VEWH - Moorabool River

The lower section of Moorabool Yulluk (Moorabool River) between She Oaks and Batesford has nine private diversion weirs that are significant barriers to fish. These barriers have increased the extent of slow-flowing habitat and reduced habitat diversity.

The Moorabool system is a water supply catchment for Barwon Water and Central Highlands Water. Releases from Lal Lal Reservoir for urban water supply contribute to environmental outcomes in reach 3a and 3b (above Barwon Water’s diversion point at She Oaks) and allow more efficient delivery of water for the environment to reach 4. Barwon Water and Corangamite CMA coordinate operational and environmental releases, where possible, to optimise these benefits.

Water allocated to the Moorabool Yulluk (Moorabool River) environmental entitlement is stored in Lal Lal Reservoir. The entitlement includes passing flows that are a significant component of annual streamflows and help maintain low flows through winter. Water use is limited by both inflows to the reservoir and by a use cap specified in the entitlement. The priority reaches for deliveries of water for the environment are between Lal Lal Reservoir and She Oaks Weir (reaches 3 a and 3b, as shown in Figure 3.6.1), as that is where the small amount of available water can have the most benefit. Environmental flows may also provide some benefits to flow-dependent values in the reach between She Oaks Weir and the confluence with the Barwon River.

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

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

Maintain channel form and processes

Maintain physical habitat diversity

Maintain and improve a self-sustaining breeding population of platypus and support the dispersal of juveniles and the movement of adults

Maintain in-stream macrophyte communities

Maintain streamside vegetation communities and promote recruitment

Maintain the abundance and diversity of waterbug communities

Maintain water quality

Prevent hypoxic blackwater events

Improve and increase the distribution, abundance and diversity of migratory species (tupong, short-finned eel, common galaxias, spotted galaxias, short-headed lamprey and Australian grayling)

Maintain and increase the distribution, abundance and diversity of non-migratory species (flat-headed gudgeon, Australian smelt, southern pygmy perch and river blackfish)

Environmental values

Moorabool Yulluk (Moorabool River) is a highly flow-stressed system, but it retains significant environmental values.The river is home to native fish species, including the Australian grayling, river blackfish, Australian smelt, flat-headed gudgeon, southern pygmy perch, short-finned eel, spotted galaxias and tupong. The system also contains extensive areas of endangered remnant vegetation, including streambank shrubland and streamside woodland ecological vegetation communities. Platypus, rakali (water rats) and a range of waterbugs are also present. Moorabool Yulluk (Moorabool River) flows into the Barwon River, connecting it to the Ramsar-listed lower Barwon wetlands.

Recent conditions

Rainfall in the Moorabool catchment varied throughout 2021-22 and was slightly above the long-term average. Wet conditions in 2020-21 caused Lal Lal Reservoir to fill, and further catchment inflows caused it to spill between early August and December 2021. Reservoir spills and local run-off downstream of the reservoir met many of the recommended high flows that are needed to grow aquatic plant and animal populations but cannot be delivered with managed environmental water due to various system constraints. The full reservoirs also boosted environmental water allocations and will support deliveries for the next three years.

The delivery of water for the environment in the Moorabool system was managed according to an average climate scenario during 2021-22, and all planned actions under that scenario were fully achieved. Natural flows met all planned watering actions during winter and spring. Water for the environment was used to deliver planned low flows and freshes throughout summer and autumn.

Traditional Owner cultural values and uses

The Wadawurrung are the Traditional Owners of the land of Moorabool Yulluk (Moorabool River) and parts of the Barwon, Leigh and Yarrowee rivers.

Wadawurrung Traditional Owners have a strong connection to and place high cultural value on Moorabool Yulluk (Moorabool River). The Wadawurrung Traditional Owners Aboriginal Corporation (WTOAC) is a key partner in advocating for additional water recovery to help support environmental outcomes and cultural water objectives.

In 2020, the WTOAC released Paleert Tjaara Dja – Let’s make Country good together 2020 – 2030 Wadawurrung Country Plan . Waterways, rivers, estuaries and wetlands – Yulluk – are identified as key values to look after.

In 2019, the WTOAC partnered with Corangamite CMA to complete an environmental flows study for the upper Barwon, Yarrowee and Leigh rivers. Environmental flows studies are essential technical references for river managers, which identify the types of flows needed to support environmental and cultural values in a river system. The cultural values identified in the flows study apply to all waterways within Wadawurrung Country, including Moorabool Yulluk (Moorabool River).

The values include:

significant aquatic species such as Wad-dirring/peridak (platypus), Buniya (eels), Turrpurt (tupong), Ware-up (river blackfish), Tark (common reed) and Bal-yun (cumbungi) which are traditional sources of food, materials and medicines
waterway confluences and deep pools, which are places for meeting, ceremonies, trade and marking clan boundaries.

