The Moorabool River flows southward from the Central Highlands between Ballarat and Ballan and joins the Barwon River at Fyansford. The Moorabool River, (Moorabull Yaluk) flows through Wadawurrung Country and has great cultural significance for Wadawurrung Traditional Owners.
The river’s catchment is heavily farmed, with about 75% of its 1,150km2 area used for agriculture. 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 Sheoks, as ‘wetting up’ and evaporative losses are minimised.
Watering priorities 2019-20
Watering actions (or flow components) are informed by FLOWS studies (conducted every 5-10 years), and are delivered in a priority order guided by the 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 low flow, then winter low flow, then the most critical freshes. Approximately 1000ML is kept in reserve in case of drought (Priority 1). This water is only released in small bursts during a drought to prevent loss of aquatic plants and animals, such as fish and platypus.
It should also be noted that complementary actions such as removal of choking weeds and fish barriers are needed together with riparian and channel restoration to gain maximum benefit from the delivery of environmental water.
In 2019 extra water was temporarily traded to the environment from Central Highlands Water and Barwon Water to the Victorian Environmental Water Holder. This has allowed more water for ecosystem health this year.
Summary of priority actions 2019-20
Actions that are underway or complete are marked in blue, and also described in text below the table.
|Priority||Flow Component||Flow Objectives|
|1||Trigger based freshes||Maintain minimum water quality for biota during critical risk summer period|
|2||Summer/ AutumnLow Flow (Dec-May) 5Ml/day||Maintain water quality for biota during critical risk summer period. Maintain habitats.|
|3||Winter/ Spring Low Flow (June – Nov) 5Ml/day||Allow fish movement and control intrusions by terrestrial vegetation.|
|4||Winter/ Spring Fresh event (Sep-Nov) 80Ml/day – 5 days||Upstream migration of Juvenile Turrpurt Galaxias, Tupong, Buniya Short-finned Eel and Grayling. Provide habitat connectivity between channels and pools for biota.|
|5||Winter/ Spring Fresh event (May – Aug) 80Ml/day – 5 days||Downstream spawning migration of adult Tupong.|
|6||Summer/ AutumnFresh event (April/May) 60Ml/day – 5 days||Downstream spawning migration of Grayling.|
|7||Summer /Autumn Fresh event (Jan-Feb) 60Ml/day – 5 days||Downstream spawning and migration of Buniya Short-finned Eel. Flush pools and remove biofilms.|
|8||Winter/ Spring Fresh event (Sep-Nov) 80Ml/day – 5 days||Upstream migration of Juvenile Turrpurt Galaxias, Tupong, Buniya Short-finned Eel and Grayling. Provide habitat connectivity between channels and pools for biota.|
|9||Little Summer/ Autumn Fresh event (Feb-Mar) 30Ml/day -3 days||Water fringing vegetation.|
What have we done and what is coming up?
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.
So far this year, thanks to the extra water traded into the environment, we have been able to deliver both priorities 4 and 5 to trigger important fish migration events. We are currently releasing an increased base flow of 10Ml/d and will deliver priorities 6,7 and 9 over the next few months.