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Water Management

Managing the health of our rivers: Shoalhaven River environmental flows

The Department of Water and Energy has developed new environmental flow rules for the lower Shoalhaven River that will ensure more water is reserved for river health and better mimic the natural river flow.

The Department's work has advanced scientific knowledge of the Shoalhaven River and of the impacts of drought and water transfers on river health in general.

What are environmental flows?

The term 'environmental flows' refers to water that is protected from extraction or released from a dam or weir to maintain river health.

In the Shoalhaven, the environmental flow rules determine how much of the water flowing into Tallowa Dam must be released for the health of the lower Shoalhaven River.

What environmental flows rules are currently in place for the Shoalhaven River?

Interim environmental flow rules for the Shoalhaven River were implemented in 1999. These rules ensure that all natural inflows into Tallowa Dam up to 90 million litres of water per day are released for river health. In addition water spills over the dam wall when Tallowa Dam is full.

What are the new rules?

The new environmental flow rules will ensure more water is reserved for river health and better mimic the natural river flow. Under the new rules:

  • 100 per cent of low dam inflows less than or equal to the 80th monthly inflow percentile (between 150 million litres per day and 371 million litres per day) will be released for river health. The amount of water released will vary depending on the actual inflows into Tallowa Dam, to better mimic the natural flow variability in the river
  • 20 per cent of flows above the 80th monthly inflow percentile will also be released
  • Special purpose environmental flow releases could be made to address specific downstream river health issues. Importantly water will continue to spill over the dam wall when Tallowa Dam is full.

What improvements are expected?

To support the new environmental flow rules, new infrastructure will be built at Tallowa Dam to allow native fish passage and improve the temperature and quality of water released from the dam.

The new rules and dam modifications are expected to bring about improvements in:

  • The distribution of native fish species upstream and downstream of Tallowa Dam
  • Water quality, particularly temperature, which will benefit native plants and animals
  • Habitat and flow conditions, which could support the re-establishment of the endangered Australian grayling
  • The size of river flows, which will benefit canoeists
  • The length of the freshwater reach below Tallowa Dam, which will benefit swimmers and other recreational users.

How were the new rules determined?

An holistic approach was used when developing the new rules to ensure the water requirements of the entire river ecosystem were taken into account.

A broad range of scientific investigations were undertaken to better understand how ecological processes respond to changes in river flow and the likely implications for key ecological, social, economic and cultural heritage values.

Rules were selected that would best sustain those values and mimic natural river flow patterns.

Was the community consulted?

An extensive community consultation process was carried out, in partnership with the Sydney Catchment Authority (SCA). Consultation activities included:

  • Regular meetings with the Shoalhaven Community Reference Group and key stakeholder groups
  • Community newsletters
  • An information centre in Nowra
  • Roaming information booths in Nowra, Kangaroo Valley and Bowral
  • Public exhibition of a discussion paper and release of technical information
  • Advertisements and media releases
  • Publication of fact sheets and information in hard copy and on the DWE and SCA websites.

Comprehensive social, economic and cultural heritage assessments were also undertaken.

What's next?

The new environmental flow rules will be implemented when Sydney Water lifts water restrictions in Sydney and monitored under an adaptive management framework.

For more information contact us.

More information and publications

The following publications provide more detail on this work and the new environmental flows rules:

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