Chao Phraya, Pa Sak rivers to rise as dam discharge doubles this week

Chayan Muangsong, ONWR deputy secretary-general, said on Tuesday that Pa Sak River will rise by 0.4 to 1 metre from Lopburi’s Phattana Nikhom district to Ayutthaya’s Tha Ruea district, while the water level at the end of Rama VI Dam will rise by 0.4 to 0.6 metres.

With heavy rain forecast until Sunday in most parts of Thailand, ONWR speculates that 400 million cubic metres of water will flow through Pasak Chonlasit Dam in Lopburi this week. Hence, the Royal Irrigation Department needs to gradually increase the dam’s drainage gradually from 400 to 800 cubic metres per second.

ONWR also said the water level at the confluence of the Pasak and Chao Phraya rivers in Phra Nakhon Si Ayutthaya will rise by 0.25 to 0.5 metres.

He said some 3,300 to 3,500 cubic metres per second of water will flow through Ayutthaya’s Bang Sai district and may cause flash floods. He added that the agency tried to divert the water to Thung Bang Rakam in Phitsanulok, but the Ping River has overflowed on its way to the Chao Phraya.

Therefore, ONWR has tried to reduce the effect on lowland areas from Chai Nat to Samut Prakan by maintaining the water flow through Chao Phraya Dam at around 2,800 cubic metres per second.

This will cause the water level above the dam from Chai Nat’s Muang and Manorom districts and Uthai Thani’s Muang district to rise by 0.3 metres.

Meanwhile, ONWR has issued the following instructions for relevant agencies to follow:

• Monitor the situation closely, inspect and reinforce water protection buildings and embankments in areas at risk.
• Prepare equipment to provide immediate help to flood victims.
• Adjust water-management plans at reservoirs and dams, while using lowland areas to divert waterflow and prepare for flash flooding.
• Issue warnings for people living in areas at risk of flooding.