Chalan Beel is one of the largest inland depressions of marshy character and also one of the richest wetland areas of Bangladesh. It is the largest beel of the country and comprises a series of depressions interconnected by various channels to form more or less one continuous sheet of water in the rainy season when it covers an area of about 368 sq km. The beel extends over four adjacent districts, Rajshahi, Pabna, Sirajganj and Natore.
The major parts of Chalan Beel cover an extensive area of Raiganj upazila of Sirajganj district and Chatmohar upazila of Pabna district. It lies between Singra upazila (natore district) and the north bank of the river Gumani.
Chalan beel was formed when the old brahmaputra diverted its water into the new channel of the jamuna. Chalan beel was probably a backswamp before it was greatly expanded with the inclusion of abandoned courses of the karatoya and the atrai and became a vast lake. The formation of the Chalan beel is historically linked with the demise of the Atrai and the Baral. The Atrai or the Gur was the principal feeder channel of Chalan beel, which used to drain the districts of Dinajpur and northern Rajshahi. The Baral worked as an outlet of the beel and eventually found its way into the Jamuna. It was about 1,088 sq km in area at the time it was formed.
The banks of the beel are covered with dense stands of kash, babla, nol, dhol kolmi, simul, and date palm. Seven species of frogs and one species of toad represent the amphibian fauna. Chalan Beel has a total of 34 species of reptiles, including ten turtles and tortoises, nine lizards and various snake species. There are 27 species of mammals from 12 families.
Chalan Beel has experienced the negative effects of pesticide use in the surrounding farmlands. In 2010, Bangladesh Agricultural University research, found pesticide use has increased sixfold since 1982, and the fish population of Chalan Beel has halved in the same period. A 25 kilometre highway constructed on the Beel has divided into two and caused havoc on the fish breeding by disrupting their movement. Commercial overfishing, grill and drag net and other destructive fishing have harmed the fish population. The Government has taken necessary steps to eliminate these types of problems.
The implementation of initiatives and development plans of Awami League government has created a vibration of life in the neglected Chalan Beel areas. With the implementation of various development programs including education, health, communication, electricity, technology, the ongoing budget is a bright and moving city today.