Lake Grassmere
Coordinates: 41 ° 43 ′ 14 " S , 174 ° 9 ′ 51" E
Lake Grassmere is a lagoon on Clifford Bay near the Cook Strait in the northeast of New Zealand's South Island .
geography
Lake Grassmere is about 30 km south of Blenheim and 11 km south of the mouth of the Awatere River . It is a shallow lagoon, separated from Clifford Bay only by a narrow barrier covered by sand dunes. It is the northeasternmost part of the Ward Depression.
The area of the lake fluctuates between 14 and 17 km², the last value is only reached with infrequent floods. It has no natural inflow. The water has a high salinity due to its proximity to the sea.
The lake area has only a low annual rainfall of 585 mm. The prevailing strong, warm northwest winds favor evaporation.
Until the 1940s, the lake was a muddy surface in winter, and in summer the lake dried up, with occasional natural salt deposits. Because of these geographic conditions, the lake is ideally suited for the creation of salt gardens . The lake was therefore divided into evaporation ponds.
Towards the end of summer, the brilliant white salt mountains of Lake Grassmere are visible from New Zealand State Highway 1 and contrast starkly with the brown of the Marlborough Hills.
The small towns of Lake Grassmere and Hauwai are located on the lake . The Blind River flows into Clifford Bay about three kilometers south.
Early history
The Māori name for the lake is Kaparatehau ("wind-blown lake"). Early whalers corrupted this to "Cobblers' Hole".
According to the Māori legend, there were plantings at the site of the lake, which were doused with salt water by the legendary navigator Kupe , creating the lake. Before the discovery by the Europeans, the lake was used by the inhabitants to hunt the numerous water birds.
In 1832/33, a year after the Ngāti Toa, led by Te Rauparaha, had defeated the Ngāi Tahu at Kaiapoi and on the Banks Peninsula , the Ngāti Toa visited the lake to hunt ducks. A Ngāi Tahu force learned of the planned visit and set an ambush. Scouts from Te Rauparaha found the place apparently deserted, so the canoes were brought to the shore. On landing they were suddenly ambushed and suffered heavy losses. Te Rauparaha was captured by Tuhawaiki , who desperately wanted him alive. The prisoner apparently surrendered to his fate and was less closely guarded so that he could flee and swim to one of the canoes and escape.
Salt industry
The salt industry started at the lake in 1943 and now takes up a third of the lake area. In 1960 17,000 tons of salt were already being produced, and the total consumption of salt for industrial and domestic purposes in New Zealand was around 61,000 tons that year. In 1964/65, 30,000 tons were reached. The maximum possible annual production of the lake is estimated at 50,000 tons. In 2005, the lake covered around half of New Zealand's salt needs.
In 1970 the harvest reached almost 52,000 tons, but was no longer able to keep pace with growing industrial demand. A salt refinery was therefore built in Mount Maunganui , in which salt from Australia and the Caribbean is processed into high-purity salt for the food and pharmaceutical industries. A second smaller refinery was built in Grassmere.
In the mid-1960s a new type of evaporation basin was introduced that allowed rainwater to drain off before it had time to mix with the brine.
Sea water is pumped into the pools and circulated between the pools for several months, with its salinity increasing. Eventually the salt crystallizes out and is harvested.
A variety of salt products with slightly different chemical compositions, grain sizes and shapes are produced at Lake Grassmere. All table salt in New Zealand is obtained in salt pans. It is partially iodinated and as a flow aid with silicon dioxide was added. In Grassmere also be licks for agriculture produced.
In addition to the salt, smaller quantities of sodium hydroxide and gypsum are produced.