The Moorabool River flows southward from the Central Highlands between Ballarat and Ballan and joins the Barwon River at Fyansford. The Moorabool River, (Mooroobull Yluk) flows through Wadawurrung Country and has great cultural significance for Wadawurrung Traditional Owners.
The river’s catchment is heavily farmed, with about 65% of its 1,150km2 deemed as being agricultural-related land cover. It is a highly regulated waterway with three major water storages – the Moorabool, Bostock, and Lal Lal Reservoirs.
The Moorabool River Environmental Entitlement 2010 is held in the Lal Lal Reservoir and can store up to 7,086ML. This entitlement is subject to delivery rules (a maximum of 7,500ML over three years) which effectively provides the environment with an average of 2,500ML per year. No environmental entitlement exists for Bostock or Moorabool reservoirs, however passing flow rules are in place.
The Moorabool River is one of the most stressed rivers in Victoria, and as a water supply catchment with significant environmental values it is listed as a priority waterway in the Corangamite Waterway Strategy 2014-22.
Water for the environment can be released from Lal Lal Reservoir as base flow to maintain connectivity and provide fresh water for plants and animals. It can also be releases as a ‘fresh’ or a pulse of water which carefully timed to trigger fish migration and spawning.
Releases primarily affect the two river reaches (3a and 3b) immediately downstream of Lal Lal Reservoir. Some benefit can also be gained further down in reach 4, particularly when releases are piggy-backed on top of Barwon Water transfers between Lal Lal and Sheoaks, as ‘wetting up’ and evaporative losses are minimised.
Watering actions (or flow components) are informed by FLOWS studies which are conducted every 5-10 years. They are delivered in a priority order guided by science and water availability. There is insufficient natural flow and environmental water to achieve all the recommended watering actions, so actions are prioritised starting with summer/autumn low flow, then winter/spring low flow, followed by summer/autumn freshes and lastly winter/spring freshes. Flow variability (different volumes of water throughout each release) has a positive impact on the diverse ecosystem by aiding native species, providing different levels of inundation of sediments which benefits varying flora and fauna species. We will continue flow variability for 2023-24 water year (financial year).
The conditions in the Moorabool in 2022-23 have been very wet as compared to years prior to 2020, with all winter/spring flow components being achieved naturally which does not usually occur. This allowed the entitlement to be focused on summer/autumn low flow and freshes at greater volumes than can usually be achieved. It is projected that there will be below average rainfall in the Moorabool catchment for 2023-24, and thereby releases will likely begin earlier (likely spring) resulting in summer/autumn releases may not being able to be as large as the previous several wet years.
The increase of water in the entitlement that is confirmed via the Central and Gippsland Sustainable Water Strategy (the SWS) will be critical to increase the likelihood of supporting the river (including downstream of reach 3a and 3b) though summer/autumn, which is not able to be achieved with the current entitlement.
| Priority | Flow Component | Flow Objectives |
| 1 | Summer/autumn low flow (*5- 40ML/day Dec-May) | • Rehabilitate migratory species (tupong, short-finned eel, common galaxias, spotted galaxias, short-headed lamprey, Australian grayling) • Maintain and expand populations of non-migratory fish species (flat-headed gudgeon, Australian smelt, southern pygmy perch, river blackfish) • Maintain the diversity and abundance of macroinvertebrates suited to both slow and fast flowing habitats • Maintain aquatic zone species • Maintain platypus population, particularly in refuge pools during dry years; restore self-sustaining breeding population of platypus • Support dispersal of juvenile platypus to/from the Barwon River • Prevent low dissolved oxygen conditions and elevated EC conditions during low flow periods Critical to prevent the river from ceasing to flow, maintaining connectivity, and to provide some water to refuge pools over summer. This watering action should always be delivered. Even though 5ML/day is the dry season recommendation, *5ML/day will be the target for 2023-24 to allow some water for maintaining other PWAs. The maximum flow rate of 40 ML/day includes Barwon Water’s transfer to She Oaks weir and passing flows. Therefore 40 ML/day maximum has been established to allow some environmental water to pass She Oaks weir in the event that Barwon Water were transferring and off taking. Allowing environmental water past She Oaks increases the likelihood of maintaining connectivity through reach 4. |
