VEWH - Wimmera system

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 downstream of 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 onstream 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 but reduce the transfer of water for the environment 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. 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 and is now an ephemeral system. In late 2016, large-scale 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 (BGLC). The billabong system was disconnected from the Wimmera River by levees. These levees and river regulation in the Wimmera River have significantly altered the natural water regime of Ranch Billabong. Restoring habitat for native animals, fish 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

icon-objectives-fish

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 riparian vegetation

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

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

Aboriginal environmental outcomes

Watering is planned to be delivered in partnership with Traditional Owners and achieve Aboriginal environmental outcomes

Environmental values

The Wimmera system is home to many plant and animal species. It supports populations of native fish such as flatheaded gudgeon, obscure galaxias, river blackfish, southern pygmy perch and Australian smelt. Populations of the critically endangered Wimmera bottlebrush also occur along the MacKenzie River other locations near the Grampians.

The Wimmera River supports abundant native fish, waterbird, turtle, frog and rakali (water rats) 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 system and supports 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 consumptive supplies and environmental watering) 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 and southern pygmy perch.

Dock Lake is a natural wetland that was modified and used as part of the Wimmera-Mallee headworks system until 2010. When it is inundated, 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 gum trees, a variety of aquatic and amphibious plant species, ducks and frogs.

Recent conditions

The Wimmera region has experienced below-average rainfall for most of the last two years. Local rainfall in late winter 2018 generated modest run off in the eastern parts of the catchment, but western tributaries had very little to no flow throughout 2018–19 and no flow was recorded in the upper Wimmera River (measured at Glenorchy) for the first time since records began in the mid-1960s. Some unregulated flows in the Wimmera River’s eastern tributaries provided low flows in the lower Wimmera and MacKenzie river systems. Low volumes of passing flows that were available at Lake Lonsdale were suspended in winter and subsequently released during spring to meet Wimmera River flow objectives.

The dry conditions meant the VEWH only received a portion of allocation against its Wimmera-Glenelg environmental entitlement. As of March 2019, the VEWH had received 55 percent allocation for the year, but the total volume of available water for the environment was supplemented by system reserves that were carried over from 2017–18. The Commonwealth Environmental Water Holder (CEWH) did not receive any allocation in 2017–18 or 2018–19.

The water that was allocated to the CEWH in 2016–17 was carried over and used in the Wimmera system during 2018–19 to support environmental outcomes in the Wimmera River and Mount William Creek.

The modest inflows from tributaries during winter and deliveries of water for the environment have maintained and protected the condition of the rivers and creeks, despite the very dry conditions experienced in the Wimmera system during 2018–19. Fish monitoring conducted as part of the Victorian Environmental Flows Monitoring Assessment Program (VEFMAP) in autumn 2018 showed that populations of golden perch, freshwater catfish and small-bodied native fish have been maintained in all reaches of the Wimmera River that could receive water for the environment. In Mount William Creek, the continued improvement of both fringing and in-stream vegetation is supporting a stable population of small-bodied fish including obscure galaxias and flatheaded gudgeons. Platypus surveys in the MacKenzie River in April 2018 also showed the platypus population has grown and doubled its range within the river since 2016. However, the MacKenzie River platypus population remains small and lacks genetic diversity and potential translocations are being considered to boost its resilience.

