Abstract: This paper, using daily mean temperature and precipitation from 8 mountainous weather stations over the period 1960-2010 in the arid region of Northwest China, analyzes snowmelt period tendency and its spatial variations and explores the sensitivity of runoff to length, temperature and precipitation of snowmelt period. The results show that mean onset of snowmelt period has a shift of 15.33 days earlier while mean ending date has moved 9.19 days later. Onset of snowmelt period in southern Tianshan Mountains moved 20.01 days earlier while that in northern Qilian Mountains moved only 10.16 days earlier. Mean precipitation and air temperature increases by 47.3 mm and 0.857℃ in the mountainous areas of Northwest China, respectively. The precipitation of snowmelt period with the largest increase was observed in southern Tianshan Mountains, reaching 65 mm, the precipitation and temperature in the northern Kunlun Mountains with the smallest increment increased by 25 mm and 0.617℃, respectively, while the temperature in northern Qilian Mountains rose the highest, an increase of 1.05℃. The annual streamflow is also sensitive to the variations of precipitation and temperature of snowmelt period, because variation of snowmelt period precipitation induce annual streamflow to change by 7.69% while change of snowmelt period temperature results in annual streamflow change by 14.15%.

Key words: snowmelt period, temperature, precipitation, streamflow, the mountainous areas of Northwest China