The glacial contribution to river flow varies greatly, both annually and within and between catchments. The hydrological significance of glacier runoff also depends on other components of the hydrological cycle, such as precipitation, evapo-transpiration, and groundwater flow. In consequence, the impacts of glacier mass loss will be highly variable both locally and worldwide. Some regions will undoubtedly be affected by water shortage, whereas others are unlikely to be significantly affected by glacial melt. Much detailed work remains to be done to adequately predict regional and local hydrological responses to climate change. Flood risks are expected to increase in some regions, including increased frequencies of glacier lake outburst flood (GLOFs) and weather-related flash floods in both the Hindu Kush Himalayas and in the Andes.