Lower Latrobe wetlands

The lower Latrobe wetlands (Dowd Morass, Heart Morass and Sale Common) are an important component of the internationally recognised Gippsland Lakes Ramsar site and provide habitat for a variety of waterbirds of state, national and international conservation significance. The wetlands are located on the floodplain of Durt-Yowan (Latrobe River) between its confluence with Carran Carran (Thomson River), and they form part of the Gippsland Lakes system.

River regulation and water extraction from Durt-Yowan (Latrobe River), Carran Carran (Thomson River) and Wirn wirndook Yeerung (Macalister River) have reduced the frequency of small- and medium-sized floods that naturally wet the lower Latrobe wetlands. Construction of levees and drains and the filling of natural depressions have also altered water movement into and through the wetlands. The drainage and flooding regime in all three wetlands is now managed to some extent with regulators connected to Durt-Yowan (Latrobe River).

System map

Latrobe River and Wetland System — 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 Latrobe wetlands

Maintain the abundance of frog populations

Maintain the abundance of freshwater turtle populations

Maintain or restore a variety of self-sustaining submerged and emergent aquatic vegetation types

Maintain or restore the diversity, condition and/or extent of native streamside vegetation fringing wetlands

Discourage the introduction and spread, or reduce the extent and density of undesirable/ invasive plants (Sale Common)

Maintain or enhance waterbird breeding, recruitment, foraging and sheltering opportunities

Provide suitable physio-chemical conditions to support aquatic life

Avoid catastrophic water quality conditions (such as acid sulfate soil exposure) (Heart Morass)

Environmental values

Sale Common is one of only two remaining freshwater wetlands in the Gippsland Lakes system. It provides sheltered feeding, breeding and resting habitat for a large range of waterbirds, including the Australasian bittern.

Dowd Morass is a large, brackish wetland that regularly supports rookeries of colonial nesting waterbirds, including Australian white ibis, straw-necked ibis, little black and little pied cormorants, royal spoonbills and great egrets.

Heart Morass is also a large brackish wetland, with open expanses providing shallow feeding habitat for waterbirds including black swans, Eurasian coots and a variety of ducks, including the musk duck.

Together, the lower Latrobe wetlands function as a diverse and complementary ecological system. Colonial nesting waterbirds breed among swamp paperbark trees at Dowd Morass in spring. Migratory shorebirds feed on the mudflats that are exposed as the wetlands draw down and dry over summer. Waterfowl and fish-eating birds use open-water habitat at the wetlands year- round. The wetlands also support threatened vegetation communities, including swamp scrub, brackish herbland and aquatic herbland.

Recent conditions

The Latrobe catchment experienced above-average temperatures throughout most of 2021-22 and above-average rainfall during early winter and throughout spring (in particular during November) 2021 for a second consecutive year. Significant flooding occurred in June 2021 and was followed by several smaller floods in late winter and spring. These floods, as well as other high-flow events in the Latrobe, Macalister and Thomson rivers, flushed the lower Latrobe wetlands for the first time since 2010-11, and salinity in Lake Wellington was at its lowest since 2004.

Environmental flows at the lower Latrobe wetlands were managed in line with a wet climate scenario in 2021-22. All planned watering actions were fully achieved with a combination of natural overbank flows and managed deliveries of water for the environment through inlet-regulating structures. It was the second consecutive year that all planned watering actions had been met, following relatively dry conditions in 2018-19 and 2019-20.

Routine monitoring at the wetlands detected improved water quality and vegetation condition at all sites as well as extensive growth of water-dependant eel grass, and there was evidence of successful breeding of green and golden bell frogs at Heart Morass. According to one anecdotal report, the level of frog breeding at Heart Morass was the highest in 30 years. More than 300 colonial waterbird nests, including royal spoonbills, little black cormorants, pied cormorants and Australian darter, were observed at Dowd Morass, making it the largest breeding event since the 2010-11 floods. Delivery of water for the environment in 2022-23 aims to build on the achievements of 2020-21 and 2021-22 and continue to enhance high-priority environmental values and support key ecohydrological functions.

Traditional Owner cultural values and uses

The Lower Latrobe wetlands are a place of spiritual and cultural connection for the Gunaikurnai people. Over many thousands of years, customs and lore have been passed orally between generations about the cultural values and uses of the wetlands and their importance to all Gunaikurnai people. The wetlands are on the lands of the Brayakaulung clan of the Gunaikurnai.

