Ovens system

The Ovens River rises in the steep, forested mountains of the Great Dividing Range near Mount Hotham and flows about 150 km to join the Murray River in the backwaters of Lake Mulwala (Figure 5.3.1). The system has two small water storages: Lake Buffalo on the Buffalo River and Lake William Hovell on the King River. The regulated reaches of the Ovens system include the Buffalo and King rivers below these storages and the Ovens River from its confluence with the Buffalo River to the Murray River.

As its storages are quite small and spill regularly, the Ovens system maintains a large proportion of its natural flow regime, particularly in winter/spring. However, the storages and licensed water extractions throughout the system can restrict flow during low-flow periods, and parts of the system can become quite flow-stressed during summer and autumn.

The Ovens River flows into Lake Mulwala on the Murray River, the largest weir pool on the Murray regulated system. Ovens River flows contribute to the reliability and variability of flows in the Murray River and support many downstream uses, including irrigation, urban supply and watering of iconic floodplain sites (such as Barmah Forest).

Water for the environment is held in Lake Buffalo and Lake William Hovell and can be released when the storages are not spilling. Five reaches in the Ovens system can benefit from releases of water for the environment. While all are important, there is a relatively small volume (123 ML) of water available, and it is insufficient to meet most of the environmental flow objectives. The available water is used selectively to deliver the greatest possible environmental benefit. Water for the environment is most commonly used in the Ovens system to deliver critical flow events in reaches immediately below the two main storages, or it is used in conjunction with operational water releases to influence flow in the lower Ovens River. It is also used to top up Mullinmur Wetland in Wangaratta.

Ovens pie chart

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

System map

Environmental watering objectives in the Ovens system

Maintain the size and distribution of native fish populations

Maintain the form of the riverbank and channel and ensure river bed surfaces are in suitable condition to support all stream life

Maintain the condition and extent of wetland vegetation communities

Maintain an adequate abundance and diversity of waterbugs to support river food webs and associated ecosystem processes

Maintain water quality for all river life

Environmental values

The diverse aquatic habitat and abundant food resources associated with the Ovens system support a wide range of native fish species, including Murray cod, trout cod, golden perch and unspecked hardyhead. The Buffalo River provides valuable habitat for large-bodied fish species during part of their breeding cycle, while trout cod have a large range within the system and are found as far up the King River as Whitfield. A project to recover trout cod populations in the Ovens system has been successful, and efforts to reintroduce Macquarie perch are continuing.

Frogs (such as the giant banjo frog and growling grass frog) are abundant in the lower reaches and associated wetlands of the Ovens River and the King River above Cheshunt. The lower Ovens wetland complex contains over 1,800 wetlands, is listed as nationally significant and is home to a variety of waterbirds, including egrets, herons, cormorants and bitterns. The streamside zones of river channels throughout the Ovens system support some of Victoria’s healthiest river red gum forests and woodlands, while the wetlands support a variety of aquatic and semi-aquatic vegetation communities.

Water for the environment was delivered to Mullinmur Wetland at Wangaratta for the first time in 2019-20. This site has been the focus of several environmental improvement projects in recent years. Specific management actions include carp removal, a revegetation program and the re-introduction of native fish.

Recent conditions

The Ovens catchment experienced above-average rainfall and average temperatures throughout 2021-22 as a La Niña event continued to influence climate conditions across eastern Australia. Inflows to Lake William Hovell were passed through the storage during winter and spring and were 144 percent of the long-term average for 2021-22. Inflows to Lake Buffalo were also passed through the storage during winter and spring and were 179 percent of the annual average for 2021-22. Periods of high rainfall in both catchments during spring and summer caused storage spills and provided natural freshes to the Buffalo and King rivers. Both storages opened the season at 100 percent allocations against environmental water shares. The Ovens River and reaches of the King and Buffalo rivers directly below their storages retained much of their natural flow variability throughout the year, with the flow at Wangaratta peaking above 16,000 ML per day (which is above the minor flood level) on three occasions during winter and spring.

Deliveries of water for the environment for the Ovens system were managed in line with an average scenario in 2021-22, and all planned watering actions were met through natural flows or water for the environment. Mullinmur Wetland was naturally connected to the Ovens River on multiple occasions throughout winter and spring 2021, and a planned top-up using water for the environment was not required. Held water for the environment was combined with allocations transferred from the Taungurung Land and Water Council and water donated by a private landholder to boost the low flow in the King River during February. A planned autumn fresh in reach 1 of the Buffalo River could not be delivered due to maintenance work, but the impact was likely minimal due to the significant flow variability in the natural flow during the year.

