New Zealand's rivers remain in a worrying state, with new data showing how levels of harmful E. Coli and nitrogen have been worsening over the past decade.

Multi-agency monitoring programme Land, Air, Water Aotearoa, or LAWA, today released updated water quality results for more than 1400 sites across the country, under nine different indicators, from between 2009 and 2018.

When measuring E.coli - the notorious bacteria linked to animal or human faeces that can leave swimmers suffering vomiting, cramping, nausea and diarrhoea - around 45 per cent of sites had been either "likely" or "very likely" degrading, while at another 21 per cent of sites, results weren't clear.

The picture for total nitrogen (TN) - a key nutrient linked to fertiliser, farm run-off and industrial waste that can fuel algae growth in rivers, leading to lowered light and oxygen that hurts species - were also dismal.

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About half of river sites showed worsening trends, while there wasn't enough data at 17 per cent of sites to say either way.

Under another critical measure of a river's ecological health, called the Macroinvertebrate Community Index or MCI, only a quarter of sites were improving.

Freshwater ecologist Dr Roger Young, of the collaborative programme's lead agency, the Cawthron Institute, said while there were more encouraging signs for other indicators like water clarity, ammonia, and phosphorus, the results for E. Coli, TN and MCI were "concerning".

"The mixed national picture suggests New Zealand has some way to go before meeting our aspirations to maintain or improve river water quality."

LAWA's river water quality lead Dr Tim Davie said while the national picture provided some interesting signals of changes, more could be learned by looking at the state of rivers at a catchment level.

"Site level information on LAWA is now richer than ever, because with today's update we've widened our offering to show 15-year trends where enough data are available," Davie said.

This graph shows how nine river quality indicators have been trending over time. They are: clarity, turbidity, total nitrogen (TN), total oxidised nitrogen (TON), ammoniacal nitrogen (NH4), total phosphorus (TP), dissolved reactive phosphorus (DRP), faecal indicator bacteria (E. coli) and Macroinvertebrate Community Index (MCI). Source / LAWA
This graph shows how nine river quality indicators have been trending over time. They are: clarity, turbidity, total nitrogen (TN), total oxidised nitrogen (TON), ammoniacal nitrogen (NH4), total phosphorus (TP), dissolved reactive phosphorus (DRP), faecal indicator bacteria (E. coli) and Macroinvertebrate Community Index (MCI). Source / LAWA

"This gives a longer-term view of changes to local water quality and for some locations represents up to 180 monthly sampling visits by a water quality technician."

Previous reports have shown how levels of E. Coli were 22 times higher in waterways in towns and cities than in the relatively unspoiled waterways that flow through our native wilderness.

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They were also nearly 10 times higher in the pastoral countryside that wraps around much of New Zealand's 180,000km of total river length.

The latest Government stocktake also showed that between 1994 and 2013 - a period that saw an explosion in cow numbers amid dairy's white gold rush - levels of nitrate-nitrogen in monitored rivers were getting worse (55 per cent) at more sites than were improving (28 per cent).

This month, the Government unveiled a package of proposed reforms to help turn the picture around.

They include new environmental standards that would effectively put the brakes on further intensification of dairy farms; a requirement for farmers to have "farm plans" by 2025 and more stringent rules around fencing and nitrogen loss, with some catchments facing having to cut rates by as much as 80 per cent over the next few years.

Councils would have to put the health and wellbeing of water first in decision-making, adopt tougher rules for wastewater discharges, use more monitoring indicators, and ensure swimming spots were at higher standards over summer.

Fish & Game New Zealand chief executive Martin Taylor said the new LAWA data showed why the Government reforms were so important.

"If intensive farming and urban waterways are not regulated, our kids will grow up thinking polluted rivers and streams are normal."

A recent Colmar Brunton poll conducted for Fish & Game New Zealand showed that pollution of our rivers and lakes remains a top concern for Kiwis, with two-thirds expecting the Government to put rules and regulations in place to protect water quality.

"Kiwis expect to be able to swim, fish and gather food from their rivers, lakes and streams. We have a once-in-a-generation opportunity to tackle an issue Kiwis are deeply concerned about."

• Today is World Rivers Day.