Regional lakes

Lake Pupuke

On this page:

• About Lake Pupuke
• How did this lake form?
• How healthy is Lake Pupuke?
• Threats to Lake Pupuke
• What is the ARC doing?
• Technical Publications

About Lake Pupuke

Pupuke is roughly circular, about 1 to 1.3 kilometres across, with a shoreline that is about 4.5 kms long. It is the deepest of all the lakes that are monitored. Beyond about 10m the steep sides drop sharply to depths of more than 50m. In summer, the surface water gets much warmer than the bottom water. This creates distinct layers of water in the lake, each at a different temperature; an effect known as thermal stratification.

The lake is filled by groundwater, by direct rainfall, and by surface runoff from the surrounding area. There are no obvious streams or rivers flowing into or out of the lake. Water stays in the lake for a relatively long time, about 30-40 years.

Water is lost by evaporation from the surface and through an underground fissure on the eastern side of the lake that runs out to Thorne Bay and into the Hauraki Gulf.

The urban location of the means that it is a highly valued, popular recreation site. Power boats are not permitted.

It is regularly stocked with brown trout and rainbow trout: about 3000 were released by Fish and Game in 2007-2008. Other exotic fish, notably perch, tench, rudd, catfish and goldfish are found within the lake. Long and short fin eels are also numerous.

Black swan, mallard, grey duck, Australian coot, pied and black shag, heron, and New Zealand scaup can be seen the lake which is classified as a Site of Special Wildlife Interest by the Department of Conservation.

Between 1884 and 1944 Lake Pupuke was used as a water supply for Devonport. The old pumphouse can still be seen in Killarney Park.

Facts

Location guide	In North Shore City, north of the Waitemata Harbour, on the east coast of the North Island, New Zealand.  See a location map of Lake Pupuke
Surface area	About 110 hectares
Maximum depth	About 57m
Catchment area	About 105 hectares
Type of catchment	Pasture (none) Exotic forest (none) Native forest/scrub (7%) Urban (93%)
Surface water temperature	Average 19.4°C
Number of sampling sites	One site, but water samples are collected at three different depths.

How and when did this lake form?

Lake Pupuke formed as a result of volcanic activity about 140,000 to 150,000 years ago.

A lava lake, fed by a volcanic vent, produced many thin flows of basalt that overlapped to create a low volcano. When the lava withdrew back down the volcanic vent, the volcano is thought to have collapsed, creating a crater.

Later, some small volcanic explosions built up a low ring of ash and tuff around the collapsed crater while minor eruptions on the western side produced a mound of scoria. Eventually the collapsed crater filled with fresh water, creating the lake.

How healthy is Lake Pupuke?

Since 1998, the quality of the lake water has been monitored as part of our State of the Environment (SoE) Lake Water Quality monitoring programme.

The quality of any lake water is shown by its trophic state. Lake Pupuke is consistently eutrophic (green and murky, with higher amounts of nutrients and algae).

	Microptrophic	Oligotrophic	Mesotrophic	Eutrophic	Supertrophic	Hypertrophic
2006/07				x
2005/06				x

Threats to Lake Pupuke

The most significant threat to Lake Pupuke is the potential introduction of hornwort, New Zealand's worst invasive submerged weed.

Oxygen weed, another pest plant, rapidly colonised Lake Pupuke between 1980 and 1985 and is now the dominant submerged species.

Other introduced pest plants including eelgrass, ribbon weed, and tape weed also grow in the lake and the submerged vegetation is dominated by these introduced weeds. Eelgrass was deliberately planted in 1885 and quickly became a nuisance.

What is the ARC doing?

• In 2005, NIWA was commissioned to analyse the temperatures and changing levels of dissolved oxygen resulting from thermal stratification over the summer of 2004-2005 and to compare the results with earlier data.
• In 2006, the ARC commissioned NIWA to help develop a regional management plan for freshwater weeds and fish.
• The water quality is sampled once every two months as part of our State of the Environment (SoE) Lake Water Quality monitoring programme. Find out more about the Lake Water Quality monitoring programme.
• The ARC has operated and promoted the Environmental Initiatives Fund (EIF) since 1999. This support individuals and groups to improve and care for the region's natural, cultural and physical environments. Around $500,000 is available annually. Find out more about EIF.

Technical Publications

The ARC has a number of technical publications relating to this subject. Follow this link to see the full list of ARC technical publications.