The Environment

Egeria guide

Egeria in Christchurch

Surveying the Avon River for Egeria

Egeria is an invasive aquatic weed that has recently become established in Christchurch, New Zealand. It is known to be in the vicinity of Kerrs Reach, lower Avon River. It is likely that Egeria is present at other sites in Christchurch as well.
The Christchurch City Council is aiming to achieve a high level of control of Egeria to minimise its spread to other sites, both within Christchurch and in the wider South Island.

Why is Egeria such a problem?

Excessive weed growth in waterways effects recreation, ecology, drainage, aesthetics and economics.

In summer, Egeria grows right through the water column and forms a tangled mass on the surface of the water. The plants impede drainage and recreational use.

The dense canopy of Egeria also blocks light, which stops other plants from living in the same area. Dense Egeria stands decrease oxygen levels, especially at night, and this can cause problems for other aquatic life.

Harvesting aquatic weed is already a significant cost on many rivers in Christchurch. If Egeria becomes widespread, maintenance costs will increase and this will ultimately effect ratepayers.

What is the risk of Egeria becoming widespread?

Egeria could spread to suitable habits throughout the South Island, including many rivers and lakes. The high recreational use of the area where Egeria currently occurs greatly increases the risk of further spread.

What can I do to help?

If you are using boats, trailers or nets in an area with Egeria, clean them very thoroughly before putting them in the water again. Only 1 cm of plant is required to create a new plant.