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

Before the construction of Lake Glenmaggie, Wirn wirndook Yeerung (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 Wirn wirndook Yeerung (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 Carran Carran (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

Fish icon
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.
Insect icon
Increase the abundance and number of functional groups of waterbugs

Environmental values

Seven migratory native fish species move between Wirn wirndook Yeerung (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 Wirn wirndook Yeerung (Macalister River) and its tributaries.

The streamside vegetation corridor along the regulated reaches of Wirn wirndook Yeerung (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 system (into whichWirn wirndook Yeerung [Macalister River] feeds). 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.

The 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 Wirn wirndook Yeerung (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.

The 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 Wirn wirndook Yeerung (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 Wirn wirndook Yeerung (Macalister River), 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 the Latrobe River 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 the 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 2, West Gippsland CMA considered how environmental flows could support values and uses including:

  • water-based recreation (such as canoeing, kayaking and swimming)
  • riverside recreation and amenity (such as fishing and hunting)
  • socio-economic benefits (such as preventing erosion and potential loss of private land).

Recent conditions

Rainfall in the Macalister system in 2020-21 was slightly higher than the long-term average. High inflows in autumn 2020 filled Lake Glenmaggie, and additional rain events caused it to spill multiple times through winter and spring. Opening allocations of high-reliability water shares were 100 percent, and low-reliability water share allocations reached 100 percent in April 2021.

Releases of water for the environment in the Macalister system were made in line with the average and wet climate scenarios throughout 2020-21. All of the planned watering actions for 2020-21 were met through a combination of natural flows, operational and consumptive releases and environmental flows. Flows at Riverslea gauge (located in reach 2) exceeded 4,000 ML per day several times between July and October 2020. Water for the environment was used to maintain connectivity in the river as needed during the storage filling season and to deliver freshes in autumn and early winter to support fish migration.

Fish surveys conducted in Wirn wirndook Yeerung (Macalister River) in March 2021 caught many young-of- year tupong, which suggests high flows in spring 2020 supported successful recruitment for that species. On a landscape scale, west Gippsland catchments may provide refuge habitat for coastal migratory fish populations that moved out of east Gippsland catchments following the extensive bushfires in 2019-20. Environmental watering in 2021-22 aims to maintain or where able build on the environmental outcomes from 2020-21. Fish ecologists from the Arthur Rylah Institute for Environmental Research recommend maintaining target low flows throughout 2021- 22 to promote the upstream dispersal and survival of new tupong recruits.

Scope of environmental watering

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

Potential environmental watering action

EXPECTED WATERING EFFECTS

Environmental objective

Wirn wirndook Yeerung (Macalister River) (targeting reach 2)1

Winter/spring low flow (300 ML/day for at least 120 days during July to November 2021 and June 2022)

  • Provide permanent wetted habitat for waterbugs and maintain water depth over riffles to enable fish passage between local habitats
  • Increase water depth to provide sustained wetting of low-level benches, limiting the encroachment of terrestrial vegetation
Fish iconPlant iconInsect icon

Spring/summer fresh(es) (one to two freshes of 700-1,500 ML/day for three to 10 days during September to December)

  • 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 mid- and higher-level benches to water woody vegetation and move organic matter into the channel to transport food resources downstream (when delivered at upper magnitude)
  • Provide flow with sufficient shear stress to scour biofilms and flush fine sediment from pools and small gaps to improve geomorphic habitat and food resources for waterbugs (when delivered at upper magnitude)

Fish iconMountain iconsPlant iconInsect icon

Spring/summer low flow (60-90 ML/day during September to February)

  • Maintain the water depth in pools and hydraulic habitat for native fish2
  • Maintain permanent wetted habitat in pools and riffles for waterbugs2
  • Provide longitudinal connectivity for local movement of platypus and rakali, as well as protection from predation, access to food sources and maintenance of refuge habitats2

Fish iconPlatypus iconInsect icon

Trigger-based summer/ autumn low flow (40-60 ML/day for five to 13 days when triggered, during December to May)

  • Maintain permanent wetted habitat in pools and riffles for fish and waterbugs to survive
  • Provide 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

Summer/autumn fresh(es) (one to three freshes of 140 ML/day for three to five days during December to March)

  • Increase water 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 dispersal of seeds and propagules from emergent vegetation throughout the reach
  • Provide flow with sufficient shear stress to flush fine sediment from small gaps to improve geomorphic habitat
Fish iconMountain iconsPlant iconInsect icon

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

  • Cue the downstream migration of Australian grayling towards the estuary for spawning
  • Additional benefits for Carran Carran (Thomson River) and the Latrobe system are expected when delivered for greater than three days:
    • fully flush the upper Thomson River estuary (when delivered for greater than three days and combined with freshes in Carran Carran (Thomson River) and contribute freshwater to the lower reaches of Durt-Yowan (Latrobe River) and wetlands

Fish icon

Autumn/winter low flow (60-90 ML/day during March to August)

  • Maintain pool and riffle habitat for waterbugs and a minimum depth over riffles to allow fish (e.g. Australian grayling, tupong and Australian bass) to migrate downstream towards the estuary habitat to spawn or breed2
  • Provide connectivity throughout the river for the local movement of platypus and rakali (water rats), as well as protection from predation and access to food
  • Provide low-velocity flow and clear water to enable the establishment of submerged vegetation2

Fish iconPlatypus iconPlant iconInsect icon

Autumn/winter fresh (one fresh of 700 ML/day for five days during July to August 2021 or May to June 2022)

  • Cue the downstream migration towards the estuary of Australian bass for spawning and of tupong for breeding
  • Increase the wetted area and improve water quality by flushing pools, providing habitat and conditions for waterbugs
  • Wet low and mid-level benches to facilitate the dispersal of emergent and fringing vegetation seeds and propagules throughout the reach

Fish iconPlant iconInsect icon

1 All freshes target reach 2 specifically. Low flows target both reach 1 and 2, but the magnitudes targeted apply to both reaches.
2 At 90 ML per day, expected watering effects are met in reach 1 and 2. At 60 ML per day, expected watering effects are met in reach 2 only.

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: 22/01/21