GWMWATER will test an alternative water supply for Horsham by supplying the city with 100 per cent groundwater for up to the next 10 weeks.
Instead of supplementing Horsham's water supply with 30 per cent groundwater, GWMWater will extract all water from the Laharum bore field as part of a six to 10 week trial.
The trial will determine whether Horsham will be able to rely on groundwater if Grampians storages run dry.
GWMWater has started operating two production bores 24 hours a day, supplying four megalitres a day to the Mt Zero water storage.
Production bore three will regulate flows into the Mt Zero storage and can contribute an additional two megalitres a day if needed.
Corporate services manager Andrew Rose said the trial would investigate Horsham's water security because it would test whether the city had an alternative water supply.
Mr Rose said GWMWater expected the Laharum bore field to recharge its groundwater level.
"It's the most extensive research we've done and it's important," he said.
"Horsham could be one of the only towns in the state not to run out of water.
"This is an opportunity to guarantee Horsham's viability."
Mr Rose said GWMWater had supplemented Horsham's water supply from Lake Wartook with Laharum groundwater for the past two years to manage the drought-induced decreasing water levels.
"As part of a risk management plan for the region, given there are so many unknowns, we need to investigate whether Horsham has an alternative if the surface water dries up," he said.
Mr Rose said the trial could boost water levels in Lake Wartook and could also benefit Laharum landowners because the results would determine the potential for the area.
Mr Rose said it was a gradual process to change the water supply and it would be three to four weeks before people noticed the difference.
Managing director Jeff Rigby said it was the first time the Laharum bore field had been tested.
"We've never tried it before and we're going off peak demand now so we decided we would solely supply Horsham with bore water and then switch back to Wartook," he said.
"It's a test to see what sustainable base the bore can handle."
Mr Rigby said people might notice a change to water quality.
"We will continue to meet the drinking water standards but by virtue of it being groundwater it will have different aspects to it," he said.
"But it won't be as dirty as Wartook water.
"This trial will also test our water treatment plant process because it usually runs on 30 per cent bore water, not 100 per cent."
Grampians storages are holding 3.9 per cent of their capacity.
In February 2007 the State Government provided up to $250,000 for GWMWater to construct a new bore at Laharum to provide 350 megalitres to Iluka for a mineral sands mine at Douglas near Balmoral. Laharum Community Building Initiative group opposed the move, asking GWMWater to instead use the bore to develop a multi-million-dollar farm enterprise scheme.
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