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The Lindsay, Mulcra and Wallpolla islands floodplain is characterised by a network of permanent waterways, small creeks and wetlands. The 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 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, generally referred to as locks. Water levels in the weir pools are managed primarily to provide safe navigation and adequate water levels for off-stream diversion via pumps. In recent years, the water level of weir pools 7 and 8 has also been managed to achieve ecological benefits in the Murray River channel, for example by lowering pool levels to increase the velocity of flowing water, which can support drift of golden and silver perch larvae when conditions are suitable for breeding.

Weir pool levels have a big effect on flows in Mullaroo Creek, the Lindsay River and Potterwalkagee Creek. When water levels in locks 7 and 8 are raised above the full supply level, flows to Potterwalkagee Creek increase and Lindsay River starts flowing. When weir pools are lowered, flows to both the Lindsay River and Potterwalkagee Creek cease. Mullaroo Creek is less-affected by weir pool levels and flows are controlled 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 to or beyond 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 flows 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 effectively.

Traditional Owners

System map

Environmental watering objectives in Lindsay, Wallpolla and Mulcra

Connected icon
Restore nutrient and carbon cycling between floodplains, floodplain wetlands and waterways to increase ecosystem productivity
Fish icon
Increase the abundance, diversity and distribution of native fish
Frog icon
Support frog populations
Insect icon
Support waterbug populations
Support turtle populations
Plant icon
Increase the abundance and diversity of wetland vegetation
bird icon
Increase the waterbird population by providing feeding and breeding habitat in floodplain wetlands

Environmental values

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

Mullaroo Creek and the Lindsay River support one of the most-significant populations of Murray cod in the lower Murray River. These waterways provide fast-flowing habitat that Murray cod favour, and contrast with the mostly slow-flowing and still habitats created by the nearby Murray River weir pools. Fish in Mullaroo Creek and Lindsay River breed and produce juveniles that colonise other parts of the Murray system. 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 has degraded the water-dependent vegetation communities throughout the Lindsay, Mulcra and Wallpolla island system, which has in turn reduced the diversity and abundance of animals that rely on healthy vegetation
for habitat.

Traditional Owner cultural values and uses

Mallee CMA has met on Country with Traditional Owners of Lindsay, Mulcra and Wallpolla islands and the First People of the Millewa-Mallee Aboriginal Corporation (representing Latji Latji, Ngintait, Nyeri Nyeri and Wergaia Traditional Owners) to discuss watering requirements for their Country. After much discussion, Elders’ key focus was to support Country to recover from the ravages of drought. Their recommendations for watering actions have shaped the environmental water planning for 2020–21.

Social, recreational and economic values and uses

In planning the potential watering actions in Table 1, Mallee CMA has also considered how environmental flows could support other values and uses such as:

  • water-based recreation (such as kayaking, fishing and swimming)
  • riverside recreation and amenity (such as walking, camping, birdwatching and relaxing with friends and family)
  • community events and tourism (such as school education programs, commercial tours and citizen science projects)
  • socio-economic benefits (such as apiarists, local businesses such as accommodation and shops).

If the timing or management of planned environmental flows may be modified to align with a community benefit, this is acknowledged in Table 1 with an icon.

Fishing icons

Watering planned to support angling activities

Native recreational fish species that are stocked into recently wetted wetlands can undergo rapid growth and achieve high survival rates. In March 2019, the Victorian Fisheries Authority conducted a trial in partnership with First People of the Millewa-Mallee Aboriginal Corporation and Mallee CMA that released 120,000 juvenile golden perch and silver perch to Wallpolla Horseshoe Lagoon.

In order to protect the juvenile perch, water will be delivered to the lagoon as a series of top-ups as required in spring and autumn, as part of the regular environmental water deliveries to support the naturally occurring environmental values of the site (such as fish and aquatic vegetation).

The stocked native fish are expected to benefit from environmental watering at Wallpolla Horseshoe Lagoon without compromising the primary watering objectives for the site. Once the fish have grown to a suitable size, they will be released into the Murray River to contribute to the regional populations and provide opportunities for anglers.

Recent conditions

Weather observations at Lake Victoria — the nearest weather station to Lindsay, Mulcra and Wallpolla islands — ndicate there was below-average rainfall and above-average temperatures in the region during 2019–20. The average maximum temperature at Lake Victoria during 2019–20 was less than in the previous year, but long-term data indicates that temperatures have increased over the previous 10 years. Monthly rainfall totals were substantially below average for the year.

