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 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.

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

Climatic conditions in the Latrobe catchment in 2020-21 were close to the long-term average, with some periods of above-average rainfall observed. Several minor floods in the lower reaches of Durt-Yowan (Latrobe River) in winter and spring spilled into Dowd Morass. The VEWH’s entitlement for the lower Latrobe wetlands is not limited in volume, and regulator gates may be opened opportunistically based on the water height in Durt-Yowan (Latrobe River) at Swing Bridge.

Environmental watering at the lower Latrobe wetlands was managed in line with an average climate scenario in 2020-21, and all planned watering actions were achieved. A combination of natural floods in winter and spring and managed inflows of water for the environment fully or partly filled Sale Common, Dowd Morass and Heart Morass in 2020-21. This watering followed two years of relatively dry conditions at all three wetlands, and it helped improve the condition of fringing wetland vegetation communities and provided feeding and breeding habitat for aquatic animals and waterbirds. Water for the environment was used to partly flush Heart Morass from October to January, to export accumulated salts and sulfates and transfer nutrients between the river and the wetland. Heart Morass and Dowd Morass began to draw down over the warmer months, and the regulator gates were opened as needed (and where water quality allowed) to prevent complete drying. Sale Common was actively managed to maintain water levels between a partial fill and full supply levels year-round. No trigger-based fills were required to prevent or respond to declines in water quality at any of the lower Latrobe wetlands in 2020-21.

Environmental watering in 2021-22 aims to build on the achievements of 2020-21, protecting high-priority environmental values, supporting key ecohydrological functions and providing refuge habitat in the event of drought. Fill events will be targeted at all wetlands to achieve these outcomes, where flow conditions and water quality in Durt-Yowan (Latrobe River) allow.

Traditional Owner cultural values and uses

The Gunaikurnai have had a continued connection to Gunaikurnai Country for thousands of years, including with the waterways that feed into the lower Latrobe wetlands. For the Gunaikurnai as traditional custodians, there are immense challenges to heal, protect and manage Country which has been drastically altered since colonisation. Gunaikurnai see all of Country as connected with no separation between landscapes, waterways, coasts and oceans and natural and cultural resources – the cultural landscape is interdependent.

The Gunaikurnai Land and Waters Aboriginal Corporation (GLaWAC) is working with the West Gippsland CMA to determine how to express Gunaikurnai objectives for water in a way that contributes to seasonal watering proposals from the perspective of traditional custodians, with traditional knowledge.

Leading up to the Seasonal Watering Plan 2021-22, the focus on the lower Latrobe wetlands has included:

incorporating the findings of the Durt-Yowan(Latrobe River) Aboriginal Waterways Assessment into the Latrobe Environmental Water Requirements Investigation, which will assist the CMA to consider cultural benefits in water for the environment planning and decision-making for the lower Latrobe wetlands
on-Country discussions with GLaWAC and Gunaikurnai Elders and Community to examine cultural values and uses
discussions about the importance of maintaining the wetlands as a freshwater system to support culturally significant species including totem species
the importance of the lower Latrobe wetlands to the Gunaikurnai, traditionally and today
concerns about water quality and increasing salinity
concerns about pest species including carp. GLaWAC is sharing with the West Gippsland CMA its knowledge of plant and animal species of cultural significance in and around the waterways of the Latrobe Valley, and the importance of specific watering decisions to support them.

Watering requirements to support cultural values and uses include:

timing of environmental watering planned in partnership with 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; the lower Latrobe wetlands are an important resource for the Gunaikurnai
providing connectivity between reaches and onto floodplains to support dependent flora and fauna with cultural values and uses of significance to the Gunaikurnai
maintaining water quality to support the health of native flora and fauna with cultural values and uses of significance 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 legislation and policy commitments (for example 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 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 that contribution, and indicating progress towards this objective.

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 watering with Traditional Owner outcomes in the lower Latrobe wetlands. In 2021-22, this is planned to include a jointly managed Gunaikurnai environmental watering event in Dowd Morass. The overarching objective is to deliver water for the environment to the western end of the morass in a way that better aligns with the natural flow paths of Durt- Yowan (Latrobe River) and wetland, supporting enhanced environmental and cultural outcomes. The flow will be delivered at a time of cultural significance to Gunaikurnai people and be aligned with appropriate seasonal conditions (water quality and weather) to support healthy Country.

Social, recreational and economic values and uses

In planning the potential watering actions in Table 1, 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)
socio-economic benefits (such as commercial eel and carp fishing).

Scope of environmental watering

Table 1 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 Australian Height Datum [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 Discourage invasive plants, particularly the excessive spread of giant rush
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 0.5m 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 and April to June²) IMAGE	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 0.6m AHD during August to November)	Wet reed beds and deep water next to reedbeds to provide waterbird nesting habitat and to 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 0.3 m AHD during August to December¹ and April to June)	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.

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: 22/01/21