The Marina Barrage is a dam in Singapore built at the confluence of five rivers. By keeping out seawater, the barrage forms Singapore’s 15th reservoir and first reservoir in the city.
The Marina Barrage also acts as a tidal barrier to keep seawater out, helping to alleviate flooding in low lying areas of the city. When it rains heavily during low-tide, the barrage’s crest gates will be lowered to release excess water from the reservoir into the sea. If heavy rain falls during high-tide, the crest gates remain closed and giant drainage pumps are activated to pump excess water out to sea. [source: Wikipedia]