For the Gunaikurnai, the overarching objective for the wetlands is to provide and maintain healthy Country. Healthy Country includes the importance of place and the health of the entire ecosystem, including maintaining water quality, controlling pest species and maintaining a natural, seasonal flow regime and overbank flood events.

Environmental objectives for the delivery of water for the environment for the lower Latrobe wetlands should take a cultural landscape approach.

Watering requirements to support cultural values and uses include:

timing the delivery of water for the environment planned in partnership with the Gunaikurnai Land and Waters Corporation (GLaWAC) to support a seasonal flow regime and wet and dry periods that embody healthy Country
maintaining freshwater supply to the Latrobe River estuary, Dowd Morass, Sale Common and Heart Morass and associated freshwater habitats
providing connectivity between reaches and onto floodplains and maintaining water quality to support cultural values and uses of significance to the Gunaikurnai.

The wetlands support many keystone species important to the Gunaikurnai, and boran (pelican) and tuk (musk duck) are the mother and father in the Gunaikurnai creation story. If boran and tuk are living and breeding at the wetlands, it is a sign Country is healthy. If they are not, flows should be provided to promote required habitat and ecosystem services.

Other birds are important for woorngan (hunting) and food, including nalbong (water hens), gidai (black swans), boyangs (eggs) and koortgan (ducks except for tuk). Gidai require submerged and softer emergent vegetation to make nest mounds, placing them on a small island or floating them in deeper water. Gidai breed in late winter to early spring after the water level rises. Actions that fill the large wetlands and support the growth of loombrak (water ribbon) and submerged aquatic plants will support gidai. Ensuring that the lower wetlands and floodplain depressions (for example, billabongs) receive freshwater flows in winter/spring will provide the conditions for submerged and emergent aquatic plants to grow and provide food and nesting materials for the waterbirds.

GLaWAC is developing a vision for the wetlands that aligns with GLaWAC’s Gunaikurnai Whole-of-Country Plan. Key aspects of the vision include:

healthy Country: reflecting the spiritual and cultural values of the Gunaikurnai custodians; healthy Country contributes to the well-being of the Gunaikurnai
water access: access to water is crucial for many cultural values, including identity and relational values, future economic values and place values, among many others. Access to water, through ownership or management, means water made available to the Gunaikurnai on the Latrobe system and the Thomson system that provides freshwater to the wetlands. Every effort should be made to maintain freshwater-dependent values, which in turn deliver cultural values
cultural and economic use: returning to cultural practices and Gunaikurnai-informed management at the lower Latrobe wetlands is key to returning to a more freshwater habitat for cultural uses and cultural species. It will also provide for water- based tourism, cultural education and ecotourism (camping) experiences
connection: GLaWAC takes its responsibility very seriously to work closely with the people it represents on management decisions concerning Country and the health of Country. Gunaikurnai cultural obligations reflect Gunaikurnai views on healthy Country and, in turn, help the Gunaikurnai continue their ongoing connection to the land and waters of Country
climate change: the Gunaikurnai have cared for Country for thousands upon thousands of years, through many cycles of climatic change, and they understand how to manage the landscape as it too changes. When cared for using traditional knowledge, Country can be healed. Mitigation of climate change factors affecting the lakes, rivers and other waterways of the lower Latrobe wetlands can be effective with resources and empowerment provided to the Gunaikurnai.

Increasing the involvement of Traditional Owners in environmental water planning and management and ultimately providing opportunities to progress towards self-determination within and beyond the environmental watering program is a core commitment of the VEWH and its agency partners. This is reinforced by a range of legislative and policy commitments, including the Water Act 1989, the Victorian Aboriginal Affairs Framework, Water for Victoria (2016) and in some cases, agreements under the Traditional Owner Settlement Act 2010.

Where Traditional Owners are more deeply involved in the planning and/or delivery of environmental flows for a particular site, their contribution is acknowledged in Table 3.2.1 with an icon. The use of this icon is not intended to indicate that these activities are meeting all the needs of Traditional Owners but is incorporated in the spirit of valuing their contribution and indicating progress towards deeper involvement.

Watering planned and/or delivered in partnership with Traditional Owners to support cultural values and uses

GLaWAC and West Gippsland CMA are exploring opportunities to enhance environmental flows with Gunaikurnai outcomes in the lower Latrobe wetlands. In 2022-23, this is planned to include a jointly managed Gunaikurnai event to deliver water for the environment in Dowd Morass.

Social, recreational and economic values and uses

In planning the potential watering actions in Table 2.2.3, West Gippsland CMA considered how environmental flows could support values and uses, including:

water-based recreation (such as canoeing and fishing)
riverside recreation and amenity (such as birdwatching, camping and duck hunting)
socioeconomic benefits (such as commercial eel and carp fishing).

