VEWH - 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 the Latrobe River between its confluence with the Thomson River, and they form part of the Gippsland Lakes system, with Dowd Morass and Heart Morass adjoining Lake Wellington.

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

Provide foraging and breeding habitat for waterbirds including threatened, migratory and colonial nesting species

Reduce the abundance of carp

Support the dispersal, germination and survival of wetland plant communities Manage the extent and density of invasive plants, particularly the spread of giant rush at Sale Common

Environmental values

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

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 many species of ducks.

Together, the lower Latrobe wetlands function as a diverse and complementary ecological system. Colonial 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 contain vegetation types that are threatened (such as swamp scrub, brackish herbland and aquatic herbland).

Social and economic values

Sale Common, which is located close to the city of Sale, is a state game refuge with extensive walking tracks and boardwalks that provide opportunities for passive recreation including walking, bike riding and observing native plants and animals. Dowd Morass is a state game reserve commonly used for duck hunting. Heart Morass consists of mostly private landholdings and is also used for duck hunting.

Conditions 2018

Climatic conditions in West Gippsland were warmer and drier than average during the 2017–18 water year. Minor flooding in the Latrobe River occurred in September and December 2017, but the flows were not of sufficient duration to deliver meaningful inflows to the wetlands.

The regulator to Dowd Morass was opened from October
to December 2017 and again in April 2018. The regulator was opened when the Latrobe River was high, to allow low-salinity water from the Latrobe River to reduce salinity in Dowd Morass.

At Heart Morass, flows through the regulator raised the water level by 5 cm and surface coverage at the wetland increased from about 40 to 80 percent. The managed inflows reduced salinity in the wetland and inundated the aquatic grasses, which provided food for waterbirds. Water was allowed to draw down naturally in Heart Morass and Dowd Morass from the middle of summer.

Sale Common was fully dry in June 2017, and after three days of inflows in September 2017 it was one-third full. By November 2017, the site was completely dry, apart from the long waterhole. Large stands of amphibious wetland vegetation (such as knotweed and club-rush) dominated the wetland over summer. By autumn, the amphibious
vegetation began to desiccate and was replaced by terrestrial grasses. Sale Common has a more-varied water regime than Heart Morass and Dowd Morass, mainly because it is smaller but also because it received managed and unregulated inflows and drawdowns.

Scope of environmental watering

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

Potential environmental watering	Environmental objectives
Sale Common
Partial fill (any time)	Control of invasive vegetation and algae Mimic the natural inundation regime
Fill or partial fill (July–November)	Encourage the growth and recruitment of wetland plants, particularly tall marsh, aquatic herbland and aquatic sedgeland Provide feeding and breeding habitat for wetland animals, particularly waterbirds and frogs
Fill or partial fill (February–May)	Provide feeding and sheltering habitat for wetland animals, particularly waterbirds and frogs Discourage the spread of giant rush
Partial drawdown (primarily August–March)	Oxygenate surface soils, break down accumulated organic matter and cycle nutrients Encourage the growth and recruitment of wetland plants across the wetland bed Reduce the abundance of carp
Dowd Morass and Heart Morass
Partial fill (Dowd Morass: July–November) (Heart Morass: July–December)	Encourage colonial waterbird breeding Reduce salinity Encourage the growth and recruitment of wetland plants, particularly swamp scrub, tall marsh, aquatic herbland and brackish herbland Provide feeding and breeding habitat for wetland animals, particularly waterbirds and frogs
Partial drawdown (year-round, primarily August–March)	Oxygenate surface soils, break down accumulated organic matter and cycle nutrients Increase the growth and recruitment of wetland plants, particularly swamp shrub, tall marsh, aquatic herbland and brackish herbland Reduce the abundance of carp
Partial fill (any time)	Avoid or mitigate risks to wetland plants due to adverse salinity and pH Mimic the natural inundation regime
Fill or partial fill (February–May)	Provide feeding habitat for wetland animals, particularly waterbirds

Risk management

In preparing its seasonal watering proposal, West Gippsland 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.