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The estuarine reach of the Barwon River contains a system of wetlands and lakes including Lake Connewarre, Reedy Lake, Hospital Swamps, Salt Swamp and Murtnaghurt Lagoon. Environmental water can be actively managed at Reedy Lake and Hospital Swamps using regulating structures at the wetlands.

Unlike many other systems, the environmental entitlement does not provide access to water held in storage. Instead, it allows water to be diverted via regulators from the Barwon River into Reedy Lake and Hospital Swamps when river levels are above 0.7 m AHD (Australian Height Datum). High water levels in the Barwon River can also result in natural inundation of the wetlands.

Environmental water holder

System map

Lower Barwon & Moorabool Systems
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 Lower Barwon wetlands

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Provide suitable habitat including mud flats and shallow water for wading birds, and feeding opportunities and refuge for waterbirds and shorebirds
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Promote habitat for fish breeding and growth and improved conditions for migration and dispersal when wetlands are connected to the Barwon River
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Provide varying water levels and conditions to promote soil salinisation to support the persistence and growth of threatened saline-dependant ecological vegetation communities
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Maintain the high diversity of ecological vegetation communities in the wetlands
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Promote the growth of coastal saltmarsh, herbfields and lignum shrubland ecological vegetation communities

Environmental values

Reedy Lake and Hospital Swamps form part of the internationally recognised Port Phillip Bay (Western Shoreline) and Bellarine Peninsula Ramsar site and provide a home for thousands of migratory birds from around the world.

The wetlands support about 47 threatened animals and plants. These include some of Victoria's rarest species (such as the brolga, orange-bellied parrot, Australasian bittern, growling grass frog, Australian grayling and dwarf galaxias) and subtropical and temperate coastal saltmarsh.

Reedy Lake supports a range of plants including coastal saltmarsh, herbfields and reed beds, which provide important habitat for a variety of animal species. The relative extent of these plants is changing due to the absence of suitable wetting and drying cycles. Reed beds are continuing to expand, reducing freshwater habitat and the diversity of birds, fish and other animals the system supports.

Hospital Swamps is made up of five unique wetland basins that support a diversity of ecological values and processes. Large areas of threatened coastal saltmarsh and diverse fish and waterbird populations are present at the site. Plants in Hospital Swamps have remained largely unchanged over time due to the maintenance of natural wetting and drying cycles, which has protected the important environmental values of the wetlands.

Social and economic values

The lower Barwon wetlands are close to Geelong, the second biggest city in Victoria. They form a very important part of the region's social fabric. The wetlands are valued by many people for their intrinsic beauty, ecological significance and recreational uses. In particular, the wetlands are used heavily by Geelong Field and Game and Geelong Field Naturalists for conservation activities and events, bird watching, game hunting and passive recreation. The system also supports a commercial eel fishery and is of significance to Traditional Owners and their Nations in the area.

Conditions mid-2016

Dry conditions in the Barwon River catchment resulted in lower river flows than normal in 2015–16, meaning that the water levels in Reedy Lake and Hospital Swamps were lower than in previous years, as less water could be diverted into the wetlands.

As in previous years, a natural pattern of wetting and drying was implemented in Hospital Swamps which meant inflows from the Barwon River entered the wetland in the winter/spring period and were actively drawn down (reducing the water level) over the drier summer months. This drying cycle helped to support important ecological processes: drying of the wetland is essential for maintaining the balance between fresh and salt water processes, which is necessary to support the diverse mix of plants and provide feeding and breeding habitat for waterbirds and native fish.

Water was delivered to Reedy Lake whenever the levels in the Barwon River were above 0.7 m Australian Height Datum (AHD). As the river level dropped below 0.7 m AHD quite regularly over summer 2015–16, water levels in Reedy Lake naturally fell to about half-full. Heavy rain in January 2016 resulted in high water levels in the Barwon River, increasing inflows to Reedy Lake, with water levels fluctuating in response to natural conditions.

Reedy Lake has largely remained in a constantly wet state since the 1970s. This has altered the soil and water chemistry allowing the extent of tall reed communities to nearly double. While reed beds form an important part of the lake's ecosystem, their continued expansion is reducing habitat diversity as they have taken over areas that previously supported different vegetation types and open water.

