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

Before the construction of Lake Glenmaggie, the Macalister River would regularly receive high and medium flows in winter and spring. Although Lake Glenmaggie regularly spills, high flows are less frequent than natural because much of the water is captured by the storage. A notable impact of irrigation and water-harvesting is reversed seasonality of flows between Lake Glenmaggie and Maffra Weir. Summer flows through this reach are  much higher than natural due to the delivery of irrigation water. Winter flows in this reach are lower than natural because a high proportion of the  inflows are captured and there are no irrigation demands over winter. Below Maffra Weir, most flows are diverted for irrigation in summer/autumn.  The changed hydrology restricts fish migration, limits the growth and recruitment of in-stream and streamside plants and reduces the quality of in-  stream habitat.

Water for the environment is stored in Lake Glenmaggie and released to the Macalister River. The river is divided into two reaches for the purposes  of managing environmental flows: Lake Glenmaggie to Maffra Weir (reach 1) and Maffra Weir to the Thomson River (reach 2).

Maffra Weir is a major barrier to fish movement along the river, so environmental watering for migratory fish objectives mainly focus on reach 2. All  other objectives apply to both reaches 1 and 2.

Traditional Owners
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 distribution, recruitment and abundance of all native fish, and increase opportunities for the spawning and recruitment of native migratory fish (such as the Australian grayling)
Improve and maintain the form of the riverbank and bed to provide physical habitat for aquatic animals and plants
Platypus icon
Increase the abundance of platypus and rakali (water rats)
Plant icon
Improve native emergent (non-woody) and fringing (woody) vegetation in the riparian zone. Reinstate or instate submerged aquatic vegetation.
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Increase the abundance and number of functional groups of waterbugs

Environmental values

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

The streamside vegetation corridor along the regulated reaches of the Macalister River is fragmented. Immediately below Lake Glenmaggie, the vegetation is in good condition and includes remnant river red gums and good-quality stands of shrubs, particularly in areas where revegetation has occurred in combination with stock exclusion. 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 plant growth. The cover of non-woody plants (such as reeds, sedges and rushes) along the fringes of the river is patchy.

Traditional Owner cultural values and uses

The Gunaikurnai have had a continued connection to Gunaikurnai Country for thousands of years, including with the waterways in the Latrobe River system (which the Macalister River feeds into). For the Gunaikurnai as traditional custodians there are immense challenges to heal, protect and manage Country which has been drastically altered since colonisation. Gunaikurnai see all of Country as connected with no separation between landscapes, waterways, coasts and oceans and natural and cultural resources – the cultural landscape is interdependent. Gunaikurnai Land and Waters Aboriginal Corporation (GLaWAC) are working with the West Gippsland CMA to determine how to express Gunaikurnai objectives for water in a way that contributes to seasonal watering proposals from the perspective of traditional custodians, with traditional knowledge.

GLaWAC expressed that more water needs to go down the Macalister River between Lake Glenmaggie and Lake Wellington, to improve water quality including the threat of salinity, and support plants and animals with cultural values and uses.

Timing of watering events has also been raised by GLaWAC. This includes providing increased water depth to promote downstream fish migration and spawning, deeper water pools to prevent water quality degradation, and more variation to water levels to better mimic natural conditions.

Traditionally the landscape – which includes the Macalister River, anabranches, and associated floodplains – has been a rich source of food, medicine and resources for the Gunaikurnai people. In the area, there are many sites of cultural significance near the river and around Lake Glenmaggie. The Gunaikurnai people have moved through the landscape along the waterways for thousands of years, sourcing food and plants along the way.

From the perspective of the Gunaikurnai people, the land and waterways flowing to the Gippsland Lakes are interconnected and cannot be considered separately where decisions made can impact downstream. The lower Latrobe wetlands and the rivers that feed them, including the Macalister, have important cultural significance to the Gunaikurnai people.

