Drinking water

• Kaikōura District Council
• Hurunui District Council
• Waimakariri District Council
• Christchurch City Council
• Selwyn District Council
• Ashburton District Council
• Timaru District Council
• Mackenzie District Council
• Waitaki District Council
• Waimate District Council

Christchurch has a plentiful supply of fresh clean drinking water. Christchurch's aquifers are replenished with 375 billion litres of water each year (JPG file, 80KB), most of which is unused and flows out to sea.

Origin of Christchurch’s groundwater

Around three-quarters of Christchurch’s groundwater comes from the Waimakariri. Water seeps through the river bed and into the groundwater, which flows toward the city at a rate of about 25 metres per day.

Rain that falls on the land west of Christchurch also contributes to the groundwater system. Recent information suggests that some of the deepest groundwater beneath Christchurch may come from rain and irrigation water that falls on the land to the north of the Waimakariri River.

Protecting Christchurch’s groundwater

We work with the community to help ensure we protect our freshwater now and for generations to come. People from across our region are working together as kaitiaki to protect and improve our water resources.

Christchurch’s groundwater is famously pure at its source. To ensure it stays pure, the area above the aquifer is subject to strict land-use rules under the Canterbury Land and Water Regional Plan to minimise the risk of contamination.

That’s why you’ll find recreational parks and very low-intensity stock grazing in this part of Canterbury.

The Christchurch City Council is the only organisation that can apply to take more water from our aquifer, and it can only do so to use for community drinking water supply.

For information regarding chlorination of the Christchurch drinking water supply, see the CCC website.

Find out more about drinking water protection zones.

As a private well owner, there are actions you can take to keep your water supply safe, for example:

• Learn where your well is located, how deep it is drilled and ensure it’s in good condition.
• Protect your well head (the top of the well where it emerges from the ground). Remember, this is your drinking water. Whatever goes down your well ends up in your glass. Follow these simple steps:

1. 1. Well cap - install a secure well cap, and seal between the casing and any hoses or cables going down the well.
   2. Well casing - ensure the well casing is elevated at least half a metre above the ground surface.
   3. Concrete apron - seal between the well casing and the surrounding ground with a concrete apron. If you're drilling a new well, install a bentonite seal around the casing.
   4. Backflow preventer - install a backflow preventer to stop contaminants siphoning back into your well.
   5. Area around well - keep the area around the well-head clear of animals, pesticides, fertilisers, compost and rubbish.
   6.  Sample point - have your groundwater supply analysed if you suspect a problem with the water quality.

• Check the historical use of the land to understand possible groundwater contamination risks. In Canterbury, one source of information is the Listed Land Use Register.
• There may be metals like lead and copper in the plumbing of your property, such as taps or other fixtures, that can impact water quality. When you first turn on your tap in the morning, run your tap to fill a large cup of water and tip this down the sink. You should also do this at other times when your tap has not been used for a while, like when you come back from holiday.

• Regularly test your water supply by taking a sample and sending it to a lab for analysis. Taumata Arowai maintains a register of accredited water testing laboratories around New Zealand.

There is potential for a range of contaminants to reach groundwater and surface water. Testing for these is important because drinking contaminated water can have serious health consequences. Contaminants that can be found in our water include the following:

Pathogens (bugs)

Pathogens, such as viruses or bacteria can come from faecal material from grazing animals or animal or human effluent storage and disposal.

• E.coli is an indicator of faecal contamination. You should test for E. coli quarterly, especially following heavy rainfall.
• Drinking Water Standards for NZ 2022 state that the maximum acceptable value for E.coli is less than 1 in 100 mL of sample.
• Seek specialist advice if your water requires treatment for pathogens. Methods could include one or a combination of ultraviolet disinfection, chlorination, and filtration. As an interim solution, boiling water for one minute will destroy most pathogens.

Nitrate

Nitrate can enter groundwater from farming activities, usually through animal urine and fertilisers, as well as from wastewater disposal and landfills. It can remain in the subsoil during dry periods and seep into groundwater following significant rainfall.

• We recommend testing nitrate levels annually, preferably during spring or autumn when nitrate levels tend to be higher. You should flush the tap for 10 minutes before sampling.
• Nitrate levels can spike after heavy rainfall, especially if that rainfall follows a long dry period. These nitrate spikes are greatest in shallow wells.
• Water with nitrate above the maximum acceptable value should not be used to prepare formula for young babies. Pregnant women and parents of new babies should talk to their lead maternity carer about the risks.
• Boiling or filters do not remove nitrate from the water.
• If your water requires treatment for nitrate, seek specialist advice. Methods could include reverse osmosis or ion exchange.
• Drinking Water Standards of NZ 2022 state that the maximum acceptable value for nitrate is 11.3 mg/L expressed as NO3-N or 50 mg/L expressed as NO3.

Learn more about the actions being taken to reduce the risk of nitrate contamination.

Download Risk Maps of Nitrate in Canterbury Groundwater 2022 (PDF File, 2.85MB)

The maps show where we have previously found high levels of nitrate in water samples from wells.

Heavy metals and organic chemicals

Heavy metals include cadmium, lead, manganese and arsenic. Organic chemicals include petroleum compounds, industrial solvents and pesticides.

• These contaminants can come from a variety of sources including old sheep dips, landfills and industry.
• The Listed Land Use Register (LLUR) is a publicly available database of sites where hazardous activities and industries have been located throughout Canterbury. This can help you identify whether any of these activities have been carried out on or near your property.
• Arsenic and manganese also occur naturally in the sediments in some parts of Canterbury and can reach harmful levels in groundwater, especially if the water is low in oxygen. If a water supply has a bad odour (smells like rotten eggs or sour cabbage) or high iron levels causing rusty staining where it comes into contact with air, these are signs that the water is low in oxygen and it is advisable to test for arsenic and manganese.
• A test for a full range of heavy metals and organic chemicals can be expensive, but only needs to be done once, unless you notice a change in the water.
• Boiling or filters do not remove dissolved heavy metals from the water. Seek specialist advice if your water requires treatment for heavy metals or organic contaminants.