Use water pro rata: professor

Water users have a duty to the public to use the resource efficiently, so as not to disadvantage others in the community, United States water and environmental law specialist, Prof Joseph Sax, says.

Prof Sax, from the University of California at Berkeley, was a keynote speaker at the Resource Management Law Association Conference at the Dunedin Centre yesterday.

The US southwest had been struggling with water shortage issues for the past 150 years, so he hoped New Zealand, as it faced increasing demands for its water resource, could learn from some of its mistakes and successes.

"It's a problem being faced around the world, decisions on supply of water, as we feel the impact of global warming," the former counsellor to the US secretary of the interior said in an interview.

Water was important to economies around the world, but was also the best illustration of how people had a mutual obligation to each other: "We have to live with what we have."

Finding ways to better accommodate both public and private use was central to resolving the tension around the issue.

In the US southwest they had developed a forfeiture doctrine, which meant people were entitled to water they used efficiently rather than the volume of water on a consent - this based on the idea that water was a public resource, not property that belonged to someone, Prof Sax said.

What was not used went back for public use, such as maintaining fisheries or protecting the natural environment, he said.

"We owe a duty to the public to use it efficiently, to only use as much as we need so as not to disadvantage other people in the community."

To do this, good monitoring and accountability systems were needed; and reassessment of what entitlements were.

While people sometimes thought there was insufficient water to meet demand, if it were used efficiently communities would be better placed to actually meet demand, he said.

New Zealand should avoid the mistakes of the US southwest: of letting good fishing rivers run dry, of developing priority systems where the newest users lose out, and of not accommodating native people's rights at the outset, he said.