Runoff characteristics of Manasi River Basin in the past 50 years

Runoff generated in the upper Manasi River Basin is water resource supplied for the middle and lower reaches.Based on the monthly runoff series(1957-2006) of the two hydrological gauging stations,Kensiwate,Hongshanzui and precipitation series at 4 precipitation stations on the upper Manasi River Basin,multiple indexes and a series of methods and wavelet methods were adopted to analyze the inter-annual,annual and periodic variation characteristics of the streamflows in the watershed for the last 50 years.The results show that:(1)Distribution of annual runoff was uneven,and it mainly focused on June and july and August.The inter-annual variations were great,with significant difference between the wet year and dry year;(2) annual runoff changes had obvious stages and the tendency of annual runoff increasing was significant;and(3) annual runoff changes had a main period of about 30 years and 15 years,with an abrupt point happening in 1995.The increasing of precipitation and climate warming were the Key factors influencing the runoff.