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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 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 colloquially called locks, in reference to structures 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.

Water is diverted from weir pool 9 in the Murray River to Lake Victoria, where it is stored for later use to meet South Australian water demands. The diversion causes water to bypass Murray River weir pools 7 and 8, and at times it has a significant impact on flow in those reaches.

In recent years, the water levels in weir pools 7 and 8 have been managed to achieve ecological benefits in the Murray River channel. For example, weir pool levels have been raised during winter and spring then lowered during summer and autumn, to mimic seasonal river flows. 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 helps establish fringing vegetation in shallow margins of the river channel and promotes cycling of nutrients and carbon as conditions fluctuate between wet and dry.

Static weir pool levels and reduced flow in the Murray River have a big effect on flow in the Lindsay River and Potterwalkagee Creek. When natural flow increases and/or when water levels in weir pools 7 and 8 are raised above the full supply level, flow to Potterwalkagee Creek increase and the upper Lindsay River starts flowing. When weir pools are lowered, flow to both the Lindsay River and Potterwalkagee Creek cease. Mullaroo Creek 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 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 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 effectively manage weir pools and flows to floodplain habitats.

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, waterbirds and water-dependant 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 fast-flowing habitat that Murray cod favour, which contrasts 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, 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 the First People of the Millewa-Mallee Aboriginal Corporation (representing Latji Latji and Ngintait Traditional Owners) to discuss watering requirements for their Country.

The Traditional Owners have identified ways in which environmental water can support cultural values and uses, which are outlined in Table 1.

Table 1 cont: Traditional Owner values and uses of watering sites in the Lindsay Mulcra Wallpolla icon site

Waterway

Traditional Owner groupValues / Uses / Objectives / Opportunities
Lindsay IslandNgintaitBlack swan (Totem) nests in bull rush. Traditional Owners have observed a lack of bull rush around certain areas, so they would like to see it restored along the river banks, making for more nesting opportunities and a greater black swan population.
Lindsay IslandNgintaitThree-pronged grass are used for weaving. Traditional Owners are looking at places to plant seeds to grow this species, so elders can sit with community and teach weaving using the grass.
Lindsay-Mulcra- WallpollaNgintait/Latji LatjiOld Man Weed (Centipeda cunninghamii) is used for bush medicine. This grows in mud as water recedes. Both Traditional Owner groups from the Lindsay, Mulcra and Wallpolla region would like to see more of this.
Lindsay-Mulcra- WallpollaLatji LatjiLatji Latji would like more opportunities to get back onto Country and begin discussions about managing Country.
Lake WallawallaNgintaitProtection of Cultural Heritage sites bordering Lake Wallawalla.

Their recommendations for watering actions have shaped planning for water for the environment for 2021-22 and beyond.

Social, recreational and economic values and uses

In planning the potential watering actions in Table 2, Mallee CMA has also considered how environmental flows could support other values and uses such as:

  • water-based recreation (such as canoeing, kayaking, fishing and yabbying)
  • riverside recreation and amenity (such as bushwalking, camping, bird and wildlife watching, four-wheel driving and photography)
  • community events and tourism (such as increased visitation and ecotourism and education programs for school, TAFE and university students)
  • socio-economic benefits (such as for apiarists, local businesses providing accommodation and hospitality to tourists and local water delivery contractors).
Fishing icons

Watering planned to support angling activities

Wallpolla Horseshoe is currently being managed as a nursery habitat for native golden and silver perch, which were released as fingerlings into the wetland in March 2019. This was undertaken in partnership with First People of the Millewa-Mallee Aboriginal Corporation, Victorian Fisheries and Mallee CMA.

Delivery of water for the environment to Finnigans Creek will be targeted to provide a connection between Wallpolla Horseshoe and Finnigans Creek, with the intent of allowing dispersal of stocked native fish from Wallpolla East to Finnigans Creek and eventually to the Murray River via Wallpolla Creek. Additional water will be proposed for Wallpolla Horseshoe, to support fish remaining in the wetland after the exit strategy is trialled.

Recent conditions

Rainfall and daily maximum temperatures at Lindsay, Mulcra and Wallpolla islands were close to the long-term average throughout 2020-21. Carryover of water in the Murray system was important, to meet demands for water for the environment early in the water year. Victorian Murray allocations reached 55 percent of high-reliability water shares by mid-October 2020 and 100 percent of high-reliability allocation by mid-February 2021. Allocations combined with carryover provided a sufficient supply of water for the environment to meet the planned watering actions identified for the Lindsay, Mulcra and Wallpolla islands system.