The 2019–20 year was mostly dry in the entire Murray River valley and major upstream tributaries (such as the Goulburn and Murrumbidgee rivers). There were no spills from major upstream storages, and the magnitudes of operational flows and environmental flows that were released in the Murray system were well below the threshold required to provide flows to wetlands and floodplains at Lindsay, Mulcra and Wallpolla islands. Summer floods in northern New South Wales (NSW) and Queensland provided flow in the Darling River and in April 2020 the Darling River provided substantial flow to the Murray River for the first time in more than two years. This inflow was well below the magnitude needed to wet Lindsay, Mulcra and Wallpolla islands.

All of the high-priority potential watering actions were delivered during 2019–20. These included year-round flows to maintain fish habitat in Mullaroo Creek and spring high flows in Mullaroo Creek, Potterwalkagee Creek and the upper reaches of the Lindsay River to help native fish disperse, spawn and recruit. Water for the environment was also pumped to wetlands and creeks on Wallpolla Island in spring and autumn, to improve vegetation condition and provide habitat for waterbirds and fish.

Scope of environmental watering

Table 1 Potential environmental watering actions and objectives for Lindsay, Wallpolla and Mulcra islands

Potential environmental
watering action

Functional watering objective Environmental

Environmental objective

Lindsay Island – Mullaroo Creek

Year-round low flow (minimum of 600 ML/day)

  • Maintain fast-flowing habitat for native fish (such as Murray cod, silver perch and golden perch)
  • Maintain habitat for aquatic vegetation and maintain soil moisture to maintain the condition of streamside vegetation
Fish iconPlant icon

Spring fresh (one fresh of up to 1,000-1,400 ML/day for three months during September to November)

  • Cue fish movement and spawning and improve recruitment opportunities for native fish

Fish icon

Lindsay Island – Lindsay River
Spring/summer fresh (one fresh of 65-200 ML/day via the northern regulator and one fresh of 20-200 ML/day via the southern regulator for a maximum of four months during September to December)
  • Provide temporary flowing water to reconnect pools and support dispersal, spawning and recruitment opportunities for native fish
  • Wet the substrate and debris (snags) close to the bank to promote the growth of biofilms, which provide a food source for animals higher in the food chain

Fish iconJigsaw icon

Autumn/winter fresh (one fresh of 130 ML/day via the northern regulator and 90 ML/day via the outhern regulator for two months during May to June)
  • Wet the substrate and debris (snags) close to the bank to promote the growth of biofilms, which provide a food source for animals higher in the food chain1

Jigsaw icon

Lindsay Island wetlands
Websters Lagoon (complete fill in spring)
  • Provide a connection between Websters Lagoon and the Murray River to allow the exchange of carbon, nutrients and fish between the wetland and the river
  • Provide conditions for lake bed herbaceous plants and semi-aquatic plants in the littoral zone to grow in the drying phase after watering
  • Provide variable water levels in the littoral zone to provide feeding habitat for shorebirds
  • Provide open-water habitat as refuge and feeding and breeding habitat for waterbirds

Fish iconJigsaw iconPlant icon

Scotties Billabong (complete fill in spring)
  • Provide shallow-water habitat to provide foraging and breeding opportunities for frogs
  • Stimulate the growth of streamside and instream vegetation
  • Provide conditions for lake bed herbaceous plants to grow in the drying phase after watering

Frog iconPlant icon

Wetland 33 (complete fill in spring)
  • Fill to the wetland fringe to increase growth of shrubs and lignum on the wetland fringe
  • Provide shallow-water habitat and open-water habitat to create foraging opportunities for waterbirds, frogs and turtles
  • Provide conditions for lake bed herbaceous plants to grow in the drying phase after watering

Frog iconTurtle iconPlant iconHeron icon

Lindsay-Mullaroo connector (complete fill in spring)
  • Provide a temporary connection to the Lindsay River to allow the exchange of nutrient, carbon and plant propagules
  • Provide conditions for lake bed herbaceous plants and semi-aquatic plants to grow in the littoral zone in the drying phase after watering
  • Stimulate the growth of severely stressed streamside vegetation

Jigsaw iconPlant icon

Crankhandle (complete fill in spring)
  • Provide shallow-water habitat to provide foraging and breeding opportunities for frogs
  • Provide conditions for lake bed herbaceous plants to grow in the drying phase after watering
  • Fill to the wetland fringe to increase the growth of shrubs and lignum on the wetland fringe

Frog iconPlant icon

Lake Wallawalla (partial fill in autumn/winter)
  • Provide shallow-water habitat, open-water habitat and shoreline habitat to create foraging opportunities for waterbirds, frogs and turtles
  • Break the dormancy of yabbies so they emerge from burrows, feed and reproduce
  • Provide conditions for lake bed herbaceous plants to grow in the drying phase after watering

