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The Macalister River flows from Mt Howitt in the Alpine National Park to join the Thomson River south of Maffra. The river meanders in a south-easterly direction through predominantly forested, confined valleys and narrow floodplains upstream of Lake Glenmaggie to cleared, wide, alluvial floodplains downstream. The Macalister River is regulated by Lake Glenmaggie, the major water-harvesting storage and Maffra Weir, a small diversion weir located further downstream in the Maffra township. Both storages divert water for irrigation, urban and industrial purposes. Environmental water is stored in Lake Glenmaggie.

Before Lake Glenmaggie was built, the Macalister River would regularly receive high and medium flows in winter and spring. Although Lake Glenmaggie regularly spills, these flows are now less common as they are harvested by the storage. A notable impact of irrigation and water harvesting is reversed seasonality of flows between Lake Glenmaggie and Maffra Weir, where summer flows are higher than natural due to the delivery of irrigation water. Winter flows are lower-than-natural because a high proportion of the inflows are harvested. Downstream of Maffra Weir, most flows are diverted for irrigation in summer and autumn. The changed hydrology restricts fish migration, limits the growth and recruitment of in-stream and riparian plants and reduces the quality of in-stream habitat.

Maffra Weir is a major barrier to fish movement and environmental flows that target migratory fish objectives mainly focus on reach 2, which is downstream of the weir. All other objectives apply to both reaches 1 and 2.

Storage manager
Environmental water holder

System map

Macalister 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 Macalister River

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Increase the range and population size of native fish species including Australian grayling and other native migratory fish
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Restore communities of waterbugs, which break down organic matter, provide a source of food for other animals and support the river’s food chain
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Improve vegetation communities including macrophytes (large water plants) in the river channel

Improve fringing woody vegetation in the riparian zone
Maintain the form of the river bank and bed

Environmental values

There are seven migratory native fish species in the Macalister River that move between freshwater and marine environments to complete their life cycle. These are the Australian grayling, short- and long-finned eel, tupong, Australian bass, short-headed lamprey and common galaxias. Platypus and water rat are widely distributed through the Macalister River and its tributaries.

The riparian vegetation corridor is fragmented. Immediately downstream of Lake Glenmaggie, the vegetation is in good condition and includes remnant river red gums. It is degraded elsewhere. The cover of in-stream vegetation and non-woody plants that colonise the fringes of the river (such as reeds, sedges and rushes) have declined in recent years. The decline may be due to a combination of increased water turbidity, erosion and lack of an appropriate water regime to encourage plant growth.

Social, cultural and economic values

The Macalister Irrigation District is the major economic driver in the area and water from the Macalister system is highly valued by the local community. As a result, there is a genuine interest in the health of the Macalister River, particularly around water quality, erosion and vegetation condition. People also use the river for recreational fishing and birdwatching. The waterways in the Macalister system including the Macalister River continue to hold significance for Traditional Owners. Waterways and wetlands in the region contain important ceremonial places and for thousands of years the Macalister River provided resources such as food and medicines for the Gunaikurnai people.

Conditions mid-2017

The last two years have seen the Macalister River experience very different climatic conditions. 2015–16 was very dry, with average to below-average rainfall in winter and a dry summer. In contrast, 2016–17 had average to above-average rainfall throughout the winter and spring, followed by a dry summer. Irrigation demands over summer and autumn have been relatively high. Environmental water deliveries over the last two years have mainly been used to provide autumn freshes to trigger Australian grayling spawning, winter freshes for migration and spawning of Australian bass and tupong, and low flows to provide connectivity between habitats for fish movement..

High rainfall in winter and spring 2016 resulted in Lake Glenmaggie spilling from July to November. The river experienced two bankfull flows in this period, the first bankfull flows in the Macalister River since 2012. These events help to disturb and reset dominant riparian vegetation. The floods also inundated some floodplain habitats, which provided food and breeding opportunities for turtles, frogs and some waterbirds.

All planned environmental watering events for 2016–17 were achieved, either through managed delivery of environmental water or through spill releases from Lake Glenmaggie.