In turn, this is reducing the number and diversity of internationally important migratory waterbirds the wetland supports. Unfortunately the carp population has also steadily increased and is now at a level where carp are diminishing the health of the lake. Carp prey on native fish and compete with them for habitat and food. They also damage aquatic vegetation.

Scope of environmental watering in 2016–17

Potential environmental watering actions and associated environmental objectives are provided in Table 1.

A more natural cycle of varying water levels is planned for both Hospital Swamps and Reedy Lake in 2016–17. The cycle will include delivering water in winter/spring and then lowering water levels over summer until the Barwon River level increases in autumn.

At Reedy Lake, introducing a more natural cycle of varying water levels will improve conditions to foster the growth of threatened plants while also managing the expansion of tall reeds which are seriously reducing habitat. This cycle will also support internationally significant bird species and most lake users. Temporarily lowering water levels at Reedy Lake will affect some users, including a local eel fisher. However, continuing to maintain high water levels in the lake poses a significant long-term risk to the health of the internationally important wetland, including the 47 threatened plants and animals the lake supports.

If a more natural cycle of varying water levels is not initiated, the spread of reed beds could ultimately prevent recreational and commercial user access, and reduce populations of waterbirds and fish. This will lessen the fishing, hunting and birdwatching opportunities now available. With lower water levels there will also be the opportunity to control carp numbers, which will further benefit the user groups at Reedy Lake, improve native fish populations and reduce the damage that carp are causing to aquatic plants, ultimately benefiting bird populations as well.

Lowering water levels at Reedy Lake is the single most important management action to mitigate threats to the system and ensure all user groups can continue to value and use the lake into the future.

The Corangamite Catchment Management Authority has undertaken extensive consultation about the planned watering regimes for Reedy Lake and Hospital Swamps over the last six years with a broad range of stakeholders and interest groups representing over 1,500 people. These people have been involved in developing the environmental flow study and in additional scientific work exploring ecological risks, vegetation monitoring, alternative management approaches and infrastructure operations. The results from this comprehensive work show that lowering water levels at Reedy Lake is the only feasible management practice that will mitigate threats to the ecological health of the wetland and ensure all user groups can continue to use the system into the future.

No alternative water regime or management approaches could be identified that would enable the environmental health of the wetland to be protected while at the same time mitigating impacts to eel fishing. Corangamite Catchment Management Authority is continuing to work with state water and fisheries managers and the eel fisherman to explore alternative arrangements for eel fishing in the region.

Table 1 Potential environmental watering actions and objectives for the lower Barwon wetlands

Potential environmental watering

Environmental objectives

Reedy Lake

Autumn/winter/spring filling flows (in March/April–October) 1

The inlet to Reedy Lake will be opened in autumn in response to a sustained increase in flows in the Barwon River

  • Maintain connectivity with the Barwon River
  • Provide feeding habitat for waterbirds in flooded vegetation and the wetland fringe
  • Promote fish reproduction

Spring/early summer drawdown (in October–January) and continued low water levels throughout summer/autumn (January–March/April)

The inlet to Reedy Lake will be closed to allow water levels to drop through evaporation; during this period, the outlet may be manipulated if required to maximise the drawdown or to introduce saltwater to the lake

  • Reduce the threat of tall reeds in the system by increasing the salt content of the water and soil
  • Reduce the threat of carp and associated impacts on plants and animals
  • Provide increased habitat diversity (including salt pans, mudflats and shallow water)
  • Provide wading bird habitat in summer
  • Provide summer waterbird refuge and foraging habitat
  • Improve lake shore salinity and promote soil salinisation
  • Initiate decomposition of organic matter on the wetland bed, to increase lake productivity when it is refilled
  • Improve soil health and allow weathering of heavy metals in lake fringe soils
  • Promote suitable conditions for threatened vegetation communities (such as coastal saltmarsh, herbfields and lignum shrubland)
  • Allow seasonal recruitment of aquatic macrophytes at wetland fringes

Hospital Swamps

Autumn/winter filling flows (in May–November) 1

Hospital Swamps will be connected to the Barwon River for at least 6 weeks by keeping the inlet and outlet open

  • Create habitat and support waterbug populations
  • Stimulate fish and waterbird breeding
  • Allow fish to colonise the wetland from the river
  • Allow soil and surface water salts to be diluted over winter
  • Promote and sustain growth of important wetland vegetation communities

Summer/autumn drawdown (in December–March/April)