Scope of environmental watering

Table 2.2.3 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 2.2.3 Potential environmental watering actions, expected watering effects and associated environmental objectives for the lower Latrobe wetlands

Potential environmental watering action	EXPECTED WATERING EFFECTS	Environmental objectives
Sale Common
Top-up (anytime, following bird breeding event if required)	Prolong wetting of reed beds to maintain habitat and food resources for nesting waterbirds and protect chicks from predators
Partial fill (in July to August1 with top-ups as required to maintain water depth of at least 0.3 m AHD and surface coverage year-round)	Encourage the growth and flowering of semi-aquatic plants Provide appropriate wetland habitat for frogs and turtles Provide conditions that support waterbug communities and food resources for waterbirds
Fill (with top-ups as required during August to November, to maintain water depth of 0.4 to 0.5 m AHD for two months)	Wet the outer boundaries of the wetland to support the growth and flowering of streamside and fringing wetland plants, increasing foraging opportunities for waterbirds Encourage bird and turtle breeding by providing nesting habitat Provide connectivity between the river and wetlands and increase habitat and feeding opportunities for frogs and turtles
Trigger-based fill or top- up to 0.5 m AHD (during December to January, if required to drown out invasive vegetation)	Wet key habitats within the wetland for a sufficient duration to discourage invasive plants, particularly the excessive spread of giant rush
Partial drawdown (during December to March)	Oxygenate sediments to enable aquatic vegetation germination and recruitment Provide water level fluctuations for emergent vegetation reproduction and expansion (particularly swamp scrub and tall marsh) Break down organic matter and promote nutrient cycling Expose mudflats and create shallows to facilitate waterbird foraging
Dowd Morass
Top-up (any time, following bird breeding event if required)	Prolong wetting of reed beds to maintain habitat and food resources for waterbirds and protect chicks from predators, following an observed breeding event
Fill to control salinity (anytime)	Dilute salt concentrations within the wetland that may be caused by king tides from Lake Wellington (likely occurring between March to May) or other sources This watering action is likely to be triggered1 if electrical conductivity is rising and reaches 7,000 μS/cm
Partial fill (with top-ups as required to maintain surface coverage during July to December 2022 and April to June 2023²)	Provide seasonal variation in water depth throughout the wetland to support the growth and flowering of semi-aquatic plants Wet vegetation and soils at middle elevations within the wetland to increase the abundance of waterbugs and other food resources for frogs, turtles and waterbirds Provide connectivity between the river and wetlands and between wetlands, increasing available habitat for frogs and turtles Support bird breeding (when delivered in spring/early summer following earlier fill) by maintaining wetted habitat around reed beds
Fill (with top-ups as required to maintain water depth of 0.6 m AHD during August to November)	Wet reed beds and deep water next to reedbeds to provide waterbird nesting habitat and stimulate bird breeding Wet high-elevation banks and the streamside zone to support vegetation growth, creating nesting habitat for waterbirds Wet vegetation and soils at higher elevations to stimulate ecosystem productivity and increase the abundance of waterbugs and other food resources for frogs, turtles and waterbirds Provide connectivity between the river and wetlands and between wetlands, increasing available habitat and food resources for frogs and turtles Reduce the impact of saltwater incursion from Lake Wellington
Partial drawdown (during January to March)	Oxygenate sediments to enable aquatic vegetation germination and recruitment Provide water level fluctuations for emergent vegetation reproduction and expansion (particularly swamp scrub and tall marsh) Break down organic matter and promote nutrient cycling Expose mudflats and create shallows to facilitate waterbird foraging
Heart Morass
Top-up to permanently maintain water level above -0.3 m AHD (anytime)	Minimise the risk of acid sulfate soils developing by keeping known high- risk areas wet Respond to decreasing pH from the rewetting of exposed acid sulfate soils (most likely during high-wind events) Dilute salt concentrations within the wetland that may be caused by king tides from Lake Wellington or other sources. This watering action is likely to be triggered³ if wetland overtopping appears likely; based on rising water levels at Lake Wellington (reaching or exceeding +0.5m AHD)
Top-up (anytime, following bird breeding event if required)	Prolong wetting of reed beds to maintain habitat and food resources for waterbirds and protect chicks from predators, following an observed breeding event
Fill and partial flushing flow (during July to November⁴)	Wet high-elevation banks and streamside zone to support vegetation growth, creating nesting and foraging habitat for waterbirds, and provide food resources for terrestrial birds Provide connectivity between the river and wetlands and between wetlands, increasing available habitat and providing food resources for frogs and turtles Export accumulated salts and sulfates and allow the import and export of nutrients, dissolved organic carbon and seed dispersal between Durt- Yowan (Latrobe River) and Heart Morass
Partial fill (with top-ups as required to maintain a minimum water depth of 0.3 m AHD during August to December1)	Support the growth and flowering of semi-aquatic plants Provide appropriate wetland fringing habitat for frogs and turtles Provide conditions that support waterbug communities and food resources for frogs, turtles and waterbirds
Partial drawdown (during January to March)	Oxygenate sediments to enable aquatic vegetation germination and recruitment Provide water level fluctuations for emergent vegetation reproduction and expansion (particularly swamp scrub and tall marsh) Break down organic matter and promote nutrient cycling Expose mudflats and create shallows to facilitate waterbird foraging

