The Provincial Waterworks Authority's (PWA) plant in Pathum Thani's Thanyaburi district on Sunday suspended supplying tap water to households in Thanyaburi, Lam Luk Ka and Nong Sua districts due to the water shortage.
Pathum Thani governor Pongsathorn Sajjacholaphan has declared the three districts disaster zones.
Local administration bodies have been instructed to use water and fire trucks to deliver clean water to residents.
Residents from Khlong 5 to Khlong 15 in Thanyaburi district and everyone in Lam Luk Ka and Nong Sua districts will be affected by the suspension of tap water.
The decision was made after Khlong 13, which supplies raw water to the Thanyaburi plant, dried up.
"Pathum Thani is now suffering the heaviest drought in 30 years. All the main rivers and tributaries have dried up," Mr Pongsathorn said.
The Thanyaburi plant usually supplies tap water to more than 50,000 households in the three districts.
Residents in the Khlong 12 area of tambon Bung Nam Rak, Thanyaburi district in Pathum Thani province bring plastic buckets and containers to receive water Sunday from Sanan Rak municipality.
The governor said the provincial authority has asked the Royal Irrigation Department to pump water from the Chao Phraya River into canals to send water through Chulalongkorn watergate to Khlong 1 and then to Khlong 13.
Residents in Muang, Sam Khok and other districts have not been affected because plants in those areas can take water directly from the Chao Phraya River to produce tap water.
Meanwhile, residents in Lop Buri have struggled to gain access to tap water for three days after the water level in the Chai Nat-Pasak irrigation canal dropped.
The drop in the water level was caused by farmers pumping water from the irrigation canal to their crops, irrigation authorities said.
Regional Irrigation Office 10 authorities said they had submitted letters to the governors of four provinces, Nakhon Sawan, Chai Nat, Lop Buri and Saraburi, asking farmers not to use water in the canal for agricultural purposes, but it did not work.
The Regional Irrigation Office 10's chief Phanukit Dissapung said authorities are trying to replenish the water supply in the Chai Nat-Pasak irrigation canal to ensure there is enough for tap water.
The Irrigation Department's deputy director-general Suthep Noiphairoj said a sub-committee on water analysis and monitoring will meet today to discuss water discharges from the four main dams: Bhumibol in Tak, Sirikit in Uttaradit, Kwae Noi Bamrung Dan in Phitsanulok and Chai Nat and Pasak Jolasid in Lop Buri.
The main topics of discussion will be climate assessment and rainfall, he said.
