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Water for the environment can be used to manage water levels in Reedy Lake and Hospital Swamps, which connect to the Barwon River. The environmental entitlement for the lower Barwon wetlands does not provide access to water held in storage. Instead, it allows water to be diverted 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 the natural wetting of the wetlands.

Proportion of water entitlements in the Lower Barwon Wetlands held by private users, water corporations and environmental water holders on 30 June 2020

Traditional Owners
Environmental water holder

System map

Environmental watering objectives in the Lower Barwon wetlands

Fish icon
Provide habitat for fish breeding and growth and improved conditions for migration and dispersal when wetlands are connected to the Barwon River

Reduce carp populations
Soil icon
Provide habitat for fish breeding and growth and improved conditions for migration and dispersal when wetlands are connected to the Barwon River

Reduce carp populations
Plant icon
Increase the diversity of ecological vegetation communities in the wetlands and increase the recruitment of aquatic vegetation

Increase the growth and extent of coastal saltmarsh, herbfields and lignum shrubland ecological vegetation communities

Retard colonisation of tall reed in low-lying areas and increase open-water habitat

Provide varying water levels and conditions to promote soil salinisation and support the persistence and growth of threatened, salt-dependent ecological vegetation communities
Insect icon
Maintain and improve the waterbug population and its biomass
Water icon
Maintain nutrient cycling and improve lake productivity

Provide flushing inflows to remove accumulated salts

Maintain surface water and groundwater interactions

Improve soil health and enable the weathering of heavy metals in vegetation-covered fringing soils
bird icon
Provide suitable feeding and breeding habitat for waterbirds, including mudflats and shallow water for wading birds, flooded vegetation and wetland fringes

Maintain waterbird breeding events

Environmental values

Reedy Lake and Hospital Swamps form part of the internationally recognised Port Phillip Bay (Western Shoreline) and Bellarine Peninsula Ramsar site, which is used by many thousands of migratory birds from around the world. The wetlands support 47 known threatened plant and animal 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.

Reedy Lake was naturally a partly ephemeral system, but river regulation meant the lake was permanently wetted from the 1970s until 2016. This long-term wetting resulted in a decline in biodiversity. The full water levels reduced the extent and diversity of vegetation communities, including coastal saltmarsh, and reduced the availability of shallow wading habitat, which in turn has resulted in lower waterbird diversity.

Following a four-year (2016-17 to 2019-20) watering regime trial at Reedy Lake, the Lower Barwon Review in 2020 proposed to implement the long-term flow recommendations with a seasonally adaptive approach, avoiding complete dry-out years. At Reedy Lake, this means having the wetland full one out of four years and a partial drawdown in summer and autumn three out of four years. The review’s recommendations informed 2021-22 watering actions and future directions.

Hospital Swamps is made up of five wetland basins that support important ecological processes and significant ecological values, including large areas of threatened coastal saltmarsh and diverse waterbird communities. Vegetation communities in Hospital Swamps have remained largely unchanged over time due to the maintenance of natural wetting and drying cycles.

Traditional Owner cultural values and uses

Corangamite CMA worked with Wadawurrung Traditional Owners Aboriginal Corporation (WTOAC) during the development of plans to deliver water for the environment for the lower Barwon wetlands as part of an ongoing conversation to ensure Wadawurrung knowledge and culture is incorporated into decision-making and that watering requirements for culturally significant species are maintained.

The WTOAC is a member of the Lower Barwon Community Advisory Committee. It has reviewed how its aspirations and plans for Country have been represented in the planning process for the lower Barwon wetlands and has provided a letter of endorsement for Corangamite CMA’s 2022-23 seasonal watering proposal.

The WTOAC has identified cultural values which apply to all waterways within Wadawurrung Country. Values that have been identified in the lower Barwon wetlands include:

  • culturally significant wetland species such as Porronggitj (brolga), Toolim (black duck), Kunuwarra (black swan), Buniya (eel), Tark (common reed) and Bal-yan (bull rush)
  • recognition of wetlands as meeting, ceremony and trade places
  • maintaining water holes and refuge pools
  • maintaining access to culturally important story places and ceremonial places
  • protection of artefact sites
  • use of appropriate Wadawurrung language for places of cultural importance
  • increased opportunities for the Wadawurrung to be involved in monitoring and evaluation activities
  • including the Wadawurrung in all communication around releases of water for the environment and other wetland-related activities.

Social, recreational and economic values and uses

In planning the potential watering actions in Table 3.7.3, Corangamite CMA consulted widely with stakeholders to ensure it considered cultural, social, economic and recreational values relevant to water management in the lower Barwon wetlands. Opportunities for social, recreational and economic values and uses are incorporated into planning and watering decisions if they do not compromise environmental outcomes.

