Abstract:The "Asian Water Tower (AWT)" is an important water source for downstream Asian countries. The cascading impacts on water resources caused by changes of the AWT are closely associated with the water security for billions of people downstream. The changes of the AWT plays a key role in achieving the sustainable development goals in the downstream regions set by the United Nation General Assembly. In the context of global change, the intensity of water resources development and utilization in downstream rivers has continuously increased, and water resource issues have risen in prominence. The changes of the AWT have brought new challenges to water management in the downstream regions. Environmental changes of the AWT have caused extreme events such as the abrupt changes of discharge from the AWT and glacial lake outbursts, resulted in water supply and floods risks in downstream river basins, affected water supply, flood control, and water environment in the downstream regions. By analyzing the impact of changes of the AWT on the downstream systems and the related research gap, suggestions are made to strengthen integrated study of environmental change of the AWT and water security in the downstream, to advance integrated watershed modeling techniques for the whole basins, and to explore the linkages between the upstream alpine area and downstream water systems. There is an urgent need to understand the cascading impacts of the AWT change on downstream water systems, and to cope with the impacts of the AWT change.