Frog iconTurtle iconPlant iconHeron iconInsect icon

Mulcra Island – Potterwalkagee Creek
Winter/spring fresh (one fresh of 90-475 ML/day via the Stoney Crossing regulator and 440 ML/day via the upper Potterwalkagee Creek regulator for a maximum of five months during September to November)
  • Provide temporary flowing water to reconnect pools and support dispersal, spawning and recruitment opportunities for native fish
  • Wet the substrate and debris (snags) close to the bank to promote the growth of biofilms, which provide a food source for animals higher in the food chain
  • Maintain soil moisture to maintain the condition of streamside vegetation

Fish iconJigsaw iconPlant icon

Mulcra Island – wetlands
Mulcra Horseshoe (complete fill in spring)
  • Provide shallow-water habitat and open-water habitat to create foraging and breeding opportunities for waterbirds, frogs and turtles
  • Provide a connection to the Murray River to support dispersal, spawning and recruitment opportunities for native fish
  • Stimulate the growth of emergent, aquatic and streamside vegetation
  • Provide a connection to the Murray River to allow the exchange of carbon, nutrients between the floodplain and the river

Fish iconFrog iconJigsaw iconTurtle iconPlant iconHeron icon

Mulcra Island floodplain (floodplain inundation in spring)
  • Stimulate the growth of emergent, aquatic and streamside vegetation
  • Provide shallow-water habitat and open-water habitat to create foraging and breeding opportunities for waterbirds, frogs and turtles
  • Support fish spawning events and provide temporary habitat for juvenile fish

Fish iconFrog iconTurtle iconPlant iconHeron icon

Snake Lagoon (complete fill on spring)
  • Stimulate growth of emergent, aquatic and streamside vegetation
  • Provide conditions for lake bed herbaceous plants to grow in the drying phase after watering

Plant icon

Wallpolla Island
Wallpolla Horseshoe Lagoon (partial or complete fill in spring/autumn)

Fishing icon

  • Wet/drown river red gum saplings in the bed of Wallpolla Horseshoe to limit their coverage
  • Provide suitable breeding conditions for waterbirds
  • Provide shallow-water habitat and open-water habitat to create foraging and breeding opportunities for waterbirds, frogs and turtles
  • Provide the conditions for lake bed herbaceous plants and semi-aquatic plants to grow in the littoral zone during the drying phase after watering
  • Provide nursery habitat for naturally occurring fish populations and juvenile golden perch and silver perch stocked by Victorian Fisheries Authority to increase growth rates before fish are released to the Murray River

Fish iconFrog iconTurtle iconPlant iconHeron icon

Finnigans Creek (low flow in spring)
  • Provide connections between Wallpolla East, Sandy Creek and Finnigans Creek to allow nutrient exchange, increased wetland productivity and the dispersal of plant propagules
  • Provide variable water levels in the littoral zone to improve wetland productivity and promote the growth of native aquatic and fringing plants
  • Provide variable water levels in the littoral zone to provide feeding habitat for shorebirds
  • Provide open-water habitat to create foraging opportunities for waterbirds

Jigsaw iconPlant iconHeron icon

Sandy Creek (low flow in winter/spring)
Wallpolla Creek East (low flow in winter/spring)

Engagement

Table 2 shows the partners and stakeholder organisation with which Mallee CMA engaged when preparing the Lindsay, Mulcra and Wallpolla islands seasonal watering proposal.

Seasonal watering proposals are informed by longer-term regional catchment strategies, regional waterway strategies, environmental flow studies, water management plans and other studies. These incorporate a range of environmental, cultural, social and economic perspectives and longerterm integrated catchment and waterway management objectives. For further details, refer to the Mallee Regional Catchment Strategy and Mallee Waterway Strategy.

Table 2 Partners and stakeholders engaged in developing the Lindsay, Mulcra and Wallpolla islands seasonal watering proposal

Partner and stakeholder engagement

  • OzFish Unlimited
  • Community members on the Mallee CMA Land and Water Advisory Committee
  • Local Landcare groups
  • Commonwealth Environmental Water Office
  • Murray-Darling Basin Authority (the Living Murray program)
  • NSW Department of Planning Industry and Environment
  • Parks Victoria
  • SA Water
  • Department of Environment Land, Water and Planning (Fire Forest and Regions)
  • Department of Environment Land, Water and Planning (Water and Catchments)
  • Lower Murray Water
  • Mildura Rural City Council
  • Victorian Fisheries Authority
  • Neighbouring landholder
  • Lindsay Point irrigators
  • Mallee Tours
  • Murray Offroad Adventures
  • Wild Side Outdoors
  • Sunraysia Apiarist Association
  • Birdlife Mildura
  • Sunraysia Bushwalkers
  • Sunraysia 4WD Club
  • Mildura Information Centre
  • Visit Mildura
  • Mallee CMA Land and Water Advisory Committee
  • Traditional owners of Lindsay-Mulcra-Wallpolla
  • First People of the Millewa-Mallee Aboriginal Corporation

Page last updated: 24/07/20