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Lindsay, Mulcra and Wallpolla islands cover over 26,100 hectares of River Murray floodplain, forming part of the Chowilla floodplain and Lindsay–Wallpolla Island Living Murray icon site. The floodplain is characterised by a network of permanent waterways, small creeks and wetlands. The larger, permanent waterways–Lindsay River, Potterwalkagee Creek and Wallpolla Creek–form the southern boundaries of the site and create large floodplain islands with the River Murray to the north.

Naturally, these waterways and wetlands would flow and fill in response to high water levels in the River Murray. However, the regulation of the River Murray has reduced its influence on the Lindsay, Mulcra and Wallpolla system.

Although large floods can still occur, flows through the system are mostly regulated by the River Murray locks 6 to 9. Regulators and containment structures have been built throughout the Lindsay, Mulcra and Wallpolla floodplain and are used to help protect the environmental values at the site.

System map

Murray System

Environmental watering objectives in Lindsay, Wallpolla and Mulcra

Fish icon
Increase abundance, diversity and movement of native fish
bird icon
Provide feeding and breeding habitat for a range of waterbird species including threatened and migratory species and colonial species (such as the egret)
Fish icon
Provide flows for large-bodied fish (including Murray cod and perch) to swim, feed and breed
Plant icon
Increase the diversity, extent and abundance of wetland plant life

Environmental values

The Mullaroo and Potterwalkagee creeks are renowned for holding very large Murray cod. These creeks provide superior fish habitat compared to the nearby weir pools in the River Murray, and large breeding fish in the creeks are an important source of juveniles to the Murray system. The waterways also support several other threatened fish species, such as the freshwater catfish, silver perch, Murray–Darling rainbowfish and unspeckled hardyhead.

The vast scale of the Lindsay, Mulcra and Wallpolla islands site is noteworthy because it provides very large expanses of habitat to support wetland-dependent and terrestrial species. Several rare and threatened plant types occur on the floodplain and in the wetlands as well as more common types of woodlands (such as black box and river red gum).

When flooded, waterways and wetlands within this system provide excellent habitat for waterbirds, 40 species of which are threatened in Victoria including the great egret and red-necked stint. Terrestrial animals also benefit from the improved productivity and food resources when flooding occurs.

Social and economic values

The islands offer recreation opportunities in a remote location with camping, boating and fishing popular for residents of nearby communities and long-distance travellers.

The floodplain and wetland systems have many sites with valuable Aboriginal heritage including shell middens, burial sites and scar trees. Lindsay Island is noteworthy due to the presence of many archaeological sites and the floodplain and wetland systems continue to be places of importance for Traditional Owners and their Nations in the region.

Conditions mid-2016

Floods in 2010 and 2011 provided the first large-scale floodplain watering event in 15 years, but there have not been flows high enough for widespread floodplain watering since. Local conditions have been hot and dry in recent years, causing high evaporation and wetland drying.

The weir pools at River Murray locks 6 to 9 have been managed to add greater variability in water levels to improve environmental outcomes in the waterways, floodplains and wetlands in the system. The raising and lowering of these weir pools has been managed to facilitate delivery of preferred baseflows and freshes to Potterwalkagee and Mullaroo creeks in 2015–16. The events also facilitated the commissioning of newly completed infrastructure on Mullaroo Creek.High flows and flushes in the Lindsay River were provided to stimulate fish movement and to facilitate pumping of water into surrounding floodplain wetlands. During these high flows, 8,000 ML was pumped into Lake Wallawalla and 600 ML into Wallpolla East Wetland to improve vegetation condition and provide habitat for waterbirds to feed

Scope of environmental watering

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

Potential environmental watering

Environmental objectives

Lindsay Island

Year-round baseflows in Mullaroo Creek (greater than 400 ML/day)

  • Maintain flowing water habitat for native fish species such as the Murray cod, silver perch and golden perch

Year-round baseflows in the northern Lindsay River (greater than 40 ML/day year-round)

Spring freshes in Mullaroo Creek (up to 1,000 ML/day in September to November)

  • Stimulate golden perch spawning and movement, and seasonal Murray cod movement
  • Maintain flows to assist in recruitment and survival of fish

Spring and summer high flows in the northern and southern Lindsay River (up to 450 ML/day in September–February)

Year-round high flows in Mullaroo Creek (up to 1,000 ML/day year-round)

Mulcra Island

Year-round baseflows in lower Potterwalkagee Creek (up to 100 ML/day year-round)

  • Maintain flowing water habitat for large-bodied native fish, particularly golden perch

Spring freshes and high flows in lower and upper Potterwalkagee Creek (up to 500 ML/day year-round)

  • Stimulate large-bodied native fish movement and spawning

Floodplain inundation of lower Potterwalkagee Creek

  • Improve condition of lignum shrublands
  • Provide floodplain habitat for small-bodied fish to reproduce

Wallpolla Island

Spring inundation of Wallpolla East, Sandy Creek and floodplain, Finnegans Creek and Wallpolla Horseshoe (filling flows in September–November)

  • Provide temporary habitat for plants and animals and increase wetland productivity

Wetland drying

Lake Wallawalla

  • Lake Wallawalla will not be actively watered in 2016–17
  • Drying will assist in maintaining a diversity of habitats to support a wide range of wetland-dependent birds and animals and promote the growth and establishment of vegetation in and surrounding the wetland

Scenario planning

Watering at Lindsay, Mulcra and Wallpolla islands in 2016–17 will focus on providing variable flows in the major waterways and anabranches of the systems (including Lindsay River) and Mullaroo and Potterwalkagee creeks. These flow events will again be coordinated with weir pool operations.

