Factors affecting runoff change in the upper reaches of the Yellow River

The formation and change of runoff are affected by many factors including both natural and human activities. This paper studies the effect of solar activity, ocean atmospheric interactivity and underlaying surface on runoff change in the upper reaches of the Yellow River using the historical runoff data from the Lanzhou hydrological station. The relationship of relative sunspot number and runoff change is shown to be a positive correlation with the grey correlation and cross spectrum method. The impact of El Nino and La Nina events on high low runoff change is analyzed statistically, and the impact of soil and water conservation on runoff change is also investigated with the double mass curve method.