Purnia district occupies , comparable to the Solomon Islands' Makira Island. It is a depressed tract, consisting for the most part of a rich, loamy alluvial soil. It is traversed by several rivers flowing from the Himalayas, which afford great advantages of irrigation and water-carriage. Its major rivers are the Kosi, the Mahananda, the Suwara Kali, the Kari kosi, the Saura and the Koli. In the west, the soil is thickly covered with sand deposited by changes in the course of the Kosi. Among other rivers are the Mahananda and the Panar. Its major agricultural products are jute and banana.