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Abstract. Mountain ranges in Asia are important water suppliers, especially if downstream climates are arid, water demands are high and glaciers are abundant. In such basins, the hydrological cycle depends heavily on high-altitude precipitation. Yet direct observations of high-altitude precipitation are lacking and satellite derived products are of insufficient resolution and quality to capture spatial variation and magnitude of mountain precipitation. Here we use glacier mass balances to inversely infer the high-altitude precipitation in the upper Indus basin and show that the amount of precipitation required to sustain the observed mass balances of large glacier systems is far beyond what is observed at valley stations or estimated by gridded precipitation products. An independent validation with observed river flow confirms that the water balance can indeed only be closed when the highaltitude precipitation on average is more than twice as high and in extreme cases up to a factor of 10 higher than previously thought. We conclude that these findings alter the present understanding of high-altitude hydrology and will have an important bearing on climate change impact studies, planning and design of hydropower plants and irrigation reservoirs as well as the regional geopolitical situation in general.

Nepal's quake-driven landslide hazards Large earthquakes can trigger dangerous landslides across a wide geographic region. The 2015 M w 7.8 Gorhka earthquake near Kathmandu, Nepal, was no exception. Kargal et al. used remote observations to compile a massive catalog of triggered debris flows. The satellite-based observations came from a rapid response team assisting the disaster relief effort. Schwanghart et al. show that Kathmandu escaped the historically catastrophic landslides associated with earthquakes in 1100, 1255, and 1344 C.E. near Nepal's second largest city, Pokhara. These two studies underscore the importance of determining slope stability in mountainous, earthquake-prone regions. Science , this issue p. 10.1126/science.aac8353 ; see also p. 147

[1] This study investigated the sensitivity of streamflow to changes in climate and glacier cover for the Bridge River basin, British Columbia, using a semi-distributed conceptual hydrological model coupled with a glacier response model. Mass balance data were used to constrain model parameters. Climate scenarios included a continuation of the current climate and two transient GCM scenarios with greenhouse gas forcing. Modelled glacier mass balance was used to re-scale the glacier every decade using a volume-area scaling relation. Glacier area and summer streamflow declined strongly even under the steadyclimate scenario, with the glacier retreating to a new equilibrium within 100 years. For the warming scenarios, glacier retreat continued with no evidence of reaching a new equilibrium. Uncertainty in parameters governing glacier melt produced uncertainty in future glacier retreat and streamflow response. Where mass balance information is not available to assist with calibration, model-generated future scenarios will be subject to significant uncertainty.

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