Scope of environmental watering

Table 1 Potential environmental watering actions and objectives for the Macalister system

Potential environmental watering

Environmental objectives

Macalister River reaches 1 and 2

Autumn/winter baseflows (35–90 ML/day in May–July)

  • Provide habitat for waterbugs
  • Provide passage for fish to undertake localised movements
  • Maintain water quality in pools and connectivity for fish, platypus and
    water rats
  • Maintain areas of slow-moving water for submerged aquatic vegetation

Spring fresh (1,500 ML/day for 3 days inSeptember–October)

  • Trigger upstream migration and recruitment for juvenile fish
  • Trigger upstream migration for lampreys and eels
  • Provide variability in water levels and wet the fringing woody vegetation
  • Scour sediment exposing fresh habitat areas
  • Provide food and habitat for waterbugs

Macalister River reach 2

Autumn fresh (350 ML/day for 4–5 days in April–May)

  • Trigger downstream migration and spawning of Australian grayling

Winter fresh (700 ML/day for 4–5 days in June–August)

  • Trigger downstream migration and spawning of tupong and Australian
    bass

Spring/summer fresh (700 ML/day for 5 days in September–December)

  • Trigger upstream migration and recruitment for juvenile fish
  • Trigger upstream migration for adult lampreys and eels

Summer/autumn fresh (140 ML/day for 3 days in December–May)

  • Provide sufficient depth to allow fish to move throughout the reach
  • Flush pools to maintain water quality for waterbugs

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

Engagement

Waterway managers meet communities on environmental watering regionally, although other program partners also play a role.

In each region of Victoria, community engagement on environmental watering happens when environmental watering objectives and priorities are scoped (long term and annually), when delivering environmental water, and when reporting on environmental watering results.

In the West Gippsland region communities are involved in decisions about the Thomson and Macalister river systems and the Lower Latrobe wetlands. The community is engaged informally and through the Macalister river Project Advisory Group.

Who is engaged and how

Recreational users

A representative of VRFish sits on the Macalister river Project Advisory Group.

West Gippsland Catchment Management Authority engages with Field & Game Australia when developing the Lower Latrobe wetlands seasonal watering proposal (annual scoping). Field & Game Australia shares wetland bird count data with the Catchment Management Authority which helps with reporting on environmental watering outcomes.

The Catchment Management Authority notifies many recreational user groups about environmental water deliveries. These groups include canoe clubs, outdoor education companies and school groups (many of whom come from outside of the region). These groups are interested in managing safety and also achieving opportunities for shared benefits from environmental watering (e.g. kayaking on higher flows in the Thomson river).

Environment groups

Representatives from environment groups (Environment Victoria, Landcare and Native Fish Australia) sit on the Macalister river Project Advisory Group.

Irrigators/farmers

Irrigation representatives sit on the Macalister river Macalister river Project Advisory Group.

Southern Rural Water sends environmental water delivery notifications to their irrigation customers on behalf of the Catchment Management Authority. These irrigation customers are often primarily interested in environmental watering from a safety and infrastructure protection perspective.

Traditional owners

Through the Catchment Management Authority Indigenous facilitator, the Gunaikurnai Land and Waters Aboriginal Corporation has been invited to join the Macalister river Project Advisory Group.

The Catchment Management Authority and Gunaikurnai Land and Waters Aboriginal Corporation have a Memorandum of Understanding. The Catchment Management Authority recognises the recently developed Gunaikurnai Land and Waters Aboriginal Corporation draft Whole Of Country Plan which contains aspirations for rivers and wetlands in Gippsland.

Councils

The Wellington Shire Council is a member of the Macalister river Macalister river Project Advisory Group.

The Wellington Shire Council, the Latrobe City Council and the Baw Baw Shire Council are all on the Southern Rural Water environmental water delivery notification list.

General public

Public signage informing the general public about upcoming environmental water deliveries is set up a few days before a planned delivery along key recreational sites in the upper Thomson River. This is for primarily for public safety purposes.