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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 higher 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 availability of water due to the small volume of Water Holdings in the Broken system. Environmental water holders can trade it 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 flows and to 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 for freshes in the Broken River. In 2020-21, accumulated passing flows were used to supplement the flow in upper Broken Creek for the first time. 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.

Traditional Owners
Storage manager
Environmental water holder

System map

Environmental watering objectives in the Upper Broken Creek

Fish icon
Increase 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 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 and daily maximum temperatures across the Broken catchment in 2020-21 were close to the long-term average. Allocations against high-reliability water shares in the Broken system started the year at 17 percent and rose to 100 percent in October, due to consistent inflows that caused Lake Nillahcootie to fill and spill. Accumulated passing flows carried over from 2019-20 in the Broken River were used to supplement low flow on days when there was no passing flow in the Broken River and to deliver winter/spring low flow in upper Broken Creek before Lake Nillahcootie spilled.

While recent conditions in the Broken catchment aligned with an average climate, water for the environment was managed in the Broken system in line with a dry climate scenario during 2020-21. Due to low operational flows in upper Broken Creek, water for the environment was used to maintain low flow throughout the year in the creek, and there was insufficient water to deliver a fresh. Minimum low- flow targets in all reaches of the Broken River were largely met with a combination of operational releases, tributary inflows and the use of accumulated passing flows. There were several natural freshes between July and October 2020, but recommended summer and autumn freshes could not be delivered, due to limited environmental Water Holdings.

A combination of accumulated passing flows and water for the environment was used to maintain winter and spring low flow in upper Broken Creek until October when the banked passing flows were lost with the spill of Lake Nillahcootie. After October, water for the environment was used (with additional water traded into the system) to meet summer and autumn low flow in upper Broken Creek. This low flow maintained water quality within target levels, so additional summer and autumn freshes were not required.

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 practice 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 Taungurung Land and Waters Council to identify more specific cultural objectives for the system in future. 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 advised that water for the environment in the Broken River and upper Broken Creek supported the following Yorta Yorta values:

  • common reed contained within the slack water provides important material for tools, while also providing refuge for culturally important large and small-bodied fish species
  • 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 spaces are important to the community for wellbeing and mental health
  • community events and tourism (such as markets around Benalla Lake)
  • socio-economic benefits (such as consumptive water; water for irrigation and stock and domestic use; and water to support terrestrial birds that help control agricultural pests).

Scope of environmental planning

Table 1 Potential environmental watering actions and objectives for the upper Broken Creek and Broken River

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 in 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

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: 22/01/21