Work is underway to improve the health and resilience of the River Murray’s inland wetlands and floodplains.
Many years of water over-allocation and river regulation have meant a decline in the health of the River Murray, exacerbated by an extended period of drought – known as the millennium drought – across the Murray-Darling Basin.
Wetland and floodplain habitats have been hit hard. Vegetation, including many majestic river red gums, have been severely stressed. Animals have also been affected with numbers of native fish, such as the iconic Murray cod and Murray hardyhead, dwindling.
The problem? Not enough water has been coming down the Lower Murray to meet the environment’s requirements.
Why we’re taking action
The River Murray‘s many locks, weirs, barrages and upstream storages have provided greater security of water for human consumption. But these structures have divided the river into unconnected sections, which significantly affects seasonal and annual variations in water flows.
Before the structures were introduced, the majority of wetlands and floodplains received highly variable flows, with intermittent dry and wet periods. They needed – and still do need – irregular but frequent flooding to replenish soil moisture and flush salt from soils. This enables floodplain plants and animals to survive and flourish.
Now, each section of the river is maintained at stable water levels, or pools, with the base flow river level usually higher than before weir construction began in the 1920s. This, along with increasing extraction of water from the system, has permanently altered environmental flows from the river to adjacent floodplains, anabranches and wetlands.
Some wetlands and many of the floodplains are now above the regulated water level and have inundation patterns that are too short and infrequent. In contrast, 87 per cent of wetlands are now permanently inundated; their inlets connect to the river below the regulated level.
Constant inundation and stable water levels have:
- restricted nature’s regeneration processes
- impeded natural nutrient cycles
- caused a decline in the diversity and extent of habitats, flora and fauna
- caused some exotic species, such as the common carp, to thrive because they favour unnatural, permanent inundation, placing further strain on wetlands.