Variation Characteristics of Runoff and Quantitative Analysis of Its Affected Factors under Changing Environment in Typical Steppe Basin of Semiarid Region
The climate fluctuation and human activities have significant effects on the changes of surface hydrological processes in the basin, especially for the semiarid steppe basin. This paper chosen the Xilin River basin to analyze the variation characteristics of its runoff series from 1963 to 2015 by using the improved M-K trend test method, the double accumulation curve method, the cumulative anomaly method and the wavelet transform method. The main influencing factors were analyzed by the statistical correlation test and the principal component analysis at hydrological year and seasonal scale. The results show that the runoff decreased significantly at all time scale in the Xilin River basin in the past years; the mutation year of it was in 1998, and the dominant factors affecting runoff were changed after that year; the cycles of the hydrological year and dry season runoff were 6 and 25 years while there were no significant cycle changes in the wet season runoff. The factors like precipitation, evaporation, relative humidity, and human activities have significant impacts on runoff, but the human activities are the dominant ones.