Using irrigation water more efficently

Irrigation pipes are saving 33 Mid Canterbury farmers hundreds of thousands of dollars in electricity bills and making their water go further reports Rural News. Ashburton Lyndhurst Irrigation Ltd (ALIL) yesterday officially opened an $8 million, 31km underground piped system, marking the culmination of a three year project to replace open races servicing 3500ha of light porous country between State Highway 77 and the north branch of the Ashburton River."˜The new piped scheme has huge benefits for both community and farmers given the electricity and cost savings and environmental benefits with more efficient and sustainable water use,' says ALIL chair John van Polanen. The pipes capture the energy of a 160m fall, removing the need for pumps and saving an estimated three million kilowatt hours of electricity a year. What's more, because over 15% of water was lost in leaks and evaporation from the open race system, piping has allowed a further 550ha to be irrigated. The pipes start at 1m, sufficient for up to 2000 litres/second (2 cumecs) tapering to 0.25m at the lower end. "˜There are four pressure reducing valves in the line to prevent the pressure becoming too great.' Electricity generation was considered at the design stage but returns didn't justify the extra capital cost, though that's not to say they won't in the future, says van Polanen.An extra annual charge of $130-$140/ha on the newly irrigated 550ha will repay and service a 30-year loan taken out by ALIL to pay for the project. ALIL is now commissioning a consultant to investigate opportunities to pipe water to more of the remaining 21,000ha in the scheme currently served by races.