MONDAY, SEPTEMBER 18, 2017

Water tax by the numbers: A breakdown

Recent attempts to estimate the cost of Labour’s proposed water tax to farmers have demonstrated a basic lack of understanding of how irrigation works, says nonprofit membership body IrrigationNZ.

This issue, which is compounded by a lack of detail from Labour about how the tax would be applied, has resulted in some widely varying estimates. Radio New Zealand’s ‘Fact or Fiction’ series calculated the cost for irrigated farms at $13,800 a year, whereas figures from DairyNZ have estimated a figure of $45,000 a year.

On top of this, yesterday Jacinda Ardern told TVNZ there are 12000 farms in New Zealand and 2000 of them have irrigation. In fact according to Statistics NZ and the 2012 census there are 58,071 farms in NZ and 10,500 have consent for irrigation. Irrigation NZ estimates the number of irrigated farms is now at 11,000.

‘The public will rightly be confused by these very different figures,’ says IrrigationNZ Chief Executive Andrew Curtis. ‘But the lack of detail on how Labour would apply a water tax compounded with the sheer number of variables between farms - for example their size, what they produce, and how dry the region is, makes it hard to estimate with accuracy. While recent coverage has focused on the impact on dairy farms – just over half of our irrigated farms are not used for dairy – but for sheep or beef, arable farming, horticulture or vineyards. These farmers are growers who will also pay the tax.”

IrrigationNZ has spent the last decade developing a comprehensive suite of standards, codes of practice, guidelines and knowledge resources on irrigation, and now run over 50 training courses a year nationally. IrrigationNZ’s main focus is providing knowledge and training to help irrigators achieve excellence in irrigation.

‘Our figures, based on the average irrigated farm in Canterbury of 220 hectares, show an actual average cost of $24,000 to $29,000 a year (at 2 cents per 1000 litres). We’ve used Canterbury figures because there is no national average figure available for the size of an irrigated farm - but there is for Canterbury, where 60 per cent of irrigated land is.’

‘When this additional cost is put in context of the profit generated by a family farming business – it will create a significant impact, particularly for sheep and beef, arable and vegetable farmers who have reasonably tight operating margins.”

Mr Curtis adds that there will be larger farms and those farmers operating in drier climates who will be facing significantly higher bills of $40,000 to $50,000 or more.

Will non-irrigated farms pay?

While both Radio New Zealand and DairyNZ calculated water tax costs for non-irrigated farms, it remains unclear whether these farms would be paying the tax as it is unclear whether they would qualify as ‘large commercial users of water’. The only users mentioned by Labour are water bottlers and irrigators.

6% of New Zealand farms are irrigated (around 11,000 farms). Regardless of whether other farms may pay some of the tax costs, the majority of the tax will fall on a small subset of farmers.

Calculating a water tax on irrigated farms - key variables:

Type of farming - from dairy, to sheep, arable, or horticulture (DairyNZ’s figures were for dairy farms)
Size of farm
Amount of rainfall
Actual water use vs consented take
Number of days irrigation water is applied
The cost of the tax.

IrrigationNZ has been surprised by the growing number of irrigation experts in NZ.

‘Academics, economists and organisations that wouldn’t have the knowledge to turn on an irrigator are all offering their expert opinions on the cost of a water tax. Anyone talking about the potential cost of a water tax must have some basic understanding of water use by irrigators and not everyone offering an opinion currently seems to have that,” says Andrew Curtis.

‘We’d be happy to run a special course for the growing list of water tax experts - to help people to brush-up on their irrigation knowledge and assumptions.’

Calculating irrigation water use - the backbround

Before entering into the ‘how much will irrigators pay’ debate some basic knowledge of water use by irrigators is required.

‘The key piece of information is 1 mm of rainfall (noting rainfall is measured in millimetres not millilitres) falling over 1 hectare is equivalent to 10m3 which is equivalent to 10,000 litres). This provides some context around the sensationalist numbers being used by some parties around irrigation water use,’ says Andrew Curtis.

“For example over the Canterbury region (4.5 million hectares) an annual rainfall of just under 1,650mm or 74 trillion litres falls. However, we all know this isn’t distributed evenly and that’s why we need to irrigate – to provide additional rain for a crop to grow during dry periods. Under 500 mm falls at the coast, rising to 1,000 mm in the foothills and well over 2,000 mm in the mountains.”

For the 500,000 ha of irrigation in Canterbury (based on a seasonal allocation of 550 mm which is explained below) this means the maximum use for irrigation is 4.5 trillion litres or 6% of the annual rainfall.

“It is important to realise irrigators must hold a consent to take water for irrigation, and this contains a seasonal allocation expressed as a volume in m3. This volume is the maximum amount of water an irrigator is allowed to take and based on 80% application efficiency (the agreed industry standard) and 90% supply reliability,” says Mr Curtis.

Councils use a water allocation tool, such as Irricalc (http://irrigationnz.co.nz/practical-resources/irrigation-development/water-allocation-calculator/) to calculate a farms seasonal irrigation allocation requirements. These tools are based on a daily time step water balance model that uses the local climate and the farms soil water holding properties.

“However, when we case study an individual farm we always base it on the seasonal volume written on their consent – as this is the most likely method through which a water tax charge will be calculated,” says Mr Curtis.

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