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 4)
Summer/autumn low flows (15–30 ML/day or natural¹ in December to May)	Maintain in-stream habitat to support native fish populations and waterbugs Maintain near-permanent inundated stream channel for riparian vegetation and to prevent the growth of terrestrial plants in the stream bed
Winter/spring low flows (15–30 ML/day in June to November)	Provide flow variability to maintain access to habitat for native fish, waterbugs and in-stream vegetation
Summer/autumn freshes (1–3 freshes of 70 ML/day for two to seven days in December to 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 one to four days in June to November)	Increase water depth to provide stimulus for fish movement Provide flow variability to maintain water quality and diversity of fish habitats Wet lower benches, entraining organic debris and promoting habitat diversity for waterbugs
Winter/spring freshes (one to three freshes of 200 ML/day for one to three days during June to November)²	Provide variable flow for native fish movement Maintain water quality and habitat diversity by flushing surface sediments from hard substrates for macroinvertebrates
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 in the stream bed, and to support the growth of aquatic vegetation for fish habitat Maintain a sufficient area of pool habitat for native fish and crayfish populations Facilitate the annual dispersal of juvenile platypus into the Wimmera River
Summer/autumn freshes (three to four freshes of 5–50 ML/day for two to seven days each in December– May)	Provide variable flows in the low-flow season for fish movement Maintain water quality and habitat diversity for waterbugs
Winter/spring freshes (five freshes of 35–55 ML/ day for two to seven days in June–November)	Stimulate fish movement by increasing flow rates and water depth Maintain water quality Increase habitat availability and connectivity for aquatic species including in-stream and riparian vegetation, platypus, native fish and waterbugs
Winter/spring freshes (1–5 freshes of up to 130–190 ML/day for one to four days in June– November)	Stimulate fish movement and maintain water quality Flush sediments from hard substrates to support waterbugs Wet the higher benches to entrain organic debris and promote habitat diversity for aquatic species including in-stream and riparian vegetation, platypus, native fish and waterbugs
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 two to seven 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 three to seven 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 one to three 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 two days at any time)³	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
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 stream bed
Summer/autumn freshes targeting lower Mount William Creek (3 freshes of 20–30 ML/day for two to seven days in December–May)	Prevent a decline in water quality by flushing pools during low flows Provide variable flows and habitat diversity during the low-flow season for waterbugs, for fish movement and to maintain water quality
Winter/spring freshes targeting lower Mount William Creek (1–5 freshes of up to 100 ML/day for one to seven days in June–November)	Wet benches to entrain organic debris and promote habitat diversity for native fish Flush surface sediments from hard substrates to support waterbugs
Bungalally Creek
Bankfull (one fresh of 60 ML/day for two days at 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
Top-ups (winter/spring and summer/autumn)	Maintain and improve wetland vegetation diversity and abundance * Improve water quality for frogs and waterbirds

¹Cease-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 may be managed to conserve water for the environment allocation, and events ideally should be followed with a fresh.

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.

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
Friends of Bungalally and Burnt Creek Group Yarriambiack Creek Advisory Committee Parks Victoria Victorian Fisheries Authority Individual landholders Hindmarsh Shire Council Horsham Rural City Council Northern Grampians Shire Council Yarriambiack Shire Council Commonwealth Environmental Water Office Department of Environment, Land, Water and Planning Glenelg Hopkins Catchment Management Authority GWMWater Victorian Environmental Water Holder Canoeing Victoria Dimboola Fishing Classic Dimboola Rowing Club Dimboola Water Ski Club Hindmarsh Ski Club Horsham Fishing Competition Committee Horsham Triathlon Committee Jeparit Anglers’ Club Lake Lonsdale Action Group Natimuk Field and Game Club Natimuk Lake Water Ski Club VRFish Wimmera Anglers’ Association Barengi Gadjin Land Council Aboriginal Corporation

Partner and stakeholder engagement

Friends of Bungalally and Burnt Creek Group
Yarriambiack Creek Advisory Committee
Parks Victoria
Victorian Fisheries Authority
Individual landholders
Hindmarsh Shire Council
Horsham Rural City Council
Northern Grampians Shire Council
Yarriambiack Shire Council
Commonwealth Environmental Water Office
Department of Environment, Land, Water and Planning
Glenelg Hopkins Catchment Management Authority
GWMWater
Victorian Environmental Water Holder
Canoeing Victoria
Dimboola Fishing Classic
Dimboola Rowing Club
Dimboola Water Ski Club
Hindmarsh Ski Club
Horsham Fishing Competition Committee
Horsham Triathlon Committee
Jeparit Anglers’ Club
Lake Lonsdale Action Group
Natimuk Field and Game Club
Natimuk Lake Water Ski Club
VRFish
Wimmera Anglers’ Association
Barengi Gadjin Land Council Aboriginal Corporation

Page last updated: 12/12/19