Watering requirements to support cultural values and uses include:

  • timing of environmental watering planned in partnership with GLaWAC to support a seasonal flow regime and wet and dry periods that embody Healthy Country
  • maintaining freshwater supply to Latrobe estuary, Dowd Morass, Sale Common and Heart Morass and associated freshwater habitats. The lower Latrobe wetlands are an important resource for the Gunaikurnai
  • providing connectivity between reaches and onto floodplains to support dependent plants and animals with cultural values and uses of significance to the Gunaikurnai
  • maintaining water quality to support health of native plants and animals with cultural values and uses of significance to the Gunaikurnai.

Social, recreational and economic values and uses

In planning the potential watering actions in Table 1, West Gippsland CMA considered how environmental flows could support values and uses including:

  • water-based recreation (such as kayaking, fishing and swimming)
  • riverside recreation and amenity (such as camping, birdwatching, duck hunting and amenity for access tracks)
  • socio-economic benefits (such as preventing erosion and potential land loss for local landholders).

Recent conditions

The Macalister River catchment has observed ongoing very dry climatic conditions over the last three years. Rainfall has been below average and temperatures warmer than average. In June 2019, the storage level at Lake Glenmaggie was exceptionally low: just 6.1 percent of the full reservoir capacity. Opening allocations of 45 percent towards high-reliability water shares were declared by the storage manager, and this increased to 80 percent by mid- August after inflows improved the water storage level. Despite the dry start, continued inflows over spring led to full allocations for high-reliability water shares by the end of September 2019, boosting water available for environmental watering. Low-reliability water shares also increased throughout the year in response to inflows, reaching full allocation in April 2020.

As of 1 June 2020, Lake Glenmaggie had not spilled in 2019–20. This is an unusual occurrence: historically, Lake Glenmaggie spills most years, as it is a relatively small reservoir in a productive water catchment. 2019–20 was the second consecutive year without a spill, demonstrating how dry the system has been in recent times. Without a spill, the natural high and bankfull flows that usually occur in the Macalister River in winter/spring were absent, but above Maffra Weir the river flowed steadily for most of the year, because water for irrigation and urban supply is delivered between Lake Glenmaggie and the offtake at Maffra Weir. Below Maffra Weir, some moderate natural flows occurred in spring and late summer after heavy rainfall.

Environmental flows were delivered year-round to provide several objectives in the Macalister system. Flows were delivered over winter to maintain habitat for aquatic animals and to support the establishment of in-stream vegetation. This included a winter fresh in August 2019, and again in June 2020, which aimed to cue the downstream migration of tupong and Australian bass towards the Latrobe estuary for breeding and spawning. A spring fresh was delivered in early November 2019, to encourage juvenile fish to migrate into the Macalister River from their estuary nurseries as well as to wet bankside vegetation and enable native seed dispersal.

In autumn 2020, a fresh to cue the downstream migration of Australian grayling towards the Latrobe River estuary for spawning was delivered. This event coincided with an equivalent fresh in the Thomson River system to optimise fish responses across both systems.

All tier 1a watering actions planned for 2019–20 under both a dry and average scenario were met. As Lake Glenmaggie did not spill, there were no tier 1b actions, either with releases of water for the environment or natural and operational flows in the system.

Scope of environmental watering

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

Potential environmental watering action

Functional watering objectives

Environmental objective

Macalister River reaches 1 and 2

Autumn/winter low flow (90 ML/day during March to August)

  • Provide minimum depth over riffles for fish species that are migrating (i.e. Australian grayling) or about to migrate (i.e. tupong and Australian bass) downstream towards estuary habitat for spawning or breeding
  • Provide permanent wetted habitat for waterbugs through minimum water depth in pools
  • Provide connectivity throughout the river for the local movement of platypus and rakali (water rats), as well as protection from predation, access to food sources and to maintain refuge habitats
  • Provide flows with low water velocity and appropriate depth to improve water clarity and enable establishment of submerged vegetation
  • Provide sustained wetting of low-level benches (increasing water depth) to limit terrestrial vegetation encroachment
Fish iconPlatypus iconPlant iconInsect icon

Spring/summer low flow (90 ML/day during September to January)

