People living near waterways in 11 provinces including Bangkok have been warned of a rise of up to 66 centimetres in the Chao Phraya River starting this weekend due to heavy downpours resulting from Storm Noru and the monsoon.
The warning on Thursday came from the Department of Disaster Prevention and Mitigation and the Royal Irrigation Department. It was directed to Ang Thong, Ayutthaya, Bangkok, Chai Nat, Lop Buri, Nonthaburi, Pathum Thani, Samut Prakan, Sing Buri, Suphan Buri and Uthai Thani, especially to people living outside embankments and in low-lying areas, and to business operators and workers on the banks of the river.
More rain from Storm Noru, which passed over northeastern Thailand late Wednesday, had increased the flow rate of the Chao Phraya, said Prapit Chanma, director-general of the Royal Irrigation Department. As a result, he said, the department had to speed up discharges from the Chao Phraya barrage in Chai Nat to control the level of the river in provinces upstream north of the barrage.
The level of the river above the barrage was 17 metres above mean sea level while a suitable threshold should not exceed 16.50 metres, he added.
The flow rate of the Chao Phraya in Nakhon Sawan rose from 2,329 cubic metres per second on Wednesday to 2,576 cu m per second on Thursday and was speeding up.
The Royal Irrigation Department will raise the discharge rate at the barrage in Chai Nat from 2,300 cu m/sec to 2,500 cu m/sec from Oct 1 to 7, Mr Prapit said.
It will also try to limit the flow of the river through Bang Sai district of Ayutthaya at 3,000 cu m/sec to protect Bangkok and adjacent provinces.
The adjacent provinces include Pathum Thani, where flooding was expanding on Thursday.
In Muang district, floodwater was 30-50 centimetres deep in a community in front of Wat Bang Luang in tambon Ban Chang and 40-60cm at Wat Nam Won in tambon Bang Duea. Flooded areas there were expanding as the upstream discharge rates of the Chao Phraya rose over the past three days.
At 4pm the Meteorological Department reported that Noru, now downgraded to a tropical depression, was in Muang district of Chaiyaphum province in the Northeast. The storm together with the monsoon would cause heavy rains to continue nationwide until Friday, it said.