A new dam scheme could help protect Christchurch's dwindling water supply - but charging residents for the water they use is still being considered.

Under the scheme, dams would be built on streams off the Waimakariri River, designed to store floodwater in winter and release it into the aquifers over summer.

It is one potential solution to Canterbury's water problems, as the water levels in the city's aquifers have dropped to record lows.

Water charges are also being looked at to try and reduce household water use, which takes the biggest portion of water drawn out of the aquifers.


A working group has been formed to look at potential solutions and report back to the Christchurch West Melton Water Zone Committee.

Working group chairman Chris Kelliher said there was a lot more work to do on the scheme before he could say if it was the best or most cost-effective option.

But he believed creating dams or water storage ponds was a good solution.

"The idea is to harvest water out of the river in the winter when there's a good flow and it's not being utilised, and then put it back in aquifers in the summer," he said.

Similar schemes have been successful in Australia, and one is being piloted in Hinds in South Canterbury.

He said the working group was initially focused on recharging the aquifers, but would also look at what could be done to reduce water use.

He said water charges were still "on the table" and likely to be considered in the future.

"We have to look at using water more wisely," he said.


Christchurch residents use an average of 357 litres of water per person per day, compared with 273 litres of water in Auckland where there are household water charges.

Environmental planner and groundwater expert, Bryan Jenkins, said he believed the plan would work.

He said Canterbury's aquifers usually only replenished over winter, because the soil dried up so much over summer that any rain would evaporate from the soil before it could trickle through to the aquifers.

If a pond or dam was built in the right place, water could be released steadily so the ground stayed moist and water could gradually soak through.

But even if dams were built, he believed water charges would still be needed.

"They should be doing both as quickly as possible," he said.

The scheme is set to be put to Environment Canterbury planners next month, who would investigate it in more detail.


Where water from Christchurch aquifers goes:

• 45 per cent residential and commercial
• 31 per cent industrial
• 22 per cent rural or irrigation
• 1 per cent recreational