Characteristics of runoff variation and its response to climate change of Qingshuihe River and Alagou River watersheds in southern slopes of the Tianshan Mountains
Runoff in Xinjiang mainly comes from snow melt water and precipitation in the mountain regions. With global warming,glaciers and snow-capped mountains have been shrinking,which directly impact the mountain runoff and surrounding ecosystem. Due to the difference in geographical environment,the response of runoff to climate change is different from place to place in the south slopes of the Tianshan Mountains. Based on hydrological data (1956-2012) of the Qingshuihe River and Alagou River,the trend,mutation,variation period of the runoff and its response to climate change in the study watershed were analyzed using the methods of Mann-Kendall method and crossover wavelet transform. The results are as followed. Seasonal distribution of runoff is not uniform,with summer runoff accounting for more than half of the annual runoff in the Qingshuihe River and Alagou Rive. The annual runoff has been increasing significantly. The hydrological process had a turning point in 1988. After 1988,runoff in the Qingshuihe River has been in abundance state and the runoff in the Alagou River has increased significantly too,especially in 1996,owing to superposition of more precipitation and higher temperature. The annual runoff shows periodic change with various time scales,of which the main period is more than 32-year,and the small periods are 2-year or 8-year. There are some regional differences in response degree of mountain runoff to precipitation and temperature in the Qingshuihe River and Alagou River. The mountain runoff of the Qingshuihe River is more sensitive to precipitation change than that of Alagou River. The annual runoff variation of the Alagou River is controlled by temperature. The Alagou River runoff exhibits sensitivity to temperature higher than that in the Qingshuihe River. Owing to glacial runoff regulation and permafrost degradation, annual runoff process in the Alagou River shows a lag more than that in the Qingshuihe River.