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Covering 19,450 hectares, Gunbower Forest is bounded by the River Murray to the north and Gunbower Creek to the south. It is an internationally significant site under the Ramsar Convention and forms part of the Living Murray Gunbower–Koondrook–Perricoota icon site. River regulation and water extraction from the River Murray and Gunbower Creek has reduced the frequency, duration and magnitude of flood events in Gunbower Forest over the long term. This has affected the extent and condition of habitat and the health of dependent animal communities.

Gunbower Creek is managed primarily as an irrigation carrier and supplies the Torrumbarry Irrigation Area from the River Murray. The daily variation in the creek through spring, summer and autumn is much higher now than under natural conditions due to irrigation demand. This results in significant ecological impacts including impacts on native fish populations. Environmental water is used to smooth out the variation by filling the gaps in flows caused by irrigation demand within the creek. This supports fish migration and breeding and promotes other ecological processes while maintaining water delivery for irrigation needs. Flows linking the creek to the Gunbower Forest floodplain and the River Murray can be restored through environmental watering and are vital to enhance ecosystem functioning (such as carbon exchange).

The Living Murray structural works program in the middle and lower forest was completed in 2013. The works allow up to 3,800 hectares of the wetlands and floodplain to be watered with considerably less water than would be required under natural conditions. The works enable efficient watering through Gunbower Creek of the forest to maintain wetland and floodplain condition.

System map

Murray System

Environmental watering objectives in Gunbower Creek and Forest

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Provide feeding, breeding and refuge habitat for waterbirds including colonial nesting species
Fish icon
Use flows to connect Gunbower Forest to Gunbower Creek enabling fish, insects, crustaceans, molluscs, worms and carbon to move between them, supporting the life cycle of Gunbower’s native fish
Landscape icon
Maintain the form of the creek bank and channel, and a diversity of creek-bed surface to support all stream life
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Maintain populations of small-bodied fish species in forest wetlands and rehabilitate large- and small-bodied native fish communities in Gunbower Creek
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Improve the resilience of wetland plant life and help river red gums recover from damage they experienced in the millennium drought

Environmental values

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

Gunbower Creek provides important habitat for native fish such as Murray cod, trout cod and freshwater catfish. Due to the diversity of fish in the creek, it is considered to be a valuable refuge and source of fish for the recolonisation of surrounding waterways.

Social and economic values

Gunbower Creek and Forest are both valuable sites from a cultural and socioeconomic perspective. Local Aboriginal communities have a strong connection to the Gunbower Forest area. The forest provides social and economic values through timber production, bee keeping, recreation and tourism. Recreational activities include boating, fishing and bird watching and it's the major carrier for the delivery of irrigation water to surrounding productive farmlands.

Conditions mid-2016

Gunbower Forest has received four years of consecutive flooding as a result of natural and managed events. 

From early September to mid-November 2015, nearly 29,000 ML of environmental water was delivered through Gunbower Forest. It was mainly delivered through the Hipwell Road Channel Regulator but for the first time water was also delivered through newly refurbished regulators in the lower landscape (the Yarran Creek, Black Swamp, Reedy Lagoon and Little Gunbower Lagoon regulators) to inundate areas of permanent and semipermanent wetlands. Environmental water was delivered to enhance the resilience of wetland plants, provide feeding habitat for waterbirds and enable native fish to move and carbon and nutrient cycling between the creek and forest.

The water delivered in 2015–16 inundated over 2,800 hectares of the forest including about 1,720 hectares of river red gums and 1,112 hectares of wetlands. Field observations showed that river red gums have responded with a flush of new growth and are in a better condition to withstand future dry conditions.

A diversity of aquatic plants germinated in the wetlands in response to the watering, with an excellent response in those areas that received water in the early spring delivery. For the second year in a row river swamp wallaby grass (a threatened plant species) germinated, which is important to replenish the wetland seed bank across the forest.

The high-value permanent and semipermanent wetlands in the lower part of Gunbower Forest have provided critical refuge areas in the landscape for waterbirds and source populations of plants. The importance of these areas was shown in the strong response to the 2015 environmental watering. A number of waterbirds used the resources in the wetlands for feeding and breeding during the 2015 watering including large numbers of black swans, Australian wood ducks, white-bellied sea eagles, yellow-billed spoonbills and great egrets. A small colony of cormorants (40 nests) was recorded breeding in the Little Reedy Wetland complex.

Environmental water was provided through Gunbower Creek to support native fish in autumn and winter, during the off-irrigation season. Traditionally, the creek was drawn down to a series of disconnected deep pools at the end of the irrigation season: this is now recognised as a major limiting factor to the survival of juvenile fish, particularly Murray cod. Providing environmental water during this period enables continued connectivity between habitats and food resources to support native fish.

Strong recruitment (when animals survive to settlement or maturity) of Murray cod in Gunbower Creek was observed through monitoring in 2014, corresponding to the delivery of environmental watering designed specifically to trigger breeding of Murray cod in spring and early summer in 2013–14. In 2015–16 the North Central Catchment Management Authority received many anecdotal reports of juvenile Murray cod being caught downstream of Cohuna, indicating that juvenile and adult Murray cod are benefiting from the creek management with winter, breeding and movement flow components. Despite this, the overall Murray cod population in Gunbower Creek requires ongoing environmental management for it to recover and become self-sustaining in the long term.