Fish surveys conducted by the Arthur Rylah Institute over the past two years have recorded Macquarie perch, trout cod and southern pygmy perch in the middle reaches of the King River and movement of golden perch into Mullinmur Wetland when it is connected to the Ovens River. Native freshwater catfish that were introduced to Mullinmur Wetland in 2019 have not been detected in follow-up surveys: they have presumably moved into the Ovens River during periods of natural connection.

Traditional Owner cultural values and uses

North East CMA consulted the Taungurung Land and Waters Council and the Yorta Yorta Nation Aboriginal Corporation in planning for potential 2022-23 environmental flows in the Ovens system.

The Taungurung Land and Waters Council water knowledge group Baan Ganalina (Guardians of Water) supports increasing Taungurung influence in water management, building internal capacity and advancing Taungurung water rights.

The Taungurung Country Plan’s water chapter Baan Dhumba-Dji-Ngan Mundak Gunga (We must speak to protect water) lists several water objectives. These include increasing and strengthening Taungurung voices, increasing water literacy and capacity, and returning water to disconnected wetlands. The future delivery of water for the environment by the Taungurung Land and Waters Council on Taungurung Country would contribute to achieving some of these objectives.

The Taungurung Land and Waters Council has a 39 ML entitlement in Lake William Hovell and has transferred unused portions of its annual allocation to the VEWH each year (2019-22) to support environmental flows in the King River to help meet the council’s watering objectives and Taungurung cultural responsibilities to heal and care for Country.

The Yorta Yorta Nation Aboriginal Corporation has developed the Yorta Yorta Whole-Of-Country Plan 2021-2030, which outlines aspirations and directions for Yorta Yorta Country. The plan identifies the lower Ovens River as a very high priority for management actions. The plan will support more culturally informed planning for water in the lower Ovens River in the future.

North East CMA has started conversations with the Bangerang Aboriginal Corporation, which has expressed aspirations for Mullinmur Wetland. Bangerang Aboriginal Corporation is exploring a cultural burning trial at the site as well as mapping scar trees and traditional stories in partnership with the Rural City of Wangaratta.

Increasing the involvement of Traditional Owners in the planning and management of environmental flows and ultimately providing opportunities to progress towards self-determination within the environmental watering program is a core commitment of the VEWH and its agency partners. This is reinforced by a range of legislative and policy commitments, including the Water Act 1989, the Victorian Aboriginal Affairs Framework, the 2016 Water for Victoria 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 5.3.1 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 their contribution and indicating progress towards deeper involvement.

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

The Taungurung Land and Waters Council may consider using their water entitlement in the King River system to support environmental objectives as part of their goal of healing and caring for Country. The Taungurung Land and Waters Council’s allocation has been released from Lake William Hovell four times as an environmental flow in partnership with the North East CMA, Goulburn-Murray Water and the VEWH to provide additional water to the King River and assist in healing Country.

Social, recreational and economic values and uses

In planning the potential watering actions in Table 5.3.1, North East CMA considered how environmental flows could support values and uses, including:

water-based recreation (such as boating and fishing)
riverside recreation and amenity (such as camping, visitation for mental/physical health and wellbeing)
community events and tourism (such as providing a setting for community gatherings, outdoor school learning, sporting events and citizen science projects)
socio-economic benefits (such as businesses used by anglers and stock and domestic uses which rely on water quality supported by water for the environment deliveries when natural flows are at their lowest from November to March).

A private landholder’s water allocation of 56 ML from the King River system was transferred to the VEWH as a donation. This release was combined with an entitlement to water for the environment and the Taungurung Land and Waters Council contribution to provide an increase in flow in February 2022.

Environmental flows are planned for Mullinmur Wetland over summer to support aquatic vegetation and support a native catfish nursery at the site. The water is expected to support other benefits for the local community at this site, which is managed by the Catholic Education Department supported by Wangaratta Landcare and Sustainability Incorporated. A new education hub provides a space for environmental education for students from Galen Catholic College, young people attending the Borinya Wangaratta Community Partnership and other members of the local community, including a team of Waterwatch citizen scientists. These volunteers have been involved in monitoring changes in conditions for plant and fish species after deliveries of water for the environment.

