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Securing the Future of Cockatoo Lagoon

Securing the Future of Cockatoo Lagoon

Cockatoo Lagoon is a natural billabong of the Gunbower Creek. Before European occupation, water levels in Cockatoo Lagoon would have fluctuated with wet and dry periods.

A permanent pool was most likely retained in the deeper sections, with total drying occurring in periods of extended drought. Since the 1920s, Cockatoo Lagoon has been used as part of the Gunbower Creek irrigation system.

Thompsons Weir, located about 6 km downstream of Cockatoo Lagoon, provides a stable water level for Cockatoo Lagoon, keeping the lagoon full for most of the year.


Recent ecological investigations have shown the lagoon is in a state of significant decline.

The lagoon has lost many of its native species, including reduced numbers of freshwater catfish, turtles and platypus, and is dominated by the aquatic weed pale yellow water lily.

A century of operating the system to allow irrigation has also resulted in Cockatoo Lagoon silting up, causing it to shallow out, making it harder to pump from in some places, and allowing pale yellow water lily to flourish.

As time goes on, the silt problem is only going to get worse, making it harder, and more costly, to access water for irrigation and providing more area for aquatic weeds, like the pale yellow water lily, to flourish.

Gunbower Creek is a natural waterway and therefore is constantly changing. Use of the creek to deliver water for irrigation for more than 100 years, and more recently for the environment, has impacted changes in the creek such as erosion and sediment transportation.

These changes to the creek limit the ability to pass large volumes of water. Goulburn-Murray Water (GMW) is currently managing the creek at a maximum flow of approximately 800 ML/day. This volume is not enough to deliver the full suite of demands that may be placed on the creek, including all irrigation allocations even in the absence of environmental water needs.

This means that during peak demand periods, water in the creek may need to be rationed.

Removing Thompsons Weir would reduce connectivity between Gunbower Creek and Cockatoo Lagoon. This could impact upon landholders’ ability to draw water from Cockatoo Lagoon. GMW is working with these landholders to investigate alternative supply options to ensure they can continue to access water.

This project provides a number of opportunities including:

  • Increasing capacity in Gunbower Creek to ensure all customers can access water during peak demand
  • Securing long-term supply and improving water quality for Cockatoo Lagoon irrigators; and
  • Maintaining and restoring the ecological values of Cockatoo Lagoon.

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