Where our water comes from
Our main water supply comes from the Turitea Stream at the northern end of the Tararua ranges. It provides about two-thirds of our water.
The remainder comes from artesian wells, also known as groundwater bores. These supply separate systems in Ashhurst, Bunnythorpe and Longburn, as well as topping up the supply for Palmerston North and Linton.
There are currently six bores, with two more to come in 2018. They provide about one third of the city’s water on a normal day, and up to 50 per cent during the dry summer months.
We also store 17.5 million litres of treated water at Ngahere Park and the Aokautere Reservoir. The latter was commissioned in September 2017 to boost the reliability of the city water supply. Both these sites provide water for peak demand as well as emergencies.
In total, the Council supplies approximately 10 million cubic metres of water to residents a year. This includes industrial use, garden hosing, hydrant flushing, fire-fighting and any system losses.
Water from the Turitea catchment is chemically high quality, but not high enough to use directly. This is common in natural run-off from bush catchments as the water is slightly coloured, sometimes has large numbers of algal cells, and after heavy rain may contain silt and protozoans such as Giardia and Cryptosporidium.
The treatment plant removes the colour, algae and silt, and ensures the water is free from bacteria and protozoans. Ongoing monitoring shows that the treatment plant provides an effective barrier to these issues.
The quality of the artesian supplies is excellent, with the only treatment required being chlorination to neutralise hydrogen sulphide that is present naturally, and to provide residual disinfectant protection in the reticulation.
Fluoride is added at Turitea and the artesian stations. The level of fluoride in the water is maintained at between 0.7 and one part per million.
The Council's laboratory maintains a close check on the water quality from all our sources. Bacteriological and general chemical quality is regularly tested and samples are collected daily in different parts of the city for microbiological analysis.
Turitea water source
The Turitea Stream has a catchment area of about 2,400 hectares, largely covered in bush. The average rainfall is 1,400 mm per year. This area is run under the Turitea Reserve Management Plan.
A reservoir has been formed at the lower end of the catchment by constructing a dam across the stream valley. The storage capacity of the dam is 1.7 million cubic metres, which meets the city's average daily use for about 60 days.
Turitea water supply history and technology
Copies of these books are also available from our Customer Service Centre.
Turitea Water Treatment Plant
The plant is a full conventional alum-flocculation, rapid gravity dual media (pumice and sand) filtration type. It can also be operated in direct filtration mode during periods of low raw water turbidity, where the clarification process is by-passed.
The plant was substantially upgraded in 1999 and is now partly automated, requiring only one eight- hour shift a day to ensure continuous supply. Most of the plant functions are automated with the manual tasks mostly being cleaning and calibrating equipment, and replenishing chemical stocks. Turitea now produces water quality equal to the best conventional plants in the world, with final water turbidity typically at 0.02 Turbidity Units.
In times of peak demand, like weekday mornings, the mains from Turitea aren’t enough to supply the volume of water needed. To meet this demand, we draw groundwater to boost mains pressure. It comes from artesian wells, or bores, which are between 300mm and 450mm diameter and up to 250 metres deep.
Each location has its own pumping station. The pumps are controlled automatically, starting when local pressures fall below set levels.
Bore locations and numbers
- Keith Street (one)
- Papaioea Park (two, with a third bore to be commissioned in February 2018)
- Takaro Park (one)
- Roberts Line (two)
A new bore has been drilled on the corner of Railway Road and Roberts Line. Construction of the pumps and pipework is underway, with completion expected in mid-2018.
Under the New Zealand Building Code, water from the water network must not be able to return – or ‘backflow’ – to the system. Backflow can be especially dangerous if there is also a cross connection between a drinking water supply and a source of contamination or pollution.
Backflow can happen as a result of something as simple as a garden hose being left on in a bucket that has chemicals in it.
There are cases where public water supply has been contaminated with dangerous chemicals and other pollutants causing injury and illness because people weren’t aware of backflow.
Residential prevention measures
At home, you can reduce the risk by fitting an inexpensive hose tap vacuum breaker on outdoor hose taps. Available from your local plumber.
Commercial prevention measures
Commercial buildings with potential hazards must have adequate backflow prevention.
- hospitals and medical centres
- agricultural and horticultural operations
- points where portable water tankers are filled
- premises with boilers and cooling towers
- hairdressers and barbers
- some food preparation premises
If you’re not sure of the risks at your premises or business, call our Water Technical Officer on 06 356 8199