On this page:
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.
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 monthly average cell counts for blue-green algae in samples collected recently from sites along the Waikato River. Results are in cells/mL. The guideline value for contact recreation is 15,000 cells/mL. 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 |
Huntly |
Tuakau |
| Dec 09 |
<1,000 |
<1,000 |
<1,000 |
<100 |
no data |
30,000 |
| Jan 10 |
1,000 |
<1,000 |
<1,000 |
<1,000 |
<100 |
<100 |
| Feb 10 |
<1,000 |
2,300 |
1,800 |
<1,000 |
<100 |
9,200 |
There are no health warnings 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.
The table below shows cell counts for blue-green algae in samples collected recently from sites in shallow lakes in the Waikato region. Results are in cells/mL. The guideline value for contact recreation is 15,000 cells/mL. Results higher than the guideline are shown in bold. These results are provisional only. For more details contact us.
| Date |
Hakanoa |
Kainui |
Ngaroto |
Rotoroa |
Waahi |
Waikare |
Whangape |
| Dec 21 |
<1,000 |
30,000 |
5,000,000 |
no data |
79,000 |
600,000 |
5,600 |
| Jan 28 |
55,000 |
no data |
55,000 |
no data |
460,000 |
5,000,000 |
1,000,000 |
| Feb 25 |
247,000 |
78,000 |
172,000 |
6,200 |
684,000 |
5,400,000 |
2,000,000 |
Health warnings are currently in place for Lakes Hakanoa, Kainui, Ngaroto, Rotoroa, Waahi, 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.