Wimmera system

Barringgi Gadyin (Wimmera River) rises in the Pyrenees Ranges 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 River receives flows from several regulated tributaries, including the MacKenzie River, Mount William Creek and Burnt Creek (Figure 4.3.1). These tributaries – Bungalally Creek and the Wimmera River below Mount William Creek – can receive water for the environment. In exceptionally wet periods, Lake Hindmarsh will overflow into Outlet Creek and then to Lake Albacutya, an internationally recognised Ramsar-listed wetland. There are numerous wetlands beyond Lake Albacutya that have not filled with water for decades.

Water in the Wimmera system is stored in three on-stream reservoirs (Lake Wartook on the MacKenzie River, Lake Lonsdale on Mount William Creek and Lake Bellfield on Fyans Creek) and in several off-stream storages (Taylors Lake, Lake Fyans, and Toolondo Reservoir). A channel system enables water to be moved between several storages. Water can also be transferred from Rocklands Reservoir in the Glenelg system to the Wimmera system via the Rocklands-Toolondo Channel and from Moora Moora Reservoir via the Moora Channel. The connected storages and channels are collectively called the Wimmera-Mallee System Headworks. Water harvested in the system headworks is used for town, stock, and domestic supply throughout the Wimmera catchment and parts of the Avoca, Hopkins, Loddon, Glenelg, and Mallee catchments. Passing flows are provided to the Wimmera River and lower Mount William and Fyans creeks.

Priority reaches in the Wimmera system that can receive water for the environment are Wimmera River reaches 3 and 4, MacKenzie River reaches 2 and 3, upper and lower Mount William Creek, upper and lower Burnt Creek, and Bungalally Creek.

Yarriambiack Creek is a distributary of the upper Wimmera River that would have naturally received flow during high-flow events. Modifications to the Yarriambiack Creek offtake increase flow rates in Yarriambiack Creek compared to what would have naturally happened, but they reduce the flow rates to the high-priority reaches of the Wimmera River.

Two wetlands in the Wimmera system are also included in the environmental watering program.

Dock Lake, near Horsham, would have naturally filled via spills from nearby Green Lake when there was significant run-off from the northern edge of the Grampians. In the 1930s, Dock Lake was modified to allow it to be used as a water storage for irrigation supply in the Wimmera-Mallee system. Dock Lake was removed from the supply system after the Wimmera-Mallee Pipeline was completed in 2010. Water can be actively delivered to Dock Lake from Green Lake via a gravity-fed channel when there is sufficient water in Green Lake.

Ranch Billabong, near Dimboola, is located on land managed by the Barengi Gadjin Land Council Aboriginal Corporation. The billabong was disconnected from the Wimmera River by changes to a road that traverses land between the river and the billabong. Restoring elements of the natural water regime at Ranch Billabong aims to improve habitat for native animal and plant communities and is an important outcome for Traditional Owners and their Nations.

Proportion of water entitlements in the Wimmera system held by private users, water corporations and environmental water holders on 30 June 2020

System map

Environmental watering objectives in the Wimmera system

Protect and increase populations of native fish, including one of Victoria’s few self-sustaining populations of freshwater catfish

Maintain the frog population by providing feeding and breeding habitat

Maintain channel capacity and diversity and prevent the colonisation of waterways by terrestrial plant species

Increase the abundance and distribution of platypus populations by providing places to breed and feed, as well as opportunities for juveniles to disperse

Maintain the turtle population by providing feeding and breeding habitat

Improve the condition, abundance and diversity of aquatic, emergent and streamside vegetation

Maintain the waterbird population by providing roosting, feeding and breeding habitat in floodplain  wetlands.

Increase the abundance and diversity of waterbugs to break down dead organic matter and support the waterway’s food web.
 Maintain crayfish populations by providing feeding and breeding habitat

Maintain water quality to provide suitable conditions for waterbugs, native fish and other water-dependent plants and animals

Environmental values

The Wimmera River supports abundant native fish populations, including one of Victoria’s few self-sustaining populations of freshwater catfish. The Wimmera River also supports native waterbird, turtle, frog, and rakali (water rat) populations.

The MacKenzie River contains the only confirmed remaining platypus population in the Wimmera system and supports locally important populations of native fish, including river blackfish and southern pygmy perch. It also supports populations of threatened Glenelg spiny crayfish, western swamp crayfish, and turtles, as well as the critically endangered Wimmera bottlebrush. Managed releases from Lake Wartook for urban supplies and environmental flows maintain regular flow in the middle and upper reaches of the MacKenzie River and provide important refuges for these regionally important populations during dry periods.

Vegetation along Burnt and Bungalally creeks provides habitat corridors for terrestrial wildlife. Upper Burnt Creek contains an important native fish community and a threatened western swamp crayfish population, which is also becoming established in lower Burnt Creek. Mount William Creek supports regionally important populations of obscure galaxias, southern pygmy perch, and rakali (water rats).

Dock Lake is a natural wetland that was modified and used as part of the Wimmera-Mallee System Headworks until 2010. When wet, Dock Lake provides feeding and breeding habitat for large numbers of waterbirds and frogs.

