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Reach 1 of the Coliban River below Malmsbury Reservoir to Lake Eppalock can benefit from environmental watering. An important distinction between the Coliban River and other regulated Victorian systems is the lack of irrigation demand in the river, as Coliban Water deliver water from the Malmsbury Reservoir via a pipe-and-channel network. Therefore, the river below this point is not subject to the high summer flows that other regulated systems experience: delivering summer flows relies on environmental water releases.

The VEWH does not have any environmental entitlements in the Coliban system but the ability to flexibly manage passing flows in the system provides an opportunity to help mitigate summer low-flow risks. There is a small volume of Commonwealth environmental water held in the system but the high cost of delivery means it is not planned to be used in 2016–17.

Environmental watering objectives in the Colliban River

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Protect and boost populations of native fish by providing flows for them to move upstream and downstream, encouraging spawning
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Maintain habitat for waterbugs which provide energy, break down dead organic matter and support the river’s food chain
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Maintain water, riverside and in-stream plants
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Improve water quality

Environmental values

The Coliban River contains a diverse range of waterbugs supported by stands of emergent and submergent aquatic plants. It is bordered by remnant patches of streambank shrubs providing habitat for a diverse range of terrestrial species. Historical records show that a diverse range of native freshwater fish species (including the Murray cod, river blackfish, Macquarie perch and Australian smelt) inhabited the river, as do populations of platypus and native water rats.

Social and economic values

Local communities highly value the Coliban River including those in Malmsbury, Taradale and Metcalfe. Of particular interest are the aesthetic and recreational values of the river (including Ellis Falls and the Cascades). Popular recreational activities in the area include camping, fishing and bird watching. The storages supply urban, stock and domestic demands in the surrounding area.

Conditions mid-2016

In 2015–16, conditions were dominated by below-average rainfall in most months and corresponding very low volumes of inflows to the storage (around 11 percent of the long-term average).

A portion of passing flows (water released from reservoirs to operate river and distribution systems, maintain environmental values and other community benefits) was withheld in spring to reserve water to support the river over summer/autumn. A summer storm provided a flush through the river in January. The withheld flows were then used to deliver a fresh in March to refill and flush remaining pools, with the river having stopped flowing at Lyal.

The water delivered was generally well below the environmental flow recommendations for the system. However, water availability in 2015–16 was limited and management aimed to protect native species under drought conditions, particularly following cease-to-flow periods in summer.

Scope of environmental watering

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

Potential environmental watering

Environmental objectives

Summer/autumn pulsed flows (5–15 ML/day for up to 2 weeks in December–May as required)1

  • Maintain water quality (including dissolved oxygen levels) and habitat for aquatic animals

Summer/autumn low flows (2.5–5 ML/day in December–May)

  • Maintain aquatic vegetation
  • Maintain fish habitat
  • Maintain permanent connectivity of river for improved water quality
  • Maintain aquatic habitat for waterbugs
  • Maintain habitat for platypus

Summer/autumn freshes (of 50–100 ML/day for 3 days each in December–May)

  • Maintain riparian and in-channel recruiting vegetation
  • Provide native fish habitat, movement and spawning
  • Provide connectivity for water quality
  • Maintain aquatic habitat for waterbugs
  • Maintain habitat for platypus

1 The actual volume and duration of pulsed flows will depend on available water resources, climatic conditions and conditions within the river.

Scenario planning

Water availability in the Coliban system relies on withheld passing flows in winter/spring for use in the high-risk summer period when issues such as poor water quality are more likely and providing constant low flows and/or short pulses/freshes can maintain habitat below the reservoir.

The volume of water available will vary depending on inflows and the volume of passing flows available, with a lower volume likely to be available under a drought/dry scenario. Water is therefore not likely to be available to provide summer/autumn freshes except under average or wet conditions. The target flows and duration of freshes to manage a potentially catastrophic water quality problem will vary depending on water availability and climate and river conditions. There is insufficient water available to meet all the environmental water requirements of the Coliban system.

