Abstract: According to the annual natural runoff time series of Tuohai hydrological station on Khasu River in West Tianshan Mountain from 1958 to 2015, we diagnosed the runoff trend, abrupt changes and cyclic evolution pattern by accumulated anomaly, Mann-Kendall test, power spectrum method and wavelet analysis to provide technical support for the rational use of river water resources, the joint scheduling of cascade reservoirs, and to reveal the runoff evolution of the Ili river. The results are concluded as follows: 1) annual runoff presents a slight rising trend in the recent 58 years; 2) annual runoff increased in periods in 1968-1974 and 1998-2010, but decreased in periods in 1975-1997 and 2011-2014; 3) annual runoff changed with an abrupt increase in 1968 and 2014, and an abrupt decline in 1980; 4) annual runoff changed in three time-scales, namely 3-5 years, 9-12 years and 17-19 years, with the dominant periods of 4, 11 and 19 years.

Key words: runoff trend prediction, accumulated anomaly, Mann-Kendall, power spectrum method, wavelet analysis, Khasu River