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Little is known about the health impact of types of non-natural chemicals being found increasingly in New Zealand groundwater a new report on New Zealand's freshwater says.

The so-called emerging contaminants were not being monitored routinely, but a national survey of 29 of the chemicals in groundwater found the plasticiser bisphenol-A, active ingredients of sunscreen, and sucralose (an artificial sweetener) were detected most often. All were at low concentrations.

"The term emerging contaminants is used for non-natural chemicals in the environment when we know little about them or their effects on human health and the environment," the Our Freshwater 2020 report, produced by the Ministry for the Environment and Stats NZ, said.

A survey of 723 emerging contaminants in groundwater at 51 sites in Waikato found at least one type of emerging contaminant at 91 percent of the sites. Pesticides, pharmaceuticals, industrial waste, and food additives were the most common.

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Some emerging contaminants had been in the environment for a long time, the report said. New Zealand drinking water standards did not specify health limits for those compounds. Ecological guidelines were in place for a small range of emerging contaminants to manage their potential effects on ecosystems.

Many emerging contaminants that could be found in freshwater were suspected or known to present risks to human health, but were not commonly monitored in New Zealand, the report said.

As an example there were per- and poly-fluoroalkyl substances (PFAS), the import, manufacture and use of which were banned in 2011. PFAS compounds had been widely used, including in food packaging, non-stick cookware and in water-resistant products. They were also used in firefighting foams sprayed onto the ground at airfields and fire training sites for decades.

PFAS could remain in the environment for many decades and accumulate in plants and animals, the report said.

The report, published on Thursday, looked at four issues:
* threats to native freshwater species and ecosystems
* polluted water in urban, farming, and forestry areas
* how changing water flows affect freshwater
* how climate change is affecting freshwater

New Zealand's mountains were the source of 70 major river systems, the report said. Along with a multitude of streams, the country's rivers ran for more than 425,000km. There were 249,776 hectares of wetland and more than 50,000 lakes, about 4000 of them larger than one hectare.

Our Freshwater 2020 said most rivers and lakes in urban, farming and forestry areas were polluted.

The report's authors expected climate change would mean increased demand for water as agriculture was affected by droughts.

A more variable climate would make droughts and floods more likely. Floods could also affect the growth and yield of crops, along with the distribution networks needed to move goods to market.

"In dry years, more irrigation may be needed to make up for the lack of rainfall. Droughts are expected to increase the demand for water from agriculture and cause competition for this resource," the report said.

Demand was likely to be greatest in regions already drought-prone because those regions were expected to experience more frequent and intense droughts.

The area of irrigated agricultural land in New Zealand almost doubled between 2002 and 2017 from 384,000ha to 747,000ha, the report said. Irrigated land area rose in every region during that time, but much of the increase was due to the almost doubling of irrigated land in Canterbury (241,000 to 478,000ha).

Dairy farming accounted for 59 percent of irrigated agricultural land area in 2017, with other types of livestock farming accounting for 17 percent. The production of grain, vegetables, fruit, and other horticulture made up 24 percent.

Computer models suggested river flows were likely to increase on the west coast of the South Island and in rivers that drained the eastern side of the Southern Alps. Flows were predicted to decrease on the east coast of the North and South Islands, and in Waikato and Northland but those predictions were less certain.

MfE and Stats NZ said the report built on information in previous reports and went deeper on the issues affecting freshwater in New Zealand. It included new insights on the health of freshwater ecosystems, heavy metals in urban streams, consented water takes, and expected changes due to climate change. 

Report indicators and apps that help explain the findings and provide context are available on the Stats NZ website.

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