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

Planning scenario



Expected river conditions

  • Little-to-no unregulated flows
  • Some unregulated river flows from tributary inflows

Expected availability of environmental water

  • Minimal passing flows and low volume to withhold for use at other times in the season
  • Moderate-to-high passing flows with good volumes available but reduced ability to reserve flows due to possible storage spills
  • Withheld flows for use at other times in the season

Potential environmental watering – tier 1 (high priorities)

  • Summer/autumn pulsed flows
  • Summer/autumn low flows
  • Summer/autumn low flows
  • Summer/autumn freshes

Potential environmental watering – tier 2 (additional priorities) 1

  • Increased magnitude of summer/autumn low flows


Possible volume of environmental water required to achieve objectives

  • 900 ML (tier 1)
  • 250 ML (tier 2)
1,200  ML (tier 1)

Priority carryover requirements

  • Reserve passing flows for 2017–18

1 Only a priority after 2017–18 critical requirements have been set aside

2 Environmental water requirements for tier 2 actions are additional to tier 1 requirements.

Risk management

In preparing its seasonal watering proposal, North Central 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.


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.

In the North Central region communities are involved in decisions about the Loddon and Campaspe river systems, Murray river system including Gunbower Forest and some of the wetlands connected by the Wimmera-Mallee pipeline. This happens through formal advisory groups: Environmental Water Advisory Groups including river and wetland focused groups and the Gunbower Island Community Reference Group.

Who is engaged and how

Recreational users

Through formal advisory groups, recreational users provide local advice and raise opportunities for potential 'shared benefits' from environmental watering. Through Environmental Water Advisory Groups, recreational users are informed of environmental water deliveries and provide data that assists with reporting on the outcomes of environmental watering.

Goulburn-Murray Water engages with recreational user groups (such as Save Lake Eppalock and Lake Meran Users Group) that use water storages for recreation through planned consultations and meetings to discuss storage levels and potential impacts of environmental water releases from storages.

Environment groups

Through formal advisory groups, environment groups provide local knowledge, land management advice and advocate for the environment. They are also informed of environmental water deliveries and provide data that assists with reporting on the outcomes of environmental watering (including citizen science monitoring data such as providing bird counts).


Through formal advisory groups, farmers and landholders (including those who own private wetlands that receive environmental water) provide local knowledge and land management advice regarding environmental watering.

They are also informed of environmental water deliveries and provide data that assists with reporting on the outcomes of environmental watering. Goulburn-Murray Water engages (and often) with consumptive entitlement holders (often irrigators) and landholders (often with river frontages).

Traditional Owners

Through the North Central Catchment Management Authority Indigenous Facilitator, Traditional Owners from the Barapa Barapa, Dja Dja Wurrung and Yorta Yorta Nations are given the opportunity to provide input to seasonal watering proposals. The Catchment Management Authority and the Barapa Barapa Nation have conducted a cultural values mapping project in Gunbower Forest which will eventually enable cultural values to be incorporated in Gunbower environmental water planning. The Barapa Barapa and Yorta Yorta Nations undertake monitoring of cultural values in Gunbower Forest.

There are Dja Dja Wurrung and Yorta Yorta representatives from the North Central region who are members of the Murray Lower Darling Rivers Indigenous Nations. The Victorian Environmental Water Holder, the Commonwealth Environmental Water Holder and the Murray Darling Basin Authority engage the Murray Lower Darling Rivers Indigenous Nations on strategic (often longer term) issues related to environmental watering.


Councils are invited to participate in formal advisory groups meetings. Goulburn-Murray Water  consults with the City of Greater Bendigo, Gannawarra Shire and Swan Hill Rural City Council regularly on water management, including on environmental water management.

General public

The North Central Catchment Management Authority communicates and engages with the general public through their website, media releases, newsletters, public notices, community forums, community events (such as tours of Gunbower Forest during environmental watering), social media and direct contact to interested parties by email distribution list.