Baseflows (low flows) are generally provided in these waterways by consumptive (water for households, industry and farming) water. Under drought and dry conditions spring freshes (small pulses of water) will also be provided to maintain habitat and provide migration opportunities for native fish. Wetland watering actions are not planned under drought conditions but will become a priority for delivery as conditions improve.

Table 2 Potential environmental watering for Lindsay, Wallpolla and Mulcra islands under a range of planning scenarios

Planning scenario

Drought

Dry

Average

Wet

Expected catchment conditions

  • No unregulated flows in the River Murray year-round
  • No natural inflows expected into wetlands or floodplain
  • Short periods of high flows in the River Murray in late winter and early spring will provide minor filling of wetlands and the floodplain
  • Lengthy periods of high flows and floods with major spills from storages resulting in widespread inundation of the floodplain and inundating most wetlands

Potential environmental watering – Lindsay and Mulcra Islands

  • Year-round baseflows in Mullaroo Creek and Potterwalkagee Creek
  • Spring freshes in Mullaroo Creek
  • Year-round baseflows in Mullaroo Creek and Potterwalkagee Creek
  • Spring freshes in Mullaroo Creek
  • Spring freshes and high flows in Mullaroo Creek and Potterwalkagee Creek
  • Spring and summer high flows in northern and southern Lindsay River
  • Year-round high flows in Mullaroo Creek
  • Spring and summer high flows in northern and southern Lindsay River
  • Floodplain inundation above the lower Potterwalkagee regulator

Possible volume of environmental water required to meet objectives

  • 2,000 ML1

Potential environmental watering – Wallpolla Island

  • N/A
  • Spring inundation of Wallpolla East, Sandy Creek and floodplain, Finnegans Creek and Wallpolla Horseshoe
  • Spring inundation of Wallpolla East, Sandy Creek and floodplain, Finnegans Creek and Wallpolla Horseshoe
  • Spring inundation of Wallpolla East, Sandy Creek and floodplain, Finnegans Creek and Wallpolla Horseshoe
  • Increased flows in all systems and large-scale floodplain inundation

Possible volume of environmental water required to meet objectives

  • N/A
  • 2,100 ML
  • 2,700 ML
  • 4,000 ML

1 Volume includes the estimated volume of environmental water required to underwrite the losses associated with the delivery of consumptive water en route (for flows within the Mullaroo Creek, Lindsay River and Potterwalkagee Creek).

Risk management

In preparing its seasonal watering proposal, Mallee Catchment Management Authority considered and assessed risks and identified mitigating strategies relating to the implementation of environmental watering. Risks and mitigating actions are continually reassessed by program partners throughout the water year.

Engagement

Waterway managers meet communities on environmental watering regionally, although other program partners also play a role.

In each region of Victoria, community engagement on environmental watering happens when environmental watering objectives and priorities are scoped (long term and annually), when delivering environmental water, and when reporting on environmental watering results.

In the Corangamite region communities are involved in decisions about the Moorabool river and Lower Barwon wetlands. This happens through formal advisory groups including a Moorabool stakeholder advisory and the Lower Barwon community advisory committees.

Who is engaged and how

Recreational users

The Mallee Catchment Management Authority meets with recreational users (such as fishers, bushwalkers, various 'Friends of...' groups) on an ad-hoc basis, where recreational users have an opportunity to communicate their priorities and perspectives. A gap in engagement is anglers as there is not an organised representative group.

Parks Victoria is the land manager for many of the sites that receive environmental water. Parks Victoria notifies recreational users about planned environmental water deliveries and communicates the potential impacts of environmental watering (through their website and on-site public signage).

Environment groups

The Catchment Management Authority engages environment groups (such as the Field Naturalists, Landcare and Birdlife Australia) through direct meetings 2-3 times a year. These groups provide advice, communicate their priorities and are keen to understand environmental watering objectives and outcomes. Some groups also provide information on the outcomes of environmental watering (e.g. through bird surveys.)

Landholders/farmers

The Catchment Management Authority engages the Victorian Farmers Federation, and industry groups such as table grape growers, dried fruit growers, citrus growers and landholders with river frontage or private wetlands.

These groups are engaged on environmental water planning (long term and annual scoping) and environmental water delivery. These groups are also engaged on related projects such as the Sustainable Diversion Limit adjustment proposals.

Traditional Owners

There are representatives from multiple Traditional Owner Nations from the Mallee region on the Murray Lower Darling Rivers Indigenous Nations. The Victorian Environmental Water Holder, the Commonwealth Environmental Water Office and the Murray-Darling Basin Association engage the Murray Lower Darling Rivers Indigenous Nations on strategic (often longer term) issues related to environmental watering.

Through the Catchment Management Authority Indigenous facilitator, individual Aboriginal stakeholders and groups are directly engaged throughout the year via the Catchment Management Authority Aboriginal Reference Group.

Councils

The Catchment Management Authority engages with the Mildura and Swan Hill Rural City Councils quarterly. Councils provide advice on potential community impacts of environmental watering and communicate environmental watering information back to the broader community.

General public

The Catchment Management Authority engages and communicates with the general public about environmental watering via SMS, their website, publications and media releases.