Mangere Inlet is an arm of the Manukau Harbour

Manukau Harbour

Manukau Harbour is the second largest natural harbour in New Zealand by area. It is located to the southwest of the Auckland isthmus, and is an arm of the Tasman Sea.-Geography:...

, the southwestern of the two harbours of Auckland

Auckland

The Auckland metropolitan area , in the North Island of New Zealand, is the largest and most populous urban area in the country with residents, percent of the country's population. Auckland also has the largest Polynesian population of any city in the world...

, New Zealand

New Zealand

New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

 and itself an arm of the Tasman Sea

Tasman Sea

The Tasman Sea is the large body of water between Australia and New Zealand, approximately across. It extends 2,800 km from north to south. It is a south-western segment of the South Pacific Ocean. The sea was named after the Dutch explorer Abel Janszoon Tasman, the first recorded European...

. The inlet lies between the two cities of Auckland City

Auckland City

Auckland City was the city and local authority covering the Auckland isthmus and most of the islands of the Hauraki Gulf, in the North Island of New Zealand. On 1 November 2010 it was amalgamated into the wider Auckland Region under the authority of the new Auckland Council...

 and Manukau City and has a size of 6.6 km2 and a catchment of 34.5 km2, being considered to extend to just west of Onehunga (including where the Port of Onehunga is now situated). It is an environment highly modified by land reclamation

Land reclamation

Land reclamation, usually known as reclamation, is the process to create new land from sea or riverbeds. The land reclaimed is known as reclamation ground or landfill.- Habitation :...

 and human uses, with the northern shoreline especially affected. However, the inlet also acts as a natural sedimentation sink, thus being especially at risk of contamination.

It is surrounded by the suburbs of Te Papapa

Te Papapa

 - to the north-east  - to the east  - to the south  - to the south-west  - to the west  - to the north-west Penrose Mount Wellington Southdown Favona Mangere Bridge Onehunga...

, Southdown

Southdown, New Zealand

Southdown is an industrial suburb of Auckland City, New Zealand. The former main company in the suburb was the Southdown Freezing Works, part of a large industrial zone located near the main trunk railway at this point...

, Westfield

Westfield, New Zealand

Westfield is an Auckland suburb.This was once the site of the Westfield Freezing Works, part of a large industrial zone located near the main trunk railway at this point. The buildings were decommissioned during the 1980s & 1990s releasing large areas of land to be redeveloped as office parks...

, Otahuhu

Otahuhu

Otahuhu is a suburb of Auckland. It is located to the southeast of the city centre, on a narrow isthmus between an arm of the Manukau Harbour to the west and the Tamaki River estuary to the east...

, Mangere East, Favona

Favona

Favona is mostly industry-dominated suburb of Auckland, New Zealand, and is part of the Mangere area. The suburb is in the Manukau ward, one of the thirteen administrative divisions of Auckland city, and is under governance of the Auckland Council....

, and Mangere Bridge

Mangere Bridge, New Zealand

Mangere Bridge can refer to two places in New Zealand:*Mangere Bridge, New Zealand, a suburb of Auckland City*Mangere Bridge , the bridges that gave the suburb its name...

. The narrowest point on the Auckland isthmus

Isthmus

An isthmus is a narrow strip of land connecting two larger land areas usually with waterforms on either side.Canals are often built through isthmuses where they may be particularly advantageous to create a shortcut for marine transportation...

 is at Otahuhu

Otahuhu

Otahuhu is a suburb of Auckland. It is located to the southeast of the city centre, on a narrow isthmus between an arm of the Manukau Harbour to the west and the Tamaki River estuary to the east...

, where the coast of the Mangere Inlet is a mere 1200 m from the Otahuhu Creek, which ultimately feeds into the Hauraki Gulf

Hauraki Gulf

The Hauraki Gulf is a coastal feature of the North Island of New Zealand. It has a total area of 4000 km², and lies between the Auckland Region, the Hauraki Plains, the Coromandel Peninsula and Great Barrier Island...

.

The Mangere Bridge

Mangere Bridge

Mangere Bridge, officially also called the Manukau Harbour Crossing, is a motorway bridge over the Manukau Harbour in south-western Auckland, New Zealand, crossing between the suburb also known as Mangere Bridge and the suburb of Onehunga...

 crosses the western end of the inlet where it joins the main body of the Manukau Harbour. At this point the inlet is about 750 m wide. The Waikaraka Cycleway

Waikaraka Cycleway

The Waikaraka Cycleway is an off-road cycleway in the south of Auckland City, New Zealand, running from the Wesley suburb in southern Auckland City along New Zealand State Highway 20 to Onehunga and then continuing along the shoreline of the Manukau Harbour beside mostly industrialised areas until...

 also travels along the northern shoreline of the inlet.

