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The Glenelg River is an integral part of the Wimmera-Mallee headworks system, which supplies towns and properties across the western region. Moora Moora Reservoir and Rocklands Reservoir, in the upper Glenelg catchment and three weirs on the upper Wannon River, are all used to divert water from the Glenelg system to the Wimmera catchment. Water for the environment is actively managed in the main stem of the Glenelg River between Moora Moora Reservoir and Rocklands Reservoir and below Rocklands Reservoir. Passing-flow rules are in place for the Glenelg River and upper Wannon River.

The priority reaches of the Glenelg River that can be targeted by environmental flow releases are Moora Moora Reservoir to Rocklands Reservoir (reach 0), Rocklands Reservoir to 5-Mile Outlet (reach 1a), 5-Mile Outlet to the confluence with the Chetwynd River (reach 1b), Chetwynd River to the Wannon River (reach 2) and Wannon River to the tidal extent just below the confluence with Crawford River (reach 3). Water for the environment in the Glenelg system is released from Rocklands Reservoir for reach 1a via the reservoir wall outlet and for reach 1b via the 5-Mile and 12-Mile outlets. Releases are made at these points to meet objectives in these reaches as well as reaches 2 and 3. The Glenelg River estuary benefits from releases of water for the environment to upstream reaches, but releases do not currently target the estuary.

The Glenelg River upstream of Rocklands Reservoir (reach 0) runs mostly through the Grampians National Park and retains significant environmental values. Flows through this reach are affected by the operation of Moora Moora Reservoir and work is continuing in 2019–20 to confirm its flow requirements. Work is also continuing to better understand how environmental releases from Rocklands Reservoir can influence the health of the Glenelg River estuary, which is listed as a heritage river reach and a site of international significance under the Ramsar Convention.

Storage manager
Environmental water holder

System map

Environmental watering objectives in the Glenelg system

icon-objectives-fish
Protect and increase populations of native fish
Landscape icon
Maintain deep pool habitats and connectivity along the river
Platypus icon
Maintain the platypus population
Plant icon
Maintain the health and increase the abundance of in-stream and riparian vegetation (such as river red gums and Wimmera River bottlebrush)
Insect icon
Maintain a wide range and large number of waterbugs to provide energy, break down organic matter and support the river’s food chain
Water icon
Maintain water quality for native fish, waterbugs, aquatic vegetation and other waterdependent animals

Environmental values

The lower reaches of the Glenelg River are part of a landscape recognised as one of Australia’s 15 national biodiversity hotspots. Its listing is due in part to the aquatic life it supports including the endangered Glenelg freshwater mussel and Glenelg spiny crayfish. It is also home to platypus and populations of native fish including river blackfish, estuary perch, tupong and several species of pygmy perch. Some of these fish species migrate long distances upstream from the Glenelg River estuary to complete their life cycles. Frasers Swamp is another important feature of the upper Glenelg system, and is home to a healthy growling grass frog population.

The Glenelg River supports a variety of riparian vegetation communities including the endangered Wimmera bottlebrush. Riparian and floodplain vegetation is comprised of river red gum woodlands with paperbark, bottlebrush and tea tree understorey.

Recent conditions

The regions experienced below-average rainfall for much of 2018–19. Several natural high-flow events in July and August 2018 met many of the environmental flow objectives for those months, but inflows to storages were well-below average between September 2018 and April 2019. The dry conditions meant the VEWH only received a portion of allocation against its Wimmera-Glenelg environmental entitlement. As of March 2019, the VEWH had received 55 percent allocation for the year, but the total volume of available water for the environment was supplemented by system reserves that were carried over from 2017–18. Passing flows were suspended during the high-flow events in July and August, to reduce the flood risk to communities downstream of Rocklands Reservoir, and water accumulated at those times was used to help meet environmental objectives in spring.

A combination of natural inflows and managed environmental flows maintained continuous flow between Rocklands Reservoir and the Glenelg estuary for most of 2018–19. The only disruption to this flow occurred in March 2019, when releases were suspended for two weeks to allow maintenance works on headworks infrastructure, carp screen cleaning and an upgrade of the Sandford fishway.

Water for the environment was used throughout the year to provide opportunities for native fish, platypus and crayfish to disperse between river reaches and to access a variety of habitats throughout the system. Spring flows also watered riparian vegetation including recently recruited seedlings, and helped move nutrients, leaf litter and small branches from the riverbank into the river channel where they can provide food, energy and habitat for aquatic biota. Low flows delivered during 2018–19 maintained the quality and quantity of water in riffles and pools along the river, to provide suitable habitat for waterbugs, native fish and other aquatic species. Occasional freshes reduced salinity and water temperature and increased dissolved oxygen concentrations in deeper pools along the river system.

Hot and dry conditions through summer and autumn increased seepage and evaporation losses, which meant that some target low flows did not achieve intended flow rates in downstream reaches. Fish monitoring conducted as part of the Victorian Environmental Flows Monitoring Assessment Program (VEFMAP) in autumn recorded a nationally threatened Australian grayling in the Glenelg River below Casterton (reach 3) for the first time in 122 years. The presence of Australian grayling and other fish species that rely on specific flows in freshwater reaches and the estuary indicates that managed environmental flows in the Glenelg River are helping to meet the requirements of native fish.

In late November 2018, water for the environment was delivered over 12 days to reach 0 from Moora Moora Reservoir. This is the second time water for the environment has been released from Moora Moora Reservoir, and the event was monitored to understand how water can be delivered from the reservoir to maintain and improve remnant plant and animal populations. Temporary gauges installed in reach 0 showed that the released water spread along several natural flow paths and did not contribute any detectable flow at the end of the reach.

