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The Ovens system rises in the Great Dividing Range near Mount Hotham and flows about 150 km to join the River Murray in the backwaters of Lake Mulwala. Two small water storages have been constructed in the system: Lake Buffalo on the Buffalo River and Lake William Hovell on the King River. The regulated reaches of the Ovens system include the Buffalo River below Lake Buffalo, the King River below Lake William Hovell and the Ovens River from its confluence with the Buffalo River to the River Murray (as shown in Figure 1 below).

The Ovens system maintains quite good natural flows (particularly in winter-spring), compared to other regulated rivers. This is a result of relatively small storages that spill regularly and allow unregulated flows to the rivers.

The Ovens system contributes significantly to the water resources of the River Murray. The water that flows out of the Ovens River is regulated by the largest weir pool (Lake Mulwala) on the Murray regulated system. Ovens River flows contribute to the reliability and the variability of the flow regime for the River Murray and support many downstream uses including irrigation, urban supply and watering of iconic sites (such as Barmah Forest).

Environmental water is held in Lake Buffalo and in Lake William Hovell and can be released under regulated conditions when the storages are not spilling. Five reaches in the Ovens system can benefit from environmental water releases. While all are important, there are relatively small environmental holdings available in the system to meet the needs of all reaches. When water is only available from the holdings, outcomes in the reaches immediately downstream of the storages are targeted. When paired with consumptive water on its way to the Murray system, additional benefits are likely to be achieved downstream in the lower Ovens River.

Figure 1 The Ovens system

System map

Ovens
Grey river reaches have been included for context. The numbered reaches indicate where relevant environmental flow studies have been undertaken. Coloured reaches can receive environmental water.

Environmental watering objectives in the Ovens system

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Provide flows for native fish to move between pools and over rocky or shallow parts of the river
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Provide habitat for a wide range of waterbugs which provide energy, break down dead organic matter and support the river’s food chain
Landscape icon
Maintain the form of the river bank and channel plus a range of different river bed surfaces to support all stream life
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Maintain water quality for all river life
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Scour silt build-up and clean cobbles in river bed pools to maintain habitat for native plants and animals

Environmental values

The Ovens system supports a wide range of native fish species including the Murray cod, trout cod, golden perch and fly-specked hardyhead. The Buffalo River is important for large fish species during part of their breeding cycle while trout cod are found as far up the King River as Whitfield. The Ovens system has been the focus of a successful recovery project for trout cod, with efforts to reintroduce Macquarie perch underway.

Frogs (such as the giant bullfrog and growling grass frog) are abundant in the lower Ovens River and associated wetlands and in the King River upstream of Cheshunt. The lower wetlands support birds such as egrets, herons, cormorants, bitterns and treecreepers while the vegetation along the rivers is mostly river red gums and is among the healthiest examples in north-east Victoria.

Social and economic values

Recreational activities include fishing, boating, kayaking, waterskiing, swimming and bushwalking while irrigation supports the food and wine industries that attract many tourists to the region. The lower Ovens/ River Murray weir pool associated with Lake Mulwala is another tourist drawcard. There are also significant Aboriginal cultural heritage values with scar trees and artefact scatters as the physical evidence of Aboriginal people living along the river. The Ovens River continues to be a place of significance for Traditional Owners and their Nations in the region.

Conditions mid-2016

Some unregulated flows (natural streamflows that can't be captured in major reservoirs or storages) occurred in the Ovens system in winter and spring 2015. Climatic conditions continued the recent trend of the past four years of reduced rainfall: consequently, inflows to the storages were also very low. Releases from storage generally remained at low, stable levels during the irrigation season.

The releases from Lake William Hovell presented an opportunity to add some flow variability by releasing 50 megalitres (ML)  of water over two days in early April.

The bulk drawdown of water—a large release from Lake Buffalo to deliver consumptive water downstream and make additional space in the storage—did not occur due to the dry conditions in 2015–16. Consequently, 20 ML of water was released at the end of April to provide some variability downstream of the storage.

