Haor

A ( হাওর) is a wetland ecosystem in the north eastern part of Bangladesh which physically is a bowl or saucer shaped shallow depression, also known as a backswamp. During monsoon receive surface runoff water from rivers and canals to become vast stretches of turbulent water. In Bangladesh and in the deltaic part of the Indian state of West Bengal, which lie in the floodplain of three great rivers, the Bengali language has several terms to differentiate between lakes, including , , and . All four are types of similar freshwater wetlands. The line of difference between a , a and a is usually very thin. A is usually a depression or topographic low generally produced by erosion or other geographical process. These are marshy in character. Sometimes are remains of a river that has changed its course. Many of the dry up in the winter but during the rains expand into broad and shallow sheets of water, which may be described as fresh water lagoons. are generally smaller than , but there also are large like Chalan Beel in Rajshahi Division, through which the Atrai River passes. It has shrunk over the years but still occupies an area of 26 km2 in dry season. Sometimes small permanent water bodies within the remain after the dry up. These are also called , which occupy the lowest part of the depressions. A or is an oxbow lake, namely moribund beds of Bhairab, Kaliganga, Gorai and Kumar rivers. A simple definition was provided by hydrologist Saila Parveen, " – seasonal wetland, – oxbow lake, and – perennial water body." or are found mostly in the moribund delta as in greater Comilla, Faridpur, Dhaka and Pabna districts. The is predominantly a feature of north-eastern Bangladesh. are seen all over Bangladesh and the neighboring districts of West Bengal. In a country where one third of all area can be termed as wetlands, the basin is an internationally important wetland ecosystem, spread over Sunamganj, Habiganj, Moulvibazar districts and Sylhet Sadar Upazila, as well as Kishoreganj and Netrokona districts outside the core area.