Scope of environmental watering

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

Potential environmental watering action

Functional watering objective

Environmental objective

Summer/autumn freshes targeting reach 1a (two freshes of 60 ML/day for two to three days each during December to May)

  • Scour sand from pools to increase the quality and quantity of fish and waterbug habitat
  • Inundate emergent vegetation on the lower banks
  • Flush pools to improve water quality and lower temperatures
  • Provide sufficient flow to allow platypus to access habitat
Fish icon Plant iconMountain iconsPlatypus iconInsect iconWater drop icon

Summer/autumn freshes targeting reaches 1b (two freshes of 100 ML/day for two to three days each during December to May)

Summer/autumn freshes targeting reach 2 (two freshes of 150 ML/day for two to three days each during December to May)

Summer/autumn freshes targeting reach 3 (two freshes of 150 ML/day for three days each or natural during January to April)

Summer/autumn low flows targeting reach 1a (10 ML/day or natural during December to May)1

  • Protect against rapid water quality decline over the low-flow period
  • Maintain edge habitats, pools and shallow-water habitat for fish, waterbugs and platypus
  • Maintain a near-permanent inundated stream channel to promote the growth of in-stream vegetation and prevent encroachment by terrestrial plants

Fish iconWater drop iconPlatypus iconPlant iconInsect icon

Summer/autumn low flows targeting reach 1b (15 ML/day or natural during December to May)1

Summer/autumn low flows targeting reach 2 (25 ML/day or natural during December to May)1

Summer/autumn low flows targeting reach 3 (80 ML/day or natural during January to
April)

Autumn/winter low flows targeting reach 3 (260 ML/day or natural during May to June)

  • Trigger fish movement and possibly assist seagrass germination in the estuarine reach downstream of reach 3, as based on estuary salinity profiles

Fish iconPlant icon

Winter/spring freshes targeting reach 1b (one to five freshes of 250 ML/day for one to
five days during June to November)2

  • Wet benches to improve the condition of emergent vegetation and maintain habitat diversity
  • Provide adequate depth for fish passage and cue fish movement
  • Provide triggers for platypus burrow selection
  • Scour sand from pools to improve the quality of fish habitat
  • Inundate vegetation in the river channel and on the channel benches to support recruitment and growth

Fish iconMountain iconsPlatypus iconPlant icon

Winter/spring freshes targeting reach 2 (one to five freshes of 300 ML/day for one to five days during June to November)

Winter/spring low flows targeting reach 1a (60 ML/day or natural in June–November)1, 3

  • Maintain water quality for fish and waterbugs\
  • Inundate aquatic vegetation to maintain its condition and prevent encroachment by terrestrial species
  • Maintain shallow-water habitat for fish, waterbugs and platypus

Fish iconPlant iconPlatypus iconInsect icon

Winter/spring low flows targeting reach 1b (100 ML or natural per day in June–November)1, 3

Winter/spring low flows targeting reach 2 (160 ML/day or natural in June–November)1, 3

Trial release to reach 0 (up to 50 ML/day over a 4–5 day period)
  • Inundate benches to increase habitat and allow widespread fish passage and keep the estuary mouth
    open (based on estuary mouth flows)

Fish iconMountain icons

Winter/spring trial release to reach 0 (up to 50 ML/day during July to November)
  • Develop an operational understanding of our ability to deliver environmental flows to support plant, waterbug
    and animal populations in this reach including the capacity of infrastructure, metering and safety considerations

Fish iconPlant iconInsect icon

1 Cease-to-flow events occur naturally in the Glenelg system and may be actively managed with deliveries of water for the environment to reduce stress on environmental values. In the most-recent flows study, the recommendation is that cease-to-flow events should occur as infrequently as possible and not exceed the duration of events that might have occurred naturally. Cease-to-flow events ideally should be followed with a fresh.

2 Winter/spring freshes in reach 1a are important to the health of the Glenelg River but due to operational constraints and potential flooding risks they can only be achieved through natural events.

3 Passing flows provided under the environmental entitlement generally provide winter/spring low flows. However, if passing flows are reduced, managed releases of water for the environment may be required to supplement them.

Engagement

Table 2 shows the partners, stakeholder organisations and individuals with which Glenelg Hopkins CMA engaged when preparing the Glenelg 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 Glenelg Hopkins Regional Catchment Management Strategy and Glenelg Hopkins Waterway Strategy for further details.

Table 2 Partners and stakeholders engaged in developing the Glenelg system seasonal watering proposal

Partner and stakeholder engagement
  • Friends of the Glenelg River
  • Glenelg River User Group
  • Parks Victoria
  • Victorian Fisheries Authority
  • Individual landholders
  • Balmoral Bush Nursing Centre
  • Balmoral Post Office
  • Glenelg River Boat Cruises
  • Grampians Resort
  • Paestan Canoe Hire
  • Nelson Boat and Canoe Hire
  • Vickery Brothers (sand extraction)
  • Department of Environment, Land, Water and Planning
  • GWMWater
  • Victorian Environmental Water Holder
  • Wimmera Catchment Management Authority
  • Balmoral Angling Club
  • Casterton Angling Society
  • Dartmoor Angling Club
  • Individual anglers
  • South-west Fishing Reports
  • VRFish
  • Barengi Gadjin Land Council Aboriginal Corporation
  • Gunditj Mirring Traditional Owners Aboriginal Corporation

Page last updated: 12/12/19