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The Moorabool River is a highly regulated river that, despite substantial extraction and many years of drought, still retains significant environmental values. It flows southward from the Central Highlands between Ballarat and Ballan to join the Barwon River at Fyansford. The catchment is heavily farmed with about three-quarters of the catchment area used for agriculture.

Water allocated to the Moorabool River environmental entitlement is stored in Lal Lal Reservoir and includes passing flows that help maintain flows in the river. The Moorabool is also a water supply catchment for Barwon Water with releases from Lal Lal Reservoir being diverted for urban water supply at She Oaks Weir. These releases contribute to environmental outcomes in reach 3a and 3b and allow more efficient delivery of environmental water to reach 4. Barwon Water and Corangamite CMA work together to maximise these benefits.

There are several large water storages in the upper reaches of the river (including Lal Lal Reservoir). In the lower reach (between She Oaks and Batesford) there are nine private diversion weirs that are a significant barrier to fish. These barriers have increased the extent of slow-flowing habitat and reduced habitat diversity in the lower reach of the Moorabool, reducing the diversity and abundance of migratory fish in this part of the river.

Environmental water can be used to manage flows in reaches 3a, 3b and 4. The priority reaches for environmental water delivery are the reaches between Lal Lal Reservoir and She Oaks Weir (reaches 3a and 3b, as shown on the map), as these are where the small amount of available environmental water can have the most beneficial impact. Environmental water delivered also provides benefits to significant flow-dependant values in reach 4, which flows from She Oaks Weir, Meredith down to the confluence with the Barwon River in Geelong (see system map below).

Environmental water holder

System map

Moorabool System
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 Moorabool River

Water icon
Improve water quality during the year, particularly during summer
Insect icon
Maintain a wide range of waterbugs to provide energy, break down dead organic matter and support the river’s food chain
Landscape icon
Reshape the river bank and bed and ensure fish and other water animals have a range of habitat pools and places to shelter
Plant icon
Maintain remnant vegetation communities including a range of macrophytes (large water plants) within the river channel; these communities provide shade and food for organisms further up the food chain
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Protect and boost native fish populations (including Australian grayling, southern pygmy perch, spotted galaxias, tupong and short-finned eel) by providing flows for fish to move upstream and downstream and encouraging fish to spawn

Environmental values

The Moorabool River is home to native fish species including the Australian grayling, river blackfish, Australian smelt, flat-headed gudgeon, southern pygmy perch, short-finned eel and tupong. The system contains extensive areas of endangered remnant vegetation including stream bank shrubland and riparian woodland ecological vegetation communities. Diverse populations of waterbugs, platypus and water rats are also present. The Moorabool River flows into the Barwon River, connecting it to the Ramsar-listed lower Barwon wetlands.

Social and economic values

The Moorabool system has important environmental values and supports a range of recreational activities with parks, walking trails, picnic sites, lookouts, swimming holes, fishing and camping spots and historic bridges located along its length. Lal Lal Reservoir is used to supply water to the Ballarat region. Water from Lal Lal is also delivered via the Moorabool River to She Oaks Weir to supply towns in the Geelong region. The Moorabool River is a place of importance for Traditional Owners and their Nations in the region.

Conditions mid-2016

There was a sharp decline in rainfall in the Moorabool catchment in 2015–16, with minimal river flows even in typically higher-flow periods in winter and spring. Water available under the entitlement relied heavily on water carried over from 2014–15 with only minor increases through the year. The lack of catchment inflows and warm weather caused cease-to-flow periods in summer for the first time since the millennium drought, resulting in a stretch of dry river bed near Batesford.

Trigger-based summer freshes were the priority for the Moorabool River in 2015–16, to improve water quality and top up habitat refuge pools as much as possible given the limited environmental water available. In summer, the trigger-based freshes restored flow connectivity between the Moorabool and Barwon rivers, highlighting the value of these small releases in dry periods.

Three trigger-based freshes were delivered to the Moorabool River in 2015–16, one in mid-December, one in March and one in May. Barwon Water's consumptive water releases from Lal Lal Reservoir also helped to meet low-flow targets in the summer period.

Scope of environmental watering

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

Potential environmental watering1

Environmental objectives

Summer/autumn low flows (5–20 ML per day in December–May)

  • Provide pool and riffle habitats for fish, waterbugs, platypus and submerged aquatic vegetation
  • Maintain water quality

Summer/autumn freshes (2–3 freshes targeting 30–60 ML per day for 3–5 days in December–May)2

  • Allow fish and platypus movement and maintain access to habitat
  • Flush silt and scour biofilms and algae from streambed
  • Maintain fringing marginal zone vegetation
  • Trigger downstream spawning migration of adult short-finned eel and grayling
  • Maintain water quality, fill up habitat refuge pools and avoid critical loss of biota

Winter/spring low flows (60–86 ML per day in June – November)

  • Allow fish movement throughout the reach
  • Maintain clear flow path and control intrusions by terrestrial vegetation

Winter/spring freshes (2–3 freshes targeting more than 162 ML per day for 10 days in June - November)

  • Allow fish and platypus movement through the reach and maintain access to habitat
  • Trigger downstream spawning migration of adult tupong and upstream migration of juvenile galaxias, tupong, short-finned eel and grayling
  • Flush silt and scour biofilms and algae from streambed and transport of organic matter
  • Promote growth and recruitment of native riparian vegetation including woody shrubs and promote strong vegetation zonation on the banks

Winter/spring high flow (1 fresh targeting 500 to 3,000 ML per day for 1–2 days in June–November)

  • Scour pools and maintain channel form and dimensions
  • Flushing of sediment to improve spawning sites
  • Inundate billabongs

1 The target reaches for environmental watering are reach 3a, 3b and 4 of the Moorabool system unless otherwise stated.

2 Due to the low water availability in the Moorabool system, trigger-based freshes will be provided as required to maintain water quality, particularly in important refuge pools. These events are likely to be significantly lower than the recommended magnitude and duration.