The inlet to Hospital Swamps will be closed to allow water levels to drop through evaporation; during this period, the outlet will be opened for short periods of time if a summer storm increases water levels above 0.85 m AHD

  • Reduce the threat of carp and associated impacts on plants and animals
  • Reduce the threat of tall reeds in the system by increasing the salt content of the water and soil
  • Provide increased habitat diversity (including salt pans, mudflats and shallow water)
  • Provide wading bird habitat in early summer
  • Provide early summer waterbird refuge and foraging habitat
  • Improve lake shore salinity and promote soil salinisation
  • Initiate decomposition of organic matter on the wetland bed, to increase lake productivity when it is refilled
  • Improve soil health and allow weathering of heavy metals in lake fringe soils
  • Promote suitable conditions for threatened vegetation communities (such as coastal saltmarsh, herbfields and lignum shrubland)
  • Allow seasonal recruitment of aquatic macrophytes at wetland fringes

1 Water can only be diverted into the lower Barwon wetlands when water levels in the Barwon River are above 0.7 m AHD at the lower Barrage Gauging Station, in line with provisions for accessing water under the environmental entitlement.

Scenario planning

Inundation of the wetlands over the winter period and drawdown in summer are a priority under all scenarios but the extent of the wetting and drying will vary in response to natural conditions. For example, in a wet scenario it is unlikely that a substantial drawdown in Reedy Lake or Hospital Swamps will be achievable. However, some degree of drying is still important to promote vegetation diversity and soil salinisation and to provide a variety of feeding and breeding habitat for waterbirds. The wetlands will be managed adaptively throughout the year in response to climatic conditions to maximise environmental outcomes.

The planned action will be carefully managed throughout the drawdown by the Corangamite Catchment Management Authority, with monitoring to ensure that the drawdown can be adaptively managed as needed.

Table 2 Potential environmental watering for the lower Barwon wetlands under a range of planning scenarios

Planning scenario

Dry

Average

Wet

Expected catchment conditions

  • Some natural inflows from the Barwon River in winter/spring
  • Dry conditions over summer will assist in the drawdown of the wetlands
  • Some natural inflows from the Barwon River in winter/spring
  • Mild conditions over summer may assist in facilitating some drawdown of the wetland water levels
  • Overbank flows likely to inundate the wetlands as a result of higher river flows, stormwater inflows and local rain/run-off
  • Extensive drawdown of wetlands is unlikely

Reedy Lake

Potential environmental watering

  • Autumn/winter/spring filling flows (March/April–October)
  • Spring/early summer/autumn drawdown and low water levels (October–March/April)

Hospital Swamps

Potential environmental watering

  • Autumn/winter/spring filling flows (May–November)
  • Summer/autumn drawdown (December–March/April)

Risk management

In preparing its seasonal watering proposal, Corangamite 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 Corangamite region communities are involved in decisions about the Moorabool river and Lower Barwon wetlands. This happens through formal advisory groups including a Moorabool stakeholder advisory and the Lower Barwon community advisory committees.

Who is engaged and how

Recreational users

Through formal advisory groups, recreational user representatives (Field & Game Australia; Geelong Gun and Rod Association; VRFish) provide advice and communicate their priorities. They are informed of environmental water deliveries and provide data that assists with reporting the outcomes of environmental watering.

Field & Game Australia (Geelong branch) has been a key advocate for environmental watering, providing assistance in monitoring activities and on-ground works.

Environment groups

Through formal advisory groups, environmental groups (People for a Living Moorabool; Geelong Environment Council; Geelong Landcare Network; Environment Victoria; Geelong Field Naturalists) provide local knowledge and advocate for the environment - specifically on seasonal watering proposals and longer term Environmental Water Management Plans. Environmental groups also receive email updates during environmental water delivery.

Landholders/farmers

Through formal advisory groups, landholders (specifically those who own land with river frontage, and commercial eel fishers in the lower Barwon wetlands) provide local knowledge and 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.

Traditional Owners

Traditional Owners are invited to participate in engagement activities regarding the Moorabool River and the Lower Barwon wetlands.

Councils

The City of Greater Geelong and Moorabool Shire have been invited to join formal advisory groups.

General public

The Corangamite Catchment Management Authority website and media releases on environmental watering are the main mechanisms for communications and engagement with the general public on environmental watering.

The Catchment Management Authority engages with the general public on environmental watering via their website and media releases.