Recreation at Lake Horowhenua

A three-stage warning system is being used to minimise the health risks of blue-green algae to people who use Lake Horowhenua. The system recognises the different health risks posed by different activities on the Lake.

The current Lake Horowhenua Domain Board health risk level is:


The health risk levels are:

Health risk level

Lake use restrictions1


No restrictions apply.


Avoid algae scums.

No swimming or drinking.

Boating not restricted.


Lake closed to all use.

1.  Lake restrictions made by Lake Horowhenua Domain Board.

What are blue-green algae?

Blue-green algae are very small plant-like organisms that can build up to huge numbers under favourable conditions in lakes and oceans. They are part of the normal lake fauna, but are a cause for concern when there is a population explosion.  This has commonly occured in Lake Horowhenua during summer for many years. They cause health concerns in other lakes in New Zealand such as Lake Rotoiti near Rotorua.

Why are they a health risk?

Some blue-green algae carry toxic substances and have been linked to negative effects on human and animal health. The toxic substances can cause skin rashes, nausea, tummy upsets, and tingling and numbness around the mouth or tips of fingers. If toxin levels are really high, drinking the water could result in liver damage.

It seems sensible that the Lake Horowhenua Domain Board manage recreational use of the lake, rather than have anyone affected by the blue-green algae.