BP has already blogged twice – once in July and another time in late August – 0n the possibility of severe flooding in 2012. Severe in the sense at a similar scale to 2011.  As blogged previously:

Last year, as Thailand experienced severe flooding, BP blogged repeatedly about the the water level in dams – see Sirikit and Bhumibol dam posts. The relevance being as the water level in the dams increased, the authorities had to release water from the dams, but this was happening during the rainy reason when there was excess rainfall – see posts here and here. In BP’s opinion, the combination of extra rain and the mismanagement of the dam levels (although see this post for a contrary opinion on mismanagement of dam levels) caused the floods last year. The government can’t do anything about rainfall, but it can manage the water in dams differently.

There was some anxiety expressed in January that the water level in the dams was too high and not much was being done about it although as BP noted in this post, the extent of downward trajectory of the dam levels suggested the panic was overblown. Back in early January, Bhumibol dam was 91% full and the Sirikit dam was 89% full. Then, in March, BP blogged again at the end of March that the quantity of water in those two dams, the two largest dams, had reduced to 60% and the plan was to reduce the the water level in those dams to be 45% full in order that, if necessary, there was additional capacity in the dams in case there is excess rainfall during the rainy season. Then, in early July, Bhumibol dam was 46% full and the Sirikit dam was 44% full.

BP: This post will focus more on the management of water in the dams than rainfall. The context is the floods in 15 provinces has raised anxiety over a repeat of the 2011 floods. It is important to note that there are regular floods in Thailand. The floods during the monsoon season in 2010 resulted in 232 fatalities and at least US$1.676 billion in damage (Wikpedia). The floods in March 2011 resulted in 53 fatalities and at least US$500 million in damage (Wikpedia). Floods of this scale would be deemed fairly regular and BP doesn’t think you could characterize them as being severe. We have already had similar flooding so far this year and are likely to continue to have flooding on such a scale each year. The question this post seeks to answer, are the dams being managed that they we are likely to avoid severe flooding like in September-October 2011?

Chart 1: Bhumibol Dam : Amount of Water in the Dam

Safari

Source: Hydro and Agro Informatics Institute (an agency under Ministry of Science and Technology) although it states the figures are from the Irrigation Department.

Note: Left-hand vertical axis is million cubic metres. Horizontal axis is date. It is every 31 days or so (no idea why!), but it goes from January to December. “Full” data is only available for these 8 years.

BP: The dam is only about 57% capacity hence there is plenty of additional capacity that rain water can flow into.

Chart 2: Bhumibol Dam : Daily discharge of water

Safari

Note: Left-hand vertical axis is million cubic metres. Horizontal axis is date. It is every 30 days or so (no idea why!), but it goes from January to December. “Full” data is available for 2005-2012, but have only included for 2010-2012 to make the chart readable.

BP: As you can see that in 2012 we started off with high levels of daily discharge of water, but this has gradually reduced as we hit the monsoon season and is almost at zero now which has happened because of the recent heavy rainfall – this is only possible because of the earlier higher discharges. Compare this to to 2011 when  from August it started to slowly raise before hitting stratospheric level of discharges in October.

Chart 3: Bhumibol Dam : Accumulated discharge of water

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Note: Left-hand vertical axis is million cubic metres. Horizontal axis is date. It is every 31 days or so (no idea why!), but it goes from January to December. “Full” data is only available for these 8 years.

BP: As you can see that while a significant amount of water has been discharged in 2012, the line has gone horizontal during the peak of the rainy season whereas in 2011 it went more vertical.

In 2011, between September 1-November 1, 2,709 million cubic metres were discharged from Bhumibol dam or an average of 44.4 million cubic metres per day

In 2012, between September 1-September 21, 62 million cubic metres were discharged from Bhumibol dam or an average of 3.1 million cubic metres per day.

Chart 4: Sirikit Dam : Amount of Water in the Dam

Safari

Note: Left-hand vertical axis is million cubic metres. Horizontal axis is date. It is every 31 days or so (no idea why!), but it goes from January to December. “Full” data is only available for these 8 years.

BP: So capacity is 65% which is the second lowest in the last 8 years. Hence, there is plenty of capacity for storing any rain water that is falling now.

Chart 5: Sirikit Dam : Daily discharge of water

Safari

Note: Left-hand vertical axis is million cubic metres. Horizontal axis is date. It is every 30 days or so (no idea why!), but it goes from January to December. “Full” data is available for 2005-2012, but have only included for 2010-2012 to make the chart readable.

BP: As you can see that in 2012 we started off with high level of daily discharge which continued through the hot season, but it is only in the last month that the level of daily discharges has reduced significantly and is almost at zero now which has happened because of the recent heavy rainfall – this is only possible because of the earlier higher discharges. Compare this to to 2011 when from August it started to raise before hitting stratospheric discharges in September and October.
Chart 6: Sirikit Dam : Accumulated discharge of water

Safari

Note: Left-hand vertical axis is million cubic metres. Horizontal axis is date. It is every 31 days or so (no idea why!), but it goes from January to December. “Full” data is only available for these 8 years.

BP: So the earlier discharge of water has helped, but clearly less water going into the dam has helped.

In 2011, between September 1-November 1, 2,657 million cubic metres were discharged from Sirikit dam or an average of 43.6 million cubic metres per day.

In 2012, between September 1-September 21, 81 million cubic metres were discharged from Bhumibol dam or an average of 4.05 million cubic metres per day.

Flash floods caused by heavy rainfall can certainly cause a lot of damage, but this is a different type of flood compared with 2011. So far the authorities have managed the water level in the dams and hence also the discharge of water from the dams with very little discharge of water right at the peak time of worry (i.e in September and October) which is the complete opposite of what happened in 2011. Of course, we may now get weeks of very heavy rain, but so far there is no evidence to suggest the mismanagement of water in the dams will be a problem for 2012. If anything, the authorities are basically able to cut the level of discharge of water now, which is during the time we have had heavy rainfall, so as not to compound the issue which we had last year of heavy rainfall + large amount of water being discharged from the dams.

Simply put, while we still need to keep an eye on heavy rainfall which can cause flash floods, we don’t have the level of water entering the river system from the North and the Central regions that we did last year. Until this happens (which BP thinks is still very unlikely for this year), the risk of severe flooding is very low.

*Made some edits just after posting to clarify a few points