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Water for the environment is supplied to Durt-Yowan (Latrobe River) from Blue Rock Reservoir on the Tanjil River. Blue Rock Reservoir also supplies water for urban supply and for electricity generators and a paper mill in the Latrobe Valley.

Durt-Yowan (Latrobe River) from Rosedale to the Carran Carran (Thomson River) confluence (reach 5) is the priority reach for delivering water for the environment because it contains endangered plant communities that have good potential for rehabilitation. Capacity constraints within reach 5 mean that some of the larger freshes required to meet environmental objectives in reaches 4, 5 and 6 cannot be delivered without flooding private land. Until this can be resolved, environmental flows will be managed to within-channel levels. Where possible, flows in Durt-Yowan (Latrobe River) are coordinated with freshes in Carran Carran (Thomson River) to meet targets for the Latrobe River estuary.

Options to deliver water for the environment to Durt-Yowan (Latrobe River) via the Tyers River may be investigated in 2022-23. These options include a physical transfer of water from Blue Rock Reservoir to Moondarra Reservoir via existing infrastructure operated by Gippsland Water or a temporary administrative transfer arrangement. Delivering water via the Tyers River would increase the proportion of the Latrobe catchment that could receive water for the environment without compromising outcomes in the main target reaches of Durt-Yowan (Latrobe River). If adopted, these options are expected to benefit native in-stream and streamside vegetation and non-migratory fish within the Tyers River.

LaTrobe Pie Chart

Proportion of water entitlements in the Latrobe system held by private users, water corporations and environmental water holders on 30 June 2020

Traditional Owners
Storage manager
Environmental water holder

Environmental watering objectives in the Latrobe River

Fish icon
Maintain or increase native fish (migratory, resident and estuary) populations
Landscape icon
Maintain or increase in-stream geomorphic diversity
Platypus icon
Maintain or improve the extent of platypus and rakali (water rats) populations
Maintain the abundance of freshwater turtle populations
Plant icon
Improve the condition and increase extent and diversity of submerged, emergent and streamside native vegetation. Reduce the extent and density of invasive plants
Insect icon
Increase the abundance of all macro- and micro-invertebrates
Water icon
Avoid adverse water-quality conditions (such as high salinity) in the lower reaches of Durt-Yowan (Latrobe River) and its estuary

System map

Environmental values

The upper reaches of Durt-Yowan (Latrobe River) flow through state forest and are relatively intact and ecologically healthy. They have continuous stands of river red gums and intact streamside vegetation, and they support native animals, including barred galaxias, river blackfish, Gippsland spiny crayfish and nankeen night herons.

Durt-Yowan (Latrobe River) below Lake Narracan is regulated and highly degraded due to historic river management practices. Most large woody habitat has been removed from the river, and many sections have been artificially straightened. These practices have caused significant erosion and widened the channel, which has in turn reduced the quality and quantity of habitat for aquatic plants and animals.

Endangered and vulnerable vegetation is found in all but the most modified sections of Durt-Yowan (Latrobe River). The banks along the lower reaches support stands of swamp scrub, characterised by swamp paperbark and tea tree. Mature river red gums grow adjacent to the lower Latrobe wetlands and provide nesting habitat for sea eagles and other birds of prey that hunt in the wetlands. Durt-Yowan (Latrobe River) supports several native estuarine and freshwater fish, including black bream, Australian bass, Australian grayling and short- and long-finned eel. The river also provides habitat and supports feeding and breeding conditions for platypus, rakali (water rats) and freshwater turtles.

Durt-Yowan (Latrobe River) and its tributaries provide an essential source of freshwater to the Gippsland Lakes system, of which the lower Latrobe wetlands are an important component.

Recent conditions

The Durt-Yowan (Latrobe River) catchment experienced above-average temperatures throughout most of 2021-22, and above- average rainfall during winter and spring resulted in several overbank flood events and sustained high flows for most of the year. A large rain event in June 2021 caused Blue Rock Reservoir to spill, resulting in widespread flooding in the lower reaches and the estuary, with a high flow peak of 34,000 ML/d recorded at Kilmany. Due to above-average inflows and only minor use of water for the environment since 2018-19, the full environmental entitlement was available at the start of the 2021-22 water year and was sustained throughout the season.

