Dams

Dam water comes from catchments high in the ranges

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Almost all of Auckland’s water comes from dams (manmade water storage lakes) in the Hūnua and Waitākere ranges.

Our aim is to capture as much water as possible so that Aucklanders can use water on demand, and to have water available for firefighting if required.

View dam levels

Where does the water come from?
What is the difference between water storage dams and hydro-electric dams?
Benefits from dams
Living downstream of dams

Fact file

Watercare operates 14 water supply reservoirs, five of them located northwest of Auckland in the Waitākere Ranges, two near Helensville, four to the southeast in the Hūnua Ranges, and one east of Papakura.  In combination the reservoirs are capable of storing over 100 million cubic metres of water.

  • The dams supply about 80 per cent of Auckland’s water.
  • Because the dams are located at high elevations, water flows easily to the city by gravity.
  • Earlier dams in the Waitākeres were made of concrete. After World War II they were built with earth and rock.
  • The Hūnua and Waitākere ranges receive about 1.8 metres of rain annually – about 50 per cent more than central Auckland.

Dams in the Hūnua Ranges

The water is piped to Ardmore Water Treatment Plant. It is then stored and carried through pipes, which are up to 1.9 metres in diameter, into reservoirs nearer the city.
  • 5 earth dams
  • Supply: About 60 per cent of Auckland’s water
  • Built: 1951-1977
  • Location: Headwaters of the Hūnua River. Cosseys Dam is on the headwater of the Wairoa River.

 

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Mangatangi Dam

Completed: 1977
Lake area: 185 hectares
Capacity: 35.3 gigalitres

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Mangatawhiri Dam

Completed: 1965
Lake area: 128.5 hectares
Capacity: 16.2 gigalitres

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Cosseys Dam

Completed: 1955
Lake area: 123 hectares
Capacity: 14.03 gigalitres

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Wairoa Dam

Completed: 1975
Lake area: 98 hectares
Capacity: 11.6 gigalitres
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Hays Creek Dam

Completed: 1967
Lake area: 18.2 hectares
Capacity: 1.1 gigalitres

Dams in the Waitākere Ranges

Raw water from these dams is piped to treatment plants in Huia, Titirangi and Swanson.
  • 5 dams, 3 concrete, 2 earth
  • Supply: about 20 per cent of Auckland's water.
  • Built: 1907-1971
  • Each dam is named after the stream that feeds into its reservoir.
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Waitākere Dam and Waitākere Saddle Dam

Completed: 1910
Lake area: 25.1 hectares
Capacity: 1.76 gigalitres

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Upper Nihotupu Dam

Completed: 1923
Lake area: 12.5 hectares
Capacity: 2.2 gigalitres

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Lower Nihotupu Dam

Completed: 1948
Lake area: 52.9 hectares
Capacity: 4.6 gigalitres

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Upper Huia Dam

Completed: 1929
Lake area: 21.4 hectares
Capacity: 2.2 gigalitres

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Lower Huia Dam

Completed: 1971
Lake area: 50.3 hectares
Capacity: 6.4 gigalitres

Helensville

Mangakura Dam 1 and Sandhills Weir supply raw water to Helensville Water Treatment Plant which supplies treated water to Helensville and Parakai.
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