Annabeth Cohen: Time to modernise our farming systems

Annabeth Cohen is the Forest & Bird fresh water spokeswoman.

As this summer sets temperature records and the number of towns and farmers facing water shortages increases, it's inevitable that conversations will soon shift to what is perceived to be the obvious solution – build more dams.

Unfortunately, large-scale dams and associated irrigation schemes aren't the panacea many hope they will be. Few ever deliver on the well-intentioned promise of environmental benefits as farming intensification leads to reduced water quality. Many also fail to deliver on their promise of long-term net economic benefits.

Water storage dams might prevent shortages if we could just refrain from increasing our water use and hold that water until a drought occurred – but we don't.

This is because it would be too expensive to build an artificial lake we wouldn't use most years. In fact, it's often uneconomic to build an artificial lake that we do use every year – that's why so many of these schemes are taxpayer-subsidised.

Even with the support of public subsidies, an enormous intensification of land-use is required for farmers to generate the funds (or justify the loans) needed to buy water at those subsidised prices.

This is the crux of the water storage conundrum. We build dams to provide surplus water, and then use the surplus water to intensify agricultural land-use to pay for those dams – thereby leaving us with very little "surplus" water.

So large-scale water storage often exposes us to increased risk during drought – we end up with heavily indebted intensive farms relying on scheme-supplied water to maintain high levels of production.

When drought compromises the supply of that water, those who have invested the most on intensive farming are the worst off. Because so much extra capital investment is suddenly at risk, farmers look to protect their investment by overriding the environmental limits that protect the ecological health of our waterways.

The Opuha Dam in South Canterbury was built in response to several serious droughts in the late 1980s and early 1990s. The dam and its irrigation scheme saw a significant increase in capital investment and land-use intensification, but also a significant reduction in the area's water quality that affected recreational and in-stream ecological values, including fisheries.

In 2015 drought struck. Rather than protecting the scheme's water users - which was the scheme's whole point - all 250 irrigation takes were shut off when the over-committed Opuha dam reservoir dried up.

The following year there was another drought and summer takes were restricted by 50 per cent - no doubt adding to the many-hundred-thousand-dollar bill the taxpayer footed through Rural Assistance Payments to support those caught out.

That's not to mention the huge social and economic costs, and stress and uncertainty for those affected.

This summer has again seen high demand on Opuha's water. In order to allow farmers to continue their irrigation the scheme's operator has recommended a reduction in the environmental minimum flows of the local rivers.

Using dams to fuel water-intensive land-uses does not "drought-proof" our farms, or guarantee the environment will be protected.

Unfortunately the public's perception of water-storage schemes has been skewed by proponents' tendency to talk up the potential benefits, and largely ignore the negative economic and environmental impacts.

It's rare that an analysis produced by a developer will present an estimate of the environmental or public costs of a scheme, or the cost to the farmers should things not go to plan – such as happened with Opuha.

If alternative solutions to a dam are analysed (and they tend not to be), the studies often assume that communities will make no attempt to innovate in response to changing conditions – despite a long history of farmers profitably doing exactly that.

It is this kind of hubris that has led to so many proposals burning through millions of dollars of public money in the planning phases before collapsing when these crucial, but wilfully overlooked, aspects resurface.

Many solutions to the challenge of creating climate-resilient farming are already known. Farmers are already changing crop varieties, farming practices and land-uses to drought-tolerant alternatives that can produce both good economic and good environmental outcomes.

They are making their operations resilient by replacing drought-prone white clover with drought-tolerant nitrogen-fixing species such as lucerne. They are retaining shelter to provide wind protection which reduces both the drying of crops and soil erosion. They are also retaining soil moisture through increased organic matter.

A lot of farmers are busy exploring new solutions.

It may seem counter-intuitive, but expensive large-scale irrigation schemes are likely to increase our exposure to climate change risk rather than reduce it – when things go wrong, we're going to be hit even harder.

Instead of committing huge amounts of public and private resources to these risky schemes we should be supporting farmers to become more resilient and innovative by changing the way they manage their farming systems as they adapt to the changing climate.

In the long term if we try to fight nature it is nature that is going to win. Being smart and working with nature is the only way forward.

Annabeth Cohen is the Forest & Bird fresh water spokeswoman. Views expressed here are the writer's opinion and not the newspaper's. Email: editor@hbtoday.co.nz