27 September 2004

Water storage lake fills

Greater Wellington Regional Council has begun to fill its empty water storage lake at Te Marua in preparation for summer.

When full, the lake holds the equivalent of 12 days’ supply of water in reserve for the metropolitan Wellington area (1,700 million litres). It had been empty since mid May for maintenance and cleaning.

Chris Laidlow, Greater Wellington’s water supply operations manager, said that both the Stuart Macaskill Lakes at Te Marua needed to be full before Christmas.

“The lakes are our main protection against running short of water in a drought, so it’s important to have them topped up to capacity as we head into summer. It’s likely to take 30 to 40 days to get the southern lake full, so we’re on track to achieve that comfortably.”

Filling the southern lake started late last week at a rate of 20 million litres per day (ML/d). Once the inlet pipes on the floor of the lake are completely covered the flow rate will be increased to as much as 80 ML/d – over 900 litres per second. The northern lake is currently 90 percent full.

Mr Laidlow said rainfall would be the main factor in how quickly the southern lake could be filled.

“We only fill the lakes when the water quality in the river is good, because cleaner water is easier to treat and needs less chemicals. The river naturally gets dirtier with heavy rainfall, so we’ll avoid taking water when that happens.”

The lake was emptied to tackle the gradual build-up of non-toxic algae that had caused the filters at Te Marua Water Treatment Plant to need more frequent cleaning. Since May, Greater Wellington has removed the algae that had settled on the lakebed. It has also checked the lining, seals, pipes and fixings that would normally be under water.

Mr Laidlow said that there had been few problems.

“This is the first time the southern lake has been empty since 1990, so we wanted to give it a thorough clean and check-up, which has been time-consuming. There were a few minor maintenance jobs but we’re pleased with the general condition of the lake’s infrastructure.”

ENDS

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