Macalister River

Wirn wirndook Yeerung (Macalister River) flows from Mt Howitt in the Alpine National Park and joins Carran Carran (Thomson River) south of Maffra (Figure 2.4.1). The river winds its way in a south-easterly direction through mostly forested, confined valleys and narrow floodplains above 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 Wirn wirndook Yeerung (Macalister River).

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 greater 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. Most irrigation water is diverted at Maffra Weir, and flow downstream of the weir is lower than natural year-round. 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 delivery of water for the environment for migratory fish objectives mainly focuses on reach 2. All other objectives apply to both reaches 1 and 2.

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

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

Increase the abundance of platypus and rakali (water rats)

Improve native emergent (non-woody) and fringing (woody) vegetation in the riparian zone.

Reinstate or instate submerged aquatic vegetation.

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

“Traditionally, the Macalister River is a very important river to the Gunaikurnai people. It is a pathway that connects from the Alps to the heart of Gippsland. It is a pathway to ceremonial grounds and a known, special men’s place to Elders. Its traditional name is Wirn wirndook Yeerung, which translates to ‘song of the male fairy wren’.

“Yeerung is the men’s totem. This river has many cultural resources and extensive important sites along the whole system.”

The Gunaikurnai have had a continued connection to Gunaikurnai Country for over 27,000 years, including with the waterways in the Latrobe system (into which Wirn wirndook Yeerung [Macalister River] feeds). For the Gunaikurnai as Traditional Owners, there are immense challenges to heal, protect and manage Country, which has been drastically altered since colonisation. The Gunaikurnai see all of Country as interconnected with only separation between clan groups, not cultural landscapes of land, waterways, coasts, oceans and natural and cultural resources. The cultural landscape is dependent on culture and Aboriginal management.

The Gunaikurnai Land and Waters Aboriginal Corporation (GLaWAC) is 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 to 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 in 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 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, 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.

Watering requirements to support cultural values and uses include:

timing the delivery of water for the environment 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.

West Gippsland CMA engaged with the GLaWAC Cultural Water Team about watering priorities for 2022-23.

Social, recreational and economic values and uses

In planning the potential watering actions in Table 2.4.1, 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)
socioeconomic benefits (such as preventing erosion and the potential loss of private and public land).

Recent conditions

Rainfall and temperatures in the Macalister catchment were above average throughout most of 2021-22, with periods of very much above-average rainfall in spring 2021. It was the second consecutive year of naturally wet conditions. Strong inflows to Lake Glenmaggie in July 2021 saw the storage quickly fill and spill, and there were multiple bankfull flow events above 4,000 ML/d in reaches 1 and 2. Allocations of high-reliability water shares opened at 100 percent, and low-reliability water share allocations reached 100 percent by March 2022. Carryover from 2020-21 was lost when Lake Glenmaggie spilled, but there was a sufficient supply of water for the environment to meet planned demands.

Delivery of water for the environment in the Macalister system was managed according to a wet climate scenario throughout 2021-22. All planned watering actions for 2021-22 were met, mainly through a combination of natural and operation flows. Water for the environment is expected to be used to help deliver an autumn fresh to cue fish migration and facilitate fish passage.

Wet conditions throughout Gippsland in 2020 provided ideal breeding conditions for many native fish, and large numbers of young-of-year tupong were detected in the Macalister River in March 2021. Follow-up fish surveys in February 2022 also found large numbers of juvenile tupong and older fish, which indicates conditions in 2021 contributed to high survival rates and the second year of successful breeding. These results show that the Macalister River continues to provide important habitat for coastal migratory fish species within the Gippsland region.

Scope of environmental watering

Table 2.4.1 describes the potential environmental watering actions in 2022-23, their expected watering effect (that is, the intended physical or biological effects of the watering action) and the longer-term environmental objectives they support. Each environmental objective relies on one or more potential environmental watering actions and their associated physical or biological effects.

Table 2.4.1 Potential environmental watering actions, expected watering effects and associated environmental 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 2022 and June 2023)	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
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 the recruitment of juveniles (e.g. Australian grayling, tupong, common galaxias, Australian bass and short- and long-finned eels) from marine/ estuarine environments Wet mid-level benches to water woody vegetation, limit the encroachment of terrestrial vegetation and facilitate the dispersal of emergent and fringing vegetation seeds and propagules throughout the reach
Spring/summer low flow (60-90 ML/day during September to February)	Maintain the water depth in pools and hydraulic habitat for native fish Maintain permanent wetted habitat in pools and riffles for waterbugs Provide longitudinal connectivity for local movement of platypus and rakali (water rats), as well as protection from predation, access to food sources and maintenance of refuge habitats Note: 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.
Spring/summer low flow (60-90 ML/day during September to February)	Maintain the water depth in pools and hydraulic habitat for native fish Maintain permanent wetted habitat in pools and riffles for waterbugs Provide longitudinal connectivity for local movement of platypus and rakali (water rats), as well as protection from predation, access to food sources and maintenance of refuge habitats Note: 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.
Trigger-based summer/ autumn low flow (40- 60 ML/day for five to 13 days during December to May) Trigger: extended periods of reduced passing flow or no flow being released from Lake Glenmaggie	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
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
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
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 breed 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 vegetation Note: 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.
Autumn/winter fresh (one fresh of 700 ML/day for five days during July to August 2022 or May to June 2023)	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

¹ All freshes target reach 2 specifically. Low flows target both reach 1 and 2, but the magnitudes targeted apply to both reaches.

Scenario planning

Table 2.4.2 outlines potential environmental watering and expected water use under a range of planning scenarios.