Expert advice (such as a flow ecology study and the 2020 Lower Barwon Review) emphasised that the entire recommended watering regime — providing a fill to the wetlands and allowing water levels to draw down at the right times — must be implemented to improve biodiversity and protect the long-term health of the wetlands, so it may not be possible to meet some community expectations at all times (such as keeping the wetlands permanently full).

However, Corangamite CMA plans to ensure management of water levels in the wetlands can meet ecological requirements and also support a range of values and uses where possible, including:

  • water-based recreation (such as boating, duck hunting and fishing)
  • wetlands recreation and amenity (such as birdwatching and spending time outdoors)
  • community events and tourism (such as community events and Traditional Owner events)
  • socioeconomic benefits (such as commercial fishing).

Corangamite CMA works with its community advisory group and stakeholders and seeks to balance these interests where possible, while maintaining the overall health of the wetlands to help sustain these activities into the future.

Recent conditions

Rainfall across the Barwon catchment during 2021-22 was slightly above the long-term average. The West Barwon Reservoir and Lal Lal Reservoir both spilled during the year, and these events, combined with natural inflows downstream of the storages, generated high flows in the lower Barwon River that inundated the lower Barwon wetlands several times in winter and spring.

Water for the environment in the lower Barwon wetlands was managed according to an average climate scenario throughout 2021-22. Both wetlands filled in winter and spring. Levels in Reedy Lake drew down slightly through evaporation and reduced inflows from Barwon River in December. Planned actions to actively draw down Reedy Lake during summer and autumn were timed to avoid disturbing nesting waterbirds, but the lake did not reach its target drawdown level due to wet conditions.

Hospital Swamps started drawing down through evaporation in December and reached its target drawdown level in March. The inlet from the Barwon River to Hospital Swamps was opened in May to start a wetland fill.

Scope of environmental watering

Table 3.7.3 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 3.7.3 Potential environmental watering actions, expected watering effects and associated environmental objectives for the lower Barwon wetlands

Potential environmental watering action

Expected watering effects

Environmental objectives

Reedy Lake

Autumn/winter/spring fill (April to November) and top-ups as required (year-round) (targeting 0.8 m AHD)

  • Maintain a mosaic of water depths and resources across the wetland to support waterbird breeding events
  • Inundate fringing wetland vegetation to provide foraging habitat for waterbirds
  • Maintain sufficient depth of water around wetland vegetation to provide fish breeding habitat
  • Temporarily inundate the outer edges of the wetland to initiate growth and recruitment of diverse vegetation communities while permanently inundating the inner wetland vegetation communities
  • Allow fish to move between the river, lake and estuary
  • Stimulate waterbug communities to breed for waterbird feeding
  • Dilute soil and surface water salts and initiate decomposition of organic matter
Fish iconPlant icon  Heron icon
Summer/autumn drawdown (December to May) (targeting 0.3 m AHD)
  • Lower the water level by natural evaporation and assisted drawdown (if required and as informed by waterbird monitoring) to dry out wetland fringing vegetation to reduce potential waterlogging of saltmarsh communities to support germination
  • Expose mudflats and margins to provide feeding habitat for wading/ migratory waterbirds and frogs
  • Manage reed colonisation of low-lying areas by allowing drying and saline groundwater intrusion to reduce growth
  • Support drying phase for vegetation communities that require drying to grow and recruit
  • Reduce water levels to restrict carp movement and access to habitat
  • Allow vegetation to decay and soils to oxidise and release nutrients to improve lake productivity and maintain biogeochemical processes
  • Enable surface water/groundwater interaction by allowing saline groundwater to discharge to the wetland bed

Fish iconPlant iconHeron icon

Hospital Swamps

Autumn/winter/spring fill (April to November) and top up as required (year- round) (targeting 0.5 m AHD)

  • Maintain a mosaic of water depths and resources across the wetland and inundate various vegetation communities and create nesting, breeding and feeding opportunities for waterbirds, fish and waterbugs
  • Increase water levels to trigger fish spawning and waterbird breeding; high water levels will allow fish to access the wetland from the river
  • Increase freshwater to dilute salt in the soil and surface water over winter
  • Inundate outer edges and margins to initiate growth and maintain the condition of important wetland vegetation communities

Fish iconPlant iconHeron iconInsect iconWater drop icon

Summer/autumn drawdown (December to May) (targeting 0.1-0.3 m AHD)

  • Lower the water level by natural evaporation and assisted drawdown (if required and as informed by waterbird monitoring if available) to dry out wetland fringing vegetation and expose mudflats and margins to support the feeding of wading/migratory waterbirds and frogs
  • Manage reed colonisation of low-lying areas by allowing drying and saline groundwater intrusion to reduce growth
  • Support drying phase for vegetation communities that require drying to grow and recruit
  • Reduce water levels to restrict carp movement and access to habitat
  • Allow vegetation to decay and soils to oxidise and release nutrients to improve lake productivity and maintain biogeochemical processes
  • Enable surface water/groundwater interaction by allowing saline groundwater to discharge to the wetland bed

Fish iconPlant iconHeron icon

Scenario planning

Table 3.7.4 outlines potential environmental watering and expected water use under a range of planning scenarios.

