Mixed trends in river and lake water quality indicators – Stats NZ news story

1 April 2026

Phosphorus levels showed improving trends but Escherichia coli (E. coli) trends worsened at many river sites, while overall lake health remained poor, according to figures released by Stats NZ today.

New Zealand’s river and lake water quality is described using a range of environmental indicators. Results show mixed trends, with some indicators improving and others declining.

Among the improving trends, total phosphorus decreased at 59 percent of monitored river sites between 2005 and 2024.

“Phosphorus occurs naturally at low levels in rivers. Lower phosphorus levels generally mean less risk of excessive algal growth,” environment statistics spokesperson Tehseen Islam said.

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