Water for the environment was managed in line with a wet climate scenario throughout 2021-22, and all planned watering actions were met or exceeded with natural flows for the second consecutive year. These natural flows provided several large flow events that are needed to support key ecological and geomorphological processes and cannot be delivered through managed releases of water for the environment. A flow constraint in reach 5 of Durt-Yowan (Latrobe River) currently limits the ability to deliver the full environmental water entitlement from Blue Rock Reservoir under average-to-wet conditions, and this is the third year in a row where all deliverable flow components required for Durt-Yowan (Latrobe River) have been achieved with high natural flows throughout winter and spring. This has helped freshen the Latrobe estuary and enhanced environmental outcomes in all reaches.

Flows over the past year have created the perfect conditions in the Latrobe estuary for fish breeding, with commercial eel fishers in the area observing estuary perch and Australian bass recruitment at a scale that many have never seen before. Fish surveys conducted in Durt-Yowan (Latrobe River) and its tributaries in early 2021 and 2022 detected many young-of- year tupong and Australian bass and a 25 percent reduction in the carp population since 2015. Fish ecologists from the Arthur Rylah Institute for Environmental Research advised that maintaining minimum low-flow targets throughout 2022-23 will continue to facilitate the upstream dispersal and increase the survival of new tupong recruits.

Traditional Owner cultural values and uses

The Gunaikurnai have had a continued connection to Gunaikurnai Country for over 27,000 years, including with the waterways in the Latrobe system.

For the Gunaikurnai as traditional custodians, 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.

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 Owners with traditional knowledge. Traditional Owners’ guidance about objectives and values was received from GLaWAC via the Gunaikurnai Cultural Water Team. This engagement is planned to continue in the 2022-23 water year.

GLaWAC is working in partnership with West Gippsland CMA to determine how cultural values and uses can be considered in planning for water for the environment. For the Latrobe system, this includes:

  • undertaking Aboriginal Waterways Assessments to examine cultural values and uses and incorporating the findings of assessments into the Latrobe Environmental Water Requirements Investigation
  • identifying primary objectives under the modified water regime
  • expressing preliminary outcomes: watering actions that recognise and promote:

- healthy Country

-    the importance of the Latrobe River system to the Gunaikurnai songline of pelican and musk duck and their water quality and habitat requirements

- implementation of cultural resource management

- waterways as meeting places, pathways and boundaries

- preliminary accommodation of the water quality and management requirements of species with cultural values and uses.

GLaWAC is sharing with the West Gippsland CMA its knowledge of plant and animal species of cultural significance in and around the waterways of the Latrobe Valley and the importance of specific watering decisions to support them.

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 Latrobe estuary, Dowd Morass, Sale Common and Heart Morass, and associated freshwater habitats as 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 2.2.1, West Gippsland CMA considered how environmental flows could support values and uses, including:

  • water-based recreation (such as fishing and water skiing)
  • riverside recreation and amenity (such as birdwatching)
  • socioeconomic benefits (such as commercial fishing, tourism and improved water quality for domestic, irrigation and stock use).

If the timing or management of planned environmental flows may be modified to align with a community benefit, this is acknowledged in Table 1 with the following icon.

Kayak icons

Watering planned to support water sports activities (e.g. water skiing)

West Gippsland CMA coordinates with the Lake Narracan Ski Club to plan the timing of releases of water for the environment so that they do not affect water levels in the lake during water skiing events held between January and March.

Scope of environmental watering

Table 2.2.1 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 2.2.1 Potential environmental watering actions, expected watering effects and associated environmental objectives for Durt-Yowan (Latrobe River)

Potential environmental watering action

Expected Watering Effects

Environmental objectives

Durt-Yowan (Latrobe River) (targeting reach 5)

Winter/spring low flow (620 ML/day during July to November 2022 and June 2023)

  • Wet benches to maintain habitat, support the growth of emergent macrophyte vegetation and limit the encroachment of terrestrial vegetation
  • Maintain oxygen levels in pools and maintain sediment (sands and silts) in suspension to prevent pools from filling and depositing on substrates, helping to maintain habitat for waterbugs, turtles, aquatic mammals and breeding substrate for river blackfish
  • Maintain longitudinal connectivity to allow movement/dispersal of native fish, turtles, platypus and rakali (water rats)
Fish iconMountain iconsPlatypus iconTurtle iconPlant iconInsect iconWater drop icon