  • Maintain the water depth in pools and hydraulic habitat for native fish
  • Maintain permanent wetted habitat in pools and riffles for waterbugs
  • Maintain shallow, slow-flowing habitat to enable the establishment of instream vegetation
  • Maintain a minimum depth in pools to allow for turnover of water and to slow degradation of water quality to support aquatic life
  • Expose and dry lower channel features for re-oxygenation

Fish iconPlant iconInsect icon

Spring/summer fresh (one to two freshes of 1,500 ML/day for three days during September to December)1
  • Cue the upstream migration of adult fish (e.g. short-headed lamprey), and the recruitment of juveniles (e.g. Australian grayling, tupong, common galaxias, Australian bass, short and long-finned eels) from marine/ estuarine environments
  • Wet a greater area of the stream channel (increasing water depth) to limit terrestrial vegetation encroachment
  • Wet mid- and higher-level benches to water woody vegetation
  • Flush pools to improve the water quality and increase wetted habitat for waterbugs
  • Provide flows with sufficient shear stress to flush fine sediment from small gaps to improve geomorphic habitat

Fish iconMountain iconsPlant iconInsect icon

Macalister River reach 2

Autumn fresh (one fresh of 350 ML/day for three to seven days during April to May)

  • Cue the downstream migration for Australian grayling towards the estuary for spawning
  • Fully flush the upper Thomson estuary (when delivered for greater than three days and combined with freshes in the Thomson River) to flush sediments from substrates, provide water quality conditions that support waterbugs and to provide freshwater to the lower Latrobe River and wetlands

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Winter fresh (one to two freshes of 700 ML/day for four to five days during June to August)

  • Cue the downstream migration towards the estuary of Australian bass for spawning and of tupong for breeding

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Spring fresh (one fresh of 700 ML/day for five days during September to November)

  • Cue the upstream migration of adult fish (e.g. short-headed lamprey), and recruitment of juveniles (e.g. Australian grayling, tupong, common galaxias, Australian bass, short and long-finned eels) from marine/ estuarine environments
  • Wet a greater area of the stream channel (increasing water depth) to limit terrestrial vegetation encroachment
  • Wet low and mid-level benches to facilitate the dispersal of emergent andrewandjaney@gmail.com fringing vegetation throughout the reach

Fish iconPlant icon

Summer/autumn fresh (one to three freshes of 140 ML/ day for three to 10 days during December to May)

  • Increase the depth to allow fish to move throughout the reach
  • Flush pools to maintain water quality for aquatic animals
  • Flush substrates and improve the quality of existing waterbug habitat and food supply
  • Wet low benches to facilitate the longitudinal dispersal of emergent vegetation
  • Provide flows with sufficient shear stress to flush fine sediment from small gaps to improve geomorphic habitat

Fish iconMountain iconsPlant iconInsect icon

Trigger-based summer/ autumn low flow (35–60 ML/day during December to May)2

  • Maintain permanent wetted habitat in pools and riffles for aquatic animals
  • Maintain shallow, slow-flowing habitat to maintain in-stream vegetation
  • Maintain a minimum depth in pools to allow for turnover of water and to slow degradation of water quality to support aquatic life

Fish iconPlant iconInsect icon

1 This fresh is only planned to be delivered following a spill in Lake Glenmaggie (if the magnitude is lower than minor flood level), to extend or slow the rate of ramp-down. If a spill occurs, delivering this fresh will meet the functional flow objectives of the lower magnitude spring/summer fresh.

2 A low flow of 35–60 ML per day may be triggered if passing flows from Maffra Weir reduce or cease.

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
  • Maffra and districts
  • Landcare network
  • Native Fish Australia
  • Southern Rural Water
  • Gippsland Water
  • Macalister Irrigation District irrigators/ diverters
  • Other landholders
  • VRFish
  • Arthur Rylah Institute (Department of Environment, Land, Water and Planning)
  • Gunaikurnai Land and Waters AboriginalCorporation

Page last updated: 24/07/20