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 4.2 Glenelg system
System overview
The Glenelg River rises in the Grampians and flows west through Harrow and then south to Casterton and Dartmoor. The Glenelg River estuary flows west from Dartmoor and passes through South Australia for a short distance before returning to Victoria and flowing into the sea at Nelson. At over 500 km, the Glenelg River is one of the longest rivers in Victoria.
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 Glenelg River 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 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 reaches 1b, 2 and 3 via the 5-Mile and 12-Mile outlets.
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 Hopkins CMA is investigating the influence of managed environmental water on the Glenelg River estuary, which is listed as a heritage river reach and a site of international significance under the Ramsar Convention.
Trial releases were delivered from Moora Moora Reservoir above Rocklands Reservoir (reach 0) in 2017–18, 2018–19 and 2019–20. The results of that trial will be analysed to inform future decisions about potential environmental water use in reach 0.
Environmental values
The Glenelg River starts in the Grampians (Gariwerd) National Park and flows to the sea through the Lower Glenelg National Park. The lower reaches of the Glenelg River are part of a landscape recognised as one of Australia’s 15 national biodiversity hotspots, and the Glenelg Estuary and Discovery Bay site is Australia’s most recent listing under the Ramsar Convention.
The Glenelg River supports a range of rare and unique aquatic life 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, kooyang (short-finned eel), tupong and three species of pygmy perch including the threatened variegated and Yarra pygmy perches. Some of these fish species migrate long distances to and 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 streamside vegetation communities and species including the endangered Wimmera bottlebrush. Streamside and floodplain vegetation is comprised of river red gum woodlands with paperbark, bottlebrush and tea tree understorey.
Environmental watering objectives in the Glenelg River
     Protect and increase populations of native fish
   Maintain deep pool habitats and connectivity along the river
     Maintain the platypus population
   Maintain the health and increase the abundance of in-stream and streamside vegetation (such as river red gums and Wimmera River bottlebrush)
    Maintain a wide range and large number of waterbugs to provide energy, break down organic matter and support the river’s food chain
    Maintain water quality for native fish, waterbugs, aquatic vegetation and other water-dependent animals
  144 | Victorian Environmental Water Holder | Seasonal Watering Plan 2020–21

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