Canty irrigation scheme on target
With reliable irrigation, farmers can grow more high-value crops and have better yields. Heather Chalmers takes a closer look at the massive new irrigation scheme in Canterbury.
Stage two of the massive $200 million Central Plains Water (CPW) irrigation scheme is on schedule and budget to supply water from September 1.
Covering the upper Canterbury Plains between the Selwyn and Waimakariri rivers, stage two will service 20,000 hectares supplying pressurised water to farm gates. This was in addition to the 23,000ha irrigated in stage one.
A key difference from stage one was that stage two will use
21 kilometres of large-diameter
2.5-metre pipe for its central spine, instead of continuing the open canal, so that all infrastructure will be buried, CPW managing director Derek Crombie said.
‘‘CPW is 95 per cent through construction and down to final commissioning and testing and farm connections. So we are on track to be ready for irrigation from September 1.’’
The central spine piping was fully installed and 180km of distribution pipework was also in the ground.
Costing a total of $450m for the two stages, resource consents and planning, CPW had been a big employer for the district.
‘‘An average of 150 people have been employed for the last five years as the two stages were built. We’ve been spending an average of
$9m a month since we started.’’ CPW stage two had 150 shareholders covering 200 farms, which had paid $2050 for each construction share, equivalent to a hectare watered.
In addition, farmers pay an average water charge of about $800 a hectare, made up of $600 of debt and $200 of operating costs. The debt would be paid off over a
40-year term.
‘‘The next generation will be very thankful,’’ Crombie said.
Digging a trench 7 metres deep, to lay pipes across the Selwyn River, had been challenging during a wet winter. The main water channel was diverted to one side, so pipes could be laid on the other.
‘‘You go out there today and there’s nothing to see – it’s all buried.’’
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 was predominantly mixed cropping and sheep and beef and, apart from a handful of farms, unlikely to change to dairying.
‘‘The area north of the Selwyn River has good-quality soils and far more valuable for cropping and not that suitable for dairying.
‘‘The probability is that area will become more intensive cropping and maybe some sheep and beef as a backstop.’’
With reliable irrigation, farmers could grow more high-value crops and achieve more consistent yields.
Greenpeace activists last year occupied a CPW construction site near Hororata, saying big irrigation schemes enabled more intensive farming, particularly dairying, further polluting waterways.
‘‘An average of 150 people have been employed for the last five years as the two stages were built. We’ve been spending an average of $9m a month since we started.’’
Crombie said farmershareholders were 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 were expected to have reduced their nitrogen/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.
As CPW was in Environment Canterbury’s Selwyn-Waihora water catchment, designated as over-allocated for water, the scheme was reducing pressure on groundwater resources.
Groundwater consents in the district totalled 82 million cubic metres, but in 2015, just before stage one started, only 21m was actually being used. By last year this had dropped to 15m.
‘‘So we are controlling nutrients on the one side and reducing groundwater use on the other,’’ Crombie said.