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The Wimmera River rises in the Pyrenees Range near Elmhurst and flows through Horsham, Dimboola and Jeparit before terminating at Lake Hindmarsh, which is Victoria's largest freshwater lake and the first of a series of terminal lakes. The Wimmera receives flows from several regulated tributaries including the MacKenzie River and the Mount William and Burnt creeks. These tributaries, Bungalally Creek and the Wimmera River downstream of Mount William Creek can receive environmental water. In exceptionally wet periods, Lake Hindmarsh may overflow into Outlet Creek and on to Lake Albacutya, an internationally recognised Ramsar-listed wetland. There are several wetlands beyond Lake Albacutya as well.

The waterways in the Wimmera system hold significance for Traditional Owners and their Nations. The Registered Aboriginal Parties (RAPs) in the Wimmera River catchment are the Barengi Gadjin Land Council Aboriginal Corporation (BGLC) and Martang Pty Ltd. Representatives of the BGLC were engaged during the preparation of this section. A trial watering is proposed for the Ranch Billabong near Dimboola, on land managed by BGLC. The intent is to provide a more-natural flooding regime in the billabong system to restore native plant and animal habitats that have been disconnected by levies and changed watering regimes in the Wimmera River. Ranch Billabong is also very significant to the Traditional Owners and their Nations, and it was the home of many generations of Wotjobaluk peoples.

Storage manager
Environmental water holder

System map

Wimmera System
Grey river reaches have been included for context. The numbered reaches indicate where relevant environmental flow studies have been undertaken. Coloured reaches represent potential watering sites.

Environmental watering objectives in the Wimmera system

Fish icon
Protect and increase populations of native fish, including one of Victoria’s few self-sustaining populations of freshwater catfish
Water icon
Maintain and improve water quality to provide suitable conditions for waterbugs, native fish and other water-dependent plants and animals
Platypus icon
Maintain and increase the resident platypus population by providing places to rest, breed and feed, as well as opportunities for juveniles to disperse
Plant icon
Improve the condition, abundance and diversity of aquatic, emergent and riparian vegetation
Insect icon
Increase the abundance and diversity of waterbugs, which break down dead organic matter and support the waterway’s food chain

Environmental values

The Wimmera system is home to many plant and animal species. It supports populations of native fish including one of Victoria's few self-sustaining populations of freshwater catfish, as well as flat-headed gudgeon, carp gudgeon, river blackfish, southern pygmy perch and Australian smelt. It also has the critically endangered Wimmera bottlebrush.

The Wimmera River supports abundant native fish, waterbird, turtle, frog and native water rat populations and one of Victoria's few self-sustaining populations of freshwater catfish.

The MacKenzie River contains the only self-sustaining population of platypus in the Wimmera and supports populations of native fish, including river blackfish, waterbugs, threatened Glenelg spiny crayfish and turtles. During dry periods, the middle and upper reaches of the MacKenzie River maintain regular flow (due to managed releases from Lake Wartook) and provide refuge for these populations.

Vegetation along Burnt and Bungalally creeks provide habitat corridors for terrestrial and riparian wildlife and upper Burnt Creek contains an important native fish community and a population of threatened western swamp crayfish. Mount William Creek supports regionally important populations of river blackfish, southern pygmy perch and threatened western swamp crayfish.

Dock Lake is a natural wetland that was modified and used as part of the Wimmera-Mallee headworks system. When it is inundated, Dock Lake supports large populations of feeding and breeding waterbirds. It also supports frogs and small-bodied native fish. It is no longer used for water storage and is frequently dry.

Social and economic values

The Wimmera system offers many popular recreational activities including walking, boating, rowing, waterskiing, fishing and camping, and it provides important amenity for local communities. Events held on waterways throughout the Wimmera catchment include waterskiing at the annual Kanamaroo Festival in Horsham, the Horsham Triathlon, the Dimboola Rowing Regatta and the Horsham, Jeparit and Dimboola fishing competitions.

Conditions 2018

Average rainfall during winter 2017 led to modest, unregulated flows in the Wimmera River's western tributaries, although rainfall in the eastern catchment was below average. During winter and spring, many of the environmental flow objectives in the Wimmera system were met naturally due to unregulated flows or through releases of water from Lake Wartook. Passing flows that were available at Lake Lonsdale were temporarily suspended and released later in the year to meet Wimmera River flow objectives.

Allocations to the environmental entitlement reached 81 percent in September 2017, based on water reserves set aside during the wet conditions during the 2016–17 season. Spring, summer and autumn 2017–18, had below-average rainfall and little-to-no inflow to storages; as a result, there were no additional allocations to the environment after September 2017. Accumulated passing flows were used to meet environmental demand between late spring and mid-January 2018. Water allocated to the environmental entitlement was used to meet demand after that.

