River water quality in Tāmaki Makaurau: Annual data summary 2024

Author:

Rhian Ingley, Nadia Dikareva

Source:

Auckland Council Environmental Evaluation and Monitoring Unit, EEMU

Publication date:

2025

Topics:

Environment

Auckland Council's online interactive Water Quality and River Ecology Data Explorer presents State of the Environment (SoE) monitoring data for rivers, lakes, groundwater and the coast. Groundwater quality data can be compared across the region, between aquifers and over time.¹

This report provides a summary of river water quality monitoring results for July 2019 to June 2024.

Key findings

Land use impacts stream health

Water quality was generally poorest in urban streams and best in native forest streams.
Streams within native forest catchments had smaller fluctuations in temperature, pH, and dissolved oxygen levels and lower concentrations of nutrients and faecal indicator bacteria compared with other streams, and metal contaminants were rarely detected.
Variation in turbidity and suspended solids concentrations between sites was better explained by biophysical units based on climate and geology than by land cover classes.

Water quality varies with seasons

There were clear seasonal patterns in several water quality measures though these patterns can vary between locations and peak concentrations may occur in different seasons. For example, dissolved forms of nitrogen were higher in winter than in summer at most, but not all sites, where higher concentrations were measured in spring.

Some issues are localised or site specific

There were specific issues at some sites and in some areas such as continued high nitrate concentrations in rural streams around Pukekohe; indications of wastewater contamination in Newmarket Stream and Botany Creek (East) with high nutrients and bacteria; continued high ammonia concentrations in Pakuranga Stream.

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1. This does not include the detailed statistical analysis that is required to assess trends in water quality over time and is reported in our five-yearly State of the Environment reports.

Auckland Council, June 2025