VEWH - Wimmera system

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 River 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 below Mount William Creek can receive environmental flows. In exceptionally wet periods, Lake Hindmarsh may 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, and harvested water 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 to 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 when the nearby Green Lake filled and overflowed, due to high flow in small creeks that flow 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. In late 2016, flooding in the catchment partially filled Dock Lake when Green Lake filled and overflowed. Managed water deliveries can now only be delivered through a small channel from Green Lake, when there is enough water in Green Lake to gravity-feed Dock Lake.

Ranch Billabong, near Dimboola, is located on land managed by Barengi Gadjin Land Council Aboriginal Corporation. The billabong system was disconnected from the Wimmera River by changes to a road that traverses land between the river and the billabong. The roadworks and river regulation in the Wimmera River have significantly altered the natural water regime of Ranch Billabong. Restoring habitat for native animal and plant communities at Ranch Billabong is an important outcome for the environment, 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 system is home to many plant and animal species. It supports populations of native fish such as flat-headed gudgeon, obscure galaxias, river blackfish, southern pygmy perch and Australian smelt. Populations of the critically endangered Wimmera bottlebrush occur along the MacKenzie River and several other locations near the Grampians.

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

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 threatened Glenelg spiny crayfish and western swamp 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 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 and southern pygmy perch and rakali (water rats).

Dock Lake is a natural wetland that was modified and used as part of the Wimmera-Mallee headworks system until 2010. When it is wetted, Dock Lake supports large populations of feeding and breeding waterbirds. It also supports frogs and small-bodied native fish.

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 waterways within the Wimmera are important to the Wotjobaluk people and heritage values exist 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, Barengi Gadjin Land Council and Wimmera CMA have considered these values as well as contemporary cultural events such as the Wotjobaluk festival.

Waterway managers are seeking opportunities to increase the involvement of Traditional Owners in environmental water planning and management. 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.

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

In the Wimmera system, Wimmera CMA and Barengi Gadjin Land Council, on behalf of the Wotjobaluk people, work in partnership to provide a variety of Aboriginal environmental outcomes at Ranch Billabong. The delivery of environmental water 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.

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 fishing, rowing, water skiing and paddle boating)
riverside recreation and amenity (such as 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; Peter Taylor Memorial Barefoot Water Ski Tournament and Night Jump at Dimboola; and general visitation).

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 and Dimboola weir pools to improve conditions for community events including fishing competitions and water-skiing and rowing events. Following the events, the environmental water is released, to continue to improve ecological objectives downstream.

Recent conditions

The Wimmera region has had below-average rainfall and above-average temperatures for most of the last three years. Near-average rainfall in winter 2019 caused the upper Wimmera River (measured at Glenorchy) to flow for the first time in more than a year, and it contributed notable inflows into the Mount William Creek catchment including Lake Lonsdale. Much of spring and the first months of summer were drier than average, which meant inflows to storages across the Wimmera-Mallee headworks system were well below average for the 2019–20 water year, but the second half of summer and autumn were slightly wetter than average and mild temperatures limited evaporation losses. The Wimmera-Glenelg environmental entitlement received 42 percent allocation in 2019–20. The Commonwealth Environmental Water Holder (CEWH) did not receive any allocation in the Wimmera system for the third year in a row. CEWH water that was allocated in 2016–17 was carried over and used to support environmental outcomes in the Wimmera River and in Mount William Creek in 2018–19 and 2019–20.

Natural flow during winter and early spring 2019 provided low flow and some freshes which met some of the minimum environmental flow requirements in the Wimmera River, MacKenzie River and Burnt Creek. Passing flows from Lake Lonsdale were suspended in winter to conserve water for drier conditions predicted for spring and summer. The accumulated water was used to meet environmental flow requirements in the Wimmera River and in Mount William Creek in spring 2019.

Water for the environment was delivered from mid-October 2019 to June 2020, in line with very dry climate conditions to maintain low flow and small freshes in Wimmera River below Dimboola and to top up Ranch Billabong. Small volumes were also delivered to Mount William Creek, the MacKenzie River and upper Burnt Creek in line with drought conditions due to limited water availability in Lake Lonsdale and Lake Wartook. Environmental watering in summer and autumn 2020 primarily aimed to maintain habitat for native fish, platypus and waterbugs and to protect water quality. Without significant rain in winter and spring 2020, water quality and habitat quality in the Wimmera system will decline and there will be a greater reliance on water for the environment to protect critical refuges. There is less environmental water carried over from 2019–20 compared to the previous three years and under drought, very dry and dry seasonal conditions water availability in 2020–21 will be limited to only meeting the highest-priority demands (tier 1a) in the Wimmera system.

