Prior to 2017, shareholders received their water allocation at zero pressure from an open channel network. These channels were the original Ministry of Works design and subject to an estimated 30% water losses through leakage and operational bywash. In February 2016, 95% of existing shareholders voted to proceed with a pipe upgrade for the Waiau and Balmoral schemes.
It was soon realised that significant financial savings could be made if the project was completed within a twelve month time period. In August 2016, Monadelphous Engineering NZ Pty Limited was awarded the contract for $60M for pipe supply and installation. The total budget for the upgrade was $85M and included works such as booster pumping, ponds, canals, pipe extensions and other associated costs.
The first sod was turned on the project on 19 September 2016. The design included 131 kilometres of pipe along four main pipelines (three from the Waiau scheme and one from the Balmoral scheme). 73 kilometres of the larger pipe (0.6-1.6m diameter) is glass reinforced polymer (GRP) pipe imported from Turkey. The remaining 58 kilometres of smaller pipe (>0.6m) is high density polyethylene (HDPE). The network includes 160 shareholder offtakes and crosses the Pahau River twice.
Prior to the pipe upgrade, AIC irrigated 22,175 hectares of land. In utilising the efficiencies from the pipe network, more water was freed up for further irrigation allowing greater utilisation of AIC’s full allocation of consented water. A share offer was held in July 2016 which was fully subscribed by new and existing shareholders resulting in an additional 4,700 shares sold. Now, 28,000 hectares is irrigated using the existing consented water. This includes 24,000 hectares from the pipe network and 4,000 hectares from retained water races.
The removal of 106 kilometres of water races and the installation of the pipe required the last 1,500 hectares of less efficient border dyke irrigation to be upgraded to spray irrigation which significantly reduced water use. Over the past ten years, shareholders have voluntarily converted over 15,000 hectares of land to spray irrigation through on-farm investment at an estimated $100M+ at their own cost.
The new network allows for improved water management through more accurate water allocation and recording as all turnouts will have a water meter installed.
Due to the >100 metres of fall west to east across the Amuri Basin, we can deliver water at 40 metres of pressure with only the western side requiring some supplementary booster pumping. The current peak pumping energy load is 9 megawatts and the upgrade reduces the energy demand from established irrigators by 80% or around 7.5MW, which for one irrigation season is equivalent to the average energy demands of 2,400 households.
Where possible we have looked to make efficiencies, such as using optimisation modelling which resulted in extra capacity being added into the pipes to ensure maximum pressure is fully utilised rather than being lost through the system.We have installed capacity for future hydro-electric power generation.
A link was constructed between the Waiau and Balmoral schemes to allow for transfer of water during times of water restrictions. A flow control valve allows a Waiau pipeline to receive water and additional pressure from the Balmoral scheme when it is available. Five shareholders have dual supply offtakes which allows these offtakes to be supplied by the Balmoral water at 40m pressure when surplus Balmoral water is available reducing energy consumption from running booster pumps.
Where booster pumping is still required we have worked to maximise opportunities for both AIC and shareholders. Nine combined stations have been built to boost scheme lateral pipelines as well as 32 individual stations which boost after the farmer offtake. By tailoring the stations to the needs of both AIC and shareholders and proportionally sharing capital expenditure and power costs we have reduced overall infrastructure investment and energy use by both AIC and shareholders.
We have built a buffer pond downstream from the Balmoral main pipe intake which captures any unused water as the pipe intake demand fluctuates. This is pumped to over 700 hectares of land ensuring that any unused water is utilised. The main intake site is on a hill with no space for a pond, but the same result was achieved on-plains further down the race. We have installed hydrants within the pipe network at strategic road junctions to allow for easy access to water for firefighting purposes.