Scope of environmental watering

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

Potential environmental watering

Environmental objectives

Gunbower Forest

Winter/spring watering of Reedy Lagoon and Black Swamp (top-up flows as required in July–December)

  • 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 if one is triggered naturally

Provide top-ups in autumn/winter for Reedy Lagoon and Black Swamp

  • 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

Winter/spring watering of Pig Swamp and associated floodrunners

  • Improve the health of vegetation communities (including river red gums, sedgy riverine and tall marsh) in the semipermanent wetland
  • Improve suitable feeding, breeding and refuge habitat for waterbirds, frogs and other water-dependant animals

Winter/spring connectivity flows between Gunbower Creek and River Murray through Yarran Creek and Shillinglaws regulators

  • Promote lateral movement of fish, turtles and seed propagules between the River Murray and Gunbower Creek

Provide an extension of 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 if one is triggered naturally

Gunbower Creek

Winter baseflows (up to 400 ML/day between July–August and May–June)

  • Maintain food and habitat resources for native fish including the recently recruited Murray cod in Gunbower Creek
  • Maintain native fish access to resources

Spring/summer high flows (targeting a gradual increase in flows up to 700 ML/day including various periods of stable flows in August–January)

  • Promote conditions for spawning and larvae survival
  • Maintain native fish access to habitat and food resources, including recently recruited juvenile fish

Summer/autumn high flows (above 300 ML per day, between January to May)

  • Maintain native fish access to habitat and food resources including recently recruited juvenile fish

Scenario planning

The scale of the floodplain watering in Gunbower Forest will be determined by climatic conditions, delivery capacity and environmental water availability.

The main objective for 2016–17 is to provide a drying regime to the majority of the permanent and semipermanent wetlands. Drying aims to reduce the number of carp across the forest: they have bred in large numbers in the last two seasons of environmental watering after a large carp invasion in the natural floods between 2010–2012.

Therefore in drought conditions, watering is only planned to occur at two very high-priority wetlands (Reedy Lagoon and Black Swamp). The two wetlands will provide drought refuge for waterbirds and other water-dependent animals and also maintain wetland plants. Top-up flows to ensure the wetland plants remains in good health may be provided in autumn/winter if another very dry season is predicted in 2017–18: there would also be planning for carryover water into the next season to meet the permanent wetland demands.

Watering of Pig Swamp is a priority under all possible conditions except drought. Located in upper Gunbower Forest, this semipermanent wetland was disconnected from the irrigation network as part of a Goulburn-Murray Water water savings project in 2007 and no longer receives irrigation outfalls or natural flooding except in very large events when flows in the River Murray are above 50,000 ML per day. Watering will support stressed river red gums and wetland vegetation that have not received any water since the 2011 floods.

In wet years, higher flows (above 20,000 ML per day for two weeks) in the River Murray may result in natural flooding and could provide opportunities to support lateral connectivity between the forest, creek and the Murray system. If the duration of higher flows exceeds three weeks in the River Murray, moderate levels of flooding will naturally occur in the forest. Environmental water may be used to extend the duration and extent of flooding to improve the health of the floodplain ecosystem still recovering from the millennium drought.

If there is significant bird breeding, environmental water may be delivered to help maintain appropriate inundation depth and area to help the waterbirds fledge.

Gunbower Creek is a highly regulated system. As a result, natural conditions do not greatly influence the objectives or flow requirements in the system. Environmental water management will aim to support all aspects of native fish life cycles, ensuring there is sufficient habitat and food resources for native fish throughout the year.

The highest priority for watering in Gunbower Creek is maintaining flowing habitat to support juvenile native fish through winter when there is no irrigation water and improvement works over winter are occurring in the system. Additionally, delivery of environmental water to smooth out flows during the irrigation period and provide summer stable flows will be prioritised to promote opportunities for breeding and larval dispersal, particularly for Murray cod which can abandon their nests in response to sudden changes in flow height (a common feature of irrigation water delivery patterns). If sufficient water is available, additional flow components (such as increased base flows - or low flows) will be targeted to support fish movement and enable native fish to access different habitats.

Table 2 Potential environmental watering for Gunbower Creek and Forest under a range of planning scenarios

Planning scenario

Drought

Dry

Average

Wet

Expected river conditions

  • No natural inflows into Gunbower Forest
  • Natural inflows into Gunbower Forest unlikely
  • Natural inflows into Gunbower Forest are likely in winter/spring but unlikely to be significant
  • Overbank flows may occur in winter/spring

Potential environmental watering – tier 1 (high priorities)

