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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 Riv

Environmental water holder

System map

Grey river reaches have been included for context. The coloured extent of the upper Barwon River (including the East and West branches) is provided as a preliminary indication of where water may be able to be delivered if the entitlement is granted.

Environmental watering objectives in the Lower Barwon wetlands

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Provide suitable foraging habitat including mud flats and shallow water for wading birds, and refuge for waterbirds and shorebirds
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Provide 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 salinedependant ecological vegetation communities
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Maintain the high diversity of ecological vegetation communities in the wetlands Increase the growth and extent 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, which provide a home for many thousands of migratory birds from around the world.

The wetlands support about 47 threatened animal and plant species and communities. 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 communities.

Reedy Lake supports a range of vegetation communities including coastal saltmarsh, herbfields and reed beds. River regulation has changed Reedy Lake from a partly ephemeral system into a permanently wet lake that has largely remained in a constantly wet state since the 1970s. Permanent inundation has favoured the reed bed community in the lake and over time it has increased its extent and replaced much of the coastal saltmarsh and herbfield communities and open-water habitat. While reed beds form an important part of the lake's ecosystem, their continued expansion is reducing habitat diversity. In turn, this is reducing the number and diversity of internationally important migratory waterbirds the wetland supports. Unfortunately, the carp population had also steadily increased, diminishing the health of the lake. Carp prey on native fish and compete with them for habitat and food. They also damage aquatic vegetation.

In summer/autumn 2016–17, the Corangamite CMA implemented the first year of a three-year partial drying regime at Reedy Lake. This helped control carp numbers and improve conditions for communities of coastal saltmarsh and herbfields. Achieving a more-natural wetting and drying regime is the single most important management action to protect the long-term ecology of the lower Barwon wetlands.

Hospital Swamps is made up of five unique wetland basins that support a high diversity of ecological values and processes. Large areas of threatened coastal saltmarsh and diverse waterbird populations are present at the site. Vegetation communities in Hospital Swamps have remained largely unchanged over time due to the maintenance of natural wetting and drying cycles.

Social, cultural and economic values

The lower Barwon wetlands are located 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, birdwatching, game hunting and passive recreation. It is a culturally significant area for Aboriginal Victorians including those represented by the Wathaurung Aboriginal Corporation (Wadawurrung). The system also supports a commercial eel fishery.

Conditions mid-2017

Above-average rainfall in winter/spring 2016–17 delivered three overbank flows in the Barwon River, which resulted in higher-than-average water levels in the wetlands in spring. Water levels over summer dropped, due to reduced seasonal rainfall. Suitable summer conditions allowed for the implementation of a partial drying regime at Reedy Lake. Operational limitations at Hospital Swamps restricted full achievement of the regime, although the lowered water levels did achieve some ecological outcomes.

Despite the wet conditions at the start of the water year, the Corangamite CMA lowered water levels and partially dried Reedy Lake to 0.1 m AHD for the first time in more than a decade, starting a long-term process to restore the site's threatened ecological values. Achieving a more-natural wetting and drying regime is the single most important management activity to protect the ecology of the lower Barwon wetlands. The lower water level in summer 2016–17, in combination with the planned watering regime in future years, is expected to reduce the carp population, limit the growth of invasive tall reeds and increase the growth and extent of coastal saltmarsh, herbfields and lignum shrubland ecological vegetation communities.

A natural pattern of wetting and drying was partially implemented in Hospital Swamps, which meant inflows from the Barwon River entered the wetland in winter/ spring and were actively drawn down, reducing the water level over the drier summer months. While low water levels were achieved, a full drying cycle was not completed due to operational constraints. Low water levels helped to support important ecological processes. Future drying of the wetland is essential to maintain the balance between freshwater and saltwater processes, which is necessary to support the diverse mix of vegetation communities and provide feeding and breeding habitat for waterbirds and native fish.

Scope of environmental watering in 2017–18

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

The main objective for environmental watering in the lower Barwon wetlands is to implement natural wetting and drying cycles. The wetlands will be filled in winter and spring when water levels in the Barwon River are high and will be allowed to draw down over summer. These regimes will be managed by using existing regulators that can control flow in either direction between the Barwon River and the wetlands.

Hospital Swamps has had an appropriate wetting and drying regime for many years and there is no plan to change its management in 2017–18.

The plan for Reedy Lake will be to implement the second year of the partial drying regime. The lake will be allowed to fill in winter and spring and then draw down to a target level of 0.3 m AHD in summer to reduce the extent of reed beds and allow other vegetation communities to recolonise. Increasing the variety of vegetation communities and habitat structure over time is expected to improve conditions for internationally significant waterbird species.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
  • Stimulate fish breeding

Spring/early summer drawdown (October–January) and continued low water levels (around 0.3 m AHD) throughout summer/autumn (January–March/April)

The inlet to Reedy Lake will be closed to allow water levels to drop to about 0.3 m AHD through evaporation; during this period, the inlet and outlet may be manipulated if required to maximise the drawdown or to introduce saltwater to the lake

  • Reduce the extent 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
  • Promote suitable conditions for threatened vegetation communities (such as coastal saltmarsh, herbfields and lignum shrubland)
  • 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 increase 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
  • 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 the 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 if a summer storm increases water levels above 0.85 m AHD

  • Reduce the threat of carp and associated impacts on plants and animals
  • Prevent the expansion 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 increase soil salinisation
  • Initiate the 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.

Risk management

In preparing its seasonal watering proposal, Corangamite 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

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.