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Gunbower Forest is a large, flood-dependent forest situated on the River Murray floodplain in northern Victoria between Torrumbarry and Koondrook (Figure 5.2.2). Covering 19,450 ha, it is bounded by the River Murray to the north and Gunbower Creek to the south.

Gunbower Creek and Forest continue to be important places for Traditional Owners and their Nations. The Registered Aboriginal Party (RAP) in the southern region is the Yorta Yorta Nation Aboriginal Corporation. Representatives from the RAP and from Barapa Barapa Nations Traditional Owners were engaged during the preparation of the Gunbower seasonal watering proposal.

System map

2018-Northern-Gunbower-map

Environmental watering objectives in Gunbower Creek and Forest

Maintain the health and support the recruitment of plants in permanent and semipermanent wetlands Maintain and improve the health of river red gums, black box and grey box communities
Maintain and increase the healthy populations of large- and small-bodied native fish Provide flows for native fish (such as Murray cod, golden perch, carp gudgeon and freshwater catfish) to swim, feed and breed in Gunbower Creek
Provide feeding, breeding and refuge habitat for waterbirds including colonial nesting species
Increase the population of frogs in the forest by providing feeding and breeding habitat

Environmental values

Gunbower Forest contains a range of important environmental values including rare and diverse wetland habitats, vulnerable and endangered plants and animals and large areas of remnant vegetation communities (such as river red gum forest). The forest provides habitats for many bird species, and it is known to support internationally recognised migratory waterbirds.

Gunbower Creek provides important habitat for native fish (such as Murray cod, golden perch and freshwater catfish). It is a valuable refuge for native fish, and it provides a source of fish to recolonise surrounding waterways.

Social and economic values

The forest provides economic values through timber production, apiculture (bee keeping), educational courses, recreation and tourism. The forest supports numerous recreational activities when it is wet and dry. Popular activities include kayaking, canoeing, camping, photography and birdwatching. The Gunbower Heritage River Trail is a popular tourist attraction that passes through many Indigenous and European cultural heritage sites. The River Red Gum Drive is one of Victoria's iconic, four-wheeldrive routes that follows the River Murray through the Gunbower National Park.

Gunbower Creek is the major carrier for the delivery of irrigation supply to the surrounding agricultural land. The creek is also a hotspot for tourism, with businesses taking advantage of the presence of flows year-round and recreational activities (such as boating, canoeing, stand-up paddle-boarding, kayaking and fishing). The Cohuna Bridge to Bridge, a popular charity event held in autumn each year, allows participants to either swim or paddle along large sections of the creek or ride up to 50 km along the banks.

Conditions 2018

Monitoring conducted after natural floods in late 2016 detected a large population of carp in Gunbower Forest's wetlands. The carp were damaging wetland vegetation and causing high turbidity. To manage the impact of the carp, the floodplain and wetlands were intentionally left to draw down and dry after the natural inflows in late 2016, with no water for the environment delivered to the forest for the remainder of the 2016–17 year. The North Central CMA used the drying conditions to remove 1,170 kg of carp (mostly large adults) from Reedy Lagoon and Black Swamp.

Water for the environment was used to partially fill Reedy Lagoon and Black Swamp in late spring 2017. In the absence of large-bodied carp, aquatic plants flourished and were able to germinate, establish and set seed. In Reedy Lagoon, the managed delivery triggered a dense cover of vulnerable river swamp wallaby-grass. In Black Swamp, the number and distribution of aquatic plants was the highest on record and several plant species not commonly observed were recorded including river swamp wallabygrass and wavy marshwort.

High rainfall in early December 2017 increased flows in the River Murray and delivered minor flows through deeper floodrunners and creeks in upper Gunbower Forest. To maintain the carp exclusions, these flows were prevented from connecting to Reedy Lagoon and Black Swamp. In the absence of large-bodied carp, vegetation in both wetlands proliferated over summer and autumn as water levels receded. A small volume of water remains in both wetlands and is expected to persist in deeper areas to the end of 2017–18.

The improved extent and condition of aquatic vegetation in Reedy Lagoon and Black Swamp provided excellent feeding habitat for many waterbirds, including eastern great egrets and white-faced heron. It also provided breeding habitat for Australasian grebes, white-bellied sea eagles and black swans.

The success of environmental watering in Reedy Lagoon and Black Swamp highlights the benefits of coordinating deliveries of water for the environment with other management actions to maximise environmental outcomes. Carp exclusion plots, established by the Living Murray Intervention Monitoring Program in 2014–15, were again monitored in a few of the forest wetlands. These trial plots demonstrate how floodplain vegetation responds at different stages of their wetting and drying cycles in the absence of large-bodied fish (including carp) as well as grazing by waterbirds and marsupials. Plots that excluded carp, waterbirds and kangaroos had more-abundant and morediverse vegetation than plots that only excluded one species.

In 2017–18, flows in Gunbower Creek allowed large-bodied fish, especially Murray cod, to migrate, spawn, feed and breed. Since implementing managed environmental flows in Gunbower Creek in 2011, the native fish population has steadily increased. Higher flows provided in winter/spring 2017 helped maintain fish nursery habitats, and Gunbower Creek now supports a healthy population of Murray cod of varying ages and greater numbers of golden perch, silver perch and freshwater catfish. 

In mid-June 2018, water for the environment was delivered to Gunbower Forest to support river red gums and the flood-dependent understory. The water delivery was timed to maximise deliveries into the forest before irrigation orders (due to resume from 15 August) were to take up much of the capacity of Gunbower Creek. The delivery of environmental water to Gunbower Forest is planned to continue during winter/spring 2018–19.

