When scanning the papers last week, BP was surprised to learn that two of Thailand’s major dams, Bhumibol Dam and Sirikit Dam, were releasing water after being 97% and 99% full respectively.  The Bangkok Post on October 6:

Increased water discharges from the Bhumibol Dam in Tak have threatened to add flood woes to provinces downstream, including Ayutthaya where a large number of industrial factories have been inundated since Tuesday.

The discharge rate at the Bhumibol Dam in Tak province has risen from 60 million cubic metres to 100 million cu m of water per day. The flow runs at about 1,200 cu m per second.

The increasing discharge is meant to save the dam. The extra volume of water has worsened the flood situation downstream.

The Nation on October 6, 2011

Meanwhile in Tak province, water from the Ping River overflowed into two sub-districts and about 100 households have been evacuated. The governor ordered the provincial officials to be vigilant. The Ping River continues to rise after the Bhumibol Dam in Tak released excess water.

In Nakhon Sawan, the Ping River overflowed, flooding homes, many of them now under one metre of water. Local authorities are reinforcing earthen dykes and residents have moved their belongings to higher ground.

BP: At the time, was thinking why were the dams allowed to become so full? But didn’t have time to look for more information. But have seen this DPA article last week:

Officials have been forced to release water from the two largest dams, Bhumibol and Sirikit, into the Ping and Nan rivers, which feed into the Chao Phraya, said Smith Dharmasaroja, head of the Natural Disaster Warning Foundation.

‘The problem is water management,’ Smith said. ‘We kept too much water in the dams early in the rainy season, and now at the end of the season, they have to release a large amount of water at the same time, which has caused floods.’

Thailand’s rainy season usually starts in May and ends in October.

Then, this Bangkok Post article which is an interview with Smith:

This incident does not result from a natural disaster. Our problem is that we do not know how to manage water. We did not assess from the beginning of the rainy season whether there would be lots of rain and how much water should have been held in the dams.

Every party kept water in large dams. The Irrigation Department and the Electricity Generating Authority of Thailand (Egat) were afraid they would run out of water in the dry season. They made the wrong guess.

If rains continue throughout the middle and the end of the rainy season, the dams cannot hold all the water and now all large dams are full.

The problem is that all the full dams are discharging water simultaneously. The Central Plains below the dams has already suffered heavy rains. Consequently there is a massive amount of water. The simultaneous discharges from the dams have therefore caused flooding in many areas from Nakhon Sawan to Ayutthaya.

Now, a NYT article by Seth Mydans also has some quotes from Smith:

As some of Thailand’s worst flooding in half a century bears down on Bangkok — submerging cities, industrial parks and ancient temples as it comes — experts in water management are blaming human activity for turning an unusually heavy monsoon season into a disaster.

The main factors, they say, are deforestation, overbuilding in catchment areas, the damming and diversion of natural waterways, urban sprawl, and the filling-in of canals, combined with bad planning. Warnings to the authorities, they say, have been in vain.

Those areas become obstacles to the free flow of water, he said, as developers continue to extend their activities.

They build their estates in low-lying areas that are supposed to be reservoirs,” he said, “and they throw up a dam or a dike, and they block the flow where the water is supposed to go in rainy season.”

Once the floodwaters reach Bangkok, they will pour into a city that has lost its natural defenses: a huge network of canals that have been filled in — or clogged with garbage — as the city has become an overcrowded behemoth.

Bloomberg today:

“The issue is less the rain and more the run-off waters that come from the northern parts where the dams release the water,” said Han from Hana Microelectronics. “That is anticipated to rise over the next few days in the Ayutthaya area before it passes through Bangkok, and that’s why everyone in Bangkok is extremely worried that it’s their turn now.”

BP: So why were the dams – there are plenty of others – allowed to get so full? Now having said that, to be fair, in June 2010 the dams hit record lows and if there as no water it would be the reverse problem. Is the problem too much unexpected rain this year or bad water management as Smith states? Could something have been done early on in the rainy season?