Self-help Macquarie Settlement farmers partner with Water Dynamics to secure their future in the face of climate shifts

A partnership of Tasmanian farmers who privately funded their own irrigation initiative to help prevent recurring crop and production losses resulting from drought is now extending the benefits of their brainchild by upgrading and extending the Macquarie Settlement Pipeline in partnership with Water Dynamics.

The Macquarie Settlement Partnership, centred around Cressy, Northern Midlands, 25km south of Launceston, is one of several key water sustainability projects building the wealth of this predominantly agricultural region dependent on reliable water supply to optimise production in the face of climate shifts and river flow variability as stated by Rob Bayles chair of the Macquarie settlement partnership committee (MSP).

The major extension, now fully online in 2023, operates within the original annual water takeout, but is engineered to provide increased capacity when water is most wanted, as direct take summer water rather than winter storage options. The latest project, involving more than 11km of trenching, pumping and river feed work, has produced an increase in overall capacity to 75 ML a day, with more water and more reliable and controllable supply to local growers 19 farm groups that at the beginning of 2023 are part of the expanded scheme.

The latest project linking to the Poatina underground hydro power station in the Central Highlands follows the Partnership’s first big initiative, in the mid-2000s, which was also completed in conjunction with Water Dynamics, drawing on their national expertise as farm irrigation authorities, specialising in farm irrigation equipment supply and major installations in locations as diverse as the Apple Isle, Mt Gambier, Mildura, Yarrawonga and the Northern Territory.

Original Scheme

The original 14 irrigators in the Partnership invested in improving the surety of water supply to their land by a project to pipe water into the settlement area from the regulation pond below the underground six-turbine Poatina Power Station, situated on the Great Lake and South Esk River, which is the longest river in Tasmania.

Poatina generates 1,255 gigawatt-hours of clean green electricity annually, drawing on a 481 thousand cubic metre capacity dam located 30 minutes’ drive away in the Central Highlands.

The Partnership’s ambitious pipeline plan back then attracted the attention of Hydro Tasmania, which also contracted with Water Dynamics to construct a second pipeline in parallel with the irrigators’ but terminating at Lake River. This pipeline was built to enable the State body to meet its water supply obligations.

The original Macquarie Pipeline continues past Lake River and terminates at the Macquarie River, which carries the water further downstream for public and farm use. It extends 17 kilometres from the regulation pond, originally delivering 55 megalitres a day to the irrigators and 40 megalitres a day for Hydro Tasmania.

“This original project was a feat of engineering in its own right, because the two 575mm PVC main pipelines and the 375 branch pipeline splitting from them collectively across a public highway, five local council roads and one waterway,” said Rob Bayles (MSP).

A feat of engineering

The original scheme worked very well in its day, but circumstances changed over time. It was found that a major expansion was required to address issues such as higher demand and a transmission loss factor arising from the Macquarie River, which is the main conduit for conveying the irrigation water to farm pumping points.

The irrigated area has grown, and the Partner shareholding has changed over the years, so operational scenarios now are considerably different from the original design criteria. Plus, most of the discharge pumping and increased water use-points are a long way downstream from the primary discharge point. So the time for a water release from the primary discharge point incurred increasing delays, making planning and management difficult. Now, with the additional water release points, the water transmission loss has been reduced.

Brought up on the family farm, Jeremy has a solid understanding of agriculture and water requirements from a practical and technical aspect. He was on the spot when the time arose to extend the original Partnership scheme to deliver another 20 megalitres of water a day recycled from the Poatina Power Station.

The solution engineered by Water Dynamics’ Tasmania branch involved major works including the welding and laying 4.7 km of 630mm diameter poly pipe, 3km of 450 mm pipe and 1km of 375mm PVC pipe, duplicating the existing branch line. This required six pumps and six 450mm suction lines routed to the MSP pump shed shared with Hydro Tasmania.

Suction works were upgraded to a larger diameter, but retaining the existing pump station discharge pipe work, metering, and valving for cost-efficiency. Motor control was upgraded with variable speed drives replacing the previous soft starter arrangement, so current limiting and energy efficiency can be optimised.

“This then enables a number of future opportunities for lead pump rotation and the possibility of changing the system to a constant pressure system so the future discharge valves can be remotely operated to suit demand,” said Jeremy Cox.

Extensive use was made of Water Dynamics’ high efficiency pipeline technology available immediately on-site in Tasmania, with the assistance of local contractor Midlands plumbing for the excavation works and a new Ritmo all-terrain welding machine to complete the job in an efficient and timely manner.

This was complemented by a strong existing team of experienced Water Dynamics specialists, who were thoroughly familiar with the site, area, and client and water authority requirements. This knowledge bank and high equipment capabilities were major assets in achieving an on-time and on-budget outcome within the four-month window of opportunity they were given.

For product and sales information, please contact Rob Bayles
Chair of the Macquarie settlement partnership committee (MSP)
Water Dynamics
P 0418 137 667