The Northern Territory government will restrict the water supply in Katherine due to contamination from old toxic firefighting foams used at Top End army bases.
Around 11,000 residents will be affected by at least two months of measures beginning August 21, at a time of peak demand during the NT dry season.
Health Minister Natasha Fyles gave the town's water supply the all clear to drink, but said limiting irrigation times were an additional precautionary effort to keep the use of groundwater to a minimum.
Pollutants from decades-long use of poisonous chemicals at the nearby RAAF Tindal base have leeched into ground and surface water, and while the health risks are still unknown, the federal government continues to provide alternative drinking water to about 50 Katherine homes.
The town's water supply comprises 10-30 per cent of groundwater, while the rest comes from the Katherine River.
Ms Fyles said the town relies much more heavily on bore water - which has higher levels of pollutants - during September and October at the end of the dry season.
Residents could be impacted during this time, as the build up to the wet season approaches, when Katherine's water demand spikes by up to 50 per cent.
The current daily average demand is 10.25 megalitres, which is expected to jump to around 15 megalitres.
No fines or penalties will be issued to residents who flout the new rules, which include time limits on watering gardens.
The Defence Department on Wednesday announced a water treatment plan for the region will be installed towards the end of the year as it explores new water sources.
The Gunner government will review the measures in November, and Housing Minister Gerry McCarthy wants to introduce permanent compulsory restrictions to tackle the issue long term.
Territory government test results last month revealed seafood from two contaminated Darwin creeks are safe to eat.
In April the federal government reduced the safe daily drinking water limit for people exposed to 12 Australian contaminated army bases.
KATHERINE'S WATER RESTRICTIONS:
* Odd numbered properties are permitted to irrigate Monday, Wednesday and Saturday from 6pm-8am.
* Even numbered properties are permitted to irrigate Tuesday, Thursday and Sunday from 6pm-8am.
* No watering of hard surfaces.
* Handheld watering via a bucket or watering can is permitted at any time.