An independent review of the lower Barwon wetlands watering trial from 2016-17 to 2019-20 was completed in 2020. The review confirmed that the current wetting and drying regimes for Reedy Lake and Hospital Swamps are appropriate, but it recommended that the timing of planned drawdowns should be adaptively managed to avoid disturbing any significant waterbird breeding at either site. The wetlands may be topped up when required after the fill period while awaiting expert advice to commence drawing down.

The 2012 FLOWS study for the lower Barwon wetlands and the 2020 Lower Barwon Review recommend a four-year watering cycle for Reedy Lake: fill the wetland in autumn/winter/spring every year and having low water levels during summer in three out of four years to facilitate partial drying. For the last three years, Reedy Lake has not achieved a full drawdown, and it is a priority for 2022-23 under all scenarios to achieve it. Drawdowns at Reedy Lake and Hospital Swamps support waterbird and frog breeding and provide muddy margins for migratory shorebirds that actively forage in mudflats during summer and early autumn before returning to the Northern Hemisphere. The planned summer/autumn drawdown will be delayed if there is significant waterbird breeding. The planned wetland drying may be difficult to implement under a wet climate scenario, especially if there are multiple high-flow events in the Barwon River during summer and autumn.

Planning scenario table

Table 3.7.4 Potential environmental watering for the lower Barwon wetlands under a range of planning scenarios

Planning scenario

Drought-Dry

Average

Wet

Expected river conditions

  • Limited to no flow from the Barwon River in winter/spring
  • Disconnection between wetlands and the Barwon River for a long period
  • Natural drawdown may begin earlier than planned
  • Some natural inflow from the Barwon River in winter/spring
  • More gradual lowering of water levels during drawdown
  • Overbank flow from the Barwon River is likely to fill the wetlands
  • Stormwater inflow and local rain/run-off will provide regular top-ups
  • Extensive drying of the wetland is unlikely

Reedy Lake

Potential environmental watering

  • Reedy Lake fill and top- up (as required)
  • Reedy Lake drawdown
  • Hospital Swamps fill and top-up (as required)
  • Hospital Swamps drawdown
  • Reedy Lake fill and top- up (as required)
  • Reedy Lake drawdown
  • Hospital Swamps fill and top-up (as required)
  • Hospital Swamps drawdown
  • Reedy Lake fill and top- up (as required)
  • Reedy Lake drawdown
  • Hospital Swamps fill and top-up (as required)
  • Hospital Swamps drawdown

Hospital Swamps

Potential environmental watering

  • Hospital Swamps fill and top-up (as required)
  • Hospital Swamps drawdown
  • Hospital Swamps fill and top-up (as required)
  • Hospital Swamps drawdown
  • Hospital Swamps fill and top-up (as required)
  • Hospital Swamps drawdown

Engagement

Table 2 shows the partners, stakeholder organisations and individuals with which Corangamite CMA engaged when preparing the lower Barwon wetlands 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 Corangamite Regional Catchment Strategy and the Corangamite Waterway Strategy.

Over the last six years, the Corangamite CMA has consulted extensively about the planned watering regimes for Reedy Lake and Hospital Swamps with diverse stakeholders and interest groups representing over 1,500 people. These people have been involved in developing the original environmental flows study and in subsequent scientific work about ecological risks, vegetation monitoring, alternative management approaches and infrastructure operations. The results of this 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 in future.

Table 2 Partners and stakeholders engaged in developing the lower Barwon wetlands seasonal watering proposal

Partner and stakeholder engagement
  • Community members on the Lower Barwon Community Advisory Committee
  • Members of the Lower Barwon Review Project Advisory Group
  • Environment Victoria
  • Geelong Environment Council
  • Geelong Field Naturalists Club
  • Barwon Water
  • Department of Environment, Land, Water and Planning
  • Parks Victoria
  • Southern Rural Water
  • Greater Geelong City Council
  • Victorian Fisheries Authority
  • Landholders
  • Farmers
  • Commercial eel fishers
  • Geelong Field and Game
  • Geelong Gun and Rod Association
  • VR Fish
  • Lower Barwon Review 2020 Expert Review Panel
  • Wathaurung Aboriginal Corporation

Page last updated: 01/07/22