Lake Grassmere
Lake Grassmere is close to Cook Strait in the northeastern South Island of New Zealand. The lake is used for the production of salt.
Geography
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.
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