Water Journal : Water Journal November 2015
NOVEMBER 2015 WATER 33 Feature Article An outback project on the edge of the Great Sandy Desert in remote Western Australia aims to transform mine dewater into an oasis of productive potential. The Department of Agriculture and Food, Western Australia (DAFWA) has embarked on a two-year $4.1 million project to explore the potential to harvest surplus mine dewater to grow a range of fodder and biofuel crops. The Woodie Woodie pilot project is part of DAFWA's Pilbara Hinterland Agricultural Development Initiative (PHADI), backed by the WA Government's Royalties for Regions funding. The 38-hectare Woodie Woodie pilot takes its name from the nearby Consolidated Minerals' manganese mine, which provides the dewater for the irrigation trial. The department has joined with the Mills family, veteran pastoralists from Warrawagine Station, who will host the trial on their 404,685-hectare station 190 kilometres east of Marble Bar, Australia's hottest town. The Mills have invested in two additional pivots at the Woodie Woodie pilot site and also provide in-kind support by keeping an eye on the equipment at the remote trial site. While there have been similar projects in the past in the Pilbara, this trial will undertake a full analysis of the potential to cultivate a range of crops under irrigation and make this knowledge available to use for future planning and investment decisions by government, industry and investors. The work will identify options and pathways to irrigated agricultural development in the Pilbara, providing pastoralists, agribusiness entrepreneurs and investors with new information. GETTING THE GREEN LIGHT The irrigation system's 'taps' were nally turned on in early September using surplus dewater from the Woodie Woodie mine, 10 kilometres away, which is discharged into Wet Creek and runs past the trial site. The project was temporarily delayed after an encounter with one of the risks associated with relying on mine dewater -- a change in the mine's operations saw dewatering rates uctuate and affect the water supply for the trial. There is no formal agreement with the mine connecting its dewater surplus to the irrigation supply; the mine has approval to discharge dewater into the creek, and the trial has approval to pick up water from that same creek. This highlights how using mine dewater for irrigation is closely linked to changes in mine operations, and the issues that can arise if dewater is the sole supply for irrigation. It's an interesting and important lesson learned and the authors want to share these project learnings with others so they can use this information to develop successful and sustainable irrigated agriculture. The mine recommenced dewatering in June and water is now owing down Wet Creek at a rate of more than 400 litres per second. DAFWA has extensively tested the quality of the water, which is 500--600 milligrams per litre of total dissolved solids (TDS) -- well within the parameters for agricultural production. The water for the trial is delivered through a high-density polyethylene (HDPE) pipe placed in a natural pool via three diesel-powered turbine pumps to the centre pivots. The rst pivot is supplied by 885m of 450mm diameter pipe, which continues a further 740m at 355mm diameter to the second pivot, and then 725m at 315mm diameter to the third pivot. Each pivot is powered by a 12kVA genset. AN ENGINEERING MARVEL The Pierce centre pivot was imported from the US, then transported from Perth to the Pilbara by road and assembled on site. It is 350m long and will irrigate 38 hectares at up to 15mm per day, based on low-pressure sprinklers to conserve energy. The absorbed pump power is about 40 kW, with another ve kilowatts absorbed by the diesel generator running the electrical system. The operation of the centre pivot was an engineering marvel. The controls are manipulated from the trial contractor Global Groundwater's headquarters in Perth, more than 1500 kilometres away. The equipment is monitored and can be manoeuvred remotely, while the owrate is tailored to each individual crop's needs. Injection rates of soluble fertiliser can be altered as required and the mix changed using owmeters and variable speed-drive motors on the injectors, via a computer control system. Average annual water use is expected to be around 23ML/ha but will vary, depending on the season and what each crop requires. THE WOODIE WOODIE IRRIGATION PROJECT Chris Schelfhout and Megan Broad report on the Pilbara Hinterland Agricultural Development Initiative to transform mine dewater to grow crops. Woodie Woodie pilot site construction.
Water Journal September 2015
Current Feb 2016