TasWater has established an incident management team to meet weekly to discuss the water supplies at risk during the extended dry period across the state.

TasWater regional services department manager Mark McConnon said towns on stage 1 restrictions could have them raised to stage 2 restrictions at any point.

Stage 2 restrictions aim to reduce water usage by 50 per cent.

He said Launceston's supply was being closely monitored, and might require restrictions from as soon as next week.

"Systems can change overnight or they can change progressively through to the next week," he said.

"We monitor the demand and the flows in the rivers, so we'll continue to run our models that we've got for those towns, and once we realise that demand has picked up or restrictions aren't having a great impact at reducing that demand, that's when we'd start looking at implementing stage 2.

"It could be anywhere from a week to a month, depending on what's actually happening within those towns, and what happens in regards to the stage one, and how the community reacts to the implementation of those stage one restrictions."

The towns join Bridport and Currie, which were placed on stage 1 restrictions towards the end of December.

It is the first time in TasWater's history that towns other than Bridport have been placed on water restrictions.

Mr McConnon said water restrictions were being introduced now to ensure water reserves could be stretched for as long as possible in the event the state remained dry throughout autumn.

"We'll step through the restriction process. Obviously stage 1 is the first, which is that reduction by 20 per cent. Obviously stage 2 beyond that, and then we'll go to stage 3," he said.

"When we start getting around that stage 3, that's when we'd start looking at the trigger points to start to implement the contingencies."

Mr McConnon said people should try to reduce their usage across the state, regardless of whether they were located in a town on water restrictions.

More information is available from TasWater's website.

● Manual watering systems can only be used between 6am and 8am and 8pm and 10pm.

● Automatic watering systems can only be used between midnight and 4am.

● Handheld hoses with a trigger nozzle, buckets or watering cans may be used at any time.

● A bucket, high pressure cleaning device or commercial car wash can be used at any time for vehicle washing. A handheld hose with a trigger nozzle may be used for pre-rinsing and rinsing at home.

● Pools and spas with a capacity of over 2000 litres may only be filled with approval from TasWater.