Lake Taupo’s Water Quality (source Environment Waikato)

Environment Waikato’s monitoring of Lake Taupo’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.

On this page:

•  Increasing nitrogen

•  Increasing chlorophyll a

•  Decreasing water clarity

Environment Waikato measures Secchi depth at our open water sampling site to monitor Lake Taupo's water clarity over time. We also collect water samples in the top ten 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 1994 to 2001 compared with typical levels for oligotrophic lakes in general. The results show that Lake Taupo currently has excellent water quality, that is clear and low in nutrients.

Increasing nitrogen

There are concerns about the increasing amount of nitrogen (a plant nutrient) in Lake Taupo's bottom waters. Nitrogen levels have increased since the 1970s. Find out more about how nitrogen gets into Lake Taupo and how it could affect the Lake's water clarity.

Increasing chlorophyll a

Chlorophyll a is measure of the amount of tiny free-floating algae (phytoplankton) in the Lake's water. Levels of chlorophyll a in the Lake have increased between 1994 and 2001.

The graph below shows monthly average levels of chlorophyll a in Lake Taupo'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.

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

Decreasing water clarity

Lake Taupo’s water clarity has tended to fall over the last few decades. Minimum winter water clarity fell from 12 metres in the 1970s to 10 metres in 1998 and 1999 for the first time in the last 30 years.

The graph below shows the long term trend in minimum winter water clarity in the Lake. Winter values are used as this is the growing season for algae.