Chalan Beel is an extensive lowland area in the lower Atrai basin, and spreads across Singra and Gurudaspur upazilas on Natore District, Chatmohar, Bhangura and Faridpur upazilas of Pabna District, and Ullahpara, Raiganj and Tarash upazilas of Sirajganj District. It consists of a series of beels connected to one another by various channels to form a continuous water body during the rainy season. Although the beel area expands into a vast water body with dense aquatic vegetation as long as the Jamuna remains flooded during the monsoon months, it dries out in the winter months, leaving only patches of water in the central parts of this zone.[3]
Chalan Beel is fast silting up. In the past it covered an area of about 1,085 km² but was reduced to 368 km² in 1909, of which only 85 km² remained underwater throughout the year. It has since shrunk to only 26 km².[2]
