While the River Murray is doing better today thanks to work by lots of people to help it recover after the Millennium Drought, there are still issues occurring that can affect its health.
South Australia and the River Murray have endured multiple droughts throughout history. In earlier years, before dams were built along the river, dry times and drought meant the river could be reduced to a few pools, and sometimes the flow would stop altogether.
While the Millennium Drought broke in 2010, we are still dealing with the effects. The drought saw the lowest flows into South Australia in recorded history, causing untold damage to communities. Recovery has been good, but there is still more to be done. And we must always be prepared for any potential future droughts.
While drought is definitely something to be concerned about, at the other end of the spectrum is flooding. Flooding is definitely a case of too much of something (rain) not being a good thing.
South Australia’s worst flood occurred in 1956, when water levels reached 12.3 metres at Morgan.
DEWNR is the Hazard Leader for flood and riverbank collapse in South Australia. We work with other agencies to assess risks and prepare the community in case of flooding.
Late in 2016, thanks to a very wet winter, the river experienced what are known as high flows. The extra rainfall increased the amount of water coming down the river, which was great news for many, although some shacks and river properties were inundated with water. . Farmers received all the water allocated to them, more people were visiting the river to take part in the activities, and the environment received a welcome boost.
One of the less-welcome side effects of high flows can be blackwater. Blackwater events are a natural phenomenon that occur when areas that don’t see much water are inundated due to the high flows. This stirs up the organic matter like leaves and wood and washes down the river. This results in low dissolved oxygen levels, making the water darker in colour and often quite smelly. In some instances it can cause distress to fish as well as skin irritations for people who come into contact with the water.
Blackwater is a temporary event and can eventually result in the increase of food sources for fish from the increased carbon in the water.
Salinity occurs when there is too much salt in the water. Too much salt can affect the quality of the soil, as well as create health problems for the plants and animals that rely on the river for survival.
Salinity factsheet (MDBA)
Over the years, the amount of farming along the river has increased dramatically. Increased farming means increased amounts of water allocated to those who need it to water their crops. While farming definitely plays a crucial role in society, the increase, combined with changes in our weather systems has resulted in less water being available for the environment.
To help deal with this, part of river management includes delivering environmental water to areas in need. Environmental water is exactly what it sounds like – water held specifically for environmental benefit. The water goes to places like floodplains and wetlands to improve their condition and encouraging the increase of plant and animal life.
Pests and weeds
Not all the plants and animals that live along the river are its friend. There are many pest weeds and animals that can threaten the health of the river and the surrounding areas. Not only that, but they can affect the land of farmers, damaging crops and reducing output.
Work to manage pests includes eradication programs, workshops with landholders to educate on pest management and reporting them to the appropriate authorities.
This video explains how pests are being managed in the Coorong, Lower Lakes and Murray Mouth area:
Pest animals in the SA Murray-Darling Basin region
Pest plants in the SA Murray-Darling Basin region
The overpopulation of carp in Australia has been an ongoing problem for some years. They overwhelm the system and reduce the health of the river as well as the other creatures that inhabit the river.
The Federal Government has been discussing ways to reduce the carp population. They are working on a plan to release a virus into the river that is fatal to carp, but won’t harm the other animals or plants, or affect the water for humans.
The project is still being discussed, as there are many factors to take into consideration, such as how the virus will be distributed, how many carp it will affect, and how to remove the dead carp after the virus has taken effect.
Carp control in the River Murray
Carp: Villians or victims
Factsheet – Carp control in the River Murray
National Carp Control Plan
Department of Agriculture and Water Resources
Invasive Animals Cooperative Research Centre
Reclaiming our rivers from feral carp (CSIRO)
About the Tri-State Murray NRM Regional Alliance
Carp information (NSW Department of Primary Industries)
Locks, weirs and barrages
As the use of irrigation in farming increased along the river, so did the amount of water being taken from the river. After the River Murray Commission was established in 1917, structures known as weirs and locks were built along the river to help manage the water that was being taken. The weirs help to:
- store water and regulate river flow
- provide a higher river level to improve the river's navigability
The locks allow boats and other vessels to travel through the weirs.
Weir pools are the water stored behind the weirs, and their water levels can be altered to help divert water for agricultural, town and industrial use.
There are five barrages located near the top of Coorong National Park. The barrages help to reduce or restrict the flow of water out to the sea, so we don't lose the water during times of lower flows. They also help to reduce salinity in the lower part of the river and the Lower Lakes
History of the Lakes
Locks, weirs, dams and barrages
MDBA - Weirs and locks
Factsheet – All about the barrages
Lower Lakes barrages