The Tha Chin river is slowly recovering from the deluge of black, foul-smelling water which killed thousands of fish. The river's highly polluted state was first noticed by the officials of Suphan Buri towards the end of April. Initially, it was assumed that industrial effluents were causing this severe pollution. But later, the reason for the water turning putrid was traced to the paddy fields.
Nisakorn Kositratna, deputy director-general of the pollution control department, said there was evidence suggesting that the farms were responsible for polluting the river, and not factories. Tests conducted on the putrescent water has revealed that the contamination level of heavy metals -- such as copper, manganese, zinc, lead and chromium -- did not exceed permitted standards and was no different than when the phenomenon first occurred.
On the other hand, paddy fields in Suphan Buri's Song Phi Nong and Bang Plama districts are thought to be primarily responsible for polluting the river. Water was being held in these fields after the heavy rains that occurred before the Songkran festival. This large volume of water was further augmented by overflows from districts north of the area. "It can be compared with leaving rice in a jar of water for 10 days. This causes fermentation, which leads to decay. The decayed water flowed into the river and contaminated it," Kositratna said.
Farmers were unable to drain out the decayed water from the paddy fields because officials responsible for drainage were unavailable during the Songkran festival. By the time the problem came to the notice of the officials at the end of April it had turned into a severe crisis. The officials closed the gate and prevented clean water from mixing with the polluted water that flowed into the river at a constant pace. But by then the river had become a sewer carrying the polluted water to the sea and killing aquatic animals along the way.
In mid-May, officials began opening the gates and regulated the flow of water at 100 cubic metres per second. This has had the effect of diluting the polluted water, thus improving the water quality in the river. However, officials say the polluted water from paddy fields would continue to drain into the river for a month. They have also warned that the phenomenon was bound to repeat itself. "The water may look clearer now. But the problem still remains. A large volume of polluted water remains trapped in the paddy fields. The worst-affected areas are Samut Sakhon and the river estuary," said provincial governor Manit Silpa-archa.