Teesta River is lifeline of Sikkim and makes a border between Sikkim and West Bengal before joining the Brahmaputra as a tributary in Bangladesh. The total length of the river is 315 kilometres.It originates at Tso Lhamo Lake in North Sikkim and is formed by the melting of the Tista Khantse glacier.
Just before the Teesta Bridge, which joins Kalimpong with Darjeeling, the river is met by its main tributary, the Rangeet River.
At this point, it changes course southwards flowing into West Bengal. The river hits the plains at Sevoke, at a distance of 22 Km from Siliguri, where it is spanned by the Coronation Bridge which links the north-east states to the rest of India. The river then courses its way to Jalpaiguri and then to Rangpur District of Bangladesh, before finally merging with the mighty Brahmaputra at Fulchori.
In 1983, an ad-hoc water sharing agreement was reached between India and Bangladesh, whereby both countries were allocated 39% and 36% of the water flow respectively.