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River flows and connectivity

River flows connect different habitats for water-dependent animals and plants. Murray–Darling Basin rivers connect wetlands, floodplains, upstream and downstream habitats and the Southern Ocean. River regulation, or the control of water flow, has reduced the size and frequency of river flows that connect rivers with floodplains and the sea. Physical barriers, like weirs, dams and barrages, now prevent the movement of fish and other species up and down the river.

Returning parts of the natural flow pattern is a central element of river restoration and a concept adopted by the Basin Plan to restore and protect environmental assets and functions.

Basin annual environmental watering priorities for river flows and connectivity

The Basin-wide environmental watering strategy outlines the objectives to improve river flows and connectivity along rivers and out to floodplains and the Murray Mouth.

Annual environmental watering priorities for 2018-19

  • support opportunities for lateral connectivity between the river and adjacent low-lying floodplains and wetlands to reinstate natural nutrient and carbon cycling processes.
  • coordinate replenishment flows across multiple tributaries to maintain habitat condition and regulate water quality, carbon and nutrients in refuges along the Barwon–Darling watercourse.
  • maintain seasonally appropriate water levels, support a suitable salinity gradient in the Coorong, provide regular flows for fish movement and salt export through the barrages.

The annual environmental watering priorities are the focus for the current year and are small steps in the short term to achieve the multi-year watering priorities in the long term.

Multi-year environmental watering priorities

The annual environmental watering priorities support multi-year environmental watering priorities that remain in focus over a number of years to achieve long term outcomes. Multi-year watering provides and relies on cumulative progress over time, e.g. watering in one year may only wet a dry riverbed, but follow up watering the next year provides more water to fill the river and reach wetlands either side of the river where it waters plants and animals.

More information


The multi-year priorities are listed below:
Support lateral and longitudinal connectivity along the river systems

Many plants and animals in the Basin rely on river flows for water, food and habitat as well as to support the cycle of wetting and drying that underpins various stages of their life cycle.

Flows that reconnect main river channels with river tributaries (longitudinal connectivity) restore health to river systems by enabling animals to move, supporting nutrient and carbon cycling, and flushing salt downstream.

Connectivity between main river channels, wetlands and floodplains (lateral connectivity) restores river health by providing water to ecosystems for habitat, cycling nutrients through the river system, and providing natural cues for feeding, breeding and movement, which underpins the food web.

Support freshwater connectivity through the Lower Lakes, Coorong and Murray Mouth

The priority for river flows and connectivity is to improve connectivity between freshwater, estuarine and marine environments and to improve habitat conditions in the Coorong by optimising and managing inflows through the Lower Lakes and Murray Mouth.

The Coorong, Lower Lakes and Murray Mouth

The Coorong and Lakes Alexandrina and Albert (the Lower Lakes) is one of Australia’s largest wetland systems. It has 23 wetland types, covers 142,500 hectares and meets 8 of 9 criteria listed in the Ramsar Convention. It is an important feeding habitat for international migratory waterbirds. It also removes salt and sediment from the Basin through the Murray Mouth and allows native fish to move between marine, estuarine and freshwater environments.

Improving conditions in the Coorong requires a long-term approach. Many key species and ecological processes within the system need specific flow regimes over multiple years to begin to recover.

Connectivity between freshwater, estuarine and marine environments helps native fish move and migrate. This sustains populations and enables fish to complete life cycles in different aquatic environments. It is particularly important for diadromous fish - those which move between fresh and salt water to breed. Some of these fish are congolli, common galaxias, short-headed lamprey and pouched lamprey.


The salinity of the Coorong generally increases with distance from the Murray Mouth. This varies over time and in response to inflows from the River Murray through the Lower Lakes and barrages. It is also influenced by seawater flowing back through the Murray Mouth and into the Coorong.

Ensuring a salinity gradient exists along the length of the Coorong is vital for a diverse and healthy estuary and the broader ecology of the Coorong.

How does the MDBA decide where to water needs to be delivered?

Where and how much water for the environment is delivered depends on a number of different factors including climate (e.g. rainfall and soil moisture). These factors are measured by the Resource Availability Scenario. For more information visit the Resource Availability Scenario page.