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Lake Nillahcootie has a storage capacity that is about half the mean annual flow of its upstream catchment, so it fills in most years. The operation of Lake Nillahcootie has modified the river’s natural flow pattern: winter/spring flow is less than natural because a large proportion of inflow is harvested, while summer/autumn flow is greater than natural because water is released to meet downstream irrigation demands. These impacts are most pronounced in the reach between Lake Nillahcootie and Hollands Creek. Below Hollands Creek, the river retains a more natural flow pattern due to flows from unregulated tributaries, although total annual flow is considerably less than natural. The catchment has been extensively cleared for agriculture, including dryland farming (such as livestock grazing and cereal cropping) and irrigated agriculture (such as dairy, fruit and livestock).

Water is released from Lake Nillahcootie to meet downstream demand and minimum-flow requirements specified under the bulk entitlement for the Broken River system. Releases from storage may be less than 30 ML per day as tributary inflows immediately below the storage (such as from Back Creek) can supply much of minimum-flow requirements specified in the bulk entitlement.

Upper Broken Creek is defined as the 89-km stretch of creek from the Broken River (at Caseys Weir) to the confluence with Boosey Creek near Katamatite. Upper Broken Creek flows across a flat, riverine plain and has naturally low run-off from its local catchment. It receives flood flows from the Broken River, although the frequency of these floods has been reduced by river regulation, earthworks and road construction.

Upper Broken Creek has been regulated for more than a century. Before 2007, water was diverted into upper Broken Creek at Casey’s Weir to meet local demand, but recent water savings projects have reduced the demand on the creek. There is now low flow throughout the year between Caseys Weir and Waggarandall Weir. The flow below Waggarandall Weir is mainly influenced by rainfall and catchment run-off. These changes have reduced the amount of permanent aquatic habitat.

Delivery of water for the environment to the Broken River is primarily constrained by the small volume of water holdings in the Broken system. Environmental water holders can trade water into the Broken system from other trading zones subject to relevant limits and conditions to meet critical environmental needs.

The bulk entitlement for the Broken system held by Goulburn-Murray Water stipulates that minimum environmental flows — also known as passing flows — are to be maintained in the Broken River when there are natural flows into the system. The bulk entitlement also allows Goulburn-Murray Water and the VEWH to agree to reduce minimum passing flows and accumulate the unused volumes for later releases that will provide a greater environmental benefit. In recent years, passing

flows have been reduced, accumulated and delivered to maintain low flow (on days when there are no passing flows due to no natural flow into the system) and freshes in the Broken River. Accumulated passing flows are the first volumes lost when the storage spills. Environmental flows in upper Broken Creek are restricted by the volume of available supply, channel capacity and the need to avoid flooding low-lying, adjacent land.

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

Traditional Owners
Storage manager
Environmental water holder

System map

Environmental watering objectives in the Upper Broken Creek

Fish icon
Maintain native fish populations
Landscape icon
Turn over bed sediments and scour around large wood to maintain in-channel habitat diversity
Platypus icon
Maintain platypus populations
Plant icon
Maintain in-stream vegetation
Insect icon
Maintain a wide range and high biomass of waterbugs to break down dead organic matter and support the river’s food web
Water icon
Maintain water quality

Environmental values

The Broken River retains one of the best examples of healthy in-stream vegetation in a lowland river in the region. A range of native submerged and emergent plant species, including eelgrass, common reed and water ribbons, populate the bed and margins of the river. These plants provide habitat for a range of animals, including small- and large-bodied native fish. Murray cod, Macquarie perch, golden perch, silver perch, river blackfish, mountain galaxias, southern pygmy perch and Murray- Darling rainbowfish all occur in the Broken River. The river also supports a large platypus population.

Upper Broken Creek is dominated by unique box streamside vegetation and remnant plains grassy woodland. The creek and its streamside zone support numerous threatened species, including brolga, Australasian bittern, buloke and rigid water- milfoil. Much of the high-quality native vegetation in the region is set aside as a natural features reserve. Upper Broken Creek supports a variety of native fish species, including carp gudgeon, Murray cod, golden perch and Murray-Darling rainbowfish, as well as platypus and common long-necked turtle.

