Water gives veges the green light
Vegetable production is set to expand in central Canterbury following the completion of the second and final stage of the massive Central Plains Water (CPW) irrigation scheme.
At a cost of $450 million, CPW is probably New Zealand's biggest privately funded infrastructure project, irrigating almost 50,000 hectares of the upper central Canterbury plains between the Rakaia and Waimakariri Rivers. CPW also estimates that farmers have invested a further $187m on irrigation.
While other irrigation schemes such as Hurunui in North Canterbury and Hunter Downs south of Timaru, struggled to get sufficient farmer funding to proceed and Waimea Irrigation, Nelson, is looking to cover budget blowouts, CPW has delivered its scheme on time and on budget. Stage two services 20,000ha, supplying pressurised water to farmgates. This is in addition to the 23,000ha irrigated in stage one and 4300ha in a Sheffield scheme on the upper plains.
Potatoes NZ chairman, Stuart Wright, whose farm received water from CPW in November last year as part of the Sheffield scheme, said there were a lot of opportunities to grow crops on better soils within the scheme which were previously non-irrigated. Development of crops was likely to generate new food processing industries in nearby centres such as Rolleston and Christchurch. And exports could go directly to Asia through Christchurch International Airport. “Already we have several North Island growers with a presence in Mid Canterbury and I can only see this continuing, especially as they come under pressure from population growth and urban sprawl around Auckland,” he said.
“With water, there are not many places better to grow crops than Canterbury.”
Darfield arable farmers Peter and Gretchen Redfern joined CPW to water a dryland block and reduce reliance on their existing groundwater take. Now watering 410ha, they previously irrigated 260ha, “but were always under-watered and looking for the next shower of rain”.
The Redfern family has farmed the property for 120 years, with their son and daughter-in-law Hamish and Janet the next generation to take up the baton.
“A lot of new irrigators will find the cost challenging, but there will be no more opportunities to acquire water,” Peter said.
“For this reason farmers had to commit to it and see where it takes them in the future. Canterbury could be growing
fresh vegetables for the world. People who don’t necessarily support irrigation have to realise that if we don’t continue to lift production and keep the price of food at a reasonable cost, where is the world’s food going to come from?
“Today’s irrigation applies such small volumes of water more often, that you never waste a rainfall. The irrigation technology today and soil moisture probes do a lot of keep the moisture level where it should be.
“A centre pivot can go around 100ha in a day and apply 4.5mm. So you are never getting the soil to a point where it won’t absorb rain. Earlier irrigators took five to six days to go around the same area, putting on 25 to 30mm.”
The Referns grow vegetable seed crops for export, including radish, carrot, corn salad and Chinese cabbage. Other seed crops are barley, ryegrass, white and red clover and cocksfoot.
“You can’t grow those crops without irrigation. Having water available at the right time is key,” Peter said.
To date, fears that CPW will lead to wall-to-wall dairy farms on the plains haven't eventuated, with only a handful of dairy conversions. Relatively flat dairy payout prices, as well as Environment Canterbury reducing limits on farm nitrogen losses are likely to keep a lid on dairy development. However, everybody acknowledges that it’s expensive water and farmers will have to make changes and become more intensive to make it pay.
The concept behind CPW was first introduced as far back as 1999, but it wasn’t until 2010 that resource consents were granted. Water for CPW stages one and two is sourced from the Rakaia River, while a 4300ha secondary scheme at Sheffield takes water from the Waimakariri River. CPW’s annual take equates to one single day of the Rakaia River flow, or two percent.
After initial plans for a water storage reservoir in the Waianiwaniwa Valley inland from Coalgate were rejected, CPW successfully negotiated with Trustpower to use stored water in Lake Coleridge. Earlier plans for a 56 kilometre headrace canal to run along the foothills between the Rakaia and Waimakariri Rivers were abandoned in favour of burying all infrastructure in stage two. Instead stage two uses 21km of buried large diameter 2.5 metre pipe for its central spine, as well as 180km of distribution pipework. Even now there is little to see of the scheme, apart from on-farm irrigators. >
CPW stage two has 150 shareholders covering 200 farms, and paying $2050 for each construction share, equivalent to a hectare watered. In addition, farmers pay an average water charge of about $800/ha, made up of $600 of debt and $200 of operating costs. The debt would be paid off over a 40-year term. In stage two, about half of its farmer-shareholders were existing irrigators, who will switch from groundwater to surface water from the scheme, with the remaining half new irrigation.
The district is predominantly mixed cropping and sheep and beef, with many properties farmed by the same families for more than a century. Arable research showed that an average difference in cereal yields of four tonnes a hectare over 10 years between irrigated and non-irrigated crops would cover the cost of irrigation. CPW figures show that irrigated farmland, on average, generates three times the production of an equivalent area farmed under dry-land systems. Studies on the economic effect of irrigated agriculture show that one third of the wealth and employment created from irrigation occurs onfarm, with the other two thirds spread through the rural and city communities.
CPW general manager, Derek Crombie, said farmer-shareholders are required to meet good farm management standards and complete a farm environmental plan.
“They can't get water until they have one.”
By 2022, within four years of receiving CPW stage-two water, dairy farms are expected to reduce their nitrogen/ nitrate loss by 30 percent and dairy support by 22 percent. Irrigated sheep and beef farmers must reduce by five percent, arable by seven percent and vegetable growers by five percent.
As CPW was in ECan's Selwyn-Waihora water catchment, designated as overallocated for water, the scheme was reducing pressure on groundwater resources. Groundwater consents in the district totalled 100 million cubic metres, but by 2016-17 only 15 cubic m was actually being used.
"So we are controlling nutrients on the one side and reducing groundwater use on the other," Derek said.
STUART WRIGHT ◀ Potatoes NZ chairman, Stuart Wright, said there are a lot of opportunities to grow crops on better soils within the scheme which were previously non-irrigated.
Having water available at the right time is key.PETER REDFERN
▴ Stage two of the Central Plains Water irrigation scheme uses 21km of large diameter pipe, rather than an open canal, so that all infrastructure is buried.
▴ The main water channel goes from an open canal to a buried pipe in stage two of the Central Plains Water irrigation scheme.