Flows in the Murray River throughout late autumn, winter and early spring 2020 allowed the Murray-Darling Basin Authority to achieve Lake Victoria’s storage level targets. As a result, less water was diverted from the Murray River weir pool 9 to Lake Victoria in middle to late spring 2020 than would be the case in a drier year, but diversions occasionally occurred to meet Lake Victoria’s requirements. Weir pools 7 and 8 were both held near to or above full supply levels from early winter 2020 to early summer, which meant additional water associated with natural inflows from the upper Murray catchment and a coordinated spring pulse of water for the environment delivered from Lake Hume was pushed into the upper Lindsay River (via Lindsay River north) and Potterwalkagee Creek for short periods. These flows were affected by occasional diversions to Lake Victoria, and they were not large enough to provide sustained flows in Lindsay River and Potterwalkagee Creek, let alone fill wetlands or inundate floodplain habitats on the islands. A spring high flow was also provided to Mullaroo Creek through the Mullaroo Creek regulator and fishway.

Flow in the Murray River returned to normal operating levels in summer and autumn 2021, and weir pools 7 and 8 were lowered to increase the amount of flowing-water habitat for native fish in the Murray River and to expose banks to support the establishment of vegetation. These actions ceased the flow to the Lindsay River and Potterwalkagee Creek, and flow in Mullaroo Creek was returned to low flow (600 ML per day) for the rest of 2020-21.

In spring 2020, water for the environment was delivered (via temporary pumps) to four wetlands on Lindsay Island for the first time since natural floods in 2016 and four wetlands/creeklines on Wallpolla Island watered the previous spring. In autumn/winter 2021, Lake Wallawalla was partially filled with water pumped from the Lindsay River. Management of the system during 2020-21 was principally in line with a dry climate scenario, and the planned watering actions identified for those conditions in the Seasonal Watering Plan 2020-21 were mostly achieved. The only required watering actions that were not fully achieved were the planned fills at Crankhandle and Scotties Billabong. Seepage rates at these sites were higher than expected, which meant the delivered water did not inundate as much of the fringing river red gum, black box and lignum vegetation communities as planned. Topping up these wetlands in spring 2021 will be a priority.

Recent condition monitoring shows that the health of river red gum, black box and lignum is generally in decline across the Lindsay, Mulcra and Wallpolla islands. In many areas, understory vegetation coverage is gradually transitioning to non-flood- dependant species. The poorest-quality vegetation is at Lindsay and Wallpolla islands, but without significant watering, the vegetation community on Mulcra Island is expected to deteriorate significantly. Environmental watering targeting selected wetlands on Lindsay and Wallpolla islands will be needed in 2021-22 to address the decline at specific sites, while larger-scale floodplain watering is recommended at Mulcra Island.

Scope of environmental watering

Table 1 Potential environmental watering actions, expected watering effects and associated environmental objectives for the Lindsay, Mulcra and Wallpolla islands

Potential environmental
watering action

Expected Watering Effects

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 soil moisture to maintain the condition of streamside vegetation
Fish iconPlant icon

Spring high-low flow (1,200 ML/day for three months during September to November)

  • Increase the extent and velocity of fast-flowing water habitat to cue movement and spawning and improve recruitment opportunities for native fish
  • Provide improved fish passage between Mullaroo Creek and the Murray River via the Mullaroo Creek regulator fishway

Fish icon

Lindsay Island – Lindsay River
Winter/spring/summer low flow via the southern regulator (50 ML/ day for six months during July to December)
  • Provide temporary flowing water to connect 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 bank soil moisture to support the growth of streamside vegetation

Fish iconJigsaw iconPlant icon

Winter/spring/summer low flow via the northern regulator (95 ML/ day for six months during July to December)
Lindsay Island wetlands
Crankhandle (top-up in spring)
  • Inundate the margins of the wetland to provide foraging and breeding opportunities for frogs, reptiles and waterbirds
  • Provide conditions for lake bed herbaceous plants to grow in the drying phase after watering
  • Increase soil moisture to maintain and improve the condition of streamside vegetation, particularly lignum
  • Stimulate the growth of aquatic vegetation

Plant iconFrog iconHeron iconTurtle icon

Lake Wallawalla (partial to complete fill in winter/ spring)
  • Provide shallow-water habitat, open-water habitat and shoreline habitat to create foraging opportunities for waterbirds
  • Stimulate the release of carbon and nutrients to increase the productivity of the floodplain food web, to increase the growth rate of yabbies
  • Provide conditions for lake bed herbaceous plants to grow in the drying phase after watering
  • Increase soil moisture to maintain and improve the condition of streamside vegetation, particularly river red gum
  • Provide roosting habitat over open water to support breeding colonial nesting birds

