Precision bombing by the Sri Lankan Air Force paved the way for ground troops to capture the Mavil Aaru dam from the LTTE on Tuesday, the government Defence Spokesman Keheliya Rambukwela told Hindustan Times.
He said that the aerial bombing helped clear the area of mines.
"The dam itself is safe, and water is flowing," he assured.
The sluice gates were opened at 8 pm.
About 10, 000 sq meters around the East gate of the dam had been heavily mined by the LTTE, and Sri Lankan ground troops were hard put to it to negotiate the minefield.
Hence the inordinate delay in opening the dam, despite air and artillery action since July 20, when the LTTE closed the dam.
Rambukwela said that the engineers of the Irrigation Department were still to go to the site to operate the dam.
Operations were still going on to make the area safe, an army spokesman said.
Asked to comment on the LTTE's claim that it had already opened the dam on "humanitarian grounds" at 5 pm on the same day, three hours before the government said it opened the gates, Rambukwela said that he did not want to deny the LTTE the pleasure of claiming to have performed a "humanitarian act."
He described as a "comedy of errors", the LTTE's first claiming that the closure of the dam was a "humanitarian act" and then at the end describing the reopening also as a "humanitarian act!"
Rambukwela wondered how these contradictory actions be both "humanitarian".
The LTTE had no business to be at the dam site, in the first place, he contended.
Secondly, the LTTE needed to be told in no uncertain terms that the government would never allow water to be used as a negotiating tool, he declared.
The row over water had led to air, sea and land action, not only in the dam area, but in Mutur, Sampur and the Trincomalee harbour in Trincomalee district, in the Mullaitivu and Kilinochchi districts in the North, and in Batticaloa district in the South East.
The government threw in all its sophisticated and heavy weaponry in a show of force unprecedented in the last four and a half years.
More than a hundred people were feared killed. About 40, 000 have been displaced.