Blue Lake, Nelson - world’s clearest lake

In a pristine New Zealand national park, the Blue Lake – also known as Rotomairewhenua – holds the title of the world’s clearest lake.

Scientific tests carried out in 2011 by New Zealand’s National Institute of Water and Atmospheric Research (NIWA) showed Blue Lake to be the clearest natural body of fresh water known to man.

According to the NIWA research results, visibility in the lake is up to 80 metres - meaning the water is considered almost as "optically clear" as distilled water.

Blue lake is characterised by blue-violet hues seen only in such clear natural waters.

Part of the Nelson Lakes National Park conservation area in the northern South Island, Blue Lake is fed by waters from nearby Lake Constance. The park is a popular hiking, fishing and destination. The lake is a two-day hike from the park boundary or, for an aerial view, there are scenic flights with Reid Helicopters.

Sacred waters

The spring-fed source of the water, and its 1200m altitude above sea level, just below the tree line of stunted mountain beech, ensures that Blue Lake is always cold, ranging between 5 and 8°C.

These astonishingly clear waters are regarded by the local Māori iwi / tribe as tapu or sacred, which means that humans are not permitted to enter the lake.

However, in early 2013, Danish photo-journalist and environmentalist Klaus Thymann was granted special permission by Māori, NIWA and New Zealand’s Department of Conservation to capture the clarity of the lake for conservation purposes.

Nelson Lakes National Park

Nelson Lakes National Park begins at the northern end of the Southern Alps - a grand series of mountain ranges that forms the South Island’s main divide. The port city of Nelson is the nearest main centre.

The national park, formed in 1956, covers some 1020sqkm, and is popular for camping, tramping and fishing.

Nelson Lakes National Park is characterised by impressive native beech forests, glacial lakes and rivers beneath craggy peaks. There are remote mountain passes to challenge the experienced solitude-seeker, but the lower reaches offer accessible hiking trails and overnight, camping and fishing.

The park is home to the Rotoiti Nature Recovery Project, which aims to revive populations of kiwi, other native birds and lizards.

Travers-Sabine Circuit

Blue Lake / Rotomairewhenua is on the multi-day Travers-Sabine Circuit track. The 80km hiking route through Nelson Lakes National Park reaches deep into the national park, through tranquil forests surrounded by 2000m peaks. Comfortable hiking huts maintained by the Department of Conservation are scattered along the track.

Images courtesy of Klaus Thymann of Project Pressure and supported by the Department of Conservation, NIWA and Tourism New Zealand.

Background: Blue Lake / Rotomairewhenua

  • Blue Lake is a side trip off the Travers Sabine Circuit multi-day track.
  • Blue Lake Hut accommodates more than 700 trampers annually - mainly through summer.
  • The clarity of the lake is being monitored to establish if there are any changes.
  • The waters of Blue Lake/ Rotomairewhenua are sacred to Ngāti Apa ki te Rā Tō Māori tribe.
  • NZ’s Department of Conservation asks visitors to respect the waters by not washing themselves, clothes or dishes in the lake.