Future change of hydrological regulation function of glaciers in the cold region basins of western China

As a solid reservoir, glaciers play a significant role in regulating the variation of runoff abundance and dieback in the form of “peak-cutting and valley-filling”. The hydrological regulation function of glaciers is very important in cold regions, especially in the arid regions of Northwest China. The runoff estimation data from 2014 to 2100 were simulated by the VIC-CAS model in the cold region of western China. With perspectives of combinations of trend and fluctuation characteristics, glacier hydrological regulation index (Glacier _R) was constructed based on the runoff variation coefficient method to analyze the stability of glacier runoff in 9 cold region basins of western China. The changes of the hydrological regulation function of glaciers in these basins are analyzed in detail during the historical period (1971–2010) and in the future to the end of the 21st century. The results show that: In the historical period and under the RCP2. 6 and RCP4. 5 scenarios, except for the Yangtze River basin, the decrease time node of glacier runoff in other basins of the Tibetan Plateau is 2020s, and that in the northwest inland basins is 2010s. In historical period and under the global emission scenarios of RCP2. 6 and RCP4. 5 to the end of the 21st century, although the glacier runoff in most of cold region basins in western China showed a decreasing trend, the fluctuation range decreased or had no obvious change, and the stability of glacier runoff increased or had no change. Overall, hydrological regulation function of glaciers is high in the northwest inland river basins, while function is low in the basins of the Qinghai-Tibet Plateau. Under the global emission scenarios of RCP2. 6 and RCP4. 5, to the end of the 21st century, the hydrological regulation function of glaciers showed a weakening trend in all cold region basins of western China, and the weakening was more significant in the inland river basins of Northwest China. Under the global emission scenario of RCP4. 5,the hydrological regulation function of glaciers in the Muzati River decreased by 25. 4%, and all the basins of the Qinghai-Tibet Plateau remained at a low level. With the perspective of decadal variation, the hydrological regulation function of glaciers in the cold region basins of western China was strong during the period of 1970s–2010s, especially in the 1980s and 2000s. Under the global emission scenarios of RCP2. 6 and RCP4. 5, the hydrological function of glaciers showed a weakening trend obviously in the future to the end of 21st century. The earliest time node in the cold region basins is 1970s, and the latest is 2020s.