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Home >> Environment >> Natural resources >> Water >> Rivers >> Waikato River >> Algal blooms in the Waikato region

Algal blooms in the Waikato region

Photo of blue-green algal bloom in Lake Ohakuri
Blue-green algal bloom in Lake Ohakuri

On this page: Latest results, Waikato River, Lake Taupo, other Waikato lakes, contacts for drinking water concerns

Algae occur naturally in our rivers, lakes and streams, flourishing during hot and fine conditions such as those experienced in the summer of 2002/03. Most algae present in waterways are harmless, but high levels of blue-green algae may be potentially toxic.

In recent years blooms of blue-green algae have been reported throughout New Zealand due to favourable climatic conditions. Blue-green algal blooms are a common feature in some lakes in the Bay of Plenty region with high levels recorded most years. In the first few months of 2003, blue-green algal blooms were recorded in the Waikato River, Lake Taupo and several other lakes. In several cases this resulted in health warnings being issued. 

In early 2010 the Ministry for the Environment released new guidelines for measuring and assessing levels of blue-green algae in waterbodies.  Warning levels now take into account both the number of cells and their size.  This is referred to as the "biovolume" of blue-green algae.

More algal bloom information may be available in our media releases, and you can also find out more about algal blooms in our questions and answers page.

Latest results

Waikato River

Routine monitoring has continued in conjunction with several other agencies since late 2003. The key results from recent monitoring are shown below. Earlier data are available on request – please contact us

The table below shows the monthly average biovolume of blue-green algae in samples collected recently from sites along the Waikato River. Results are in mm3/L. The guideline value for contact recreation is 1.8 mm3/L. Any results higher than the guideline are shown in bold. These results are provisional only. For more details contact us.

Month Ohakuri Maraetai Karapiro Hamilton Tuakau
Jan 2014 <0.1 <0.1 <0.1 <0.1 0.2
Feb 2014 <0.1 <0.1 <0.1 <0.1 0.1
Mar 2014 <0.1 <0.1 <0.1 <0.1 <0.1

 

No health warnings are currently in place for the Waikato River.

Lake Taupo

As part of our routine monitoring of the water quality of Lake Taupo, we will continue to be on the lookout for blue-green algae in the lake.  If a bloom is detected we will undertake additional monitoring. 

No health warnings are currently in place for Lake Taupo.

Other Waikato lakes

Routine monitoring of levels of blue-green algae in several of the smaller lakes continues.  Hamilton City Council provides the results for Lake Rotoroa (Hamilton Lake).

The table below shows the biovolume of blue-green algae in samples collected recently from sites in shallow lakes in the Waikato region. Results are in mm3/L. The guideline value for contact recreation is 1.8 mm3/L. Results higher than the guideline are shown in bold. These results are provisional only. For more details contact us.

Date Hakanoa Ngaroto Rotoroa Waahi Waikare Whangape
30/31 Jan 0.2 1.0 0.5 0.5  10  48
27 Feb 1.1 0.2 4.5 1.4  7.0  9.3
27 Mar 0.7 1.9  12 1.1  3.2  37

 

Health warnings are currently in place for Lakes Ngaroto, Rotoroa, Waikare and Whangape.

Contacts for drinking water concerns

The Public Health Unit is working closely with local councils, including Hamilton City Council, to monitor drinking water standards.

If you’re concerned about health issues contact the Public Health Unit of the Waikato District Health Board on the freephone 0800 800 977. For queries regarding Lake Taupo or the upper Waikato River (from Taupo to Lake Maraetai) contact the Public Health Unit of the Bay of Plenty District Health Board on (07) 349 3520.

If you have any enquiries about your local drinking water supplies please contact your local district or city council.