"It was an extremely difficult and ambitious operation. But we had to act, and try to do whatever was humanly possible to hold back the water," said Saxony-Anhalt state premier Reiner Haseloff.
Thousands of people had been evacuated from the towns of Jederitz and Kuhlhausen after the dyke at Fischbeck broke and water flooded the area.
On Saturday divers were sent to inspect the damaged dyke, after which tank traps and nets full of rocks were dropped at the site by helicopter. Then two barges were tugged to the spot and holes blown into them so they would sink.
"We have never done such a thing before," admitted tug pilot Thomas Peter. "But we are not crazy, we could halfway anticipate what was going to happen."
On Sunday a third barge followed suit, and helicopters were used to drop more sandbags, effectively closing the huge hole in the dyke.
"We're very satisfied that this worked," said a spokeswoman for the crisis management team on Sunday.
The flooded area had shrunk by around five square kilometres within the first 24 hours of the hole being blocked. But the area around the spot where the rivers Elbe and Havel meet is still terribly flooded, with around 145 square kilometres under water.
Further south engineers were trying to blow a hole in a dyke to speed up the water's passage back into the River Saale. Two explosions were prepared at the Saaledeich at Breitenhagen to create a 60-metre hole to enable the floodwaters to return to the river.
The floods which hit much of eastern and northern Germany are slowly receding, leaving people pulling down walls of sandbags and surveying the damage. Farmers are already looking at €100 million in losses, while tourist facilities such as family-run hotels could be facing ruin as holidaymakers stay away from flooded areas.