| 2 | Winter/spring low flow (*5-60 ML/day, Jun-Nov) | • Rehabilitate migratory species (tupong, short-finned eel, common galaxias, spotted galaxias, short-headed lamprey, Australian grayling) • Maintain and expand populations of non-migratory fish species (flat-headed gudgeon, Australian smelt, southern pygmy perch, river blackfish) • Maintain aquatic zone species Critical to prevent the river from ceasing to flow and combined with natural inflow aids connectivity. This watering action should always be delivered when natural flow is not sufficient. Even though 5ML/day is the dry season recommendation, *5ML/day will be the target for 2023-24 to allow some water for maintaining summer/autumn low flows and other PWAs. |
| 3 | Summer/autumn fresh event (Apr/May, *60-80ML/d for five days) | · Rehabilitate migratory species (tupong, short-finned eel, common galaxias, spotted galaxias, short-headed lamprey, Australian grayling) · Maintain and expand populations of non-migratory fish species (flat-headed gudgeon, Australian smelt, southern pygmy perch, river blackfish) · Maintain the diversity and abundance of macroinvertebrates suited to both slow and fast flowing habitats · Maintain marginal zone species · Maintain damp zone species For a wet/average year, a summer autumn fresh should occur twice. Once in Jan/Feb (priority 4) and once in April/May (priority 3). If climatic conditions were to change to be ‘dry’, this priority 3 fresh in April/May would still be delivered if water was available, and but the priority 4 fresh would not. This fresh event was last delivered in April 2022 and will also be delivered in mid-April 2023 (current water year). The FLOWS study does not denote a maximum magnitude for summer/autumn freshes, therefore the maximum magnitude of summer/autumn freshes is dependent on the magnitude of winter freshes. The maximum of 80ML/day in this proposal is based on the minimum magnitude for a winter/spring fresh being 80ML/day. *60ML/day will be the target for 2023-24 to allow some water for maintaining other PWAs. The 80 ML/day maximum also allows some environmental water to pass She Oaks weir in the event that Barwon Water were transferring and off taking. Allowing environmental water past She Oaks increases the likelihood of maintaining connectivity through reach 4. |
| 4 | Summer/autumn fresh event (Jan/Feb, *60-80 ML/day for five days) | · Rehabilitate migratory species (tupong, short-finned eel, common galaxias, spotted galaxias, short-headed lamprey, Australian grayling) · Maintain and expand populations of non-migratory fish species (flat-headed gudgeon, Australian smelt, southern pygmy perch, river blackfish) · Maintain the diversity and abundance of macroinvertebrates suited to both slow and fast flowing habitats · Maintain marginal zone species · Maintain damp zone species For a wet/average year, a summer autumn fresh should occur twice. Once in Jan/Feb (priority 4) and once in April/May (priority 3). If climatic conditions were to change to be ‘dry’, the priority 3 fresh in April/May would still be delivered if water was available, and but this priority 4 fresh would not. This fresh event was last delivered in Jan 2023. In dry years eels should survive without this trigger. The FLOWS study does not denote a maximum magnitude for summer/autumn freshes, therefore the maximum magnitude of summer/autumn freshes is dependent on the magnitude of winter freshes. The maximum of 80ML/day in this proposal is based on the minimum magnitude for a winter/spring fresh being 80ML/day. *60ML/day will be the target for 2023-24 to allow some water for maintaining other PWAs. The 80ML/day maximum also allows some environmental water to pass She Oaks weir in the event that Barwon Water were transferring and off taking. Allowing environmental water past She Oaks increases the likelihood of maintaining connectivity through reach 4. |
| 5 | Little summer/autumn fresh event (Feb/Mar, *30-60 ML/day for three days) | · Rehabilitate migratory species (tupong, short-finned eel, common galaxias, spotted galaxias, short-headed lamprey, Australian grayling) · Maintain and expand populations of non-migratory fish species (flat-headed gudgeon, Australian smelt, southern pygmy perch, river blackfish) · Maintain marginal zone species · Maintain the diversity and abundance of macroinvertebrates suited to both slow and fast flowing habitats To be delivered in addition to priority 3 and 4 in wet/average years according to FLOWS study. This fresh is important for watering fringing vegetation. *30ML/day will be the target for 2023-24 to allow some water for maintaining other PWAs. The FLOWS study does not denote a maximum magnitude for the little summer/autumn fresh, therefore the maximum magnitude is dependent on the magnitude of the larger summer/autumn freshes. The maximum of 60ML/day in this proposal is based on that the minimum magnitude for the larger summer/autumn freshes is 60ML/day. *30ML/day will be the target for 2023-24 to allow some water for maintaining other PWAs. The 60ML/day maximum also allows some environmental water to pass She Oaks weir in the event that Barwon Water were transferring and off taking. Allowing environmental water past She Oaks increases the likelihood of maintaining connectivity through reach 4. |
