Lower River Murray in South Australia. Photo: Tanya Doody
The Lower Murray-Darling region contains diverse and rich natural environments. Its waterways provide water for domestic use, and support diverse agriculture, tourism and recreational activities, and Aboriginal cultural values and practices.
The Lower Murray-Darling’s river system, its floodplains, swamps and wetlands, provide habitat for threatened animals including the Regent parrot and Australasian bittern, Murray cod, Murray hardyhead, silver perch, southern bell frog and Murray River tortoise.
The region also features a number of internationally significant wetlands including the Coorong, and Lakes Alexandrina and Albert Wetlands, the Riverland complex, Banrock Station and Hattah-Kulkyne Lakes.
For more information, please see the Commonwealth Environmental Water Management Plan 2021-22.
What has environmental water achieved in the Lower Murray-Darling?
Monitoring shows that water delivered to the Lower Murray-Darling river system is supporting food, habitat and breeding opportunities for many of the region’s unique plants and animals.
A summary of results to date are below, with further detail and full monitoring reports available on the monitoring page.
Summary of findings to date
Monitoring in the Lower Murray River identified a number of key outcomes achieved due to environmental water delivery over the period 2014-15 to 2020-21:
- ‘Flowing water’ habitat (greater than 0.3 metres per second) increased in area, and water levels were more variable. More flowing water benefits native plants and animals that are adapted to a riverine environment.
- Variable water levels increased areas of inundation, improving river bank plant health and diversity. Variable water levels can also increase the diversity of biofilms, which are a key component of riverine food webs.
- Flows through the barrages to the Coorong were almost continuous throughout all years, maintaining a connection between the river and the Coorong estuary to support a functioning river system.
- Environmental water substantially increased salt export out of the Basin, reduced salt import into the Coorong and reduced salinity concentrations in the Coorong. This was crucial in maintaining estuarine habitats, species diversity and ecosystem functions.
- In the river channel, food production and consumption, and transport of nutrients and phytoplankton all increased. Greater primary production provides more food to aquatic food webs (e.g. for invertebrates and fish). Transported food resources from the river also benefit food webs in the Lower Lakes and the Coorong.
- The likelihood of low oxygen levels (e.g. <5 milligrams per litre, mg/L) during spring-summer was reduced due to increased water mixing and oxygen exchange from environmental water delivery. Aquatic animals generally need oxygen levels above 5 mg/L. particularly during spring-summer, which is the main reproductive season of many species.
- Microinvertebrates from upstream sources (e.g. Goulburn River/southern Basin) were transported to the Lower Murray River, which contributed to increased amounts (density) and variety (diversity) and potentially provided a more diverse food source for larger animals (e.g. fish).
- Murray cod populations in the Lower Murray have increased following several strong recruitment events, potentially supported by the increased extent of flowing water habitat during the spawning/early larval period, and increased larval food resources.
- Populations of diadromous fish species including lamprey and congolli have increased, likely due to the continuous flow and connection between the River Murray, Lower Lakes and the Coorong.
- Spawning of golden and silver perch has occurred in the Lower Murray River, however, there has been little evidence of successful ‘recruitment’, i.e. survival to juvenile stage, and consequently minimal contribution to the broader population. This is largely due to prolonged low flows that do not provide appropriate nursery habitat. The current golden perch population in the Lower Murray is dominated by eight to ten year old fish (spawned in the Lower Murray and the Darling), with negligible recruitment from the last eight years.
- Targeted pumping of environmental water for southern bell frogs in South Australian wetlands has been successful in increasing breeding and abundance of this nationally threatened frog.
Fish monitoring in the Lower Darling and Coorong. Photos: Craig Bravery and CEWO
Commonwealth environmental water use is planned, delivered and managed in partnership with a number of individuals and organisations in the Lower Murray-Darling, including:
- NSW Department of Planning, Industry and Environment
- Lower Murray Water
- New South Wales Department of Primary Industries – Fisheries
- Murray Local Land Services
- Western Local Land Services
- Victorian Environmental Water Holder
- Goulburn-Murray Water
- Mallee Catchment Management Authority
- South Australian Department for Environment and Water
- Murraylands and Riverland Landscape Board
- SA Water
- Nature Foundation
- Banrock Station
- Renmark Irrigation Trust
- Australian Landscape Trust
- Murray Darling Wetlands Working Group Ltd
- Tar-Ru Lands Board of Management
- Local councils and planning groups
- Private landholders
- Murray-Darling Basin Authority
Chalka Creek within the Hattah Lakes complex. Photo: CEWO