Contributions of climate change and human activities to the runoff change in Heihe River valley

Based on the data of meteorological and hydrological material from 1960 to 2008, this paper used the methods of accumulative anomaly, annual accumulation and rate of change about cumulate slope, and also adopted nonparametric Man-Kendall test. The paper analyzed characteristics and trend of runoff and climate, and calculated the rate of contribution that climate change and human activities caused runoff variation in the upper and middle reaches of Heihe River valley. The results are shown as follows: according to the methods of accumulative anomaly analysis, two inflection points, 1979 and 1984, for the accumulative runoff in the upper and middle reaches of Heihe River Basin, were identified respectively. The time series was divided into upstream (1960-1979, 1980-2008) and middle (1960-1984, 1985-2008) as year of runoff sudden variation, and got linear equation of accumulated runoff, cumulative precipitation and accumulative evapotranspiration with year separately. The upstream climate change was key factors, human activity had less impact. Their contribution rate that increases runoff was 59.71% and 40.29%. Climate varying in the middle influence was little, human activity was main points. The rates that decreased runoff were 25.23% and 74.77% respectively. This research played a role with regards to the water resources in Heihe River Basin development and future utilization.