GW proposes options to boost water supply

Greater Wellington is proposing several short-term measures to provide more water at peak times and reduce the risk of shortages. It is also investigating long-term measures for increased population growth.

"Our water supply system entails a low risk of water shortages each year but this risk is increasing as the population grows," says Greater Wellington's Parks, Forests and Utilities Chair Cr Rex Kirton.

"A decade ago, the system was expected to meet the region's water needs until 2020. However, higher-than-expected population growth and revised climate information mean planning for our next steps is needed now."

The short-term options are:

Increasing capacity at the Te Marua water storage lakes by raising the maximum water level
A new reservoir in central Wellington
Taking more water from the Hutt River at the Kaitoke Weir
Developing the Upper Hutt aquifer
Together, the first three options could supply a population of up to 395,000 in the four cities, which is projected for 2012. The Upper Hutt aquifer would provide for growth beyond 2012, for about 10 years, but may be needed sooner if one of the first three options doesn't go ahead.

Cr Kirton says that Greater Wellington also needs to establish a major new water supply source or implement a wide range of water efficiency measures by 2022, according to current population projections.

"We have investigated three potential dam sites for long-term water supply: Skull Gully in the Wainuiomata Water Collection Area, the Pakuratahi Forest, and Whakatikei River in the Akatarawa Forest. We needed to identify a preferred source, as planning and development of such projects can take 8-10 years.

"Our preferred site is the Whakatikei River in the Akatarawa Forest. It has advantages over the other two sites because it is on the western side of the Wellington Fault - so distribution pipes to Porirua and Wellington would be much less vulnerable to a fault movement - and the proposed storage capacity could be increased for a relatively low cost. It would also be closer to areas of projected population growth.

"We're also looking into a wide range of water demand management options and talking with the region's city and district councils about a more cohesive regional approach to managing water resources in the medium to long term. More efficient use of water may delay the need for a dam for a number of years."

Greater Wellington will consult this year with local councils on the supply options and with the public in early 2009.

For more information see www.gw.govt.nz/water