Scope of environmental watering

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

Potential environmental watering

Environmental objectives

Summer/autumn low-flow fresh in reach 5 (1 fresh of 130–260 ML/day for at least 3 days in April–May)

  • Maintain flow cues to stimulate movement of native fish
  • Maintain short-term fluctuations in discharge to move sediment and maintain waterbug habitat
  • Maintain connectivity between pools and riffles
  • Scour biofilm from river bed

Supporting variability1 of summer/autumn low flows targeting reaches 1, 2 and 3

  • Maintain natural connectivity between pools and riffles
  • Maintain short-term fluctuations in discharge to move sediment and maintain waterbug habitat

1 Operational releases from storage can vary, with environmental water used to provide some variability over one or two days.

Scenario planning

The climatic conditions and inflows into storages have a large effect on how environmental water is likely to be used. Under dry conditions, environmental water aims to provide low-flow variability below the storages.

As conditions become wetter, there are increased opportunities to piggyback environmental releases on the bulk drawdown of water from Lake Buffalo and achieve environmental outcomes for the length of the regulated river. Environmental water cannot be released if the storages are spilling and under wet conditions the additional risk of overbank flows may result in environmental water not being released at all. However, the desired flows through the Ovens system are likely to be achieved naturally under wet conditions. The Commonwealth environmental water holdings in the Ovens system have a high level of security and are expected to be available under all scenarios except for an extreme dry scenario, where perhaps rights to environmental water could be qualified and therefore not available for release.

Table 2 Potential environmental watering for the Ovens system under a range of planning scenarios

Planning scenario

Dry

Average

Wet

Expected river conditions

  • Possible winter/early spring unregulated flows
  • Highly likely low summer/autumn flows
  • Bulk water release unlikely
  • High winter/spring unregulated flows
  • Possible summer/autumn low flows
  • Bulk water release likely
  • High unregulated flows throughout most of the year
  • Bulk water release likely

Expected availability of environmental water

  • 50 ML Lake William Hovell
  • 20 ML Lake Buffalo
  • 70 ML total

Potential environmental watering

  • Summer/autumn low flows
  • Summer/autumn low-flow freshes
  • All objectives achieved naturally
  • Spill conditions and/or risk of overbank flows mean environmental water may not be released

Possible volume of environmental water required to meet objectives

  • 70 ML
  • 70 ML
  • 70 ML

Risk management

In preparing its seasonal watering proposal, North East Catchment Management Authority considered and assessed risks and identified mitigating strategies relating to the implementation of environmental watering. Risks and mitigating actions are continually reassessed by program partners throughout the water year.

Engagement

Waterway managers meet communities on environmental watering regionally, although other program partners also play a role.

In each region of Victoria, community engagement on environmental watering happens when environmental watering objectives and priorities are scoped (long term and annually), when delivering environmental water, and when reporting on environmental watering results.

Communities in the North East region are involved in decisions about the Ovens river system through the Ovens Environmental Water Management Plan.

Who is engaged and how

Recreational users

Recreational user groups (especially angling groups) provided advice and input to the development of the Ovens river Environmental Water Management Plan.

Environment groups

Environment groups (e.g. Landcare, Wangaratta Sustainability Group) provided advice and input to the development of the Ovens river Environmental Water Management Plan.

Members of the Wangaratta Sustainability Group support the North East Catchment Management Authority to communicate positive messages to the broader community about the benefits of environmental watering and healthy waterways.

Traditional Owners

The Dhudhuroa and Waywurru Nations were approached by Catchment Management Authority to provide input to the development of the Ovens River Environmental Water Management Plan process.

The Catchment Management Authority has an Indigenous engagement officer to assist with engagement of Traditional Owners on natural resource management.

The Dhudhuroa and Waywurru Nations are represented by the Murray Lower Darling Rivers Indigenous Nations. The Victorian Environmental Water Holder, the Commonwealth Environmental Water Office and the Murray Darling Basin Authority engage Murray Lower Darling Rivers Indigenous Nations on strategic (often longer term) issues related to environmental watering.

Councils

The Alpine Shire Council and the Rural City of Wangaratta provided advice and input to the development of the Ovens river Environmental Water Management Plan.

General public

The Catchment Management Authority communicates and engages with the general public on environmental watering via their website and media releases.