Upper Barwon River

The Barwon River rises in the Otway Ranges and flows through or near the townships of Forrest, Birregurra, Winchelsea, and Inverleigh, before flowing through Geelong and the Lower Barwon Wetlands to empty into the ocean at Barwon Heads.

The Leigh River, a major tributary, rises near Ballarat and joins the Barwon River at Inverleigh. Two other tributaries, Birregurra and Boundary Creeks, flow into the Barwon from the western part of the catchment. 

The Moorabool River is also a major tributary of the Barwon River, flowing southward from the Central Highlands between Ballarat and Ballan and joining the Barwon River at Fyansford. The waters of the Barwon flow through Traditional Owner Country of the Eastern Maar and the Wadawurrung peoples.

The Barwon River is a major water supply for Geelong and smaller urban centres, and is also an important farm water supply for the region. The system is significantly altered via extensive farm dam storages, on-stream reservoirs and many diversion licences. 

The West Barwon reservoir supplies a substantial percentage of Geelong’s Water supply, via transfers to Wurdee Buloc Reservoir. Grazing for livestock (beef, sheep and dairy) and forestry dominate the catchment, with 89% of the landscape zone dedicated to these practices, bringing significant economic benefits to the region. Sections of the Great Otway National Park and Otway Forest Park are also in the catchment.

The Upper Barwon Environmental Entitlement was established in 2018 and provides approximately 1,000 ML per year which can be released from the West Barwon Reservoir near Forrest. This is a small amount of water for a big system, but it is hoped that release of this water over summer will assist in maintaining flow and water quality. Releases can be made down both the Upper East Barwon River and the Upper West Barwon River to benefit both these reaches, but also to get water down to reaches past the confluence, towards Winchelsea.

Watering priorities 2019-20

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 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 dry period low flow, then dry period freshes, with the east branch prioritised over the west branch. Some water, approximately 500 Ml is reserved in case of drought. 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.

Summary of priority actions for 2019-20

Actions that are underway or complete are marked in blue, and also described in text below the table.

PriorityFlow ComponentFlow Objective
East Branch (reach 4)
1Dry Period (Dec-May) Low Flow (0.5 ML/d)Provide water in pools for habitat and to maintain food sources for fish and platypus. Provide adequate depth of permanent water in channel, with natural seasonal drawdown to promote recruitment of in-stream vegetation and to limit encroachment of terrestrial vegetation. Maintain a shallow water table with low salinity groundwater throughout the year.
2Dry Period (Dec-May) Freshes
(modified from 35 to 15 ML/d for 2 days x 2)
Provide water over riffles, and connectivity between reaches to allow fish and platypus to move between pools to breed, feed and find new habitats. Submerge and clean woody debris and hard surfaces to provide breeding substrate for fish. Sustain macroinvertebrate communities during the dry period. Provide a variety of differentially wetted areas within the stream channel, on benches and on lower banks and support growth on terraces, channel edge and lower bank to promote healthy emergent vegetation. Provide velocity to establish mixing and flushing of pools for water quality. Scour sediment from base of pools to maintain pool and to use bed sediments to scour algae from riffles and mobilise sediment from base of pools in order to improve and maintain abundance and condition of pools, large wood and riffles to provide structural habitat for macroinvertebrates and fish.
4Wet Period (Apr-Nov) low flow (10ML/d or natural)As dry season low flow, but also mobilise sediment from base of pools for a sustained duration to maintain channel capacity, shape and form, to support flora and fauna.
West Branch (reach 3)
3Dry Period (Dec-May) Low Flow (up to 30ML/d depending on water availability, but likely ~4ML/d to get through summer with remaining water, based on assumption of 1000 Ml available)Provide water in pools for habitat and to maintain food sources for fish and platypus. Provide adequate depth of permanent water in channel, with natural seasonal drawdown to promote recruitment of in-stream vegetation and to limit encroachment of terrestrial vegetation. Maintain a shallow water table with low salinity groundwater throughout the year.
5Dry Period Fresh (Dec-May) (modified from 100 ML/d to ~50ML/d for 6 days x 5)Provide water over riffles, and connectivity between reaches to allow fish and platypus to move and migrate between pools to breed, feed and find new habitats. Submerge and clean woody debris and hard surfaces to provide breeding substrate for fish. Sustain macroinvertebrate communities during the dry period. Provide a variety of differentially wetted areas within the stream channel, on benches and on lower banks and support growth on terraces, channel edge and lower bank to promote healthy emergent vegetation. Provide velocity to establish mixing and flushing of pools for water quality. Scour sediment from base of pools to maintain pool and to use bed sediments to scour algae from riffles and mobilise sediment from base of pools in order to improve and maintain abundance and condition of pools, large wood and riffles to provide structural habitat for macroinvertebrates and fish
6Wet Period (Dec-May) Low flow (modified from 100 l/d to 50 ML/dayAs dry season low flow, but also mobilise sediment from base of pools for a sustained duration to maintain channel capacity, shape and form, to support flora and fauna.

What have we done so far and what is coming up?

The water year starts on July 1 (like the financial 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.

A low base flow release of 5 Ml/d was commenced down the East Barwon just before Christmas. This is higher than listed in the table because we are trying to achieve 0.5ML/d by the end of the East Barwon, and currently have no way of gauging that flow. It also allows more water to get through past the confluence and down to places like Birregurra and Winchelsea. A small ‘fresh’ or pulse of water was also delivered in January to a peak of 15 ML/d. This did cause some localised flooding due to constrictions. A second fresh was trialled in March at volume reduced further to 9ML/d. Low base flow continues and river flow has so far been maintained through to Winchelsea over the summer period to date.

Supporting Documents