Rivers are the most important geographical features in Bangladesh, and it is the rivers that created the vast alluvial delta. It's been known that the out flow of water from Bangladesh is the third highest in the world, after the Amazon and the Congo systems. The Padma, Jamuna and the lower Meghna are the widest rivers, with the latter expanding to around eight kilometers across in the wet season, and even more during the floods.
Some rivers are known by different names in various portions of their course. The Ganges (Ganga), for example, is known as the Padma below the point where it is joined by the Jamuna River, the name given to the lowermost portion of the main channel of the Brahmaputra. The combined stream is then called the Meghna below its confluence with a much smaller tributary of the same name. In the dry season the numerous deltaic distributaries that lace the terrain may be several kilometers wide as they near the Bay of Bengal, whereas at the height of the summer monsoon season they coalesce into an extremely broad expanse of silt-laden water. In much of the delta, therefore, homes must be constructed on earthen platforms or embankments high enough to remain above the level of all but the highest floods. In non-monsoon months the exposed ground is pocked with water-filled borrow pits, or tanks, from which the mud for the embankments was excavated. Throughout the country there are bils, haors and lakes that meet the need of drinking, bathing and irrigating water.