Bhar Basin the very lowland in and around Atrai upazila having an area of about 3,120 sq km. Bhar means 'lowland'. This basinal area sometimes is also known as the Chalan Beel Depression. In scientific literature it is referred to as Lower Atrai Basin. Along the eastern side of the west-central barind tract, the base of this basin is 40 km and its apex nearly 160 km away, where the hurasagar river flows into the jamuna. The basin can be divided into two parts on the basis of its relative height, and the normal depth of inundation. A sheet of water having depth of 0.61 to 3.7m covers the basinal area during the rainy season (June to October). It does not look like a lake, as it is dotted with homesteads on raised mounds, and covered with deepwater rice or reeds and grasses.
The western half of Bhar Basin collects water from chalan beel as part of its drainage. Then it passes through the broad sheet of water, known as Failam, into several other water bodies, and finally flows into the Jamuna through the Hurasagar. Number of north-south streams coming through the Barind Tract are obstructed in this part of the basin and then turned southeast. Due to the rapid changes of courses these rivers and streams deposit much of their silt here and as such rising the level of the basin slowly. This part of the basin gets flooded deeply and often quickly. Near Manda, where the atrai turns southeast, there is an area of very irregular relief, with almost circular deep basins. The soil is mainly heavy clay. The eastern part of the basin has more ridges. But the land usually gets flooded in the rainy season. There is also some influx of water from the ganges when it is flooded. [Tahmina Ahmed]