Why does the Bay of Bengal gain water overall during a year?

The Bay of Bengal experiences a net annual gain of water primarily because the volume of freshwater it receives from rainfall and riverine discharge exceeds the amount of water lost through evaporation.1

The bay receives significant freshwater input from several major river systems, including the Ganges, Brahmaputra, Mahanadi, Godavari, Krishna, and Kaveri. This discharge is particularly high during the fall, which significantly lowers the surface salinity of the bay. Additionally, the region is heavily influenced by the monsoons, which bring substantial precipitation to the area. This combination of heavy seasonal rainfall and the massive discharge from these river systems ensures that the bay maintains a positive water balance throughout the year.234156