Wimmera system

Barringgi Gadyin (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 River receives flows from several regulated tributaries including the MacKenzie River, Mount William Creek and Burnt Creek. These tributaries, and Bungalally Creek and the Wimmera River below Mount William Creek, can receive environmental flows. In exceptionally wet periods, Lake Hindmarsh will overflow into Outlet Creek and on to Lake Albacutya, which is an internationally recognised Ramsar-listed wetland. There are numerous wetlands beyond Lake Albacutya as well, which 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 that is harvested in the system headworks is used for towns and 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 some flows 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. During very dry years, flows entering Yarriambiack Creek may be blocked to ensure watering objectives in the Wimmera River are not compromised.

Two wetlands in the Wimmera system have been included in the environmental watering program in recent years.

Dock Lake, one of the Wimmera’s large terminal lakes near Horsham, would have naturally filled via spills from nearby Green Lake when there was significant runoff 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 completion of the Wimmera-Mallee pipeline in 2010. Water can be actively delivered to Dock Lake from Green Lake via a gravity-fed channel.

Ranch Billabong, near Dimboola, is located on land managed by 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.

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 as well as prevent colonisation of waterways by terrestrial plant species

Maintain and increase the resident platypus population 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

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

Increase the abundance and diversity of waterbugs, which break down dead organic matter and support the waterway’s food chain Maintain the crayfish population by providing feeding and breeding habitat

Maintain and improve 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 population of platypus 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 and western swamp crayfish and turtles as well as the critically endangered Wimmera bottlebrush. During dry periods, the middle and upper reaches of the MacKenzie River maintain regular flow (due to managed releases from Lake Wartook for urban supplies and environmental watering) and provide refuge for these populations.

Vegetation along Burnt and Bungalally creeks provide habitat corridors for terrestrial 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 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 it is wet, Dock Lake supports large populations of feeding and breeding 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 people and there are heritage values throughout the landscape. Native title is held along much of the lower Wimmera River, reinforcing the cultural significance of these values. In planning for environmental flows in the Wimmera River, the Barengi Gadjin Land Council and Wimmera CMA considered these values as well as opportunities to enhance contemporary cultural events (such as the Wotjobaluk festival).

Increasing the involvement of Traditional Owners in environmental water planning and management, and ultimately providing opportunities to progress towards self-determination within and beyond 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 (for example the Water Act 1989, the Victorian Aboriginal Affairs Framework, Water for Victoria (2016)) 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 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, and indicating progress towards this objective.

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

In the Wimmera system, Wimmera CMA and the Barengi Gadjin Land Council on behalf of the Wotjobaluk people work in partnership to provide Aboriginal environmental outcomes at Ranch Billabong. The delivery of water for the environment at Ranch Billabong aims to return a more natural flooding regime, restore indigenous plant and animal habitats, control selected weed species and improve the site’s amenity and suitability for gatherings and events (such as earth oven and bark canoe recreations).

Water for the environment has been delivered to Ranch Billabong consecutively for the last three years (2018, 2019, 2020). Notable ecological enhancements at the site include improved water quality and vegetation condition, consistent with the aspirations of the Traditional Owners. The Barengi Gadjin Land Council manages the site, and is controlling weed species and enhancing accessibility by building walking tracks and boardwalks. Following on from this work, Wimmera CMA and Barengi Gadjin Land Council will continue to work together to deliver environmental water.

Social, recreational and economic values and uses

In planning the potential watering actions in Table 1, 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; Dimboola [rowing] Regatta; 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 general visitation)
socio-economic benefits (such as improved water quality for consumptive water users including irrigation and stock and domestic users).

If the timing or management of planned environmental flows may be modified to align with a community benefit, this is acknowledged in Table 1 with an icon.

	Watering planned to support angling activities
	Watering planned to support water sports activities (e.g. rowing, 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.

Recent conditions

The Wimmera region had near-average rainfall, average temperatures but well-below average streamflow during 2020-21, continuing the very low streamflows experienced in the region since 2017. The Wimmera-Glenelg environmental entitlement received 57 percent allocation in 2020-21. The CEWH did not receive any allocation in the Wimmera system for the fourth year in a row, and carryover from previous years was exhausted in 2019-20.

Natural and passing flows delivered low flows and several freshes to the Wimmera River throughout winter and spring 2020. A large rainfall event in October 2020 caused flow in the Wimmera River at Horsham to peak at 636 ML per day and another event in late January–early February 2021 delivered a peak flow of 1,825 ML per day. The February event was the largest flow in the Wimmera River since 2016, and it washed a high load of organic material into the river, which caused a hypoxic blackwater event for parts of the river from near Horsham to Dimboola. Water for the environment was released from Taylors Lake during and after the event to help dilute the blackwater and prevent widespread fish deaths. Water for the environment was also used to meet recommended low-flow targets and deliver some additional freshes during summer and autumn.

