Lindsay, Mulcra and Wallpolla islands

Latest information about where, when and why environmental water may be delivered to Lindsay, Mulcra and Wallpolla islands and the environmental objectives being targeted is available in this year’s seasonal watering plan.

The seasonal watering plan also contains information about how environmental flows could support cultural, social, recreational and economic values in Lindsay, Mulcra and Wallpolla islands.

Watering data for Lindsay, Mulcra and Wallpolla islands and the wider northern region is updated quarterly. Visit current watering releases to find out more.

To find out the current environmental water entitlements held by the VEWH in Lindsay, Mulcra and Wallpolla islands visit our water holdings.

Lindsay, Mulcra and Wallpolla islands are part of the Victorian Murray system.

Traditional Owners

First People of the Millewa-Mallee Aboriginal Corporation (FPMMAC) has a Recognition and Settlement Agreement with the Victorian Government and is a statutory authority for the management of Aboriginal heritage values and culture, under the Victorian Aboriginal Heritage Act 2006.

System overview

Lindsay, Mulcra and Wallpolla islands cover over 26,100 ha of Victorian floodplain in the Murray-Sunset National Park. They form part of the Chowilla Floodplain and Lindsay-Wallpolla islands icon site that straddles the Victoria–South Australia-New South Wales border in the mid-Murray River system.

A network of permanent waterways, small creeks and wetlands characterises the Lindsay, Mulcra and Wallpolla islands floodplain. Lindsay River, Potterwalkagee Creek and Wallpolla Creek form the southern boundaries of the site and create large floodplain islands with the Murray River to the north.

In their natural state, these waterways and wetlands would regularly flow and fill in response to high water levels in the Murray River. Large floods still occur, but major storages in the upper reaches of the Murray River system and extraction for consumptive use have reduced the frequency of small to moderate-sized floods.

Flows in the mid-Murray River system are regulated through a series of weir pools. The weir pools are named after the locks that form part of the infrastructure at the weirs that allow vessels to navigate from one weir pool to the next. The weir pools are primarily managed as small water storages to ensure adequate water levels for off-stream diversion via pumps and regulated channels.

Water is diverted from the Lock 9 weir pool in the Murray River to Lake Victoria, where it is stored for later use to meet South Australia’s water demands. The diversion causes water to bypass Murray River locks 7 and 8 weir pools, and at times it can greatly affect the flow in those reaches.

In recent years, water levels in locks 7 and 8 weir pools have been managed to achieve environmental benefits in the Murray River channel. For example, weir pool levels have been raised during winter and spring and lowered during summer and autumn to mimic the seasonal river flow. The raising and lowering provide greater environmental benefits than a stable weir pool because it wets and dries off-channel habitats and creates more variable flow patterns in the Murray River and connected floodplain streams. Changes in water levels during appropriate seasons help establish fringing vegetation in shallow margins of the river channel and promote the cycling of nutrients and carbon as conditions fluctuate between wet and dry.

Static weir pool levels and reduced Murray River flow significantly affect the Lindsay River and Potterwalkagee Creek flows. When the natural flow increases and/or water levels in locks 7 and 8 weir pools are raised above the full supply level, the upper Lindsay River starts flowing (Lock 7) and the flow to Potterwalkagee Creek increases (Lock 8). When weir pools are lowered, flow to the upper Lindsay River and Potterwalkagee Creek ceases. Mullaroo Creek on Lindsay Island is less affected by weir pool levels, and flow is controlled independently through the Mullaroo Creek regulator, which connects the creek and the Murray River. Moderate lowering of the Lock 7 weir pool level has little effect on Mullaroo Creek, but lowering more than 0.5 m below full supply level makes it difficult to deliver the recommended minimum flow of 600 ML per day that is required to maintain fast-flowing habitat for native fish, especially Murray cod.

Fluctuation of weir pool levels is a major consideration for jurisdictions managing the flow in the Murray River and the anabranch waterways of Lindsay, Mulcra and Wallpolla islands. Environmental objectives and associated water regimes for the Murray River sometimes conflict with those for the Lindsay, Mulcra and Wallpolla anabranch systems. Responsible agencies in Victoria and NSW and the Murray-Darling Basin Authority collaboratively plan how to manage weir pools and flows to floodplain habitats effectively.

Environmental values

The Lindsay, Mulcra and Wallpolla islands represent three separate anabranch systems that contain various streams, billabongs, large wetlands and swamps. When flooded, waterways and wetlands within these systems provide habitat for native fish, frogs, turtles, waterbirds and water-dependent plants. Terrestrial animals (such as woodland birds) also benefit from improved productivity and food resources when anabranch systems are inundated. Large floodplain wetlands (such as Lake Wallawalla) can retain water for several years after receiving inflows; they provide important refuges for wetland-dependent species and support terrestrial animals (such as small mammals and reptiles).

Mullaroo Creek supports one of the most significant populations of Murray cod in the mid-Murray River system. Mullaroo Creek provides a fast-flowing habitat that Murray cod favour, contrasting with the artificially slow-flowing and still habitats in the nearby Murray River weir pools. Fish in Mullaroo Creek breed and produce juveniles that contribute to populations in adjacent parts of the Murray system (such as in the Darling River in NSW and the lower Murray River in South Australia). Waterways and wetlands throughout the icon site support several other fish species, including freshwater catfish, golden perch, silver perch, Murray-Darling rainbowfish and unspecked hardyhead.

The reduced frequency and duration of floods in the Murray River have degraded the water-dependent vegetation communities throughout the Lindsay, Mulcra and Wallpolla island system, reducing the diversity and abundance of animals that rely on healthy vegetation for habitat.

Page last updated: 05/12/24