UPDATED 3.23pm The Government has set a target of making 90 per cent of New Zealand’s rivers and streams safe for swimming by 2040.

LISTEN ABOVE: Dr Nick Smith spoke to Larry Williams

That means all waterways will have to meet the safe standard for e-coli contamination 80 per cent of the time.

SEE ALSO: PM could lift freshwater standards today

Announcing the target in Auckland today, Environment Minister Nick Smith said 72 per cent of New Zealand’s rivers were currently “swimmable”, according to a standard used in Europe and the US.

Raising that level to 90 per cent would require cleaning up 10,000 km of waterways, and would cost Government, farmers and councils an estimated $2 billion.

SEE ALSO: Government needs to 'rattle its dags' on freshwater quality

It would be backed by national rules which require stock to be kept out of waterways and will make regional councils tighten their rules on sewage discharges.

Smith described the target as “ambitious” and said it recognised that New Zealanders expected to be able to “take a dip in their local river or lake without getting a nasty bug".

"New Zealanders expect to be able to go down to their local river, their local lake and have a dip. In many parts of the world, for billions of people that expectation is not there. If we allow the decline that we've allowed for the last hundred years we too would end up like those countries."

• Government needs to 'rattle its dags' on freshwater quality

SEE ALSO: Farmers a 'punching bag' in freshwater debate

The Green Party says the Environment Minister's swimmable standard is completely different to what most New Zealanders would consider swimmable.

It had hoped the Government would today answer the cries of 12,000 New Zealanders, who had signed a petition to clean up our waterways.

But water spokesperson Catherine Delahunty said all the Government's done is move the goalposts.

"We would have thought that far more rivers would have had to safe for swimming. Their e-coli, which is the bugs, would have to be around 260 but what the government's done is said 540 e-coli is excellent for swimming."

At present, the minimum standard for water quality in New Zealand is “wadeable”.

The standard will now be changed to “swimmable” – despite previous statements by Smith that this was not practical.

“It will return our rivers and lakes to a standard not seen in 50 years while recognising that our frequent major rainfalls mean a 100 per cent standard is not realistic,” Smith said.

The latest reports on water quality in New Zealand said around 60 per cent of rivers, streams and lakes were not safe for swimming.

But Smith said this was misleading because councils focused their monitoring on higher-risk sites.

The Government has used new data and monitoring to determine that 40 per cent of waterways were not suitable for swimming.

All livestock will have to be kept out of waterways within 15 years, Smith said.

“The rules progressively apply to dairy, pig, dairy support, beef and deer farms from this year to 2030 relative to the steepness of the country, at an expected cost of $367 million.”

Primary Industries Minister Nathan Guy said farmers are ready for the challenge.

He said it will mean putting in place 56,000 kilometres of fencing, which is enough to go around the world one and a half times.

Mr Guy said farmers have already voluntarily fenced off over 24,000 kilometres of waterways, because they know the impact livestock has on water quality.