Smith Thammasaroj, chairman of the centre, said that in the near future, provinces in the lower Chao Phya River Basin would be inundated throughout the rainy season because global warming would cause a higher sea tide.

"The way to prevent the situation is to start building a permanent water barrier along the Chao Phya River to prevent water overflowing into Bangkok and its adjacent provinces," said Smith.

Global warming has worsened the effects of the La Nina and El Nino phenomena, which usually occur every four or five years.

The effects of the current La Nina cycle were seen recently when abnormally heavy rain hit Thailand, despite only one storm - Xangsane - hitting the country this year, he said.

Smith said the La Nina phenomenon triggered unusually cold ocean temperatures in the eastern equatorial Pacific, which introduced a large amount of steam into the air.

The rain was caused when the steam drifted across land and collided with the seasonal Monsoon Trough in the North and Central regions, he said.

In the early part of the rainy season, there was as much as 300 to 400 millimetres of rainwater in a day in some northern areas such as Nan and Uttaradit, Smith said, adding that 90mm of rainwater is usually enough to cause flash-floods and landslides.

La Nina caused the North's rainy season to start earlier in May, he said.

Meteorological Department director Suparuek Tunsrirattana-wong said the overall volume of rainfall in the country since early this year until October stands at 1,596mm, or 21 per cent more than the mean annual rainfall over 30 years.

There was 30 per cent more rainwater in the North, 5 per cent more in the Central region, 35 per cent more in the East, 25 per cent more in the eastern parts of the South and 10 per cent more in the western parts of that region.

Smith said the large amount of rainwater combined with ineffective water management had made the situation worse.

"The rainwater from the North should be released into basin areas along the Chao Phya River early in the season in order to prevent the water accumulating," he said, adding that each province along the Chao Phya should also construct barriers to prevent flooding in their areas.

The accumulated water was unable to find a way to drain and so flooded the provinces of Ayutthaya, Sing Buri, Angthong and Bangkok, he said.

To prevent flooding in the long-term, more dams and embankments are needed, he said, adding that of the 800 billion millimetres average rainfall in the country only 200 billion millimetres was utilised due to a shortage of water reservoir space.

He said that at the very least, embankments should be constructed along the Yom River to prevent water from the North flowing directly into the Chao Phya River.

While La Nina is at the end of its cycle, it is always followed by El Nino, which would bring about drought conditions for about 12 to 18 months.

"El Nino will start at the end of January, causing serious heat in April and very little rain across the country until November or December when typhoons and tropical storms will hit the lower Central region and the Gulf of Thailand," said Smith, warning that the country will be hit by severe drought.

Because of this, the reserved water in large dams should be well managed if it is to be adequate for the year, he said.

Chatrarat Kaewmorakot

The Nation