River regulation and water extraction from the Latrobe, Thomson and Macalister rivers has 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 the Latrobe River.
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 openwater habitat at the wetlands year-round. The wetlands also support threatened vegetation communities including swamp scrub, brackish herbland and aquatic herbland.
Climatic conditions in the lower Latrobe wetlands’ catchment varied throughout 2019–20. Total rainfall was below average, but there were still some significant rain events that increased river levels throughout winter and spring 2019, particularly from the Latrobe River catchment, and they caused minor overbank flooding in late spring 2019 and again in late autumn 2020. The VEWH’s entitlement for the lower Latrobe wetlands is not limited in volume, and regulator gates may be opened opportunistically based on water height in the Latrobe River at Swing Bridge.
Heart Morass, Dowd Morass and Sale Common were allowed to draw down in 2018–19 to allow the die-off of aquatic vegetation, promote nutrient cycling and allow terrestrial grasses and sedges to establish. Overbank flows in late winter and early spring 2019 partly refilled the wetlands. Environmental water was subsequently delivered as required (and when salinity in the Latrobe River estuary was not too high) to maintain water quality and habitat for aquatic and terrestrial animals, and to support the growth and flowering of semi-aquatic vegetation. Complete and near-complete fills were achieved at Dowd Morass and Heart Morass respectively in 2019–20, and a partial fill was achieved at Sale Common. A flushing flow was delivered to Heart Morass in spring 2019 to export salts and sulfates. Water levels at all wetlands were drawn down partially over summer to expose mudflats, which created feeding opportunities for wading birds and oxygenated soils to promote seed germination. High rainfall in late April and May 2020 caused minor flooding, allowing deliveries of freshwater to the lower Latrobe wetlands again in autumn.
Some water was retained in Dowd Morass and Sale Common to maintain habitat for Australasian bittern and other significant waterbirds that were observed at these sites during summer. Maintaining this habitat will likely be a priority throughout 2020–21.
The Gunaikurnai have had a continued connection to Gunaikurnai Country for thousands of years, including with the waterways in the Latrobe River system. 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.
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.
For the Latrobe River system this has included:
GLaWAC shared with the West Gippsland CMA 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:
In planning the potential watering actions in Table 1, the West Gippsland CMA considered how environmental flows could support values and uses including:
Table 1 Potential environmental watering actions and objectives for the lower Latrobe wetlands
Potential environmental watering action | Functional watering objectives | Environmental objectives |
|---|---|---|
Sale Common | ||
Partial fill (during July to December, with top-ups as required to maintain water height above 0.3m AHD[Australian Height Datum]) | Maintain a water level at 50 percent or greater (0.3m AHD) to:
|
|
Fill (during August to November and maintain at full level for at least two months)1 |
|      |
Top-up (anytime, following bird breeding event if required) |
| |
Dowd Morass | ||
Partial fill (during April to December, with top-ups over summer to maintain surface coverage)2 |
| |
Fill (during August to November) |
| |
Trigger-based fill or partial fill to control salinity (any time)3 |
| |
Top-up (anytime, following bird breeding event if required) |
|
|
Heart Morass | ||
Partial fill (during August to December, with top-ups as required to maintain water level above -0.3 m AHD5) |
|
|
Partial wetland flush (during June to November) |
|
|
Trigger-based fill or partial fill to respond to acid sulfate soil exposure or control salinity (any time)3 |
|
|
Top-up (anytime, following bird breeding event if required) |
|
|
1 While a full fill is the target, if salinity in the Latrobe River is too high a partial fill may be provided instead, helping to achieve some of the listed functional watering actions. This is most likely to eventuate under drought conditions.
2 Timing of this flow changes depending on the scenario. An extended partial fill may be required under a drought scenario, however under dry to wet scenarios, partial fills either side of the full fill over late winter and spring are preferred. Top-ups over summer are unlikely under a drought scenario, as reduced flow in the Latrobe River is likely to increase salinity levels beyond a tolerable limit for wetland filling.
3 Trigger-based events may override other planned watering actions if required, to maintain conditions at the site.
4 If salinity level in the Latrobe River exceeds 15,000 μS/cm, a fill or partial fill will not be provided.
5 Maintaining the water level above -0.3m AHD is a high priority, to avoid exposing acid sulfate soils.
6 If the salinity level in the Latrobe River exceeds 10,000 μS/cm, a fill or partial fill will not be provided.
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 |
|---|
|
Page last updated: 22/01/21
