The joint river valley venture between India and Nepal is the Kosi river. The Kosi river is a transboundary river that flows through Nepal and India. It originates in Nepal and enters the Indian state of Bihar. The river is known for its high sediment load and frequent floods, which have led to it being referred to as the "Sorrow of Bihar". The Kosi river is important for both countries as it provides water for irrigation, hydropower generation, and transportation. The joint venture between India and Nepal aims to manage and utilize the resources of the Kosi river for the benefit of both countries.