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Last reviewed: Thu, 15 Sep 2011

Where our water comes from



Christchurch's underground aquifiers mean residents continue to enjoy an untreated water supply from natural underground reservoirs.



In Christchurch, water is delivered into water mains by electrically driven pumps keeping the mains pressurised and charged. The pressure forces water out of the tap when you turn on a tap in your house.

Where reservoirs or large tanks are sited on hill areas, water pressure is maintained by continually supplying water to the level of the reservoir. In areas where there are no nearby hills to put tanks on, pumps are kept running to ensure a continuous water pressure 24 hours a day.

Water is taken from many wells around the city, sunk down into the natural underground reservoir. There are more than 50 places around the city where water is pumped into the pipe network. At each of these extraction sites there is at least one, and sometimes up to five, wells. These wells are typically 200mm and 300mm in diameter and are drilled down to depths ranging from 22–190 metres.

Although Christchurch appears flat, there is actually a significant difference in land elevation from the east to the west of the city. Up to five pressure zones are needed on the hills, depending on the height of residential development. In addition, the Christchurch City Council operates a small public water supply at Kainga and Brooklands.

The water supply network is controlled from a central room. As the pressure in the system falls and rises around the district, pumps are switched on and off by a combination of automatic and manual controls.

A vast network of pipes cover all urban parts of the city. This underground infrastructure spans from Belfast in the north to the hill suburbs in the south, and from Templeton in the west to Taylors Mistake in the east.

Over 1300 kilometres of main pipes are laid - enough pipes to run from Christchurch to Whangarei. The total length of underground pipework, including submains, is 1500 kilometres.

This network of pipes ensures that when a section of pipe has to be isolated for replacement or repairs, the number of households affected by stopped water supply is minimal. The main distribution pipes are made from cast iron (often lined with a cement coating), fibrolite, or plastic. The pipes distribute all of the water and provide water for Council-maintained fire hydrants on the main pipes.

 

Authorising Unit: Asset and Network Planning

Last reviewed: Thursday, 15 September 2011

Next review: Thursday, 15 March 2012

Keywords: water supply