Quantitative study of impacts of climate change and human activities on runoff in Beiluohe River basin

In the Beiluohe River basin (BRB) runoff has been experiencing a significant reduction induced by climate change and human activities. This paper considers the impacts of climate change and human activities on runoff reduction. An improved empirical method for climate factors and runoff was developed to study the impacts quantitatively. Meanwhile climate elasticity of runoff, based on the Budyko hypothesis, was also adopted to study the impacts. Using runoff change points, series were divided into natural period (1960-1969) and impacted periods (1970-1994, 1995-2010). Results show that the methods used to quantify the contributions obtained different but close conclusions to one another. For 1970-1994, climate was the primary factor impacting runoff; compared with that for 1960-1969, with the contribution reaching around 70.84-83.42%, which was greater than human activities (16.58-29.16%). For 1995-2010, the role of human activities strengthened with the contribution around 62.58-65.07%, greater than climate changes, around 34.93-37.42%.