Asian Correspondent Asia News

A previous post on Friday looked at the Bhumiphol Dam, but this one post will look at the next major dam, the Sirikit Dam. The three relevant charts are namely 1. Amount of water stored in the Sirikit Dam., 2. Accumulated amount of water entering Sirikit Dam for each year for 2005-2011, and  3. Accumulated discharge of water per year in the Sirikit Dam for 2005-2011, have to be considered together.

1. Amount of water stored in the Sirikit Dam per year for 2005-2011

Source: Irrigation Department – the graphic when you click on the page is interesting to watch and if you put the mouse over a line in the graph, you can find the exact amount of water in the dam on that day.

NOTE: Left-hand vertical axis is million cubic metres. The normal reference is 100% capacity. The years from left to right are 2005 (2548) – 2011 (2554). These are the default years for the full data.

BP: In some ways the early months were not unremarkable although by April 2011 you start see a different trend of it plateauing, but it is in late June 2011 where things really change and it goes vertical for a period – on June 25, there were 5.201 billion cubic metres and this went up to 6.140 cubic metres by July 2. This is almost 1 billion cubic metres in about a week. Of course the increase by late June 2011 we already had the most water in the dams compared with the previous 6 years.

2. Accumulated amount of water entering Sirikit Dam for each year for 2005-2011

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

Note: Left-hand vertical axis is million cubic metres. Horizontal axis is date. It is every 26 days (no idea why!), but it goes from January to December. Full data is only available for these 7 years.

BP: 2011 has the most amount of water entering the dam reservoir. About twice as much water entered the dam reservoir in 2011 than at the same time in the previous 6 years. It is end of June where things go vertical – as you have already seen with capacity. It is end of June in 2011 that things go crazy. The water entering the dams just continues to go up and even now it is only just leveling off.

NOTE: There is a lag from the date it rains to the date the water flows into the reservoirs so it doesn’t mean that suddenly the rain started in June – although there was a tropical storm in late June which can explain the large quantity of water entering at this time – but you can see the early start to the rainy season in March – as per this post on the rainfall for Northern Thailand -

3. Accumulated discharge of water per year in the Sirikit Dam for 2005-2011

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

Note: Left-hand vertical axis is million cubic metres. Horizontal axis is date. It is every 25 days (no idea why!), but it goes from January to December. “Full” data is only available for these 7 years.

BP: You see we go from March 25 – where 2.503 billion cubic metres had been discharged – which was the highest amount of water had been discharged at that point compared with the other 6 years. Instead of then continuing the normal trend of a consistent discharge of water it drops dramatically to the point that on May 19 – where 3.167 billion cubic metres had been discharged – which was the second lowest compared with the other 6 years. This lower daily discharge continued until July 13 – where at this point only 3.542 billion cubic metres had been discharged – when things suddenly start to move upwards and then even further upwards  on August 5 – where 3.967 billion cubic metres had been discharged – to August 28 where 5.280 billion cubic metres had been discharged – which was at the point where we had more water discharged than in any of the other previous 6 years. One has to ask the question, why was so little water discharged between March 25 until July 13? Only just over 1 billion cubic metres discharged over this time which was 1-2 billion cubic metres less (ie 1 billion vs 2-3 billion) than the previous years except 2010 over the same period. Now, at the end of June, we can understand if there was a sudden dip  as there was tropical storm, but for the months prior to this, why? It just mean we had to increase the level of the discharge once the flooding at already started.

Finally, given the amount of rainfall this year, BP thinks that even with better water management we would have had floods. There was simply too much water for the system to manage. However, BP is also of the view that the late discharge of water exacerbated the floods because it led to too much water having to be discharged from August onwards. In 5 out of the 6 years excluded 2010 (where even less was discharged), less than 1 billion cubic metres was discharged in each of those years between August 1-October 31. However, for 2011, over 4 billion cubic metres of water was discharged – from  3.946 billion cubic metres on August 1 to 8.206 billion cubic metres on October 31. This extra water that needed to be discharged made the floods worse. It is hard to say precisely, how much extra water should have been discharged earlier, but it was mistake leaving so much to be discharged in August onwards when it was already flooded.

Now, BP also thinks the current government could have done more to mitigate the damage with better and more timely warnings and been more prepared to handle the damage – the same also applies for the BMA – but given the level of rainfall and water that to be discharged from the dams from August onwards, the choice was about what areas would be flooded and which areas would try to be saved.