Water starts flowing to farms from giant Central Plains Water irrigation scheme

Written by Heather Chalmers

Irrigation has spelled the end of brown grass and poor crop yields for Hororata farmer Campbell Tuer.

The mixed cropping and livestock farmer has gone from being a dryland farmer to irrigating 430 hectares virtually overnight as the tap is switched on the second and final stage of the massive $450 million Central Plains Water (CPW) irrigation scheme. 

"You'll never get another chance [to join the scheme]. You get sick of brown grass," Tuer said. 

CPW stage two supplied pressurised water to 150 connections, covering 20,000 hectares. In total, the scheme irrigates almost 50,000ha between the Rakaia and Waimakariri Rivers, inland of State highway 1.   

While other irrigation schemes notably Hurunui in North Canterbury and Hunter Downs south of Timaru, failed to get sufficient farmer funding to proceed and Waimea Irrigation, Nelson, was still working to secure sufficient finance after budget blowouts, CPW delivered its scheme on time and on budget.

Tuer, who farms with his wife Ingrid near Hororata, said having irrigation meant they could grow specialist crops like browntop (grass) and radish for seed for the first time. "We have grown cereals, but without water you can't get contracts for specialist seed crops."  

The last harvest was the worst they had experienced, after crops failed during a prolonged dry spell and extreme heat. 

"Irrigation is a big investment, but it cost us to grow crops last year." 

Autumn-sown feed wheat normally yields eight to nine tonne a hectare under dryland, but last season only produced five tonne a hectare. Under irrigation, yields should be at least 12 tonne a hectare.

Previously crops had to be autumn-sown to get established before the warmer months, but under irrigation the Tuers can grow more crops in a year and commit to buying in lambs for finishing with more confidence.  

More than $1 million was spent on buying nine centre pivot spray irrigators which can be turned on and off at the touch of Tuer's mobile phone. This investment was in addition to CPW construction shares and annual water supply charges.

Shelterbelts were cut down and fences removed to make way for the new irrigators, with the new farm layout halving the number of paddocks. 

CPW estimated that farmers had invested $187m in on-farm irrigation over the entire scheme. 

CPW general manager Derek Crombie said that stage two was fully commissioned and all its farmers had access to water ready for the new irrigation season. 

"It is a relief to finally get there. It has taken longer than anyone imagined. It is a project that is important, particularly to the Selwyn district, but to Christchurch as well."

The project had an average workforce of 177, with an average monthly spend of $9m.  

When construction started on stage two farmers had committed to shares equivalent to 15,500ha, with Crown Irrigation Investments, which was being wound down by the Government, taking up the shortfall.   

"Since we started construction, shares equivalent to another 2000ha have been purchased. We have a capacity of 20,000ha and we are getting up to that quite quickly.

"We are getting calls every week now from people that weren't originally interested, but now want to join the scheme. We thought it might take as long as 10 years to sell the shares." As the remaining shares are sold, CPW repays Crown Irrigation Investments. 

Greenpeace activists last year occupied a CPW construction site near Hororata, saying big irrigation schemes enabled more intensive farming, particularly dairying, further polluting waterways.  

Crombie said stage two was predominantly mixed cropping and sheep and beef and apart from a handful of farms unlikely to convert to dairying.  

By 2022, within four years of receiving CPW stage two water, dairy farms were expected to have reduced their nitrogen and nitrate loss by 30 per cent and dairy support by 22 per cent. Irrigated sheep and beef farmers must reduce by 5 per cent and arable by 7 per cent. 

Water was also expected to flow more often at Coe's Ford once a recharge project near Selwyn River gets underway, using water from CPW. 

Environment Canterbury chief scientist Tim Davie said the recharge project did not have all its required consents, but was expected to be operational in late winter 2019.

The main recharge period was expected to be during autumn and winter when the Selwyn River was not naturally flowing at the Bealey Road bridge. Infrastructure will be designed to recharge up to 3.5 cubic metres a second. 

"We expect to see more flow at Coes Ford and other spring-fed streams like the Irwell and Hart's Creek in future and it is far less likely to stop flowing. There is anecdotal evidence that Coes Ford dried up in the 1930s, well before there was irrigation on the Canterbury plains," Davie said. 

CPW provided an alternative water supply for Sheffield township and a back-up supply for Springfield. It had also installed 18 turnouts (connections to the scheme) as fire hydrants to help with fire fighting.   

CPW's annual water take equates to one single day of the Rakaia River flow, or 2 per cent.