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.
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 nitrate levels in the bottom waters of 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 2013 to 2017 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
2013 to 2017
|Chlorophyll a (mg/m3)1||Clarity||<2||1.1|
|Secchi depth (m)||Clarity||>10||14|
|Total phosphorus (mg/m3)||Causes nuisance plant growth||<10||5.6|
|Total nitrogen (mg/m3)||Causes nuisance plant growth||<200||104|
There are concerns about the increasing amount of nitrogen (a plant nutrient) in Lake Taupō's bottom waters. Nitrogen levels have increased since the 1970s.
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.
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 19-year period 1999–2017 shows that the overall water quality of Lake Taupō did not change over this period, although concentrations of total nitrogen have increased substantially.
Environmental indicator - Lake Taupō's water quality