The 210 km pipeline covers a region of southwestern NSW from the Menindee Lakes to the Murray River, and will save around 47 GL in evaporation and seepage through the replacement of the open waterway with a secure source of stock and domestic water.
The $28 million pipeline is part of the larger $54 million Darling Anabranch Pipeline and Environmental Flows project, an initiative to return some 460 km of degraded water course to a more natural ephemeral system.
It is the first major infrastructure project in the Murray/Darling Basin to provide significant water savings, improved water supply to landholders and enhanced environmental outcomes.
The overall project has three key stages:
1. Construction of a pipeline, pump stations and associated on farm works (now completed);
2. Modification and removal of instream structures to allow the free passage of environmental flows; and,
3. Reinstatement of an adaptively managed environmental flow regime.
Removal of the structures (Stage 2) is scheduled to be completed by June 2008. An environmental flows committee will develop the release rules and monitoring strategy for the management of environmental flows (Stage 3).
The provision of the new pipeline results in environmental benefits for the Darling Anabranch (including the removal of weirs and reinstatement of natural flow events) and improved water security for landholders.
Built by Mitchell Australasia, the PVC pipeline is buried at a minimum depth of 500 mm and follows existing roads, tracks and fences where possible. Pipeline diameter varies from 300 mm near the pump stations to 50 mm at the extremities of the system.
The pumps will deliver water into the main pipeline up to a maximum demand pressure of 1,200 kpa (174 psi) at a maximum flow rate of 90 L/s (45 L/s from each pump station). A total of 317 km of pipeline was installed with an average of 1.5 km installed per day by two crews.
Throughout pipeline construction, an Indigenous Employment Strategy was implemented, generating employment opportunities for indigenous people (eight on average) from the Dareton/Wentworth and Menindee areas.
* Installation of pump stations on the Murray River near Fort Courage (20 km downstream of Wentworth) and the Darling River at Polia Station.
* Installation of 330 km of main and spur pipelines, 360 km of on-farm pipelines and installation of 226 tanks and troughs. This provides a secure stock and domestic water supply for Anabranch landholders.
* An adaptively managed environmental flow to reinstate the natural wetting and drying regime for the 460 km of Anabranch stream.
* Removal of block banks and instream structures to allow an “˜end of system’ environmental flow.
In 2003/04, the Australian and New South Wales governments jointly invested $1.5 million through the National Action Plan for Salinity and Water Quality (NAP) to enable an Environmental Impact Assessment of the pipeline to proceed.
In December 2004, the Murray-Darling Basin Ministerial Council approved investment of $54 million towards the implementation of the project.
In September 2005 the NSW State Government got on board, with NSW Natural Resources Minister Ian Macdonald announcing the formal go-ahead for the pipeline. “The Great Darling Anabranch pipeline will deliver significant environmental benefits while delivering much needed certainty of supply to landholders,” Mr Macdonald said at the time. “That’s a good thing for the whole Murray Darling Basin, including the Macquarie River area, and it means there will be more water for the entire system.”
Mitchell Australasia was announced as the successful tenderer for the supply and installation of the lines, pump stations and storage tanks in February 2006. Construction commenced in mid-May and was completed in December 2006.
The pipeline was formally opened in February 2007. Federal Minister for Environment and Water Resources Malcolm Turnbull commended the members of the Darling Anabranch Management Plan Steering Committee for their foresight and determination in pursuing the construction of the pipeline.
“This project offers significant environmental benefits such as shifting stock watering points away from the sensitive banks of the Anabranch,” Mr Turnbull said.
Parliamentary Secretary to the Minister for Agriculture, Fisheries and Forestry Sussan Ley also welcomed the completion of the pipeline. “This new pipe will significantly cut evaporation losses and improve the reliability of water supply to properties along the Anabranch,” Ms Ley said.
The great Anabranch of the Darling River extends 460 km, from the Darling River 50 km south of Menindee, to the Murray River 15 km west of Wentworth. In its natural state, it is an ephemeral stream with intermittent flows.
Water for stock and domestic purposes has been supplied to the Anabranch since the 1960s, when the Menindee Lakes scheme was developed. Historically, almost every year a nominal volume of water – up to 50,000 ML – was released down the Anabranch from Lake Cawndilla.
This release is ponded in 17 weir pools where up to 3,000 ML/a is extracted by the 41 landholders adjacent to the Anabranch. Most of the remainder is accounted for by evaporation, uptake by riparian vegetation, and seepage. As a consequence of continuous ponding of water, the Anabranch is significantly degraded, water quality is poor and extensive areas of cumbungi infestation have developed.
The Darling Anabranch Pipeline and Environmental Flows project is an initiative to return some 460 km of degraded water course to a more natural ephemeral system. The project involves the construction of a stock and domestic water supply pipeline to supply landholder needs; the removal of in-stream structures from within the Anabranch; and the management of environmental flows from Lake Cawndilla to mimic a more natural flow regime.