Some of the planned passing flows from Lake Lonsdale were suspended in winter and spring 2020, and the accumulated water was used to protect refuge pools in lower Mount William Creek in December 2020.

Water for the environment was used to support environmental values in Ranch Billabong in winter 2021. The MacKenzie River and Burnt Creek had lower-than-average natural flow during winter and spring 2020, and water for the environment was delivered to these systems from late spring 2020 to help maintain aquatic habitat and refuge pools for native fish, crayfish and platypus.

Limited supply in the Wimmera-Glenelg environmental entitlement meant deliveries of water for the environment in the Wimmera system were managed in line with the drought climate scenario, even though local climatic conditions were closer to a dry scenario. All planned watering actions under the drought scenario were either fully or partially met in 2020-21 with a combination of environmental, unregulated and passing flows. Environmental monitoring in autumn 2021 detected an increased distribution of western swamp crayfish in the lower reaches of Burnt Creek. This finding may have implications for the future management of lower Burnt Creek.

Scope of environmental watering

Table 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 flows (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 five 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
Large winter/spring fresh(es) (one to three freshes of 200 ML/day for one to three days during June to November)	Wet lower benches, entrain organic debris and maintain habitat for waterbugs and fish
Summer/autumn low flows (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 five freshes of 70 ML/day for two to four 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)
Year-round low flows (10 ML/day or natural, year-round)	Maintain edge habitats and deeper pools and runs 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 pool habitat for native fish and crayfish populations Facilitate the dispersal of juvenile platypus downstream during autumn and winter
Small winter/spring fresh(es) (one to 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
Large winter/spring fresh (one fresh of 190 ML/day for one to two days during June to November)	Disturb biofilms on rocks or woody debris to stimulate new growth and provide food for waterbugs Maintain soil moisture for streamside vegetation Stimulate fish and platypus movement by increasing flow rates and water depth
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
Year-round low flows targeting upper Burnt Creek (1 ML/day or natural, year-round)	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
Small 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
Large winter/spring fresh(es) (one to three freshes of 160 ML/day for one to three days during June to November)	Disturb biofilms on rocks or woody debris to stimulate new growth and provide food for waterbugs Allow fish to move throughout the reach Inundate streamside vegetation to maintain plant condition and facilitate recruitment
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
Overbank fresh (one fresh of 90 ML/day for one day during August to November)	Inundate floodplain vegetation to maintain plant condition and facilitate recruitment Move organic debris from the floodplain to support waterbugs in the channel Maintain the structural integrity of the channel and floodplain
Small winter/spring fresh (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
Bungalally Creek
Bankfull (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 pools (winter/ spring and 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 variable flows 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 Improve water quality for frogs and waterbirds

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
Yarriambiack Creek Advisory Committee Friends of Bungalally and Burnt Creek Commonwealth Environmental Water Office Department of Environment, Land, Water and Planning – Grampians Region Glenelg Hopkins CMA Grampians Wimmera Mallee Water Hindmarsh Shire Council Horsham Rural City Council Northern Grampians Shire Council Parks Victoria Victorian Fisheries Authority Yarriambiack Shire Council Wimmera community members, especially landholders Natimuk and District Field and Game VRFish Natimuk Lake Water Ski Club Dimboola Water Ski Club Dimboola Fishing Classic Horsham Triathlon Committee Wimmera Anglers’ Association Dimboola Rowing Club Jeparit Anglers’ Club Hindmarsh Ski Club Horsham Fishing Competition Committee Canoeing Victoria Arthur Rylah Institute (Department of Environment, Land, Water and Planning) Barengi Gadjin Land Council

Partner and stakeholder engagement

Yarriambiack Creek Advisory Committee
Friends of Bungalally and Burnt Creek
Commonwealth Environmental Water Office
Department of Environment, Land, Water and Planning – Grampians Region
Glenelg Hopkins CMA
Grampians Wimmera Mallee Water
Hindmarsh Shire Council
Horsham Rural City Council
Northern Grampians Shire Council
Parks Victoria
Victorian Fisheries Authority
Yarriambiack Shire Council
Wimmera community members, especially landholders
Natimuk and District Field and Game
VRFish
Natimuk Lake Water Ski Club
Dimboola Water Ski Club
Dimboola Fishing Classic
Horsham Triathlon Committee
Wimmera Anglers’ Association
Dimboola Rowing Club
Jeparit Anglers’ Club
Hindmarsh Ski Club
Horsham Fishing Competition Committee
Canoeing Victoria
Arthur Rylah Institute (Department of Environment, Land, Water and Planning)
Barengi Gadjin Land Council

Page last updated: 22/07/21