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Lake Grassmere / Kapara Te Hau
Lake Grassmere
Lake Grassmere
Location of Lake Grassmere
Location of Lake Grassmere
Lake Grassmere / Kapara Te Hau
Location in New Zealand Marlborough
Location Marlborough Region, South Island
Coordinates 41°44′S 174°10′E / 41.733°S 174.167°E / -41.733; 174.167
Type lagoon
Primary inflows none
Basin countries New Zealand
Surface area 17 km2 (6.6 sq mi)

Lake Grassmere / Kapara Te Hau is a New Zealand lake in the northeastern South Island, close to Cook Strait. The lake is used for the production of salt.


Lake Grassmere, 25 miles (40 km) south of Blenheim and 6 miles (10 km) south of the mouth of the Awatere River, is a shallow lagoon protected from the open sea by a single barrier beach covered by sand dunes. It is on the north-easterly extension of the Ward depression.

Covering an area of 17 square kilometres (6.6 sq mi), it has no natural inflow and is prone to strong warm winds. Close to the sea, it also has a very high salinity.

Because of these geographical characteristics, it is ideal for natural salt extraction. Grassmere has been divided into solar evaporation ponds. Seawater is pumped in, and moved between ponds over several months, increasing in salinity with each successive evaporation period. As salinity increases, crystallised salt forms and is extracted.

Grassmere's area varies between 3,500 and 4,400 acres (14 and 18 km2); this maximum is attained only in rare floods. The watershed is small. The climate, with a low average rainfall of 585 millimetres (23.0 in) and prevailing strong and dry north-westerly winds, provides Lake Grassmere with the suitable conditions required for natural economic salt production.

Early history

The Māori name for the lake is Kapara Te Hau ("wind-blown lake"). Early whalers on the coast rendered this name “Cobblers' Hole”.

According to Māori oral tradition, the lake occupies the site of early cultivations. Kupe, the navigator, is said to have poured salt water on these cultivations, thus creating the lake.

In pre-European times it was used as a ready source of food, as it attracts a wide range of waterfowl.

In 1832–33, a year after Ngāti Toa under the leadership of Te Rauparaha had defeated Ngāi Tahu at Kaiapoi and Banks Peninsula, Ngāti Toa visited the lake to take moulting ducks. A Ngāi Tahu force, having learned of this impending visit, laid an ambush. Scouts from Te Rauparaha's party found the locality apparently uninhabited and the canoes were driven ashore. On landing, the visitors were taken by surprise and sustained heavy casualties. Te Rauparaha was seized by Tūhawaiki, who was anxious to take him alive. The captive, however, after feigning resignation, was less tightly held. He then slipped out of his flax garment, swam to a canoe and made his escape.

Seismic activity

A fault running underneath Lake Grassmere triggered a magnitude 6.6 earthquake on Friday, August 16, 2013 at 2:31:05 pm. The quake was 8 kilometres (5 mi) deep and was strike-slip fault similar to the 2013 Seddon earthquake on July 21, thus considered a doublet earthquake.

Official name

The official name of the lake become a dual name as a result of the Ngāi Tahu Claims Settlement Act 1998.


A large range of salts with slightly different chemical compositions, grain sizes and shapes are produced at Lake Grassmere. All table salt produced in New Zealand is solar salt, and both iodised and non-iodised table salt are available.

Iodised salt contains added iodine (to prevent goitre) and silicon dioxide (to make the salt run). Specialty salts, including flaky salt, are also produced at Lake Grassmere.

Animal health products such as salt licks for farm animals are produced at Grassmere and Mt Maunganui.

At the end of summer Grassmere's gleaming white salt piles are easily seen from State Highway 1. This seasonal landmark forms a vivid contrast to the burnt brown of the Marlborough hills.

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