The CEWH did not receive any allocation in 2017–18. The water that was allocated to the CEWH in 2016–17 was carried over to 2017–18 and used for the first time in the Wimmera system to support environmental outcomes in the Wimmera River and Mount William Creek.

The wet conditions in winter and spring 2017–18 and deliveries of water for the environment have improved the condition of the rivers and creeks in the Wimmera system.

Fish monitoring in the Wimmera River in March 2017 showed that populations of golden perch and freshwater catfish have been maintained along all reaches, and there is a healthy population of small-bodied native fish. Fish surveys in the MacKenzie River and Burnt Creek showed that southern pygmy perch successfully recruited in summer 2017–18. In autumn 2018, high abundances of young-of-year fish were found at many sites, which coincided with priority reaches that had received environmental flows. Other native fish identified include river blackfish, flat-headed gudgeon, Australian smelt, obscure galaxiids and carp gudgeon. The threatened western swamp crayfish was also found in MacKenzie River and Burnt Creek in 2017. Platypus surveys in MacKenzie River in both 2017 and 2018 also showed the platypus population is slowly increasing in abundance, with three young individuals caught for the first time.

Scope of environmental watering

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

Potential environmental watering

Environmental objectives

Wimmera River (reach 4)

Summer/autumn low flows (15–30 ML/day or natural1 in December–May)

  • Maintain in-stream habitat to support native fish populations and waterbugs
  • Maintain near-permanent inundation of the stream channel for riparian vegetation and to prevent the growth of terrestrial plants in the streambed

Winter/spring low flows (15–30 ML/day in June–November)

  • Provide flow variability to maintain various habitat types

Summer/autumn freshes (1–3 freshes of 70 ML/day for 2–7 days in December–May)

  • Flush pools to improve water quality and maintain habitat for fish and waterbugs
  • Provide fish passage to allow fish to move through the reach

Winter/spring freshes (1–5 freshes of 70 ML/day for 1–4 days in June–November)

  • Flush pools to improve water quality and maintain habitat for fish and waterbugs
  • Provide fish passage to allow fish to move through the reach

Winter/spring freshes (1–5 freshes of 70 ML/ day for 1–4 days in June–November

  • Stimulate fish movement and provide fish passage to allow fish to move through the reach
  • Maintain water quality to support fish populations

Winter/spring freshes (1–3 freshes of 200 ML/ day for 1–3 days in June–November2)

  • Wet lower benches to entrain organic debris and promote habitat diversity
Winter/spring freshes (1–2 freshes of up to 1,300 ML/day for 2–3 days in June–November)
  • Flush surface sediments from hard substrates to improve habitat quality and support waterbugs 
  • Wet higher benches to entrain organic debris and promote habitat diversity 
  • Maintain the quality, diversity and extent of submerged and emergent aquatic vegetation for fish habitat

MacKenzie River (reach 2 and 3)

Year-round low flows (of 2–27 ML/day or natural, year-round)1

  • Maintain edge habitats and deeper pools and runs for waterbugs 
  • Maintain near-permanent inundated stream channel for riparian vegetation and to prevent the growth of terrestrial plants including the Wimmera bottlebrush in the stream bed, and support growth of aquatic vegetation for fish habitat 
  • Maintain sufficient area of pool habitat for native fish populations 
  • Facilitate the annual dispersal of juvenile platypus into the Wimmera River

Summer/autumn freshes (3–4 freshes of 5–50 ML/day for 2–7 days each in December– May)

  • Provide variable flows during the low-flow season for waterbugs, for fish movement and to maintain water quality and habitat diversity

Winter/spring freshes (5 freshes of 35–55 ML/ day for 2–7 days in June–November)

  • Stimulate fish movement and maintain water quality and habitat diversity

Winter/spring freshes (1–5 freshes of up to 130–190 ML/day for 1–4 days in June– November)

  • Stimulate fish movement and maintain water quality 
  • Flush sediments from hard substrates to support waterbugs 
  • Wet higher benches to entrain organic debris and promote habitat diversity

Burnt Creek

Year-round low flows targeting upper Burnt Creek (1 ML/day or natural, year-round)1

  • Maintain edge habitats and shallow water habitat for waterbugs
  • Maintain inundation of the stream channel to protect riparian vegetation and prevent excessive streambed colonisation by terrestrial vegetation species
  • Maintain a sufficient area of pool habitat for native fish populations

Summer/autumn freshes targeting upper Burnt Creek (3 freshes of 30 ML/day for 2–7 days each in December–May)

  • Prevent the decline in water quality by flushing pools during low flows

Winter/spring freshes targeting upper Burnt Creek (1–5 freshes of 55 ML/day for 3–7 days in June–November)

