Changes of Precipitation‐Runoff Relationship Induced by Climate Variation in a Large Glaciated Basin of the Tibetan Plateau

Abstract

AbstractClimate warming on the cryosphere could change catchment precipitation‐runoff relation by additional water from glacier melting and more energy absorbed at the ground surface. These changes further alter the physical properties of the catchment. The combined effects of these changes on runoff are analyzed from upstream to downstream of the Yarlung‐Zangpo River (YR) basin in southeastern Tibetan Plateau using statistical methods and a modified Budyko equation with consideration of glacier melting. Major results show that in the study period of 1980–2015 there was a jump in the mean annual temperature and precipitation around 1997. Since 1997, accelerated glacier melt and the thaw of permafrost have contributed to a nearly 80.9% increase in surface runoff in the upstream region of the YR basin. Meanwhile, the increase of runoff in the same period in downstream areas of the basin with warm and wet climates is smaller and has been mostly from an increase in annual precipitation. Part of that increase is offset by changes in catchment properties following the warming, such as the increase in vegetation coverage. Results of runoff responses to climate change and catchment properties across different sub‐basins in the YR basin and between the two time periods separated in 1997 suggest that continued warming would reduce the buffering effect of glacial and permafrost on runoff in upstream areas of the basin, shortening the runoff response time to precipitation and increasing flood and drought vulnerability of the YR basin.