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The Macalister River flows from Mt Howitt in the Alpine National Park and joins the Thomson River south of Maffra. The river winds its way in a south-easterly direction through mostly forested, confined valleys and narrow floodplains upstream of Lake Glenmaggie. The downstream reaches flow through wide alluvial floodplains that have been cleared for agriculture. The Wellington River and Glenmaggie Creek are the main tributaries of the Macalister River.

Lake Glenmaggie is the major water-harvesting storage regulating the Macalister River, and the Maffra Weir is a small diversion weir located further downstream in Maffra.

The Macalister River and its tributaries continue to be an important place for Traditional Owners and their Nations. The Registered Aboriginal Party (RAP) in the region is the Gunaikurnai Land and Waters Aboriginal Corporation. The West Gippsland CMA engaged with representatives from the RAP during the preparation of the Macalister River seasonal watering proposal.

Storage manager
Environmental water holder

System map

Macalister System
Grey river reaches have been included for context. The numbered reaches indicate where relevant environmental flow studies have been undertaken. Coloured reaches can receive environmental water.

Environmental watering objectives in the Macalister River

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Increase the range and population size of native fish species including Australian grayling and other native fish Improve spawning and recruitment opportunities for native migratory fish
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Increase the abundance of waterbugs Maintain water quality throughout the year for waterbug habitat
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Restore aquatic vegetation Improve native emergent and fringing vegetation communities
Improve and maintain the form of the riverbank and bed

Environmental values

Seven migratory native fish species move between the Macalister River, the Latrobe River estuary and the sea to complete their life cycle. These species include the Australian grayling, short- and long-finned eel, tupong, Australian bass, short-headed lamprey and common galaxias. Yelloweye mullet, which are an estuarine species, has been recorded in the river. Platypus and water rats are widely distributed through the Macalister River and its tributaries.

The riparian vegetation corridor along the regulated reaches of the Macalister River is fragmented. Immediately downstream of Lake Glenmaggie, the vegetation is in good condition and includes remnant river red gums and good-quality stands of shrubs, particularly in areas where there has been revegetation and from which stock have also been excluded. Further downstream, the vegetation is degraded. In recent years, the cover of in-stream vegetation has declined, which may be due to a combination of increased water turbidity, erosion and a lack of an appropriate water regime to encourage plants to grow. The cover of non-woody plants (such as reeds, sedges and rushes) along the fringes of the river is patchy.

Social and economic values

Lake Glenmaggie is the primary source of water for the Macalister Irrigation District, a major economic driver in the area and highly valued by the local community. As a result, there is strong interest in the health of the Macalister River, particularly around water quality, erosion and vegetation condition issues. The river is also a popular location for recreational fishing and birdwatching.

Conditions 2018

Climatic conditions in the Macalister River catchment have varied widely over the last two years. Winter and spring 2016 had above-average rainfall and minor flooding, but the rest of the 2016–17 water year was significantly drier than average. Dry conditions persisted through much of 2017–18, and the only moderate-to-large. Unregulated flows occurred in December 2017 and January 2018.

In response to the dry conditions, irrigation demands have been high, and the reach of the Macalister River between Lake Glenmaggie and Maffra Weir has therefore carried consistently high irrigation flows since the start of the irrigation season in August 2017. Water for the environment was used to provide freshes in autumn, winter and spring and increased baseflows over the autumn/winter period, when there was less irrigation demand.

Dry conditions in the second half of 2016–17 restricted environmental allocations at the start of the 2017–18
water year, and water for the environment carried over from 2016–17 was needed to deliver target low flows and freshes through winter and spring 2017. A winter fresh was delivered in August 2017 to trigger migration and spawning of tupong and Australian bass. A spring fresh was delivered in early November 2017, to encourage juvenile fish to migrate into the Macalister River from the sea and to wet bankside vegetation and enable native seed dispersal. Lake Glenmaggie spilled in early December 2017, but it was a comparatively small spill and later in the year than is usually the case. The storage manager (Southern Rural Water) managed flows during and after the spill to prevent a sudden drop in water levels that might have stranded fish or caused banks to slump. An autumn fresh was delivered in April 2018 to trigger Australian grayling to migrate and spawn.

Scope of environmental watering

Table 1 Potential environmental watering actions and objectives for the Macalister system

Potential environmental watering

Environmental objectives

Macalister River reaches 1 and 2

Autumn/winter low flow (90 ML/day in May–August

  • Provide longitudinal connectivity 
  • Provide habitat for waterbugs 
  • Maintain water quality in pools 
  • Maintain areas of slow-moving water for submerged aquatic vegetation

Spring low flow (90 ML/day in September–December)

  • Provide longitudinal connectivity
Spring fresh (1,500 ML/day for 3 days in September–October)
  • Scour sediment exposing fresh habitat areas 
  • Provide food and habitat for waterbugs

Macalister River reach 2

Autumn fresh (350 ML/day for 4–5 days in April–May)

  • Trigger downstream migration and spawning of Australian grayling

Winter fresh (700 ML/day for 4–5 days in June–August)

  • Trigger downstream migration and spawning of tupong and Australian bass

Spring/summer fresh (700 ML/day for up to 5 days in September–December)

  • Trigger upstream migration and recruitment for juvenile fish
  • Trigger upstream migration for adult lampreys and eels

Summer/autumn fresh (140 ML/day for 3 days in December–May)

  • Provide sufficient depth to allow fish to move throughout the reach
  • Flush pools to maintain water quality

Risk management

In preparing its seasonal watering proposal, West Gippsland CMA considered and assessed the risks of environmental watering and identified mitigation strategies. Program partners continually reassess risks and mitigation actions throughout the water year

Engagement

Table 2 shows the partners and stakeholder organisations with which West Gippsland CMA engaged when preparing the Macalister system 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 West Gippsland Regional Catchment Strategy and West Gippsland Waterway Strategy.

Table 2 Partners and stakeholders engaged in developing the Macalister system seasonal watering proposal 

Partner and stakeholder engagement
  • Environment Victoria 
  • Gippsland Water 
  • Gurnaikurnai Land and Waters Aboriginal Corporation 
  • Macalister Irrigation District irrigators and diverters 
  • Maffra & Districts Landcare Network 
  • Native Fish Australia 
  • Southern Rural Water 
  • Victorian Environmental Water Holder 
  • VRFish 
  • Wellington Shire Council