NZ Farmer - Irrigation: What politicians need to know

Hawkes Bay hill country farmer and former Chairman of AgResearch, Sam Robinson, shares his thoughts about irrigation and water use.

These are my reflections on irrigation projects, including the retention of Crown Irrigation Investments Ltd, for the policymakers and politicians who are going to be running the country for the next three years. The intention is to balance the multiple one-liners, 10-second soundbites and vitriolic comments that sprang out of the water debate during the election.

  • Food is New Zealand's largest export by value.
  • Growing food depends on water.
  • Irrigation allows water to be applied at precisely the right time to optimise quality food production.
  • There is a strong correlation between irrigation and regional economic development
  • Irrigation allows further development of the existing food production value-chain from paddock to port.
  • There is not necessarily a correlation between irrigation and degradation of water quality.

1. Importance of irrigation to the economy

  • Food production for export is a fundamental building block of the economy. All food exports contain water, and reliable water is an integral aspect of modern food production
  • New Zealand is increasingly exporting quality foods to wealthy consumers. To meet these customer expectations growers need to be able to optimise all inputs, including water, required to grow various crops.
  • Irrigation allows further development of the existing food production value-chain from paddock to port. Economic benefit from irrigation schemes is widespread (particularly in the regions); including on-farm, towns servicing farms, processing enterprises, technical support and transport service industries including export ports.

2. Irrigation doesn't always lead to more dairy cows

  • An obvious example is the strong performance of the horticulture sector; both annual and perennial crops.
  • Both globally and within New Zealand there is an increasing trend for production of plant protein direct for human consumption. For example, there is currently a group of high net-worth individuals looking to invest significant capital in a New Zealand start-up company to produce plant protein for human consumption.
  • As we move to more sophisticated crops, water is required "just in time" rather than "just in case". There is a need for very reliable water. The application of water to land and crops has become much more precise.
  • Modern irrigation practices and (precision) equipment are leading to reductions of up to 20 per cent water usage per hectare. Over time, even greater efficiencies in water use are highly likely. R&D on this is occurring at He Puna Karikari (Ag Research's Lincoln hub). There is international interest in this research.
  • Because New Zealand is located in the southern hemisphere there is a good opportunity for us to grow out-of-season crops (including small seeds) for the northern hemisphere markets. These are sophisticated high-value crops that need reliable water.
  • Irrigation provides an opportunity for farmers to change land-use from more highly emitting dairy/pastoral use to lower emitting cropping/horticultural use.

3. Nutrient issues

  • Both society and the regulators (regional councils) are becoming increasingly concerned about water quality in our rivers. Limiting/prohibiting/taxing irrigation is a blunt instrument to control nutrient discharges to water/rivers. There are more precise methods such as regional plans, on-farm nutrient budgets (Overseer) etc to control discharges to waterways.
  • There has been a tendency to focus only on nitrogen as a measure of degradation of water quality in our waterways. This is simplistic and there are other factors that also influence water quality such as sediment, turbidity, E coli, phosphorus, water temperature etc
  • Most of Canterbury and part of Hawke's Bay (Tukituki) now have nitrate limits linked to land use consents that are specified down to individual property level. These are a form of "output control", rather than an "input control" (such as they tend to have in Europe for fertiliser and animal numbers etc). With the focus on "outputs", it encourages and allows farmers to continue to innovate and adopt the most efficient way of meeting their nitrate loss limits.
  • Using an irrigation levy (tax) to fund the clean-up of existing waterways is a very blunt instrument. There is often more harmful discharge to waterways (both direct and indirect) from dryland farms; particularly intensive cattle wintering which often occurs on non-irrigated farms. While not the subject of this paper, a nutrient levy/tax would seem to be much more precise and fair.
  • Farmers with reliable irrigation are able to apply precisely the correct amount of fertiliser to a particular crop in a particular season, meaning minimal excess available to leach into the groundwater. On the other hand, a non-irrigated cropping farm can only estimate the correct amount of fertiliser that will be taken up during a crop rotation. If the crop is grown in a dry year, excess fertiliser is left in the ground which will often leach into the groundwater in the following winter.

4. Environment and other issues

  • Where the water resource is limited it is probably more efficient to have a centralised (community) approach to designing, constructing and delivering water to individual farms. That way all farms are offered access to reliable water, rather than the "first-in-first-served" approach. A community scheme will also supply farms that don't bound a river. Keri Keri is a good example of this where in the early 1980s, with leadership from the Ministry of Works, two community irrigation dams were built in this water-short area. They now have a thriving kiwifruit industry, along with other horticultural crops.
  • Major Canterbury rivers are alpine fed. Their low-flow is mid-late winter and the high-flow is in spring-early summer. Canterbury irrigation schemes have traditionally been run-of-river, although as crops have become more sophisticated and reliant on the timing of water some community or on-farm storage is being built to overcome any irrigation-ban days that may occur in the autumn period. The cost of this storage is not a large capital cost in the overall scheme of things.
  • North Island rivers are not alpine (melting snow and ice) fed. Their low flow is late spring, summer, and autumn. Much larger scale storage is required, necessitating more capital. This front-end loading of capital makes it more difficult to establish community schemes in the North Island. Crown Irrigation Investments Ltd (CIIL) has a role to help with these more capital-intensive schemes.
  • On-farm storage dams are often touted as an option. There are some good examples where they have been successful. However, the prerequisites for successful on-farm storage are not always or even often available on all farms so much land will not have an opportunity to irrigate. On-farm dams are considerably more expensive to construct on a per cubic metre of water stored (3-6 times on a per M3 basis) than large community dams and they do inundate a lot of otherwise productive land.
  • On-farm storage supplying the same area of land as a large community storage scheme will not, by itself, reduce nutrient emissions from the irrigated area.
  • As we better understand groundwater, in many cases there are increasing concerns about abstracting from this source. Much of Canterbury is already over-allocated for groundwater extraction. Water storage in Lake Coleridge and delivered via Central Plains Water has dramatically reduced the extraction of groundwater in inland Selwyn district, which will improve spring-fed stream flow in downstream parts of the district. In Hawke's Bay's Ruataniwha basin some of the deep water is between 60-200 years old and it is unlikely that it will be sustainable to continue to take this for irrigation. Water storage is the most likely alternative source.
  • Scaled community irrigation dams allow the opportunity for establishing increased minimum flows, providing flushing flows, and with the use of reticulated scheme water there should be less use of natural groundwater leading to enhanced low-flows in spring-fed streams.
  • Future irrigation schemes that involve storage will be capital-intensive. All of this capital has to be invested at the start of the scheme.... it is not possible to stage the construction of a water storage dam. For a scheme of scale (say, more than 50 property owners) it is nigh impossible to get all landowners to agree on the same day to commit to invest in constructing a scheme. This is where CIIL contribution is important...... acting as "banker" until all eligible land has (inevitably) joined the scheme.
  • There is a clear need to address the claim that "irrigation degrades the environment". It doesn't - or at least doesn't if coupled with other now widely used regulations and controls. In fact, irrigation using stored water is lessening the pressure on groundwater and even contributing to lowland streams.

    Sam Robinson is a Hawke's Bay hill country farmer who has been involved in promoting the Ruataniwha Dam project.