¹ If salinity level in the Latrobe River exceeds 15,000 μS/cm, a fill will not be provided.

²This is the likely timing under a drought scenario. Note, under a dry, average or wet scenario a fill event may occur during this period, as detailed in Table 2.2.4.

³If the salinity level in the Latrobe River exceeds 10,000 μS/cm, a top-up will not be provided.

⁴If a partial flushing flow is not possible until the end of November, top-ups will be provided to maintain a fill with a minimum water depth of 0.5m AHD.

Scenario planning

Table 2.2.4 outlines potential environmental watering and expected water use under a range of planning scenarios.

The main priority for environmental flows at the lower Latrobe wetlands in 2022-23 will be to fill each wetland as much as possible in winter/spring and prevent complete drying over summer and autumn. The proposed watering actions aim to consolidate environmental outcomes from 2020-21 and 2021-22 to further enhance recovery from extended drying in 2018-19 and 2019-20 and build ecosystem resilience ahead of future dry periods. The wetlands can only be filled when water levels and water quality in the lower reaches of Durt-Yowan (Latrobe River) are suitable, and therefore the timing and extent of water delivery will be heavily influenced by natural climatic conditions and flow in Durt-Yowan (Latrobe River). It is likely that only partial fills will be possible under a drought scenario, and natural overbank floods are likely at any time of year under a wet scenario. Trigger-based inflows to address a potential acid sulfate soil risk, support a natural waterbird breeding event or control invasive vegetation will be delivered when needed and possible, even if the timing of these actions compromises other planned wetting or partial drawdown events. Specific watering plans for each wetland under different climate scenarios are described below.

Sale Common

The minimum aim for Sale Common is to partially fill the wetland in winter and provide top-ups as needed to maintain water levels above 0.3 m AHD throughout the year, which will wet about half of Sale Common. Maintaining at least a partial fill is considered ecologically important to support wetland plant communities (which experienced near-complete drying in 2018-19 and 2019-20) and provide habitat for frogs, turtles and waterbirds. This is likely to be the maximum water level achieved under a drought scenario.

Providing a fill to the wetland for at least two months from late winter or early spring is a high priority where possible to connect the wetland to Durt-Yowan (Latrobe River), stimulate recruitment of plant communities at the outer margins of the wetland and provide nesting habitat for breeding waterbirds. This is likely to be achieved under average and wet scenarios, and it may be achieved under a dry scenario if there is sufficient flow and water quality in Durt-Yowan (Latrobe River) at the required time.

The wetland will be allowed to draw down naturally over the warmer months, although there may be limited drawdown under average and wet climate scenarios. Facilitated drawdown (via opening regulator gates) is not proposed in 2022-23 unless it is deemed necessary, such as to control the excess proliferation of carp. If climatic conditions only allow a limited drawdown in 2022-23, the wetland may be actively drawn down in 2023-24 to facilitate nutrient cycling and other dry-phase ecosystem processes.

Dowd Morass

The plan at Dowd Morass is to fill or partly fill the wetland in winter and spring, then allow a controlled partial drawdown in summer. Top-ups would be provided as needed to support waterbird breeding and from April to June 2022 to prevent water levels from dropping below 0.3 m AHD and so increase available habitat for frogs and turtles by maintaining connectivity between the river and wetlands. A partial fill will support some vegetation outcomes and help maintain habitat and food for waterbirds, frogs and turtles. Achieving a complete fill at Dowd Morass is a lower priority in 2022-23, but it may occur naturally via overbank flows from Durt-Yowan (Latrobe River) in an average and wet climate scenario. A partial drawdown is planned in summer and autumn under drought and dry scenarios to support a wider range of wetland vegetation communities and facilitate carbon and nutrient cycles, but it may be limited under average and wet scenarios if there is significant local rainfall or high flows in Durt-Yowan (Latrobe River).

