Ōkārito Lagoon is a coastal lagoon on the West Coast of New Zealand's

South Island The South Island ( , 'the waters of Pounamu, Greenstone') is the largest of the three major islands of New Zealand by surface area, the others being the smaller but more populous North Island and Stewart Island. It is bordered to the north by ...

. It is located south of

Hokitika Hokitika is a town in the West Coast region of New Zealand's South Island, south of Greymouth, and close to the mouth of the Hokitika River. It is the seat and largest town in the Westland District. The town's estimated population is as of ...

, and covers an area of about , making it the largest unmodified

coastal wetland A wetland is a distinct semi-aquatic ecosystem whose groundcovers are flooded or saturated in water, either permanently, for years or decades, or only seasonally. Flooding results in oxygen-poor (anoxic) processes taking place, especially in ...

in New Zealand. It preserves a sequence of vegetation types from mature

rimu ''Dacrydium cupressinum'', commonly known as rimu, is a species of tree in the family Podocarpaceae. It is a dioecious evergreen conifer, reaching heights of up to , and can have a stout trunk (botany), trunk up to in diameter. It is endemis ...

forest through mānuka scrub to brackish water that has been lost in much of the rest of the West Coast. The settlement of

Ōkārito Ōkārito is a small coastal settlement on the west Coast, New Zealand, West Coast of New Zealand's South Island, southwest of Hokitika, and from . It is built at the southern end of the Ōkārito Lagoon at the mouth of the Ōkārito River. Th ...

is at the southern end of the lagoon.

Name

The lagoon's name is from the

Māori Māori or Maori can refer to: Relating to the Māori people * Māori people of New Zealand, or members of that group * Māori language, the language of the Māori people of New Zealand * Māori culture * Cook Islanders, the Māori people of the Co ...

, place of, and , the young shoots of the bulrush or

raupō ''Typha orientalis'', commonly known as bulrush, cumbungi, or raupō, is a perennial herbaceous plant in the genus ''Typha''. It is native to Australia, New Zealand, Malaysia, Indonesia, Japan, Korea, Mongolia, Myanmar, Philippines, China and th ...

(''Typha orientalis''), a valued food source. Another account has Ōkārito taking its name from a

rangatira In Māori culture, () are tribal chiefs, the leaders (often hereditary) of a (subtribe or clan). Ideally, were people of great practical wisdom who held authority () on behalf of the tribe and maintained boundaries between a tribe's land ( ...

named Kārito, whose daughters Mapourika and Wahapako gave their names to nearby Lake Mapourika and Lake Wahapo. The lagoon's official name has been spelled with macrons over the vowels since 2010, although it is still commonly seen written as "Okarito".

Geography

The lagoon is in area, mostly quite shallow. It is the largest

sandbar In oceanography, geomorphology, and geoscience, a shoal is a natural submerged ridge, bank, or bar that consists of, or is covered by, sand or other unconsolidated material, and rises from the bed of a body of water close to the surface or ...

-built

estuarine An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environm ...

wetland in the

West Coast region The West Coast () is a region of New Zealand on the west coast of the South Island. It is administered by the West Coast Regional Council, and is known co-officially as Te Tai Poutini. It comprises the territorial authorities of Buller Distri ...

– and the largest such unmodified wetland in all New Zealand – and is roughly in the middle of a series of wetlands that extends for 40 km, between the

Wanganui River The Wanganui River is in the West Coast, New Zealand, West Coast of the South Island of New Zealand. It flows northwest for from its headwaters in the Southern Alps, entering the Tasman Sea near Lake Ianthe, southwest of Hokitika. After hea ...

in the north and the Waiho River in the south. Around the lagoon is a low moraine ridge left by a glacier 18,000 years ago as it retreated up what is now the Whataroa River. Several small waterways drain into the lagoon, and it is the outflow of Lake Mapourika and Lake Wahapo via the Ōkārito River. At the southern end of the lagoon is the small settlement of

. The lagoon is tidal, with large stretches of mudflat being exposed at low tide, when reliable passage for canoes is only possible along a main channel. The channel forks into several streams and creeks that can be used to enter tall coastal and rainforest. Most of the lagoon is trackless and muddy and only accessible by boat. The lagoon is a dynamic system, driven by

seismic activity An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they ...

along the main Alpine Fault. In an earthquake, the

estuary An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime enviro ...

floor settles and deepens, but sediment from landslides is also washed down from the mountains, forming a spit which partly blocks the lagoon off from the sea and raises the shoreline. Tides cannot penetrate as far, and a

freshwater ecosystem Freshwater ecosystems are a subset of Earth's aquatic ecosystems that include the biological communities inhabiting freshwater waterbodies such as lakes, ponds, rivers, streams, springs, bogs, and wetlands. They can be contrasted with marine ec ...

forms, dominated by

around the water's edge. Sediment is deposited at the river's mouth as a delta. Over time, the arrival of sediment slows, the spit is breached and washed away, the water level lowers, and tides come further inland forming a

brackish water Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuary ...

ecosystem. During this stage Ōkārito's

forest is able to encroach around the edges of the now-lower lagoon, a pattern we can observe today.

Flora

Ōkārito Lagoon has extensive meadows of

eelgrass Eelgrass is a common name for several plants and may refer to: * '' Zostera'', marine eelgrass * '' Vallisneria'', freshwater eelgrass See also *'' Potamogeton compressus'', known as eel-grass pondweed {{Short pages monitor