The WTOAC may partner with Corangamite CMA to coordinate the delivery of summer/autumn fresh events and some winter/ spring fresh events to coincide with cultural events. This can support significant cultural values and species for the lead-up to or duration of an event.

Social, recreational and economic values and uses

In planning the potential watering actions in Table 3.6.1, Corangamite CMA considered how environmental flows could support values and uses, including:

water-based recreation (such as camping, fishing, kayaking and swimming)
riverside recreation and amenity (such as birdwatching, bushwalking, camping, picnicking and lookouts) community events and tourism
socioeconomic benefits (such as for diverters for stock needs and domestic use: water levels and water quality can rely on the delivery of water for the environment, particularly in summer).

If the timing or management of planned environmental flows may be modified to align with a community benefit, this is acknowledged in Table 3.6.1 with the following icon.

Watering planned to support peaks in visitation (e.g. camping or other public activities on long weeks or school holidays))

Summer/autumn freshes provide a freshening flow in Moorabool Yulluk (Moorabool River) and are planned to coincide with school holidays and public holidays where possible. These flows improve opportunities for riverside and water-based recreation, in particular camping and fishing.

Scope of environmental watering

Table 3.6.1 describes the potential environmental watering actions in 2022-23, their expected watering effect (that is, the intended physical or biological effects of the watering action) and the longer-term environmental objectives they support. Each environmental objective relies on one or more potential environmental watering actions and their associated physical or biological effects.

Table 3.6.1 Potential environmental watering actions, expected watering effects and associated environmental objectives for the Moorabool system

Potential environmental watering action	Expected watering effects	Environmental objectives
Winter/spring low flow (5-60 ML/day during June to November)	Maintain in-stream vegetation Maintain connectivity and allow fish and platypus movement through the reach Reduce intrusion by terrestrial vegetation into the stream bed
Winter/spring freshes (three freshes, 80- 90 ML/day for five to 10 days during May to November)	Maintain pool and riffle habitats and provide connectivity to support fish and platypus movement through the reach Trigger downstream spawning migration of tupong (May-August) and upstream migration of juvenile Turrpurt (galaxias), tupong, Buniya (short- finned eel) and Australian grayling (September-November) Provide flow variability to maintain species diversity of the fringing vegetation and promote the growth and recruitment of streamside vegetation Flush silt, scour pools and remove biofilms from hard substrates and the stream bed to maintain waterbug communities and transport organic matter to prevent blackwater events
Summer/autumn low flow (5-40 ML/day during December to May)	Maintain refuge pools and riffle habitat for fish, waterbugs and platypus and submerged aquatic vegetation and allow movement through the reach Maintain water quality for aquatic life by reducing periods of low oxygen, high temperature and high electrical conductivity
Summer/autumn freshes (two to three freshes,30-80 ML/day for five days during December to May)	One small fresh at 30-60 ML/day to: maintain pool and riffle habitat and the condition of streamside vegetation, water fringing marginal zone vegetation and promote recruitment allow fish movement through the reach Freshes at 60-80 ML/day to: trigger downstream spawning migration of adult Buniya (short-finned eel) (January-February), tupong (May-August), Australian grayling (April-May) and short-headed lamprey maintain pool and riffle habitat and the condition of streamside vegetation, and promote recruitment allow fish and platypus to move through the reach to access habitat flush silt and scour biofilms and algae from the stream bed and substrates to improve habitat quality for waterbugs maintain water quality for plants and animals by reducing periods of low oxygen, high water temperature and salinity

Scenario planning

Table 3.6.2 outlines potential environmental watering and expected water use under a range of planning scenarios.

Moorabool Yulluk (Moorabool River) requires continuous low flows throughout the year and periodic freshes under all climate scenarios to achieve the intended environmental outcomes. Under drought and dry climate scenarios, the main objective is to provide sufficient habitat to maintain existing populations of native fish and platypus, and therefore flows can be delivered at the lower end of their recommended size range and frequency to ensure connecting flows are maintained for as long as possible. Water for the environment may be added to operational transfers at times to increase flow variability downstream of Lal Lal Reservoir and to maintain some flow in the reaches downstream of She Oaks Weir once operational water is diverted.

Even with these proposed watering actions, sections of the Moorabool River are likely to cease flowing under a dry or drought scenario, which will reduce environmental condition and the size of plant and animal populations.

Under average and wet climate scenarios, most of the recommended flows are expected to be provided through a combination of natural flows, passing flows and operational releases, which will mean water for the environment can be used to deliver additional freshes at any time of year to improve environmental conditions and increase populations of native plants and animals. Delivering a 60 ML per day fresh for five days in autumn will be a high priority under all climate scenarios to trigger Australian grayling migration and spawning. Autumn high flows are required two out of every three years to maintain and grow Australian grayling populations. They occurred in the Moorabool system in 2021-22 but not in 2020-21. They are needed in 2022-23 to help the population recover from past dry periods and provide a buffer in case there is a return to drier conditions in 2023-24.

