with the prongs of an electrified stunner. Apart from the pain, this would have made the stun ineffective thus leaving the animals still conscious as their throats were cut open. A pig was struck four times with a captive bolt gun. She thrashed and moaned. She was laughed at and sworn at. Then she was shot. Twice. Her ordeal lasted more than six agonising minutes. Over 1000 videos were sent to authorities cataloging abuses to cows, calves, goats and sheep.
The inescapable reality is that whenever animals are killed en masse in slaughterhouses, there will be suffering. It doesn't have to be this way and it shouldn't. because we don't require any animal products in our diet in order to be healthy and happy. If we truly believe we are "superior" to the other animals then lets prove it by treating them with superior compassion and mercy.