Water restrictions are probably not something many southern Tasmanians are expecting after a wet spring, but TasWater says they could be implemented because of challenges it faces in supplying drinking water.
TasWater said heavy downpours made it harder for southern Tasmania's ageing water treatment plant to cope, and demand for water in the Greater Hobart area was continuing to increase.
"When we have heavy rain, it runs straight into our rivers carrying with it huge amounts of sediment and debris and stirs up sediments already in the river," said TasWater's Luc Richard.
"The water becomes cloudy and thick with suspended matter, we call this turbidity.
"It's happened to such an extent that we can't treat the water to an acceptable level."
Mr Richard said the plant had been slowed and TasWater was relying more on its reservoirs.
As well as the heavy rains, Mr Richard said the intensification of agriculture in the catchment also affected the amount and type of sediment that flowed into waterways.
"We're coming into summer now and that's usually our biggest demand of the year ? any small changes that people can make like reusing water in their gardens or only using a washing machine or dishwasher when they're full can help," he said.
Mr Richard said he expected water restrictions would be needed in southern Tasmania.
The Bryn Estyn Water Treatment Plant in the Derwent Valley supplies almost 60 per cent of greater Hobart's drinking water.
TasWater's Tony Willmott said the plant, built in the 1960s and upgraded in the 1990s, was being upgraded again "to increase water supply capacity for the community now, and for the next 30 to 50 years depending on how fast the Greater Hobart region grows."
"The original plant was originally sized to treat 160 megalitres a day, the new plant will, in turn, treat 160 megalitres a day as well but ? the turbidity will not be as much of a problem to us."
The $200 million works are expected to be finished in 2023.
From 2018 to 2019, water use in Hobart increased by 10 megalitres a day ? enough water to fill four Olympic-sized swimming pools.
TasWater said the main reasons at the time were the tourism boom experienced before the coronavirus pandemic, and dry weather encouraging people to water their gardens.
Water treated at Bryn Estyn is also used by irrigators.
The Sorell stage of the South East Irrigation Scheme draws its water from the plant and has a capacity of 3,000 megalitres.
According to Tasmanian Irrigation, it has a daily flow rate of 8.22 megalitres a day.
The scheme started in 2015 and the initial term of the agreement is for 25 years, with up to three extensions of 25 years.
© ABC 2021
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