Scope of environmental watering

Table 1 Potential environmental watering actions and objectives for Gunbower Creek and Forest

Potential environmental watering

Environmental objectives

Gunbower Forest

Inundation of Gunbower Forest floodplain, floodrunners and wetlands (fill in winter/spring and provide top-ups if a significant bird-breeding event occurs)

  • Improve the health of river red gum, black box and grey box communities 
  • Maintain/enhance healthy populations of native fish in wetlands and increase opportunities for riverine fish to access floodplain resources 
  • Maintain suitable feeding, breeding and refuge habitat for waterbirds including colonial nesting species 
  • Support a significant bird-breeding event

Semipermanent and permanent forest wetlands (fill in winter/spring and provide topups if a significant bird-breeding event occurs)

  • wetlands (fill in winter/spring and provide topups if a significant bird-breeding event occurs)
  •  Maintain the health and resilience of vegetation communities in permanent wetlands 
  • Maintain suitable feeding and refuge habitat for waterbirds 
  • Support a significant bird-breeding event

Reedy Lagoon and Black Swamp (fill in winter/ spring and provide top-ups if a significant bird-breeding event occurs)

Winter/spring fresh in Yarran Creek (variable flow rates and duration based on water levels in Gunbower Forest and flows in the River Murray and Gunbower Creek)

  • Provide connectivity between Gunbower Creek and River Murray through the Yarran Creek and Shillinglaws regulators, to increase flowing habitat for the lateral movement of native fish, turtles and seed propagules 
  • Provide migration and spawning opportunities for native fish

Extend natural flooding in Gunbower Forest floodplain, floodrunners and wetlands (with variable flow rates to maintain appropriate inundation extent)

  • Improve the health of river red gum communities 
  • Maintain/enhance healthy populations of native fish in wetlands and increase opportunities for riverine fish to access floodplain resources 
  • Maintain suitable feeding, breeding and refuge habitat for waterbirds including colonial nesting species 
  • Support a significant bird-breeding event
Reedy Lagoon and Black Swamp (top-ups in autumn/winter)
  • Maintain/enhance the health and resilience of vegetation communities in permanent wetlands 
  • Maintain suitable feeding, breeding and refuge habitat for waterbirds including colonial nesting species
Inundation of Gunbower Forest floodplain, floodrunners and wetlands (fill in autumn/winter 2019)
  • Improve the health of river red gum, black box and grey box communities 
  • Maintain/enhance healthy populations of native fish in wetlands and increase opportunities for riverine fish to access floodplain resources 
  •  Maintain suitable feeding, breeding and refuge habitat for waterbirds including colonial nesting species

Gunbower Creek

Winter low flows (up to 400 ML/day between May–August)

  • Increase the survival and maintain the growth of native fish (such as Murray cod) by maintaining access to food and habitat resources

Spring/summer high flows (targeting a gradual increase in flows up to 650 ML/day including various periods of stable flows in August– January)

  • Increase the recruitment, growth and survival of native fish (such as Murray cod) by maintaining access to breeding habitat and food resources

Year-round low flows (above 400 ML/day between August–May)

  • Maintain native fish survival and growth by increasing access to habitat and food resources

Summer/autumn low flows (above 300 ML/ day, between January–May)

  • Maintain native fish survival and growth by increasing access to habitat and food resources
Increased low flows (up to 550 ML/day yearround if unregulated conditions occur in the River Murray)1
  • Increase native fish recruitment by providing cues for migration and spawning, in line with larger flows in the River Murray 
  • Increase the growth and survival of native fish (such as Murray cod) by maintaining access to breeding habitat and food resources
Spring/summer/autumn freshes (up to 550 ML/day between October-April)1
  • Increase native fish recruitment from the River Murray populations into the Creek by providing cues for migration and spawning, in line with larger flows in the River Murray 
  • Maintain water quality below Koondrook Weir to dilute low-dissolvedoxygen water that may exit Gunbower Forest
1 Increased low flows and freshes may be provided opportunistically in Gunbower Creek if unregulated conditions eventuate in the River Murray and the Hipwell Road Channel regulator is not being used.

Risk management

In preparing its seasonal watering proposal, North Central 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 North Central CMA engaged when preparing the Gunbower Creek and Forest 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 North Central Regional Catchment Strategy and North Central Waterway Strategy.

Table 2 Partners and stakeholders engaged in developing the Gunbower Creek and Forest seasonal watering proposal

Partner and stakeholder engagement
  • Gannawarra Shire Council, Campaspe Shire Council and Cohuna Progress Association 
  • Gunbower Island Community Reference Group (with representation from the Cohuna Progress Association, bird observers, Field & Game Australia, BirdLife Australia, Gunbower Landcare Group, irrigators and general community members) 
  • Gunbower Operations Advisory Group (with representation from Goulburn-Murray Water, Parks Victoria, Department of Environment, Land, Water and Planning, Vic Forests, State Forests NSW, North Central CMA, Murray–Darling Basin Authority, Commonwealth Environmental Water Holder and the Victorian Environmental Water Holder 
  • Gunbower Technical Working Group (with representatives of Department of Environment, Land, Water and Planning [Threatened Flora and Fauna]; and specialist fish, vegetation and bird consultants and ecologists) 
  • Yorta Yorta Nation Aboriginal Corporation and Barapa Barapa Nations Traditional Owners