Both the Broken River and upper Broken Creek are listed in the Directory of Important Wetlands in Australia.

Recent conditions

Rainfall across the Broken River catchment during 2021-22 was slightly above the long-term average, and January rainfall was the highest recorded since 2011. Lake Nillahcootie filled and spilled in August 2021, and the lake remained at full capacity until mid-November. Several natural freshes ranging from 500 ML per day to 3,500 ML per day occurred in the Broken River between July and February, and a bankfull flow of 5,000 ML per day occurred in early September. Upper Broken Creek also had two natural overbank flow events in late January. Allocations against high- and low-reliability water shares in the Broken system reached 100 percent by September and October, respectively. About 2.6 GL of water for the environment from VEWH and CEWH entitlements in the Goulburn was traded into the Broken system to meet demands in upper Broken Creek and Moodie Swamp: subsection 5.5.3 Broken wetlands has more information about this.

Deliveries of water for the environment for the Broken system were managed in line with an average climate scenario during 2021-22. Planned watering actions for Broken River were largely met by natural flow and operational releases, while planned watering actions for upper Broken Creek were only partially met. Water for the environment was used to help meet low flow requirements in upper Broken Creek during summer and autumn and to deliver a fresh to try to minimise the impact of a hypoxic blackwater event that was caused by the January overbank flow. The fresh helped to improve oxygen levels in upper Broken Creek, but not before some fish died (mainly European carp and a small number of Murray cod).

Traditional Owner cultural values and uses

Traditional Owners value implementing more natural flow regimes in the landscape’s waterways and wetlands as a way of caring for Country, supporting culturally important plants and providing opportunities to practise culture.

Goulburn Broken CMA consulted with the Yorta Yorta Nation Aboriginal Corporation for upper Broken Creek and the Broken River downstream of Benalla and the Taungurung Land and Waters Council for the Broken River upstream of Benalla.

The Taungurung Land and Waters Council plan to assess cultural values and objectives for the Broken River through healthy Country assessments like Aboriginal Waterway Assessments. These will assist the Taungurung Land and Waters Council in identifying more specific cultural objectives for the system in future. The Taungurung Land and Waters Council has been part of the Broken system advisory group meetings since 2018 and is continuing to work with Goulburn Broken CMA to identify cultural objectives and develop culturally informed recommendations for water for the environment in the Broken system. Water for the environment in the Broken system supports the health of cultural values and landscapes, including intangible cultural heritage, valued species and traditional food and medicine plants.

The Yorta Yorta Nation Aboriginal Corporation has provided the following statement about the cultural values of the Broken River and upper Broken Creek:

“The Broken River (and upper Broken Creek) hold many cultural values. Common reed contained within the slack water provides important material for tools while also providing refuge for culturally important fish species (large- and small- bodied). The river also has significant stands of old-growth river red gum containing important habitat and exhibiting scars made from carving out canoes and coolamons.”

Social, recreational and economic values and uses

In planning the potential watering actions in Table 5.5.1, Goulburn Broken CMA considered how environmental flows could support values and uses, including:

  • water-based recreation (such as canoeing, fishing, kayaking and swimming)
  • riverside recreation (such as birdwatching, bushwalking, camping, duck hunting and picnicking)
  • amenity: green and blue spaces are important to the community for wellbeing and mental health due to the otherwise dry environment
  • community events and tourism (such as markets around Benalla Lake)
  • socio-economic benefits (such as maintaining the volume of water in the lower sections to optimise the efficiency of deliveries of consumptive water, maintain water quality for irrigation, stock and domestic use and support terrestrial birds that help control agricultural pests).

Scope of environmental planning

Table 5.5.1 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 objective(s) they support. Each environmental objective relies on one or more potential environmental watering actions and their associated physical or biological effects.