  • Top-up watering of Reedy Lagoon and Black Swamp
  • Gunbower Creek winter baseflows
  • Gunbower Creek spring/summer high flows
  • Top-up watering of Reedy Lagoon and Black Swamp
  • Gunbower Creek winter baseflows
  • Gunbower Creek spring/summer high flows
  • Gunbower Creek summer/autumn high flows
  • Top-up watering of Reedy Lagoon and Black Swamp
  • Winter/spring watering Pig Swamp
  • Gunbower Creek winter baseflows
  • Gunbower Creek spring/summer high flows
  • Gunbower Creek summer/autumn high flows
  • Winter/spring watering Pig Swamp
  • Winter/spring connectivity flows
  • Gunbower Creek winter baseflows
  • Gunbower Creek spring/summer high flows
  • Gunbower Creek summer/autumn high flows

Potential environmental watering – tier 2 (additional priorities)

  • Top-up watering of Reedy Lagoon and Black Swamp (autumn)
  • Gunbower Creek summer/autumn high flows

·          

  • Top-up watering of Reedy Lagoon and Black Swamp (autumn)
  • Winter/spring watering Pig Swamp
  • Top-up watering of Reedy Lagoon (autumn)
  • Winter/spring connectivity flows
  • Extension of natural inundation of Gunbower Forest floodplain, floodrunners and wetlands
  • Gunbower Creek spring increased flows

Possible volume of environmental water required to meet objectives1, 2

  • 23,000 ML (tier 1)
  • 6,000 ML (tier 2)
  • 28,000 ML (tier 1)
  • 1,550 ML (tier 2)
  • 28,000 ML (tier 1)
  • 4,050 ML (tier 2)
  • 50,000 ML (tier 1)
  • 6,500 ML (tier 2)

Priority carryover requirements

  • 4,000 ML
  • 4,000 ML
  • 2,000 ML
  • N/A

1 Represents the estimated volume of water required to underwrite the losses associated with the delivery of consumptive water en route (except for discrete wetland watering actions).

2 Environmental water requirements for tier 2 are additional to tier 1 requirements.

Risk management

In preparing its seasonal watering proposal, North Central Catchment Management Authority considered and assessed risks and identified mitigating strategies relating to the implementation of environmental watering. Risks and mitigating actions are continually reassessed by program partners throughout the water year.

Engagement

Waterway managers meet communities on environmental watering regionally, although other program partners also play a role.

In each region of Victoria, community engagement on environmental watering happens when environmental watering objectives and priorities are scoped (long term and annually), when delivering environmental water, and when reporting on environmental watering results.

In the North Central region communities are involved in decisions about the Loddon and Campaspe river systems, Murray river system including Gunbower Forest and some of the wetlands connected by the Wimmera-Mallee pipeline. This happens through formal advisory groups: Environmental Water Advisory Groups including river and wetland focused groups and the Gunbower Island Community Reference Group.

Who is engaged and how

Recreational users

Through formal advisory groups, recreational users provide local advice and raise opportunities for potential 'shared benefits' from environmental watering. Through Environmental Water Advisory Groups, recreational users are informed of environmental water deliveries and provide data that assists with reporting on the outcomes of environmental watering.

Goulburn-Murray Water engages with recreational user groups (such as Save Lake Eppalock and Lake Meran Users Group) that use water storages for recreation through planned consultations and meetings to discuss storage levels and potential impacts of environmental water releases from storages.

Environment groups

Through formal advisory groups, environment groups provide local knowledge, land management advice and advocate for the environment. They are also informed of environmental water deliveries and provide data that assists with reporting on the outcomes of environmental watering (including citizen science monitoring data such as providing bird counts).

Landholders/farmers

Through formal advisory groups, farmers and landholders (including those who own private wetlands that receive environmental water) provide local knowledge and land management advice regarding environmental watering.

They are also informed of environmental water deliveries and provide data that assists with reporting on the outcomes of environmental watering. Goulburn-Murray Water engages (and often) with consumptive entitlement holders (often irrigators) and landholders (often with river frontages).

Traditional Owners

Through the North Central Catchment Management Authority Indigenous Facilitator, Traditional Owners from the Barapa Barapa, Dja Dja Wurrung and Yorta Yorta Nations are given the opportunity to provide input to seasonal watering proposals. The Catchment Management Authority and the Barapa Barapa Nation have conducted a cultural values mapping project in Gunbower Forest which will eventually enable cultural values to be incorporated in Gunbower environmental water planning. The Barapa Barapa and Yorta Yorta Nations undertake monitoring of cultural values in Gunbower Forest.

There are Dja Dja Wurrung and Yorta Yorta representatives from the North Central region who are members of the Murray Lower Darling Rivers Indigenous Nations. The Victorian Environmental Water Holder, the Commonwealth Environmental Water Holder and the Murray Darling Basin Authority engage the Murray Lower Darling Rivers Indigenous Nations on strategic (often longer term) issues related to environmental watering.

Councils

Councils are invited to participate in formal advisory groups meetings. Goulburn-Murray Water  consults with the City of Greater Bendigo, Gannawarra Shire and Swan Hill Rural City Council regularly on water management, including on environmental water management.

General public

The North Central Catchment Management Authority communicates and engages with the general public through their website, media releases, newsletters, public notices, community forums, community events (such as tours of Gunbower Forest during environmental watering), social media and direct contact to interested parties by email distribution list.