Water from the North is surging toward the Central Plains despite attempts to curb its volume.
The Royal Irrigation Department yesterday said Chai Nat, Sing Buri, Ang Thong, Ayutthaya and Pathum Thani that are situated downstream from the Chao Phraya dam in Chai Nat stand to be affected by the Chao Phraya overflowing.
The department has boosted discharge at the dam to 1,800-2,000 cubic metres per second to drain water upstream in Nakhon Sawan province and also to prepare for heavy downpours expected to continue until next Monday.
It predicts water levels downstream of the dam will rise by 25-50 centimetres.
Yesterday, the Chao Phraya River started to overflow in the tambon Jampa Lor area of Muang Ang Thong district, Ang Thong province, and in the tambon Ban Ngew area of Sam Khok district, Pathum Thani province. Overflow has continued in Bang Ban district of Ayutthaya for a week.
Sujarit Khunthanakulwong, head of the Department of Water Resources Engineering at Chulalongkorn University, said water would reach Bangkok in seven to 10 days and it may cause problems in the capital if it rains heavily from today until Monday as the Meteorological Department has predicted.
Seree Supratid, a lecturer on disaster management at Rangsit University, thinks floods will be limited in Bangkok due to its good flood prevention facilities.
He said heavy rains are the key factor for determining whether there will be flooding in the capital because this may exceed the city's drainage capacity.
In some areas, it may take six to 10 hours to drain the water.
Otherwise, Bangkok will stay safe, said Assoc Prof Seree.
However, the Bangkok Metropolitan Administration (BMA) has put all 50 districts in the capital city on alert for possible flooding.
Bangkok deputy governor Malinee Sukvejvorakij said yesterday staff of all districts were told to install water pumps in flood-prone areas so that rainwater can be quickly drained away.
The 1,200 people in 27 communities of 13 districts not protected by floodwalls along the Chao Phraya River should be ready to move their belongings to higher ground, she said. The BMA has already drained water from major canals.
Meanwhile, authorities are trying to reduce water flow from northern tributaries of the Chao Phraya River that pass through the Central Plains.
Kitti Tancharoen, assistant governor of the Electricity Generating Authority of Thailand, said the state enterprise had cut the discharge of the Bhumibol dam in Tak province to 1 million cu/m per day. The dam holds 7,211 million cu/m of water. It is 54% filled and can receive 6,251 million cu/m more.
The Sirikit dam in Uttaradit province has stopped discharges to divert water from the Yom River to the Nan River. The dam holds 5,884 million cu/m of water. It is 62% filled and can receive 3,626 million cu/m more.
The Yom River flows into the Chao Phraya River but it is not controlled by any dams.
Wim Rungwattanajinda, secretary to the PM's Office Minister, yesterday said the government was diverting water from the Yom River to the Nan River where the Sirikit and Naresuan dams are. The diversion is taking place through Khlong Hok Bat canal that adjoins the Nan River in Phichit province. Phichit and Phitsanulok provinces are receiving floodwaters from the Yom River in Sukhothai province.
The river overflowed yesterday in tambon Rang Nok area of Sam Ngam district of Phichit. People in Pho Prathap Chang, Bung Na Rong and Pho Thale districts were warned of possible inundation.
In Phitsanulok, situated between Sukhothai and Phichit, floods hit six out of nine districts due to both the overflow of the Yom River and persistent rain. Floods affected Phrom Phiram, Muang Phitsanulok, Bang Rakam, Chat Trakan, Nakhon Thai and Wang Thong districts.
The Yom River is subsiding upstream in Phrae and Sukhothai provinces.
The heart of Sukhothai remains inundated after the Yom River overflowed, breaking through its levee last Monday.
Big sandbags and gabions are have been deployed to plug the levee. Prime Minister Yingluck Shinawatra, who was in Sukhothai yesterday, said water could be pumped out of the heart of Sukhothai in two days.