Table 5.5.1 Potential environmental watering actions, expected watering effects and associated environmental objectives for the Broken River and upper Broken Creek

Potential environmental watering action

Expected watering effects

Environmental objectives

Upper Broken Creek (reach 1)

Winter low flow (1-10 ML/day during June to August)

  • Maintain aquatic habitat and connections between weir pools for native fish and platypus
  • Inundate benthic surfaces and large wood located at the bottom of the channel, which serves as habitat for waterbugs
  • Maintain water quality and oxygen levels for native fish, platypus and waterbugs
Fish iconPlatypus iconInsect iconDrop icon

Spring low flow (1-10 ML/ day during September to November)

Summer low flow (1-5 ML/day during December to February)

Autumn low flow (1-5 ML/day during March to May)

Summer/autumn fresh (one fresh of 50-100 ML/ day for 10 days during December to May)

  • Flush pools to improve their water quality and increase oxygen levels
Drop icon
Broken River (reach 1, 2 and 3)

Winter low flow (15-30 ML/day during June to August)

  • Maintain habitat for in-stream and fringing vegetation, and prevent terrestrial vegetation from colonising the stream bed
  • Maintain riffles, pools and slackwater to provide diverse hydraulic habitat for native fish, aquatic plants, platypus and waterbugs
  • Maintain water quality and oxygen levels for native fish, platypus and waterbugs
Fish iconPlatypus iconPlant iconInsect iconDrop icon

Spring low flow (15- 30 ML/day during September to November)

Summer low flow (15-30 ML/day during December to May)

Autumn low flow (15-30 ML/day during March to May)

Summer/autumn fresh (one fresh of 400-500 ML/day for two to five days during December to May)

  • Scour sediments around large wood, turn over bed sediments, replenish biofilms and maintain macrophyte habitat
  • Provide flow cues to stimulate native fish to breed and migrate
  • Maintain longitudinal connectivity for native fish passage
Fish iconMountain iconsPlant icon

Scenario planning

Table 5.5.2 outlines potential environmental watering and expected water use under a range of planning scenarios.

There are two sets of watering actions: one for upper Broken Creek and another for the Broken River. Delivering flow to upper Broken Creek is a higher priority, because upper Broken Creek has no inflows from tributaries and is more reliant on operational water deliveries and water for the environment. The potential watering actions for upper Broken Creek require less water than the potential watering actions for Broken River, and any environmental flows delivered to upper Broken Creek will pass through reaches 1 and 2 of the Broken River, where they will provide some environmental benefit.

All potential watering actions in the Broken and upper Broken Creek are required across all climatic scenarios, but there is insufficient water for the environment to meet most of them, and no environmental allocations are expected for the Broken system in 2022-23 under a drought scenario. The VEWH may elect to trade water into the system to meet high priority potential watering actions if a trade opportunity is available.

The main objective of environmental flows in the upper Broken Creek is to maintain low flow throughout the year so as to maintain water quality and habitat for native fish, platypus and waterbugs. Maintaining adequate flow and connectivity is particularly important during spring, when native fish, platypus, waterbugs and aquatic vegetation are most active and productive. Water for the environment will likely be prioritised for spring low flow under a dry climate scenario, and greater allocations under average and wet scenarios may be used to supplement low flow at any time of year as needed. Summer/ autumn freshes may be needed to help mitigate hypoxic blackwater events. The natural high flow that causes hypoxic blackwater events is most likely under average or wet climatic conditions. Goulburn Broken CMA will monitor conditions and may limit the use of water for the environment for low flow during low-risk periods to enable them to deliver emergency freshes if needed.

Year-round low flow is needed to support the Broken River environmental objectives, but there is little capacity to influence these with environmental flows, especially under drought and dry climate scenarios. Operational deliveries and natural tributary inflows will likely meet a large proportion of the recommended flow in the Broken River under average and wet climate scenarios, and water for the environment may be used to supplement any of the recommended low flows or summer/autumn freshes if needed.

