Watercare operates 14 water supply reservoirs, five of them located northwest of Auckland in the Waitakere Ranges, two near Helensville, four to the southeast in the Hunua 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 Waitakeres were made of concrete. After World War II they were built with earth and rock.
- The Hunua and Waitakere ranges receive about 1.8 metres of rain annually – about 50 per cent more than central Auckland.
Dams in the Hunua 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 65 per cent of Auckland’s water
- Built: 1951-1977
- Location: Headwaters of the Hunua River. Cosseys Dam is on the headwater of the Wairoa River.
Dams in the Waitakere Ranges
Raw water from these dams is piped to treatment plants in Huia, Titirangi and Swanson.
- 5 dams, 3 concrete, 2 earth
- Supply: about 26 per cent of Auckland's water.
- Built: 1907-1971
- Each dam is named after the stream that feeds into its reservoir.