Press Release – Greater Wellington Regional Council
The turn of a tap last Friday signalled the start of filling for Greater Wellington’s newly-strengthened and enlarged southern water storage lake at Te Marua, which has been empty since September last year.
Lake filling began with a modest 450 litres (about three baths’ full) per second, but will increase to as much as 800 litres per second once the water levels are high enough to stop incoming water disturbing the lake’s bed. The filling should take up to seven weeks, resulting in two million cubic metres of water – roughly twice the volume of the Westpac Stadium – in the lake by November.
“The good news is that the southern lake is now not only stronger in an earthquake, it’s also gone from 16 to 17 metres deep, providing 240 million litres more stored water once it’s filled,” says Cr Nigel Wilson, Chair of Greater Wellington’s Social and Cultural Wellbeing Committee.
“However, we’ll still have an empty lake this summer, only it’ll be the northern lake. We’ll start the summer with only half the usual lake water in reserve for the region’s cities, so we’ll be asking people to save a bit more water again this summer to make sure there’s enough to go around if we have long spells of warm, dry weather.”
Draining of the northern lake is likely to begin in November. Upgrading work will take place over summer and autumn, and is expected to be finished by December 2013.
The two Te Marua lakes provide a backup water source for Upper Hutt, Lower Hutt, Porirua and Wellington when river levels are low.
See www.gw.govt.nz/water for more information about the lakes upgrade and easy ways to conserve water this summer.
WHAT’S GREATER WELLINGTON’S ROLE IN SUPPLYING WATER?
Greater Wellington supplies treated bulk water to the Upper Hutt, Lower Hutt, Porirua and Wellington city councils. Most of this water comes from the Hutt, Wainuiomata and Orongorongo rivers, and an aquifer. In summer, water from the Te Marua storage lakes makes up for any shortages from these sources.
WHY ARE YOU UPGRADING THE TE MARUA LAKES?
The earthquake strengthening work is needed to meet national dam safety guidelines. The capacity increase of the two lakes combined will give us another 400 million litres of stored water – this amount could be enough to maintain water supply for up to two weeks longer in a drought.
WHAT ARE YOU DOING TO UPGRADE THE LAKES?
Greater Wellington is upgrading the Te Marua lakes by installing a tough, flexible plastic liner to prevent leaks following a major earthquake, and raising the outer walls to increase the lakes’ combined storage capacity by 13%. This work has been completed for the southern lake and will begin in a few months for the northern lake.
WHY ARE YOU DOING THIS WORK OVER SUMMER?
Most of the upgrading work requires a dry lake bed and dry conditions, which are most likely during summer.
WHERE DOES THE WATER FOR FILLING THE SOUTHERN LAKE COME FROM?
The southern lake will be refilled from the Hutt River at the Kaitoke Weir, north of Upper Hutt.
WILL YOU BE USING THE REVISED KAITOKE WEIR CONSENT TO GET ENOUGH WATER?
In August 2011, Greater Wellington was granted consent to reduce the allowable minimum water flow in the Hutt River at Kaitoke Weir for up to three years if needed while our stored water reserves are halved due to the upgrade. However, our aim is to avoid using the revised consent for refilling unless high demand and a dry spell require it. The weather outlook is for normal rainfall levels over the next two months.