Help by Saving Water

31 October 2011

We're fortunate Wellington usually receives plenty of rain to supply the city's water needs - the challenge is that it's not evenly distributed throughout the year and some years are drier than others.

Councillor Ngaire Best and a Greater Wellington Regional Council technician inspect the drained lake

Councillor Ngaire Best and a Greater Wellington Regional Council technician inspect the drained lake

During dry summers the water available to us from rivers, underground reserves and storage lakes can dwindle, raising the prospect of a water shortage for the city.

Saving water is always wise but this summer it has become essential. We need to manage our water supply carefully while Greater Wellington Regional Council carries out earthquake strengthening on one of its two bulk water storage lakes. The capacity of the lake will increase 14 percent when the project is finished.

One of the Stuart Macaskill lakes at Te Marua has been drained, which has halved the stored water available to Wellington, Lower and Upper Hutt and Porirua. The lake usually holds 1,800 million litres of water. After the upgrade it will be able to hold 2,050 million litres.

While this important work is carried out, there's more chance of a water shortage if we get a warm and dry spring or summer. So we're working closely with the three other cities and Greater Wellington Regional Council to encourage everyone in the region to use a bit less and make a big difference.

The Council's Three Waters and Waste Portfolio Leader, Councillor Ngaire Best, says the earthquake strengthening is necessary to meet national dam safety guidelines and to provide greater certainty that the lakes will keep their water in the event of a significant quake.

"This is an important project for two reasons - it will ensure we have more water stored in a dry year and the embankments containing the water are stronger," says Cr Best.

"It's all about managing risk. We don't know in advance the level of rainfall or demand for water that we will get each summer and with one storage lake out of service, we want to make sure we have options to maintain an adequate water supply."

Greater Wellington Regional Council water treatment technician, Phil Macdonald, says the upgrade work involves laying a tough flexible lining on the inside surface of the embankment and placing rock buttresses at the foot of the steepest sections of the outer wall faces, to reinforce them against damage from water seepage.

"These improvements will ensure the lakes meet safety guidelines published by the New Zealand Society on Large Dams," he says.

On average, each Wellingtonian uses 230 litres of water a day at home, which includes showers, toilet flushing, washing clothes, watering gardens and drinking.

Tips on how to save water

  • Turn the tap off when you brush your teeth (use only for rinsing)
  • Put a plastic bottle full of water in your toilet cistern - a 1 litre is fine - so the cistern uses less water
  • Only use washing machines and dishwashers for full loads
  • Fix any dripping taps and leaking pipes and toilet cistern valves quickly (one drip per second could add up to almost 30 litres a day, or 10,000 litres a year)
  • Use flow-control triggers on hoses
  • Buy water-efficient appliances
  • Test whether soil needs moisture (10 cm down) before watering
  • Target watering to the roots of plants at a rate soil can absorb without run-off
  • Time any watering sessions - 30 minutes once / twice a week
  • Mulch garden beds - if you haven't already (make sure soil is moist before applying mulch)