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 

Most lakes in Auckland are in poor health

• 12 out of 13 (92%) of the monitored lakes in the Auckland region were in poor health.

Lake health differs between lake types

• Shallow, polymictic (well-mixed) lakes were in worse health than deeper, seasonally stratified lakes (where the water separates into layers between October and May).
  
• Nutrients, algae and turbidity were higher in polymictic lakes than in seasonally stratified lakes.

Stratification results in low oxygen and nutrient release from sediments

• Seasonally stratified lakes have prolonged periods with low oxygen an high nutrient concentrations in the bottom waters, suggesting nutrient release from lakebed sediments (internal loading) is occurring.

Risks to human health were low

• Cyanobacteria counts were low in publicly accessed lakes, but higher in other lakes.
• There are low levels of E. coli across all lakes in the region, but with episodic high results in lakes with high numbers of waterfowl.

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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

See also

Water Quality and River Ecology Data Explorer. Website for water quality data.

Water quality and river ecology data explorer methodology. Supplementary report

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Coastal water quality in Tāmaki Makaurau: Annual data summary 2024

Groundwater quality in Tāmaki Makaurau: Annual data summary 2024

River ecology in Tāmaki Makaurau: Annual data summary 2024

River water quality in Tāmaki Makaurau: Annual data summary 2024