Clean drinking water is something most of us take for granted in New Zealand - or at least we did until the shocking outbreak of gastric illness in Havelock North left nearly 5,000 people ill for days.

The source of the contamination and how it got into Havelock North's water supply is not yet clear, although preliminary tests showed that the campylobacter that had contaminated the water supply came from cattle, sheep or deer.

While we don't yet know how the contamination got into the water supply, we do know that the risks to the health and purity of our rivers, lakes and underground water aquifers increase with the intensification of agriculture, particularly dairying.

If you want to see the results of rapid intensification, take a look at Canterbury. The spread of irrigation in recent decades has transformed the patchwork of mixed cropping and sheep grazing on the plains into an increasingly uniform bright green swathe of dairy pasture.

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Both Hawke's Bay and Canterbury are among the driest and most drought-prone areas in New Zealand and both rely largely on aquifers for drinking water. Both have braided rivers too, although those in Hawke's Bay are on a smaller scale than Canterbury.

A rush of irrigation over recent decades in Canterbury has led to significant environmental degradation, including serious contamination of some rural water supplies, loss of biodiversity and transformation of landscapes. Democracy has been damaged too, as development pressures led to the Government sacking the elected Environment Canterbury regional councillors and their replacement with appointed commissioners.

The commissioners promised to improve water quality. They have failed and water quality has continued to decline. Some rural water supplies, including Selwyn, Hinds and Hurunui, are contaminated with high levels of nitrogen and pathogens, leading to people becoming sick.

Canterbury now has the unenviable record of having the highest rate of campylobacter infections in the world, along with 17,000 notified cases of gastroenteritis a year and up to 34,000 cases of waterborne illness annually, according to Canterbury District Health Board figures.

Rates of animal sourced disease such as campylobacter are higher in areas of Canterbury with more intensive animal farming. A Canterbury District Health Board commissioned assessment of the proposed Central Plains Water Scheme found potential health risks to Cantabrians outweighed the probable financial benefits to a few people. Hawke's Bay should not make the same mistakes as Canterbury. It needs development, particularly in agriculture, that is sustainable and protects water quality and the other natural treasures that contribute so much to the region's quality of life.

The proposed Ruataniwha dam on the Makaroro River and its associated irrigation scheme will only lead to further degradation of the Tukituki River catchment. The Tukituki already has damaging levels of nitrates in some sections and the planned irrigation and agricultural intensification of more than 25,000ha of the Ruataniwha Basin can only send nitrate levels higher.

So it seems crazy to further damage the environment for a dam and irrigation scheme that doesn't appear to add up even in a narrow economic sense. Once the environmental damage is done, it will be difficult or impossible to undo.

Protecting water quality will mean protecting the native forests in upper catchments that help even out water flows - soaking up water in times of flood and steadily releasing it in times of drought. Looking after wetlands will also ensure better water quality and help protect from floods.

These natural protections will become even more important as climate change intensifies and they will help keep the region's aquifers full of good quality drinking water.
The measure of the health of Hawke's Bay's rivers will be if native fish can flourish in them and native birds and other wildlife flock to them.

Whatever the origin of the Havelock North outbreak, it should be a wake up call to take better care of our water. Healthy rivers that support nature will support the people of Hawke's Bay too.

Development in Hawke's Bay must be sustainable for the wellbeing of nature and for future generations of people. Hawke's Bay would not welcome a replay of the problems that plague Canterbury as a result of the rush to irrigation there.

We want to be able to swim in our rivers, catch fish in them and to be able to rely on safe drinking water. And we want to appreciate our rivers, streams and lakes and the native wildlife that live in and around them as our taonga.

■Amelia Geary is Forest & Bird Hawke's Bay regional manager.