Scope of environmental watering

Table 5.3.1 describes the potential environmental watering actions in 2022-23, their expected watering effects (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 5.3.1 Potential environmental watering actions, expected watering effects and associated environmental objectives for the Ovens system

Potential environmental watering action	Expected watering effects	Environmental objective
Mullinmur Wetland (top up during November to February)	Maintain the water level within the wetland to support the growth and recruitment of aquatic vegetation Maintain habitat for native fish
Autumn fresh (one fresh of greater than 430 ML/day for three days in reaches 1 and 4 and greater than 130- 260 ML/day for three days in reach 5 during March to April)	Provide flow cues to stimulate the movement of native fish Increase connectivity between pools for fish movement Mix pools to improve the water quality Provide small variations in river levels and velocity, to flush sediment from hard substrates and maintain waterbug habitat Scour biofilm from the river bed
Summer/autumn low-flow variability (greater than 80 ML/day for one to two days during February to March in reaches 1, 2 and 3)	Increase connectivity between pools for fish movement Provide small variations in river levels to move sediment and maintain waterbug habitat Maintain sufficient oxygen levels

Potential environmental
watering action

Expected watering effects

Environmental objective

Mullinmur Wetland (top up during November to February)

Maintain the water level within the wetland to support the growth and recruitment of aquatic vegetation
Maintain habitat for native fish

Autumn fresh (one fresh of greater than 430 ML/day for three days in reaches 1 and 4 and greater than 130- 260 ML/day for three days in reach 5 during March to April)

Provide flow cues to stimulate the movement of native fish
Increase connectivity between pools for fish movement
Mix pools to improve the water quality
Provide small variations in river levels and velocity, to flush sediment from hard substrates and maintain waterbug habitat
Scour biofilm from the river bed

Summer/autumn low-flow variability (greater than 80 ML/day for one to two days during February to March in reaches 1, 2 and 3)

Increase connectivity between pools for fish movement
Provide small variations in river levels to move sediment and maintain waterbug habitat
Maintain sufficient oxygen levels

Scenario planning

Table 5.3.2 outlines potential environmental watering and expected water use under a range of planning scenarios.

The weather and inflows into storages have a large effect on how water for the environment is likely to be used in the Ovens system. Under dry and average conditions, the highest priority will be to use available water for the environment to introduce some variability to the summer/autumn low flow to limit the duration of extremely low-flow or cease-to-flow events that can stress native fish and waterbugs. Under average and wet conditions, the objective will be to provide a greater flow, support fish movement and breeding and increase the abundance and diversity of waterbugs. There is not enough water for the environment to deliver the recommended autumn fresh in full, so releases of water for the environment will need to be timed to coincide with operational water releases. All the recommended environmental flows for the Ovens River system are expected to be met naturally under a wet climate scenario.

The main priority for Mullinmur Wetland in 2022-23 will be to provide top-ups throughout the warmer months to offset seepage and evaporation, maintain wetland vegetation and maintain habitat for native fish. This will likely require some active deliveries of water for the environment under drought and dry climate scenarios, but it may be met by natural connections to the Ovens River under average and wet climate scenarios.

Planning scenario table

Table 5.3.2 Potential environmental watering for the Ovens system under a range of planning scenarios

Planning scenario	Drought	Dry	Average	Wet
Expected river conditions	Possible winter/ early-spring natural fresh Very low flow through summer and autumn No bulk water release	Possible winter/ early-spring natural fresh Very low flow through summer and autumn Bulk water release is unlikely	High winter/spring natural freshes Moderate flow in summer and autumn with occasional natural freshes Bulk water release is likely	High natural freshes and low flow throughout most of the year Bulk water release is likely All flow objectives are achieved naturally
Expected availability of water for the environment	123 ML
Potential environmental watering – tier 1 (high priorities)	Tier 1a (can be achieved with predicted supply)
Potential environmental watering – tier 1 (high priorities)	Summer/autumn low flow variability Mullinmur Wetland top-up	Summer/autumn low flow variability Mullinmur Wetland top-up	Autumn fresh Summer/autumn low flow variability Mullinmur Wetland top-up	Autumn fresh Summer/autumn low flow variability Mullinmur Wetland top-up
Possible volume of water for the environment required to achieve objectives	123 ML	123 ML	123 ML	0 ML

Engagement

Table 2 shows the partners with which North East CMA engaged when preparing the Ovens system seasonal watering proposal.

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 North East Regional Catchment Strategy and North East Waterway Strategy.

Table 2 Partners engaged in developing the Ovens system seasonal watering proposal

Partner engagement
Wangaratta Landcare and Sustainability Incorporated Commonwealth Environmental Water Office Goulburn-Murray Water City of Wangaratta Victorian Fisheries Authority Catholic Education Department – Sandhurst Diocese Arthur Rylah Institute (Department of Environment, Land, Water and Planning) Yorta Yorta Nation Aboriginal Corporation Taungurung Land & Waters Council

Page last updated: 01/07/22