Ganges is a complex trans-boundary basin which is poorly understood in terms of both the existing quantity and quality and future impact of climate change.The basin is extremely heterogeneous in terms of geography,availability of and access to resources including land,water and energy,development and socio-economic trends.Average annual flow in the Ganges varies from 5.9 kin3 upstream at Tons River to 459 km3 at Farakka barrage closer to Bangladesh.