Summer/autumn low flow (250-380 ML/day during December to May)

  • Maintain an adequate depth in pool habitat to support native fish, turtles, platypus and rakali (water rats) and submerged vegetation
  • Limit encroachment by terrestrial vegetation and support the growth of emergent macrophyte vegetation
  • Mix pools to maintain oxygen levels suitable for aquatic animals
Fish iconPlatypus iconTurtle iconPlant iconInsect iconWater drop icon

Summer/autumn river freshes (three to six freshes of 920 ML/day for one to five days during December to May)

Kayak icons

Water-quality fresh (one-day duration):

  • freshen water quality in pools to support fish, waterbug and zooplankton communities
  • provide sufficient velocity to turn over and flush sediments (sands and silts) from pools, scour algae from hard surfaces and clean fine sediment from substrates, including river blackfish nesting habitats

Fish and vegetation fresh (three to five days duration):

  • Objectives listed for the one-day fresh and additional objectives:
  • wet benches to support the growth of emergent macrophyte vegetation
  • provide longitudinal connectivity (including over benches for Australian grayling) for native fish, platypus and rakali (water rats)
Fish iconMountain iconsPlatypus iconPlant iconInsect iconWater drop icon

Summer/autumn estuary fresh(es) (one to three freshes of 2,200 ML/ day for seven to 10 days during December to May) Note: this is a combined magnitude with Carran Carran (Thomson River) over the equivalent period; a contribution of at least 1,280 ML/ day from Carran Carran (Thomson River) is required.

Kayak icons

Objectives listed for the three-to-five-day river fresh and additional objectives for the Latrobe River estuary:

  • upper estuary: fully flush with freshwater to support submerged vegetation, provide adequate oxygen levels for aquatic animals, transport silt, wet benches and deliver freshwater to connected wetlands
  • mid-estuary: partially/fully flush the upper layer of the water column to improve water quality, support emergent macrophytes, provide freshwater habitat and associated food sources for freshwater fish and provide breeding opportunities for estuary fish
  • lower estuary: partially flush the upper layer of the water column; a flow of this magnitude will also provide opportunities to fill the lower Latrobe wetlands
Fish iconMountain iconsPlatypus iconPlant iconWater drop icon

Scenario planning

Table 2.2.2 outlines potential environmental watering and expected water use under a range of planning scenarios. The estimated water demands for planned watering actions presented in Table 2.2.2 do 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 Latrobe River under wet and possibly average scenarios should be achievable with the available supply.

Maintaining target low flows throughout the year to provide habitat and support vegetation growth, and delivering summer/ autumn freshes to maintain water quality and provide specific opportunities for fish movement, are high priorities under all climate scenarios. These flows are necessary to consolidate environmental outcomes achieved on the back of wetter conditions in 2020-21 and 2021-22.

Most of the recommended flows are likely to be fully achieved through a combination of natural events, operational releases, passing flows and environmental deliveries under average and wet climate scenarios. The magnitude and duration of low flows and freshes can be lower under drought and dry climate scenarios, where the focus is on maintaining current ecological values rather than improving them. However, there will be less natural inflow and lower operational releases under drought and dry climate scenarios, and there may not be enough water for the environment to deliver all of the required watering actions, even at the lower end of their recommended range.

Under drought and dry climate scenarios, the available water for the environment will be used to deliver summer/autumn low flows and a small number of summer/autumn freshes. Summer/autumn flows are prioritised, because critically low flow at this time of year can lead to poor water quality and reduce available habitat, which in turn will threaten populations of native fish, platypus and turtles. Passing flows and natural inflows from unregulated tributaries are likely to provide some flow through the system during winter and spring. Water for the environment will only be used in winter or spring under drier climate scenarios if a lack of flow represents an immediate risk to aquatic fauna.

It is unlikely that target summer/autumn low flows will be able to be maintained continuously from December to May under a drought scenario, and up to four freshes will likely be needed to prevent adverse water-quality events in reach 5. There may only be enough supply to deliver three summer/autumn freshes under a drought scenario, and at least one of these should be delivered for three to five days to provide an opportunity for fish movement and to water native vegetation on low channel benches. More freshes with larger magnitudes and longer durations (up to 10 days) may be coordinated with flows in Carran Carran (Thomson River) under dry, average and wet climate scenarios to meet environmental flow objectives in the Latrobe River estuary.

