Tributary of brahmaputra that flows through sikkim?

The Tista River is a tributary of the Brahmaputra River that flows through Sikkim. It originates in the Himalayas in the northern part of Sikkim and flows through the state before entering West Bengal. The Tista River is one of the major rivers in Sikkim and is an important source of water for the state's population. The river is also used for irrigation and hydroelectric power generation.