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Lake Taupō’s water quality

Water quality for human contact recreation 

Waikato Regional Council measures bacteria levels (E. coli) in the water at a number of sites around the edge of Lake Taupō.

E. coli bacteria is a useful indicator of the health risk for human contact recreation activities such as swimming or water skiing. Water clarity is also important so that submerged hazards can be easily seen. See our monitoring site information for more details on results.

Water quality for ecological health

Waikato Regional Council’s monitoring of Lake Taupō’s open water quality shows the lake continues to be of high quality, clear and low in nutrients. However, increasing nutrient levels in the lake could lead to increases in algae, which can reduce clarity.

Waikato Regional Council measures Secchi depth at our open water sampling site to monitor Lake Taupō's water clarity over time. We also collect water samples in the top 10 metres of the lake at this site to measure chlorophyll a, total phosphorus and total nitrogen.

The table below gives their average values for the period 2014 to 2018 compared with typical levels for oligotrophic lakes in general. The results show that Lake Taupō currently has excellent water quality that is clear and low in nutrients.

Our glossary explains the importance of each different water quality measure.


Water quality measure Importance Typical levels Lake Taupō averages
2014 to 2018
Chlorophyll a (mg/m3)1 Clarity <2 1.1
Secchi depth (m) Clarity >10 14
Total phosphorus (mg/m3) Causes nuisance plant growth <10 5.1
Total nitrogen (mg/m3) Causes nuisance plant growth <160 98


Chlorophyll a

Chlorophyll a is measure of the amount of tiny free-floating algae (phytoplankton) in the lake's water.

The graph below shows monthly average levels of chlorophyll a in Lake Taupō's water, measured at our open water site. The peaks in the graph represent the winter months, which are the algal growing season. Increasing algae in the lake will reduce water clarity, although this also depends on the type of algae (which can vary between years) and the amount of other dissolved substances in the water.

Lake Taupō, deep-water site, monthly average chlorophyll a

Chlorophyll a graph 2014 2018

Chapter 3.10 of the Waikato Regional Plan aims to protect the long-term water quality of Lake Taupō by ensuring that it does not deteriorate from its condition in 2001 (actually, the 5-year period centred around 2001, namely 1999–2003). 

Using the methods outlined here for our shallow lakes indicator, analysis of the records of chlorophyll, Secchi depth, total phosphorus and total nitrogen for the 20-year period 1999–2018 shows that the overall water quality of Lake Taupō did not change over this period, although concentrations of total nitrogen have increased appreciably. 

More information

Environmental indicator - Lake Taupō's water quality