Planning scenario table

Table 5.5.2 Potential environmental watering for the Broken River and upper Broken Creek under a range of planning scenarios

Planning scenario

Drought

Dry

Average

Wet

Expected river conditions

  • No unregulated flow in Broken River or upper Broken Creek
  • Low and cease- to-flow events are probable throughout the year in all reaches
  • Low, unregulated flow in Broken River and none in upper Broken Creek
  • Low and cease- to-flow events are possible throughout the year in all reaches
  • High winter/spring flow in Broken River
  • Some unregulated flow in upper Broken Creek
  • High winter/spring flow in Broken River
  • Unregulated flow in upper Broken Creek with some winter/spring freshes

Expected availability of water for the environment

  • 0 ML
  • 226 ML
  • 647 ML (plus available trade opportunity up to 1,500 ML)
  • 647 ML (plus available trade opportunity up to 1,500 ML)

Upper Broken Creek (targeting reach 1)

Potential environmental watering – tier 1 (high priorities)

Tier 1a (can be achieved with predicted supply)

  • N/A
  • Spring low flow
  • Winter low flow
  • Spring low flow
  • Summer low flow
  • Autumn low flow
  • Summer/autumn fresh
  • Winter low flow
  • Spring low flow
  • Summer low flow
  • Autumn low flow
  • Summer/autumn fresh

Tier 1b (supply deficit)

  • Winter low flow
  • Spring low flow
  • Summer low flow
  • Autumn low flow
  • Summer/autumn fresh
  • Winter low flow
  • Summer low flow
  • Autumn low flow
  • Summer/autumn fresh
  • N/A

Potential environmental watering – tier 2 (additional priorities)

  • N/A

Broken River (targeting reach 1, 2 and 3)

Potential environmental watering – tier 1 (high priorities)

Tier 1a (can be achieved with predicted supply)

  • N/A
  • Winter low flow
  • Spring low flow
  • Summer low flow
  • Autumn low flow
  • Summer/autumn fresh
  • Winter low flow
  • Spring low flow
  • Summer low flow
  • Autumn low flow
  • Summer/autumn fresh

Tier 1b (supply deficit)

  • Winter low flow
  • Spring low flow
  • Summer low flow
  • Autumn low flow
  • Winter low flow
  • Spring low flow
  • Summer low flow
  • Autumn low flow
  • Summer/autumn fresh
  • N/A

Potential environmental watering – tier 2 (additional priorities)

  • N/A

Possible volume of water for the environment required to achieve objectives

  • 0 ML (tier 1a)
  • 6,676 ML (tier 1b)
  • 226 ML (tier 1a)
  • 11,724 ML (tier 1b)
  • 2,147 ML (tier 1a)1
  • 0 ML (tier 1b)
  • 490 ML (tier 1a)1
  • 0 ML (tier 1b)

Priority carryover requirements for 2023-24

  • N/A

1 This assumes water available made through trade opportunity.

Engagement

Table 2 shows the partners and stakeholder organisations with which the Goulburn Broken CMA engaged when preparing the Broken system seasonal watering proposal.

Seasonal watering proposals are informed by longer-term plans such as regional catchment strategies, regional waterway strategies and environmental water management plans and other studies. These plans incorporate a range of environmental, cultural, social and economic perspectives and longer term integrated catchment and waterway management objectives. For further details, refer to the Goulburn Broken Regional Catchment Strategy and Goulburn Broken Waterway Strategy.

Table 2 Partners and stakeholders engaged in developing the Broken system seasonal watering proposal

Partner and stakeholder engagement
  • Broken Boosey Conservation Management Network
  • Broken Creek Field Naturalists Club
  • Goulburn Murray Landcare
  • Commonwealth Environmental Water Office
  • Goulburn- Murray Water
  • Parks Victoria
  • Individual landholders who are on the Broken Environmental Water Advisory Group
  • Individual community members on the Broken Environmental Water Advisory Group
  • Taungurung Land and Waters Council
  • Yorta Yorta Nation Aboriginal Corporation

Page last updated: 01/07/22