Scenario planning

Due to the limited volume of environmental water expected to be available in the Moorabool system, the priority for environmental water delivery is to protect water quality and fish in the higher-risk summer/autumn period. Over summer in a dry year, trigger levels for dissolved oxygen, electrical conductivity and water temperature are monitored and used to inform the release of freshes to improve water quality. If wetter conditions eventuate, unregulated flows are likely to help meet minimum environmental flow requirements, and winter freshes or low flows may become a priority.

Although environmental watering focuses on reaches 3a and 3b, some releases will benefit reach 4. Where possible, deliveries to reaches 3a and 3b will be planned to maximise the benefit for reach 4, for instance by increasing summer fresh volumes when water availability allows. The CMA prioritises carryover of 750 ML each year (if possible) to allow delivery of trigger-based freshes in the following years if low inflows continue. Given low inflows in 2015–16, only about 700 ML was available to carry over into 2016–17.

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

Planning scenario

Drought

Dry

Average

Wet

Expected river conditions

  • Minimal catchment inflows
  • Limited passing flows
  • Low catchment inflows
  • Passing flows
  • Moderate catchment inflows
  • Unregulated and passing flows
  • High catchment inflows
  • Unregulated and passing flows
  • Expected availability of environmental water

    • 700 ML carryover
    • 300 ML inflows
    • ~1,000 ML total
  • 700 ML carryover
  • 1,800 ML inflows
  • ~2,500 ML total
  • 700 ML carryover
  • 4,300 ML inflows
  • ~5,000 ML total
  • 700 ML carryover
  • 6,386 ML inflows
  • ~7,086 ML total
  • Potential environmental watering – tier 1 (high priorities)

    • Summer/autumn freshes
  • Summer/autumn freshes (trigger-based)
  • Winter/spring freshes
  • Summer/autumn low flows
  • Summer/autumn freshes
  • Winter/spring freshes
  • Summer/autumn low flows
  • Summer/autumn freshes
  • Winter/spring freshes
  • Summer/autumn low flows
  • Potential environmental watering – tier 2 (additional priorities)

    • Summer/autumn freshes
    • Winter/spring freshes
    • Summer/autumn low flows
    • Winter/spring low flows
  • Summer/autumn freshes
  • Summer/autumn Low flows
  • Winter/spring freshes
  • Winter/spring low flows
  • Summer/autumn low flows
  • Summer/autumn freshes
  • Winter/spring freshes
  • Winter/spring low flows
  • Winter/spring high flows
  • Winter/spring low flows
  • Winter/spring high flows
  • Possible volume required to achieve tier two objectives1

    • 240 ML (tier 1)
    • 5,500 ML (tier 2)
  • 1,670 ML (tier 1)
  • 4,070 ML (tier 2)
  • 2,500 ML (tier 1)
  • 7,870 ML (tier 2)
  • 2,500 ML (tier 1)
  • 5,600 ML (tier 2)
  • Priority carryover requirements

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

    Risk management

    In preparing its seasonal watering proposal, Corangamite CMA 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.

    In the Corangamite region communities are involved in decisions about the Moorabool river and Lower Barwon wetlands. This happens through formal advisory groups including a Moorabool stakeholder advisory and the Lower Barwon community advisory committees.

    Who is engaged and how

    Recreational users

    Through formal advisory groups, recreational user representatives (Field & Game Australia; Geelong Gun and Rod Association; VRFish) provide advice and communicate their priorities. They are informed of environmental water deliveries and provide data that assists with reporting the outcomes of environmental watering.

    Field & Game Australia (Geelong branch) has been a key advocate for environmental watering, providing assistance in monitoring activities and on-ground works.

    Environment groups

    Through formal advisory groups, environmental groups (People for a Living Moorabool; Geelong Environment Council; Geelong Landcare Network; Environment Victoria; Geelong Field Naturalists) provide local knowledge and advocate for the environment - specifically on seasonal watering proposals and longer term Environmental Water Management Plans. Environmental groups also receive email updates during environmental water delivery.

    Landholders/farmers

    Through formal advisory groups, landholders (specifically those who own land with river frontage, and commercial eel fishers in the lower Barwon wetlands) provide local knowledge and 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.

    Traditional Owners

    Traditional Owners are invited to participate in engagement activities regarding the Moorabool River and the Lower Barwon wetlands.

    Councils

    The City of Greater Geelong and Moorabool Shire have been invited to join formal advisory groups.

    General public

    The Corangamite Catchment Management Authority website and media releases on environmental watering are the main mechanisms for communications and engagement with the general public on environmental watering.

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