Toorale Water Infrastructure Project

Management of November 2019 flow event

Significant rainfall at Bourke and surrounds in early November generated a localised flow in the Darling and Warrego rivers. Flows into Boera Dam on Toorale began shortly after.

In response, the National Parks and Wildlife Services opened pipes at Boera Dam so inflows could be delivered to the Darling River in full.

The image (below) shows the first of the flow passing through to the Darling River at the site of the recently removed Peebles Dam.

The area around the junction of the Warrego and Darling rivers is part of Country for the Kurnu-Baakandji Aboriginal People. Toorale has extensive evidence of Aboriginal occupation and activity, including over 500 known Aboriginal sites. Artefacts recorded during 2018 have been dated at over 50,000 years old.

Toorale is associated with significant water management and engineering achievements including the Boera Dam and Floodwaters Scheme constructed by Sir Samuel McCaughey around 1892. This scheme was one of the most successful and large 19th century civil engineering and water management constructions known to be undertaken by a private individual in New South Wales.

The Warrego and Darling rivers and their floodplains on Toorale provide habitat for a diverse variety of wildlife and plants, including threatened species. When inundated with water, the wetlands along the floodplain spring to life supporting an abundance of native fish, frogs and waterbirds including pelicans, brolgas and the endangered Australasian bittern. The lush lignum that has established on the western floodplain provides some of the best habitat for waterbird breeding in the northern Basin. 

Studies have also highlighted the importance of the Warrego River for many of our native fish species. For example, the Warrego River is a significant source of golden perch to the Barwon-Darling system.

The Warrego River can be particularly important for the Darling River and its dependent communities in years when inflows from other rivers are critically low.

More information on the natural values of Toorale can be found at Commonwealth Environmental Water Office: Looking after Toorale's wildlife and plants.

Extensive ecological monitoring has been undertaken at Toorale. Annual monitoring results are available for the Warrego River and floodplain and the Darling River in annual reports at Commonwealth Environmental Water Office publications and resources.

Monitoring such as this will improve knowledge to inform decisions about relative environmental demands on Toorale and in the Darling River, to help balance water use.

The Australian Government’s purchase of 25,498 megalitres (ML) of Toorale water entitlements, as transferred to the Commonwealth Environmental Water Holder, comprised:

• 17,826ML in the Warrego River
• 7,672ML in the Darling River

The available amount of water that can be used under licence varies from year-to-year according to rainfall, inflows and catchment conditions.

A summary of how CEWO has used its Toorale water licences since 2008 can be found at History - Northern Unregulated Rivers (Intersecting Streams and Barwon-Darling).

In addition to the water returned through the purchase of licences, the regulating structures on Toorale are now managed to pass more of the total Warrego River flow to the Darling River than has been the case in the past.

Toorale has extensive infrastructure that was initially built to regulate water across the property for agricultural purposes. This includes water storage dams along the Warrego River that have altered the natural flow patterns. The remaining in-channel storages starting from the upstream end of the Warrego River are Boera Dam, Booka Dam, Homestead Dam and Peebles Dam.

Management of flows on and through Toorale is currently constrained by the capacity of pipes at each dam. Movement of native fish between the Warrego and Darling rivers is also affected by these dams, as they currently do not have fish passages on them.

When the flow down the Warrego River is larger than the capacity of pipes in Boera Dam, some water will spill onto the western floodplain. During larger flows, a portion of this water can return to the Warrego River from the western floodplain further downstream. Similarly, if flows are larger than the capacity of the pipes at Peebles Dam at the bottom end of the Warrego River, water can back up and flow into Ross Billabong rather than down the Darling River.

When Toorale was purchased, the NSW and Australian governments agreed to “demolish, remove, modify or decommission water infrastructure (on Toorale) to improve water flows for environmental purposes”. The Toorale Water Infrastructure Project is being undertaken to achieve this.

Such modifications to the infrastructure will give greater flexibility to share water between Toorale and the Darling River depending on relative needs, thus improving water flows for environmental and other purposes.

The Project aims to ensure that the important values of Toorale are maintained or enhanced, while achieving greater flexibility to pass more water to the Darling River in certain circumstances.

The Project objectives include:

• increase the maximum flow rate than can be delivered to the Darling River
• retain the capacity to divert flows from Boera Dam to the Western Floodplain
• maintain or improve the ecological values and processes for the Warrego and Darling rivers and connected floodplains
• improve fish passage connectivity between the Warrego and Darling Rivers
• minimise impacts to Aboriginal cultural heritage and support the recognition and maintenance of Aboriginal cultural values
• consider social and stakeholder values in the development of options, including adjacent and downstream stock and domestic water access
• minimise impacts to public road access and park operations
• consider recreational and aesthetic values.

The Project will be done in 2 phases:

Phase 1 – Removal of Peebles Dam

• Remove a section of the bank across the Warrego River to enable flows to pass unimpeded to the Darling River.

Phase 2 – Modifications to Boera, Booka and Homestead dams

• Install gated culverts at Boera Dam. The gates can be operated to either pass flow downstream in the Warrego River or out to the western floodplain. The new structure will increase the capacity to pass flows down the Warrego by at least 50 to 100%.
• Homestead and Booka dams will be modified to pass additional flow downstream by a “fill and spill” arrangement. These structures will not require any active operation
• Fishways to allow fish passage will be constructed at the three dams being modified.

Information on the current process for managing the Commonwealth environmental water holdings at Toorale can be found at Commonwealth Environmental Water Office: Portfolio Management Plan - Northern Unregulated Rivers, 2017–18.

In essence, a decision is made to pass as much water as possible to the Darling River (given existing infrastructure), or to share water between the river and the western floodplain. The first of any inflows are always passed to Darling River, in accordance with works approval conditions.

The new structures will allow for greater flexibility to meet the water needs of the environment and, in certain circumstances, downstream communities.  The proposed operating rules will prioritise flows to the Darling River when conditions are critically dry, while supporting floodplain values during higher sustained flows in the Warrego River or when the Darling River is flowing well.  

The new fishways will be operated to support fish movement between the Warrego and Darling Rivers during all flows.

The new structures and rules will be subject to approval from relevant government agencies.

The Project has engaged the Aboriginal community (represented by the Toorale Joint Management Committee), local landholders and representatives from local, state and Australian government departments. The proposal has been adjusted several times in response to issues raised and information provided.

Phase 1 of the project, the removal of Peebles Dam, commenced in early October as planned. It was completed ahead of schedule, on 29 October 2019.

The detailed designs for Phase 2 are being finalised and environmental assessment for this work has commenced. Pending approvals, the works will commence in 2020 and are due for completion in 2021.

See time lapse footage of the dam removal below.

The environmental assessment (called a Review of Environmental Factors) for Phase 2 is scheduled to be placed on public exhibition in January 2020. Anyone can make a submission on this assessment.