Authorities are diverting part of the Chao Phraya River into irrigation channels and low-lying fields in a bid to halt rising water levels, with more torrential rain expected this week.
Somkiat Prajamwong, director-general of the Royal Irrigation Department (RID), said a monsoon was expected over the next couple of days in the Central Plains and the East, while a low-pressure system would pass through the Northeast and upper Central Plains. Accordingly, more rain, including heavy downpours, is forecast during this period.
Four key dams in the Chao Phraya River basin are coping with 18.3 billion cubic metres of water, which is 74% of their water-retention capacity and 2.96 billion cu m more than last year.
According to Mr Somkiat, the Chao Phraya barrage dam currently discharges 2 billion cu m per second of water, resulting in the inundation of low-lying areas along Khlong Phong Peng in Ang Thong and Khlong Bang Ban in Ayutthaya as well as the areas along the Noi River in Bang Ban, Sena and Phak Hai districts of Ayutthaya.
He said the RID is trying to diminish the amount of water flowing into the Chao Phraya barrage dam by siphoning the water into irrigation channels along the east and west of the river.
Low-lying areas are being used to retain the diverted water and reduce the amount of water from flowing downstream, he said.
Chayapol Thitisak, director-general of the Department of Disaster Prevention and Mitigation, said his agency was told by the RID that dams and sluice gates along Yom, Chao Phraya, Pasak and Prachin Buri river basins would expedite water discharge in the wake of rising water levels.
Eight provinces are at risk of flooding, including Sukhothai, Chai Nat, Sing Buri, Ang Thong, Ayutthaya, Prachin Buri, Lop Buri and Saraburi, he said. Local authorities have been told to closely follow updates from the RID.
He added that officials have been deployed to check the strength of dykes and clear out materials obstructing waterways.
Meanwhile, the Nan River has burst its banks and swamped the riverside communities in Phichit's Bang Mun Nak municipality.
Several tambons surrounding Bang Mun Nak district were also flooded as a result of runoff from the Phetchabun mountain range. According to authorities, the economic zone of Bang Mun Nak municipality has now been surrounded by floodwater.
Deputy Bang Mun Nak mayor Annop Tankittithawon said 20,000 sandbags have been used to build flood walls around the municipality.
The Yom River has also begun to flood parts of Sam Ngam, Pho Prathap Chang, Bung Na Rang and Pho Thale districts.
Authorities are concerned about the possible flooding in Muang and Taphan Hin in light of the heavy rain forecast for this week and many rice fields have been turned into water catchment areas. People were also warned to get ready to move their belongings to higher ground because water can no longer be pumped out to the river.
In Chai Nat, more than 100 houses on the bank of the Chao Phraya River in Sapphaya district have been inundated. On Monday, people helped place sandbags to prevent more water from flowing into community areas.
In Ayutthaya, some temples on the bank of the Chao Phraya River have been inundated by the river's overflow. These include Wat Kasattrathirat Worawiharn in tambon Ban Pom, which is now under more than 50cm of water.
Local authorities along with monks and novices are creating an earth wall to help protect the temple's buildings.