Ranch Billabong is a small wetland near Dimboola that supports river red gums, a variety of aquatic plant species, waterbirds, and frogs.

Traditional Owner cultural values and uses

The Wimmera’s waterways are important to the Wotjobaluk Nations, and there are significant cultural values throughout the landscape. Native title is held along much of the lower Barringgi Gadyin (Wimmera River). In planning for environmental flows in Barringgi Gadyin (Wimmera River), the Barengi Gadjin Land Council and Wimmera CMA work together to support Wotjobaluk cultural values, including supporting contemporary cultural events (such as the Wotjobaluk festival).

Increasing the involvement of Traditional Owners in environmental water management and progressing opportunities towards self-determination in the environmental watering program is a core commitment of the VEWH and its agency partners. This is reinforced by a range of legislation and policy commitments, including the Water Act 1989, the Victorian Aboriginal Affairs Framework, the 2016 Water for Victoria, the Water is Life: Traditional Owner Access to Water Roadmap 2022, and in some cases, agreements under the Traditional Owner Settlement Act 2010.

Where Traditional Owners are more deeply involved in the planning and/or delivery of environmental flows for a particular site, their contribution is acknowledged in Table 4.3.1 with an icon. The use of this icon is not intended to indicate that these activities are meeting all the needs of Traditional Owners, but is incorporated in the spirit of valuing that contribution.

Watering planned and/or delivered in partnership with Traditional Owners to support Aboriginal cultural values and uses

In the Wimmera system, the Wimmera CMA and Barengi Gadjin Land Council work in partnership to support cultural values at Ranch Billabong. The delivery of water for the environment at Ranch Billabong aims to provide a more-natural flooding regime, restore indigenous plant species (such as old man weed and sneezeweed) and animal habitats, control selected weed species, and improve amenity and suitability for gatherings and events (such as earth oven and bark canoe cultural activities).

Water for the environment was delivered to Ranch Billabong in 2018, 2019, 2020, and 2021. In 2022, Ranch Billabong was filled naturally by flooding. Watering over the last five years has improved water quality and vegetation condition, consistent with the cultural objectives of the Traditional Owners. The Barengi Gadjin Land Council manages the site and has controlled weed species and enhanced accessibility by building walking tracks and culvert crossings around the billabong. In 2022, jetty construction commenced but was interrupted due to flooding.

Social, recreational and economic values and uses

In planning the potential environmental watering actions in Table 4.3.1, the Wimmera CMA considered how environmental flows could support values and uses, including:

Water-based recreation (such as canoeing, fishing, rowing, and water skiing)
Riverside recreation and amenity (such as birdwatching, cycling, running, and walking)
Community events and tourism such as fishing competitions at Dimboola, Jeparit, and Horsham; rowing at Dimboola; Kannamaroo Festival at Horsham, Wimmera River Duck Race; Wimmera River Park Run; Peter Taylor Memorial Barefoot Water Ski Tournament and Night Jump at Dimboola; and supporting small business, including chartered river cruises, pop-up food vendor caravans, and general visitation
Socioeconomic benefits such as for diverters for irrigation, stock needs, and domestic use: water levels and water quality, which can rely on the delivery of water for the environment, particularly in summer, and associated tourism events

If the timing or management of planned environmental flows may be modified to align with a community benefit, this is acknowledged in Table 4.3.1 with the following icons:

	Watering planned to support angling activities
	Watering planned to support water sports activities (e.g. canoeing, kayaking, rowing, swimming and water skiing)

Water for the environment can be used to temporarily raise water levels in the Horsham, Dimboola, and Jeparit weir pools to improve conditions for community events, including fishing competitions and water skiing and rowing events. Water for the environment held in the weir pools is released after the community events to support ecological objectives further downstream when required.

Scope of environmental watering

The term ‘environmental watering’ refers to the active delivery of held environmental water to support particular environmental objectives by altering the flow in a river or the water level in a wetland. While other terms are sometimes used to describe the delivery of environmental water, ‘environmental watering’ is deliberately used here and in seasonal watering statements to ensure consistency in the legal instruments that authorize the use of water for the environment in Victoria.

Table 4.3.1 describes the potential environmental watering actions in 2023-24, their expected watering effect (that is, the intended physical or biological effects of the watering action), and the longer-term environmental objectives they support. Each environmental objective relies on one or more potential environmental watering actions and their associated physical or biological effects.