Scope of environmental watering

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

Potential environmental watering action	Functional watering objective	Environmental objective
Wimmera River (reach 2 & 3)
Winter/spring low flow (100 ML/day during June to November)	Provide fish passage to allow fish to move through the reach Maintain soil moisture for streamside vegetation and a near-permanent wetted stream channel for aquatic vegetation Prevent the growth of terrestrial plants in the stream bed
Wimmera River (reach 4)
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 wetted stream channel for aquatic vegetation and to prevent the growth of terrestrial plants in the stream bed
Winter/spring low flow (30 ML/day during June to November)	Maintain access to habitat for native fish, waterbugs and in-stream vegetation
Winter/spring low flow (30 ML/day during June to November)	Maintain access to habitat for native fish, waterbugs and in-stream vegetation Maintain water quality and habitat diversity by flushing surface sediments from hard substrates for macroinvertebrates
Summer/autumn fresh (one to five freshes of 70 ML/day for one to four days during December to May)	Flush pools to prevent decline of water quality and maintain habitat for fish and waterbugs Provide fish passage to allow fish to move through the reach
Small winter/spring fresh (one to three freshes of 70 ML/day for one to five days during June to November)	Increase water depth to provide stimulus for fish movement Provide flow variability to maintain water quality and diversity of fish habitats
Large winter/spring fresh (one to three freshes of 200 ML/day for one to three days during June to November)	Wet lower benches, entrain organic debris and increase habitat availability for waterbugs and fish
MacKenzie River (reach 2)
Summer/autumn low flow (two ML/day or natural during December to May)	Maintain edge habitats and deeper pools and runs for waterbugs, platypus and fish Maintain soil moisture for streamside vegetation and a near-permanent wetted stream channel for aquatic vegetation Prevent the growth of terrestrial plants in the stream bed
Winter/spring low flow (27 ML/day or natural during June to November)	Facilitate the annual dispersal of juvenile platypus into the Wimmera River
Summer/autumn fresh (two to four freshes of five to 50 ML/day for two to seven days during December to May)	Provide variable flows in the low-flow season for fish movement Maintain water quality and increase habitat availability for waterbugs and platypus
Winter/spring fresh (five freshes of 55 ML/day for two to seven days during June to November)	Stimulate and facilitate fish and platypus movement by increasing flow rates and water depth Maintain water quality and improve habitat quality for waterbugs Maintain soil moisture for streamside vegetation and a near-permanent wetted stream channel for aquatic vegetation Prevent the growth of terrestrial plants in the stream bed
MacKenzie River (reach 3)
Year-round low flow (10 ML/ day or natural, year-round)	Maintain edge habitats and deeper pools and runs for waterbugs Maintain soil moisture for streamside vegetation and a near-permanent wetted stream channel for aquatic vegetation 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 into the Wimmera River during autumn/winter
Summer/autumn freshes (three to four freshes of 35 ML/day for two to seven days each during December to May)	Provide variable flows in the low-flow season for fish movement Maintain water quality and increase habitat availability for waterbugs
Small winter/spring fresh (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 Maintain water quality Maintain soil moisture for streamside vegetation and a near-permanent wetted stream channel for aquatic vegetation
Large winter/spring fresh (one fresh of 190 ML/day for one to two days during June to November)	Disturb biofilms present on rocks or woody debris, to stimulate new growth and provide food for waterbugs Maintain water quality Maintain soil moisture for streamside vegetation and a near-permanent wetted stream channel for aquatic vegetation Stimulate fish movement by increasing flow rates and water depth and increase habitat availability for platypus
Upper Burnt Creek
Year-round low flow (one ML/day or natural, year- round)	Maintain edge habitats and shallow-water habitat for waterbugs Maintain soil moisture for streamside vegetation and near-permanent wetted stream channel for aquatic vegetation and to 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 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
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
Large winter/spring fresh (one to three freshes of 160 ML/day for one to three days during June to November)	Disturb biofilms present on rocks or woody debris, to stimulate new growth and provide food for waterbugs Allow fish to move throughout the reach Wet streamside vegetation to maintain plant condition and facilitate recruitment
Lower Burnt Creek
Bankfull fresh (one fresh of 45 ML/day for two days at any time)	Wet 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)	Wet floodplain vegetation to maintain plant condition and facilitate recruitment Move organic debris from the floodplain to support waterbugs in channel Maintain the structural integrity of the floodplain
Bungalally Creek
Bankfull (one fresh of 60 ML/day for two days at any time)	Wet 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 habitat for native fish and waterbugs Maintain water quality Trigger native fish spawning
Lower Mount William Creek
Year-round low flow (five 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 wetted stream channel for aquatic vegetation and to prevent the growth of terrestrial plants in the stream bed
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 increase habitat availability during the low-flow season for waterbugs and fish
Winter/spring fresh (one to five freshes of 100 ML/ day for one to seven days during June to November)	Wet benches to entrain organic debris and increase habitat availability for native fish Flush surface sediments from hard substrates to support waterbugs Wet the streamside zone to maintain its condition and facilitate the recruitment of streamside vegetation communities
Dock Lake
Winter/spring partial fill	Maintain and improve the diversity and abundance of wetland vegetation Support feeding and breeding habitat for waterbirds, frogs, waterbugs and turtles
Ranch Billabong
Top-ups (winter/spring and summer/autumn)	Maintain and improve wetland vegetation diversity and abundance 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: 22/01/21