Representatives from the water company said they had taken steps to reduce the effect algae in water storage basins was having on drinking water, leaving an earthy taste and smell.

Branch operations manager Wayne Murdoch said because storage facilities held large volumes of water they always contained algae.

The storage reservoirs are located across the south-west and hold raw water until it goes through to treatment plants and eventually enters the drinking water system.

“Seasonal weather patterns suggest that you do get fluctuations in algal growth throughout those storages,” Mr Murdoch said.

“You always have algae in there, but whether those populations rise or fall depends on the weather patterns.”

“The levels are not super high.

“These aren’t massive blooms or anything, this is just an increase in the levels of algae within the system.”

The last time algae affected the taste of Warrmambool’s drinking water was in November 2016, and Mr Murdoch said it happened once every couple of years.

Mr Murdoch said the poor taste and smell was caused by chemical compounds MIB (methylisoborneol) and geosmin as a result of the algae in the water prior to treatment.

Service delivery general manager Ian Bail said there were various types of algae in drinking water all the time.

“This stuff’s in the water all the time. It’s like if you had a glass of water and you put one drop of cordial in,” he said. “Most of us wouldn’t taste it, but by the time you’ve put 50 millimetres in the bottom of the cup, we can all taste it.

“That’s what’s happening here with those byproducts from the algae – they’re there all the time but it just means you’ve tipped that threshold.”

Wannon Water is using water unaffected by algae to dilute the supply flowing in Warrnambool at the moment.

Mr Bail said the water was completely safe to drink by the Australian Drinking Water Guidelines and the Victorian Safe Drinking Water Regulations and would not cause health issues.

In the meantime, Mr Bail said some people found refrigerating water improved its taste and smell.

A Department of Health and Human Services spokesperson said the organisation was aware of the aesthetic drinking water quality issues affecting water supplied in Warrnambool.

“The water in Warrnambool is safe to drink,” they said.

“It's not unusual at this time of year for blue-green algae to affect raw water sources, when water bodies are warmer and more conducive to microbial growth.

“Water agencies are vigilant in monitoring for all risks in raw water, including blue-green algae, and treat the water to ensure that it's safe to consume.”