Although environmental flows in Moorabool Yulluk (Moorabool River) primarily target outcomes in reaches 3 a and 3b, deliveries will be planned where possible to also provide benefits in reach 4.

The use of water for the environment in the Moorabool system is capped at 7,500 ML over three years. Under these rules, only 2,500 ML can be used in 2022-23, and full storages mean there is sufficient supply to support environmental flows until at least 2024-25.

Planning scenario table

Table 3.6.2 Potential environmental watering for the Moorabool system under a range of planning scenarios

Planning scenario	Drought	Dry	Average	Wet
Expected river conditions	Little rainfall with no inflow to Lal Lal Reservoir Regular periods of no flow	Below-average rainfall and inflow to Lal Lal Reservoir Cease-to-flow events	Average rainfall and moderate inflows to Lal Lal Reservoir,especially during winter and spring Low flow over summer and high peaks in winter months	Lal Lal Reservoir is likely to fill and spill Continuous flow year-round Overbank conditions in some parts during winter/spring
Expected availability of water for the environment	2,500 ML	2,500 ML	2,500 ML	2,500 ML
Moorabool River (targeting reach 3 a)
Potential environmental watering – tier 1 (high priorities)	Tier 1a (can be achieved with predicted supply)
	Winter/spring low flow (partial) Summer/autumn low flow (partial) Summer/autumn fresh (one fresh of 60 ML/day)	Winter/spring low flow (partial) Winter/spring fresh (one fresh) Summer/autumn low flow (partial) Summer/autumn fresh (one fresh of 60 ML/day)	Winter/spring low flow Winter/spring fresh (one fresh) Summer/autumn low flow (partial) Summer/autumn fresh (one fresh of 30-60 ML/day and two freshes of 60 ML/day)	Winter/spring low flow Winter/spring freshes (three freshes) Summer/autumn low flow Summer/autumn fresh (one fresh of 30-60 ML/day and two of 60 ML/day)
	Tier 1b (supply deficit)
	Winter/spring freshes (two freshes)	Winter/spring fresh (one fresh)	Winter/spring freshes (two freshes)	N/A
Potential environmental watering – tier 2 (additional priorities)	Winter/spring low flow (delivered at upper magnitude) Summer/ autumn low flow (delivered at upper magnitude) Summer/ autumn freshes (three freshes, delivered at upper magnitude)	Winter/spring low flow (delivered at upper magnitude) Winter/spring freshes (two freshes) Summer/ autumn low flow (delivered at upper magnitude) Summer/ autumn freshes (three freshes, delivered at upper magnitude)	Winter/spring freshes (three freshes) Summer/ autumn low flow (delivered at upper magnitude) Summer/ autumn freshes (three freshes, delivered at upper magnitude)	Summer/ autumn freshes (three freshes, delivered at upper magnitude)
Possible volume of water for the environment required to achieve objectives	2,243 ML (tier 1a) 1,130 ML (tier 1b) 15,055 ML (tier 2)	2,508 ML (tier 1a) 565 ML (tier 1b) 15,055 ML (tier 2)	2,510 (tier 1a) 990 ML (tier 1b) 14,900 ML (tier 2)	780 (tier 1a) 0 ML (tier 1b) 9,300 ML (tier 2)
Priority carryover requirements for 2023-24	The environmental entitlement for the Moorabool system caps use at 7,500 ML over three years. Use in 2022-23 will be capped at 2,500 ML, which will leave sufficient allocation to support watering actions in 2023-24 and 2024-25

Engagement

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

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

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

Partner and stakeholder engagement
Australian Platypus Conservancy Geelong Landcare Network Local community groups Moorabool Stakeholder Advisory Committee People for a Living Moorabool Barwon Water Central Highlands Water Department of Environment, Land, Water and Planning - Water and Catchments Southern Rural Water Parks Victoria Landholders on the Moorabool Stakeholder Advisory Committee Recreational users on the Moorabool Stakeholder Advisory Committee Wathaurung Aboriginal Corporation

Partner and stakeholder engagement

Australian Platypus Conservancy
Geelong Landcare Network
Local community groups
Moorabool Stakeholder Advisory Committee
People for a Living Moorabool
Barwon Water
Central Highlands Water
Department of Environment, Land, Water and Planning - Water and Catchments
Southern Rural Water
Parks Victoria
Landholders on the Moorabool Stakeholder Advisory Committee
Recreational users on the Moorabool Stakeholder Advisory Committee
Wathaurung Aboriginal Corporation

Page last updated: 01/07/22