Former Parliamentary Commissioner for the Environment Dr Morgan Williams says climate change is the single biggest risk to water systems.

New Zealand needs a minister for water Nelson-based scientist Dr Morgan Williams says, Cherie Sivignon reports.

A former Parliamentary Commissioner for the Environment wonders why there is no ministerial portfolio for water.

"Think about all the ministers [who] focus on areas important to society and the economy," Dr Morgan Williams says. "You've got ministers of health and education and transport and even horse racing ... but we've never had a ministerial portfolio for water."

MARTIN DE RUYTER/STUFF Ron Wastney kicks at dry ground that was the lake bed of Eastons' dam, near Nelson, in 2001.

The immediate response is likely to be that freshwater is a local government responsibility, he suggests.

"In a simple sense, that's correct but in a strategic sense, there's nothing more important to people than water."

That's not to say central government has kept away from water, Williams says, highlighting large hydro, irrigation and flood schemes along with some involvement in urban water for health and safety reasons.

BRADEN FASTIER/STUFF Surface flooding at Appleby, near Nelson, in mid-2017.

"But it's all been part of some other portfolio. So one wonders, and that's all I'm doing, has that contributed to our splintered approach to the way we think about water and the way we manage water and the way we value water."

Providing water for urban and industrial users is a big, expensive and often complicated task.

Williams says he believes the delivery of water is a local government function. "Recognising one size doesn't fit all."

However, he argues that in a strategic sense, it should be a central government function with central government investment to match.

"Getting it in the right place, securing it against things such as climate change, which is the single biggest risk to water systems in the coming decades ... that has to be [central government]," he says. "It's no different to having a national strategic approach and leadership in health."

Williams is a scientist with degrees in ecology from the universities of Canterbury and Bath, and an honorary doctorate in natural resources from Lincoln University. He has held research, policy and leadership roles for high-profile organisations throughout the South Pacific including the position as New Zealand Parliamentary Commissioner for the Environment for 10 years until March 2007.

Now living near Nelson, Williams holds several trustee and advisory positions. He is chairman of the World Wide Fund for Nature in New Zealand, the Cawthron Foundation and the Community Water Solutions Advisory Group, which was established to provide advice around the proposed Waimea dam.

Williams has a long interest in climate change.

In 1990, he was part of a group within the former Ministry of Agriculture and Fisheries that completed one of the first major studies on the potential effects of climate change on New Zealand agriculture.

"We've seen all of them now and faster than we ever dreamed of in 1990," Williams says. "Everything is shifting out. You get bigger wets and bigger drys and at the same time, the mean temperature is lifting the heat element."

Some areas were becoming wetter, such as South Westland while the east coast, particularly the east coast of the North Island and Canterbury, were becoming dryer.

The Nelson-Tasman region was experiencing both ends of the spectrum with "big wets and big drys" but extremes of weather were evident across the world.

"We're getting big drys, lots of heat with it: big fires. Big wets, lots of floods: enormous damage and it's just being repeated all over the planet."

Williams says he attended a forum in Germany about six years ago that brought together the heads of German industry with some ministers in the German parliament at that time. The speaker was the head of leading reinsurer Swiss Re.

"The thing that actually silenced the whole audience ... he was talking about his large research budget and his team, and what they were looking at in terms of their forward risks and the evidence for those risks and he said: 'Virtually all our budget's going into climate'."

When asked if he thinks climate change can be reversed, Williams says he believes "all we can do now is temper it".

He calls the British Climate Change Act 2008 a smart piece of legislation being talked about for New Zealand.

"It's smart because it puts in place a means of focusing on reducing emissions ... and adapting because it's very clear we're going to have to adapt and adapt fast."

Williams says the nub of that act is a requirement for five-year tranches of action within the British economy and society to reduce emissions, set at least 10 years in advance to put them outside the cycle of governments.

It was legislation that had majority support across the House. Other countries in Europe have similar laws either in place or on the way.

But New Zealand has been a "bit slow" on climate, Williams says.

"We've got a lot of very good people here, we know a lot about it. Yes, there's still unpredictables and yes, we naturally have a lot of variability but we do know now that our variabilities are going to increase and they're all increasing faster than we expected."