Impact assessment of climate change and human activities on net runoff in the Yellow River Basin from 1951 to 2012

Runoff in the Yellow River Basin (YRB) has changed constantly during the past six decades. This study investigates the features of variations in runoff increment in the YRB and evaluates the impact of climate change and human activities on the mean annual net runoff. Residual analysis based on double mass curves (RA-DMC) was performed to quantitatively assess the separate contributions of climate change and human activities to the changes in net runoff. There was a significant downward trend in annual net runoff for each of the Yellow River sub-basins. For the basin as a whole, net runoff decreased at a rate of 0.721 × 109 m3 yr−1, with the upper, middle, and lower sub-basins separately accounting for 28.4%, 40.5% and 31.1% of the decrease. Human activities were responsible for more than 90% of the change in runoff in each separate sub-basin between 1960 and 2012. For the entire YRB, 91.7% of the change in net runoff from baseline was attributed to human activities. This indicates that human activities have become the dominant factor in net runoff changes in the Yellow River Basin. Among the upper, middle, and lower reaches, the effect of human activities was greatest in the lower reaches.