Heart Morass

Acidity and salinisation represent a high risk to environmental values at Heart Morass, and maintaining water levels above -0.3 m AHD at all times is a high priority to avoid exposing potential acid sulfate soils. Heart Morass was fully flushed in 2021- 22, which removed accumulated salt and sulphides and reduced the immediate risk of acid sulfate soils. Flushing flows are likely to occur again in 2022-23 under wet and possibly average climate scenarios, but they will not be delivered without a natural flood. The preferred watering strategy under drought and dry scenarios involves providing a partial fill to the wetland from winter to early summer and maintaining water levels above -0.3 m AHD for the rest of the year. The partial fill in winter and spring will support established wetland plant communities and provide additional habitat and food for frogs, turtles and waterbirds. The partial drawdown in summer and autumn will expose shoreline habitat to increase the diversity of vegetation communities, allow nutrient cycling and provide foraging habitat for shorebirds. Significant drawdown is unlikely under an average or wet climate scenario.

Planning scenario table

Table 2.2.4 Potential environmental watering for the lower Latrobe wetlands under a range of planning scenarios

Planning scenario	Drought	Dry	Average	Wet
Expected river and wetland conditions	No natural inflow from Durt-Yowan (Latrobe River), and wetlands are likely to dry completely	Minor natural inflow from Durt- Yowan (Latrobe River) in winter/ spring; expect moderate to substantial drying in summer	Moderate winter/ spring flow in Durt- Yowan (Latrobe River) is likely to fill or partially fill the wetlands; expect minor drying in summer	Major flow in Durt-Yowan (Latrobe River) in winter/spring and possibly autumn/ winter is likely to fill all wetlands with very little drying in summer
Sale Common
Potential environmental watering – tier 1 (high priorities)1	Top-up (any time, following bird breeding) Partial fill (with top-ups as required) Trigger-based fill or top-up to 0.5 m AHD (during December to January, if required) Partial drawdown (during December to March)	Top-up (any time, following bird breeding) Fill (with top- ups as required during August to November) Partial fill (with top-ups as required) Trigger-based fill or top-up to 0.5 m AHD (during December to January, if required) Partial drawdown (during December to March)	Top-up (any time, following bird breeding) Fill (with top-ups as required during August to November) Trigger-based fill or top-up to 0.5 m AHD (during December to January, if required) Partial fill (with top-ups as required during December to June) Partial drawdown (during December to March) if triggered
Dowd Morass
Potential environmental watering – tier 1 (high priorities)1	Top-up (any time, following bird breeding) Fill (any time to control salinity) Partial fill (with top-ups as required in August to December and April to June) Partial drawdown (during January to March)		Top-up (any time, following bird breeding) Fill (any time to control salinity) Partial fill (with top-ups as required in July and April to June) Fill (with top-ups as required during August to November)
Heart Morass
Potential environmental watering – tier 1 (high priorities)¹	Top-up (any time to permanently maintain water level above -0.3 m AHD) Top-up (any time, following bird breeding) Partial fill (with top-ups as required during August to December) Partial drawdown (during December to March)		Top-up (any time to permanently maintain water level above -0.3 m AHD) Top-up (any time, following bird breeding) Fill and partial flushing flow (during July to November)

¹ Potential environmental flows at the lower Latrobe wetlands are not classified as tier 1a, tier 1b or tier 2 because there is no limitation on the volume of water that can be supplied to the site from Durt-Yowan (Latrobe River). Water can be diverted to the lower Latrobe wetlands at any time of the year when flows are above -0.7 m AHD at Durt-Yowan (Latrobe River) at the Swing Bridge gauging station.

Engagement

Table 2 shows the partners with which West Gippsland CMA engaged when preparing the Latrobe system 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 West Gippsland Regional Catchment Strategy and West Gippsland Waterway Strategy.

Table 2 Partners and stakeholders engaged indeveloping the Latrobe system seasonal watering proposal

Partner and stakeholder engagement
Greening Australia Latrobe Valley Field Naturalist Club Inc. Native Fish Australia Parks Victoria Gippsland Water Department of Environment, Land, Water and Planning East Gippsland CMA Field & Game Australia (Heart Morass) Individual landholders Port of Sale Heritage Cruises Field & Game Australia (Dowd Morass and Sale Common) VRFish Gunaikurnai Land and Waters Aboriginal Corporation

Page last updated: 01/07/22