| 6 | Winter/spring fresh event (Sep-Nov, *80-90 ML/day for 5-10 days) | · Rehabilitate migratory species (tupong, short-finned eel, common galaxias, spotted galaxias, short-headed lamprey, Australian grayling) · Maintain and expand populations of non-migratory fish species (flat-headed gudgeon, Australian smelt, southern pygmy perch, river blackfish) · Maintain aquatic zone species · Maintain the diversity and abundance of macroinvertebrates suited to both slow and fast flowing habitats · Maintain marginal zone species · Maintain damp zone species The FLOWS study update specifies that winter/spring fresh events are prioritised after all low flow recommendations, and summer/autumn freshes. These events are unlikely to be achieved naturally unless it is a wet year. Considering the winter/spring freshes as a group, a Sep-Nov fresh (priority 6) and the May-Aug fresh (priority 7) should be delivered in all years, where water is or becomes available. In an average or wet year an additional Sep-Nov fresh (priority 8) should also be delivered. *80ML/day will be the target for 2023-24 to allow some water for maintaining other PWAs. In wetter years 90ML/day will be the target due to the constraint of Dollys Creek Road. |
| 7 | Winter/spring fresh event (May-Aug, *80- 90ML/d for 5-10 days) | · Rehabilitate migratory species (tupong, short-finned eel, common galaxias, spotted galaxias, short-headed lamprey, Australian grayling) · Maintain aquatic zone species · Maintain the diversity and abundance of macroinvertebrates suited to both slow and fast flowing habitats · Prevent potential blackwater events that can lead to fish kills · Maintain marginal zone species Maintain damp zone species The FLOWS study update specifies that winter/spring fresh events are prioritised after all low flow recommendations, and summer/autumn freshes. These events are unlikely to be achieved naturally unless it is a wet year. Considering the winter/spring freshes as a group, a Sep-Nov fresh (priority 6) and the May-Aug fresh (priority 7) should be delivered in all years, where water is or becomes available. In an average or wet year an additional Sep-Nov fresh (priority 8) should also be delivered. *80ML/day will be the target for 2023-24 to allow some water for maintaining other PWAs. In wetter years 90ML/day will be the target due to the constraint of Dollys Creek Road. |
| 8 | Winter/spring fresh event (Sep-Nov, *80-90 ML/day for 5-10 days) | · Rehabilitate migratory species (tupong, short-finned eel, common galaxias, spotted galaxias, short-headed lamprey, Australian grayling) · Maintain aquatic zone species · Maintain the diversity and abundance of macroinvertebrates suited to both slow and fast flowing habitats · Maintain marginal zone species Maintain damp zone species The FLOWS study update specifies that winter/spring fresh events are prioritised after all low flow recommendations, and summer/autumn freshes. These events are unlikely to be achieved naturally unless it is a wet year. Considering the winter/spring freshes as a group, a Sep-Nov fresh (priority 6) and the May-Aug fresh (priority 7) should delivered in all years, where water is or becomes available. In an average or wet year an additional Sep-Nov fresh (priority 8) should also be delivered. *80ML/day will be the target for 2023-24 to allow some water for maintaining other PWAs. In wetter years 90ML/day will be the target due to the constraint of Dollys Creek Road. |
The water year starts on July 1 each year. The timing for a lower priority flow component may come up before a higher priority flow component, so planning delivery requires careful consideration of available water and the long term weather forecast.
This document has been designed to cover Water for the Environment in the Moorabool River. It conveys what environmental water is for, why it is important and how delivery is managed.
The Moorabool Stakeholder Community Advisory Group (MSAC) was established by the Corangamite Catchment Management Authority (CCMA) to provide feedback on water management planning in the Moorabool River from a whole of community perspective.
64 Dennis Street, Colac VIC 3250
PO Box 159, Colac, VIC 3250
Hours: 8:30am – 5pm, Monday to Friday
T: 1800 002 262
E: info@ccma.vic.gov.au
BARWON WATER OFFICES
Hours: 8:30am – 5pm, Monday to Friday
All mail must be sent via our Colac office
PO Box 159, Colac, VIC 3250
T: 1800 002 262
E: info@ccma.vic.gov.au
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