Federated Farmers has described an article in a major international magazine that finds fault with New Zealand's dairy industry as unfairly harsh.

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The Economist article blames cows for making 60 percent of the country's rivers and lakes unswimmable.

In the article headlined 'Dairy farming is polluting New Zealand's water', cows are labelled the main villains behind New Zealand's deteriorating water quality.

"Scrub where sheep once grazed is being given over to intensive dairy farms-some of them irrigated to help the pasture grow. Some 6.6m cattle are now squeezed into the country of 4.7m people, transforming even an iconic arid grassland, the Mackenzie Basin (made famous by the "Lord of the Rings" films), into a tapestry of emerald fields," reads the article.

But Federated Farmers' dairy chairperson Chris Lewis said farmers had been making changes to improve water quality and the article lacked substance.

"We're not perfect yet, but hopefully in the next 10 years we'll show some massive improvements in what we're doing. It's one of those things where we've hit rock bottom on public opinion a little bit but we haven't hit rock bottom on what we're doing."

The Economist said at many of the sites where the government tested the groundwater it contained too much nitrate to be safe to drink.