But downstream was already swamped with water as well, so the existing floodwaters combined with the dam discharge caused the historic flood. The only strategy we could use that time was to drain the water to the sea as fast as we could and a major flood was inevitable."
Seree Supharatid, director of Rangsit University's Centre of Climate Change and Disasters, said there was no way this year's flooding would match what occurred in 2011, as the situation was totally different and the flooding now has come mainly from rain, not the dams like five years ago.
"I think that the South should be warned of major floods more than the Central Plain, as the prediction is for heavy rain and possible storms in the South," Seree said.
Chaowalit pointed out that water mismanagement was another factor that worsened the flood situation in 2011.
"There was a severe drought in the dry season of 2010-11, so the water policy of that year was to store more water for the next dry season and the policymakers did not think that there would be so much rainfall during that year," he said.
"We just realised this when there was already flooding downstream and the dams were full," he said.
Royon said the major weakness of water management was that policy-makers often managed the water situation based on fear of flood or drought.
"We have to manage water based on scientific data and predictions," he said. "We should plan water management by considering the real-time water situation, the scientific prediction for the next two weeks and the rain pattern of next year.
"We already have big lessons from the big flood of 2011 and major drought of 2015. We should not repeat the same mistake."