  • Allow fish to move throughout the reach
  • Flush sediments from hard substrates to increase biofilm production and food for waterbugs
Winter/spring freshes targeting upper Burnt Creek (1–3 freshes of up to 160 ML/day for 1–3 days in June–November)
  • Disturb biofilms present on rocks or woody debris to stimulate new growth and provide food for waterbugs

Year-round fresh targeting lower Burnt Creek (1 fresh of 45 ML/day or natural for 2 days at any time)

  • Inundate riparian vegetation to maintain its condition and facilitate recruitment
  • Move organic debris in the channel to support waterbugs
  • Maintain the structural integrity of channels
Lower Burnt Creek bankfull (any time)3
  • Inundate riparian vegetation to maintain its condition and to facilitate recruitment 
  • Move organic debris in the channel to support waterbugs 
  • Maintain the structural integrity of the channel

Mount William Creek

Top-up of upper Mount William Creek pools

  • Maintain habitat for native fish and waterbugs

Year-round low flows targeting lower Mount William Creek (5 ML/day or natural, year-round) 1

  • Maintain edge habitats and shallow water habitat for waterbugs and endemic fish
  • Maintain near-permanent inundation of the stream channel for riparian vegetation and to prevent the growth of terrestrial plants in the streambed
Summer/autumn freshes targeting lower Mount William Creek (3 freshes of 20–30 ML/day for 2–7 days in December–May)
  • Prevent a decline in water quality by flushing pools during low flows
  • Provide variable flows during the low-flow season for waterbugs, for fish movement and to maintain water quality and diversity of habitat

Winter/spring freshes targeting lower Mount William Creek (1–5 freshes of up to 100 ML/day for 1–7 days in June–November)

  • Wet benches, move organic debris and promote habitat diversity
  • Flush surface sediments from hard substrates to support waterbugs
Winter/spring freshes targeting lower Mount William Creek (1–3 freshes of up to 500 ML/day for 1–3 days in June–November)
  • Wet the highest benches, entrain organic debris and promote habitat diversity

Bungalally Creek

Bankfull (any time)3
  • Inundate the riparian zone to maintain its condition and facilitate the recruitment of riparian vegetation communities 
  • Maintain the structural integrity of the channel and prevent the loss of channel capacity

Dock Lake

Partial fill (winter/spring)

  • Maintain and improve the diversity and abundance of wetland vegetation 
  • Support feeding and breeding habitat for waterbirds, frogs, waterbugs and turtles
The Ranch Billabong
Fill (winter/spring/summer)
  • Maintain and improve wetland vegetation diversity and abundance

1 Cease-to-flow events occur naturally in the Wimmera system and may be actively managed with deliveries of water for the environment to reduce stress on environmental values. In the most-recent flow 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 event.

2 Depending on catchment conditions, the timing of this fresh may vary to optimise environmental outcomes.

3 These actions will only occur if on-ground works have been completed to prevent third-party impacts potentially caused by bankfull events in these creeks.

Risk management

In preparing its seasonal watering proposal, Wimmera 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

Table 2 shows the partners and stakeholder organisations with which Wimmera CMA engaged when preparing the Wimmera system seasonal watering proposal. Other stakeholders and individuals are consulted throughout the year to help the Wimmera CMA implement the seasonal watering plan.

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 Wimmera Regional Catchment Strategy and the Wimmera Waterway Strategy.

Wimmera CMA holds its annual Environmental Water Management Forum, where community groups and agencies with an interest in water for the environment in the region provide feedback about the effectiveness of environmental watering, drought actions and other issues.

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

Partner and stakeholder engagement
  • Barengi Gadjin Land Council Aboriginal Corporation 
  • Commonwealth Environmental Water Holder 
  • Dimboola and Jeparit town committees 
  • Dimboola Fishing Classic, Wimmera Anglers' Association, Jeparit Anglers' Club, Native Fish Australia (Wimmera), Murtoa Angling Club, Dimboola Anglers' Club, Warracknabeal Angling Club, Mid-Northern Association of Angling Clubs and Horsham Fishing Competition Committee 
  • Dimboola Rowing Club, Horsham Triathlon Committee 
  • Friends of Bungalally Creek, Friends of Burnt Creek, Lake Lonsdale Action Group 
  • Glenelg Hopkins CMA 
  • GWMWater 
  • Hindmarsh Shire Council, Horsham Rural City Council, Northern Grampians Shire Council and Yarriambiack Shire Council 
  • Natimuk Field and Game 
  • Natimuk Lake Water Ski Club, Dimboola Water Ski Club, Hindmarsh Ski Club 
  • Parks Victoria 
  • Victorian Environmental Water Holder 
  • VRFish 
  • Victorian Fisheries Authority