Providing year-round low flows to maintain habitat connectivity for aquatic animals in Wirn wirndook Yeerung (Macalister River) is the highest-priory watering action under all climate scenarios. Year-round operational passing flows of 60 ML per day will meet the minimum low-flow objectives for reach 2. Increasing flows to 90 ML per day has additional benefits for environmental values in reach 1 and is therefore preferred. It is expected to be achieved under all scenarios unless carryover from 2021-22

is lost due to managed spill releases, and it may cause a deficit in supply for the remaining priorities, which is possible under average and wet scenarios. If this occurs, increasing the magnitude to 90 ML per day will only be prioritised in November after the delivery of a spring fresh and during mid-April to mid-August, when water from the upper catchment is harvested to fill Lake Glenmaggie, and little to no consumptive orders on top of the operational passing flow are released downstream. Low flows delivered at the upper end of the recommended range aim to provide more habitat and food to help grow waterbug, fish and platypus populations and exclude terrestrial vegetation from the main channel.

Under a wet scenario, increasing the low flow to 300 ML per day during winter and spring is preferred to wet the lower benches over a sustained period. The estimated water demand for this action presented in Table 2.4.2 does not account for potential unregulated flows. As seen in recent years, natural tributary inflows are likely to achieve many of the planned watering actions under wetter climate scenarios, so most or all of the tier 1a and tier 1b actions proposed for the Macalister River under the wet scenario should be achievable with the available supply.

Under drought and dry climate scenarios, low inflows to Lake Glenmaggie may trigger reduced operational passing flows any time over summer and autumn. Maintaining low flows of at least 60 ML per day is the target under all scenarios, but if that cannot be achieved under drought or dry scenarios, water for the environment may be used to deliver trigger-based low flows of 40 ML per day for five to 13 days and then a summer/autumn fresh. This combination of actions aims to avoid a serious water-quality outcome and the loss of environmental values — regular water quality monitoring would occur if that was likely — while also conserving available supply. Additional summer/autumn freshes may be provided under average and wet climate scenarios.

Delivering at least one fresh of 350 ML per day in autumn and 700 ML per day in spring (both for five days) is a high priority under all climate scenarios to provide a migration trigger for native fish to move into or out of the system to complete their life cycles. An additional 700 ML per day fresh may be delivered in late autumn or winter to increase fish migration. These events are necessary every year under average and wet climate scenarios to ensure regular recruitment and align with environmental cues in the broader landscape. They are generally less important in dry our drought scenarios, but they are important to deliver even under drier conditions in 2022-23 to consolidate recent population growth and to potentially supplement populations in east Gippsland that were affected by the 2019-20 bushfires. Several other large freshes are recommended to slow the recession following spills from Lake Glenmaggie, but they are a lower priority and will likely be at least partly met by operational releases under most scenarios.

Under all climate scenarios, a minimum of 1,900 ML is prioritised for carryover into 2023-24 to meet critical early-season low- flow requirements in Wirn wirndook Yeerung (Macalister River).

Planning scenario table

Table 2.4.2 Potential environmental watering for the Macalister system under a range of planning scenarios

Planning scenario	Drought	Dry	Average	Wet
Expected river conditions	Limited natural flow; freshes or high flows are unlikely Passing flows at Maffra Weir may be reduced	Possible spills from Lake Glenmaggie in spring, minor flood levels may occur Passing flows at Maffra Weir may be reduced	Regular spills from Lake Glenmaggie in spring, minor to moderate flood levels may occur	Large and frequent spills from Lake Glenmaggie, moderate to major flood levels may occur
Expected availability of water for the environment	21,700 ML	25,000 ML¹	27,000 ML¹	31,500 ML¹
Potential environmental watering – tier 1 (high priorities)	Tier 1a (can be achieved with predicted supply)
	Spring fresh (one fresh) Spring/summer low flow (partial: delivered at upper magnitude in November only, following fresh) Trigger-based summer/autumn low flow Summer/autumn fresh (one fresh, of lower duration) Autumn fresh (one fresh) Autumn/winter low flow Autumn/winter fresh (one fresh)	Spring fresh (one fresh) Spring/summer low flow Trigger-based summer/autumn low flow Summer/autumn fresh (one fresh, of lower duration) Autumn fresh (one fresh) Autumn/winter low flow Autumn/winter fresh (one fresh)	Spring fresh (one fresh) Spring/summer low flow² Spring/summer fresh following 1,500 ML/d spill (one fresh)³ Summer/autumn freshes (three freshes) Autumn fresh (one fresh) Autumn/winter low flow² Autumn/winter fresh (one fresh)	Spring fresh (one fresh) Spring/summer low flow² Spring/summer fresh following 3,000 ML/d spill (one fresh) Summer/autumn freshes (three freshes) Autumn fresh (one fresh) Autumn/winter low flow² Autumn/winter fresh (one fresh)
	Tier 1b (supply deficit)
	Spring/summer low flow (upper magnitude continuous)	N/A		Winter/spring low flow
Potential environmental watering – tier 2 (additional priorities)	N/A
Possible volume of water for the environment required to achieve objectives	18,200 ML (tier 1a) 4,000 ML (tier 1b)	21,800 ML (tier 1a)	25,200 ML (tier 1a)	24,100 ML (tier 1a) 28,800 ML (tier 1b)
Priority carryover requirements for 2023-24	1,900 ML

¹ Carryover from 2021-22 may be forfeited in the event of spill releases from Lake Glenmaggie.

²Continuous delivery is a tier 1a action unless carryover is lost to spill. If this occurs, delivering the low flow at the upper magnitude is prioritised from July to August 2022, November 2022 and April to June 2023 (60 ML per day at other times).

³Tier 1a action unless carryover lost to spill: this action will not be prioritised if there is insufficient supply.

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: 01/07/22