Table 4.3.1 Potential environmental watering actions, expected watering effects, and associated environmental objectives for the Wimmera system

Potential environmental watering action	Expected watering effects	Environmental objective
Wimmera River (reach 4)
Winter/spring low flow (30 ML/day during June to November)	Maintain access to habitat for native fish, waterbugs and in-stream vegetation
Small winter/spring fresh(es) (one to five freshes of 70 ML/day for one to four days during June to November)	Increase water depth to provide a stimulus for fish movement Provide flow variability to maintain water quality and diversity of fish habitats
Medium winter/spring fresh(es) (one to three freshes of 200 ML/ day for one to three days during June to November)	Provide variable flow during the high-flow season for fish movement Provide flow variability to maintain water quality and diversity of fish habitats Wet lower benches to support native streamside vegetation, entrain organic debris and maintain habitat for waterbugs and fish
Summer/autumn low flow (15 ML/day or natural during December to May)	Maintain edge habitats in deeper pools and in-stream habitat to support native fish populations and waterbugs Maintain soil moisture for streamside vegetation and near-permanent inundated stream channel for aquatic vegetation and prevent the growth of terrestrial plants in the stream bed
Summer/autumn fresh(es) (one to three freshes of 70 ML/day for two to seven days during December to May)	Flush pools to prevent a decline in water quality and to maintain habitat for fish and waterbugs Provide fish passage to allow fish to move through the reach
MacKenzie River (reach 3)
Winter/spring low flow (10 ML/day or natural during June to November)	Maintain edge habitats and deeper pools and runs for waterbugs and platypus Maintain soil moisture for streamside vegetation and near-permanent inundated stream channel for aquatic vegetation and prevent the growth of terrestrial plants in the stream bed Maintain pool habitat for native fish and crayfish populations
Winter/spring freshes (five freshes of 35 ML/ day for two to seven days during June to November)	Stimulate fish movement by increasing flow rates and water depth and increase habitat availability for platypus and waterbugs Flush pools to prevent a decline in water quality Maintain soil moisture for streamside vegetation
Summer/autumn low flow (10 ML/day or natural during December to May)	Maintain edge habitats and deeper pools and runs for waterbugs and platypus Maintain soil moisture for streamside vegetation and near-permanent inundated stream channel for aquatic vegetation and prevent the growth of terrestrial plants in the stream bed Maintain pool habitat for native fish and crayfish populations
Summer/autumn freshes (three to four freshes of 35 ML/day for two to seven days each during December to May)	Flush pools to prevent a decline in water quality and to increase habitat availability for waterbugs and native fish
Upper Burnt Creek
Winter/spring low flow (1 ML/day or natural during June to November)	Maintain edge habitats and shallow-water habitat for waterbugs Maintain soil moisture for streamside vegetation and near-permanent inundated stream channel for aquatic vegetation and prevent the growth of terrestrial plants in the stream bed Maintain a sufficient area of pool habitat for native fish and crayfish populations
Winter/spring fresh(es) (one to five freshes of 55 ML/day for three to seven days during June to November)	Allow fish to move throughout the reach Flush sediments from hard substrates to increase biofilm production and food for waterbugs
Summer/autumn low flow (1 ML/day or natural during December to May)	Maintain edge habitats and shallow-water habitat for waterbugs Maintain soil moisture for streamside vegetation and near-permanent inundated stream channel for aquatic vegetation and prevent the growth of terrestrial plants in the stream bed Maintain a sufficient area of pool habitat for native fish and crayfish populations
Summer/autumn freshes (three freshes of 30 ML/ day for two to seven days each during December to May)	Prevent a decline in water quality by flushing pools in the low-flow season Allow fish to move throughout the reach Flush sediments from hard substrates to increase biofilm production and food for waterbugs
Lower Burnt Creek
Bankfull fresh (one fresh of 45 ML/day for two days at any time)	Inundate streamside vegetation to maintain plant condition and facilitate recruitment Move organic debris in the channel to support waterbugs Maintain the structural integrity of the channel
Bungalally Creek
Bankfull fresh (one fresh of 60 ML/day for two days at any time)	Inundate the streamside zone to maintain its condition and facilitate the recruitment of streamside vegetation communities Maintain the structural integrity of the channel and prevent the loss of channel capacity
Upper Mount William Creek
Top-up of pools (summer/autumn)	Maintain edge and shallow-water habitat for native fish and waterbugs Maintain water quality
Lower Mount William Creek
Year-round low flow (5 ML/day or natural)	Maintain edge habitats and shallow-water habitat for waterbugs and endemic fish Maintain soil moisture for streamside vegetation and near-permanent inundated stream channel for aquatic vegetation and prevent the growth of terrestrial plants in the stream bed
Winter/spring fresh(es) (one to five freshes of 100 ML/day for one to seven days during June to November)	Wet benches to entrain organic debris and allow native fish to move throughout the reach Flush surface sediments from hard substrates to support waterbugs Inundate the streamside zone to maintain its condition and facilitate the recruitment of streamside vegetation communities
Summer/autumn freshes (three freshes of 20-30 ML/day for two to seven days during December to May)	Prevent a decline in water quality by flushing pools during low flow Provide a variable flow and allow the movement of fish and waterbugs throughout the reach during the low-flow season
Dock Lake
Winter/spring partial fill	Trigger the growth and germination of wet-phase wetland vegetation communities Support feeding and breeding habitat for waterbirds, frogs, waterbugs and turtles
Ranch Billabong
Top-ups (winter/spring and summer/autumn)	Inundate wetland vegetation to maintain plant condition and facilitate recruitment mprove water quality for frogs and waterbirds

Page last updated: 01/07/22