There are no true carryover provisions in the Latrobe system. Rather, the VEWH maintains an ongoing share of storage capacity in Blue Rock Reservoir. Under a drought scenario, it will be important to ensure a minimum of 2,500 ML is maintained in storage at the end of 2022-23 to help deliver critical watering actions in 2023-24. Natural inflows are likely to meet some of the planned watering actions under dry to wet climate scenarios in 2022-23 and result in some leftover water at the end of the year. This leftover water will help support potential watering actions in 2023-24, and no specified carryover target has been set or prioritised for those scenarios.

Planning scenario table

Table 2.2.2 Potential environmental watering for Durt-Yowan (Latrobe River) under a range of planning scenarios

Planning scenario

Drought

Dry

Average

Wet

Expected river conditions

  • Small contributions to low flows from unregulated reaches and tributaries
  • Passing flows reduced, more likely over summer/autumn
  • Possible spills from storages in spring, minor flood levels may occur
  • Some natural flows contributing to low flows and freshes
  • Passing flows may be reduced, more likely over summer
  • Regular spills from storages in spring, and minor to moderate flood levels may occur
  • Natural flows and/ or passing flows likely to meet low- flow requirements
  • Large and frequent spills from storages, and moderate to major flood levels may occur
  • Natural flows and/ or passing flows likely to meet low- flow requirements

Expected availability of water for the environment

  • 18,700 ML
  • 20,700 ML
  • 25,700 ML
  • 33,700 ML

Potential environmental watering – tier 1 (high priorities)

Tier 1a (can be achieved with predicted supply)

  • Summer/autumn low flow (partially delivered)
  • Summer/autumn river freshes (two of lower duration, one of mid-duration [four days])
  • Summer/autumn low flow
  • Summer/autumn river freshes (four of lower duration and two of mid- duration [three days])
  • Replace one mid- duration summer/ autumn river fresh with an estuary fresh, if conditions allow
  • Winter/spring low flow (continuous)
  • Summer/autumn low flow
  • Summer/autumn river fresh (one of lower duration and three of mid-duration [four days])
  • Replace all mid-duration summer/autumn river freshes with estuary freshes, if conditions allow
  • Winter/spring low flow
  • Summer/autumn low flow
  • Summer/autumn river fresh (one of lower duration and three of upper- duration [five days])
  • Replace all mid-duration summer/autumn river freshes with estuary freshes, if conditions allow
 

Tier 1b (supply deficit)

  • Winter/spring low flow (lower duration)
  • Summer/ autumn low flow (continuous)
  • Tier 1a mid- duration summer/ autumn river fresh replaced with a summer/ autumn estuary fresh (delivered for seven days)
  • One additional summer/autumn river fresh (of lower duration)
  • Winter/spring low flow (lower duration)
  • One additional summer/autumn estuary fresh

N/A

Potential environmental watering – tier 2 (additional priorities)

N/A

Possible volume of water for the environment required to achieve objectives

  • 16,200 ML (tier 1a)
  • 28,300 ML (tier 1b)
  • 14,400-20,400 ML(tier 1a)
  • 13,400 ML (tier 1b)
  • 7,400-27,2001 ML (tier 1a)
  • 8,600-15,200 ML (tier 1a)

Priority carryover requirements for 2023-24

  • 2,500 ML
  • 0 ML

1 While the upper demand is in excess of available supply, it is expected that some of the events will be at least partially met with natural inflows under an average scenario

Engagement

Partners and stakeholders engaged by West Gippsland CMA in developing seasonal watering proposals for the Latrobe River, lower Latrobe wetlands, Thomson River and Macalister River systems and other key foundation documents that have directly informed the proposals

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

Partner and stakeholder engagement
  • Greening Australia
  • Latrobe Valley Field Naturalist Club Inc.
  • Native Fish Australia
  • Parks Victoria
  • Southern Rural Water
  • Gippsland Water
  • Department of Environment, Land, Water and Planning
  • East Gippsland CMA
  • Individual landholders
  • Port of Sale Heritage Cruises
  • Field & Game Australia
  • VRFish
  • Arthur Rylah Institute (Department of Environment, Land, Water and Planning)
  • Gunaikurnai Land and Waters Aboriginal Corporation

Page last updated: 01/07/22