History

Portage Road is the location of one of the overland routes between the two harbours (and thus the Pacific Ocean

Pacific Ocean

The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

 and the Tasman Sea

Tasman Sea

The Tasman Sea is the large body of water between Australia and New Zealand, approximately across. It extends 2,800 km from north to south. It is a south-western segment of the South Pacific Ocean. The sea was named after the Dutch explorer Abel Janszoon Tasman, the first recorded European...

), where the Maori would beach their waka

Waka (canoe)

Waka are Māori watercraft, usually canoes ranging in size from small, unornamented canoes used for fishing and river travel, to large decorated war canoes up to long...

 (canoes) and drag them overland to the other coast, thus avoiding having to paddle around Cape Reinga

Cape Reinga

Cape Reinga is the northwesternmost tip of the Aupouri Peninsula, at the northern end of the North Island of New Zealand. Cape Reinga is located over 100 km north of the nearest small town of Kaitaia. State Highway 1 extends all the way to the Cape, but until 2010 was unsealed gravel road for the...

. This made the area of immense strategic importance in both pre-European times and during the early years of European occupation.

In the 1850s, after settlement by Europeans, the areas around the inlet had become the agricultural centre of Auckland. Later industrial expansion westwards from the new railway line at Westfield

Westfield, New Zealand

Westfield is an Auckland suburb.This was once the site of the Westfield Freezing Works, part of a large industrial zone located near the main trunk railway at this point. The buildings were decommissioned during the 1980s & 1990s releasing large areas of land to be redeveloped as office parks...

 led to increasing discharges of contaminants into the inlet.

Environment

The inlet is highly man-modified, with three embayments at the inlets of historic streams having been lost along the northern shore, to a significant degree for use as landfill

Landfill

A landfill site , is a site for the disposal of waste materials by burial and is the oldest form of waste treatment...

s, and a loss of tidal inundation to the Hopua volcanic crater forming the Onehunga Basin further west. Ann’s Creek in the north-east still has a short section of open stream remaining in the north-east. Land reclamation in the 1960s for the Westfield

Westfield, New Zealand

Westfield is an Auckland suburb.This was once the site of the Westfield Freezing Works, part of a large industrial zone located near the main trunk railway at this point. The buildings were decommissioned during the 1980s & 1990s releasing large areas of land to be redeveloped as office parks...

 Rail Yards also reduced the inlet in the east, while the southern shore is less modified.

The area is generally known for relatively muddy, sedimented waters, which seem to predate human occupation of the area. Mangrove swamp

Mangrove

Mangroves are various kinds of trees up to medium height and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics – mainly between latitudes N and S...

 fringes are present around most of the shoreline, becoming less common west of Mangere Bridge.

For many years the many industries, from meatworks and abattoirs, to phosphate

Phosphate

A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...

 fertiliser works and other factories located here were discharging large amounts of untreated waste into the Manukau Harbour. This had a detrimential effect on the ecology of the harbour which at the turn of the 20th century had been a popular and attractive place to swim, sail, fish and gather shellfish. During the 1950s, the decomposition of organic wastes (including from residential areas and facilities like Middlemore Hospital

Middlemore Hospital

Middlemore Hospital is a major hospital in the suburb of Middlemore, Manukau City, New Zealand. The largest hospital operated by the Counties Manukau District Health Board, it offers tertiary-level care as well as a range of other health and social services for the Counties Manukau...

 into the mud flats led to sulphate reduction under anaerobic conditions - leading to complaints about hydrogen sulphide smells, and blackening of lead paint in the areas around the inlet. From 1962, the Mangere sewage works removed many of the household and industrial wastes that were previously discharged and led to significant improvements. As of 2008, a number of coastal protection zones had been established around the shores of the inlet.

However, industrial sewage mixed with stormwater overflows, and other contamination still leads to above-average traces of toxins like pesticides, insecticides, PCBs and copper in the mussels and oysters sampled by testing.

In the discussions around Stadium New Zealand

Stadium New Zealand

Stadium New Zealand, often called the Waterfront Stadium, was the provisional name for a national stadium proposed for Auckland's waterfront to host the 2011 Rugby World Cup. The stadium never advanced beyond a concept design....

, constructing the new venue over the eastern shoreline of the inlet was mooted by several architects as a potential alternative to the Auckland CBD

Auckland CBD

The Auckland CBD is the geographical and economic heart of the Auckland metropolitan area. Bounded by several major motorways and by the harbour coastline in the north, it is surrounded further out by mostly suburban areas...

location. They considered that the site would be far enough away from residential areas to suit the need for a large and busy multi-use stadium, but would also be able to be accessed easily by public transport (trains) and cars, more so than the CBD location. However, the idea failed to get public traction.