Frog iconPlant iconJigsaw iconInsect icon

Lindsay-Mullaroo connector (fill in spring)
  • Provide shallow-water habitat to provide refuge (if conditions are dry in the next 2-3 years) and feeding habitat for frogs and waterbirds
  • Provide conditions for lake bed herbaceous plants and semi-aquatic plants to grow in the littoral zone in the drying phase after watering
  • Maintain habitat for aquatic vegetation and provide soil moisture to maintain and improve the condition of river red gums and black box

Frog iconPlant iconHeron icon

Scotties Billabong (fill in spring)
Stockyards (fill in autumn)
Websters Lagoon (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 during the drying phase after watering
  • Provide variable water levels in the littoral zone to provide feeding habitat for shorebirds
  • Provide open-water habitat as a refuge (if conditions are dry in the next 2-3 years) and feeding and breeding habitat for waterbirds

Fish iconJigsaw iconPlant iconHeron icon

Wetland 33 (top-up in spring)
  • Provide shallow-water habitat to provide feeding habitat for frogs, reptiles and waterbirds
  • Maintain water of sufficient depth to encourage nesting waterbirds to complete the fledgling process

Frog iconTurtle iconHeron icon

Mulcra Island – Potterwalkagee Creek
Spring low flow via the Stony Crossing regulator (115-280 ML/day for three months during September to November)
  • Provide temporary flowing water to connect 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

Spring low flow via the upper Potterwalkagee Creek regulator (15- 145 ML/day for three months during September to November)

Winter/spring overbank flow via the Stony Crossing regulator (470 ML/day for 4  months during August to November)

  • Provide a connection between Potterwalkagee Creek and the floodplain to allow the exchange of nutrients and carbon between the floodplain and the Murray River system
  • Provide off-channel habitat for small-bodied fish to feed and breed

Fish iconJigsaw icon

Winter/spring overbank flow via the upper Potterwalkagee Creek regulator (420 ML/day for 4 months during August to November)
Mulcra Island – wetlands
Mulcra Horseshoe (fill in spring)
  • Provide shallow and open-water habitat to create foraging and breeding opportunities for waterbirds
  • Provide shallow-water habitat to provide refuge (if conditions are dry in the next 2-3 years) and feeding habitat for frogs and turtles
  • Stimulate the growth of emergent, aquatic and streamside vegetation
  • Provide moisture for lake bed herbaceous plants to grow during the drying phase of the wetland
  • Stimulate the release of carbon and nutrients to increase the productivity of the floodplain food web

Frog iconJigsaw iconTurtle iconPlant iconHeron icon

Mulcra Island floodplain (floodplain inundation in spring)
  • Provide shallow- and open-water habitat to create foraging and breeding opportunities for waterbirds
  • Provide shallow-water habitat to provide feeding habitat for frogs and turtles
  • Increase soil moisture to maintain and improve the condition of streamside and floodplain vegetation, specifically river red gum, black box and lignum
  • Stimulate the release of carbon and nutrients from the sediment to increase the productivity of the floodplain food web
  • Provide a connection to the Murray River to allow the exchange of carbon and nutrients between the floodplain and the river

Frog iconTurtle iconPlant iconHeron iconJigsaw icon

Wallpolla Island

Finnigans Creek (low flow in spring)

Fishing icon

  • Provide connections between Wallpolla Horseshoe and Finnigans Creek to allow the dispersal of stocked native fish from Wallpolla East to Finnigans Creek and eventually to the Murray River via Wallpolla Creek
  • Provide variable water levels in the littoral zone to promote the growth of aquatic vegetation and increase soil moisture for streamside vegetation, particularly river red gums
  • Provide shallow-water habitat to provide refuge (if conditions are dry in the next 2-3 years) and feeding habitat for wetland-dependant species including frogs and waterbirds

Fish iconFrog iconPlant iconHeron icon

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

Fishing icon

  • Provide connections between Wallpolla Horseshoe and Finnigans Creek to allow the dispersal of stocked native fish from Wallpolla East to Finnigans Creek and eventually to the Murray River via Wallpolla Creek
  • Wet/drown river red gum saplings in the inlet channel to Wallpolla Horseshoe to limit their coverage
  • Increase soil moisture to maintain and improve the condition of streamside and vegetation, specifically river red gum
  • Provide suitable breeding conditions for waterbirds
  • Provide permanent habitat for fish in the wetland
  • Provide shallow- and open-water habitat to create foraging and breeding opportunities for 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

Fish iconFrog iconTurtle iconPlant iconHeron icon

Engagement

Table 3 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 3 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: 22/07/21