“Is it wise to put  all our eggs in one dam basket?”

That’s the question asked by some farmers who would like access to irrigation water, but are concerned with the cost and environmental implications of the Ruataniwha Water Storage Scheme (RWSS). Are there alternatives that make more sense? How about having every farm with its own hen house….commonly known as on-farm irrigation storage.

On-farm storage schemes on the South Island illustrate the alternative.

Photo rendering of the Rangitata Irrigation Scheme

The last seven years has seen a surge in on farm water storage in Canterbury and now it’s revving up in Otago as well. Andrew Rae, design manager for Rooney Earthmoving Ltd, has been involved with many of the irrigation storage ponds and races constructed in the South Island. “On-farm storage provides the buffering or subsidiary storage for the larger intake ponds on the river. We use the fall of the land along the rivers to divert winter flows into a series of these large ponds and then the water is distributed through races to the participating farms. Cost calculations show that low tech river intake and on-farm storage has a cost savings over a larger dam where storage occurs only on one site.”

The Rangitata South Irrigation Scheme moving toward completion is an example. The scheme comprises 300 hectares of ponds up to eight metres deep beside the Rangitata River, providing 16.5 million m3 of water storage to irrigate 16,000 hectares through 70 kilometers of water transport races and 35 irrigation offtakes and meters. Each participating farmer needs to have 250m3 of water storage capacity for every hectare of land he intends to irrigate. According to Rooney Group, the price of on-farm water storage ponds works out to about $1.50 to $2.00 per cubic meter of capacity. The project value is approximately $82 million.

For farmers in Central Hawke’s Bay, there could be some striking benefits to this dispersed storage concept. Farmers would have the water they need for the season already on their farms and wouldn’t be vulnerable to the “Oops, sorry, we’ve run out already” scenario. The projects could be farmer driven, owned, and built strategically by adding on interlinked bits like a Mechano set, as demand warranted. It could reduce the environmental downsides of a huge dam structure which include: earthquake and flash flood risk, unnatural summer flushes of silt-laden dam water, and increased nitrate leachate from wholesale intensification of farming on the Ruataniwha Plains.

Strategic irrigation delivered through a farmer-driven community scheme would be less likely to change the balance of farming enterprises than the blanket irrigation approach of the proposed RWSS corporate investor mega dam. The HBRC reports estimate 75% of the farms in CHB will change hands within five years of the scheme starting, and that intensive dairying will increase by five times.

The RWSS would force farmers to contract to take a set amount of water every year. The intensification to justify that irrigation commitment will result in high capitalisation costs, ongoing debt costs and higher input costs. Those investors buying into potentially irrigated land will pay top dollar. Both these realities violate the basic rules of profitable business which are to buy land or initial inputs cheaply and to keep overheads low.

If commodity prices go down, farmers in the RWWSS scheme would be vulnerable because they are locked into a high energy use and cost structure business as costs rise and returns drop. This is what happened in the US in the 1920s and 30s, resulting in the Dust Bowl and thousands of bank foreclosures on farms. The smaller farmers fail first, and corporate interests move in to take advantage of the discounted land prices.

Do farmers really want to be pressured into committing to a project that forces them to buy water each year, needed or not, and is so expensive that they have to either intensify or sell out? Many farmers in CHB want a simpler solution. They want the ability to irrigate only 40 to 80 hectares of a summer crop to fatten lambs, or safely put in a barley crop as part of pasture renovation. They’d like water in a way that reduces their risks and increases their overall productivity without mortgaging the farm to the hilt.

On-farm storage is viable in hill country as well, not just on the plains. As Irrigation NZ chief executive Andrew Curtis recently commented in Straight Furrow (Oct 15): “There aren’t many hill country farms that haven’t got five or ten hectares of flat somewhere. It could definitely save your bacon in bad years.”

Storage ponds, similar to those on the Rangitata, alongside a river in our Ruataniwha basin could be filled from April to October by drawing water when stream flows are high. That water could then be distributed via races to on-farm ponds to be drawn down from November to March.

This approach could use the gravelly waste land that is often adjacent to rivers and streams in the area for the larger draw off ponds. In many places a natural embankment already exists that could serve as one side of those storage ponds. Less productive paddocks on farm or the awkward corners of centre pivot paddocks could be turned into storage ponds of about ten hectares surface area. A hectare of pond three metres deep provides 30,000m3 or enough irrigation water for ten hectares of land.

Farmer-controlled community water schemes could be created to undertake the withdrawal structures at stream-side and coordinate distribution of the water to ponds that farmers create on their own properties. Given the slope of the Ruataniwha Basin, it might be possible to have water intake points on several rivers or streams and arrange for interconnected races so that water could be gravity flowed, or even pumped, to eventually service the entire Ruataniwha Plains and equalise access to less expensive water.

River intake ponds and races are less complex and could be built quickly – in 12-24 months instead of the several years for construction of the proposed mega dam. That could mean that current irrigation wells in places like Ashcott Road, which are under water take restrictions when the Tukituki is low, could be fed water sooner directly into their bores so that they could continue to pump through their existing water infrastructure, quickly and without as much risk of being restricted or shut down. The surplus winter take might also be pumped directly into the aquifer to recharge that important underground body of water.

But what about the hassle of permitting so many ponds and races? Experience in the South Island indicates that with a well thought out plan that has universal farmer support, the permitting required by ECAN and the district councils has been minimal and pretty much hassle free. “It’s all quite simple, really,” says Andrew Rae of Rooney Earthmoving, “The councils see the advantages of these systems and are not creating permitting hurdles for the storage ponds.”

In contrast, the plan put forward by the HB Regional Council would preclude on-farm storage, in order to force farmers onto the dam scheme.

According to one CHB pastoral and cropping farmer, “We can increase productivity without a huge dam. Three to eight m3/hectare of irrigation water can provide a good economic return for farmers and encourage a return to cow/calf and breeding units which are needed for availability of animals for prime beef production. Find a way to distribute water that’s cheap for us to use so we can improve farm productivity and resilience in the current system. A shift to intensification of dairy/cropping exposes us to a huge risk that many don’t want. We can be rather more productive with just a bit more water.”

The HBRC says it’s already looked at on-farm storage and found that it’s too expensive at $3 to $6 m3, but their report is only several paragraphs of very general comments and undocumented costs. No thorough cost analysis of on-farm storage as it might be applied in CHB has been conducted, and the estimated figures cited by HBRC are disputed by leading contractors in the industry, as noted above.

Indeed, an on-farm storage option might end up being cheaper than the dam. That comparison, grounded in robust empirical analysis should be available today, but is not.

When you take on board the enormity of the environmental impacts and ownership changes that will happen with the mega dam, it’s worth looking closely at a lower tech, community-driven solution for water in the Ruataniwha Basin. And in fact, examination of such an examination would seem required by the Resource Management Act.

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